HomeMy WebLinkAboutRDA RES 153RESOLUTION NO. 153
A RESOLUTION OF THE PALM DESERT REDEVELOPMENT
AGENCY APPROVING PAYMENT BY THE AGENCY OF ALL
OR PART OF THE COST OF CERTAIN PUBLIC IMPROVEMENTS.
The Palm Desert Redevelopment Agency hereby FINDS,
DETERMINES, RESOLVES and ORDERS as follows:
SECTION 1. The Palm Desert Redevelopment Agency
proposes to pay for all or part of the cost of certain flood
control improvements to be installed, constructed, owned,
operated and maintained by the Coachella Valley Water District.
Such flood control improvements are to be installed and con-
structed pursuant to that certain plan known as the Bechtel
Plan 1-A which is a plan contained within that certain study
entitled "Flood Control Works for the City of Palm Desert,
Rancho Mirage and Indian Wells, Coachella Valley Water District,
October, 1978" attached hereto as Exhibit A and by this reference
incorporated herein.
SECTION 2. The study attached hereto as Exhibit A,
and that certain study entitled ''Master Drainage Plan for the
City of Palm Desert," attached hereto as Exhibit B and by this
reference incorporated herein, and that certain study entitled
"Whitewater River Basin Study" by the United States Army Corps
Jf Engineers, attached hereto as Exhibit C and by this reference
incorporated herein, and that certain study entitled "Flood
Insurance Study, City of Indian Wells," attached hereto as
Exhibit E and by this reference incorporated herein, describe
in detail the hazards to Project Area No. 1, As Amended, from
flooding and the protection which will be afforded to the Project
Area by the installation and construction of flood control improve-
ments pursuant to such Bechtel Plan 1-A. Based upon the infor-
mation and materials contained in the studies attached hereto as
Exhibits A through E, the Agency hereby finds and determines that
the installation and construction of flood control improvements
pursuant thereto are of benefit to such Project Area and to the
immediate neighborhood in which such Project Area is located.
SECTION 3. That certain study entitled "Preliminary
Investigation of Assessment Proceedings for Flood Hazard Correction
for the City of Palm Desert," attached hereto as Exhibit F and by
this reference incorporated herein, describes the unavailability
to the City of Palm Desert of traditional methods of financing the
subject flood control improvements, such as general obligation
bonds and special assessment bonds. Based upon the study attached
hereto as Exhibit F and the cost of installation and construction
of such flood control works as set forth in various engineers
estimates and in the bids for the project received from contractors
by the Coachella Valley Water District, and based upon the budget
of the City, the Agency hereby finds and determines that other than
payment by the Agency no other reasonable means of financing the
cost of such installation and construction is available to the City.
RESOLUTION NO. 153
SECTION 4. The Agency hereby approves payment by
the Agency for all or part of the value of the land for and
the cost of installation and construction of flood control
improvements as set forth in such Bechtel Plan 1-A, and all
buildings, facilities, structures or other improvements
incidental thereto.
PASSED, APPROVED and ADOPTED by the Palm Desert
Redevelopment Agency of the City of Palm Desert, California,
on this 12th day of August , 1982 by the following
vote to wit:
AYES:
NOES:
ABSENT:
ABSTAIN:
ATTEST:
Newbrander, Puluqi, Snyder & Wilson
None
McPherson
None
SHEILA GI 'AN, CITLERK
CITY OF PALM •ESERT, G FORNIA
OCTOBER 1978 FINAL
(Supplement to August 1978 Draft)
��L
EHVIROHMEN
IMPACT REPORI
Control Works for e „Indian wells
Flood Rancho Mirag
Palm Desert - ,�,�.
County Water teC DistrictCoachella Valley
J. B.
Gilbert & Associates
Berkeley
TABLE OF CONTENTS
CHAPTER I
INTRODUCTION
Authorization and Scope I-1
Organization of the Report I-1
CHAPTER II
SUMMARY OF RECOMMENDED PROJECT
Description II-1
CHAPTER III
RESPONSE TO COMMENTS III-1
Project Area Hydrology III-1
Flooding in Indio III-1
Level of Protection III-2
Estimation of Peak Discharge III-2
Flood Plain III-3
Delineation 111-3
Management 111-3
Demography III-4
Land -Use Data 111-4
Population and Population Characteristics Data 'III-4
Debris Basins 1II-5
Need for Debris Basins III-5
Access to Deep Canyon Desert Research Center III-6
Natural. Habitat 111-6
Groundwater Recharge I11-6
Aesthetics 111-7
Construction Scheduling 111-7
Maintenance Procedures and Costs 111-7
Flood Control Channels 111-8
Capacity 111-8
Source of Material for Cook Street Channel III-8
Impacts of Sub -Alternatives III-3
Lining Magnesia Spring Channel III-3
Selection of the Recommended Project III-9
Status of the Report III-9
Benefits and Costs III-9
APPENDIX A
WRITTEN COMMENTS TO THE DRAFT ENVIRONMENTAL IMPACT REPORT
iii
). B. Gilbert 6, Associates
CHAPTER I
INTRODUCTION
AUTHORIZATION AND SCOPE
On 23 January 1978, the Coachella Valley County Water District
(CVCWD) authorized J. B. Gilbert & Associates to prepare an
environmental impact report on flood control facilities proposed
to provide additional protection to the cities of Palm Desert,
Rancho Mirage, and Indian Wells. The alternatives under consid-
eration were developed by Bechtel Incorporated under contract to
the CVCWD. Information related to the engineering studies for
the proposed alternatives is contained in the August 1977 report
by Bechtel Incorporated entitled, Engineering Report on
Preliminary Design and Cost Estimate for Flood Control Works
for Palm Desert -Rancho Mirage -Indian Wells. This report is
incorporated by reference into this document.
The Draft Environmental Impact Report (EIR) was prepared to
assess the potential effects of the proposed flood control
projects on the physical and socio-economic environment pursuant
to the California Environmental Quality Act of 1970, as amended,
and State EIR Guidelines.
This Final Environmental Impact Report was prepared in response
to comments on the Draft EIR submitted in writing and presented
at the public hearing held on 17 October 1978 in Coachella,
California.
ORGANIZATION OF THE REPORT
This report consists of three chapters and an Appendix. Chapter
II contains a summary of the recommended flood control project
and mitigation measures proposed in the Draft EIR. Chapter III
presents the response to all comments received. The comments are
organized by topic and referenced to the agency making the
comment.
Copies of all written comments received are included in Appendix
A.
). B. Gilbert 6, Associates
CHAPTER II
SUMMARY OF RECOMMENDED PROJECT
DESCRIPTION
The 1977 Bechtel Report for Palm Desert, Rancho Mirage, and
Indian Wells described 15 alternative flood control projects to
provide protection against the Standard Project Flood. These
alternatives were evaluated in the 1978 Draft EIR. In response
to local concerns, the CVCWD prepared, but has not executed, a
Memorandum of Understanding with the cities of Palm. Desert and
Indian Wells in 1978. It was proposed in this memorandum that
Alternative IA modified would be the recommended project.
The main features of the channels and debris basins which comprise
Alternative IA are shown in Table II-1. Additional detail is
available in the Bechtel Report and Draft EIR. Alternative IA
modified would be the same as Alternative IA except that the
Deep Canyon Channel would be grass lined instead of concrete
lined.
Mitigation measures were developed in the Draft EIR to mitigate
identified impacts. They are reproduced in Table II-2 for easy
reference. As can be seen from the comments in Table II-2,
additional modifications to the recommended project are under
consideration by the CVCWD.
). B. Gi!bart Associetas
TABLE II-2
SUMMARY OF MITIGATION MEASURES PROPOSED IN DRAFT EIR
Proposed Mitigation Measure
1. Schedule major construction activities to avoid
prevalent periods of strong winds.
2. Water construction sites to control dust.
3. Revegetate debris basins to control dust.
4. Eliminate debris basins proposed in the Magnesia
Spring Canyon area.
5. Prohibit construction in vicinity of Magnesia
Spring Canyon, Dead Indian and Carrizo creeks,
and Deep Canyon during summer months to prevent
disturbance to Bighorn sheep.
6. Relocate Deep Canyon debris basins to allow minor
drainage along eastern edge of alluvial fan to
continue in its present watercourse.
7. If Deep Canyon debris basins are not relocated,
retain the Palo Verde habitat along eastern edge
of alluvial fan.
B. Implement a program to establish or enhance
other wildlife habitats to compensate for loss of
habitat in debris basins and along channels.
9. Implement a program to record cultural resources
in Deep Canyon prior to construction.
10. Avoid disturbance to archaeological or historic
sites adjacent to proposed facilities by marking
sites and excluding construction equipment and
personnel in these areas.
11. Consult a qualified archaeologist if additional
archaeological or historic sites are uncovered
during construction.
12. Modify Alternative IA so that the Deep Canyon
Channel would be grass -lined.
13. Modify alternatives which require a new channel
along Cook Street, so that flood waters are
conveyed beneath the existing street.
Impact
Responsible
Agency.
Air Quality CVCWD
Air Quality CVCWD
Air Quality CVCWD
Biological CVCWD
Resources
Biological CVCWD, DFG
Resources
Biological CVCWD, BLM,
Resources NLWRS
Land Use,
Access
Biological CVCWD,
Resources NLWRS
Biological CVCWD, DFG
Resources
Cultural CVCWD, SOHP
Resources
Cultural CVCWD, SOHP
Resources
Cultural CVCWD, SOHP
Resources
Land Use CVCWD
Land Use
II-3
CVCWD,
Cities of
Palm Desert
and Indian
Wells,
County
Comments
Periods of strong winds usually
occur during winter and spring;
construction in summer months
should be avoided in some
areas (see 45).
Under consideration by the
CVCWD; it would require that
the downstream channels be
widened to achieve protection
from the Standard Project Flood.
Under consideration by the
CVCWD; in order to maintain
protection from the Standard
Project Flood, additional
acreage in the vicinity of the
proposed site may be required
for the basins.
Include maps, photography, and
artifacts collection.
Modified versions of Alterna-
tive IA are presently under
consideration by the CVCWD.
Several plans have been con-
sidered; cost estimates differ
depending on the required
channel capacity. Implementing
any of these options would sub-
stantially increase total
project cost.
J. B. Gilbert ex Associates -
CHAPTER III
RESPONSE TO COMMENTS
PROJECT AREA HYDROLOGY
Flooding in Indio
The City of Indio was concerned that flood control improvements
in the project area would aggravate existing flooding problems in
Indio. Shown in Table III-1 are historical peak discharges in
the Whitewater River at Indio and estimated peak discharges from
the 100-year storm and Standard Project Flood. The peak discharges
at Indio have generally been caused by winter storms. The most
critical storm in the project area, however, is the summer
thunderstorm. These thunderstorms cover a relatively small area
and produce high -intensity precipitation of short duration.
TABLE III-1
PEAK DISCHARGES AT INDIO
Peak Discharge
Date cubic feet/second
2 March 1938
22 November 1965
25 January 1969
February 1927
January 1916
6 December 1966
Estimated Storm Flows
100-year Storm
Standard Project Flood
29,000
14,100
11,400
11,500
10,000
5,000
43,000
86,000
Source: "Study of Benefit Assessments Resulting
from Whitewater and Cabazon Dams",
Philip Abrams Consulting Engineers,
Palm Springs, 1975
). B. Gilbert & Associates —
high permeability. The location of the proposed debris basins is
in one such area. The permeability of urbanized areas and the
mountainous areas have a much lower permeability. The precipita-
tion loss rate used by Bechtel to estimate storm runoff varies
from 0.2 to 1.0 inch per hour and depends not only on theoretical
permeability but also upon topography, land use, and type of
storms. It is a parameter of a storm runoff model that used
values based on model verification studies conducted by the
U. S. Army Corps of Engineers on other portions of theyWhitewater
River Basin.
FLOOD PLAIN
Delineation
The City of Palm Desert requested that the Standard Project Flood -
plain (Figure II-7 in Draft EIR) be made to correspond to the
U. S. Housing and Urban Development flood insurance study. This
latter study developed maps that delineated the area that would
be flooded by a 100-year storm if no flood control improvements
were made. The Standard Project Flood used by Bechtel corresponds
to a larger storm expected to occur only once about every 300
years. Because the Standard Project Flood would have a larger
flood volume, and a higher peak discharge rate, it would probably
flood a larger area if no improvements were made. Hence, the two
referenced floodplains are not comparable.
U. C. Riverside was concerned that it appeared that the Deep
Canyon Debris Basins would cause floodwaters to back up onto
University -owned land in Section 9, T6S, R6E. These debris
basins will be designed not to cause floodwaters to back up
onto University -owned property.
Management
The City of Palm Desert commented that the selection of the No
Project Alternative would impact existing floodplain management.
In this case the cities in the project area could elect to
participate in the federal Flood Insurance Program. All new
development proposed in the flood -prone area would then have to
be regulated and new development would have to be flood proofed.
If flood control projects proposed in the Bechtel Report were
constructed, flood insurance and regulation of development in the
floodplain would not be necessary because floodwaters would be
confined to designated basins and channels.
III-3
). B. Gilbert 6 Associates -
Item
TABLE XI-2
POPULATION CHARACTERISTICS
City of
a Palm Desert
City of b City of b
Rancho Mirage Indian Wells
Median Age 37 50 54
Persons over 65 (percent) 19.7 22 18
Persons under 18 (percent) 20.0 20 16
Persons retired or not in
labor force (percent 54.5 45 46
bCity of Palm Desert, 1978.
Coachella Valley Association of Governements, 1976.
DEBRIS BASINS
Need for Debris Basins
U. C. Riverside questioned the need for debris basins, noting that
the U. S. Army Corps of Engineers' project, if constructed as
preliminarily planned, would not involve debris basins and
furthermore, that channel velocities of 30 feet per second should
be adequate to transport sediment out of the proposed area. The
proposed Bechtel projects include debris basins primarily to
reduce overall costs. Without the debris basins the channel
capacities would have to be increased. The channel velocity
design criteria of 30 feet per second will only be reached in
certain channels during the peak runoff periods. Most of the
time, in most of the channels, the velocities will be lower.
Without the debris basins, sediment would be deposited in the
channel reaches having lower velocities, which could cause flood-
waters to back up and overtop the upstream dikes.
The State Department of Conservation asked whether removal of
sediment could increase erosive forces in the channels. All
proposed channels will be lined to protect against any increase
III-5
J. B. Gilbert U Associates —
Aesthetics
U. C. Riverside was concerned about the aesthetic impact of the
proposed flood control project. The major impact will be caused
by the Living Desert Debris Basin. This is considered to be an
avoidable adverse impact which cannot be mitigated.
Construction Scheduling
The State Department of Fish and Game requested that construction
of the upper canyon portions of the flood control project not be
undertaken in the summer months. This is a recommended mitigation
measure in the Draft EIR. There are other scheduling concerns
related to minimizing air quality and traffic impacts that will
have to also be addressed when the project is constructed.
Maintenance Procedures and Costs
The State Department of Conservation and U. C. Riverside requested
information on debris basin maintenance and disposal of removed
debris. Debris removal will occur on an infrequent and unpre-
dictable basis following major floods. It is believed that
average annual debris removal from all proposed debris basins
and channels will be in the range of 30,000 to 60,000 cubic yards.
It should be noted that no debris may be deposited during years
of no or low runoff. The debris would be disposed as fill
material in the project area and on CVCWD property on the west
side of the Coachella Valley.
The energy consumption during debris removal is estimated to be
in the range of 15,000 to 30,000 gallons of fuel per year. The
water used for dust control during debris removal is estimated to
be in the range of 1 to 4 acre-feet of water per year. The cost
of debris removal was estimated by Bechtel in their 1977 project
report to be $60,000 per year for the entire system of debris
basins and channels. These costs were included in their annual
cost analysis of the proposed project.
). B. Gilbart Associitas
If these debris basins are to be eliminated, as is presently being
considered by the CVCWD, the channels may have to be widened and
additional energy dissipation structures provided. The detailed
design should be reviewed with the Department of Fish and Game to
minimize wildlife impacts. Adjusting the side slope and adding
steps into the concrete side walls are examples of design modifi-
cations which could be provided.
SELECTION OF THE RECOMMENDED PROJECT
Status of the Report
The City of Palm Desert requested an analysis of the proposed
Memorandum of Understanding between the CVCWD and the cities of
Palm Desert and Indian Wells. This memorandum indicates that a
modified version of Alternative IA is the preferred alternative.
As is discussed under the sub -alternatives in the Draft EIR
(page XII-10) and in this report, this modification of the
proposed project would mitigate the land -use impacts associated
with concrete -lined channels and therefore improve overall
environmental impacts.
Benefits and Costs
The City of Palm Desert requested that benefits and costs of the
proposed project be compared in a quantitative manner. Regarding
the costs, the proposed project has not yet been fully defined
and therefore there is no single cost estimate --only a range of
costs are available at this time. The calculation of benefits
is a more subjective matter. It too cannot be finalized until
the project is selected. From information presented on page
XII-12 of the Draft EIR, for a storm of less magnitude than the
Standard Project Flood, it appears that benefits will be well in
excess of project costs. It would be inappropriate at this time,
however, to calculate a benefit cost ratio based upon preliminary
cost and benefit information.
III-9
). B. Gilbert & Associktas
MASTER PLAN OF DRAINAGE
for the
CITY OF PALM DESERT. CALIFORNIA
June. 1976
with
Amendments of January and November. 1977
I HAROLD HOUSLEY
Consulting Engineers
on association with
WILIDAN ASSOCIATES
Engineers. Architects & PIannPr,
r
CHAPTER 1 INTRODUCTION
TABLE OF CONTENTS
1.1 Authorization and Scope
1.2 Description of Study Area
1.3 History of Drainage
1.4 Conclusions and Recommendations
.HAPTER 2 STUDY APPROACH
CHAPTER 3
2.1 Existing Drainage Patterns and Facilities
2.2 Flood Frequenci,
2.3 Methodology
TECHNICAL STUDY
3.1 Hydrologic Studies
3 2 Coefficient of Runoff
3.3 Rainfall Intensity
...
3.4 Coverage of Impervious Material
3.5 Time of Concentration
3.6 Hydraulic Studies
3.7 Retarding Basins .....
CHAPTER 4 PROPOSED MASTER PLAN SYSTEM
4.1 Identification of System Elements
4.2 Drainage Area Designations
4,3 Description of the Proposed Dralryge System
4,4 Alternative Systems . . .
4 5 Priority Schedule
4.6 Surface Improvements
....
Page
1
1
1
5
7
7
7
8
9
10
10
10
12
12
13
13
14
17
17
17
19
19
25
25
CHAPTER 5 ESTIMATED COST OF MASTER PLAN iMr1..EMENTATION 28
5.1 Basis of Estimates 28
5.2 Estimated Projott Costs 28
5.3 Project Costs of Conduit Systems for Vafious Storm Frequencies 30
5.4 Cost of Alternative Systems 31
5.5 Required Surface Improvements 32
CHAPTER 6 FUNDING METHODS
6.1 General Fund
6.2 Drainage Fees
6.3 Federal Revenue Sharing
6.4 Federal Housing and Community Developrnk4-0 Act of tr74
6.5 'Redevelopment Agency Funds
6.6 Assessment Districts
6.7 Highway Impri-yompet Projects
6.0 Sfrrvir, of Coverage Charges
6 9 Combinations of Funding Mile,rids
• .4
•
3:3
33
33
34
34
35
35
30
Page
APPENDIX A Runoff Coefficients for Soil Groups 39
APPENDIX B
Floods of September 1976
Tropical Storm Kathleen
Storm of September 23
Effect of the Master Plan System
TABLES 3.1 Comparison of Runoff Coefficients ='
1 l' len 11966) vs. Hou SlevtWittdan (1976) 11
3-2 Impervious Coverage nn a Tvpar ral 10,000 Square Foot
Residential Lot . . . . . . . . . . . . , . . 12,
4.1 Facility Identification Codes 17
4-2 Drainage. Master Plan Descript!, 21 24
5-1 Estimated Project Cost of Ref v, mended Drainage Plan . . 30 k
5-2 Estimated B,a',an Corts for Pronosed Master Plan Conduit System 30
5-3 Comparison of Project Costs cf Conduit System. for Various
Storm Frequencies 31
5-4 Summary 'of Costs frx Alternative Si sterns 32
55 Estimated Cost of Required Surface Improvements 32 i
6-1 Potentially Collectible Drainage Fees . . . . 34
6-2 Possible Funding Sources for Peoctlrc-<i Dra.n,ane Facilities 37
FIGURES . 1 Vicinity Map . . 2
2 Aerial Photograph 3 •
3 Flood Damage Along the Wt +tevv'ater River , . . . . . 6
4 Retarding Basin Concept 16
5 Conveyance Facilities 18
6 Facilities Plan 20
7 Surface Improvements 27
8 Construction Cost Indices 29
A-1 Runoff Coefficient Curves 40
A-2 Hydrologic Sods Types 41
8-1 Aerial Photograph 43
B-2 - B10 Photographs . 43.47
C-1 Rainfall Intensity/Duration Curves 48
CHAPTER 1
INTRODUCTION
1.1 Autharitation and Scope
'In January, 1976, the City of Palm Desert authorized the assoaate.d firms of I. Harold Houstey,
Consulting Engineers and Willdan Associates. Engineers. Architects and Planners to develop a master plan
• of drainage for the City. The purpose' of the authorization was to provide a comprehensive long-range
plan for the development of drainage facilities within the City.
The „ethorization limited the scope of the study to the existing City boundaries and to provision for
primary drainage facilities. Several previous studies have been conducted in the area. The scope of the
• current iniestigation was intended to opr mite the value of previous studies through expansion and
modification of the data to develop a comprehensive drainage plan consistent with the City's adopted
general plan and with current Pngcneering practrro.
12 Description of the Study Aran
• The City of Palm Desert is located at the foot of the Santa Rosa Mountains along the southwesterly
side of the Coachella Valley midway between Palm Springs and Indio. Figure 1 shows the City in its
regional context. The City is characterized by resort and retirement activities although date groves still
exist in part ui the Crty.
While the City is orimarity a residential community, an active commercial core exists along State
Highway 111. Other notable Land uses within the present City boundaries include the College of the
Desert and the Living Desert Reserve. The City's General Plan c..'lis for continued development to move
in a northerly and easterly direction with predominant land uses in mtdiurn, low, and very low density
residential development and with some industrial development generally paralleling interstate Highway 10.
The City has developed on the alluvial fan deposited by drainage from Dead Indian Creek and Deep
• Canyon watersheds. Ground surface elevations within the City vary from about 150 feet at the Cook
Street crossing of the Whitewater River Storrnwatcr Channel to 1,040 1e't on the canyon wall along the
westerly boundary of the City. Within the study area itself maximum elevation is approximately 720
feet near the intersection of Dead Indian Creek diversion dil-A and State N.yhway 74. The physical
features of the study area are pictured in the aerial photograrh preeeerei rrgure 2.
The City of Palm Desert is located in an arid inland desist o g,on of the Coachella Valley in Southern
California. The typical annual precipitation for the area is on the order of three inches per year. The
greatest 24-hour and 1-hour rainfalt recorded at established rainfall record stations in the general vicinity
is 2,90 inches end 1.24 inches respectively. Virtually no precipitation ,s experienced during the non -
winter season, except for thunderstorms which generally occur during the period between August and
November .
• Thunderstorms are typically of short duration, however, the r intensity can be vary high. Consequently,
the potential for extensive runoff rates and 'load damage is euite.acute for this type of storm. Thornier•
Cams do, in :act, pose a very 9errous potential for local !loin' dam:x .
While the area within the study limits is mach smatter than that in the rnotintain watersheds to the
i South, the storms on the valley floor are capable of producing substantial quantities of surface runoff.
The 'effect of this runoff is magnified by a .ombination of natural fe,e,-r, e'ter aIion by developer'r.t
era the absence of en adequate drainage system. The relatively steep r! .>pt 5 enertherty of Highway f 1 1,
Nma
41"
•
.4,1 • •-..4
1,4
• 44 •
4 ../es •
4,‘ • • '
1.;
tot ^f-o' `"t• -4:
7 0'
....,
...'' r....j,i....,„t -.4.
' . reoot,:v• 104- ‘1.14 ..- - ' - i- ...
, • i
4, 4,ept, ., ..• r''' • '' ...t 4 it '•‘4,
)4.• .... ••
0, "-- „, • ,
r .
...•.- - e N ..,--.."--.... ; : 40 ''‘,.; .1 1•
OP . :
-
dr
4.1.0
44 "
4 •
'We
+V"
O.* fir
- * ,
tt
'*••• • —
.017,"4tV • t;
• V* •
om,••
;- .-r
;0* '
a 4* 4"
` ,` 04-*-
•
1'
•
41000610100.4000,44
r '4 • "
• 40, "4
' • ;,4 '‘.4
L. „ , •
0 rl
,, •
•
-tt, • - ."‘
,•
ic•
•
ori,r4
7,4[0; rr
40. ? • •
•
;1
I
•
r;••,c-r-
•
9if.
the restrictions created by the State highway, and the relatively flat area between the highway and the
Whitewater Rive Stormwater Channel combine to cause moderate to serious flooding and erosion
problems. Presently, surface runoff is carried in sheet overflow or in the existing street sections, Since
the majority of streets have little or no crc xn and are without curb and gutter, their water carrying
capacity is severely limited. Moreover, most of the east west streets have been constructed without
consistent grade. As a result, the water carrying rapacity of the street is easily 'exceeded, and the storm
water must then flow across the adjoining downstream property,
Varying degrees of flooding problems have been observed thriiuihout the City. Among the typical
drainage prublemc ire
(11 Erosion
121 Overland f;nw
13) Utility disruption
.11) Restrictionat State Highway 111
15) Poodir`g problems; in the flatter tier, en norther', Lif St.sh Hirt` ^.iy 111
Sail err lion from storm flow has been a major s'aurce of damage during flood peruxjs 1 s n er th su.ith
streets southerly of State Highway 111 have relatively sleep grades and sterr w iter roaches high vicetcx•ihes.
j ric'e most of the streets are w thous curb and gutter, it* water is i)hannole'd bivi'g the earaly e•rixdihle
shoulders of the road, creating ditche,, often ,. •al tr»•t in depth. Th+ enr, >n larnaae e pr,,p'.rty frc,nLaevs
and undermines driveway apprii,r-hes Eiod'd e ils are then tarried d `,ti'n•.1rtarr aria ter-",',rtn,1 ,o the
Clatter areas' as The veto•'rty of the therm flow dt•rreiw=.
...Some properties fronting on., . ist-west streets air suhte4:t to i'rosioii `,i•m v.aic r s)r,ti•,r,,g between buildings..
The water is diverted across private nroperty when the limited cane: ,in cat .ici'ty of the unrurt''d Streets
is exceeded. Properties Itx;atted along ihe'nartt only side of "T' or •.1_" nttervcnons .are particularly
susceptible to damage of this type.
Sorne damaoe to utility lines'' as Oi_Ctirr,d teem .erosion or trench settlement attributable to storm runoff.
Severe erosion can expose and iindr,rne e. in j..rgro,r d +ailiLrs re,ulhng in internrpt,an ,,f „n,
The construction of Highway 111 effei lively f ;rmr ei a dike runr•iq east vest arras,, the City. A number
of culverts intended to carry storm flow aerie:, the• i ighway have b.e n provided. The culverts, however,
have insufficient capacity to carry the storm flow horn the entire drainage area ,.riurherli of the highway.
As a result, portions of the highway and adt.ac'rr,t pi,,pertie,, to the south ;,re ublrrrt to flooding during
severe storms. During major storms the highway culit•rts discharge large quantities nt water ;it high
velocities intensifying flood problems for downstream properties. Ftoudinq ni:e,nt e e:;erat ! •cate-,ne.
along Portola Avenue. The most significant of ta'esr n in the area of 41th Avenue. 1 the , ; a point of
runoff concentration from much of the City tying `.ri'stf riy of Porti•la Avenue, and ••,iit'a,•rly "f 449i
Avenue. The flooding problem is intensified by the limited carrying capacity of the Ntre,•is tr swer+i
Highway t 11 and the Whitewater River Storrs at,er Channel. Water also ponds at 44th .ind Mt,niori:v
Avenues and north of 44th Avenue on San Pablo Avenue. Properties north of 44th Av, we, fr+irn Sir,
Pasc.tal Avenue to Portola Avenue, are subject to inundation. Se,'. ee hoe„s in th ; need hay, i iti
as much as one foci above the floor level,
The major difference in the flooding problem north of Highway 111 compared to that south nt tivi `,fate
Highway, is that the flatter :lopes combine' to. reduce the extent of erosion but incrr,a.x, the ef.pth t,f
water. Generally, the amount of damage extue,ieenrerf northerly of Highway 111 i,, yir•.tta•r thtai t.a
south. Examples of increased ponding •i•Jude properties a'nnq the north side of C;.it;al.,,.i U'},. b„twe4,n
—4—
San Pablo Avenue and Portola Avenue. Property near the intr,r•ection of Roy& Palm Drive and San
Mateo Avenue and near El Cortez Avenue and Cabrillo Aven;,e may also experience flooding. Finished
floor elevations of homes in these areas are tow compared to the street ftuwline and water has entered
the houses doting severe storrns.
Local drainage problems occur in almost all part of the City. Many of there occur at locations where
drainage is transferred from the steeper north -South streets to the virtually -level taast•weSt streets. Often
this occurs at a "T" intersection (e.g., Joshua Tree Street and Burroweed Lane) where the east -west
streets have instifficient capacity to accept transfer of the e. et<r As a result. ponding occurs until the
runoff hatpins to overflow on the downstream property Without curb and gutter, or other means of
containing the storm flow, runoff (even from small storm••) cannot be contained in the streets.
Implementation of a grading ordinance provision never -inn ea-, and buildrnq parts to dram to the
street would serve to further aleviate the problem
1.3 History of Drainage
Hrstorecatly, two generally distinct flood control t�rohiemr, har-e existed in the Cuauie:1,e ..,Ili . ''r. 'ate
involves runoff from storms occurring ,n ariiacent mo nL, • ranee.,- Stormwater trtrm watersheds in the
San Bernardino, San Jacinto, Santa Rosa, and Lrttre S•+n Et, rri,ardrrt r rig cram ranee!, is carried ntr) the .
valley via the Whitewvater River and it, tnbit•anr^, Heavy r.rr.tall n the, mountainous areas combined with
with spring urowmelt, has contributed to maim- fiends in Pile'', 1'1.'7, 1938, arid again in the late 1960's.
The phutugranh , rr f rq irr' 3 r'r.. to r', •.•in . if es: i1,..,aeeLim n•s+ine rj from the tat, st of these major
floods
A substae:r:.a! amount id damage uc tarred in the Palm Dcst'1 area as a result of the 1927 stbrm.''),a
Flood waters resulting trier major storm activity in the f . Carryon watershed of the Santa Rosa
Mountains washed out potions of highway in tree, Palm De...ert ,erica, Channel erosion from that storm
was estimated betwee' 8 and 10 feet in depth The Deep Canyon Stormwater Channel wn i cunstrur o'<1
to reduce the likelihood c,' reoreurrence of this type of it ir•'age.
The second type of drainage problem is that resulting from storm, occurring primarily over the valley
floor. While runoff quantities from these storms are rrlat',cey smart in rompartscm with those generated
in the watersheds of the adjacent inoiintirri range's, they crit of vepbrr:ince rn planning a drarnani system
because of their intensity The, types of t+ar'di•rtore, at t• i1, t,avr,rd substantial damage in the Palm
Desert area in 1948 and again in 1951.
The first organized effort to control tlood.ng in the Coat r etta Valley was by the Indio Levee District.
In 1915, the Coachella Valley Stormwater District was 0r1anizeti absorbing the Indio Levee District and
the Coachella Storm -water District. Three years later, N1e• C ear h-114 Valley County Water Deduct
(CVCWD) was formed as a vehicle to conserve kcal water resouut'e, and tb contract for supplemental
water from the Colorado River. In some respects, the arh•:rtres of the County Water District and the
Stormwater District were duplicated and in conflict. In 101(7, the two districts were merged leewmq
the Coachella Valley County Water District as the sorvrvfng agency and placing ur it the rr'p r srbr!rty
for regional flood control in the southern and eeotral portions of the Coachella Vallee.
As the Palm Desert area began to develop, the CVCWD in conjuncton with developers con/rt.etett a
nurnbx of facilities to protect the area from runoff from adjacent mountain canyons. •In 1940, the
CVCWD completed the Deep Canyon Stormwater Channel. This channel, along with a series of dikes
and a spreading area, were constructed to divert mator storm flow around Palm Desert and dr t harge it
to the Whitcwater Raver near Point Happy about a1't mike. ea;t of the present City limits (see Frg,re 2)
The Pam Valley Stormwater Channel was built along the western fade of what is now the City of Palm
Drlert, late►, a dike was constructed to divert storm waters from Dead Indian Canyon around Palen
Dreert.
'Yhitetwater River a in, CVCWD, April, 1967, p. 21.
*Report by Coachella Valley Stormwater District to Rrverslde County Board of Supervi<.or s, urrdat,d-
*Report to Board of Trustees, Coachella Valley Stormwater district, March 28, 1927, ley George N Acin,ns.
—6—
ft
n
PHOTOOnAP►4A COUATEBY Of
COACHlLLA VALLEY COUNTY WAtER 0+147Alct
PALM
0UU
MASTPLAN OF OPAINAGIII
CITY OF PALM 0128121:1T
FLOOD DAMAGE
ALONG THE
WHITEWATER RIVER • •
I. HAROLO HOUSLE Y
CONSULTING ENGNEPS
IN ASSOCIATION WITH
WILLOAN ASSOCIATES
th
Together. the Whitewater River, Palm Valley and Deep Canyon Stormwater Channels, and their
appurtenant facilities serve as the City's primary protection against Major flood damage. No s,onificatit
local drainage facilities have been developed within the perimeter of these channel,• although the CCWt)
adopted a comprehensive plan for surface water drainage for the area in 1966. Mons,' of the provision'.
of that plan remain valid and have, to the extent applicable, been included in tho rvrreht master plan
1.4 Conckrsions raid R . . ,lotions
Storm }boding in the City of Palm Dra•rt is an i ir.iqurant but a significant prohtern, the el try, t )n c.f
which wilt require the efforts of the City, acilacent cornriunrttes, and of the Coachella County Water
District to provide a coordinated progr,im for reoional and !oval flood control facility improvements.
The implementation of the comprehensive master drainj,tr, Han developed in the; study will provide
the City with a level of flood pratecti v' rr'nerath• con ..lent with that of other Svirthern C,j!ifnrntia
Communities. The project cost of the ,ystem pro,; ci,ed t t the master plan (,nc!i,rl,rrq surf UP
improvements) is approtrr' ICIy $18,,>b0,000 based nii terenl constru>'!,o'i 1n i.,
Various methods of funding drainage systern irnt'rovernent, are avail to r+ c' City. Arvin q th, ,e arc
bond issues, as-essment district proceedings. and ,off !site, dra,nage fees > +' irq' ; t t> ,. r tnttinq per ; rrtu>s.
federal grants, and redevelopment turd',.
I1 is rpcommenr)ed that the adopt the cornorehensn,e plan of d;,fi> age as u t (,rt1. h':'ein as the. .
-drainage element" of the Genera! Pia, of the City of Palm Desert It is furthw r rr,• : n r ''>ded that an
implementation program be initiated and the anrropri,,re t,r„nc.ing m,-toocls he
CHAPTER 2
STI.IDY APPROACH
2.1 Existing Drainage Patterns end Facilities
The prevalent drainage pattern in Palm Desert is ovntland fl+iw in .r r rthe.rs,erty dir>',_tron to the
Whitewater River Stormwater Channel. With the ear( t'tipn of i.omc areas adtar:r'r t to the Paten Valley
Stormwater Channel and the area southerly of laaystacklRoad, runoff water flown predominately l0
the north, and to a lesser extent 10 the east, c,'tnnatr I'; dr'a_h.atging to the iNh,trr; tier Stc,rrrw,+ter
Channel.
At was indicated previously, the City of Palm Desert has, for the most part. devc:inped on the alluvial
fan generated by flood flows from Dead Indian and Caren Canyons located in the Santa Rr''xi f.4onnt,r ns
south of the City. These watersheds have, hrst:xically, constituted the orim.rr'; threat of coat a tia'd
damage to the City.
The Coachella Valley County Water District i- the agency responsible for regiceal flood control protection
in the central and the southern parts of the Coachella Valley. The CVCWD was organizer/ in 1918 iindm
what is now known as the County Water District Law (Division 12, California Water Code). t't 1937 the
District and the Coachella Vaiiey Storm Water Distre_ t merged, leaving the CVCWD as the surviving
agency and resting in it the powers of a flood contra! agency. The Distract owns and mamtarns srve°•.il
maior facilities which provide flood protection to tt,:. City of Palm Desert. Among tlica> are 'he Dr, p
• Canyon. the Palm Valley, and the Whitewater River Stormwater Channels. The CVCWD has.tho re ,orrs,bility
to protect the local communities arch as Palm Desert from flood,.. originating upstream or in the arts tr eat
mountain ranges. Officials of the CVCWD have ateor' 1 City staff that the existing D,>et, Canyon and Palm
Vettey•Stormweter Channels: re of sufficient •.;apectty to protect the City of Palm De,, -it front ft.>,.1, cal
100-year frequency. They also indicated that a "standard project storm" may e),ated 1i' = r 'city of
—7-
existing drainage facilities. In simplest terms. the standard project storm is the most intense rainfall
observed in the area or in any meteorologically similar area.
The Whiteweter River Stormwater Channel is the major watercourse in the Coachella Valley and provides
the primary outlet for storm flow from the Palm Desert area. In developing the Master Plan of Drainage,
it was assumed that most undeveloped properties adjacent to the channel will be drained directly to it by
storm drains constructed as development occurs. These facilities will be generally of a local nature and
likely the responsibility of the owner. As these reeperties develop, project proponents must provide
drainage facilities to protect the development from flooding or show that no additional facilities are
needed.
The Palm Valley Stormwater Channel passes through the westerly part of Palm Desert, intercepting water
from those portions of Palm Desert which he westerly of the channel. The channel is sufficiently low in
some reaches to accept inflow from adtacent areas to the east. However, some reaches, are too high with
respect to the adjacent greend to provide a sate r•rctory storm drain outlet. Therefore, miich of the area
which lies adjacent to and easterly of the Palm Valley Stormwater Channel has not been ,ncturio I rn
that channel's tributary drainage area All of the veil that Tres westerly of the Palm Valle', Stormwater
Channel and southerly of El Paseo drains t;, the heeler I in natural watercou' ;eT._ Doe IC) the nature of
the existing terrain and small parcels of land, it is unlikely that there will be <rr`y manor modification in
the Overall lanolorm in this area. It is as'irr'ed rt at the eyisteig natural drainage crierv", wilt remain in
the ultimate develnomen1
Deep Canyon Stormwater Channel generally skr'r', the ',ouN,9,r`;terly p.rrt Of Pale, Do'.rrt. Any development
•r'currrng soruthreIv of the charnel mutt tie oreeeted be construction of additional levees andiur channels
to prevent flooding by flows generated south a• d west of the City. Some drainage from the City is
currently being discharged t0 the Deer' Canyon Store -A, rter Channel. Recent discussions with the Coachella
`:alley County Water District concerned the el{i" t on the adequacy of the Deep. Canyon Storrn,vater
Channel if additional diversions of Itx.al storm +'. 'w Were directed 10 it, Representatives ,,f the CVCWD
have assured the City that diversion of runoff rem areas ' cir'herly of Hayst,rcl Road car he riiptr d
the Deep Canyon system.
Together, the Whrtewater, Deep Canyon and Palm Valley Stormwater Channels virtually c•nJlose the.
presently developed portion of the City. Since trese facilities are the responsbility of the CVCWD, the
scope of the master plan study was specifically l.mrted to those drainage areas within the perimeter
formed by the major stormwater channels The assurances of the CVCWD as to the arlr'dirir,y of its
existing channel facilities to protect the City frem upstream storms has been accepted and no rndependerlt
analysis of the upstream watershed his teen c reduced as a part of this investigation.
2.2 Flood Frequency
In determining the level of protection desired far a community, it is essenn,il to have an understanding
of the term "flood frequency." Flood frequency is generally defined in terms of the number of
occurrences off a given intensity level in any one period. Storm inter,srttas are usually identified as
relating to a particular "flood frequency," typically 10, 25,50, or 100-year events. The iise of "return
• year" terminology is common since rainfall intensity and runoff quantities are generally recorded on an
annual basis. Any particular flood can then.be defined as a certain rate of peak runoff occurring air
average of once in a certain number of years.. For example:a 10-year frequency storm means a storm
that would occur, over a very long period, on an average of once every 10 years Sim'rarly, a 100.year
Storm would be a storm which, on the average..vduld occur once in every 100 years The larger the
recurrence interval number, the longer the interval between storms and the greater the storm 'unotf aitd
potential for causing damage.
Drainage facilities we usually designed to provide protection from storms of a specified intensity.
Presumably lesser intensities weutd only oa►trat►y fill the drainage facilities, and arearer rntenr•itias
its
•
411
µno
iH
p�P
would generate runoff quantities that would fill the drains and create excels flow which would travel,
as storm waters currently do, by overload flow to the Whitewater River Stormwater Channel,
Many communities throughout the United States have adopted flood protection critnr,a against 10.year
frequency. storm flow. fay comparison, the Flood insurance Act of 1968 requires flood protection for
a 100-yedr storm.
Generally speaking, as the area tributary to a drainage facility increai, r in size, the storm frequency
takes on a greater significance. For example, hydrolon c st,eities fnr floods of 10-year and 50-year return
frequencies were conducted on two drainage basins oa srrn,I,rr cl,.+•,lc terat;r-s but with .areas of 100 ar res
and 1,000 acres respectively It was found that while ranr,ff rates for the 50-veer storm were, in both
cases, nearly double three fit, rah 10-year flood the flow ,-Pte from the larger basin increased by 1,0?0
,s compared to an increase of 103 cfs for the arnaffor no The significance in these magnitudes is that
facilities serving larger tributary areas may need to be sip if to carry higher intensity t rni flews raae to
the possible inability of the tandfora streets, etc., r,urrr, „ ling the drainage far 'lay to safely
accommodate the excess flow.
The analyses used in this study were based on the cancrf,t that f rotection from storms of gr,.',3tnr than.
the )(}year frequency Carl L.. offered by J corrbIna tion of street and overland flow in combination of
street And overland flow ,n Combreatwn with a coriareees ,yst,-m di•signrd for the 10-year flo d.
2.3 Methodology
The ape LJi..h used to defm:, the comprehensive local dr-,iu age .ystPn, for the City of Palm Des rt has
been developed using hydrolrxtra and hydraulic. criteria of the Rarer -ea County Flood Control and
Water Conservation District.
The initial thrust of the investigation war. to determine which filailitiria were regional in n.iti,re and thus
the responsibility of the Coachella Valley County Water District rather than that of the City It way:
concluded that the perit,hetat channel and dike system i c,nsistirie of the Wh,tewater, Palm Valley and
Deep Canvan Stormwater Channels provided regional pror, cti n ,and thus established the logical
limits of the study. Accordingly, the study area for the :mister plan of drainage was dt"fined as thrr,,'
areas of the City of Palm Desert located within the net,, ,ref channel system. Haying estah'isiiiid ttxe
study area boundaries, the following analyses were maJ
(1) Alt drainage areas within the study area were droned m det.a+l.
(2i Existing drainage facilities were classified and der emented as to size and location.
(3) A field reconnaissance survey was conducted tn \wife areas of frequent flooding problem;
(4) A hydrology computer model was established. Data on tar+d use, draireete patterns,
and rainfall intensity were input into the computer model
(5) Estimated runoff quantities were determined using the computer model for each local
drainage basin of the City. Quantities were established for 10, 25, and 50-year frew-1uen,:y
storms.
(tit Additional data such as that on existing topography, piprfrnc lengths, and design criteria
were included in the computer model, and analyses were performed to determine the
facilities necessary to satisfy the flood control requirements for each storm. Storm flows
were considered to be carried 'o existing street sections as long as sufficient capacity
eats available to carry the flood flow without damage to adjacent properties. Alternative
drainage systems were developed to satisfy protection needs for the various storm
frequencies
—9-
1'1#'" f 4. {r'-.a',~
't
(7) The various alternatives were analyzed to determine the most appropriate system for the
study area.
(8) Numerous alternative designs were considered for the 10-year flood frequency to establish
the lowest cost alternative which would adequantety provide for that level of protection.
The alternative drainage systems included consideration of retarding basins, open and
closed conduits, alternative system alignments, and diversions to existing regional storm
water channels.
(9) Having determined the lowest cost alternative which would satisfactorily provide flood
Protection for the 10-year frequency storm, additional sub -alternatives and refinements
to the plan were developed and te-ted in an atrempt to optimize facility development.
1tw various proposed facilities were then prioritized en the hasis of their irnportancxi to the overall
system function, their cost etfrctiveness, and their rr'r.,rcve l.,,ation wishin the overall system. the
►esniting plan is presented as th.. recornmcnded klase + Plat, of Drainage for the City of Palm Desert.
CHAPTER 3
TECHMU AL STur)Y
3.1 Hydrologic Studies
Hydrologic studies conducted in connection with the master plan investigation were conducted
utilizing the -rational method" adopted by the RCounty Flood Control and Water Conservation
District. The District's method and etiteria have been developed from, and are generally consistent with,
data generated by the California State Resnurcr's Art ncy. The rational method is also used by the
Coachella Valley County Water District.
The rational method computes runoff as a fuectio,, e< area, rainfdll intensity, and a coefficient of runoff.
The basic formula used in the rational method is a, fellows
Q ,a CIA Where:
Q = Runoff (in cubic, feet per second)
C = Coefficient of runoff
I = Rainfall intensity (in inches per hour)
A = Land area ti.) acres)
Hydrology computations were made using computer analysis techniques and program HYDRO.• This
program considers "internally" factors usually ignored or considered separately by manual methods and .
permits the addition of certain refinements to the formula. The following discussions.beiter do crihe
the method "and criteria used in the hydrology study.
3.2 Coefficient of Runoff
The runoff coefficient is a factor which represents the ratio of the quantity of stormwater runoff to
the quantity of rainfall staking the earth. The runoff coefficient is a function of numerous factor,, the
most significant of which are the type of development and the infiltration capacity of the soil. Program
HYDRO computes the coefficient of runoff on the basis of the following formula.
!HYDRO isacomputei program for computation of storm runoff based on the Los Anrlelr''s Cunt/ Flop()
Control District Short -Cut Rational Method; O►iginafty programmed by the Los Angeles Cour•ty ft'.>ad
Department end subsequently modified by Wifidan Associates for use in Orange and Riv'rsr.l" coter!trf:'e.
-10-
'•
ryl
C 1 C
100 100 A
Where:
C ▪ Coefficient of runoff
P ▪ Percentage of impervious area
▪ Coefficient of runoff for undeveloped or agricultural areas
The type of development affects the runoff coefficient since infiltration rates vary significantly with
different types of development. For example, agricultural land generally has greater infiltration capacity
than land devoted to commercial or industrial diiveI pment. In addition, the precentarte of coverage of
..nperv,' us material on the grnond surface is sq'ufr,?ntly 1.fferent for the varinu, type::, of development.
The runoff coefficient (C) also varir. with respe t to the •-ceffu-rent of runoff from undeveloped or
ay cu'tural land (CAI.. This value is unique to e.+c:h util t,'or. There are two prevalent <r l types in the
Palm Desert area (U.S. Soils Conservation Service l irvlogrc Soils Groups A and B). Born types have
relatwely high infiltration rates and are not prone to swelling when wet, therefore, they generally retain
their infiltration rate teoar,;;c.>s of their rfr'ree of atura1 vn. Tt', val,,c's of CA• are qra; hu ally represented
in Figure A 1 (Appendix Al.
The runoff coefficients computed using the for'nu!a contained ir, : r„gr,jm HYDRO result in considerably
higher runoff values than those predicted in the 19Gti rec.., tPrepared for the Coachella V,a!Ioiy County
Water ;.,t,urct by Wesley Hylen.
Table 3-1 compares the runoff coefficients used in the current report with tho.e used by t-iv'en. Comparison
of these coefficients indicates that computed runoff rates using the formula contained in program HYDRO
will be on the order of 30% to 50% greater thaor those computed using the Hylen coefficients The
difference in these coefficients is attributable to the percentage of impervious materials assumed for
ultimate development. This subject is covered in more detail in Sert;on 3.4.
It should be noted also that the land use data (Wilsey & Ham, January, 19751 used to establish runoff
coefficients in this study was not available to Hylen. Tt.j' the (orient study has benefit of an adopted
general plan upon which to base more definitive coefficients.
TABLE 3-1
COMPARISON OF RUNOFF COEFFICIENTS
HYLEN 11966) VS. HOUSLEY/WILLDAN (1976;
Soil Group A
Soil Group B •
hand Um Nylon Houslay/Willdan Hylen Housley/Willdan
Commercial 0 60 0 84 0.70 0.85
Multi -Family 0.50 0.70 0.65 0 81
Single Family 0.40 0 65 0.60 0.78
—11—
3.3 Sainte! Intensity
Intensity is expressed in inches of rainfall per hour and is developed by statistical methods from recorded
rainfall data covering as many years as possible.
1her e are no rainfall recording stations in Palm Desert that have the type of equipment nrcesary t3
establish rainfall intensity determinations; therefore, the rainfall intensity data utilized in this report are
bawd on hydrology data developed by the Resources Agency of the State of California for the Thermal
and Hayfield gauging station', These areas are con',uf'-rid by t'ie Riverside County Flood Control District
to be ni,•r,•orologically Similar to the Palm Springs,'Irni'n req.ixi.
Rainfall intensity rates are the result of many factors• the moist sinnifi alit of which is the duration of the
i' 'rr ae 1 the statistical average rerirrrence interval 11O year. <5.v,,, r, r.il-y"ar, anri 100 year).
The relationship between the rainfall i-itc'nsity and the duration of the storm is a complex, in,erse function
that can be character s/ed by the general staternetit that rarrta.l interi\+t.es for a given ref-urrenre interval
;an be vary high for short lr nails of time, regressing to lu;, • average v.-ti,rrs as ti+i time period it inf reasr'd.
3.4 Coverage of Impi!rvinrra Material
The following table suiernarizes the Percentage t.o.i rage of in P rVienis materials for the arious types
of development that were utilized in preparing the• nets.:.!atinns for this study
Coverage of
Development Impervious Material
Commc rcial 90%
High Density Residential 80°f,
Medium Density Residentsi! 70%
Low Density Residential 60
Combination Golf C'Iorse
and Condominium 40 • 50%
Various percentages of coverage were developed from Lifter la established in areas having similar land
uvr characteristics. The following table illustrates the coverage anticipated on a typical low density •
residential lot.
TABLE 3-2
IMPERVIOUS COVERAGr ON A TYPICAL
10,000 SQUARE FOOT RE`,IDENTIAL LOT
Type of Surface Area (S.F.)
Buildings (House + 2 Car Garage) 2,650
Street 1,450
Patio, Driveway, + Walks 1,300
Swimming Pool• 600
Assumes 1/3 of ail homes have pools.
—12-
6,000 or 60%
•
I?II 04 I'
Generally. the land uses specified in the Palm Desert General Plan (Wilsey & Ham, January, 1975) were
used in computing discharge rates. In a few instances, however, existing land use was substituted. This
occurrred in those locations where existing development is not totally consistent with land use classification
indicated in the General flan and where it appeared unlikely that redevelopment would occur in the
foreseeable future. Examples include existing expansive single-famity developments in arras de .ig rated
as medium density and developments such as Marrakesh Golf Club, which although der.lgnatrrii e, a
medium density area, is unlikely to be more densely developed.
3.5 Time of Concentration
A major premise of the rational method is that the greatest discharge from ttie are.► ()caws when runoff
from the entire area is contributing to the ftnw passing the point of concentration. Since the rainfall
intensity is decreasing with respect to the duration, the maximum discharge occurs at the shortr«,t
time period required for water to travel from tor, furthest t,:unt of the drainage area. That time teriod
is identified as the "time of coil :ntration."
Program HYDRO computes the various time. coo, entree .n individually ter each sub-,+rre in the
drainage basin. The selection of sub -arras eel have a ,ign,hcant affect on the computed times of
concentration. This is particularly true with r' sect 10 the e,*iear.,,is at the upstream end et rya, h drenaee
basin. The size and configuration of these :e .1lea, deb rreines the "initial" time of concentration for the
basin. Since the 1111ttat time of concer+tratin,l rir ierrae.,' th' ralr'r;all Ine.nety 10 he use'i ter any
particular storm frequency, the selection n' ti . 1ne ii sub.ar"a . ,re significantly effect the tote runoff
.1. .an1,t!PS.
Since the rational method of estimating runoff is moo ace nr,itr.• when applied to small basins, it is
desirable that the sub -areas (and particularly the inir.„+ it ,:t tj, lept relatively sn+afI the i.:1'e of the
initial areas of concentration used in this r vesegitien rarer) between 10 and 90 acre; arld ra- less
than 40 acres. It is anticipated that more detailed hivdrolixiie studies will be conducted nl conlunction
with the final design of storm drainage facilities. Sur . i"i sh"ild limit the size of the motel tributary
area to 10 acres.
The selection of the initial sub -areas appears 10 accoint for at least a portion of the difference in
runoff rates computed in this study as compared tc, those computed in the Hyleri investigation in 1966.
A review of the hydrology calculations upon which the Hylen study was based indite -we that initial
sub -areas ranged from 25 to 170 acres in area with an average of about 70 acres. While no attempt was
made to quantify the increase in the Hyten flow r6te; that would result from the use of smaller initial
areas, this difference in approach accounts for a srq' ificrnt per en of the disparity,
3.6 Hydraulic Studies
Hydraulic studies were initially determined during hydrology studies using the computer mode/ and
program HYDRO. These initial designs were then refined using program STORM''' and through manual •
adjustment of the system elements.
Facilities for the conveyance of stormwater were sized to accommodate storms of 10-year return
frequency. It has been assumed that runoff in excess of that generated by the 10-year storm will be
conveyed on the surface. This assumption differs considerably from that utilized iri the previous
master plan developed in 1966. Under the earlier (Helen) plan the 10-year frequency storm flow would
have been carried by a combination of surface and subsurface conveyances. The water was to be conveyer)
on the surface until the carrying capacity of the street was reached and the remainder was diver ti d
to underground conduits. The conduit system itself was thus sized for something lees than the 1n 4Cer
storm.
°STORM is a computer program designed to corn ete the hydraulic gradient cf stet rn drawee' r, ,ti ms. •
STORM was originatty developed by the Los Angeles Cr1,snty Road Department.
--13—
»y
The significance of this difference is that the current plan reserves the capacity of the streets for storm
flows in excess of those generated by the 10•year frequency storm, while the 1966 plan required both
the street and subsurface conduit system to carry the 10-year frequency storm. The approach used in the
current plan does, of course, require larger facilities but it provides for a measure of protection from
storms of greater intensity.
In the current study underground storm drains were generally assumed to flow without pressure.
However, in some instances, particularly where other facilities such as open channels or retarding
basins required higher hydraulic gradients, pressure flow was permitted provided that the energy gradient
did not exceed the ground surface. For the most part, subsurface drains were assumed to be established
on a slope parallel to the ground surface along their route. Pipeline sizes were selected to the nearest
3-inch diameter; however, in some instances, box culvert alternatives were analyzed when circular
conduit sizes became unrealistic in team of potential availability and/or feasibility of construction.
Open channel designs were based on the most e'fechve section (considering construction conditions
and maintenance costs) and as uming uniform ferny with the water surface generally parall<,I to the
longitudinal crad,ent 0f the channel. Depths o1 the channel were estahl;shnd ge•ieratty usmg two feet of
freeboard between the estimated water surface aril the tor' of the channel wall
Hydraulic design calculation included in both computer r'fxtrams are based on M.e,ntng'e formula.
The formula and its terms are descrih+.d as follows
V e 1.•l86 Rr3 sin
n
V - Velocity of Uniform Flow fleet per secondf
n = Roughness Coefficient
R = Hydraulic Radius (fr't)
S = Slope of Energy Gradient ile0 per foot)
The following values of n were used for var,ou', elements of the conveyance system•
Reinforced Concrete Pipe ',RCP)
Reinforced Concrete Box
Open Concrete Channels
n=0.01'1
n = 0.015
n = 0.015
In all cases, hydraulic analyses assumed that the 4treets would be free and clear of any major
• obstructions and that storm drain systems would be adequately maintainers so that blockage would
not occur.
3.7 Retarding Basins
Among the alternatives considered in the development of the comprehensive master drainage plan
ayes the incorporation of retarding basins in the facilities plan. The major benefit of such basins is in
achieving a reduction in the size of downstream conveyance facilities.
For the purposes of the invetigations, it was assumed that retarding basins would:
• (t) Be utilized as multi -purpose sites. perhaps as parks, playgrounds, or /Or similar recteerit, ...t
purposes..(Development costs for secondary rises were, however, not included in the �t
analyses.)
(2) Be limited in dimension to avoid designation under State criteria as a major impoundment
or dam structure.
(3) Be placed only in areas of generally compatible land use as defined in the City's General Plan.
N;ne potential sites for retarding basins were investigated using the general criteria listed above. The
locations of the various sites and approximate construction costs are shown an Figure 4. Of the nine
sites considered. only Site 8 presents a potential for reduction in construction c;)st. eve, hire, the
potential for.savings is available only under limited circumstances.
The retarding basin at Site B, located northerly of 44th Avenue between San Pablo and San Pascual
Avenues, offers the lowest cost alternative if aesthetic, environmental, or maintenance con;ideratiers
restrict the conveyance structures between 44th Avenue and the Whitewater River Stormwater Chai.nel
to closed conduits. However, if open channels are found acceptable, the retarding basin would have no
economic advantage.
Other considerations relating to the retarding basin r oncent include.
Advantages
(1) Open Soace — The retarding basin would establish a form of publicly held open
;peer wench could be utilized for some aecr)nd.+ry recreational uses.
advantages
(1) A retarding basin at Site B appears incc'r taitible with the City's Land Use»
Element. The General Plan indicates land use at the proposed site to he a
combination of medium density residernn,il and crneral institutional use.
(2) Maintenance Cost — To be aesthetirall, 4r)d environmentally acceptable„ a is
assumed that the basin would reouire en :,ttraenvely landscaped buffer around
its perimeter. The irrigation and maintee « ce ; f horn 4 to 6 acres of land-
scaping would represent an additional o; «rational cost.
(3) Hazard and Liability Aspects — When functioning as a retarding basin, the •
facility would present a potentially hay arrdous c:nndition. This is particui 1rie
true if, as assumed, security fencing is cieesidered aesthetically unacceptable.
(4) Reduction in the Tax Base — The acou".ition of acres by the City for use as
a retarding basin would result in some diminishment of the community's
available tax base.
The results of the investigation of retention facilities indicates that their value in the drainage system
is limited. A retarding basin at Site B aopears to he feasible only if a closed conveyance structure is
required between 44th Avenue and the Whitewater River Stormwater Channel. Rena.ding basins at other
locations within the City are not considered advantageaes under any circumstances afforded by II le
established criteria.
—16—
1,---irreirr-Trilm• ,
I : 1r: '114:11'
! ;
•
t.
, .
,,, • , •„
•
"Iivirrtio
___.,:.— 41 ''''''''!%ArLi ' • '''''''' 'vhilit,...,:i kVA,: ‘•••:-.:141;),-7,-.....-; - .44.6'' .0.' l'i
—10 • : : ',.- ,,...- „, ii:„ ,, i . j:!47,,...•.„..,,,,,,,t,1
: .
l',..____.' .....ii,
ii.,•..".r.77. -77-..
r.):;,..„--..---_-,....„.._.
. „, ..,. • „,,....... .........„.
,..„. I i . f • •1.' .1' '' ' rr, '" • ".,,,:\!• \-•'-' 1 .! : 1
'‘'.1,.., ..!", !it:".....,...' ' ' '.. 1:1,1_ r r • ..., !‘„_:•r, • ,.„, .
.. .
‘,......„.4.. .,. r,4.
. 111.C:47: ' e:t 1. ri,vi i."Iii.,-:.-..1*;..!.4'111.7.-----'f,'\'',..V‘!"•: . .
„, ,..../.... __
131.-•,4",t, 4- '44.
t
ZfLJ
;
S '??
‘,1;6'f'f' 1$, •
••••! • dobr.'r
t's —
rr.,•;;ri
ralkTirer
PPM
' POO POP 41.,
omeet. - •
.P.:
PPP. 4.
II
4
r;
.,••••
Illo.mtorrtr,,,rtarLaUll•r,trarer*ty.11
r••••"; ••••••••
;
r-,!!
1111•••11 Irtf :fr.**
a,,- Are V. -1 111,00. arra
fltWN
rifiTust
•
fOk
IIMIITAMIDINal *AN CONCEPT
IMUNI, SONO 0/11//11a arms
VAINDINOB 16/4181,41 Onalre
- "•.•;••r ;
MASTER PLAN OP DRAINAGE
CITY OP PALM DESERT
RETARDING BASIN
CONCEPT
I. HAROLD HOUSLEY
• CONSULT ING ENGINE E RS •
IN AILOCSCIATiON WI T H
WILLDAN ASSOCIATES
lictruFlIF. 4
CHAPTER 4
PROPOSED MASTER PLAN SYSTEM
As a result of the investigations summarized on this report, a comprehensive master plan of Ioc,at
c ;p drainage was developed. The basic plan provides for flood protection from a storm with a return
frequency of 10 years, In addition to subsurfacsi drainage facilities. the plan protooses certain surface
Improvements, primarily construction of curb and gutter, considered necessary to provide for adequate
drainage.
The recommended plan inclue: s both underground .end open channel conduits. The varios coe've,ance
facilities utilized in the master plan are ilt,rstrated In Figure 5,
4.1 Identification of System Elements
In order to easity identify the various system etemo.'ts, reference codes have been assiitned to each
read of pipe. The reference codes consist of letter prefn' followed by a number, The prefix code Indicates
the major system branch. For example, the San Pablo Branch is identified by the codoe SPB, the nurnerictt
portion of the reference code generatfy indicates the relative location of the rear)). Numbers wert' assigned
er: rocreasing numerical order from the downstream end of each branch, Thus, a p+o9 reach with a small
number can be expected to be Located near the drwnstream end of the branch, while one with a relatively
large nurnber can be found near the upstream end „f the braea-rh or atonq a lateral line. Table 4.1 lists the
reference codes for the various trunk systems.
T.ehle 4.1
FACILITY IDENTIFICATION CODES
Prefix Branch
8 Buckboard
OC Deep Canyon
H Haystack .
Ironwood
M Monterey
P Portola
PV Palm Valley
SPB San Pablo
SPL San Pascual
TP Toro Peak
42 Drainage Area Designations
Drainage areas have been identified by their relationship to the ultimate point of discharge, Each of the
tin major drainage basins previously identified have been subdivided into smaller drainage areas The
vicious basins end sub -areas sre indicated on Figure 6.
—17—
,
'Id
•
•
ALTERNATIVE
PgJERPFE7NpE
SYMBOL USED
ON
CMASTER PLAN TYPICAL SE TION
r---
/"
.....•••• vie maw _
. • '
3.
RecTANGQL AR
EuH2FAILE
/u
otoireakvo• ••••••••••..,.••
en....•••• ••••••••,...,
•
WV
CONVEYANCE FACILITIES
01.004,,
FIGURE !"5
4.3 Description of the Proposed Orsinegs System
The proposed system consists of five independent drainage networks, each of which discharges to
either the Whitewater River Stormwater Channel or to the Deep Canyon Stormwater Channel. Each
of these networks drain a corresponding maior tributary basin Basin 1 is the largest of the five tributary
areas. The area within its limits is bounded generally by the Whitewater River Stormwater Channel on
the north, Portola Avenue on the east, Haystack Road on the ,,oath, and Highway 74 and Palm Valley
Stormwater Channel on the west. The drainage system for Basin 1 discharges to the Whitewater River
Stormwater Channel at a point along the northerly extension of San Pascual Avenue. The drainage
network contains three major branches These are identified as the hiunterey, San Pablo, and Portola
Branches. A number of lateral tines extend tell, each of these hr mrmcnr'S.
Basin 2 includes within its tributary area mo•.t of lhr 1,rupertrr•s within the City lying easterly of
Portola Avenue. The tributary ae., also includes that ere hon ,,,,, City of Indian Wells hounded by
the Palm Desert city limits on the north and west, D'..,, Canyon Stormwater Channel on the south,
and the southerly extensrnn of Deep Canyon Av, nut r tht. , r;t The dramnane network for Bann 2
din charges to the Whitewater River Strernwafer Chan-+ : mid: , betvvoen Deep Canyon Avenue and
Conk Street. This drainage system core,ists primarily ,-,e the Toro Peak And Deep Canyon Branches.
B.+;ens 3, 4 and 5 all discharge to the r),•ep Larynn yt +rmw tr: r Ch eruct. i he bw,r,,, are ,,erved by
&A!lat..," sySterns rtr'gnatcd as the Haystack. Burkbn. t, and irerie,,,.ed Bevil hes respr,+trvrie,
Specific descrephons of the various elerr,r.nt•, of tree re !noseri mire t pl.,r+ area given in 'Table 4 Z
4.4 Alternative Systems
The recommend•d.facilities plan is shown in FIgure f, Howeser, a number of alternative sy.teres have
also been considered. A desermntmon of the cnalor a11,trativrs is trs fellows
fit
Tire Non -Diversion Attsrnative - in the ,nyest gat.i,n, some question was ra,,,rd
as to the capability of the Deep Canyon Stormwater Channel to accept runoff tr+)rn
lands within the study area As a result, r,- wider;,; mun was given to cares n't it .Ain }•Tt>
from the area southerly of Haystack Road tf'roun+r the Cmty's drainage system to the
Whitewater River Stormwater Channel.
Under this alternative, water would not be diverted to Deep Canyon Stormwater
Channel. as Shown in the recommer Jed pie, Instead, ,t would be conveye,l in a
conduit northerly along Portola Avenue lr"r'eng the Cty's dramnaee system in thrt
vicinity of Grapevine Street The capacity •,! downstrearr conduits would than be
enlarged to provide capacity for the addiroeal sr rvice area.
121 Closed Conduit Alternative - The recommended master plan of drainage ralis for
several reaches of the drainage system to c nnsmst of open trapezoidal channels. White
such channels offer the lowest cost alternative, there are certa;n maintenarce,
aesthetic. and environmental considerations whm.h may make closed conduits rn.)re
desirable. Under this alternative, closed conduits would be substituted for those
reaches of the recommended plan which presently utilize open channels
Because of the substantial difference in cnnsttuction costs between Cnncrete.itned
trapezoidal channels and reinforced concrete bnv structures, this alternative
t rural. extremely Costly without some means of reducing the design flow. One
such means is through the use of retarding basins. Under the retarding barn
concept, a portion of the peak storm flow is diverted into a reservoir nod herd
until the flow rate drops stifticir:ntty to provide Oe,tlet o peci1y down<.rreocr. TI,
retarding basin concept is illustrated in F .;;vie 4,
;I
i
{
—
r - 4
i4 .
1
• wow X
$ •
.4,
- *-•
, 41417'1 ,
t• •
•
t •
11;0 • '•
1•';'•
1 • ;
; `o=
•
*•-*
"0 11
410
0
170 )4r-x-
rNW 44 1.
• • • 10.0•••• 0.01.
4,•
$ I I * , • •
• "0
HS
1-."-e-
•••••
saw - war ••••• ,
* ' • *'**"" " •
1,.
•.(1.;
(ii• ;$1
-)
L
st0Ft4 Ati,t
SI 12 •
W 4WD 4MW,..
6 5
I. HAROLD HOUSLEY
CONSULTING ENGINEERS
IN ASIBOCIAT ON WITH
WILLOAN ASSOCIATES
t,00 04 • 14140ev
00 MN WWW0m0aw
: ',„••,*,- •
MA.SUD% PLAN tii=• OPAIIMAa!
CITY t3P PALM pt[$e!
FACILITIES PLAN
TABLE 4-2
DRAINAGE MASTER PLAN DESCRIr1ION
FACILITY ►NIORITY PROJECT FACILITY SIZE LINOTN DEVON FLOW
COOS COOS COST ti TYPE (FT.I (CPS)
Buckboard Branch
8-1 5 8 20.000 39" Pipe 200 120
8.2 6 70.000 36" Pipe 700 120
8-3 5 60.000 33" Pipe 700 50
DC-1
Der!rt Canyon Branch
3 S150,000 8' x 6' Trap 1200 410
DC-2 3 60.000 8' - 6" Trap 500 385
DC-3 4 ' 310,000 78" Pipe 1400 310
0C4 4 90,000 51" Pipe 800 205
DC-6 4 30,000 48" Pipe 300 175
DC-6 4 110,000 45" Pipe 1000 140
DC-7 3 140,000 48" Pipe 1100 85
DC-8 3 80,000 42" Pipe 700 65
DC-9 4 70,000 39" Pipe 700 80
DC-10 4 70,000 33" Pipe 800 45
DC-11 4 30,000 21" Pipe 400 30
Haystack Brooch
I61 4 60,000 72" Pipe 300 545
H•2 4 350,000 72" Pipe 20JO 475
H-3 4 260,000 63" Pip. 1800 450
H4 4 150,000 48" Pioe 1200 250
14•6 6 60,000 42" Pipe 800 130
H4 5 110,000 36" Pipe 1200 130
141 6 110,000 33" Pipe 1200 70
144 4 140,000 46" Pipe 1300 175
H-10 4 70,000 42" Pipe 800 156
14•11 4 30,000 3111" Pipe 300 170
14-12 4 30,000 36" Pipe 300 95
H-13 4 70.000 30" Pipe 600 60
—II—
LOCATION i LIMITS
Buckboard Trail, Portola to
Deep Canyon Channel
Buckboard Trail, Birdie to
Portola
Buckboard Trail, Littleband
to Birdie
Alesandro Drive Extension
Deep Canyon to Toro
Peak Ext.
Deep Canyon Road, Hwy 111
to Alesandro Ext.
Deep Canyon Road, Candlewood
to Hwy. 111
Deep Canyon Road, Peppergrass
to Cindtewood
Deep Canyon Road, Fairway to
Peppergrass•
Deep Canyon Toad, South City .
Limits to Fairway
Paint Desert D►. (Hwy. 111)
Panorama to Deep Canyon
Palm betert Dr. (Hwy. 1111.
El Paseo to Panorama
Candlewood Street, Panorama to
Deep Canyon
Candlewood Street, Ouailbush to
Panorama
Fairway Drive, Panorama to
Deep Canyon
Haystack Rood, Portola to Deep
Canyon Channel
Haystack Road, Moon to Portola
Haystack Road, Marlbouro to Moon
Marlbouro Drve, Littlebend to
Haystack
Marlbouro Drive Extension, Mesa
View Ext. to Litttebend
Mesa View Driya Extension, Alamo
to Marlbouro Extension
Mesa View Drive, West of Praire to
Pairs
Haystack Road, Alamo to Marlhrarro
Alamo Drive, Skyward to Haystack
Alamo Drive, Bat AN to Skyward
Alamo Drive, Homestead to B« Air
Homestead Road, Beverly to Alamo
..i
Table 4-2 Drainage Master Plan Description Cont'd,
FACILITY PRIORITY PROJECT FACILITY SIZE LENGTH DESIGN FLOW
coos ' COO* COST a TYPE I IF T. ICES)
LOCATION II LIMITS
Ironwood Branch
1.1 5 80,000 60"Pips 400 265 Portola Avenue, at Deep Canyon
Channel r.
1 2 5 110,000 51" Pipe 900 265 Portnla Avenue, Mariposa to Nissp
Canyon Channel I
1-3 5 210,000 42" Pipe 2000 190 Portola Avenue, Quercus to Mariposa
I-4 5 250.000 33" Pipe 2800 75 Portola Avenue Extension, West of
Della Roma to Oueicus i
t
Monterey Br tench
61-1 3 440,000 1 cor Pipe 1300 765 44th Avenue, San Anselmo to
San Pablo
M-2 3 400,000 102" Pipe 1300 575 44th Avenue, Monterey to
San Anselmo
M-3 3 190,000 63" Pipe 1300 275 Monterey Avenue, Pancho
Grande to 44th
M-4 3 , 190,000 60" Pipe 1300 215 Monterey Avenue, Highway 111 ,
to Rancho Grande
. ,
M-5 4 100,000 48" Pine 800 180 ,
Highway 74, El Pasec- to Hwy 111
M-8 4 90,000 48" Pip. 800 130 El Paseo, Ceobilo to Hwy 74
M-7 ' 4 50,000 45" Pipe 4C0 95 Ocotillo Drive, Tumbleweed to
El Paseo
M-8 4 . 80,000 39" Pipe 600 85 Tumbleweed Lane, Shadow
Mouitain to Ocotillo
M-g 3 90.000 80" Pipe 600 145 San Anselmo Ave. -ue, San Nicholas
to 44th
M-10 3 40,000 54" Pipe 300 110 San Antelml Avenue, Catalina to
'San Nicholas
M-11 3 80,000 48" Pipe 600 90 San Anselrno Avenue, Royal Palm
to Catalina
M-12 5 180,000 48" Pipe 1300 75 Monterey Avenue, rarkview to 44th
04.13 5 220,000 66" Pipe 1300 185 44th Avenue, Fairhaven to Monterey
• •
•
Table 4 2 Orthrage Matter Ptan Qeeyiption Coned.
Aellttr
coot+
PAIOQITv MOiet PACIUTY sat ufWm Deem PLOW
0002 COST ti TYPE IFT.1 OCPSI
LOCATION 1 LIMITS
PINTO'S Brandt
f-1 1 230,000 17 x 8' Trap 1300 810 Desert Star Blvd. Extension, Portota
to San Pascual Ext.
R2 2 440,000 102" Pipe 1400 770 Portola Avenue, 44th to Desert Stw
P•3 2 220,000 87" Pipe 1000 735 Portole Avenue, Catalina to 44th
P4 2 100,000 78" Pipe 500 585 Portola Avenue, El Cortez to
Catalina
P-6 2 250,000 75:' Pipe 1300 535 Portota Avenue, Highway 111 to
El Cortez
P4 4 250,000 72" Pipe 1400 430 Portota Avenue, Shadow Mt. to
Highway 111
P-7 4 790,C°_) 57" Pipe 1400 255 Portola Avenue, Fairway to
Shadow Mt.
P•8 4 180,000 57" Pipe 1300 245 Portola Avenue, Ctapevme to
Fairway
P-9 4 260,000 36" Pipe 1600 60 Grapevine St., Marrakesh to Portola
P.10 2 40.000 48" Pip. 300 70 Catalina Way, San Jose to Portola
P•11 2 30,000 42" Pipe 30C 45 Catalina Way, San Luis Rey to
San Jose
P•12 2 30,000 33" Pipe 300 25 Catalina Way, San Juan to
San Luis Rey
P-13 2 90,000 39" Pipe ' 900 35 El Cortez Way, Cabrillo to Portola
P-14 2 180,000 60" Pipe 1100 105 Palm Desert Drive, San I uis Rey
to Portola
P-15 2 90,000 36" Pipe 1000 25 Palm Desert Drive, Larkspur to
San Luis Rey
P 16 2 50,000 33" Pipe 500 65 San Luis Rey Avenue, El Paseo
to Highway 111
P-17 2 70,000 30" Pepe 800 45 San Luis Rey Avenue, Shadow Mt.
to El Paseo
P-18 2 30,000 17" Pipe 400 30 Sac Luis Rey Avenue, Joshua Tree i
to Shadow Mt. 9'
P-19 4 140.000 54" Pry* 7100 130 Mountain View Avenue, Shadow
Lake to Portota •
Palm Valley Ban,±
PV• i ' 3 70,000 48" Pipe 500 170
Bursera; Palm Valley Channel
to Pitahaye
PV-2 3 150,000 38" Ptpe 1900 , 80 Pitahaya, Bursera to Shadow Mt,
PV-3 3 50,000 24" Pipe 600 25 Pitshaya, Shadow Mt. to Hwy. 74
PV4 3 30,003 30" Pipe 300 45 Buriera, Palm Valley Channel to
Willree
—23—
Table 4-2 Drainage Master Plan Description Cont'd.
PA .trTY PRIORITY PROSECT PACILITY at2E
COST
COOS CGOE
8P81 3 S310,000
SP9.2 3 100.000
SP9.3 3 180,000
SP9-4 3 80,000
SP8-5 4 170,000
SP84 4 50,000
a TYP!
LIMOTH DE$MN FLOW
(FT.) ICrs*
San Pablo Branch
81" Pipe 1400
78" Pipe
72" Pipe
83" Pipe
63 Pipe
d0 r',pe
SPB'7 4 100,000 57" Pipe
SP8-8 4 170.000 51" Pipe
5PB-9 4 90,000
SP8.10 4 110.000
SP8-11 4 190,000
SPE/12 4 50,000
SP8.13 4 40.000
SPB• 14 4 30,000
4' x 4' Trap
36" Pipe
51" Pipe
45" Pipe
47' Pipe
38" Pipe
SPB• 15 4 60,000 30" Pipe
SPL• 1 1
SPL-2 1
SPL-3 2
SPL-4 4
SPL•5 2
TP-1
TP-7
TP•3
TP•4
TP•b
TP •6
$49C.000
280,000
260.000
70.000
160,000
3 S300.000
3 320,000
4 60,000
4 110,000
4 90,000
3 60,000
3 70,000
3 40,000
500
1000
500
1100
400
700
1400
1800
1200
1500
400
400
400
700
e
San Pascual Brandt
20' x 10' Trap 2100
20' x 8' Trap 1400
20'x8'Trap 1300
4'x4'Trap 1300
42" Pipe 1500
Toro Peek Branch
17 x 8' Trap 2200
17 x 6' Trap 2300
'18" Pipe 600
36" Pipe
24" Pipe
4' x 4' Trap 1300
42" Pip.
36" Ptpa
1200
1000
600
400
LOCATION a LIMITS
570 San Pablo Avenue, Royal Palm
to 44th
500 San Pablo Avenue, San Gorgonio
to Royal Palm
4R0 San Pablo Avenue, Highway 111
to San Gorgonio
440 Sun Ledge Lane. El Paseo to
Highway 111
410 Sun Lodge Lane, Joshua Tree to
Et Paseo
390 Burroweed Lane, Juniper to Joshua
Tree
360 Burroweed Lane, Ironwood to Juniper
795 Burroweed Lane. Grapevine to
Ironwood
115 Emir Dr., Salt Cedar to Grapevine
35 Palm Desert Dr , Sage to San Pablo
175 Grapevine St., Desert lily to Emir
180 Desert Lily Dr , Willow +o Grapevine
135 Desert Lily Dr., Bursars to Willow
110 Desert Lily Dr , Tamarisk to
Bursera .
40 Desert Lily Dr , Salt Cedar to
Tamarisk.
2790 San Pascual Ave Eat , Desert Star
Ext. to Whitewater River
1305 . San Pascual Ave , 44th to Desert
Star Extension
1295 filth Ave., San Pablo to San
Pascual
•
130 Desert Star Eet., San Pahl() to
San Pascual Eat.
410 San Pascual Ave and Catalina Wey
San Carlos to 44th
640 Taro Peak Roast Ext , 44th to
Wnrt.wat.r Rrv.r
525 Toro Peak Road Fat , Nor th of
Highway 111 to 44th
50 Toro Peak ;load Ext , &tuth of
Hwy. 111 to Ninth of Hwy, 111
50 Toro Peak Rnn1 Ext , CanU.wond
to South of Hwy 111
25 Tao Peak Road, Yucca Tr.. to
Candfewoarl
75 44th Ave., Osseo Canyon to Toro
Peak Ext.
60 Deep Canyon Road, Goleta to 44th
15 Nero Canyon Road, South of
Goleta to Groats
Nine separate sites were studied to determine the feasibility of the retarding basin
concept. With the exoeption of Site B (located northerly of 44th Avenue between
.San Pablo and San Pascual Avenues), none of the basins were found to be
economically feasible. Furthermore, the use of Site 8 for a retarding basin was
only feasible when used in conjunction with the clad conduit alternative.
A system consisting totalty of closed underground conveyance structures (i e.,
reinforced concrete pipe or reinforced concrete box structures) is. feasible when
combined with a retention basin located at Site B. Such an arrangement offers
a potentially viable alternative to the use of open trapezoidal channels.
13) Multiple Outlet Alternative - One of the plans initially considered in the
investigation was one generally paralleling that developed in the 1966 Master Plan
of Drainage. This plan calls for three discharge Tines from the City of Pairn Desert
to the Whitewater River Stormwater Channel. Analysis of this alternative
indicated that a more cost effeetiv'e solution could be developed by combining
portions of the drainage basin However, the multiple outlet alternative presents
some advantages in the es, et that open channel construction is found objectionable.
Under the multiple outlet alternative, clr-i aid , nnduin would be used to convey
storm flow to the Whitewater River Stormwator Channel. By maintaining separate
discharge tines for the Portola and San feiblo ':shams, the outlet facilities would be
mall ence+igh ie permit their t.t;nstr,;ction useie reinterced concrete pipe. The cost
saving el RCP over reinforced concrete tine seer:tures is sufficient to make the
multiple outlet alternative competitive with the combination of the closed conduit
alternative, and a retarding been at <Tete n,
The multiple outlet alternative would c*tend ins San Pablo and Portola Branches
northerly to the Whitewater River Channel. Additional branches and laterals would
be necesrary tp carry water from San Pascual to the major branches.
(4) Mufti -Frequency Alternative - An aesumtition basic to the analysis summarized in
this report is that storms having an intensity greater than the 10-year frequency
storm can be provided for by a combination of subeirface drains and overland flow.
Analysis indicates that design for a 10-year storm drain freneenry is sufficient in
those areas southerly of Highw.ty 111 where relatively steep ground surface grades
ere prevalent. However, in the areas, northerly of Highway 111, the streets and
tandforms adjacent to the drainage facilities new be unable to convey the excuse
flow. Consequently, alternative designs were considered to proviae capacity 'for
25-year frequency storms in facilities located between Highway 111 and 44th
Avenue tied for 50-year frequency storms in nose between 44th Avenue and the
Whitewater River Stormwater Channel. In providing for these multi -frequency floods,
this alternative offers a higher degree of flaied protection, particularly in the .
norther iv portion of the City.
4.5 Priority Schedule
The recommended priorities for the various drainage conduits are listed in Table 4-2. Priorities have
been established on the basis of J scale of 1 to 5, with 1 being the highest priority.
4.5 Surface I , ,
In addition to the subsurface conveyance facilities, certain surface improvements (notably construction
of curb and gutter end street resurfacing) are necessary to the overall functioning of the proc.rd
drainage system. The need for these rmprovements.is categorized es follows:
—25—
.•Yi'+r,:c..'. ,..�, ... _ - k.' ,�. .So,E.•4r.,: ,,.w. an L...,.i�
l'it:1„il�.:Lf"
(1) Surface improvements required in the streets were where physical improvements
will be constructed.
12) Surface improvements required to convey the stormwatee to the inlets and
conduits designed to serve the area and minimize short-circuiting private
property.
(3) Surface improvements required to prevent erosion of the dirt shoulders or
parkway. The erceion of the shoulders is a costly maintenance expense to the
City. Some of the eroded soil will also be deposited in the stormwater inlets
and conveyance facilities reducing their efficiency and increasing maintenance
costs.
The vast majority of the streets in the City of Palm Desert will require curb, gutter and other surface
improvements, if proper control of stormwaters is to be achieved. It is estimated that nearly 75% of
the City's streets carry sufficient volumes of water during perk storm periods to justify the•
construction of curb and gutter.
At present, only the central commercial area and the newer residential developments have full street
improvements. Streets in the majority of the residential area.. are uncurbed and have little or no Crown
to the pi:ement section
Figeire 7 shows schematically those locations where improvements are considered essential to the
drainage ystem's ultimate operation, as well as those additional improvements considered desirable to
the functioning of the drainage system, but not necessarily essential The amount of surface improvement
reeu,red v,,e -e considerably from street to street. Sorne streets will require full improvements and
reconstruc-tio,i. others, improvements on only one side, while still others will need only intermittent
reconstruction. The schematic representation of irepreaemeres shown in Figure 7 is intended to indicate
only the aenerat location of surfaces improvements related to the effective operation of the drainage, system.
It shoui,f.rrot be used as.the sole basis for retabltsieng steel reconstruction priorities.
Surface improvements should be considered for all streets ie the City including the estimated 25% of
the streets not requiring improvements in connection with Ice. storm drain system. Additional
justification for the surface improvements are.
(1) Curb and gutter is needed for conventional street sweeping equipment to function
efficiently.
12f Curb and gutter establishes a reference elevation to establish floor elevations of
structures.
(3) Curb and.gutter enables the abutting property owner to maintain landscaping
to a defined line.
(4) Curb and gutter permits separation of pedestrians and vehicles.
(5) Curb and gutter reduces deterioration and damage to the edge of the asphaltic concrete
paving.
It is recommended that the City of Palm Desert consider the adoption of a po:icy of installing curb and
gutter, driveway approaches, and cross gutters on all City streets. Unless a city-wide program for full
street improvements is implemented, the City will continue to experience substantial and contiruing
cysts for street maintenance.
-28-
I
MI M. 0111110111•10.
jjnYN notuumlamvatuntstet
a r !!!!!!!3!!!!!!!!:tounffi!!ll;00
� nstenn nn'UnirSalte
INS N�N� • �� lMf MI. •
ss lu �un.nn�INSnj i
i knnN,,ti I I An, %law
lif
At'
4iiif*: 410 '4;
; , •,,,, - 4,,,t , ",, . s
...... ..;....
'., , ,c,'",.-^...10,te.iie — *. '' 1.17' •.t.Le.
' . ”P'''..imrPre...4.. :4,....',-,..13,,,,,,,,n,fr
-:•-r.,..s...rr-ir r,T;
10 ' +1444.: .4 4 .......'''' 4"
..4 ',. , 0.4f .. i ,t .... .,,c.; • ]1 1 , .'-' ' i i ,
., ,... , +.° • ,.i. ,...i0i0,41, I,- • ,... , ' ..,.., . tr.,.
. ., 4 , (
r-:;-
, '. 0: ...,* .
*,,,‘,r ' ge. • 1 - —4 . - --44
.' ,,,,-,.., • ,t, —row - p, ,•
• • l'. ' ':1,17,. t' . , ' 2 ii t 1 - , • ' .„ ::: .1" • . • •
. •',. ' ' '. ' " ' ' '' ' .-, ' . - ' . ' '. w,t'''' -it-• ' „
. . . •
. . " ' ••• ' ' ' --, - 4 • • ' •I. .
• ;••
' V* "44•/:
'• "" 1. ' ' ' •-•*''' ' ' 0. t ; '?• ; ,', 1 i ',
; --
•
•
0
I qtr.'
14
T T T
pre of MA NW.
r • .11-21-ZIPL-T.--11—
/
I
1.6
• :, • .
" -
0•.•11, ••••1111.•'
ST ORM
11 3;
•••• .1•10
se
1 :
.,,,,,i 'f'"'";:•-'1'1,'
! , 4 , , , . ,. - !
,..,,,,,04 ........... I ti .,i. . *
>V; I tt li. i1,tt I It.
!, :-.,Inet::44pitr„:
T.,. ,--_711.1, .1.1•E ..,
....-.. IiIII=..711114!.__i...4,
ft;
'SA, '41t4i
Pt a f la- VI,-
al
an . 041PC • 10;:
jo. 4141C-:
:,41r•600
''"' 7.4 N.'
"61
1 ,yo
r a
c
•`• • • flfl
.10 OM .2.t.
I. HAROLD HOUSLEY
CONSULTING ENGINEERS
ASISCCIATION WITH
WILLOAN ASSOCVXTESz
woe
*).\
• , )
7 7
•
7 ,•77 777
4
e
4 it
•
• --a
I
,
;-;::1•,3•?:1 ;i7
; • '1:4
•,!?
I
\ el;
SS
1
MOM WO arms
•
N
1'
I/
0
1
MILES
LEGEND
SURFACE IMPROVEMENTS
REQUIRED FOR IMPLEMENTATION
OF MASI ER PLAN
OTHER DESIRABLE SURFACE •
DRAINAGE IMPROVEMENTS
MASTER PLAN OF DRAINAGE
CITY OF PALM DESERT
SURFACE
IMPROVEMENTS
FicIt..r,-Ar 7
1 11,: :4 tr. "ilit
VA
777
4.44roR,:a
!WIT i r • .. te'ti tint
CHAPTER 5
ESTIMATED COST OF MASTER PLAN IMPLEMENTATION
This chapter presents a summary of the estimated cost of implementing the comprehensive master plan
of local drainage presented in the previous chanter. The various drainage facilities are indicated by number,
and their rr.specirve costs are shown along with the total cost for each malty' drainage area
Additionally, Cost comparisons are made for the overall systems necessary to accommodate the 10-year,
25-year, and 50-year storm frequencies. respectively. Moreover, cost comparisons are provided for
several alto'natives to the recommended plan
5.1 Basis of Estimates
Tt,c estimated costs listed in the following tables are based on current (June, 19761 construction costs
for protects of similar nature and magnitude. It has been assumed that the master plan would be
implemented on an incremental basis as appropriator tundrnq becomes available and in accordance with
the priority schedule indicated in Table 4-2.
Sim? it 'is like's, that construction of the recommended facilities will be spread out over a number of
years. the totel cost of master plan implementation will be sliteect to future construction Cost rncreaSrs.
While no detailed effort has been made to protect future construction prices, some insight into the
probable magnitude can be gained through a review of histni..• trends in construction costs. Fixture 8
illustrates the recent history of two construction cost rndir es The first is the Construction Cost Index
published quarterly by Engineering News Record magazine (ENR).'This index is established w;inq as its •
base the construction costs prevalent in the year 1913. ENR's latest Construction Cost Index (June, •
1976) stands at 2,599. This compares with an index of 1,0"9 in June of 1966.
The second index illustrated in Figure 8 is the Cost Index for Concrete Pipelines compiled by the US.
Bureau of Reclamation. This index, published quarterly, is br°:ed on a 1967 index of 1.0. Its level, as
of April, 1976, was 1.91. The Bureau's index for concrete pipeline construction has shown a 7.9%
increase over the last 12 months, and since 1974 has shown a consistently higher rate of increase than
the ENR index of general construction.
On the basis of recent trends in the two indices, construction costs could be expected to double within
eight to fifteen years. Whether or not these inflationary tre'ids will continue is, of course, a matter
beyond the control of the City, It is recommended, however, that the funding programs established
for implementation of the master plan of drainage make provision for the increaard cost of deferred
Construction.
5.2 Estimated Project Costs
Table 5-1 summarizes the total estimated project costs for the proposed master plan system. These
costs include construction, engineering, administrative, legal, and financing costs. as well as a reasonable
factor for construction contingencies. The total project cost of the proposed master plan of drainage
is estimated to be 518,200,000. The project cost of conduit facilities is listed by drainage basing in
Table 5 2. The project cost for individual elements of the conduit system were previously pro stinted rn
Table 4,2.
-2S-
35OLL,
3000—
X
2500--
1-
o P
u o
;
O e)
; a
u
1500 -
4
3 t
11
O t000 -
U
•
2000--
0
•
1950
1
1980
YUAN
1 •1
1970
CONSTRUCT ION
COST INDICES
''-
ilit
,
—2.5
z
• Z
if
—2.0
I-
J q
u a ;
U
u. co
_1.5 • am
O U
3 C
• 0 4
v▪ . 03
_0.5
1980
I. HAROLD HOUSLEY
CONSULT ING ENGINEERS
IN ACOOCIATION WIT V4
WILLDAN ASSOCIATES
F
Conduit Systems
Surface Improvements
Contingencies Ila 10%
Right -of -Way Acquisition
Technical, Legal and
Administrative Costs
TABLE 51
ESTIMATED PROJECT COST OF
RECOMMENDED DRAINAGE PLAN
$ 9,300,000
4,300,000
$13,600,000
1,300,000
$14,900,000
300,000
$15, 200,000
3,000,000
TOTAL PROJECT COST $18.200,000
TABLE 5-2
ESTIMATED BASIN COSTS FOR
PROPOSED MASTER PLAN CONDUIT SYSTEM
Drainage Area Estimated
Designation
Cost
1.1 (SPL) $ 1,250,000
1-2 (P) 2,810,000
1-3 (SPB) 1,710,000
1-4 (M) 2,100,E
2-1 (TP) 1,030,000
2-2 (DC) 1,110,000
$ 7,870,000
$ 2,140,000
1,510,000
44 (8) 150,000
5 (1630,000
6 (1)
6 (PV) 300,000
TOTAL COST' $12,600,000
5.3 Project Costs of Conduit System for Various Storm Frequencies
In developing the master plan of drainage, alternative plans were developed to provide for conduit
systems adequate to convey flood water for storms of various ar frequencies. Table 5-3 compares the
prosect costs of conduit systems for 10-year, 25-ye
ttncudesconstruc'tion cost, contingencies, and right of way, technical, legal and adrninistrntive c,) ts.
_$o_
TABLE 5-3
COMPARISON OF PROJECT COSTS
OF CONDUIT SYSTEMS
FOR VARIOUS STORM FREQUENCIES
Storm Frequency Total Project Cost'
10-year
25-year
50-year
S 12,600,000
15,100,000
18,300,000
SA Cott of Alt rnetive Systems
The master plan study considered numerous alternatives to the recnrnmended facilities plan Among
tfv±9e! wrere•
(11 Multi -Frequency Alternative - This alternative would provide capacity in portions of
the drainae^ system for storms of 25 year and 50 ,, rear frequency In general, those
portions of the system located in the relatively flat rlownstreram anus northerly
of Highway 111 would be designed for the higher ,ntens.,ty st,,rms. Ten-year return
frequency design would be used in upstream areas where ,ten•per surface grades
dr, nrevalent, Total project Cost for conduit facie. t,,,., under this alternative is
$13.500,000.
(2) The Non -Diversion Alternative • Under this alternative, all runoff generated within .
the study area would be conveyed through the C,t,1's dramatic system ,to the
Whitewater Rtwr Stormwatr'r Ch.,nnel. The ,xna t•;lhcriv of haystack Road
would not be diverted to the Deep Canvon Stotnw,,,tr Channel, but would be
conveyed in a conduit northerly along Pi,riroa Av, ': ,e , leini the remainder of the
City's drainage system near Grapevine Street, This ,laere.ativ,° r,.quires that the
remainder of the downstream system be enlarger' " 1 pros ido capacity for the
additional service area. Total estimated protect c ( r for the conduits under the
non -diversion alternative is $14,000,000.
:3) Closed Conduit Alternative - This ,alternative cont„i.led the use of only closed
conduit (r.e., reinforced pipe and reinforced concn'fe box structur€,) for the
•conveyance of storm flow. Closed conduits would be substituted for those
reaches of the recommended plan which utilized open channels. Because of
the substantial difference in construction costs, this alternative ,s not feasible
without the use of a retarding basin along 44th Avenu.:: between San Pablo ,,, d
San Pasttial Avenues (Site 8). The total project c,,st for conduit system,: under
this alternative (including the retention basin) is $14,600,000
f4) Multiple Outlet Altes►r►ative • This alternative would consist entirely of cloud
conduits and would utilize an additional major d •,charge fine to the Wh,tewater
River $tarnwater Channel. Conduits would exteed to fie r,v ., along bath F', r tr t;a
and San Pablo Avenues. The' primary advantage of this alternative as that the
downstream portions of the conduit systems are upa' lied and could thus be
constructed independently. This advantage in the ability to phase the tarujer t
construction is offset by the substantially higher 'project cost Total pr„ject Lost
for this aftc'native as estimated :a be $14.700,000,
*includes constriction ant, contingencies, and right of way, technical, Irr'el and 'ad+han,, 1r.711,,•
—31—
r
TEAM 5-4 compares the total project costs of the various alt^rnative plans:
TABLE 5-4
SUMMARY OF COSTS FOR ALTERNATIVE CONDUIT SYSTEMS
Alternative Total Project Costa
10-Year System (Proposed System) $12,600,000
25-Year System 15,100.000
50-Year System 18,300,000
Multi -Frequency System 13,500,000
Non -Diversion System 14,000,000
Closed -Conduit System
(with Retarding Basin) 14,600,000
Multi -le Outlet System 14,700,000
5.5 Required Surface Improvements
The cost of curb, of•r•er, and street work necessary to the proper functioning of the drainage system
is summarized in Table 5-5. These costs are for the construction of these facilities Shown as being essential
to the drainage plan.
Construction costs include o-inch and 8-inch concrete curb and gutter, widening of the traveled roadway
in ultimate wirtth of from 3C to 40 feet, resurfacing with asphaltic t.uncrete pavement, and allowances
for curb depressions, driveway anrons and cross gutters, Project costs are based on current construction
prices end inctude allowances for technical, legal, and administrative services.
TABLE 5-5
ESTIMATED COST OF
REQUIRED SURFACE IMPROVEMENTS
Construction Cost
Contingencies @ 10%
Technical, Legal, and Administrative
Services
S 4,300,000
400,000
S 4,700,000
900,000
TOTAL S 5,600,000
'Costs sve for conduit systems only and do not in6ude surface improvements.
-32-
FUNDING METHODS
An essential requirement for the implementation of the master plan of drainage is a sound funding
program. Once the master plan is adopted, positive steps must be taken to assure that adequate
mvi'ies will be available to construct the required facilities. The following discussion outlines a number
of possible financing methods. Many of these are commonly known and relatively simple, and
vans+equentty have been discussed only briefly. More lengthy narratives have been devoted to those
methods which appear most appropriate for the City Of f'atm Desert or which are not in common
usage now.
It Is evident that no single financing mi thod will be sufficient to provide the funding necessary to
implement the master plan of drainage. It is recorimr'nd d ih.it the City consider the various
combinations of financing method• rn implerrent,ng nrograrn.
el Genera) Fund
One source of funds iaihich can legally be used for drainage facility construction is the City's General
Fund. However, since this is a limited source of revenue, the tremendous demands for funding for
other services usually places construction of drainage facilities below more immediate priorities.
62 Drainage Fees
Under the provisions of the government code of the Slate of California, a local governmental agency
may adopt a program for the collection of drainage l01•.. The Sub -division Map Act enables the City
to enact the drainage fee program after certain prerequisites have been satisfied. The rectuirements for
the drainage fee program include:
(1) Adoption of a master drainage plan for ear li local drainage area.
• (2) Certification of the master drainage plan by the legislative body of the
County and/or speiiat distr,ct haying a Co ;n`ywi.iF' and/or districtwide
drainage plan.
(3) Adoption Of a fee structure based on the .:o>t of the required
facilities for each drainage area and equitably proportioned to
all affected properties.
(4) Establishment of local drainage facilities fund.
Following adoption of appropriate local ordinainxs, fc,ca can be collected from developers
a5 a condition of approval of final subdivision maps, Funds are then deposited in the appropriate
"local drainage facilities fund." They may then be emended for engineering, administrative, and
construction costs of drainage facilities to be constructed within a particular drainage nrc.a.
In the case of the City of Palm Desert, a drainage fee program within the study area would he of
. )mewtwt limited benefit in that so much of the area where drainage facilities are required has
already been developed. However, the selective applr:•,ation of this program to urrievelnid site,
within the study area and to additional areas as they are annexed to the City should be considered
along with other financing alternatives. Table 6-1 presents an estimate of potentialliv i iiilec:t'a!ile
drainage fees.
--33—
TABLE 6-1
POTENTIALLY COLLECTABLE
DRAINAGE FEES
Drainrge Percentage Total Cost Reimbursable
Arse Undeveloped Cost by Dovelopan
1 15% $ 7,870,000 $ 1,180,000
2 35% 2,140,000 750,000
3 45% 1,510,000 670,000
4 0% 150,000 —0-
5 65% 630,000 400,000
6 0% 300,000 —0—
$ 12.600.r' y) $ 3,000,000
8.3 Federal Revenue Sharing
The City e nrrenily receives a certain amount of funds thro!,'j ,he Feder rI Revenue Sharing Program.
The life of thjs program is subject tr, political consideration', and corn be terminated at any time prior
to the next fiscal year. Thus, any programs which are deoe, rfant upon this source of funds for their
continued operation generally receive low priority because of the ongoing funding requirements which
may not he met if the Revenue Sharing Program were terra r ated
The construction of a project ,n the master drainage plan would be a logical application of revenue
sharing funds provided that individual drainage system elements can be constructed within a given budget
year and be functional without dependence on cor.;;nued funding in order for the element to provide
benefit to the community. It is, therefore, recommended that this source of revenue, to the extent that
the procram is continued by the Federal Government. be rori;,dered for the implementation of the
master drainage plan facilities.
6.4 Federal Housing and Community Development Act of 1974
The Housing and Community Development Act of 1974 provides for Federal grant funds for community
development programs. Storm drains are among projects eligible for funning under this program. For the
fiscal year 1975-1976, the City of Palm Desert received planning grant funds under the Urban Counties'
Grant Program through joint application with the County of Riverside. A portion of these funds were
used to finance this master plan study.
Construction.grent funds under HCDA could be used to irrpleinent portions'of the master plan of
drainage, provided that the City can demonstrate that construction of such facilities are part of a program
designed to meet community development needs and objectives and to provide for a new or continued
supply of housing for low and moderate income families:
In applying for HCDA funds, the City can determine annually, at its option, to either'.
(1) File a joint application with the County of Riverside under the Urban Counties
Program; or
(?t File an independent application to compete for monies from HCDA's discretionary
fund.
—34—
•
roe
ih
In either Civics the City must demonstrate that funding assistance for storm drain facilities is not available
from other f adi•raI programs. Since no other Federal agency programs presently provide assistance for
rlr,ana+ele! faCtlitic'S, it would appear that the HCDA program has some potential as a source of funding
for drainage facilities in some parts of the City. If HCDA funding is received the City will be required to
establish a housing assistance program. Similar programs have been successfully implemented throughout
the nation including such local communities as Pam Springs and Beverly Hills.
8.5 Redevelopment Agency Funds
The City of Palm Desert has established a Community Redevelopment Agency. The project area .for the
Redevelopment Agency is generally centered along State Highway 111 and includes the bulk of
commercial development within the City. Properties within the Redevelopment Agency's project areas
should be provided with adequate drainage facilities ; as redevelopment occurs or as an incentive to
redevelopment. Redevelopment Agency funds can also he used outside of the specific project areas providing
that it can bee demonstrated that the construction of off -site facilities will benefit the redevelopment area.
it is recommended that i,'rrous consideration tn' yrven to tfk' use of •Redevelopment Agency funds free
those facilities within the Agency area and those off -site far shire„; witch would directly tly bctiefit the •
redtvelettmrsnt prole, t .area
6.6 Argent Districts
Assessment district proceedings offer a variety e,f mcthiids of financing storm drain systems under the Acts
of 1911, 1913, 1915. or other assessment proceedings, AS'4',•.ment district iinancing could present a
.•:able alternative for local drainage areas, partii Oterty those which are substantially 'developed. However,
since the cost of administering a•;.ussreent distri: t'. is higher than other financing programs and is subject
to protest from landowners within Viet districts. it is recommended that a preliminary evaluation of
property -owner acceptance be made prim to initiating proceedings.
The procedures of the 1911 Act and 1915 Act are generally similar except for the means by which the
assessment district bonds are secured Under the 1911 Art, bonds are secured by liens on specific parcels
within the district white the 1915 Act bolds .arts secured by collective bens on the entire area of the
district Delinquencies under the 1911 procedures result in individual foreclosures where the 1915 Act
authorizes the City to levy a limited tax on all t roper ty within the City to ccvre delinquencies.
6.7 Highway 1 t Projects
Certain of the proposed drainages improvement projects are closely related to Highway 111, The ost of
these improvements may be at least partially fi;' dablc by the State of California through the general ,late
road system program. One major provision wo;ilil be that such drainage element,; render• the highway
free from excess flooding during major storms. Proposed improvements to Highway 111 or other States
hrghways should be coordinated to include ptovisior's for implementing eernent'• of the master p;an of
drainage.
Another source of possible funding for at least a portion of necessary storm drain fac;ihties If' gas tax
monies which come directly to the Crty and which may he used for selected drainage facilities. All
proposed highway projects should be carefully reviewed with regard to the po'r 'brlity of incc , rape iti'sq•
portions of the storm drain system an their des; gn.
IA Service of Coverage Charges
A potential source of revenue which ha:, been considered in some cities is either an are . 7e „argr f. ,r e,!htar
drainage service or a charge br,sed on coverage of land with impervious surfaces.
,5—
I
The first apa'roach would involve collerlion of a monthly drainage service charge for each property in
the City. Drainage districts would be established, and charges would be based on the cost of providing
adequate drainage facilities for each particular district. Funds collected from the service charge would
be used only for the planning, design, and construction of drainage facilities, Service charge revenue could
be used on a pay-as•you-go basis or pledged as income for support of a revenue bond issue. This type of
Program aPpears to offer an attractive alternative to assessment district proceedings in areas where
substantial development has already occurred.
The coverage charge concept would apply a similar monthly charge_ to properties within the various drainage
districts. ►l+wVever, in this case, rather than proportioning charges on an acreage basis, charges would be
imposed on the basis of the area covered with structures, pavurg, or tither impervious surfaces. Where
improvements already exist on the property, the actual covervte would be utilized in the computation
of the monthly charge In thn,e cases where no improvements exist, the charge would be based on an
estir^lte of Probable ultimate coveragr While the coverage approach is theoretically more equitable than
the service e:harge, it has certain inherent administrative disadvantages which would complicate its
implementation
Although existing law may rut provide for service or coverage charges, the City may find the concept of
siaffiaent value to warrar r nersurt of enabling legrshition. It r- •,ugge',ted that the City Engineer and the
City Ateir:rrey investigate the potential for developing this t tie of revenue program.
8.9 Combinations of Funding Methods
As indicated earlier, no signle financing method is likely to b' sufficient to provide the funding necessary
to implement the Master Plan of Drainage. Of the several methods reviewed previously, it appears that
the following are the most likely sources of revenue
(1) Drainage Fees
(2) Redevelopment Agency funds
• (3) Assessment Districts
(al General Obligation bonds
It is also possible that monies from the City's General Fund allocated to its Capital Improvement Program
could be used to construct some of the necessary drainage f 3cilitrrts. Funds from the Federal Housing
and Community Development Act Program could probably be used to construct a portion of the
recommended system.
Although a detailed financial plan is far beyond the scope of the work covered in this report, an
attempt has been made to illustrate possible methods of funding the required drainage facilities. Developing
an actual funding program for a project of this magnitude will, of course, require detailed fir,cal planning
• and the establishment of the drainage system's priority with respect to other municipal programs. Tebie
62 presents one of an almost limitless number of possible, funding programs.
'YIPS+^�,.,:'. ��':'4.. �s:;'a}�-.�ies::�ww�S"+!'. ki"'�Af e,,.'p ^t`s�d a'�.e.'�"'l 'V�.••,i
•
Source
Drainage Fees
Redevelopment Agency
Assessment Districts
General Oblig. Bond',
CL, .tal lmnprov. Program
HCDA l unds
TOTALS
TABLE 6-2
POSSIBLE FUNDING SOURCES
FOR REQUIRED DRAINAGE FACILITIES
Conduits
Cost of Facilities
Surface
Total
$ 3,000,000 — $ 3,000,000
2.700,000 $ :300,000 3,000,000
1,450,000 3,900,000 5,350,000
5,4 50,000 — 5,450,000
1,000.000 1.000,000
400,000 400,000
$12.f,rrO.W $r• r,()0,000 $18,200,000
It should be noted that this $3 million In potentially collectible drainage fees can only become available
as development occu-s on presently undeveloped lands. Thin, it could be a considerable period of time
before this money is available for actual constructton of facilities. Monies shown as being available
from the City's Capital Improvement Program or from the Federal Housing and Community
Development Act have been based on the assumption that sin h funds would become available over a
period of yr For example, tl,e current year's allocation of HCDA hinds has been budgeted for street
improvement projects. Table 6-2 assumes aporoxirnately $ ').O00 eri H'DA funds could be alloc-ated to
drainage related street emprovertwnts over a five veear per 'nil.
It is al:n assumed that an annual budget of $200,000 coull t>e et,tabli,hed for drainage !elated surface
street improvements under the City's Capital Improvement P rgr,rrn,
While drainage fees, federal grant funds and general City revenue", could pos<.ibly account for $4,400,000
in drainage system funding, these sources of financing would take several years to generate. Drainage fees,
for ex,emple, may be collected from developments as they occur hut must be placed in accounts
specifically designated for facilities to serve the drainage b;e•in ire wh'th the development is located.
The tuning of development projects is largely beyond the ; ontro( of the City and thus the a,,iit;+hility
of funds from this source is by no means assured.
More immediate sources of funding include the City's Rt,ie veloprnent Agency, assessment di ,'riot
proceedings and the issuance of General Obligation Bonds It has been assumed that Rode:velot)rner+t
Agency funds could be applied to those drainage facilities ev,thin the boundaries of Project Area No 1
3s well as to a •proportional share of the cost of downstream facilities carrying water from they
Redevelopment Agency area. The annual tax increments anticipated from Project Arc,i No. 1 appear to
be sufficient to support a Redevelopment Agency bond issue considerably in excess of $3 million.
Assessment district financing could he used to fund those drainage improvements required in already
develnped areas of the City. The estimated cost of improvements which could be appropriately fin:need
in this manner is S5,350,000. About three fourths of this arnount would be applied to rer oo` truchon
of streets, with the rernainder being used for construction of underground conduits.
Based on the foregoing, it would appear that unless other funding sources are found (e.g. new federal
grant programs) one-third or more of the total project costs have to be financed through soma gerneritt
revenue measure. The most likely source nt such funds would be the General Obligation Bonds,
Table 3-2 assumes that approximately $5.4 million would be funded using General Qtligition 13ne ef'
—37—
•
•
41
f •
4
wirt:1!T. TT'),1,1
' •
--• • • • •
101' ffq. F
4 ,
The clistrihutr• 0 herding ',turf OM in Table 6-2 is but one of a nearly infinite number of financing
(.0moevjtiuns ii,r1 could b' di-/Oopel in support of the Matter Plan of Drainage. It Is recommended
that the Clry ervege the rivi-es of firancia1 CtIngUltRni lo develop specific funding programs for
the itripletrentwion of Me Plan of Drainage.
-34
MASTER PLAN OF DRAINAGE
FOR THE CITY OF PALM DESERT
Appendix A
Runoff Coefficients for Soil Groups
The runoff coefficient (C) varies with respect to the perce.ntag.i of impervious area and the coefficient
of runoff for undeveloped land (CA 1. The value of CA relates to rainfall intensity and soil type. Figure
A 1 shows the relationship of thew factors for the soil types r.ommon to the Palm Desert area.
The curves rn Figure A.1 ere representative of U S Soils Conservation Service Hydrologic Soils Groups
A and B. Figure A 2 defines the approximate limits of the two hydrologic soils groups within the
Study area.
Appendix B
Floods of September. 1976
Suhseguent to the completion to the final draft of the Ma•.tr'r Plan of Drauiaue, the City of Palm
D art was struck by a disasterous flood.
In September, 1976 properties in the City of Palm D re'rt per on' ced heavy darn rj from floods
resulting from the tropical storms. The first of thew, tropical storm "Kathleen," depornrd mere than
3 inches of rainfall on Palm Desert in less than 24 her„rs. Even heavier rainfall occurred in the
mour•:rinous areas to the south of the City.
the heavy runoff from the mountarr• ,any ,cis brea, r d the Dead Indian Canyon dike intended to
peetect the southerly flank of the City, and widespread damage occurred. Riverside end Imperial
Counties were declared disaster areas by the President of the United States and damage from the
storm in the Palm Desert area was esnmated to be in excess of $20 million. Thirteen days after
tropical storm Kathleen another malnr rain storm hit the City causing still more fluwiiert ,red
property damage.
Tropical Storm KetlthMen
Rainfall from tropical storm Kathleen began falling .luring the evening of September 9, 1976.
Relatively intense rainfall continued throughout the evening and into the afternoon of September
loth. Runoff from Carrizo, Grapevine, Dead Indian and Ebhans Creeks, is well as from the
numerous smaller canyorn in the vicinity, conunrgerf eear State Highway 74 topping the road near
the bridges for Dead Indian and Carrizo Creeks. Fair a per e,d of time the water Continued northew:1r'r1y
along tho base of the mountains. However, sometime .after noon a diversion dike at the mouth of
Deed Indian Canyon failed. A wall of water estimated to be several feet high began flawing
northerly toward Dead Indian Carryon d:veesron dile? lust south of Portnl,t Avenue and east ref
Highway 74. The water struck and breached Dead 1 tdian Canyon Dike at two. IUr:.atran; awerr,t
hundred feet easterly of Highway 74.
A wake Of water several feet in height and hr ndreds of feet in width continued racueg northeasterly
towerds.the urbanized area of Palm Desert. The result was catastrophic. Upon reaching ^,•hi.ev,ator
River stormwater channel the main body of water had widened nearly a mite, leaving a Wake of
destruction and damage.
Figure B•1 presents an aerial view r.,f the City. It shows graphically the path of flord waters from 'he •
rrzauntainoua areas srjutherty of the City.
39—
i
J
TYPR ~PD-is"
Note
t he data st.t'wn hereon represents the
most rchabie ,ntormaKm ava'teble at the
time of the -aster plan study The data rs.
however, sublet, to revs on and the
reader .s a ,toned to consult with
appronr•' rgenc.es prior 'o ‘rutut ng
nesron ^r lacrlrties
• •
RAINP*$ L INT•NIBITY
IN INCHUS PUN NOUR
•
•
RUNOFF COEFFICIENT CURVES
(C^ vs I)
1. HAROLD HOUSLEY
CONSUL1'INO ENGINEERS
IN p.••OCIATION \jtToe
WILLDAN ASSOCIATES-�
1
•
6
0
9
9
lt
1•1'1.
'
i!
a '
' I
4
•
• .Y.." 11/4,
Th
I ` 11 rh-.0,1 he, ttrel I thit
iP)11/b� r?ijr'l%tIOfl pve.tablit st the
1.,41{Alhe mast., Dien lit.rAy The date Pl.
how'' SirIpPCI. ritiorir, Pod
ege14.• cOnsult with
approry PIP 11,3., prior I., in.lorling
des.gn er,Ither
.,„
••
re'N-7;
HN'OrIOL.C.0-C2,
Tyr
V" •
I
•
r
Yi
e `�Iry t�V1i�'F �j 'III
I, NNi t �ii
01
A third breach in the Deed Indian Canyon dike occurred near its easterly end, southeasterly of
ironwood Country Club in Deep Canyon. As a result, the area ir-unediatety around the clubhouse
became en island end a number of people were temporarily stranded. Damage to the golf course
was extensive.
During this period stormwater also topped the Palm Valley Stormwater Channel. Flood waters left the
confinement of the channel in at least two locations southerly 01 Hedgehog Street and flowed
northerly re-entering the Palm Valley Stormwater Channel on the south side of Highway 111. Extensive
damage occurred to both public and private property as a result of this breach.
The photographs on the following page's (Figures 8.2 ihrrwgh B-10) illustrate the damage which resulted
from tropical storm Kathleen.
Storm of September 23rd
Tropical storm Kathleen was followed thirteen days later by another storm of very high intensity which
re•,uttrd in an estimated S90(1.C:., in damage The 4', tent of the d.rmage was intensified as a result of
the atteretfects of tropical storm Kathleen. A layer of sill had been deposited in many areas, reducing
tole percolation rate and thus increw,trig the arnooro „ f rieiiitf. 1 he water readily followed than path of
'erosion caused by tropical storm Kathleen ar,r1 numerous hnrnr•s were again fio,uir'd and damaged.
Effect of the Master Plan System
It is important to recognise that the drainage systee• pror,,sed in this Master Plan of Drainage would
not have been adegua:e to protect the City of Palm ;}P°r r+. from the storm flows resulting from
Trof:icat Storm Kathleen. The system proposed in this report is designed to provide only for drainage
of storm water originating within the dike systems + the Coar.hella Valley County Water District
fCVCWD). The vast majority of the damage which car currnd a: a result of tropical storm Kathleen was
Attributable to storm water generated outside of ti ri perrrnr'ter formed by these, dikes. •
The runoff from the storm of September 23rd was, however, almost entirely the result of rainfall'
occurring with the CVCWD dike.system. Had the drainage system proper,ed in the M;i stir Plarr been
in place and operative, the damage would, in all 1/ketrhorxf, have been negligible
Appendix C
Rainfan Intensity
Hydrologic computations used in the master plan study are based upon the Riverside County Flood
Control Drstrrct's rarntall intensity/duration Curves f.-r the Palm Springs area. These intensity/duration
relationships are shown in Figure C-1
—42—
mt.
.•
'••• .'," : /;;;;•'/,i, 4/:
/''•• 1H,.f
- ,
4•••
;,! • 4
' 4-11P-•*_
•
,,I,,eqmo•
„.•
3
FR:JURE B 1 AI /"1,r.- A
Th'2 path toll •••••, h‘v t!t, w rs.;')/f` ' C,1` • t; VAiley
C•Inty Wah••• rh•••trit,t'•, t,, r,r- , • !fj
flr,t?`11
1C1..)!•!-. Vti-V`.' r1•Jr.;
STATE :••11,,,i4V'/AY
— 43—
If)
,*7
1:1
t.:11
•',,,,,,,..„-.),,,,dyft, ''' ''' ' ;/•/`;',,,Y;;,,/''''''.,i1.;;;; '///,,'„' 1••,;k4.4/44-_9;10 '_-/' /: '4// ''''''/-: ,,: •'''/// //''''''''''' /4''''•-',4.•417-4,. :// •,•;•• ''',/‘ V//" ' '
• - ,.. . , • • -• _ .• . • , ,
. ,
'i fC nr,
,
FIGURE q 3 VIFtti LO01,.IN0 NORTH .`N Sf“N LUIS REY rROM
STATE }-41GOVVAY 111.
F IGUPE Ei 1. VI(tity' LOOKING WET AL(/ G WE r9' 11`',Er!.'ti,
S;OE OF STATE: FllGi'WAY 111 Ft< .M SL:4 LAHr
" `"- r ram—
Fre
•
4
4
' •"1111, 'illrgrif.f.'1-',,-' r•fr•re,rr.-, ,..,
')i • ' ',, ', (. ',
•
re.10,11
e-eqte ereo•er ere::
'
Ft,
Tr-1'PICAL Si
7_0;....
. .
-,'. ,!•:,„ i ,..i.,.. . 1 . 4,,',.'i; j'yt.,i1, .
- i
. 1 '
';, i'-, i V,i,'retexteekre r,'ri ' e ,,1 —r .1.., r , • °•;',errir.qiirlfle;.:
r
',err
, .
wLOOk it: ;
t 4
' ,4, g,0011* 4116,, tt"tt
`-,,:rfec,r,prr
- -
. -
t't
E111,• DA,' A,P, r
.,'",r.leVtir,74,,erle;e!r.feF', '4'4'174 " F
• r,
"F.
:•
•
, 31, •
441 L
r
• i ' - . .
„;4., • e.'!"' ' 7"- . .
':t4' .'". • 4,
11,-, ir:: ,.:•r„ .,.., ,,r,-,.. ,, . - __,,, ,. ...,. .,,,.,,,i, ,; ,. , ..; ,,-- '::"-,7,-- ' . , -.„,,,,,i,........„..,.
e.,,
' IGURE i'. q Nil i '‘%' I. '..pr..IV..! . Al '.1 Al f.-... • . TH1 t 'f ,, 1 HERLY
• !ADE OF Hi(,11AY 111,
•
•
.47
01' yryfrel..ler tet117-1 It '- 1 f ir.
1C -
5 "
4
1
II 1
2
a
or
03
1
1
1
I
iI 11
1
I 1
3 4 5
Note The data shown hereon represent* the
most reltahle tntofmation ava.labie at the
time of the Metter plen study The Bite ts,
however sottotct to rpvtiol,f1 nd the
reader ts ceuttoned to conttott wrth
sop, opnsta egfpnoes ono, to Indtattng
design of spec,ft,-, tec,ittwtt
, .
___i__I L - ._,.. i
4. 4' —
1-1 l. — -- —
11 -1 1 I 1
20 30 40 50 100
10
DURATION
IN
RAINFALL INTENSITY / DURATION CURVES
I. HAROLD HOUSLEY
CON9ULT1403 F NOINE r.
IN AMMO A'T /ON NV ITN
WILLMAN ASSOCIATES
Preliminary Investigation
Of Assessment Proceedings
For Flood Hazard Correction
For The City of Palm Desert
Willdan Associates • F. Mackenzie Brown
Miller & Schroeder Municipals,Inc.
Clayson, Rothrock & Mann
F. MACKENZIE BROWN
INCORPORATED
(7 1 4 1 7 5 2- 9 0 2 5
(213) 489-5006
October 29, 1979
City Council
CITY OF PALM DESERT
45-275 Prickly Pear Lane
Palm Desert, CA 92260
Re: DRAINAGE FINANCING STUDY
Gentlemen:
160C DC.E STREET SU.-E I:C
NEWFORT PEACH. CAL:FOR N:A 92E50
Pursuant to your prior request, enclosed herein find joint
venture study and report that has been prepared to assist
the City in analyzing the financial alternates available
for financing certain drainage improvements to correct
drainage problems and needs of the City, with special
emphasis on the ramifications involved in pursuing a
special assessment district.
Any of the involved consultants will be happy to meet with
you and the City Staff, or be in attendance at a Council
meeting, as so desired by the City Council.
Please so -Advise.
Very truly yours,
F. MACKENZIE BROWN
FMB:jlm
Enclosures
cc: Mr. William Stookey
Mr. Michael Whipple
Mr. Eugene Nazarek
Mr. Robert Spellman
TABLE OF CONTENTS
ARTICLE I:
Introductory Remarks and Summary.
[F. Mackenzie Brown]
ARTICLE II:
Preliminary Investigation of Assessment
Proceedings for Flood Hazard Protection
[Willdan Associates]
ARTICLE III:
Drainage Assessment Districts and The Law
[F. Mackenzie Brown]
ARTICLE IV:
Alternative Financing Methods for Flood
Hazard Correction and Recommendations
[Miller & Schroeder Municipals, Inc.]
ARTICLE V:
State and Federal Funding and Legislation
[Eugene Nazarek of Clayson, Rothrock & Mann]
GENERAL SUMMARY
The material enclosed herein is submitted by a joint venture
consisting of the following persons:
a. F. Mackenzie Browu;
b. William Stookey of Willdan Associates;
c. Michael Whipple of Miller & Schroeder
Municipals, Inc.;
d. Eugene Nazarek of Clayson, Rothrock & Mann.
The purpose of this joint venture study was to attempt,
through independent sources, to make information available to
the City relating to the engineering, legal, and financial matters
concerning the possible implementation of a plan to correct the
drainage problems which exist today in the City of Palm Desert.
Willdan Associates did an update as to the costs involved
to solve both the on -site as well as the off -site problem, and made
a general analysis as to what would be the appropriate method and
spread for any assessment district proceedings.
I then, F. Mackenzie Brown, attempted to point out the
procedural problems and fiscal impact that could result from an
assessment district, as well as outlining certain of the court's
concerns [which are pointed out in a 1975 California Appellate
Court decision, Harrison v. County Board of Supervisors].
Thirdly, Mr. Whipple covered the various financing tools that
could be used, or in combination could be used, for implementing a
program for funding the drainage improvements, together with his
conclusions and recommendations, which should be carefully studied
by the City Council.
Lastly, Mr. Nazarek researched the possibility of State
and/or Federal funding which may be available, together with the
possibility of implementing legislation to help assist the City
in establishing a program.
An analysis of the alternates available would generally be
as follows:
1. Assessment District. The assessment statutes authorize
the construction of the drainage improvements; however, one must
be aware of the Harrison decision [Drainage Assessment Districts
and the Law, Article III], as well as the possibility of expending
a substantial sum of money for engineering, without any guarantee
that the project would proceed. The assessment district, in its
proposed state, is very large and, thus, the program, if it is to
be considered, should definitely be implemented by other sources
of funds, either as a contribution up front or as a contribution
against the annual debt service schedules. This most likely would
have to come from tax increment funds from the existing Redevelopment
Agency, or from a modification to said Agency.
Because of the substantial cost for engineering, there are
two possibilities for consideration relating to the possible
implementation of an assessment program.
a. Debt Report. As I previously indicated, in order to
initiate the proceedings, it would be necessary for the City
Council to consider the preparation of a debt report, which
basically would cost approximately twenty-five thousand dollars
(25,000.00). This would then result in a Public Hearing, with
all property owners being advised as to what would be their exact
dollar individual assessment. Upon the conclusion of that Public
Hearing, though there is still no guarantee the proceedings would
go forward and, still, upon the completion of the engineering,
there would be the necessity for the Public Hearing, under the
provisions of the "1913 Act".
b. Advisory Election. The City Council could consider at
this time placing a matter on the ballot as an advisory measure
as to whether or not the City should at this time proceed with
the formation of a special assessment district. The advisory
ballot could also be worded in such a way to request an opinion
as to whether or not the City should proceed with either an
assessment district or possibly a general obligation bond issue
through an ad valorem tax levy if and when such a tax override
would again be authorized.
2. General Obligation Bond. As we previously discussed,
since the passage of Constitutional Amendment, Article 13A, the
conventional type of general obligation bond is no longer available,
inasmuch as the ad valorem tax override power has, for all purposes,
been eliminated. As Mr. Whipple outlines, if Constitutional
Amendment SCA 26 is approved by the electorate [June, 1980], that
vehicle would, again, become a viable tool and most likely the
most logical and feasible way to finance the improvements. The
City could consider an election for a general obligation bond issue
at this time, subject to the passage of SCA 26 but, again, the
general obligation bond issue could not finance the entire
obligation because of the bond debt limit as it relates to the
City's assessed valuation [Miller & Schroeder Municipals, Inc.].
3. Redevelopment Agency. The drainage problem surely would
qualify as a blighted condition, but the existing Redevelopment
Agency cannot provide adequate revenue through tax increment or
tax allocation bonds to support the entire program. Certainly,
tax increment from the existing district, or a modified district,
should be considered as one source of contribution funds to the
problem.
Please review the date enclosed herein. Any of the
participants in this joint venture report will be happy to meet
with you for further consideration, upon your request, at the
next most convenient meeting of the Ci y Council.
RqApAc>tf flly submitted,
(r;
EN BRO
General Situation
The solution to the Palm Desert drainage situation will involve two distinct
and separate major drainage systems. For the purpose of this discussion,
these will be referred to as "offsite" and "onsite" systems.
The onsite system might appropriately be described as those proposed
drainage facilities set forth in the Master Plan of Drainage prepared by
Willdan Associates which depicts proposed drainage facilities, generally
within the corporate boundaries of the city of Palm Desert, and lying
southerly of the Whitewater River. Under the final plan, this system
essentially will collect only those waters that fall upon the city of Palm
Desert below the proposed interceptor works for the mountain ravines
having drainage tributary to the city area. The estimated cost to accom-
plish these facilities at current prices is $32, 176, 000.00.
The offsite facilities may best be described as those protective works
needed to provide protection from runoff originating in the mountains
along the southerly side of the Coachella Valley. Several conceptual
alternates for the accomplishment of these works have been set forth
in studies prepared by Bechtel, Inc. The Bechtel studies were primarily
for conceptual and comparative purposes and were somewhat general in
nature, not involving detailed engineering. As a result, the cost estimates
set forth in that report will need additional refinement. However, recog-
nizing these limitations, a cost of $14 million at 1979 prices is the estimated
cost of the proposed offsite improvements.
Onsite Drainage System
The onsite drainage system identified in the city's Master Plan of Drainage
for this portion of Palm Desert essentially consists of two parts. One part
includes a system of channels and underground storm drains to carry
storm runoff from the city streets to disposal points at the Whitewater
River. The other part includes street improvements consisting of curbs
and gutters to collect storm runoff in the streets and direct the flow to
catch basins and other points of interception. A system of storm drains
without the street improvements will not function. Without curbs and
gutters, storm runoff will continue as uncontrolled overland sheet flow
in most areas of the city.
The proposed onsite storm drain improvements would include two trunk
channels extending southerly from the Whitewater River with a system of
underground lateral storm drains in various streets extending upstream
eventually to Haystack Road. Southerly of Haystack Road, another system
of underground storm drains would extend from the Deep Canyon Channel
to drain the area between Haystack Road and the city's southerly boundary.
The Master Plan of Drainage identifies the existing uncurbed streets that
need to be improved in order to collect and carry storm runoff to the storm
drain system. The Master Plan also provides recommended priorities for
construction of the storm drain improvements in order that a logical con-
struction program can be undertaken to provide onsite flood protection.
Generally, the highest priority improvements include downstream trunk
facilities, with other priorities based on the extent of existing development
and the degree of danger due to flooding.
The entire onsite drainage system would be located within the boundaries
of Palm Desert southerly of the Whitewater River and easterly of the Palm
Valley Channel. The onsite system would provide flood protection from
a 10-year storm falling on the city. The onsite system would not provide
flood protection from offsite runoff entering the city from the upstream
canyons.
Offsite Drainage System
The proposed offsite drainage system needed to protect Palm Desert from
storm flows originating in the mountains southerly of the city is based on
a modified version of one of the concepts presented in the Bechtel report.
The drainage improvements for "Alternate 1A Modified" would include a
substantial enlargement of the entire Palm Valley Channel through Palm
Desert, together with construction of a new diversion channel to carry
storm runoff from Dead Indian Creek and Carrizo Creek to the Palm Valley
Channel. A series of debris basins would also be constructed at several
upstream locations with this alternate.
The Palm Valley Channel generally extends through the city of Palm Desert
near the westerly city boundary and passes through a portion of the city
of Rancho Mirage before reaching the Whitewater River. The channel is
located at the base of the mountainous terrain along the city's westerly
boundary, and presently carries runoff from the Cat Creek watershed
through Palm Desert to the Whitewater River. The Palm Valley Channel
is a relatively shallow earthen ditch with a graded sand dike forming its
easterly side. It was this channel that recently failed in July, 1979,
resulting in flood damage to many homes in this portion of the city.
Alternate 1A Modified would divert runoff from Dead Indian Creek and
Carrizo Creek to the Palm Valley Channel. Presently these streams flow
to the Deep Canyon Channel which extends in a northeasterly direction
across Palm Desert near the city's southerly boundary and passes through
the city of Indian Wells to the Whitewater River. Dead Indian Creek and
Carrizo Creek join near Highway 74, and the runoff from these streams
is contained by an earthen dike along its northerly side as it crosses
through Palm Desert. During the Kathleen storm of 1976, debris from
these watersheds filled the stream bed which caused the stormwater to
overflow the dike and eventually resulted in the failure of a secondary
protective dike and caused severe flooding in large areas of the city.
The proposed diversion of Dead Indian Creek and Carrizo Creek to the
Palm Valley Channel would result in much larger flows in this channel,
and would require that the channel be enlarged to handle the increased
flows. The proposed improvements for the Palm Valley Channel would
include widening and deepening the channel together with construction
of permanent slope lining and drop structures. With this alternate, no
improvements would be required for the Deep Canyon Channel within
the city limits of Palm Desert other than the improvements presently
under construction near the Living Desert Reserve in connection with
a large housing development just downstream in the city of Indian Wells.
The cities of Palm Desert and Indian Wells, together with the Coachella
Valley County Water District (CVCWD) , have prepared a Memorandum of
Understanding in which each party agrees that Alternate 1A Modified is
the offsite flood control plan to be utilized for protection of the cities of
Palm Desert and Indian Wells. According to the Memorandum of Under-
standing, CVCWD will be responsible for implementing the plan.
Assessment District Considerations
The following discussion is based upon the assumption that all or part
of the proposed improvements described above would be installed by
assessment district proceedings, presumably under the "1913 Act".
Proceeding on the assumption that such a district would include only
properties within the corporate limits of the city of Palm Desert, the
district boundaries then would be limited to that area southerly of the
Whitewater River. It may, in the final analysis, include those properties
westerly of the Palm Valley Channel, but it is recognized that those pro-
perties have limited benefit from the project.
Previous storms have afflicted different degrees of damage on different
portions of the city due principally to the course of flow taken across the
alluvial fan upon which the city is built. Various patterns of these "flood
plains" are depicted through the city on various documents prepared by
the U.S. Army Corps of Engineers and by Toups Engineering for the
Federal Flood Insurance Administration. The exact location of these
flood plains through the city have, in the past, been determined in part
by the location of the breaks that have occurred in the existing dikes
along the base of the mountains. It is conceivable that breaks at other
locations would modify the geometrics of these flood plains.
Preliminary studies recently conducted by the Flood Insurance Adminis-
tration utilizing the conditions in the city of Palm Desert specifically as
a trial case indicate that the 100-year frequency design flood could damage
any portion of the city southerly of the Whitewater River and easterly of
the Palm Valley Channel. Such studies are predicated on a dike break
occurring at any location or perhaps stated otherwise, the absence of
dikes. However, this analysis by the Flood Insurance Administration
utilizes a new method recently developed for analyzing flooding condi-
tions in alluvial fan areas, and is considered a trial analysis only, not
an "official" flood plain analysis. In the meantime, the flood plain map
prepared by Toups which shows areas flooded during the Kathleen storm
in 1976 as the "flood plain" will soon be published as the official flood
plain map for this portion of Palm Desert.
The significance of this information is that the entire city within the area
described above is subject to flooding and under existing conditions, any
property within that area could receive flood damage under a particular
set of circumstances. From an assessment engineering standpoint, this
indicates that all properties within the above -described project boundary
would receive benefit and such benefit would be relatively uniformly
proportional to each property's area and in some instances to its land use.
In developing a preliminary indication of an assessment spread, a land
use inventory has been made of that portion of the city which would be
included in such an assessment district and it is attached hereto. Proper-
ties designated and zoned as parks, date groves, open space and hillside
have been excluded from assessment at this point, since drainage benefit
to such properties is limited, if any. Also excluded are public facilities
including city owned properties, schools, college. Reduced assessments,
if any, would be applied to the golf courses for the same reasons stated
above for parks. The balance of the city is master planned, zoned and
developed in several forms of residential and in commercial.
SUMMARY OF LAND USES IN
PALM DESERT S/O WHITEWATER RIVER
AND E/O PALM VALLEY CHANNEL
ASSESSABLE USES
Zone Area (Acres)
Single Family 1682
Multi -Family t93
Condominium 1122
Mobil Homes 122
Planned Residential 479
Commercial 263
TOTAL 3861 acres
NON -ASSESSABLE USES
Date Groves
Open Space (including golf courses)
Parks
Schools
College
Other Public Land
Hillside
TOTAL
$ 46, 176, 000
+ $ 11,959.60/acre
3861 acres
Say 512,000/acre
76
202
19
45
164
130
67
703 acres
SINGLE FAMILY
Area: 1682 acres
Lots: 2742 Developed Lots.
913 Vacant Lots in Existing Subdivisions
689 Proposed Lots in Recently Approved Subdivisions
68 Potential Lots in Undeveloped Areas Zoned for R-1
TOTAL 4412 Lots
Average Assessment:
4412 Lots = 2.62 Lots/Acre
1682 Acres
$12,000/Acre = $4580/Lot
2.62 Lots/Acre
MULTI -FAMILY (Includes Duplexes in S.F. Zones)
Area: 193 acres
Lots: 275 Developed Lots - 1466 Units
129 Vacant Lots
30 Proposed Lots - 238 Units
TOTAL 434 Lots
Average Assessment:
434 Lots = 2.25 Lots/Acre
193 Acres
512,000 'Acre
2.25 Lots, Acre
= $5333/Lot
Average S1000 Per Unit
CONDOMINIUMS
Area: 1122 Acres
Units: 3210 Existing Units
1802 Proposed Units
TOTAL 5012 Units
Average Assessment:
5012 Units = 4.47 Units/Acre
1122 Acres
$12,000/Acre = $2685/Unit
4.47 Units/Acre
PLANNED RESIDENTIAL
Area: 653 Acres
Units: 805 Proposed Units
1137 Potential Units
TOTAL 1942 Units
Average Assessment:
1942 Units = 3.0 Units/Acre
653 Acres
$12,000/Acre
3 Units/Acre
= $4000/Unit
COMMERCIAL
Area: 263 Acres
Lots: 247 Developed Lots
80 Vacant Lots
5 Proposed Lots
7 Potential Lots
TOTAL 339 Lots
Average Assessment:
Assessment of $12,000.00 per Gross Acre
ASSESSMENT SUMMARY
We would propose that within practical limits similar units receive similar
assessments. For example, in a particular block totally occupied by single
family homes, the assessment for each lot would be the same even though
there was a slight variation of lot areas within that block. To a lessor degree,
this would also apply to the condominiums, planned residential, and multi-
family. The average assessment for these blocks, however, would be arrived
at through calculating the average areas. Commercial would be arrived at on
the unit area basis.
The indicated assessment, assuming that the entire cost of the project is
financed by the assessment district procedure without other contributions,
would be $4,580.00 for the average single family residential lot. Based on
the average previous development densities, the average assessment per
condominium unit would be $2, 685.00, the average assessment for a planned
residential unit would be $4,000.00, and the approximate assessment for a
multi -family unit would be $1, 000.00.
The above figures are based upon 1979 dollars. Residential areas with
average lot sizes substantially smaller or larger than the mean would be
accordingly adjusted. Vacant land and vacant lots assume the same assess-
ment as if they were developed. Other than what has been stated above,
we would not propose to further segregate assessments on the basis of
zoning, since zoning is not necessarily permanent and one of the major
flood producing factors is not the water that faIIs upon the assessment
area, but rather the water the runs through the assessment area.
DRAINAGE ASSESSMENT DISTRICTS
AND THE LAW
The Streets and Highways Code, and specifically the "Municipal
Improvement Act of 1913", [Division 12 of the Streets and Highways
Code of the State of California], specifically authorizes the
construction of certain improvements for drains, tunnels, conduits,
culverts and channels for drainage purposes, [Streets and Highways
Code Section 5101 and 10102].
The ability and authorization to form a special assessment
district rests upon the existence of a special benefit to the
assessed property. The general theory of a special assessment
district is that a public agency can construct authorized public
improvements and assess the costs against the benefiting properties
in proportion to the benefits that they receive from the improve-
ments. The rule has oftentimes been repeated that only a special
benefit to the property assessed will justify the levy of the
assessment, not merely general benefit inuring to the public as
a whole.
In 1975 the California Court of Appeal rendered their decision
relating to special sssessments and drainace improvements in a
decision entitled, Harrison v. Board of Supervisors, 44 Ca1.App.3d
852. In that case, the Appellate Court upheld a decision of the
trial court invalidating certain storm sewer special assessments
on the ground that no substantial evidence ..as presented to support
special benefit to the assessed properties and, also, that the
method of spreading the assessments was invalid.
The County of San Mateo was the agency involved in the
proceedings and the amount of the assessment was calculated upon
a rainfall runoff coefficient based wholly upon the zoning of
the units in question. All parties to the decision agreed the
power to specially assess for public improvements is based upon
the existence of a special benefit to the assessed property.
Many cases were then cited.
The Court, in rendering its decision, indicates that first
of all, it is necessary to identify the benefit which the public
improvement will render; next, to determine if the property
owners will receive a benefit different from that of the general
public, and; thirdly, to ascertain if the formula on which the
assessments are made is based on the benefits received. The facts
in the case indicated the benefit to be arrived from the drainage
system was the prevention of street flooding which occurred during
the rainy season, and there was no major testimony of flooding on
the private properties themselves.
The Court indicated the general area would benefit by relief
of the traffic problem and there was no showing of special benefit
to the assessed property. The facilitation of traffic was determined
to be of general benefit to the community and, thus, if repair and
maintenance expenses alone were involved, those are not chargeable
to the abutting owner.
The Court though did indicate that property abutting a street
with a flooding problem would receive a special benefit if the
facilitation of ingress and egress from the parcel was involved.
The question was also raised as to whether property on higher
ground several blocks from any flooded streets would enjoy any
increase in market value [benefit] because of the distant street
drainage problem being improved.
The Court further continued that if water from all the
property drained into public property, such as the street, and
the pooled water caused odors, or a health problem of some nature,
all property owners then might be equally benefited, regardless
of the elevation of their land.
Since the Harrison decision was handed down in 1975, it has
become difficult in certain circumstances for the justification of
the special benefit, and the facts must be clearly ascertained and
understood before any special assessment levy can be exercised.
The Court did not specifically state that an assessment district
for drainage improvements would be invalid or in any way unconstitutional,
but merely indicated under the facts presented and the evidence
before the Board of Supervisors, there was insufficient evidence
or facts to justify the levy of a special benefit assessment and
the method and formula utilizing the drainage district,and the
runoff factor had no direct relationship to the benefits received.
The procedure to form a special assessment district culminates
upon the public hearing, where property owners are given the
opportunity to protest or object to the boundaries of the assessment
district, as well as the method and levy of the special assessment
spread. Prior to the setting of the public hearing, it is necessary
that the Engineer's "Report" be presented to the City Council for
their consideration. The Engineer's "Report" consists of the
following items:
-3-
a. Plans;
b. Specifications;
c. Cost estimate;
d. Assessment roll;
e. Assessment diagram.
From this, it is quite clear the great majority of costs and
expenses necessary for the formation of the assessment district
will have been expended prior to the time the public hearing
is scheduled and, thus, if for any reason the proceedings are
abandoned at the public hearing the City would have already
spent a substantial sum for all the preliminary engineering and
related matters.
PRESENTATION TO
THE CITY OF PALM DESERT
FOR
ALTERNATIVE FINANCING METHODS
FOR
FLOOD HAZARD CORRECTION
MILLER & SCHROEDER MUNICIPALS, INC.
1200 Prospect Street Suite 150
La Jolla, California 92037
ALTERNATE FINANCING METHODS
GENERAL OBLIGATION BONDS
General obligation bonds secured by the full faith
and credit of the issuing entity and its power to levy
taxes have traditionally been a source of capital improve-
ment funds for cities. This has been especially typical
in cases where the municipality required some capital
intensive project that would benefit a broad segment of
its population.
Prior to enactment of Article XIII A of the Califor-
nia Constitution (the Jarvis -Gann Initiative), the power
and obligation to levy ad valorem property taxes for bond
service had comprised the underlying security for general
obligation bonds. Since the enactment of Article XIII A,
the power to levy ad valorem property taxes for the pay-
ment of the principal of and interest on bonds has been
limited to indebtedness approved by the electorate prior
to Jule 1, 1978.
General obligation bonds can still be issued if the
city's financial position and projections for its future
revenues (e.g. sales taxes) support the proposed bond
service without the power to levy ad valorem property
taxes, or other special taxes prohibited under Article
XIII A.
General obligation bonds must be approved by a two-
thirds vote of the electorate.
-2-
The maximum legal interest rate on general obliga-
tion bonds of a city operating under the Government Code
of the State of California is eight percent (8r). Actual
interest rates vary widely, depending on the financial
status and future economic outlook of the issuing city,
the condition of the bond market at the time of the sale
and the number of years to the final maturity. However,
general obligation bonds will usually bear the lowest
interest rate of any long-term financing method.
Another advantage of general obligation bonds is
the flexibility they afford the city in raising funds
to meet bond service - taxes, operating revenues of an
enterprise, or any other unencumbered funds may be used.
GENERAL OBLIGATION DEBT LIMIT
The Government Code limits the general obligation
debt which a city may incur to fifteen percent (15r=) of
the assessed valuation of property in the city. This is
sometimes referred to as its bond capacity. Recognized
bond counsel have given the opinion that the assessed
valuation for this purpose need not reflect any exemp-
tions. The amount of general obligation bonds which a
city may issue at any given time is calculated by de-
ducting the amount of prior general obligation bonds then
outstanding from an amount equal to fifteen percent (157c)
of the assessed valuation of the city. This is sometimes
referred to as the net bonding capacity of the city.
-3-
Because of this legal limitation on the amount of
general obligation bonds which may be issued, cities con-
templating a number of municipal improvements often use
other financing methods whenever feasible, in order to
reserve the general obligation bonding capacity for pro-
jects for which no other financing method is practical.
The practical limit of general obligation debt is
no longer a function of a city's assessed valuation, as
had been the case when ad valorem property taxes pro-
vided security for the bonds. Although the legal limi-
tation is still in effect, the maximum amount of bonds
which can be issued is a function of the anticipated
revenues from other sources, such as sales tax, busi-
ness licensing fees or special taxes authorized by the
voters.
THE JARVIS-GANN AMENDMENT
On June 6, 1978, California voters approved a consti-
tutional amendment, commonly known as "Proposition 13"
or the'"Jarvis-Gann Amendment," which added Article XIII A
to the California Constitution. The principal \thrust
of the Jarvis -Gann Amendment was to limit the amount of
ad valorem taxes on real property to one percent (1r) of
"full cash value," and to limit the definition of full
cash value to 1975-76 tax levels plus two percent a year
to reflect inflation, subject to change in cases of
change of ownership or new construction.
-4-
The Jarvis -Gann Amendment exempts from the one per-
cent (1`:) tax limitation any indebtedness previously
approved by the voters prior to July 1, 1978, and re-
quires a vote of two-thirds of the qualified electorate
to impose special taxes, while precluding the imposition
of any additional ad valorem, sales or transaction tax
on real property. General obligation bonds authorized
prior to July 1, 1978 may still be issued and secured by
property tax levies.
LEGISLATURE'S PROPOSED CONSTITUTIONAL AMENDMENT
A newly proposed constitutional amendment has been
introduced in the California Senate which, if passed by
the electorate. will amend Article XIII A. The proposed
amendment (S.C.A. 26) will allow the levy of ad valorem
property :axes for the payment of voter -approved indebted-
ness. The effect of the proposed amendment will be to
allow the authorization and issuance of general obliga-
tion bonds secured by ad valorem property taxes.
TAX ALLOCATIC'; FONDS
The California Community Redevelopment Law authorizes
a method of financing redevelopment projects based upon
a prescribed allocation of property taxes collected
within a project area. The assessed valuation of tax-
able property within the project area is established at
the level existing prior to the adoption of the redevelop-
ment plan, and all overlapping taxing agencies continue
to receive the :axes derived by the levy of the current
tax rate against this base assessed valuation. All
-5-
property taxes collected each year after the adoption of
the redevelopment plan upon any increase in assessed
valuation above the established base level may be
credited to a redevelopment agency and pledged to the re-
payment of any indebtedness incurred in the development
of the project area. After all such indebtedness has
been repaid, the total taxes produced within the project
area accrue to the respective taxing agencies in the
usual manner. Thus, the tax allocation procedure not
only permits each taxing agency to levy and collect
taxes on the level of assessed valuation existing in a
project area prior to redevelopment, but also provides
that increases in assessed valuation occurring as a
result of such .redevelopment may be used as a basis for
the repayment of indebtedness incurred on behalf of the
project area.
The statutes do not provide for a maximum term for
tax allocation bonds; however, as a practical matter,
the final maturity should be comparable to other types
of municipal obligations, usually 30 years or less. In
many cases, tax allocation bonds are issued as term
bonds rather than serial bonds; that is, the entire issue
matures at some future date instead of a specified por-
tion of principal maturing each year over the life of
the issue. In this manner, principal may be retired
ahead of maturity at the option of the redevelopment
agenc., as tax revenues become available. In order to
-6-
enhance the marketability of term bonds, the resolution
providing for their issuance should provide for accumu-
lation of funds for their payment in a sinking account,
and for a premium to be paid on the bonds retired in
advance of maturity.
Tax allocation bonds must be sold at public sale
and the interest rate (which currently may not exceed
eight percent per annum) is specified in the low bid.
Because tax allocation bonds are often sold based on
the assessed valuation of anticipated future develop-
ments, it is usually necessary to increase the bond
issue by an amount equal to the estimated interest that
will become due on the bonds until such time as incre-
mental taxes are sufficient to meet interest and scheduled
principal payments. By providing the investor with a
guarantee that interest payments will be met on schedule
during development of the project, the marketability of
the bonds is improved. It is customary to establish a
bond reserve that is to be used for the payment of in-
terest and principal only if other funds are not avail-
able. In addition, the projected annual revenues must
exceed the annual payment of principal and interest by
a coverage factor of at least 1.25.
The Community Redevelopment Law allows the sale of
tax allocation bonds at a discount not exceeding five
percent of the principal amount offered. Thus, in order
to be sure that net bond proceeds will be sufficient to
-7-
meet the agency's funding requirements, the principal
amount offered is increased to offset any anticipated
discount.
Despite the fact that there is no legal limit to
the amount of bonds a redevelopment agency may issue
there is certainly a limit to the amount that can be
sold. Primarily, the feasible bonding limit is deter-
mined by the revenue potential from whatever sources of
funds are pledged to the payment of bond interest and
retirement of principal. Sources of revenues that a
redevelopment agency may pledge as security for bonds
include: (1) income and revenues from specified re-
development projects in the community, whether or not
they were financed with tax allocation bonds, (2) State
and Federal aid. (3) tax allocations from the project
financed with the bonds, (4) the general revenues of
the redevelopment agency, or (5) any combination of
these sources. In practice, however, the bonds are most
secured by and payable from tax increment revenue only.
Tax allocation bonds generally sell at higher in-
terest rates than other municipal bonds because the
bonds are payable primarily from incremental taxes
arising from new development, and a redevelopment agency
is seldom able to guarantee that such development will
take place as anticipated or that future tax rates will
he sufficient to retire the outstanding indebtedness.
The major advantages of tax allocation bonds are:
(1) a flexible debt retirement schedule may be provided
-8-
by the issuance of term bonds, so that the payment of
principal is a function of actual tax increment income
each year; (2) the creation or financial participation
of a separate public entity is not required; and (3) the
indebtedness may be authorized by action of the governing
body of the agency.
PROPOSED SPENDING LIMIT INITIATIVE
On April 10, 1979, an Initiative Constitutional Amend-
ment - Limitation of Government Appropriations (designated
as "Proposition 4") will appear on the election ballot.for
a special election to be held on November 6, 1979.
Proposition 4, if passed, will establish and define
annual appropriation limits on state and local govern-
mental entities based on annual appropriations for fiscal
year 1978-79. Proposition 4 requires adjustments for
charges in cost of living, population and other specified
factors. The appropriations limit may be temporarily
changed by the local electorate and reduced in subsequent
years to prevent an aggregate increase in appropriations.
Preposition 4 excludes debt service from the appro-
priations limit, and defines debt service as "appro-
priations required to pay the cost of interest and re-
demption charges including the fund or sinking fund. .
or indebtedness existing or legally authorized as of
January 1, 1979, or on bonded indebtedness thereafter
approved according to law by a vote of the electors."
One of the questions arising from Proposition 4 comes
-9-
from the January 1, 1979 date for authorizing payment
of debt service for bonds issued under statutes not re-
quiring voter approval. Recognized bond counsel is of
the opinion that the aforementioned date sets as uncon-
stitutional retroactive provisions which would result
in breech of contract and that therefore, bonds issued
before passage of the initiative, and issued under
statutes not requiring voter approval (such as tax allo-
cation bonds) are equally bound to receive appropria-
tions pledged as security for these bonds.
It is not clear if special assessment bonds and
tax allocation bonds issued in the future will require
voter approval. There is also uncertainty as to whether
tax increment revenue received by redevelopment agencies
and special assessments constitutes "proceeds of taxes"
as defined by Proposition 4. These issues are likely
to require judicial and legislative interpretation
should Proposition 4 be approved by the voters.
SPECIAL ASSESSMENT PROCEEDINGS
Assessment proceedings are designed to finance im-
provements which benefit a particular area within a city.
Some examples of the types of work that are normally
undertaken by assessment proceedings are: street paving,
sidewalks, curbs, gutters, storm drains, sewers, water
lines, street light and off-street parking facilities.
Under all assessment proceedings, the cost of the work
is assessed against properties within the area. The
-10-
assessments are levied in specific amounts against each
of the individual properties on the basis of the benefit
each parcel receives. The property owner may pay the
assessment in cash during a so-called cash collection
period of thirty days but if any assessments are not paid
in cash during this period, bonds are usually issued to
represent the unpaid assessments.
IMPROVEMENT ACT OF 1911
When the Improvement Act of 1911 is used without
any other enabling act, the contractor who bids for the
improvement work assumes the liability of accepting an
assessment warrant at the outset of the project instead
of cash payments. The assessments do not become payable
until the project is completed and the contractor must
accept the bonds issued for unpaid assessments. Con-
sequently, the construction bid normally is increased
to allow for interest during the construction period.
The bid may also allow for a discount on any bonds to
be issued. Before a contractor submits a bid for the
construction work, he contacts a dealer in special
assessment bonds and obtains a commitment for the assess-
ment warrants and whatever discount is allowed in such
commitment is reflected in the bid on the construction
work.
The 1911 Act also provides for the issuance of
bonds. A 1911 Act bond is issued for each unpaid
assessment over $150 and is secured solely by a lien on
-11-
the particular property for which the bond was issued.
The holder of a 1911 Act bond has the right to foreclose
the property in the event of prolonged delinquency and
the issuing city merely acts as an agent for the bond-
holder in collecting the installments of the assess-
ments and has no liability in connection with the bonds.
IMPROVEMENT BOND ACT OF 1915
An alternative to the 1911 Act bond is provided
under the Improvement Bond Act of 1915. Under the 1915
Act, the same steps may be taken as under the 1911 Act
except that when bonds are issued there is no one bond
constituting a lien against a specific property. The
individual assessments are collected in installments by
the county tax collector at the same time as ad valorem
property taxes. However, in the event of delinquencies
in assessment installments, there is a contingent
liability on the part of the city to provide funds to
offset such delinquencies. This means that in using the
1915 Act, the assessment bond may be strengthened, and
sold on more favorable terms due to the city's contingent
liability.
-12-
Prior to the enactment of Article XIII A of the
California Constitution, this contingent liability could
be secured by an ad valorem property tax levy of all
property within the city in an amount not to exceed 10
cents per hundred dollar assessed valuation. The ability
to levy the tax was eliminated by Article XIII A making
the contingent liability payable solely from available
revenues of the city. Recent enactment of SB 973 has
created an alternative method of meeting possible
delinquencies by allowing the city to establish a
special reserve fund from bond proceeds. The reserve
fund may be in an amount equal to fifteen percent (15%)
of the total amount of assessments to be levied under
the proceedings. When the balance of assessments still
due is equal to the amount in the special reserve fund,
the funds balance is to be advanced to retire the bonds.
The money in the reserve fund may be invested in author-
ized investments. Interest earned on those investments
is credited to the special reserve fund and allows for
the funds to be advanced at an earlier date to retire
the bonds.
SB 973 also authorizes the city, by resolution
adopted prior to the issuance of bonds, to covenant, to
commence and prosecute to completion any foreclosure on
property secured by delinquent installments of assess-
ments which secure the bonds. The resolution may specify
a deadline to commence foreclosure proceedings, along
-13-
with other terms and conditions as the governing body
may determine reasonable. This provision of the bill
was included to eliminate the financial advantage of
delinquency in periods of high interest rates, when the
cost of money is greater than the one percent monthly
penalties usually levied against delinquent assessments
and property taxes.
There are arguments in favor of both types of bond
issues, but generally speaking, the 1915 Act should
only be used when a city is reasonably sure that there
will be no major delinquencies greater than the special
reserves off -setting capacity which would impose a
liability on the city's general fund or where the improve-
ments to be made will benefit the city as a whole.
MUNICIPAL IMPROVEMENT ACT OF 1913
An enabling act, known as the Municipal Improve-
ment Act of 1913, may be used to create assessments for
which bonds may be issued under either the 1911 Act or
the 1913 Act. The 1913 Act provides that an assessment
may be levied against benefited properties in an estimated
amount prior to the time that the improvement work is
actually done. After the assessment is levied and con-
firmed, the usual thirty -day cash collection period
occurs, following which the bonds representing unpaid
assessments are sold and the proceeds used to pay the
contractor cash progress payments during construction.
The 1913 Act procedure usually results in lower financing
-14-
and construction costs than the 1911 Act procedure. How-
ever, under the 1913 Act, interest begins to accrue fol-
lowing the sale of the bonds, which is before the im-
provement work is done; whereas, under the 1911 Act pro-
ceedings, interest does not begin to accrue until after
the work is done. On the other hand, an allowance for
interest during construction is usually included in the
contractor's bid under the 1911 Act proceedings.
In all types of assessment proceedings no election
is required, but there must be a hearing at which a
majority protest may stop the proceedings unless it can
be shown that the project is required to eliminate a
health hazard.
COUNTY OF FRESNO VS. MALMSTROM
The special assessment procedure has been validated
since the passage of the Jarvis -Gann Initiative. In
County of Fresno vs. Malmstrom, the County Clerk refused
to serve the notice of assessment on the property owners
involved or to collect the assessment, contending that
the assessment in question would result in a levy over
one percent (1q) of the value of property in the
district, in contravention of Article XIII A of the
California Constitution (the Jarvis -Gann Initiative).
The County Clerk also contended that the assessment
constituted a "special tax" not approved by two-thirds
of the qualified electors of the district. The Court
of Appeal rejected both arguments, finding that the
-15-
Jarvis-Gann Initiative had been intended to reduce ad
valorem taxes and was not aimed at per parcel assess-
ments. The Court also found that special assessments
are different in nature than taxes, that they did not
constitute a special tax and therefore were not re-
quired to be approved by two-thirds of the qualified
electors.
COMMUNITY FACILITIES DISTRICTS
Pursuant to the Community Facilities Law of 1911,
a community facilities district may be formed by the
governing body of any city whenever, in the city's
judgement, it is necessary or convenient to provide
proper sanitation, drainage, or water service in an area
that is either greater than or less than the city.
Districts may be formed to construct, acquire and fi-
nance water systems and collection, treatment or disposal
facilities for sanitary or drainage purposes including
any and all laterals, interceptors, trunks and outfall
lines, as well as drains, conduits, and outlets for
surface storm water.
Whenever the governing body of a city determines
that the public interest requires the construction of any
of these improvements, it may proceed to form a district.
This procedure requires that a resolution of public
interest be adopted by the governing body of the city,
notice given, a hearing held, and upon conclusion of
the hearing, the district is formed by the governing
-17-
offered for sale is limited by the revenue -producing
capacity of the district.
An authorized issue of bonds may be divided into
two or more series which may be sold separately. The
final maturity date for each series must be within 40
years of the date of issuance of that series.
At any time following formation of the district,
additional territory may be annexed to it if it is deter-
mined by the city council at a public hearing that the
additional territory will be benefited by the district.
If any unincorporated areas or portions of another city
are to be annexed, the consent of the county and/or the
other city must be obtained prior to the conclusion of
the hearing. The annexed territory becomes subject to
all the liabilities of the district.
COUNTY SERVICE AREA
The County Service Area Law of 1953 provides for the
establishment of a County Service Area empowered to pro-
vide numerous services within an unincorporated 'area of
a county, and within all or any part of a city with the
approval of that city's legislative body. The law
specifically includes provisions for sewer service, and,
in counties over 20,000 square miles, flood protection.
It is possible that special legislation could be enacted
which would include Riverside County for eligibility to
the flood protection provision.
An advantage of the County Service Area is the
allowance for improvement areas within the Service Area
-18-
to meet the specific requirements of the smaller terri-
tories within the Service Area's domain.
The law provides for revenues from service fees or
charges, connection charges, water disposal fees and
sewer stand-by charges. The only assessment provided
for are ad valorem, on property of either the entire
area, an improvement area or a zone within an area, de-
pending on the purpose of the assessment. An alterna-
tive would be to ammend the law to allow for per parcel
assessments on benefited lands.
A County Service Area can authorize general obliga-
tion bonds by a two-thirds vote, and can authorize a
revenue bond issue by simple majority, pursuant to the
Revenue Bond Law of 1941.
COACHELLA COUNTY WATER DISTRICT
The County Water District Law provides for the
establishment of County Water Districts; the law's in-
tent is to provide a vehicle for the provision, and
control of water, including drainage and storm waters.
The area of the district can be a single county, or two
or more contiguous counties.
The Coachella County Water District presently pro-
vides some of these services within the City. The
County Water District Law provides for improvement districts
within the District to meet the special needs of a par-
ticular area of the District. These improvement districts
are easily formed, either by a majority vote of the
-19-
electorate within the proposed improvement district, or
by approval of the County Water District's Board of
Directors. The Board members become the governing body
of the improvement district.
A county water district has the power to charge
water and sewer rates, to establish rates and charges
for sanitation services and to sell or lease property,
oil and minerals, and to charge wholesale rates for
hydro -electric power.
If revenues are insufficient, the County Water
District Law provides for assessments for bonded in-
debtedness and improvement district assessments on
benefited property.
A county water district may either issue general
obligation bonds by a two-thirds vote, or revenue bonds
by majority vote of the electors.
FARMERS HOME ADMINISTRATION
A possible source of funds might be a bond sale to
the Farmers Home Administration (FrHA). FmHA is author-
ized to make loans to develop community facilities for
public use in small rural areas and towns.
There are two pools of funds from which FmHA can
lend money. One of these funds is general, for the
development of community- facilities (i.e., fire stations,
libraries, hospitals, industrial parks). The other
fund is specifically for construction of public utili-
ties, drainage, sewer and water works.
-_0-
There are two principal advantages of loans through
the FmHA. First, the loans are made at an annual in-
terest rate of five percent. Secondly, the maximum term
on such loans is 40 years, or the useful life of the
facilities, whichever is less. The extended maturity
decreases the annual debt service for bonds purchased
by FmHA.
EMPLOYMENT DEVELOPMENT ADMINISTRATION
In the event that the nationally unemployment rate
rises to 6.5%, the Employment Development Department
(E.D.A.), Public Works Grant Program will be reactivated.
The E.D.A. would then be funded to make public works
grants.
-21-
CONCLUSIONS
The most appropriate method of financing the proposed
improvements is general obligation bonds. However, because of
the provision in the Jarvis -Gann Amendment, which prohibits the
levy of ad valorem property taxes, except for bonds approved
by the voters prior to July 1, 1978, the authorization and
issuance of general obligation bonds is not feasible under
current law. The authorization of general obligation bonds
would, however, be possible if SCA 26 is approved by the
electorate at the elections scheduled for June, 1980.
Even if SCA 26 is approved by the electorate, the issuance
of general obligation bonds of the City is not feasible because
the amount required to finance the proposed improvements exceeds
the City's general obligation bond debt limit of fifteen
percent (15%) of the City's assessed valuation. Based on the
City's 1979-80 assessed valuation of $135,314,000.00, the City's
general obligation bond debt limit is $20,250,000.00. In addition,
the issuance of general obligation bonds of the City to finance
the entire project is not appropriate because a portion of the
City would not be benefited by the improvements, and properties
outside of the City which would be benefited would not participate
in the financing of the proposed improvements.
If SCA 26 is passed, then an improvement district authorized
to issue general obligation bonds would be the most appropriate
and economical method of financing the proposed improvements
-22-
because the boundaries of the improvement district could be
established so as to conform to the boundaries of the benefited
property by excluding non -benefited properties which are within
the City and including benefited properties which are outside
of the City.
Improvement districts can be formed by the County of
Riverside pursuant to the County Service Area Law, by the Coachella
Valley County Water District pursuant to the County Water District
Law, and by the City pursuant to the Municipal Facilities Law of
1911. The principal difference between the three laws is the
legislative body which has the authority to implement, administer
and govern the improvement district. County service areas are
governed by the Board of Supervisors of Riverside County. An
improvement district established by the Coachella Valley County
Water District would be governed by the Board of Directors of
the Water District. An improvement district formed pursuant to
the Municipal Facilities Law of 1911 is governed by the City
Council of the City which initiates the formation of the improve-
ment district.
If the City decided to proceed with an improvement district
pursuant to the Municipal Facilities Law of 1911, then it would
be necessary to mail notices to property owners indicating the
City's intent to form an improvement district and to hold a
public hearing. In addition, if the improvement district extended
beyond the City limits, it would be necessary to obtain the consent
-23-
of the Board of Supervisors of the County if unincorporated
county territory was to be included and of the City Council
of any City in which City territory was to be included. An
election to authorize the issuance of the general obligation
bonds of the improvement district could be held at one of the
election dates scheduled for March, June or November of 1980.
If the election to authorize the bonds was scheduled for March
or June, then it would be necessary to make the authorization
subject to the approval of SCA 26. In order to schedule the
election for March, 1980, it would be necessary to hold the
hearing during the first week of December, 1979 and to call
for the hearing at the first City Council meeting in November,
1979.
The Community Redevelopment Law provides an alternative
which could be used to finance a portion of the proposed improve-
ments. The Redevelopment Agency of the City currently -is
receiving tax increment revenues in the approximate amount of
$516,000.00 [bonding capacity on $4,200,000 with net proceeds
of $3,400,000], which could, if the Redevelopment Agency wished
to do so, be pledged to the payment of tax allocation bonds for
the purpose of financing the portion of the proposed improvements
which is of benefit to the redevelopment project area. Properties
within the existing redevelopment project area have repeatedly
suffered flood damage in each of the major storms and therefore
-24-
a portion of the proposed improvements would be of benefit to
the redevelopment project area. Based on the current tax
increment revenues allocated to the Redevelopment Agency, the
Redevelopment Agency could issue approximately $4,200,000.00
principal amount of tax allocation bonds. After the payment
of costs and the establishment of reserve funds to secure the
bonds, the Redevelopment Agency would have available bond
proceeds of approximately $3,400,000.00 to be used for
improvements. The passage of Proposition 4, The Gann Initiative,
may have an impact on the ability of the Redevelopment Agency
to issue its tax allocation bonds and on the allocation of tax
increment revenues to the Redevelopment Agency.
Flooding is one of the factors which can justify the
formation of a redevelopment project area under the Community
Redevelopment Law. In order to provide storm drainage and flood
control improvements, the existing redevelopment project area
boundaries could be expanded or a new redevelopment project area
could be initiated to encompass portions of the City which are
subject to flooding and inundation. Expanding the redevelopment
project area boundaries or creating a new redevelopment project
area would not provide an immediate source of additional revenue
because it would be at least two years before any additional
tax revenues would be allocated to the Redevelopment Agency. In
addition, the passage of Proposition 4, as previously discussed,
may limit the amount of tax increment revenues which can be
-25-
allocated to the Redevelopment Agency.
A third financing method which could be used to finance a
portion of the proposed improvements is special assessment
proceedings. A special assessment could be used in combination
with either general obligation bonds, if SCA 26 is approved, or
tax increment financing. Special assessment proceedings would
be most appropriate for financing the local street drainage
improvements such as curbs and gutters, which are required in
order to implement a comprehensive flood control and drainage
improvement program.
Special assessment proceedings and tax increment financing
can also be used in a combination in which the tax increment
revenues are used to reduce the amount of the property owners
future assessment debt payments. As previously discussed, tax
revenues for any expanded or new redevelopment project will not
be received for some time and the passage of Proposition 4 may
have an effect on the issuance of tax allocation bonds.. The
principal disadvantage of special assessment proceedings is the
large amount of the assessment lien which would be required.
This disadvantage can, at least in part, be mitigated to the
extent that the property owners can be assured that revenues
from other sources, such as tax increment revenues, will be
available to reduce the burden on the property owner.
-26-
RECOMMENDATIONS
It is recommended that:
1. The City Council acting as the Redevelopment Agency,
review the priorities for expenditures of tax increment revenues
and that to extent priorities permit, the Redevelopment Agency
should allocate a portion of its tax revenues to the proposed
improvements in order to reduce the burden on property owners
within the City;
2. The portion of proposed improvements, such as curbs
and gutters, which are of benefit to local properties be
financed by either special assessment bonds;
3. The remaining public improvements be financed by
general obligation, assuming that SCA 26 will be approved by
the electorate in June, 1980.
CITY OF PALM DESERT
STATE AND FEDERAL FUNDING
AND
LEGISLATION
FLOOD HAZARD CORRECTION
October 24, 1979
In considering potential sources of federal and/or state
funding for construction of drainage systems to mitigate flood
hazards to the City of Palm Desert ("Palm Desert"), it should
be emphasized that the "onsite systems" will benefit areas
within Palm Desert and the "offsite systems" will benefit an
area greater than Palm Desert. These differences in the areas
of benefit relate primarily to the responsibility of Palm Desert
for construction of onsite systems and the responsibility of
Coachella Valley County Water District ("CVCWD") for construc-
tion of offsite systems and secondarily to the method of
financing, sources of funding and nature of possible legisla-
tion.
In reviewing potential sources grant and/or loan funds
from state and federal sources, it should be noted that a
distinction is made or implied between onsite and offsite
systems; however, this distinction is not always clear. A few
of the federal and state statutes which appear to provide fund-
ing for onsite and/or offsite systems include the Public Works
and Economic Development Act of 1965 (42 USCA 310); Federal
Flood Control Act of 1948 (33 USCA 701); Watershed Protection
and Flood Prevention Act (16 USCA 1000); State Flood Control
Law of 1946; Davis-Grunsky Act (Sections 12880 et seq. of
Water Code); State Water Resources Law of 1965 (Sections 12570
et seq. of Water Code).
Based upon information available to this office, the
possibility of Palm Desert obtaining any state and/or federal
funding for onsite systems does not appear encouraging; how-
ever, the possibility of CVCWD obtaining state and/or federal
funding for offsite systems may have greater potential due to
the regional nature of such systems.
Legislation to provide funding or to implement financing
for onsite and/or offsite systems could be introduced as
follows:
1. Special legislation to provide funding for Palm
Desert and surrounding areas of benefit;
2. Legislation to appropriate funds under existing
statutes; and/or
3. Legislation to create additional sources of
revenue and to authorize such sources of
revenues to be used as security for long-term
debt.
Prior to the introduction of any legislation, Palm Desert
should coordinate with CVCWD due to the necessity of construct-
ing offsite systems. It is quite possible that such legisla-
tion should be introduced by CVCWD and supported by Palm Desert
as well as other affected agencies and interested organizations.
The final date for introducing legislation to the Finance
Committee is March 10, 1980; consequently, in order to provide
adequate time for review by the author and to obtain comments
from Legislative Counsel, such legislation should be submitted
by mid -February, 1980.
The recommendations and conclusions of this office may be
summarized as follows:
1. The area of benefit for offsite systems and the
area benefit for onsite systems should be sepa-
rately defined.
2. The financing of offsite systems should be
undertaken by CVCWD with the support of Palm
Desert.
3. The financing of onsite systems should be
undertaken by Palm Desert and coordinated
with CVCWD.
4. The possibility of Palm Desert obtaining
state and/or federal funds for onsite systems
is not encouraging.
5. The possibility of CVCWD obtaining state
and/or federal funds for offsite systems.
6. The preparation of legislation to provide
funds and/or assist in financing both onsite
and offsite systems should be immediately
commenced by Palm Desert.
7. Palm Desert should immediately initiate con-
ferences with CVCWD to develop a coordinated
effort to finance both onsite and offsite"
systems.