HomeMy WebLinkAboutMaster Drainage Plan•
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EXECUTIVE SUMMARY
This Master Drainage Study has been prepared for the City of Palm Desert to achieve the
following objectives:
• To document the status of existing runoff and flooding conditions within a 26-
square-mile study area of the existing City Boundary and sphere of influence.
• To identify and evaluate alternatives for providing 25-year flood protection.
• To identify improvements needed to implement the recommended alternative
facilities and investigate retention basins for 10-, 25-, 50-, and 100-year storms.
• To develop cost estimates and preliminary engineering design data for the
recommended flood protection plan.
1. EXISTING RUNOFF AND FLOODING CONDITIONS
Runoff modeling was performed using the Rational Method under the guidelines of the
Riverside County Flood Control and Water Conservation District Hydrology Manual. A
runoff analysis was developed for the study area for both the 25-year and the 100-year
storms.
II. 25-YEAR FLOOD PROTECTION ALTERNATIVES
Alternatives were then considered for providing 25-year flood protection. These
- , alternatives included:
1. Cast -in -place concrete pipe. Due to the nature of soils in the study area, this
alternative was not recommended, however if the situation warrants,this alternative
should be investigated.
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2. Concrete -lined corrugated steel pipe. Available engineering data indicated a short
life expectancy for this type of pipe. Therefore, its use was not recommended.
3. Reinforced concrete pipe. Recommended for the 25-year flood protection. The
combination of reinforced concrete pipe and concrete -lined channels (designed for
a 100-year flood) represents the most cost effective system.
III. REQUIRED IMPROVEMENTS TO IMPLEMENT RECOMMENDED
ALTERNATIVE FACILITIES
Improvements were then identified and developed based on the selection of the
reinforced concrete "multi -type" conveyance system. A complete system of pipelines, a
major channel, and retention basins along with their costs were developed for budgetary
and preliminary layout purposes. Within the study area two distinct areas of special
attention have been encountered: the hillside area west of the Palm Valley Channel and
the area south of the Deep Canyon Channel.
Installation and maintenance of facilities in the hillside area west of the Palm Valley
Channel could become costly and very difficult to maintain because of the terrain.
This area, unlike the remaining portion of undeveloped land in the City, does not possess
the potential for major development.
Each development in the hillside area shall be responsible for handling their on -site and
off -site drainage to the satisfaction of the City. The need for protection of downstream
properties and developments is paramount, and a storm water mitigation plan must be
reviewed and approved by the City prior to construction. The cost of such facilities must
be borne entirely by the developer.
In areas where it is expected that a high debris load or other special flood hazards will
be encountered, special design criteria must be considered by the City. Those criteria
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may include (1) 100-Year storm runoff; (2) design capacity of drains, channels and other
"- facilities increased by 100%; (3) maximum allowable flow velocity of 15 feet per second;
and (4) open channel flow conditions throughout the system.
The construction of debris basins within this area will not only have to answer the
questions of safety and maintenance, but also the potential of pollutants settling in the
debris basin. The EPA and the State Department of Water Resources criteria must also
be met in regards to debris basin discharge.
The southern area also presents a dilemma for proposed facilities in that the Deep
Canyon Channel, the major conveyance system in this area, will not accept any additional
runoff generated from development. Consequently, any further development in this area
will be forced to retain all the incremental runoff produced within that specific
development.
IV. COST ESTIMATES AND PRELIMINARY ENGINEERING DESIGN DATA
1 To facilitate the development of system alternatives and their costs, the study area was
divided into four zones. These four zones are delineated by the following boundaries;
Zone 1: Deep Canyon, Palm Valley and Whitewater Channels and the westerly City limits,
Zone 2: The Whitewater Channel, The Palm Springs Ridge Line and the easterly and
westerly City limits, Zone 3: The Palm Springs Ridge Line, Interstate 10, Monterey Avenue
and the easterly limits of the Sphere of Influence, Zone 4: The area north of Interstate 10
and the east line of sections 22, 27 and 34.(Reference Only)
The construction cost of the recommended facilities to provide 25-year flood protection
and, in a unique circumstance, 100-year flood protection in Zones 1, 2 and 3 and
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' excluding the Mid -Valley Channel is estimated at $23,295,129. The area south of 1-10 and
north of the Palm Springs Ridge Line has been studied for a 100-year storm based upon
the design criteria developed by the Coachella Valley Water District. This area will
accommodate the Mid -Valley Regional Channel. A 100-year storm event is the criterion
I for design of this regional facility and its tributaries. Within the study area two distinct
i drainage basins exist. The area south of the Palm Springs Ridge Line and north of the
` Deep Canyon Storm Channel drains to the Whitewater Channel. The area north of the
Palm Springs Ridge Line drains to the proposed Mid -Valley Channel. The total assessable
acres within the study area is 4890 acres.
The drainage fee established by Resolution 92-51 and Ordinance 653 for Zone 1 is $4,000
per acre, for Zone 2, $1,500 per acre and for Zone 3, $1,000 per acre. This cost is tied
to the Engineering News -Record 20 cities index for January 1, 1992. Drainage Fees will
become effective by September 1, 1992.
CONCLUSIONS
The recommendations made in this report are based on the following conclusions:
1. The Master Drainage Plan Description summarizes runoff quantities computed
using Rational Method of Hydrology for a 25-year storm, with the exception of the
area tributary to the Mid -Valley Storm Channel which was analyzed for a 100-year
storm.
2. The Master Drainage Plan Description shows the recommended alternative,
including design flows for all proposed drainage facilities.
3. The Recommended Master Plan facilities and their costs are itemized in the Master
J Drainage Plan Description.
I 4. The total drainage fee per acre for all recommended facilities for a 25-year design
t frequency (with a 100-year design frequency for the Mid -Valley Channel) is $4,000
per acre for Zone 1, $1,500 per acre for Zone 2 and $1,000 per acre for Zone 3.
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RECOMMENDATIONS
The following recommendations are made:
1. Adopt revised fee schedules as supported by this Master Plan of Drainage.
2. Capital improvement plans for drainage improvements be developed using the
Master Drainage Plan Description.
3. Construction of Master Plan facilities associated with the proposed Mid -Valley
Channel be incorporated in the design of the Mid -Valley Channel.
4. The problem areas in the southern region bounded by the Whitewater Channel, the
Palm Valley Channel, the Deep Canyon Channel and Indian Wells on the east of
the City be the highest priority with the implementation of the Master Drainage
Plan.
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RESOLUTION NO. 92-51
A RESOLUTION OF THE CITY COUNCIL OF THE CITY OF PALM DESERT,
CALIFORNIA, APPROVING A MASTER DRAINAGE PLAN FOR THE CITY OF
PALM DESERT AND AUTHORIZING IMPLEMENTATION OF SAID MASTER
DRAINAGE PLAN.
WHEREAS, In May of 1990, the City Council authorized NBS/Lowry,
Incorporated, to develop a citywide master drainage plan studying both the
incorporated areas of the city and its spheres of influence; and
WHEREAS, the City Council did on the 11th day of July, 1991, hold a duly
7 noticed public hearing and a continued public hearing on the 23rd day of January,
1991, in order to consider said citywide master drainage plan; and
WHEREAS, after considering testimony and arguments presented at the public
hearing, the City Council found that the following facts and reasons justify
approval of the drainage plan.
`] 1. The City's growth requires an updated citywide master drainage plan.
2. The proposed drainage plan expands and modifies the results of
.� previous studies, and provides a means of coordinating drainage
aspects of pending developments and also creates a mechanism for
evaluating the impact of storm water runoff.
3. The proposed drainage plan is consistent with the goals, objectives,
and policies of the City's general plan, its current zoning and land
use regulations, and modern engineering practice.
NOW, THEREFORE, BE IT RESOLVED by the City Council of the City of Palm
Desert, California, as follows:
I. -That the 1992 citywide master drainage�-Iylan prepared by NBS/Lowry,
and described above, is hereby approved and adopted for the reasons
set forth in this. resolution.
2. Immediate implementation of said master drainage plan -is necessary to
ensure a comprehensive and sufficiently funded program for the
development of adequate drainage facilities to -serve the city and its
spheres of influence.
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3. Funding sources for completion of the citywide master plan will be
established as part of the budget process.
4. The City may impose additional or reduced fees on a case —by —case
basis where a need for such additonal or reduced fee is demonstrated
as required by Government Code Section 66001.
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PASSED, APPROVED AND ADOPTED at a regular meeting of the Paine Desert
City Council, held on this 11 day of .tune 1992, by the following
vote, to wit:
AYES:
NOES:
ABSENT:
ABSTAIN:
Benson, Crites, Snyder, Kelly
None
Wilson
None
ATTEST:
SHEILA R. GILLIGAN, Cit lerk
City of Palm Desert, C twornia
RrCAARD S. KE LY, Mayor
City of Palm Desert, Calif nia
FACT! DOCUMENT TO WHICH THIS CERTIFICATE IS
A'r ACH.0. IS CERTIFIED TO BE A FULL TRUE AND
C?RRO COPY OF THE OAiGPM ON FILE AND ON
RECuRO IN MY OFFICE.
Bated: 31 C
2
SHEILA R. GILLIGAN, City Clem
CSty of t�kf
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ORDINANCE NO. 653
AN ORDINANCE OF THE CITY COUNCIL OF THE CITY OF PALM DESERT,
CALIFORNIA, AMENDING SECTION 26.49.050 OF THE PALM DESERT
MUNICIPAL CODE RELATING TO DRAINAGE FEES.
WHEREAS, Section 26.49.050 of the Palm Desert Municipal Code provides for
drainage fees by area, as authorized by Section 66483 of the Government Code; and
WHEREAS, changes in construction costs have occurred since drainage fees
were last adjusted by the City Council on the 9th day of July, 1987; and
WHEREAS, notice of the public hearing at which this ordinance is considered
has been given accordance With Government Code Section 66016(a).
NOW THEREFORE, the City Council of the City of Palm Desert, California,
DOES ORDAIN as follows:
SECTION 1: The City Council finds and determines as follows:
a. The amount of the drainage fees adopted pursuant to this ordinance
does not exceed the estimated cost of providing the services for which
the tees are imposed.
b. The subdivision and development of property within the City's
drainage areas will require construction of the facilities described in
the City's master drainage plan.
C. The fees recommended by the master drainage plan, which was adopted
by the City Council on the 23rd day of January, 1991, are fairly
apportioned within the City's drainage areas both on the basis of
benefits conferred on property proposed for subdivision and on the
need for such facilities created by the proposed subdivision and
development of other property within such areas.
d. The City Council makes these findings based on the estimated cost of
T constructing• the facilities for which such drainage fees are imposed
1 and that, in accordance with Government Code Section 66016(a), this
data has been on file for at least 10 days prior to the public hearing
[ at which this ordinance is considered.
SECTION 2: That Section 26.49.050 of the Palm Desert Municipal Code be
amended to provide as follows:
"26.49.050 Establishment of Off —site Drainage Fees. There is 'hereby
established on off —site drainage fee of four thousand dollars ($4,000) per
acre for land in the areas of the City designated as Zone 1, one thousand
five hundred dollars 41,500), in Zone 2 by the City's master drainage plan,
j which is incorporated herein by this reference.
There also is established an off --site drainage fee of one thousand dollars
($1,000) per acre for- land in the areas of the City designated as Zone 3, and
by the City's master and
plan. The amount of fee shall be calculated
on full and partial acres, carried to the nearest 100th of a percentage. In
the case of land to be subdivided, the' fee shall apply for any and all uses
to which the land may be put. In the case of construction or improvement
of subdivided land, the fee shall apply only to new commercial, industrial,
professional, group dwelling, or community facility use (see Section 25.56.080
of this code). Said fees shall be collected, deposited, and expended pursuant
to Section 66483 of the Government Code of the State of California and all
other applicable laws of the State of California. All necessary drainage fees
established by the City of Palm Desert shall be deposited with the City prior
to approval of the final map in the case of land being subdivided, or prior
to issuance of a building permit in the case of construction or improvement
or subdivided land. The City shall have the right, in lieu of accepting cash,
to accept any other proper and valid consideration as may be determined by
the City." Fees Imposed pursuant to this section are the amounts necessary
for the purposes set forth in the City's master drainage plan. The City may
impose additional or reduced fees on a case —by —case basis where a need for
such additional or reduced fee is demonstrated as required by Government
Code Section 66001.
SECTION 3: The City Clerk shall certify to the passage and adoption of this
ordinance and shall cause the same to be published once in the Palm Desert Post,
a newspaper of general circulation, printed, published, and circulated within the
City of Palm Desert, and the fees imposed by this ordinance shall become effective
sixty (60) days after its adoption.
PASSED, APPROVED, and ADOPTED on the 25th day of .Tune 1992,
by the City Council of the City of Palm Desert, California, by the following vote,
to wit:
AYES: BENSON, CRITES, SNYDER, KELLY
NOES: NONE
ABSENT: NONE
ABSTAIN: WILSON
�J
ATTEST:
SHEILA R. GILEIGAN, City ef k
City of Palm Desert, Cali la
7
RICAARD . S. KELLY, Mayor
City of Palm Desert, Californ
oiv fay on �t
SHEILA R. GILLIGAN, City C#erk
City of PW ORM Californis
By:
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TABLE OF CONTENTS
Page
EXECUTIVE SUMMARY ........................................ i
Resolution 92-51
Ordinance 653
INTRODUCTION ............................................ 1
Authorization ........................................... 1
Scopeof Work ......................................... 1
Historic Background ..................................... 1
MASTER DRAINAGE PLAN BOUNDARIES ......................... 4
CityBoundary .......................................... 4
Watershed Boundary ..................................... 4
EXISTING DRAINAGE SYSTEM ................................. 7
Existing Drainage Studies ................................. 7
Regional Drains ......................................... 7
DRAINAGE SYSTEM ANALYSIS ................................. 9
Methodology ........................................... 9
Runoff Coefficients ...................................... 9
Hydrology Studies ...................................... 10
FUTURE DRAINAGE SYSTEM ................................. 12
Zone1.............................................. 12
Zone2.............................................. 15
Zone3.............................................. 16
Zone4.............................................. 18
System Alternatives ..................................... 19
Master Drainage Plan Detailed Cost Analysis ................... 20
Recommended Priority List ............................... 27
DRAINAGE FEES ........................................... 28
Present Practices ...................................... 28
Recommended Fee Structure .............................. 31
TABLE OF CONTENTS (Continued)
APPENDICES
A - Incremental Runoff Analysis & Retention Basin Sizing
B - City of Palm Desert, Required Storage by Land Usage
C - City of Palm Desert, Incremental Runoff Analysis - Residential
D - Hydrology Output for Retention Analysis
REFERENCES
GLOSSARY OF TERMS
GLOSSARY OF TERMS
CFS Cubic Feet Per Second
Drainage Area The area that contributes storm flows to
a specific concentration point, or storm drain system
Hydrology A multi -disciplinary subject dealing with the occurrence,
circulation, and distribution of the waters of the Earth.
Peak Discharge The highest rate of storm runoff expressed in cubic feet per
second.
RCP Reinforced Concrete Pipe
Sub Area A smaller tributary area located within a drainage area.
25 & 100 year storm An annual maximum event whose peak discharge is equaled
or exceeded once, on the average, every 25 or 100 years,
respectively.
Standard Project Flood The discharge that may be expected from the most severe
combination of meteorologic and hydrologic conditions that
are considered reasonably characteristic of the geographical
region involved.
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INTRODUCTION
AUTHORIZATION
In 1990, the City of Palm Desert authorized NBS/Lowry, Incorporated to develop a
Citywide Master Drainage Plan.
The purpose of the authorization was to provide a comprehensive long-range plan for
the development of drainage facilities within the corporate limits of the City, as well as
the areas within the City of Palm Desert's sphere of influence.
SCOPE OF WORK
The authorization given by the City of Palm Desert limited the scope of this study to the
existing incorporated area of the City, as well as the areas within the City of Palm
Desert's sphere of influence. These areas will be segregated into four distinct zones as
follows:
Zone I South of the Whitewater Channel
Zone Il North of the Whitewater Channel to the Palm Spring Ridge
Line
Zone III Palm Springs Ridge Line to Interstate 10
Zone IV Interstate 10 to Ramon Road(Reference Only)
These zones have been studied on the basis of existing development and drainage
facilities, drainage facilities as planned in the existing master drainage plans, and
projects which our research indicates to be constructible in the immediate future.
The scope of the following investigation is intended to optimize the value of the previous
studies through the expansion and modification of their results to develop a
comprehensive drainage plan consistent with the City's adopted general plan, current
zoning and land use, and with current engineering practice.
HISTORIC BACKGROUND
Historically, two generally distinct flood control problems have existed in the Coachella
Valley. The first involves runoff from the storms occurring in adjacent mountain ranges.
Stormwater from watersheds in the San Bernardino, San Jacinto, Santa Rosa and Little
San Bernardino mountain ranges is carried into the valley via the Whitewater River and
its tributaries. Heavy rainfall in these mountainous areas, combined with the spring
snowmelt, has contributed to major floods in 1916, 1927, 1938 and again in the late
1960's, 1970's, 1980's. .
The second type of drainage problem is that resulting from storms occurring primarily
over the valley floor. While runoff quantities from these storms are relatively small in
comparison with those generated in the watersheds of the adjacent mountain ranges,
they are of importance in planning a drainage system because of their intensity. This
type of high -intensity, short -duration storm activity caused substantial damage in the
Palm Desert area in 1948 and again in 1951.
There are three distinct types of storms that occur in the Coachella Valley. The summer
storm poses a greater threat of flooding to the valley than a winter storm because of its
high intensity and short duration of rainfall. The September 1976 storm that pounded
Palm Desert was a summer type storm. The eccentricity of this type of storm can be
illustrated by the fact that Rancho Mirage, Indian Wells and La Quinta suffered no
significant damages during the September 1976 storm, while Palm Desert experienced
extensive damage.
The winter storms are more evenly spread over a wide area and generally tend to drop
more substantial rain than the summer type storms. The winter storms come primarily
from the North Pacific; and if tropical disturbances are right, they can pick up moisture
from the south. The 1916 flood was the most noticeable storm of this type. The third
type of storm, the spring storm, stems from melting snow combined with rainfall to
produce significant runoff down the canyons. This type of storm has limited impact on
the City of Palm Desert.
1 The first organized effort to control flooding in the Coachella Valley was made by the
Indio Levee District. The merger of the Indio Levee District and the Coachella
L{ Stormwater District in 1915 resulted in the organization of the Coachella Valley
l Stormwater District. Three years later the Coachella Valley County Water District was
formed as a vehicle to conserve local water resources and to contract for supplemental
water from the Colorado River. The activities of the County Water District and the
Stormwater District were in some respects duplicated and in conflict; consequently, in
1937 the two districts were merged. The Coachella Valley County Water District, as the
r surviving agency, assumed responsibility for regional flood control in the southern and
�1 central portions of the Coachella Valley.
As the Palm Desert area began to develop, the Coachella Valley County Water District,
in conjunction with developers, constructed a number of facilities to protect the area from
runoff generated in adjacent mountain canyons. In 1940, the Coachella Valley County
Water District completed the Deep Canyon Stormwater Channel. This channel, along
with a series of dikes and a spreading area, were constructed to divert major storm flows
` around Palm Desert to the Whitewater Channel near Point Happy about three and one-
half miles east of the present City limits.
2
71 Construction of the Palm Valley Stormwater Channel was completed in December 1983.
The construction of this facility, adjacent to the westerly City Limits of Palm Desert,
provides for the diversion of stormwater produced in the mountain regions westerly of
the channel. Prior to 1983, a dike was constructed south of the Ironwood Country Club
r, to divert stormwaters from Dead Indian Canyon around Palm Desert.
I
Together, the Whitewater, Palm Valley and Deep Canyon Stormwater Channels and their
appurtenant facilities serve as the City's primary protection against major flood damage.
(See Exhibit A) No further development of regional facilities has occurred within the City
limits with the exception of a planning study by the Coachella Valley Water District for
the Mid -Valley Stormwater Channel paralleling Interstate 10.
In contrast, there has been an effort by the City to control localized flooding by
implementing the recommendations of Master Drainage Plans prepared in 1976, 1979,
and 1987.Examples of these efforts are the construction of the Fred Waring storm drain
in 1985, the South Portola storm drain in 1987, the North Portola storm drain in 1989 as
well as other local drainage facilities. Many of the provisions of these plans remain valid
and have, to the extent applicable, been included in the current Citywide Master
Drainage Plan.
3
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S MA TER DRAINAGE PLAN BOUNDARIES
T CITY BOUNDARY
The City of Palm Desert lies southerly of Interstate 10 to the base of the Santa Rosa
Mountains. The east -west boundaries of the City vary from Monterey Avenue to
Eldorado Drive, north of the Whitewater Channel, the Palm Valley Channel to the City of
Indian Wells western boundary, south of the Whitewater Channel.
The sphere of influence extends beyond the City boundary in both the northern area and
southern area of the City. A large portion of the sphere of influence extends well into the
Santa Rosa Mountains with the Dead Indian Canyon and the Deep Canyon serving as
major floodways in this area. The study area, which is divided into four drainage zones,
r encompasses a total area of approximately 16,700 acres.
WATERSHED BOUNDARY (See Exhibit 1)
The watershed boundaries are divided into four distinct zones. The zones are generally
bounded by the City's corporate limits or sphere of influence and further geological or
Z manmade boundaries.
• Zone 1. This region is located south of the Whitewater Channel. This area is
considered the "original" City limits. Flows in this region generally tend to flow
northeasterly to the Whitewater Channel, with the exception of areas west of
Monterey Avenue which drain into the Palm Valley Channel. This region is
dominated by residential development, both single-family and multifamily
dwellings. There are some commercial developments in this zone located
predominately along Highway 111 and El Paseo. There is approximately 580
acres of undeveloped land within Zone 1.
Within the study area two distinct areas of special attention have been
encountered: the hillside area west of the Palm Valley Channel and the area
south of the Deep Canyon Channel. The hillside area has special interest due to
the terrain. Installing and maintaining facilities in this area could become costly
and very difficult to maintain. This area, unlike the remaining portion of
undeveloped land in the City, does not possess the potential for major
development. The lack of useable land and the rugged terrain limits the
development potential in this area.
Each development in the hillside area shall be responsible for handling their on -
site and off -site drainage to the satisfaction of the City. The need for protection
of downstream properties and developments is paramount, and a storm water
1 mitigation plan must be reviewed and approved by the City prior to construction.
The cost of such facilities must be borne entirely by the developer.
4
Any facility in a hazardous area or areas with a potential for high debris loads
must be designed using special design criteria resulting in increased costs. This
j special design criteria recommends design of drainage facilities for the 100 year
j flood,the capacity of all facilities increased to a factor of 100 percent, velocities
in these facilities should not be less than 15 feet per second, and the system
should be designed for open channel flow.
The construction of debris basins within this area will not only have to answer the
questions of safety and maintenance, but also the potential of pollutants settling
in the debris basin. The EPA and the State Department of Water Resources
criteria must also be met in regards to debris basin discharge.
The southern area also has a dilemma for proposed facilities. The Deep Canyon
Channel, the major conveyance system in this area, will not accept any additional
runoff generated from development. Any further development in this area will be
forced to retain all the incremental runoff produced within that specific
development.
• Zone 2. This region is located south of the Palm Springs Ridge Line and runs
to the Whitewater Channel. Monterey Avenue serves as the western boundary and
the mid -section line of section 10 & 15 as the eastern boundary. The flow pattern
from this zone is basically southerly, with minor deviations from east to west.
Within Zone 2, approximately 1660 acres remain undeveloped.
Development within this area is largely planned residential communities, mainly
country club type developments, with golf courses and paved streets serving as
the major conveyance of runoff. Within this region the following developments
contain all runoff within their sites: Marriott Desert Springs Hotel & Spa, Lakes
Country Club, and Palm Desert Greens. Other developments within this zone
drain directly to the Whitewater Channel: Monterey Country Club, the Chaparral Country
Club, and the Portola Country Club.
• Zone 3. This region is located north of the Palm Springs Ridge Line to the
proposed CVWD Mid -Valley Channel. The western boundary of Zone 3 is
Monterey Avenue, and the eastern boundary is Washington Street. This region
is primarily undeveloped, approximately 2650 acres at present, although some
large planned residential developments have been completed within this region:
Desert Falls, Avondale, and Palm Valley Country Clubs. The basic flow pattern
in Zone 3 is northeasterly toward the proposed Mid -Valley Channel.
• Zone 4.(Reference Only) This region is located north of Interstate 10 with Ramon
Road as the northern boundary and the eastern section line of sections 22, 27
and 34 as the eastern boundary. This region is primarily located on the large
alluvial fan radiating from the Indio Hills to the north. Within Zone 4 approximately
5
1280 acres remain undeveloped. Development in this zone is for
p p the most part,
planned residential, with country dub type developments. Golf courses are
Y surrounded by homes in these developments. The golf courses are used to
contain the runoff for a 100-year storm within the development. The general flow
pattern in this zone is to the south with 1-1 0 serving as a levee prohibiting runoff
from continuing southward. A retention basin will serve as a termination point for
the runoff in this zone.
Zone 4 is located within an AO Flood Zone as designated on the National Flood
Insurance Program, Flood Insurance Rate Map; panel 1625 of 3600, Riverside
County, California as published by the Federal Emergency Management Agency.
The flood depth within Zone 4 ranges from two feet at Interstate 10 to four feet at
the mouth of Thousand Palms Canyon with velocities of flow ranging from six
feet per second to nine feet per second within those same limits.
Any inquires in regards to drainage or development in this area or the Thousand
Palms Study should contact CVWD for the appropriate information.
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EXISTING DRAINAGE SYSTEM
EXISTING DRAINAGE STUDIES
Previous drainage studies have been performed for the City of Palm Desert at
appropriate times of the city's expansion. A Master Drainage Plan conducted by 1.
Harold Housley and Willdan Associates in June 1976 encompassed the "original" City
limits. These limits ranged from the Whitewater Channel south to the base of the Santa
Rosa Mountains.
Some of the proposed facilities suggested in this study have been incorporated into
drainage systems that exist today. In 1987, the $11 million South Portola Storm Drain
facility with its tributaries was implemented, as was the Fred Waring Drive system in
1985. This study has incorporated these existing conditions with proposed additions.
r j
A second study of Palm Desert was compiled in August 1979 by Willdan Associates.
This study encompassed the northern limits of the City's expansion. The Whitewater
Channel served as a southern boundary and Interstate 10 as a northern boundary. This
Y area is divided into two distinct drainage areas by the Palm Springs Ridge Line that runs
southeasterly through the City.
1 A third study was performed by Charles Haver and Associates in April 1987. This study
involved the area south of the Palm Springs Ridge Line to the Whitewater Channel. At
the time of the study much of this area had been developed, and the need for a
1 drainage plan was evident.
A $2 million drainage facility completed in 1989, consists of a 96" Reinforced Concrete
Pipe (RCP) north in Portola Avenue to Hovley Lane West,reducing to a 66" RCP. Future
construction will extend a 36" RCP to Country Club Drive. An existing branch line on
Hovley Lane West has been proven sufficient to convey the calculated flows.
REGIONAL DRAINS
The regional drains in the Palm Desert City limits include the Whitewater Channel, the
Deep Canyon Channel, and the Palm Valley Channel. A proposed Mid -Valley Regional
Channel by the Coachella Valley Water District will run parallel to the Southern Pacific
Railroad tracks through the City of Palm Desert.
The Whitewater Channel is a major thoroughfare of runoff in the Coachella Valley. The
Whitewater Channel is the primary outlet for runoff generated in drainage Zones 1 and
2.
7
The Palm Valle Channel runs in a norther) direction through the wester) art of Palm
Y Y g YP
Desert. Its function is to.drain areas to the southwest of the City limits and, for the most
part, areas west of Monterey Avenue (State Route 74). This channel carries runoff into
the Whitewater Channel.
The Deep Canyon Stormwater Channel runs northeasterly along the southeasterly edge
of Palm Desert. Areas south of Haystack Road are drained into this channel, and the
flows are carried northeasterly along the base of the mountains through Indian Wells to
the Whitewater Channel.
A proposed regional drain, which will parallel the Southern Pacific Railroad, is the Mid -
Valley Channel. This facility is designed to pick up runoff south of the Southern Pacific
Railroad between Date Palm Drive in Catehdral City and Washington Street in Palm
' Desert. It will then continue along the same course collecting runoff south of the
l Southern
Pacific Railroad, between Washington Street and the Coachella Valley Storm Channel.
The Coachella Valley Water District, as the regional flood control agency, has the
responsibility of maintaining and constructing these regional drains.
0
DRAINAGE SYSTEM ANALYSIS
METHODOLOGY
The hydrologic study performed in this Master Drainage Plan was completed under the
guidelines of the Riverside County Rood Control and Water Conservation District
(RCFC&WCD) Hydrology Manual. The procedures utilized are documented in the
RCFC&WCD Hydrology Manual and incorporated into the computer Program RATRV.
The Rational Method is used to determine the peak discharge for drainage areas and
is based on the equation:
Q=CIA
Where:
Q = Runoff (Cubic feet per second)
C = Coefficient of Runoff
= Rainfall Intensity (Inches per hour)
A = Area of Land (Acres)
The Rational Method is a very conservative approach to runoff quantities due to the fact
that the method calculates runoff using cumulative time of concentration in conjunction
with individual sub -areas. This can be beneficial for its use in a Master Drainage Study;
but for design calculations, a more precise hydrologic study should be used.
The coefficient of runoff is a ratio of storm water runoff rate to the rate at which rainfall
occurs. The coefficient depends on the rainfall intensity, soil classification and cover,
percentage of impervious areas, and antecedent moisture conditions.
PERCENT IMPERVIOUS AREA
RECOMMENDED
LAND USE RANGE VALUE
Undeveloped .00 - .10 0
Single Family - 1 acre lot .10 - .25 .20
Single Family - 1 \2 acre lot .30 - .45 .40
Single Family - 1 \4 acre lot .45 - .55 .50
Multi - Family .45 - .90 .75
Commercial .80 - 1.00 .90
9
Rainfall intensity is a statistical result of recorded rainfall in a specific area. Rainfall
research for the area in and around the City of. Palm Desert yielded data from several
rain gauges. The gauges in and around the City limits, however, only recorded long
duration information. Therefore, short duration information from Cathedral City, Deep
Canyon Lab, and the Thermal Airport was used to validate the assumption, by CVWD,
F� that rainfall intensities for Cathedral City, as reported by the RCFC&WCD Hydrology
Manual apply to the region.
HYDROLOGY STUDIES
This drainage study was developed using the Rational Method of Hydrology for the
Riverside County Flood Control and Water Conservation District. The computer program
RATRV was used to define pipe size and channel size for non -pressure flow. This
analysis is based on the ratio of depth of flow to diameter of pipe being most efficient
at 80%. The Manning's n value of .013 was used in this study which represents
Reinforced Concrete Pipe.
Certain assumptions were made for drainage areas in the northern portion of the City
based on Chapter 26.49 of the Palm Desert Municipal Code. Section 26.49.060,
"Drainage Facilities," states:
"Development of 10 gross acres or more shall provide sufficient on -site
i storm water retention and/or retardation so as to limit peak runoff occurring
during a storm having 25-year intensity to a rate no greater than that which
would have otherwise occurred under undeveloped conditions."
This report utilized Section 26.49.060 of the Palm Desert Municipal Code in the study of
Zones 1 & 2; and, as a result, the quantities of flow were substantially reduced, thereby
reducing drainage facility costs.
Zone 1, the area south of the Whitewater Channel, was studied to verify existing
drainage facilities and to develop new facilities where needed. Upon development, land
within this zone is currently subject to a drainage fee per acre of $3,200. Areas east of
Portola Avenue have experienced some problems of flooding in the past. With this in
mind, two new facilities, one along Deep Canyon Road and the other along the eastern
City boundary, were developed to correct this problem and to reduce the amount of
runoff into neighboring Indian Wells. Another problem in this zone occurs at Haystack
Road and the open space east of Chia Drive. A sump condition exists in the open
space. A culvert has been designed to alleviate this condition. A similar condition exists
at Silver Spur Trail and Haystack Road. A culvert connecting to the Haystack Channel
on the north side of Haystack Road has been designed to drain this area.
10
Zone 2, the area north of the Whitewater Channel and south of the Palm Springs Ridge
j Une, was studied utilizing the criteria of Chapter 26.49 of the Palm Desert Municipal
11 Code. The existing drainage fee in this area is $4,000 per acre. The drainage areas in
this region were studied as being of undeveloped nature. This assumption is justified
r by the fact that each development of 10 acres or more will retain the incremental
difference in runoff quantities between developed and undeveloped conditions.
Zone 3, the area north of the Palm Springs Ridge Une and south of Interstate 10, drains
northeasterly to 1-10. This area has an existing drainage fee of $4,000 per acre. The
proposed Mid -Valley Channel that parallels 1-10 will pick up runoff in this region. The
Coachella Valley Water District will be responsible for maintenance of this channel.
CVWD requires developments in this region to retain 100% of a 100- year storm. The
Mid -Valley Channel is designed to collect only street runoff, however, on -site drainage
may be released into the channel over a Hive day period. With this design requirement
in mind, the City of Palm Desert must address the issue of the Palm Desert Municipal
Code regarding incremental runoff retention. This drainage region was studied with
street right-of-way serving as sub -area limits, to abide by the criteria set forth by CVWD.
Zone 4,(Reference Only) the area North of 1-10 to Ramon Road, is another drainage area
that was studied under the design criteria of CVWD. As required by CVWD, any
development within a floodplain must not add to flows of a 100-year storm. Therefore,
the incremental increase of a 100-year storm must be retained on -site. Developers in
this zone designed facilities to retain 100% of the on -site runoff from a 100 year storm.
These developments, Td-Palms, Ivey Ranch and the proposed North Star Development,
all pass the historic flows through their sites but maintain complete retention of runoff
accumulated on -site.
11
FUTURE DRAINAGE SYSTEM
ZONE 1
Zone i is bounded on the east and west sides by the City limits, on the north by the
Whitewater Channel, and on the south by the Deep Canyon Storm Channel (see Exhibit
2).
• Drainage Area # 1 A (See Exhibit 2.1 A)
This drainage area runs north from Cahuilla Way to the Whitewater Channel, is
bounded on the west by the Palm Valley Channel and on the east by Monterey
Avenue (State Route 74). The proposed facilities south of El Paseo convey runoff,
heading north on State Route 74, at intermittent pick-up points to the Palm Valley
Channel. These lines are Line 1 A-3, Line 1 A-4, Line 1 A-5 and Line 1 A-6. Line 1 A-
2 conveys runoff from El Paseo, just south of Route 111 to the Palm Valley
Channel. Line 1 A-1 is a proposed system to carry runoff along Fred Waring Drive,
west of Monterey Avenue, to the Palm Valley Channel. There are two existing
drainage facilities in this area: a private line conveying flows from the Palm
Desert Town Center to the Palm Valley Channel and a system along the southerly
property line south of Hedgehog Street. Both lines are adequate for the
conveyance of the 25-year storm.
• Drainage Area .#1 B (See Exhibit 2.1 B)
This drainage area is bounded on the east by the Palm Valley Channel and on the
west by the City boundary. The northern boundary is Park View Drive and the
southern boundary is at the intersection of the Palm Valley Channel and the
western City limit. This area consists of relatively flat terrain in the north and
hillside in the south. Two systems have been designed for this region. The
Joshua Road storm drain (Line 1 B-1) is a designed facility to convey runoff in the
Joshua Road area to the Palm Valley Channel. The Paradise Palms Hotel storm
drain carries flows from Painters Path to Fred Waring Drive. This designed
system will head east in Fred Waring Drive and terminate in the Palm Valley
Channel. Both of these systems are adequate to convey the 25-year storm to the
Palm Valley Channel and will relieve this area of the troublesome runoff. No
J facilities have been developed for the hillside area due to the difficulty of
maintenance and other factors, as previously discussed in this report.
• Drainage Area # 1 C (See Exhibit 2.1 C)
Drainage area #1 C is located south of Haystack Channel and north of the Dead
Indian Canyon. State Route 74 is the western boundary, and Indian Wells is the
12
eastern boundary of this drainage area Lines 1 C-3 and 1 C-4 are existing facilities
that convey runoff to the Haystack Channel from the western two-thirds of this
drainage area. Proposed Lines 1 C-1 and 1 C-2 are culverts to convey the
overland flows under Haystack Road to the Haystack Channel.
• Drainage Area #1 (See Exhibit 2.1)
This area's boundaries extend from just west of Monterey Avenue to just East of
San Pascual Avenue, with the Whitewater Channel on the north and El Paseo on
the south, with a small area along the Pines to Palms Highway in the south.
i The facilities mentioned below are existing for this drainage area The main line
in this area is an existing facility designed to carry runoff down Fred Waring Drive
(Line 1-2) to the San Pascual Channel (Line 1-7). Line 1-1 carries runoff on
Monterey Avenue south to Line 1-2. Another tributary to Line 1-2 is Line 1-3
which conveys runoff north on San Anselmo Avenue. The largest tributary of Line
1-2 is Line 1-4. This line picks up runoff on Palm Desert Drive, conveys the flows
k to San Pablo Avenue, and continues north until it reaches Line 1-2. Line 1-5
conveys runoff from the College of the Desert south on San Pablo Avenue until
it reaches Line 1-2. Flows from Catalina Avenue are conveyed through Line 1-6
which extends north on San Pascual Avenue to Line 1-7.
aThe proposed facilities in this area consist of a main line running south to north
on Monterey Avenue, Line 1-9, which conveys the runoff to the Whitewater
Channel. Line 1-9 has proposed tributaries along its length, contributing to the
large diameter main line. The reason this line is directed north on Monterey
Avenue past Fred Waring Drive is due to the fact that the existing facility on Fred
Waring Drive is inadequate to convey this additional runoff. Additions to this
existing facility were studied; but due to the conflicts with existing utilities in Fred
Waring Drive, the proposed Line 1-9 was directed north along Monterey Avenue.
At the present time a portion of Line 1-9 from the Palm Desert Town Center to
Fred Waring Drive and along Fred Waring Drive to San Anselmo Avenue is being
designed for construction.
Problem areas between El Paseo and Highway 111 from Lupine Lane to San Luis
Rey Avenue called for proposed facilities connecting to the existing Line 1-4 in
Highway 111.
• Drainage Area #2 (See Exhibit 2.2)
Drainage area #2 is located north of the Haystack Channel between the Pines to
Palms Highway on the west and just east of Portola Avenue on the east. This
area runs north of El Paseo and then follows Drainage Area #1's eastern
boundary to the Whitewater Channel.
13
A
The majority of facilities in Drainage Area #2 are in existence. Line 2-1 carries a
large amount of the runoff produced in the southern portion of Zone 1. Line 2-1
consists of large drainage facilities that run from Grapevine Avenue north in
Portola Avenue to the Whitewater Channel. Line 2-4 extends westward along
Grapevine Avenue, picking up a tributary" line on Desert Lily Drive. A proposed
tributary to Line 2-4 is Line 2-6, which extends southward on the western
boundary of the Marrakesh Country Club. Another existing tributary to Line 2-1
is Line 2-3, a large drainage facility extending west on Shadow Mountain Drive.
This extension also picks up runoff on San Luis Rey Avenue to the south down
to Ironwood Street.
• Drainage Area #3 (See Exhibit 2.3)
Drainage Area #3 is confined to Portola Avenue on the west, Deep Canyon Road
on the east, and the City Limit to the south and the Whitewater Channel on the
north. Line 3-1 is the main line in this drainage area. It extends from Fairway
Drive in Deep Canyon Road to Fred Waring Drive, then it heads east on Fred
Waring Drive connecting to Line 4-1 at Phyllis Jackson Lane. Line 3-2 is a
tributary, collecting flows west of Deep Canyon Road on Palm Desert Drive south.
Line 3-3 extends Line 3-1 westward on Fairway Drive collecting runoff generated
south of Fairway Drive. Line 3-2A is another tributary to line 3-1. This line
collects flows on Candlewood Street and conveys them to the main line.
A small system on Deep Canyon north of Fred Waring Drive, Line 3-4, collects
runoff from the interior streets south of Magnesia Falls Drive and west of Deep
Canyon Road and conveys them north to the Whitewater Channel.
• Drainage Area #4 (See Exhibit 2.3)
The eastern boundary of Drainage Area #4 runs north along the City Limits of
Indian Wells, the southern boundary is the City limit, the western boundary lies
just east of Deep Canyon Road, and the northern boundary is the Whitewater
Channel. Line 4-1 is proposed to run North from Fairway Drive along the City
limit to Higghway 111. At present, a portion of Line 4-1 is being designed from
just north of Candlewood to Highway 111. This drainage area tends to flow
northeasterly to the City of Indian Wells; therefore, Line 4-1 is designed to
intercept these flows.
14
MASTER PLAN FACILITIES
FXHIBIT 2
4OWRY
ENGINEER$ & PLpNtfERS
LEGEND
EXISTING PIPE
PROPOSED PIPE
STUDY AREA
DRAINAGE AREA BOUNDARY
MASTER PLAN FACILITIES
EXHIBIT 2.1A
w
4--
PAUrI DE'SFRT
� o
9
N B
l3 Y! 1
E%QRaM8 & Pis
LEGEND
— __--- EXISTING PIPE
PROPOSED PIPE
STUDY ARKA
loxv. w M.—N-A a DRAINAGE AREA BOUNDARY
MASTER PLAN l=ACILMES
EXHIHIT 221 B
oft
-L)OWRY
ENGINEERS & PLANNPRS
C--= I
701/71'
LEGEND
EXISTING PIPE
PROPOSED PIPE
STUDY ARE
DRAINAGE AREA BOUNDARY
MASTER PLAN FACILITIES
EXHIBIT 2-1C
�YVRY
WOMMM & ru+Wxs
qH
LEGEND
EXISTING PIPE
PROPOSED PIPE
4 STUDY AREA
++■y■�■w.�= DRAINAGE AREA BOUNDARY
L 1 II Ci I a
c
�~ on
J c
c
R.C.s. rn a
SAN
PABLO � J
i F—S
}.
NASCUAL244 X ' OHL - _—
llu
MASTER PLAN FACILITIES
EXHIBIT 2-1
LOWRY
84Gfem8 & P"W"s
LEGEND
EXISTING PIPE
PROPOSED PIPE
STUDY AREA
DRAINAGE AREA BOUNDARY
� P5 ll'---\-,�--,T��-- --I'-*
MASTER PLAN FACILITIES
EXHIBIT 2.2
s
IL
IG�)OWRY
ENGINOM do PLANNERS
Go
-13
04
FRED WAF.NG DR!VE
48 60"
STATE Hi WAY 11
-ItTiL
LEGEND
aH w -
...... EXISTING PLFE
PROPOSED PIPE
sum tm=9 v v%" STUDY AREA
1L J 3�Isw.mmri DRAMAGE AREA BOUNDARY
z
MASTER PLAN FACILITIE`
EXHIBIT 2.3
I ZONE 2
Zone 2 is bounded by the Whitewater Channel on the south, the Palm Springs Ridge
y Line on the north, and the City limits are the east and west boundaries (see Exhibit 3).
• Drainage Area #5 (See Exhibit 3.5)
Drainage area #5 is bounded on the west by Monterey Avenue, on the north by
the Palm Springs Ridge Line, and on the south by the Whitewater Channel. The
eastern boundary extends north from the Whitewater Channel approximately 1 J4
mile east of Portola Avenue to Country Club Drive, then heads east on Country
j Club Drive to the Palm Springs Ridge Line.
t The main portion of this system runs in Portola Avenue from Frank Sinatra Drive
to the Whitewater Channel. Line 5-1, which runs in Portola Avenue from the
Whitewater Channel to Country Club Drive, is an existing facility. This facility is
responsible for collecting flows at Portola Avenue conveyed by Country Club Drive
and Portola Avenue north of Country Club Drive. This facility also picks up flows
from Hovley Lane West. This tributary consists of proposed Line 5-4 which drains
the southwest corner of Section 5 from Country Club Drive, then runs south along
the boundary of the Sagewood Development to Hoviey Lane. Line 5-2 picks up
runoff from Line 5-4 and conveys it eastward, again picking up runoff from Line
5-3, until it connects to Line 5-1 in Portola Avenue. The facilities previously
mentioned are either existing or designed for construction as of this report.
An extension north in Portola Avenue is proposed from Country Club Drive to just
beyond Frank Sinatra Drive (Line 5-5). Line 5-6 picks up flows from section 32
and conveys them along Frank Sinatra Drive to Line 5-5. Another proposed
j tributary on Line 5-5 is Line 5-7 which collects runoff from Section 4 and conveys
1 the flow westward along Country Club Drive to Line 5-5.
i • Drainage Area #6 (See Exhibit 3.6)
Drainage Area #6 is bounded on the north by Country Club Drive, on the west
by Drainage Area #5's eastern boundary, on the east by the Palm Springs Ridge
Line and the City limit, and on the south by the Whitewater Channel.
Line 6-1 runs in Cook Street from Hovley Lane East to the Whitewater Channel.
This proposed line primarily serves the industrial areas along Cook Street, picking
up runoff from Line 6-3 which runs westerly on 42nd Avenue. Line 6-1 also has
tributaries both east and west on Merle Drive. Line 6-4 extends west on Merle
Drive, picking up flow from the industrial area; and Line 6-2 conveys flows east
of Cook Street to the City limits, down to Merle Drive west and connects to Line
6-1.
15
i
�:: •' T -y— I MO 7EB
ERE AVENUE —
rK I S ,n + — I—
pIf c E
31
71
i I + + •' POD.
Av NUE54
TM
I 1' I �I
— # i
� pit
n f �i
z i l
• � - - - ram- ... -
m 1:3 r Fsl I
k ELD RADO DRIVE
?-7•
- I
C
0
LEGEND
,f.
��� ���o RETENTION BASIN
UASI CLUB DRIVE EL ,,i EXISTING PIPE
ENGINEERS & PLANNERS
— — — m -- ' PROPOSED PIPE
v + —_
A ' — :_-.•= �= STUDY AREA.
D. A. 10 Y _ PALM S-PRINGS RIDGE LINE
�- ■ n DRAINAGE AREA BOUNDARY
i D
d
UM 10-,36*
1
1JASHINGTON S REET
MASTER PLAN FACILITIES
EXHIBIT 3
GERALD FORD DkIVE
EXISTING PIPE
PROPOSED PIPE
rya STUDY AREA
PALM SPRINGS RIDGE LINT
DRAINAGE AREA, BOUNDAR)
MASTER PLAN FACILITIES
EXHIBIT 3.5
`a'
LEGEND
�j
tt-- t% a CA—Wab—1
Y, �OWR -- -
ENGINEERS & PLANNERS
EKSTING PIPE
PROPOSED PIPE
STTj-DY AREA
PALM SPRINGS RIDGE LINI,
DRAINAGE AREA BOUNDARY
MASTER PLAN FACILITIES
EXHIBIT 3-6
ZONE 3
Zone 3 is bounded on the north by Interstate 10, on the south by the Palm Springs
Ridge Line, on the west by Monterey Avenue, and on the east by Washington Street (see
Exhibit 3).
• Drainage Area #7 (See Exhibit 3.7)
This area is bounded on the north by 1-10 and on the south by the Palm Springs
Ridge Line. The western boundary follows the Palm Desert Adopted Sphere
boundary north from the Palm Springs Ridge lane to 1-10. The eastern boundary
of this area follows Portola Avenue north from the Palm Springs Ridge Line to I-
10.
In this Drainage Area only accumulated street flows can be conveyed into the
proposed Mid -Valley Channel. Line 7-1 conveys street flows north along the
future continuation of Portola Avenue. Line 7-2 picks up street flows at Monterey
Avenue and Dinah Shore Drive and conveys them to the proposed Mid -Valley
Channel.
• Drainage Area #8 (See Exhibit 3.8)
Drainage Area #8 is bounded on the north by 1-10, the south by the Palm Springs
Ridge Line, the west by Portola Avenue, and on the east by Cook Street. Only
one facility is proposed for this area, Line 8-1. lane 8-1 conveys street flows
within this area north in Cook Street to the proposed Mid -Valley Channel.
• PrainaQe Area #9 (See Exhibit 3.9)
Drainage Area #9 is bounded on the north by 1-10 and on the south by the Palm
Springs Ridge Line. The western boundary is Cook Street and the eastern
f boundary of this area runs north along the eastern boundary of Section 11 to
1 Country Club Drive, then heads east to the mid -section line of Section 1, and then
heads north to 1-10.
Within this area, approximately 1/2 mile east of Cook Street, the Mid -Valley
Channel will head north under 1-10, three proposed 54" RCP culverts will convey
the flow under 1-10.
Line 9-1 conveys street flows east along Frank Sinatra Drive where it connects
with Line 9-2, then heads southeast along the northern limit of Palm Valley
Country Club paralleling 1-10 until approximately 1/2 mile west of Washington
Street. At that point, Line 9-2 connects with Line 9-3. Line 9-3 drains the low
r point on Country Club Drive approximately 1/2 mile west of Washington Street.
After the confluence of Line 9-2 and Line 9-3, the system is jacked under 1-10
with 3-39" RCP's into a channel that will run north to the proposed Mid -Valley
' Channel.
�{ • Drainage Area #10 (See Exhibit 3.9)
J Drainage Area #10 is bounded on the west b the eastern bound of Drainage
Y �Y 9
Area #9, on the north by 1-10, on the east by Washington Street, and on the
south by the south section line of Section 12.
1, Line 10-1 conveys runoff north along Washington Street in the City of Palm
Desert. Street flows in this area are collected on Washington Street and conveyed
to a retention basin along 1-10.
17
Ed W, Y - -----
EN(ANEER3 & PLANNERS
LEGEND
RETENTION BASIN
EXISTING PIPE
PROPOSED PIPE
sue. STUDY AREA
=,J :lyri. PALM SPRINGS RIDGE LINE
xer�r, DRAINAGE AREA BOUNDARY
MASTER PLAN FACILITIES
EXHIBIT 3
L
I
EMMEOM & PLANmms
LEGEND
EXISTING PIPE
PROPOSED PIPE
STUDY AREA
A It
PALM SPRINGS RIDGE LINE
# M
DRAINAGE AREA BOUNDARY
Li
ry
F-I
r)
MASTER PLAN FACILITIES
EXHIBIT 3-7
NB
AWRY
WGNMRS & PLe
LEGEND
�P ,!mil X Sf Y%37.>
EXISTING PIPE
PROPOSED PIPE
STUDY AREA
PALM SPRINGS RIDGE LINE
DRAINAGE AREA BOUNDARY
MASTER PLAN FACILITIES
EXHIBIT 8.8
}
j
LEGEND
M RETENTION BASIN
EXISTING PIPE
+ N� PROPOSED PIPE
■
...#,� STUDY AREA
' jr�OWRY PALM SPRINGS RIDGE LINE
0,"11111111M5 Rom DRAINAGE AREA BOUNDARY
}I ■
r
Pd�
PROPOSED MID —VALLEY CHANNEL.
7°LINE 9-1
pM y • �.
�.. 5
AV❑N 43)39
DALE — .-.--
PALM
�'ALEY LINE 9-4 4,ajp
Y 1 A \1!%9 36"1 LINE: 9-3 �
L ,
Ld C❑UNTRY CHUB DRIVE
> LINE 10-1
RES[7RTER
I LA I Lj
IN" D.AA1810
_z
yyy
W
P.R.-S S.
I U I W❑❑D
HAVEN
I
I
LJ
J
MASTER PLAN FACILITIES
EXHIBIT 3.9
4
A
-
ENONEERS ac PLANNERS
LEGEND
F RETENTION BASIN
MSTING PIPE
PROPOSED PIPE
rAaac::.Y STUDY AREA
PALM SPRINGS RIDGE LINE
s. It DRAINAGE AREA BOUNDARY
MASTER PLAN FACILITIES
EXHIBIT 3
ZONE 4 (Reference Only)
Zone 4 is bounded on the south and west by Interstate 10, on the north by Ramon
Road, and on the east by eastem section lines of sections 22, 27, and 34 (see Exhibit
3). In this zone, north of 1-10, only one drainage area was designed for pipe flows.
Given the knowledge of the drainage within the existing and proposed developments,
no other facilities were designed. The Federal Emergency Management Agency has
determined that Zone 4 is located in a Flood Zone and is given an AO designation. The
depth of flooding in this zone range from two feet at Interstate 10 to four feet at the
mouth of Thousand Palms Canyon with flow velocities ranging from six feet per second
to nine feet per second.
0 Drainage Area #11 (See Exhibit 3.11)
Drainage Area #11 is bounded on the north by Ramon Road, on the west by the
Tri-Palms Development, on the south by the Ivey Ranch Development, and on the
east by the east section line of Section 22.
Line 11-1 conveys flows along the southern boundary of Section 21 eastward to
a retention basin. Line 11-2 conveys flows westward along the southern
boundary of Section 22 to the same basin. Line 11-3 runs south along the
intersection of these two sections to the retention basin.
The retention basin in Drainage Area #11 has been calculated to hold 116.62
acre-feet of flow. To achieve this volume of retention, a suggested 20-acre site
with a depth of 6 feet would be sufficient.
Options for development of this site range from a park to a golf course fairway or
a golf course lake. These are just a few possibilities for the provision of an
aesthetically pleasing retention basin.
18
--Jmwft�
h . F V—V
NB�'---�
OWRY
. E%GMnS &PLAWMS
M. C)
AV
4�1
36' 27'
m
7W
P-4
PRORMCD UNC ll-�
NORrH 36,
sYr STAR r-
/7 LI
LEGEND
RETUNTWN BASIN
TviSTING PIPE
PROPOSED Pipr
STUDY AREA
PALM SPRINGS RIDGE UNE
dp 0! DRAINAGE ARE& BOUNDARY
L
17
FRIPALMS
MASTER PLAN FACUTIES
EXHIBIT 3.11
SYSTEM ALTERNATIVES
This proposed Master Drainage Plan was developed using reinforced concrete pipe
(RCP) to convey flows throughout the City. Although these facilities are adequate to
convey runoff, other alternative conveyances were studied.
Cast in place concrete pipe (CIPP) is an alternative to RCP. This alternative was not
introduced into this study because of factors deterrent to its use. Trench wall stability
is a major deterrent to using CIPP in the region. Due to the nature of soils in Palm
Desert, this system does not seem feasible for keeping drainage facility costs at a
minimum.
Cast in place concrete pipe is installed more efficiently if trench wall stability is
maintained, no ground water is encountered, and if the soils are not expansive in nature.
If these conditions can be met in specific areas, CIPP should be investigated as an
altemative.
r� Another alternative conveyance of runoff for use which was studied is corrugated steel
x pipe - concrete lined (HCCL). This system was not expanded into the design criteria due
to the fact that the design life of RCP is longer than that of HCCL. With this in mind and
r comparing material costs (both conveyances are relatively equal), HCCL was not
incorporated into this proposed system.
There are other alternatives to this proposed drainage plan. Open concrete lined
channels could replace some in -ground facilities. Although open channels are cheaper
to install, the issues of maintenance, right-of-way acquisition, safety and aesthetics must
be considered.
Although there are alternatives to the system designed in this report, the system of RCP
is recommended as the best alternative for the conveyance of runoff in Palm Desert.
A detailed cost analysis for the recommended drainage alternative, consisting of RCP,
is provided in the following table.
19
PALM DESERT MASTER DRAINAGE PLAN
. DETAILED COST ANALYSIS
DRAINAGE AREA #1A
Line # Flow
(CFS)
Diameter Length Cost/Foot Cost
(Feet) ($) ($)
1 A 1
243
48 IN
400
$ 192
$ 76,800
65
36 IN
700
144
100,800
1 A 2
55
30 IN
1100
120
132,000
1A-3
70
36 IN
2800
144
403,200
1 A-4
103
36 IN
1020
144
146,880
1 A 5
85
36 IN
275
144
39,600
1A-6
175
48 IN
940
192
180,480
Outlet Structures
6 EA
30,000
180,000
TOTAL COST DRAINAGE AREA #1A
$1,259,760
DRAINAGE AREA #1 B
Line # Flow
(CFS)
Diameter Length Cost/Foot Cost
(Feet) ($) ($)
}
1 B-1 864
(2)1ax4 RCB
1375
$ 500
$ 687,500
799
1 Qx4 RCB
402
500
201,000
60
36 IN
635
144
91,440
53
30 IN
108
120
12,960
35
24 IN
138
96
13,248
Outlet Structures
1 EA
30,000
30,000
TOTAL COST DRAINAGE AREA #1B
$1,036,148
DRAINAGE AREA #1C
Line # Flow
Diameter
Length
Cost/Foot
Cost
(CFS)
(Feet)
($)
($)
1C-1 17
30 IN
200
$ 120
$ 24,000
`
1 C-2 108
48 IN
308
192
59,136
65
36 IN
230
144
33,120
Outlet Structures
2 EA
30,000
60,000
TOTAL COST DRAINAGE AREA #1C
$176,256
20
DRAINAGE AREA #1
Line # now
Diameter
Length
Cost/Foot
Cost
(C FS)
-
(Feet)
($)
($)
1-4 23
24 IN
800.
$ 96
$ 172,800
50
27 IN
600
108
64,800
81
30 IN
250
120
30,000
1-9 679
90 IN
4510
360
1,623,600
1-10 60
36 IN
1340
144
192,960
1
1 1-11 281
36 IN
660
144
95,040
1-12 145
36 IN
700
144
100,800
TOTAL COST DRAINAGE AREA #1
$2,280,000
,f
DRAINAGE AREA #2
,,. Line # Flow
Diameter
Length
Cost/Foot
Cost
(CFS)
(Feet)
($)
($)
,. 2-1 62
30 IN
910
$ 120
$109,200
2-6 123
39IN
510
156
79,560
103
33 IN
340
132
44,880
85
30 IN
315
120
37,800
68
27 IN
350
108
37,800
TOTAL COST DRAINAGE AREA #2
$309,240
21
DRAINAGE AREA #3
Line # Flow
(CFS)
Diameter Length Cost/Foot Cost
(Feet) ($) ($)
I 3-1 421
60 IN
850
$ 240
$ 2041000
350
54IN
1650
216
356,400
102
36IN
3000
144
432,000
51
30 1N
500
120
60,000
3-2A 102
36IN
600
144
86,400
18
24 IN
500
96
48,000
3-2 183
48 IN
1075
192
206,400
96
36IN
275
144
39,600
59
24 IN
565
96
54,240
3-3 40
24 IN
1175
96
112,800
t
3-4 126
36IN
600
144
86,400
16
24 IN
250
96
24,000
Outlet Structures
1 EA
50,000
50,000
TOTAL COST DRAINAGE AREA #3
$1,760,240
DRAINAGE AREA #4
= Line # Flow
Diameter
Length
Cost/Foot
Cost
(CFS)
(Feet)
($)
($)
4-1 222
42 IN
1750
$ 168
$ 294,000
50
24 IN
1000
96
96,000
4-2 741
90IN
1320
384
506,880
4-3 946
90 IN
1120
384
430,080
Outlet Structures
1 EA
50,000
50,000
TOTAL COST DRAINAGE AREA #4
$1,555,280
22
DRAINAGE AREA #5
Line # Flow
(CFS)
Diameter Length Cost/Foot Cost
(Feet) ($) ($)
5-1 368
60IN
900
$ 240
$ 216,000
58
30 IN
1000
120
120,000
5-4 160
42IN
2000
$ 168
$ 336,000
70
36IN
400
144
57,600
5 5 395
66 IN
2250
264
594,000
374
60IN
2850
240
684,000
65
24 IN
550
96
52,800
5-6 255
57IN
670
228
152,760
241
54IN
1200
216
259,200
105
42IN
750
168
126,000
21
24 IN
1710
96
164,160
5-7 322
66IN
650
264
174,600
288
60IN
2150
240
516,000
185
54IN
1150
216
248,400
74
36IN
1350
144
194,400
TOTAL COST DRAINAGE AREA #5
$3,892,920
DRAINAGE AREA #6
Line # Flow
(CFS)
Diameter Length Cost/Foot Cost
(Feet) ($) ($)
6-1 A 443 54IN
1950
$ 216
$ 421,200
79 36IN
1350
144
194,400
30 24 IN
1200
96
115,200
6-2 196 39 IN
4050
156
631,800
6-3 25 24 IN
850
96
81,600
64 79 33IN
1350
132
178,200
Outlet Structures 1 EA
50,000
50,000
TOTAL COST DRAINAGE AREA #6
$1,672,400
23
DRAINAGE AREA #7
Line # Flow
(CFS)
Diameter Length Cost/Foot Cost
(Feet) ($) ($)
7-1 193 361N 2400- $ 144 $ 345,600
r� 7-2 23 24 IN 950 96 91,200
Outlet Structures 2 EA 30,000 60,000
TOTAL COST DRAINAGE AREA #7 $496,800
DRAINAGE AREA #8
Line # Flow
(CFS)
Diameter Length Cost/Foot Cost
(Feet) ($) ($)
8-1 17 24 IN 4200 $ 96 $403,200
r Outlet Structures 1 EA 30,000 30,000
w.. TOTAL COST DRAINAGE AREA #8 $433,200
DRAINAGE AREA #9
Line # Flow
(CFS)
Diameter Length Cost/Foot Cost
(Feet) ($) ($)
9-1 22 27 IN 3100 $ 108 $ 334,800
9-2 42 331N 7000 132 924,000
9-3 61 36IN 1600 144 230,400
TOTAL COST DRAINAGE AREA #9 $1,489,200
DRAINAGE AREA #10
Line # Flow
(CFS)
Diameter Length Cost/Foot Cost
(Feet) ($) ($)
10-1 61 36IN 3450 $ 144 $496,800
Retention Basin 1 EA 300,000 300,000
TOTAL COST DRAINAGE AREA #10 $796,800
24
r DRAINAGE AREA #11
' Line # Flow
Diameter
Length
Cost/Foot
Cost
(CFS)
(Feet)
($)
($)
11-1 337
78 IN
2400
$ 312
$ 748,800
226
60IN
2850'
240
684,000
88
36IN
1300
144
187,200
17
27IN
1900
108
205,200
-
11-2 134
36 IN
3800
144
547,200
11-3 269
60 IN
800
240
192,000
127
42IN
1250
168
210,000
24
24 IN
800
96
76,800
Retention Basin
1 EA
300,000
300,000
**********************************************************************
TOTAL COST DRAINAGE AREA #11
$3,151,200
MID -VALLEY CHANNEL
Line # Flow
Diameter
Length
Cost/Foot
Cost
(CFS)
(Feet)
($)
($)
MID-1 621
20x6x1.5 CH
22000
$ 350
$ 7,700,000
MID-2 621
(3)54 IN
600
1,080
1,944,000
MID-3 653
20x6x1.5 CH
11200
350
3,920,000
MID-4 107
(3)39 IN
500
780
1,170, 000
MID-5 112
10x5x1.5 CH
3100
300
930,000
i MID-6 762
20x6x1.5 CH
2600
350
910,000
**********************************************************************
TOTAL COST FOR MID -VALLEY CHANNEL
$16,574,000
25
TOTAL FACILITY COST
$17,158,244
MASTER PLAN
131,500
ENGINEERING 15%
2,573,737
RIGHT-OF-WAY 5%
857,912
UTILITY RELOCATION 5%
857,912
CONTINGENCIES 10%
1.715.824
TOTAL ASSESSABLE ACRES = 4890
DRAINAGE FEE PER ACRE FOR TOTAL UNDEVELOPED AREA
*DRAINAGE AREA # 11 AND MID -VALLEY CHANNEL NOT INCLUDED
IN TOTAL FACILITIES COST
**BASED ON COACHELLA VALLEY WATER DISTRICT UNIT PRICES
1992 DOLLARS - ENR 20 CITIES INDEX FOR JANUARY 1, 1992; 4,885.03
23,295,129*
$4,764**
PRIORITY
4
6-1
6
RECOMMENDED PRIORITY LIST
DESCRIPTION
Deficiency: The inability of the Fred Waring storm drain to convey runoff
Exhibit 2.1 generated along Highway 74 north of Grapevine Street to Fred
Waring Drive.
Recommendation: Install Lines 1 through 1 12 to convey the runoff flowing down
Monterey Avenue to the Whitewater Channel, thus bypassing
the Fred Waring Drive storm drain.
Deficiency: Lack of storm drain facilities to divert runoff generated in
Exhibit 2.3 Drainage Area #3 and #4 from passing into Indian Wells.
Recommendation: Install Line 3-1,Une 4-1, line 4-2, and Line 4-3 to convey this
runoff to the Whitewater Channel.
Deficiency: Lack of sufficient drainage facilities between El Paseo and
Exhibit 2.1 Highway 111 from Lupine Lane to San Luis Rey Avenue.
Recommendation: Install a series of pipes and catch basins to collect and convey
runoff north to the existing Line 1-4 located in the north
frontage road of Highway 111.
Deficiency: Lack of storm drain interceptors on Highway 74 to divert flows
Exhibit 2.1 A to the Palm Valley Channel, south of El Paseo in Drainage Area
#1 A.
Recommendation: Install four interceptor systems located along Highway 74 south
of El Paseo, Lines 1 A-3 through 1 A-6.
Deficiency: Cook Street's inability to convey runoff generated in Drainage
Exhibit 3.6 Area # 6 to the Whitewater Channel.
Recommendation: Install Line 6-1 through 6-4 within this area will sufficiently
convey runoff to the Whitewater Channel.
Deficiency: Lack of drainage facilities in Deep Canyon Road north of Fred
Exhibit 2.3 Waring Drive.
Recommendation: Install Line 3-4 to convey runoff generated within the interior
streets west Deep Canyon Road to the Whitewater Channel.
27
7 Deficiency:
Exhibit 3.5
Recommendation:
r "i8 Deficiency:
Exhibit 3
Recommendation:
Lack of drainage facilities on Country Club Drive just east of
Monterey. Avenue.
Complete the remainder of the proposed drainage facility from
Hovley Lane West to Country Club Drive (Line 5-4)
A major channel to convey runoff generated in Zone 3.
Incorporate the construction of the proposed Mid -Valley
Channel with the implementation of the Master Drainage Plan.
9 Deficiency: Lack of draiange facilities on Monterey Avenue from
Homestead
Exhibit 2.1 Road to the Whitewater Channel.
r. Recommendation: Vllide range of solutions including detention basin and altemate
storm drains that require discussion with adjacent land owners
` and CVWD. An annual review of this deficiency will be
-, conducted to evaluate and compare alternative solutions.
DRAINAGE FEES
An essential requirement for the implementation of the Master Drainage Plan is a
mechanism to provide project funding. Once a Master Plan has been adopted, positive
steps must be taken to provide adequate monies to construct the proposed facilities.
It is evident that no single method of funding will provide an adequate source of money
for the implementation of this Master Plan. Therefore, it is recommended that the City
consider a combination of funding methods to insure that adequate funds are made
available for the construction of the previously described facilities.The following
discussion outlines a number of possible financing methods.
PRESENT PRACTICES
• General Fund
One source of funds that is legally available for the construction of Master Plan
facilities is the City's General Fund. Considered as a limited source of revenue,
the use of these funds for the construction of drainage facilities would be a low
priority when compared to the tremendous demand for funding of necessary
services.
28
Drainage Fees
] Under the provisions of the government code of the State of California, a local
1 government or regulatory agency may adopt a program for the collection of
drainage fees. The Subdivision Map Act -enables the City to enact the drainage
fee program after certain prerequisites have been satisfied. The requirements for
the drainage fee program include:
Adoption of a Master Drainage Plan for each local drainage area.
2. Certification of the Master Drainage Plan by the legislative body of the
County and/or Special District having a Countywide and/or Districtwide
drainage plan.
3. Adoption of a fee structure based on the cost of the required facilities for
�i each drainage area and equitably proportioned to all affected properties.
4. Establishment of local drainage facilities funds.
Following the adoption of the appropriate ordinances, drainage fees can be collected
from developers as a condition of approval of final subdivision maps. Funds are then
deposited in the appropriate "Local Drainage Facilities Funds". As funds accumulate,
they may be expended for engineering, administrative and construction costs of the
k_
drainage facilities to be constructed within a particular drainage area
• Federal State Assistance Programs
There are a number of Federal and State programs which provide financial
assistance to local governments for the development of needed facilities. The
City currently receives an allotment of funds under the Housing and Community
Development Act of 1974. These HCDA monies could be potentially utilized to
construct certain portions of the proposed drainage system. However, because
of the limited funding available and the demand for other community facilities, it
probably cannot be considered a primary source of funding. Many of the other
Federal programs are geared to assist communities with lower per capita incomes
or where the nature of the community is less urbanized.
,,j • Assessment Districts
Assessment district proceedings offer a variety of methods of financing storm
drain systems under the Acts of 1911, 1913, 1915, or other assessment
proceedings. Assessment district financing could be used for funding in local
drainage areas, particularly those which are now substantially developed.
�i
29
However, the establishment of an assessment district requires that the property
owners within the area recognize the problem and agree to the assessment
approach for facility financing.
Assessment districts, like most other methods of municipal financing, have been
affected by the passage of Proposition 13. Certain cases now being considered
by the courts may affect the viability of assessment proceedings for the funding
of future municipal improvements.
• Mello -Roos Community Facilities Act
The Mello -Roos Community Facilities Act of 1982 provides an altemative method
of financing certain public capital facilities. A community facilities district formed
under a Mello -Roos is established for the purpose of carrying specific activities
of a public project.
A "Community Facilities District" is defined as the district of land in which public
facilities and authorized services are to be provided, and in which special taxes
and charges may be levied pursuant to the Mello -Roos Community Facilities Act
to pay for those facilities and services.
• Redevelopment, Agency
In theory, the Redevelopment District's tax is frozen to all taxing agencies within
the boundaries of the District. As assessed valuation increases due to
redevelopment, the increased taxes that result are funneled to the Redevelopment
Agency for their use. These tax increment funds can be used by the
Redevelopment Agency for eligible projects.
In present practice however, most taxing agencies will not agree to receiving only
the frozen tax base amount. Instead "pass thru" agreements are entered into by
the Redevelopment Agency in order to get the Redevelopment District formed.
LJ These pass through agreements entitle the existing taxing agencies to their fair
share of the tax increment funds. This pass through of funds to existing taxing
agencies dilutes the amount of the tax increment funds available to the
Redevelopment District.
At present, two Redevelopment Project Areas exist within the City, with a third
expected to be approved by mid-1991 and a fourth Redevelopment Project Area
in the feasibility stage.
Redevelopment Project Area No.1 parallels State Highway 111 from the eastern
City boundary to State Highway 74, then the area spreads out until it reaches the
western City boundary.
30
J
Redevelopment Areas No. 2, No. 3, and proposed No. 4, encompass
approximately 9010% of the City's land between 1-10 and the Whitewater Channel.
RECOMMENDED FEE STRUCTURE
In the case of the City of Palm Desert, a drainage fee program could be utilized to
establish a cost per gross acre of undeveloped land to be assessed as the land
develops. Based on a total undeveloped acreage of 4,890 acres and a total Master Plan
cost of $23,295,129 , the applicable acreage fee has been divided among two drainage
basins. The first drainage basin is comprised of Zones 1 & 2 and drains directly to the
Whitewater Channel. A drainage fee of $4,000 per acre is recommended Zone 1 and
$1,500 per acre is recommended for Zone 2.
The second drainage basin is comprised of Zones 3 & 4 and drains directly to the
proposed Mid -Valley Channel. Zone 4 is for reference only and, therefore, no
construction costs have been allocated at this time. Based on the cost of proposed
drainage facilities, a drainage fee per acre of $1,000 is recommended for Zone 3. These
costs are based on the ENR 20 cities index for January 1, 1992.
31
APPENDIX A
INCREMENTAL RUNOFF ANALYSIS
AND
RETENTION BASIN SIZES
INCREMENTAL RUNOFF ANALYSIS
AND RETENTION BASIN SIZES
The following tables represent the incremental runoff analysis demonstrating on -site
retention for 10-, 25-, 50-, and 100-year storms for 5-acre, single-family residential
development and 0.25-acre commercial development. The storage volume required for
each storm return period is noted in Table 1.
Within a 5-acre residential development approximately 23 lots of 8,000 square feet can
be constructed. This figure is derived by allowing 15% of the total area to be used for
roads and open space. Table 2 represents the storage basin sizes for each return
period. From this table it is summarized that 1 lot per 5-acre development can
accommodate the storage volume required. The storage volume provided in the table
represents a standard 80' x 100' lot with a 15' wide maintenance road around the basin.
The length and width of the basins remain the same with only the depth changing
accordingly.
Appendix B graphically represents the storage volume required in cubic feet per acre,
for both residential and commercial developments.
Appendix C represents runoff generated for residential development of 5 acres.
Developed runoff and undeveloped runoff are shown graphically with the use of a bar
chart.
J
J.
TABLE-1
INCREMENTAL RUNOFF ANALYSIS
VOLUME REQUIREMENT
Storm
Event
Time
Return
Undev.
Dev.
of
Storage
Storage
Period
Flow
Flow
Concen.
Required
Required
(Years)
(CFS)
(CFS)
(Min.)
(Cu. Ft.)
(CF/Acre)
Residential Development * 5-Acre Drainage
Areas
10
5.23
9.92
11.52
3243
649
25
6.79
12.32
11.52
3823
765
50
8.38
14.72
11.52
4383
877
100
9.82
16.85
11.52
4860
972
Commercial
Development * 1
/4 Acre Drainage Areas
10
0.41
0.92
5.00
153
612
25
0.53
1.12
5.00
177
708
50
0.64
1.32
5.00
204
816
100
0.75
1.51
5.00
228
912
TABLE-2
INCREMENTAL RUNOFF ANALYSIS
RETENTION BASIN SIZES
Storm Storage Volume Storage Volume
Event Required (CFS) Provided (CFS)
(Years)
Residential Development * 5-Acre Development
10 3243 3500
25 3823 4375
50 4383 5250
100 4860 7000
Commercial Development * 1 /4 Acre Development
10 153 187.5
25 177 199.5
50 204 225.0
100 228 262.5
APPENDIX B
CITY OF PALM DESERT
REQUIRED STORAGE BY LAND USAGE
I
City of Palm Desert
Required Storage by Land Usage
n
L 0.8
V
Q
L
0 0,7
CL
L 0,6
u�
0,5
Or
a
a
o M
D
L
° 0,2
M
� WAWAW.= Mk'Mi-0i WAWAW,=Ml�'gk-W� WAWAWAM WA WA Ww
10 25 50
Storm Event Return Period (Years)
® Residential Commercial
100
APPENDIX C
CITY OF PALM DESERT
INCREMENTAL RUNOFF ANALYSIS - RESIDENTIAL
W
kL
V
n
17
16
15
14
13
12
11
10
7
8
7
6
5
4
3
2
�f
City of Palm Desert
Incremental Runoff Analysis —Residential
10 25 50
Storm Event Return Period (Years)
ZZI Developed ® Undeveloped
RATIONAL METHOD HYDROLOGY COMPUTER PROGRAM BASED ON
RIVERSIDE COUNTY FLOOD CONTROL & WATER CONSERVATION DISTRICT
(RCFC&WCD) 1978 HYDROLOGY MANUAL
«««««««««««««««««««»»»»»»»»»»»»»»»»»»»
(C) Copyright 1982,1'986 Advanced Engineering Software [AES]
Especially prepared for:
NBS/LOWERY ENGINEERS & PLANNERS
<<<<<<<<«« <<<<<<<<«««««« ««« »»» >>>>>>>>>>>>>>»» >>>>>>>>>>>>>>
**********DESCRIPTION OF RESULTS********************************************
{ * PALM DESERT INCREMENTAL RUNOFF ANALYSIS
* 10 YEAR EVENT UNDEVELOPED VS. DEVELOPED(COMMERCIAL)
* 10/10/90
----------------------------------------------------------------------------
USER SPECIFIED HYDROLOGY AND HYDRAULIC MODEL INFORMATION:
----------------------------------------------------------------------------
USER SPECIFIED STORM EVENT(YEAR) = 10.00
SPECIFIED MINIMUM PIPE SIZE(INCH) = 18.00
SPECIFIED PERCENT OF GRADIENTS(DECIMAL) TO USE
FOR FRICTION SLOPE _ .95
10-YEAR STORM 10-MINUTE INTENSITY(INCH/HOUR) =
2.770
10-YEAR STORM 60-MINUTE INTENSITY(INCH/HOUR) =
.980
100-YEAR STORM 10-MINUTE INTENSITY(INCH/HOUR)
= 4.520
100-YEAR STORM 60-MINUTE INTENSITY(INCH/HOUR)
= 1.600
SLOPE OF 10-YEAR INTENSITY -DURATION CURVE _
.5799047
SLOPE OF 100-YEAR INTENSITY -DURATION CURVE _
.5796024
COMPUTED RAINFALL INTENSITY DATA:
STORM EVENT = 10.00 1-HOUR INTENSITY(INCH/HOUR)= .9898
SLOPE OF INTENSITY DURATION CURVE = .5799
RCFC&WCD HYDROLOGY MANUAL "C"-VALUES USED
«««««««««««««««««««»»»»»»»»»»»»»»»»»»»
Advanced Engineering Software [AES]
SERIAL No. 100971
VER. 3.3C RELEASE DATE: 2/20/86
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>»» >>>>>>>>>>»»»
--FLOW PROCESS FROM NODE 90.00 TO NODE 85.00 IS CODE = 2
-------------------------------------------------------------------------
»»>RATIONAL METHOD INITIAL SUBAREA ANALYSIS ««<
ASSUMED INITIAL SUBAREA UNIFORM
DEVELOPMENT IS: UNDEVELOPED WITH FAIR COVER
TC = K*[(LENGTH**3)/(ELEVATION CHANGE)]**.2
INITIAL SUBAREA FLOW -LENGTH = 150.00
UPSTREAM ELEVATION = 100.00
DOWNSTREAM ELEVATION = 97.00
ELEVATION DIFFERENCE = 3.00
10.00 YEAR RAINFALL INTENSITY(INCH/HOUR) = 2.578
SOIL CLASSIFICATION IS "B"
UNDEVELOPED WATERSHED RUNOFF COEFFICIENT = .6400
SUBAREA RUNOFF(CFS) = .41
TOTAL AREA(ACRES) = .25 TOTAL RUNOFF(CFS) _ .41
FLOW PROCESS FROM NODE 80.00 TO NODE 75.00 IS CODE = 2
----------------------------------------------------------------------------
r� r�»»>RATIONAL-METHOD_INITIAL�SUBAREA-ANALYSIS<<<<< ------------------`-'
ASSUMED INITIAL SUBAREA UNIFORM
DEVELOPMENT IS COMMERCIAL
TC = K*[(LENGTH**3)/(ELEVATION CHANGE)]**.2
INITIAL SUBAREA FLOW -LENGTH = 150.00
UPSTREAM ELEVATION = 100.00
DOWNSTREAM ELEVATION = 97.00
ELEVATION DIFFERENCE = 3.00
TC = .303*[( 150.00**3)/( 3.00)]**.2 = 4.918
COMPUTED TIME OF CONCENTRATION INCREASED TO 5 MIN.
10.00 YEAR RAINFALL INTENSITY(INCH/HOUR) = 4.182
SOIL CLASSIFICATION IS "B"
COMMERCIAL DEVELOPMENT RUNOFF COEFFICIENT = .8820 -
SUBAREA RUNOFF(CFS) _ .92
TOTAL AREA(ACRES) _ .25 TOTAL RUNOFF(CFS) .92
1 END OFRATIONALMETHOD ANALYSIS
RATIONAL METHOD HYDROLOGY COMPUTER PROGRAM BASED ON
RIVERSIDE COUNTY FLOOD CONTROL & WATER CONSERVATION DISTRICT
(RCFC&WCD) 1978 HYDROLOGY MANUAL
«««««««««««««««««««»»»»»»»»»»»»»»»»»»»
(C) Copyright 1982,1986 Advanced Engineering Software [AES]
Especially prepared for:
NBS/LOWERY ENGINEERS & PLANNERS
«« <<<<<<<<<<<<C < <<<<<<<<«« <<<<<<<<»» »»»» »» >>>>>>>>>>>>>>»» >>>>
**********DESCRIPTION OF RESULTS********************************************
* PALM DESERT INCREMENTAL RUNOFF ANALYSIS
* 25 YEAR EVENT UNDEVELOPED VS. DEVELOPED(COMMERCIAL)
* 10/10/90
----------------------------------------------------------------------------
USER SPECIFIED HYDROLOGY AND HYDRAULIC MODEL
----------------------------------------------------------------------------
INFORMATION:
-
USER SPECIFIED STORM EVENT(YEAR) = 25.00
SPECIFIED MINIMUM PIPE SIZE(INCH) = 18.00
r
SPECIFIED PERCENT OF GRADIENTS(DECIMAL) TO USE
FOR FRICTION SLOPE _ .95
.�
10-YEAR STORM 10-MINUTE INTENSITY(INCH/HOUR)
= 2.770
10-YEAR STORM 60-MINUTE INTENSITY(INCH/HOUR)
= .980
100-YEAR STORM 10-MINUTE INTENSITY(INCH/HOUR)
= 4.520
100-YEAR STORM 60-MINUTE INTENSITY(INCH/HOUR)
= 1.600
SLOPE OF 10-YEAR INTENSITY -DURATION CURVE _
.5799047
SLOPE OF 100-YEAR INTENSITY -DURATION CURVE _
.5796024
r�
COMPUTED RAINFALL INTENSITY DATA:
STORM EVENT = 25.00 1-HOUR INTENSITY(INCH/HOUR) = 1.2027
SLOPE OF INTENSITY DURATION CURVE = .5799
J
RCFC&WCD HYDROLOGY MANUAL "C"-VALUES USED
«««««««««««««««««««»»»»»»»»»»» »»»»»»»»
Advanced Engineering Software [AES]
SERIAL No. 100971
VER. 3.3C RELEASE DATE: 2/20/86
«««««««««««««««««««»»»»»»»»»»»»»»»»»»»
****************************************************************************
FLOW PROCESS FROM NODE 90.00 TO NODE 85.00 IS CODE = 2
----------------------------------------------------------------------------
»»>RATIONAL METHOD INITIAL SUBAREA ANALYSIS««<
---------------
ASSUMED INITIAL SUBAREA UNIFORM
DEVELOPMENT IS: UNDEVELOPED WITH FAIR COVER
TC = K*[(LENGTH**3)/(ELEVATION CHANGE)]**.2
INITIAL SUBAREA FLOW -LENGTH = 150.00
UPSTREAM ELEVATION = 100.00
DOWNSTREAM ELEVATION = 97.00
ELEVATION DIFFERENCE = 3.00
25.00 YEAR RAINFALL INTENSITY(INCH/HOUR) = 3.133
SOIL CLASSIFICATION IS "B"
UNDEVELOPED WATERSHED RUNOFF COEFFICIENT = .6745
SUBAREA RUNOFF(CFS) _ .53
TOTAL AREA(ACRES) _ .25 TOTAL RUNOFF(CFS) _ .53
FLOW PROCESS FROM NODE 80.00 TO NODE 75.00 IS CODE = 2
----------------------------------------------------------------------------
»»>RATIONAL METHOD INITIAL SUBAREA ANALYSIS ««<
ASSUMED INITIAL SUBAREA UNIFORM
DEVELOPMENT IS COMMERCIAL
TC = K*[(LENGTH**3)/(ELEVATION CHANGE)]**.2
INITIAL SUBAREA FLOW -LENGTH = 150.00
UPSTREAM ELEVATION = 100.00
DOWNSTREAM ELEVATION = 97.00
ELEVATION DIFFERENCE = 3.00
TC = .303*(( 150.00**3)/( 3.00)]**.2 = 4.918
COMPUTED TIME OF CONCENTRATION INCREASED TO 5 MIN.
25.00 YEAR RAINFALL INTENSITY(INCH/HOUR) = 5.081
SOIL CLASSIFICATION IS "B"
COMMERCIAL DEVELOPMENT RUNOFF COEFFICIENT = .8846
SUBAREA RUNOFF(CFS) = 1.12
TOTAL AREA(ACRES) = .25 TOTAL RUNOFF(CFS) = 1.12
END OF RATIONAL METHOD ANALYSIS
RATIONAL METHOD HYDROLOGY COMPUTER PROGRAM BASED ON
RIVERSIDE COUNTY FLOOD CONTROL & WATER CONSERVATION DISTRICT
(RCFC&WCD) 1978 HYDROLOGY MANUAL
«««««««««««««««««««»»»»»»»»»»»»»»»»»»»
(C) Copyright 1982,1986 Advanced Engineering Software [AES]
Especially prepared for:
NBS/LOWERY ENGINEERS & PLANNERS
«« <<««««««« «««««««« <<»»»»» »» »»» >>>>>>»»»»» >>
**********DESCRIPTION OF RESULTS********************************************
* PALM DESERT INCREMENTAL RONOFF ANALYSIS
* 50 YEAR EVENT UNDEVELOPED VS. DEVELOPED(COMMERCIAL)
* 10/10/90
USER SPECIFIEDHYDROLOGYAND HYDRAULIC MODEL INFORMATION:
USER SPECIFIED STORM EVENT(YEAR) = 50.00
SPECIFIED MINIMUM PIPE SIZE(INCH) = 18.00
SPECIFIED PERCENT OF GRADIENTS(DECIMAL) TO USE
FOR FRICTION SLOPE _ .95
10-YEAR STORM 10-MINUTE INTENSITY(INCH/HOUR) =
2.770
10-YEAR STORM 60-MINUTE INTENSITY(INCH/HOUR) =
.980
100-YEAR STORM 10-MINUTE INTENSITY(INCH/HOUR)
= 4.520
100-YEAR STORM 60-MINUTE INTENSITY(INCH/HOUR)
= 1.600
SLOPE OF 10-YEAR INTENSITY -DURATION CURVE _
.5799047
SLOPE OF 100-YEAR INTENSITY -DURATION CURVE _
.5796024
COMPUTED RAINFALL INTENSITY DATA:
STORM EVENT = 50.00 1-HOUR INTENSITY(INCH/HOUR) = 1.4134
SLOPE OF INTENSITY DURATION CURVE = .5798
RCFC&WCD HYDROLOGY MANUAL "CIO -VALUES USED
«««««««««««««««««««»»»»»»»»»»»»»»»»»»»
- Advanced Engineering Software [AES]
SERIAL No. 100971
VER. 3.3C RELEASE DATE: 2/20/86
«««««««««««««««««««»»»»»»»»»»»»»»»»»»»
****************************************************************************
FLOW PROCESS FROM NODE 90.00 TO NODE 85.00 IS CODE = 2
-----------------------------------------------------------------------------
»»>RATIONAL METHOD INITIAL SUBAREA ANALYSIS ««<
,} ASSUMED INITIAL SUBAREA UNIFORM
DEVELOPMENT IS: UNDEVELOPED WITH FAIR COVER
TC = K*[(LENGTH**3)/(ELEVATION CHANGE)]**.2
INITIAL SUBAREA FLOW -LENGTH = 150.00
UPSTREAM ELEVATION = 100.00
DOWNSTREAM ELEVATION = 97.00
ELEVATION DIFFERENCE = 3.00
50.00 YEAR RAINFALL INTENSITY(INCH/HOUR) = 3.681
SOIL CLASSIFICATION IS "B"
UNDEVELOPED WATERSHED RUNOFF COEFFICIENT = .7006
SUBAREA RUNOFF(CFS) _ .64
TOTAL AREA(ACRES) = .25 TOTAL RUNOFF(CFS) _ .64
FLOW PROCESS FROM NODE 80.00 TO NODE 75.00 IS CODE = 2
»»>RATIONAL METHOD INITIAL SUBAREA ANALYSIS««<
ASSUMED INITIAL SUBAREA UNIFORM
DEVELOPMENT IS COMMERCIAL
TC = K*[(LENGTH**3)/(ELEVATION CHANGE)]**.2
INITIAL SUBAREA FLOW -LENGTH = 150.00
UPSTREAM ELEVATION = 100.00
DOWNSTREAM ELEVATION = 97.00
ELEVATION DIFFERENCE = 3.00
TC = .303*[( 150.00**3)/( 3.00)]**.2 = 4.918
COMPUTED TIME OF CONCENTRATION INCREASED TO 5 MIN.
50.00 YEAR RAINFALL INTENSITY(INCH/HOUR) = 5.969
SOIL CLASSIFICATION IS "B"
COMMERCIAL DEVELOPMENT RUNOFF COEFFICIENT = .8866
SUBAREA RUNOFF(CFS) = 1.32
TOTAL AREA(ACRES) _ .25 TOTAL RUNOFF(CFS) = 1.32
END OF RATIONAL METHOD ANALYSIS
RATIONAL METHOD HYDROLOGY COMPUTER PROGRAM BASED ON
RIVERSIDE COUNTY FLOOD CONTROL & WATER CONSERVATION DISTRICT
(RCFC&WCD) 1978 HYDROLOGY MANUAL
«««««««««««« «««««««»»»»»»»»»»»»»»»»»»»
(C) Copyright 1982,1986 Advanced Engineering Software [AES]
Especially prepared for:
NBS/LOWERY ENGINEERS & PLANNERS
«««««««««««««««««««»»»»»»»»»»»»»»»»»»»
**********DESCRIPTION OF RESULTS********************************************
.` * PALM DESERT INCREMENTAL RUNOFF ANALYSIS
* 100 YEAR EVENT UNDEVELOPED VS. DEVELOPED (COMMERCIAL)
* 10/10/90
-----------------------------------------------------------------------------
USER SPECIFIED HYDROLOGY AND HYDRAULIC MODEL INFORMATION:
USER SPECIFIED STORM EVENT(YEAR) = 100.00
SPECIFIED MINIMUM PIPE SIZE(INCH) = 18.00
SPECIFIED PERCENT OF GRADIENTS(DECIMAL) TO USE FOR FRICTION SLOPE _ .95
10-YEAR STORM 10-MINUTE INTENSITY(INCH/HOUR) = 2.770
10-YEAR STORM 60-MINUTE INTENSITY(INCH/HOUR) = .980
100-YEAR STORM 10-MINUTE INTENSITY(INCH/HOUR) = 4.520
100-YEAR STORM 60-MINUTE INTENSITY(INCH/HOUR) = 1.600
SLOPE OF 10-YEAR INTENSITY -DURATION CURVE _ .5799047
SLOPE OF 100-YEAR INTENSITY -DURATION CURVE _ .5796024
COMPUTED RAINFALL INTENSITY DATA:
STORM EVENT = 100.00 1-HOUR INTENSITY(INCH/HOUR) = 1.6000
SLOPE OF INTENSITY DURATION CURVE _ .5796
RCFC&WCD HYDROLOGY MANUAL "C"-VALUES USED
«««««««««««««««««««»»»»»»»»»»»»»»»»»»»
._J Advanced Engineering Software [AES]
SERIAL No. I00971
VER. 3.3C RELEASE DATE: 2/20/86
<<<<<<<<«« <<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>»»» >>>>>>>>»»» >>>>>>>>
FLOW PROCESS FROM NODE 90.00 TO NODE 85.00 IS CODE = 2
-------------------------------------------------------------------------------
»»>RATIONAL METHOD INITIAL SUBAREA ANALYSIS««<
ASSUMED INITIAL SUBAREA UNIFORM
DEVELOPMENT IS: UNDEVELOPED WITH FAIR COVER
TC = K*[(LENGTH**3)/(ELEVATION CHANGE)]**.2
INITIAL SUBAREA FLOW -LENGTH = 150.00
UPSTREAM ELEVATION = 100.00
DOWNSTREAM ELEVATION = 97.00
ELEVATION DIFFERENCE = 3.00
100.00 YEAR RAINFALL INTENSITY(INCH/HOUR} = 4.166
SOIL CLASSIFICATION IS "B"
UNDEVELOPED WATERSHED RUNOFF COEFFICIENT = .7192
SUBAREA RUNOFF(CFS) _ .75
TOTAL AREA(ACRES) _ .25 TOTAL RUNOFF(CFS) _ .75
FLOW PROCESS FROM NODE 80.00 TO NODE 75.00 IS CODE = 2
----------------------------------------------------------------------------
;�--»»>RATIONALrMETHOD_INITIAL-SUBAREA-ANALYSIS<<<<< _�-------------�`--�
ASSUMED INITIAL SUBAREA UNIFORM
DEVELOPMENT IS COMMERCIAL
TC = K*[(LENGTH**3)/(ELEVATION CHANGE)]**.2
INITIAL SUBAREA FLOW -LENGTH = 150.00
UPSTREAM ELEVATION = 100.00
4 DOWNSTREAM ELEVATION = 97.00
ELEVATION DIFFERENCE = 3.00
TC = .303*[( 150.00**3)/( 3.00)]**.2 = 4.918
COMPUTED TIME OF CONCENTRATION INCREASED TO 5 MIN.
100.00 YEAR RAINFALL INTENSITY(INCH/HOUR) = 6.755
SOIL CLASSIFICATION IS "Bit
COMMERCIAL DEVELOPMENT RUNOFF COEFFICIENT = .8879
SUBAREA RUNOFF(CFS) = 1.50
TOTAL AREA(ACRES) _ .25 TOTAL RUNOFF(CFS) = 1.50
END OF RATIONAL METHOD ANALYSIS
RATIONAL METHOD HYDROLOGY COMPUTER PROGRAM BASED ON
RIVERSIDE COUNTY FLOOD CONTROL & WATER CONSERVATION DISTRICT
(RCFC&WCD) 1978 HYDROLOGY MANUAL
«««««««««««««««««««»»»»»»»»»»»»»»»»»»»
(C) Copyright 1982,1986 Advanced Engineering Software [AES]
Especially prepared for:
NBS/LOWERY ENGINEERS & PLANNERS
rr <<<<<<<<«« <<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>»» >>>>>>>>>>»»»»» »»»
**********DESCRIPTION OF RESULTS********************************************
* PALM DESERT INCREMENTAL RUNOFF ANALYSIS
* 10 YEAR EVENT UNDEVLOPED VS. DEVELOPED(1/4 ACRE SINGLE FAMILY)
* 10/ 10/90
****************************************************************************
---------------------------------------------------------
USER SPECIFIED HYDROLOGY AND HYDRAULIC MODEL INFORMATION:
USER SPECIFIED STORM EVENT(YEAR) = 10.00
SPECIFIED MINIMUM PIPE SIZE(INCH) = 18.00
SPECIFIED PERCENT OF GRADIENTS(DECIMAL) TO USE
FOR FRICTION SLOPE _ .95
10-YEAR STORM 10-MINUTE INTENSITY(INCH/HOUR) =
2.770
10-YEAR STORM 60-MINUTE INTENSITY(INCH/HOUR) =
.980
100-YEAR STORM 10-MINUTE INTENSITY(INCH/HOUR)
= 4.520
100-YEAR STORM 60-MINUTE INTENSITY(INCH/HOUR)
= 1.600
SLOPE OF 10-YEAR INTENSITY -DURATION CURVE _
.5799047
SLOPE OF 100-YEAR INTENSITY -DURATION CURVE _
.5796024
COMPUTED RAINFALL INTENSITY DATA:
STORM EVENT = 10.00 1-HOUR INTENSITY(INCH/HOUR) _ .9898
SLOPE OF INTENSITY DURATION CURVE = .5799
RCFC&WCD HYDROLOGY MANUAL "CIO -VALUES USED
«««««««««««««««««««»»»»»»»»»»»»»»»»»»»
�.� Advanced Engineering Software [AES]
SERIAL No. 100971
VER. 3.3C RELEASE DATE: 2/20/86
«««««««««««««««««««»»»»»»»»»»»»»»»»»»»
****************************************************************************
+_FLOW PROCESS FROM NODE 90.00 TO NODE 85.00 IS CODE = 2
---- ..------- ----- ----- --------- _---_---- --------- -------- ---------_---------
»»>RATIONAL METHOD INITIAL SUBAREA ANALYSIS««<
ASSUMED INITIAL SUBAREA UNIFORM
DEVELOPMENT IS: UNDEVELOPED WITH FAIR COVER
TC = K*[(LENGTH**3)/(ELEVATION CHANGE)]**.2
INITIAL SUBAREA FLOW -LENGTH = 660.00
UPSTREAM ELEVATION = 100.00
DOWNSTREAM ELEVATION = 86.80
ELEVATION DIFFERENCE = 13.20
._1
10.00 YEAR RAINFALL INTENSITY(INCH/HOUR) = 1.829
SOIL CLASSIFICATION IS "B"
UNDEVELOPED WATERSHED RUNOFF COEFFICIENT = .5722
SUBAREA RUNOFF(CFS) = 5.23
TOTAL AREA(ACRES) = 5.00 TOTAL RUNOFF(CFS) = 5.23
FLOW PROCESS FROM NODE 80.00 TO NODE 75.00 IS CODE = 2
----------------------------------------------------------------------------
»»>RATIONAL METHOD INITIAL SUBAREA ANALYSIS««<
ASSUMED INITIAL SUBAREA UNIFORM
DEVELOPMENT IS SINGLE FAMILY (1/4 ACRE)
TC = K*[(LENGTH**3)/(ELEVATION CHANGE)]**.2
INITIAL SUBAREA FLOW -LENGTH = 660.00
UPSTREAM ELEVATION = 100.00
DOWNSTREAM ELEVATION = 86.80
ELEVATION DIFFERENCE = 13.20
TC = .393*[( 660.00**3)/( 13.20)]**.2 = 11.523
10.00 YEAR RAINFALL INTENSITY(INCH/HOUR) = 2.577
SOIL CLASSIFICATION IS "B"
SINGLE-FAMILY(1/4 ACRE LOT) RUNOFF COEFFICIENT = .7699
SUBAREA RUNOFF(CFS) = 9.92
TOTAL AREA(ACRES) = 5.00 TOTAL RUNOFF(CFS) = 9.92
END OF RATIONAL METHOD ANALYSIS
RATIONAL METHOD HYDROLOGY COMPUTER PROGRAM BASED ON
RIVERSIDE COUNTY FLOOD CONTROL & WATER CONSERVATION DISTRICT
(RCFC&WCD) 1978 HYDROLOGY MANUAL
«« <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<««»»» >>>>>>>>>>>>>>>>>>>>>>>>»»»»
(C) Copyright 1982,1986 Advanced Engineering Software [AES]
Especially prepared for:
NBS/LOWERY ENGINEERS & PLANNERS
Y-I<<<<<<<<<<<<<<<<<<<<<<<<<<<<<««««<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
**********DESCRIPTION OF RESULTS####**#*##*******#**###*###*****************
* PALM DESERT INCREMENTAL RUNOFF ANALYSIS
* 25 YEAR EVENT UNDEVELOPED VS. DEVELOPED(1\4 ACRE SINGLE FAMILY)
* 10/10/90
---------------------------------------------------------
USER SPECIFIED HYDROLOGY AND HYDRAULIC MODEL INFORMATION:
USER SPECIFIED STORM EVENT(YEAR) = 25.00
SPECIFIED MINIMUM PIPE SIZE(INCH) = 18.00
SPECIFIED PERCENT OF GRADIENTS(DECIMAL) TO USE
FOR FRICTION SLOPE _ .95
10-YEAR STORM 10-MINUTE INTENSITY(INCH/HOUR) =
2.770
10-YEAR STORM 60-MINUTE INTENSITY(INCH/HOUR) =
.980
100-YEAR STORM 10-MINUTE INTENSITY(INCH/HOUR)
= 4.520
100-YEAR STORM 60-MINUTE INTENSITY(INCH/HOUR)
= 1.600
SLOPE OF 10-YEAR INTENSITY -DURATION CURVE _
.5799047
SLOPE OF 100-YEAR INTENSITY -DURATION CURVE _
.5796024
COMPUTED RAINFALL INTENSITY DATA:
STORM EVENT = 25.00 1-HOUR INTENSITY(INCH/HOUR)
= 1.2027
SLOPE OF INTENSITY DURATION CURVE = .5799
RCFC&WCD HYDROLOGY MANUAL "C"-VALUES USED
«««««««««««««««««««»»»»»»»»»»»»»»»»»»»
.1 Advanced Engineering Software [AES]
SERIAL No. I00971
'j VER. 3.3C RELEASE DATE: 2/20/86
«« <<<<<<<<<<<<««« <<<<<<<<<<<<<<<<»»»» >>»» >>>>>>>>»»» >>>>>>>>>>
FLOW PROCESS FROM NODE 90.00 TO NODE 85.00 IS CODE = 2
----------------------------------------------------------------------------
»»>RATIONAL METHOD INITIAL SUBAREA ANALYSIS««<
----=====ASSUMED-INITIAL SUBAREA UNIFORM
DEVELOPMENT IS: UNDEVELOPED WITH FAIR COVER
TC = K*[(LENGTH**3)/(ELEVATION CHANGE)]**.2
INITIAL SUBAREA FLOW -LENGTH = 660.00
=' UPSTREAM ELEVATION = 100.00
DOWNSTREAM ELEVATION = 86.80
{ ELEVATION DIFFERENCE = 13.20
L:) . V V Il.lii[ Lwft.LL1rt11JL/ yaiL aJ11 a `tad\ aa/ aavva.� �.. c c c
SOIL CLASSIFICATION IS "B"
UNDEVELOPED WATERSHED RUNOFF COEFFICIENT = .6116
SUBAREA RUNOFF(CFS) = 6.79
TOTAL AREA(ACRES) = 5.00 TOTAL RUNOFF(CFS) = 6.79
•—�********,Ir****�k*�*�Ik******�rr�k**k*****�***��k**************te��e****�Ic********��Y�***
---
--FLOW PROCESS FROM NODE 80.00 TO NODE 75.00 IS CODE = 2
»»>RATIONAL METHOD INITIAL SUBAREA ANALYSIS««<
ASSUMED -INITIAL SUBAREA
-UNIFORM
---==--___^____-___-- -----
DEVELOPMENT IS SINGLE FAMILY (1/4 ACRE)
r� TC = K*[(LENGTH**3)/(ELEVATION CHANGE)]**.2
INITIAL SUBAREA FLOW -LENGTH = 660.00
UPSTREAM ELEVATION = 100.00
DOWNSTREAM ELEVATION = 86.80
ELEVATION DIFFERENCE = 13.20
TC = .393*(( 660.00**3)/( 13.20)]**.2 = 11.523
25.00 YEAR RAINFALL INTENSITY(INCH/HOUR) = 3.131
SOIL CLASSIFICATION IS "B"
j SINGLE-FAMILY(1/4 ACRE LOT) RUNOFF COEFFICIENT = .7872
SUBAREA RUNOFF(CFS) = 12.32
` --TOTAL -AREA(ACRES)-T------5_00--- TOTAL
-RUNOFF(CFS)-------12.32_-___-------^
END OF RATIONAL METHOD ANALYSIS
RATIONAL METHOD HYDROLOGY COMPUTER PROGRAM BASED ON
RIVERSIDE COUNTY FLOOD CONTROL & WATER CONSERVATION DISTRICT
(RCFC&WCD) 1978 HYDROLOGY MANUAL
«««««««««««««««««««»»»»»»»»»»»»»»»»»»»
(C) Copyright 19`82,'1986 Advanced Engineering Software [AES]
Especially prepared for:
NBS/LOWERY ENGINEERS & PLANNERS
<<<<<<<<<<<<<<<<<<<<«««««« «« <<>>>>>>»»» >>>>>>>>>>>>>>>>>>>>>>>>>>
**********DESCRIPTION OF RESULTS********************************************
* PALM DESERT INCREMENTAL RUNOFF ANALYSIS
* 50 YEAR EVENT UNDEVELOPED VS. DEVELOPED(1\4 ACRE SINGLE FAMILY)
* 10/10/90
****************************************************************************
---------------------------------------------------------
USER SPECIFIED HYDROLOGY AND HYDRAULIC MODEL INFORMATION:
USER SPECIFIED STORM EVENT(YEAR) = 50.00
SPECIFIED MINIMUM PIPE SIZE(INCH) - 18.00
SPECIFIED PERCENT OF GRADIENTS(DECIMAL) TO USE
FOR FRICTION SLOPE _ .95
10-YEAR STORM 10-MINUTE INTENSITY(INCH/HOUR) =
2.770
10-YEAR STORM 60-MINUTE INTENSITY(INCH/HOUR) _
.980
100-YEAR STORM 10-MINUTE INTENSITY(INCH/HOUR)
= 4.520
100-YEAR STORM 60-MINUTE INTENSITY(INCH/HOUR)
= 1.600
SLOPE OF 10-YEAR INTENSITY -DURATION CURVE _
.5799047
SLOPE OF 100-YEAR INTENSITY -DURATION CURVE _
.5796024
COMPUTED RAINFALL INTENSITY DATA:
STORM EVENT = 50.00 1-HOUR INTENSITY(INCH/HOUR) = 1.4134
SLOPE OF INTENSITY DURATION CURVE _ .5798
RCFC&WCD HYDROLOGY MANUAL "C"-VALUES USED
«««««««««««««««««««»»»»»»»»»»»»»»»»»»»
Advanced Engineering Software [AES]
SERIAL No. 100971
VER. 3.3C RELEASE DATE: 2/20/86
«««««««««««««««««««»»»»»»»»»»»»»»»»»»»
****************************************************************************
--FLOW PROCESS FROM NODE 90.00 TO NODE 85.00 IS CODE = 2
------------------------------------------------------- ---------------------
»»>RATIONAL METHOD INITIAL SUBAREA ANALYSIS««<
ASSUMED
-INITIAL SUBAREA UNIFORM
DEVELOPMENT IS: UNDEVELOPED WITH FAIR COVER
TC = K*[(LENGTH**3)/(ELEVATION CHANGE)]**.2
INITIAL SUBAREA FLOW -LENGTH = 660.00
UPSTREAM ELEVATION = 100.00
DOWNSTREAM ELEVATION = 86.80
ELEVATION DIFFERENCE = 13.20
f 5V. UV Yr.HtC Kil1Ni'HLLr 1N'1'�Nbl'1'Y {1NC:t1�tlVUltJ W l . bii '
SOIL CLASSIFICATION IS "B"
UNDEVELOPED WATERSHED RUNOFF COEFFICIENT = .6423
SUBAREA RUNOFF(CFS) = 8.38
TOTAL AREA(ACRES) = 5.00 TOTAL RUNOFF(CFS) = 8.38
FLOW PROCESS FROM NODE 80.00 TO NODE 75.00 IS CODE = 2
----------------------------------------------------------------------------
»»>RATIONAL METHOD INITIAL SUBAREA ANALYSIS««<
ASSUMED INITIAL SUBAREA UNIFORM
DEVELOPMENT IS SINGLE FAMILY (1/4 ACRE)
`l TC = K*[(LENGTH**3)/(ELEVATION CHANGE)]**.2
1 INITIAL SUBAREA FLOW —LENGTH = 660.00
UPSTREAM ELEVATION = 100.00
DOWNSTREAM ELEVATION = 86.80
ELEVATION DIFFERENCE = 13.20
TC = .393*[( 660.00**3)/( 13.20)]**.2 = 11.523
50.00 YEAR RAINFALL INTENSITY(INCH/HOUR) = 3.679
SOIL CLASSIFICATION IS "B"
SINGLE—FAMILY(1/4 ACRE LOT) RUNOFF COEFFICIENT = .8003
SUBAREA RUNOFF(CFS) = 14.72
TOTAL —AREA(ACRES)--------5-00�-- TOTAL _RUNOFF(CFS)14A72----��__-----
END OF RATIONAL METHOD ANALYSIS
a.�
' iGFiA1VIYHL i•1Tili1UL AiLLtLLvvi �viirutLa� ra�vvr,caa•a uA�uu va•
I RIVERSIDE COUNTY FLOOD CONTROL & WATER CONSERVATION DISTRICT
(RCFC&WCD) 1978 HYDROLOGY MANUAL
«««««««««««««««««««»»»»»»»»»»»»»»»»»»»
(C) Copyright 19'82,.1986 Advanced Engineering Software [AES]
Especially prepared for:
NBS/LOWERY ENGINEERS & PLANNERS
«««««««««««««««««««»»»»»»»»»»»»»»»»»»»
**********DESCRIPTION OF RESULTS********************************************
* PALM DESERT INCREMENTAL RUNOFF ANALYSIS
* 100 YEAR EVENT UNDEVELOPED VS. DEVELOPED(1\4 ACRE SINGLE FAMILY
J----------------------------------------------------------------------------
USER SPECIFIED HYDROLOGY AND HYDRAULIC MODEL INFORMATION:
----
--USER SPECIFIED STORM EVENT(YEAR)
----___
SPECIFIED MINIMUM PIPE SIZE(INCH) = 18.00
SPECIFIED PERCENT OF GRADIENTS(DECIMAL) TO USE
FOR FRICTION SLOPE _ .95
10-YEAR STORM 10-MINUTE INTENSITY(INCH/HOUR) =
2.770
�-
10-YEAR STORM 60-MINUTE INTENSITY(INCH/HOUR) =
.980
100-YEAR STORM 10-MINUTE INTENSITY(INCH/HOUR)
= 4.520
100-YEAR STORM 60-MINUTE INTENSITY(INCH/HOUR)
= 1.600
SLOPE OF 10-YEAR INTENSITY -DURATION CURVE _
.5799047
SLOPE OF 100-YEAR INTENSITY -DURATION CURVE _
.5796024
COMPUTED RAINFALL INTENSITY DATA:
STORM EVENT = 100.00 1-HOUR INTENSITY(INCH/HOUR)
= 1.6000
SLOPE OF INTENSITY DURATION CURVE = .5796
RCFC&WCD HYDROLOGY MANUAL "C"-VALUES USED
«««««««««««««««««««»»»»»»»»»»»»»»»»»»»
Advanced Engineering Software [AES]
SERIAL No. 100971
VER. 3.3C RELEASE DATE: 2/20/86
«««««««««««««««««««»»»»»»»»»»»»»»»»»»»
FLOW PROCESS FROM NODE 90.00 TO NODE 85.00 IS CODE = 2
»»>RATIONAL METHOD INITIAL SUBAREA ANALYSIS ««<
f� ASSUMED INITIAL SUBAREA UNIFORM -- -
:_' DEVELOPMENT IS: UNDEVELOPED WITH FAIR COVER
TC = K*{(LENGTH**3)/(ELEVATION CHANGE)]**.2
INITIAL SUBAREA FLOW -LENGTH = 660.00
UPSTREAM ELEVATION = 100.00
DOWNSTREAM ELEVATION = 86.80
ELEVATION DIFFERENCE = 13.20
SOIL CLASSIFICATION IS "B"
UNDEVELOPED WATERSHED RUNOFF COEFFICIENT = .6644
SUBAREA RUNOFF(CFS) = 9.82
TOTAL AREA(ACRES) = 5.00 TOTAL RUNOFF(CFS) = 9.82
FLOW PROCESS FROM NODE 80.00 TO NODE 75.00 IS CODE = 2
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»»>RATIONAL METHOD INITIAL SUBAREA ANALYSIS««<
ASSUMED INITIAL SUBAREA UNIFORM
DEVELOPMENT IS SINGLE FAMILY (1/4 ACRE)
TC = K*[(LENGTH**3)/(ELEVATION CHANGE)]**.2
INITIAL SUBAREA FLOW -LENGTH = 660.00
UPSTREAM ELEVATION = 100.00
DOWNSTREAM ELEVATION = 86.80
ELEVATION DIFFERENCE = 13.20
TC = .393*[( 660.00**3)/( 13.20)]**.2 = 11.523
100.00 YEAR RAINFALL INTENSITY(INCH/HOUR) = 4.163
SOIL CLASSIFICATION IS "B"
SINGLE-FAMILY(1/4 ACRE LOT) RUNOFF COEFFICIENT = .8095
SUBAREA RUNOFF(CFS) = 16.85
TOTAL AREA(ACRES) = 5.00 TOTAL RUNOFF(CFS) = 16.85
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:. END OF RATIONAL METHOD ANALYSIS
REFERENCES
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GLOSSARY OF TERMS
CFS Cubic Feet Per Second
Drainage Area The area that contributes storm flows to
a specific concentration point, or storm drain system
Hydrology A multi -disciplinary subject dealing with the occurrence,
circulation, and distribution of the waters of the Earth.
Peak Discharge The highest rate of storm runoff expressed in cubic feet per
second.
RCP Reinforced Concrete Pipe
Sub Area A smaller tributary area located within a drainage area.
25 & 100 year storm An annual maximum event whose peak discharge is equaled
or exceeded once, on the average, every 25 or 100 years,
respectively.
Standard Project Flood The discharge that may be expected from the most severe
combination of meteorologic and hydrologic conditions that
are considered reasonably characteristic of the geographical
region involved.