HomeMy WebLinkAbout2014-10-13 CSC Regular Meeting Agenda PacketCITY OF PALM DESERT
CITIZENS' SUSTAINABI�ITY COMMITTEEE
AGENDA
MONDAY, OCTOBER 13, 2014 — 2:00 P.M.
ADMINISTRATIVE CONFERENCE R�OM
73-510 FRED WARING DRIVE, PALM DESERT, CA 92260
CALL TO ORDER
II. ROLL CALL
III. ORAL COMMUNICATIONS
Any person wishing to discuss any item not otherwise on the Agenda may address the
Citizens' Sustainability Committee at this point by giving his/her name and address for
the record. Remarks shali be limited to a maximum of five minutes unless additional time
is authorized by the Committee. Because the Brown Act does not allow the Citizens'
Sustainability Committee to take action on items not on the Agenda, members will not
enter into discussion with speakers but briefly respond or instead refer the matter to staff
for report and recommendation at a future Citizen's Sustainability Committee meeting.
This is also the time and place for any person who wishes to comment on Agenda
items. It should be noted that at Citizen's Sustainability Committee discretion, these
comments may be deferred until such time on the agenda as the item is discussed.
Remarks shall be limited to a maximum of five minutes unless additional time is
authorized by the Citizens' Sustainability Committee.
Reports and documents relating to each of the following items listed on the agenda,
including those received following posting/distribution, are on file in the Office of the
Department of Community Development and are available for public inspection
during normal business hours, Monday-Friday, 8:00 a.m.-5:00 p.m., 73-510 Fred
Waring Drive, Palm Desert, CA 92260, telephone (760) 346-0611, Extension 484.
IV. CONSENT CALENDAR
ALL MATTERS LISTED ON THE CONSENT CALENDAR ARE CONSIDERED TO BE
ROUTINE AND WILL BE ENACTED BY ONE ROLL CALL VOTE. THERE WILL BE NO
SEPARATE DISCUSSION OF THESE ITEMS UNLESS MEMBERS OF THE CITIZENS'
SUSTAINABILITY COMMITTEE OR AUDIENCE REQUEST ITEMS BE REMOVED
FROM THE CONSENT CALENDAR FOR SEPARATE DISCUSSION AND ACTION
UNDER SECTION V CONSENT ITEMS HELD OVER, OF THE AGENDA.
A. MINUTES of the Citizens' Sustainability Committee meeting of May 12, 2014.
Rec: Approve as presented.
Action:
POSTED AGENDA
CITIZENS' SUSTAINABILITY COMMITTEE OCTOBER 13, 2014
V. CONSENT ITEMS HELD OVER
VI. NEW BUSINESS
A. PRESENTATION of Green Life Program (Nicole Criste, Terra Nova Planning &
Research)
Rec:
Action:
B. DISCUSSION of Parking Lot Shade Tree Standards (Tony Bagato, Principal
Planner)
Rec:
Action:
VII. CONTINUED BUSINESS
NONE
VIII. OLD BUSINESS
A. UPDATE on Single-Use Plastic Bags (Tony Bagato, Principal Planner)
Rec: Receive and file.
B. UPDATE on Water Conservation (Tony Bagato, Principal Planner)
Rec: Receive and file.
IX. REPORTS AND REMARKS
A. Committee Members Comments
X. ADJOURNMENT
I hereby certify under penalty of perjury under the laws of the State of California, that the
foregoing agenda for the Citizens' Sustainability Committee was posted on the City Hall
bulletin board not less than 72 hours prior to the meeting. Dated on this 9t" day of
October, 2014.
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Monica O'Reilly, Recording Sei�retary
...
Please contact fhe Planning Department, 73510 Fred Waring Drrve, Palm Desert, CA 92260, (760) 346-0611, for
assistance with access to any of the agenda, matenals, or participation at the meeting.
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CITY OF PALM DESERT
CITIZENS' SUSTAINABILITY COMITTEEE
PRELIMINARY MINUTES
MONDAY, MAY 12, 2014 — 2:00 P.M.
ADMINISTRATIVE CONFERENCE ROOM
73-510 FRED WARING DRIVE, PALM DESERT, CA 92260
Q
CALL TO ORDER
Chair Robert Leo called the meeting to order at 2:02 p.m.
II. ROLL CALL
Present:
Member Tom Edwards at 2:08 p.m.
Member Eric Corey Freed at 2:08 p.m
Member Dean Gatons
Member Gregory Gritters at 2:23 p.m.
Member Dennis Guinaw
�
Member Bruce Kassler
Member Courtney Lingle
Member Susan Rosenberg
Member Luke Taylor
Chair Robert Leo
Also Present:
Absent:
�
Member David Koller
Member David Mourhess
Member Ralph Raya
�
Van Tanner, Council Member
Susan Marie Weber, Council Member at 2:10 p.m.
John Wohlmuth, City Manager
Lauri Aylaian, Director of Community Development at 2:07 p.m.
Mark Greenwood, Director of Public Works
Tony Bagato, Principal Planner
Ruth Ann Moore, Economic Development Manager
Lisa Ream, Recycling Technician
Monica O'Reilly, Recording Secretary
Michelle Dan, Youth Committee Member
Jessica Kozlak, Youth Committee Member
Cassidy Quilling, Youth Committee Member
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CITIZENS' SUSTAINABILITY COMMITTEE
MAY 12, 2014
III. ORAL COMMUNICATIONS
Ms. Cassidy Quilling, Youth Committee member, communicated that she will be
attending Cal Poly in the fall. She said that two other Youth Committee members
will attend the Citizens' Sustainability meetings.
Ms. Michelle Dan and Ms. Jessica Kozlak, Youth Committee members,
introduced themselves to the Sustainability Committee.
IV. CONSENT CALENDAR
A. MINUTES of the Citizens' Sustainability Committee meeting of February 10,
2014.
Rec: Approve as presented.
� �
At the beginning of the meeting there was not a quorum to approve the minutes;
therefore, Chair Leo moved to New Business.
At 2:55 p.m., Chair Leo returned to the Consent Calendar for approval of the
minutes.
Upon a motion by Member Gatons, second by Member Taylor, and a 8-0-3-2
vote of the Citizens' Sustainability Committee (AYES: Edwards, Freed, Gatons, Gritters,
Kassler, Leo, Rosenberg, and Taylor; NOES: None; ABSENT: Koller, Mourhess, and
Raya; ABSTAIN: Guinaw and Lingle), the Consent Calendar was approved as
presented.
V. CONSENT ITEMS HELD OVER ��
None
VI. NEW BUSINESS
,�
A. SELECTION of Chairperson and Vice Chairperson
Member Guinaw moved, by Minute Motion, to nominate Chair Leo for another
year as Chairperson; and Member Rosenberg volunteered to serve as Vice
Chairperson. Motion was seconded by Member Gatons and carried by a 9-0-4 vote
(AYES: Edwards, Freed, Gatons, Guinaw, Kassler, Leo, Lingle, Rosenberg, and Taylor;
NOES: None; ABSENT: Gritters, Koller, Mourhess, and Raya)
B. WATER CONSERVATION (Tony Bagato, Principal Planner)
Mr. Tony Bagato, Principal Planner, stated that he emailed the City's water
efficient and landscape ordinances to the Sustainability Committee. He said that
he does not want to change the water efficient ordinance. However, he is looking
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PRELIMINARY MINUTES
CITIZENS' SUSTAINABILITY COMMITTEE
MAY 12, 2014
at changing the landscape ordinance for commercial, industrial, and residential.
He asked the Sustainability Committee if they had any comments.
Member Bruce Kassler commented that the ordinances currently in place are
good; however, there does not seem to be any policing once the landscape and
irrigation is constructed according to the approved landscape plans. For
example, a gardener will turn on the irrigation controller for an hour a day, four
times a day instead of five or ten minutes a day, two times a day. He said he
understands that the City is not able to check every water meter, but can there
be a program where there is some policing being done.
Member Luke Taylor said that the Coachella Valley Water District (CVWD) is
policing water use with the tier rate structure. He mentioned that he does
inspections for the County of Riverside. He explained that after landscape is
completed on county projects, they hold a bond for a year. After a year, he
perForms another inspection to make sure everything is working properly, and
check that the plant material was not replaced with high water use plant material.
Ms. Lauri Aylaian, Director of Community Development, asked Member Taylor if
bonds are held on private or public projects.
Member Taylor responded that bonds are held for public projects.
Member Eric Corey Freed mentioned that the City of Paso Robles created a
water offset program during a water state of emergency. He explained that a
certain amount of water is allocated to the customer. If the customer used less
than the allocated amount, they could give the offset amount to other people. If
the customer used more than the allocated amount, they had to pay for the
water.
Mr. Bagato stated that CVWD oversees water, and it would be CVWD's
responsibility to declare a water state of emergency.
Member Freed asked how much power the City has since there is a water
district.
Mr. John Wohlmuth, City Manager, responded that the City of Palm Desert
historically has designed public areas with drought tolerant landscape. He noted
that this was to done to demonstrate that drought tolerant landscape can look
good and be a theme in the City. He agreed with Member Taylor that CVWD's
tier rate structure is the best way to enforce water conservation. He mentioned
that CVWD has an offer for residents to have irrigation clocks replaced so that
they are programmed by month. Beginning July 1, the City is partnering with
CVWD on a turF buyback program. The City is also purchasing flags for all City
inspectors to carry in their vehicles. He explained that if an inspector sees a
broken irrigation head, it will be flagged. The City and CVWD's contact
information will be on the flag. Mr. Wohlmuth stated that it makes sense to tackle
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PRELIMINARY MINUTES
CITIZENS' SUSTAINABILITY COMMITTEE
MAY 12, 2014
irrigation issues before strengthening home issues (faucets, showerheads, and
toilets).
Member Freed asked if the City could influence CVWD.
Mr. Wohlmuth responded that the City works with CVWD. They are currently
working together on the turf buyback program and flag system. He stated that he
would be reluctant to tell the CVWD board of directors and general manager
what they need to do in Palm Desert. CVWD is in the water business; the City is
not.
Member Freed mentioned that the City of Palm Springs has offered to set aside
funds to incentivize waterless gray water systems for existing homeowners. He
asked if the City of Palm Desert could do something similar.
Mr. Wohlmuth responded that the City has put in $100,000 into the turf buyback
program. He noted that the City has gone through next year's budget process,
and additional funds have not been set aside for sustainability purposes.
However, the City Council could consider using money from reserves.
Councilmember Van Tanner asked Member Freed to explain a waterless system.
Member Freed explained that a waterless urinal does not flush, and used for
urination only. He also explained that with a gray water system you can save
water from one sink, and use that water to flush the toilet. He commented that
the Sustainability Committee is not short on ideas; however, he would like to
know what is possible.
Mr. Bagato stated that many items being discussed are educational. He stated
that he would like to form a couple of groups to work on the education for water
conservation and single-use plastic bags.
Chair Leo asked for volunteers to assist Mr. Bagato on the education program for
water conservation.
Councilman Tanner and Members Freed, Kassler, and Taylor volunteered to
work with Mr. Bagato on the water conservation education program.
Member Tommy Edwards suggested working with someone from CVWD.
Mr. Bagato mentioned that Member David Koller works for CVWD. He also
mentioned that Ygrene has been contracted by the Coachella Valley Association
of Governments (CVAG), and they will cover water infrastructure. He noted that
the City's Code Department will be working with CVWD on enforcing nuisance
water.
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PRELIMINARY MINUTES
CITIZENS' SUSTAINABILITY COMMITTEE
MAY 12, 2014
VII. CONTINUED BUSINESS
None
VIII. OLD BUSINESS
A. UPDATE ON SINGLE-USE PLASTIC BAGS (Tony Bagato, Principal Planner)
Mr. Tony Bagato, Principal Planner, reported that the second reading of the
ordinance was approved with a$.10 charge for all paper bags. He mentioned
that the retailers on EI Paseo are concerned with the $.10 charge for paper bags
since they already provide paper bags for free. He stated that he would like to
form another group of inembers of the Sustainability Committee to work with the
retailers and do more research.
Member Freed commented that the $.10 charge did not come from the
Sustainability Committee; it came from the grocery stores. He stated that he
rather not see a$.10 charge. It makes sense to have a charge for the grocery
stores, but not the retailers.
The Committee agreed with Member Freed. Chair Leo directed staff to move
forward with what the City Council prefers.
Mr. Bagato stated that he will work directly with the retailers group.
Councilman Tanner asked what Palm Springs is doing with the $.10 charge.
Member Freed responded that they are charging $.10 across the board;
however, they do not have an EI Paseo.
At the conclusion of discussions on the $.10 charge, Mr. Bagato asked for
volunteers to assist with the single-use plastic bag education program.
Chair Leo and Members Guinaw and Lingle volunteered.
Member Gatons inquired about the thickness of bags.
Mr. Bagato responded that in accordance with the ordinance drafted by CVAG; a
reusable bag is considered either cloth, woven, or a plastic bag that is at least
2.25 mil thick.
Member Gatons asked if the retailers will change the thickness of the bags so
customers can get the bag.
Mr. Bagato responded that he hopes in a year, when the ordinance goes into
effect, the retailers will all have uniform bags so he does not have to worry about
enforcing the thickness of bags.
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PRELIMINARY MINUTES
CITIZENS' SUSTAINABILITY COMMITTEE
MAY 12, 2014
Mr. David Fletcher, Chartwell Properties, Palm Desert, California 92260,
mentioned that he received a call from the president of the downtown retail
district in Palm Springs. After reading the newspaper, he realized that the
ordinance passed in Palm Springs without input from the retailers. Mr. Fletcher
said that the retailers may now go back to the Palm Springs City Council
because they are not onboard with that decision.
IX. REPORTS AND REMARKS
A. Committee Members Comments
Member Taylor commented that he is looking forward to working on the water
conservation program.
Member Rosenberg commented that she would like to see something in the
BrightSide reminding the citizens to take a reusable bag to the store. She would
also like the store owners and employees to get educated. The clerks
automatically want to put items in a plastic bag.
Member Lingle said that she has found single-use plastic bags very interesting
and educational.
Member Gritters apologized for being late. He stated that he also is interested in
water conservation. He is also happy to hear that the City is budgeting funds for
the turf buyback program.
Member Gatons circulated a copy of The Pinecone Press Waste and Recycling
Newsletter. He commented that the newsletter comes with their quarterly Burrtec
statement. He noted that the newsletter is sponsored by the County of San
Bernardino and Mountain Disposal. Member Gatons stated that he would like to
see something similar with the Burrtec statement in Palm Desert.
Ms. Lisa Ream, Recycling Technician, responded that she could look at the
franchise agreement regarding inserts.
Member Freed commented that Chair Leo gave a rousing speech at the City
Council meeting regarding single-use plastic bags.
Member Edwards commented that he likes seeing the progress on plastic bags,
and he is interested to see where they go with water conservation.
With three additional Sustainability Committee members, Chair Leo returned to
the Consent Calendar to approve the minutes (see Consent Calendar).
Councilmember Tanner noted that the City is changing turf to desert tolerant
landscaping at Desert Willow.
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PRELIMINARY MINUTES
CITIZENS' SUSTAINABILITY COMMITTEE
MAY 12, 2014
Mr. Wohlmuth added that they are looking at reducing turf, and reducing some of
the sand traps on both courses at Desert Willow.
Ms. Ream mentioned that Coca-Cola has a LEED certified building in Coachella,
and they are having a tour on May 15 at 10:00 a.m. She said they have five
spaces available. Please contact her if interested in going on the tour.
Member Gatons noted that the Arrowhead building off the Interstate 10 is also a
LEED certified building.
Member Gritters commented that the 30 acres retrofit at Desert Willow could
potentially save over $100,000 a year in water.
It was announced that August 11 is the next Citizens' Sustainability Committee
meeting.
X. ADJOURNMENT
� �
Upon a unanimous vote of the Citizens' Sustainability Committee, Chair Leo
adjourned the meeting at 3:02 p.m. (AYES: Edwards, Freed, Gatons, Gritters, Guinaw,
Kassler, Leo, Lingle, Rosenberg, and Taylor; NOES: None; ABSENT: Koller, Mourhess,
and Raya).
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Monica O'Reilly, Recording Secretary
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CITY OF PALM DESERT
REQUEST
DEPARTMENT OF COMMUNITY DEVELOPMENT
SUSTAINABILITY COMMITTEE STAFF REPORT
REVIEW THE
REQUIREMENTS
AND DIRECTION
CITY'S CURRENT PARKING LOT TREE
AND PROVIDE STAFF WITH COMMENTS
SUBMITTED BY:
DATE:
CONTENTS
Recommendation
Tony Bagato, Principal Planner
October 13, 2014
1. Palm Desert Municipal Code Section 25.52.050 Parking Lot
Landscaping Requirements
2. Interactive Design Corporation Article "It's a Miserable Life
for Trees in Parking Lots"
3. City of Davis "Parking Lot Shade Regulations: Review and
Recommendations"
By Minute Motion: That the Sustainability Committee provides staff
direction regarding Palm Desert Municipal Code Section (PDMC)
25.52.050 Parking Lot Landscaping Standards.
Backuround
Many cities and counties have adopted ordinances that require a certain amount of tree
planting in parking lots because the shade provided reduces excessive heat buildup in
urbanized areas. In addition, trees improve the air quality and can improve the
aesthetics quality of a commercial parking lot that is filled with pavement and cars.
Just like many other cities, Palm Desert's parking lot landscaping standards (PDMC
25.52.050) requires shade trees in off-street parking areas. The tree requirement is
intended to improve and maximize landscaping within off-street parking areas to provide
50 percent or more of shade coverage in 10 years from when a commercial parking
area is constructed or significantly remodeled. In order to achieve this goal, medium
size or large size trees are required for every three (3) parking spaces in a parking area.
The ordinance does allow carport structures in lieu of the tree requirement, as long as
the carport design is integrated with project architecture and landscaping providing
space for trees between the rows of carports.
Staff Report
Parking Lot Tree Requirement
Page 2 of 2
October 13, 2014
Over the past few years, staff has had several discussions related to the effectiveness
of trees providing shade in parking lots, and potential shade issues from trees next to
carports with solar panels. For reasons discussed in the articles attached to the staff
report, staff does not believe that the current requirements are providing 50 percent
shade coverage in parking lots and may not be the most sustainable design for off-
street parking areas.
Staff is requesting comments and direction from the Sustainability regarding the current
tree requirements for off-street parking areas.
Submitted By:
�.!�----a--- -
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Tony B gato, Principal Planner
`dsrv-fi12k31groups�,PlanninglTony Bagato!Sustainability and Greenhouse GaseslSustainabilitylParking Lot Shade Trees`,SCSR_Parking Lot Shade
Trees.docx
25.�2.050 Yarking Lot Landscaping Standards
Page 1 of 3
Palm Desert Municipal Code
Up j� Prev_ious Next Main ��-�I Search
Title 25 ZONING
Chapter 25.52 LANDSCAPING
Pnnt , No Frames �
25.52.050 Parking Lot Landscaping Standards
A. Landscaping reyuirements.
l. A minimum of 15 percent of the total ofGstreet open parkin� arca shall be landscaped with a miKture
of trees, shrubs, vines, ground cover, hedges, flowers, bark, ehips, decorating cinders, gravel, and similar
material. A minimum of onc-third of the required landscaping shall be distributed within the interior of the
parking facility and the remaining two-thirds of the required landscaping sha(I be provided as peri�heral
planting on the exlerior edges of the parking area.
2. All planLer beds and tree plantcrs shall be bordered by a concrete curb not less than 6 inches in height
adjaccnt to the parking surface.
3. All applicai�ts creating new or rehabilitating parking lots shall provide a landscape plan for review
and approv�l by the landscape manager and ARC for said parking lots. The landscape plan shall incorporate
water-conserving plant material and irrigation tecl�nology in accordance with Chapter 24.04 (Water-Efficient
Landscape).
4. All landscapc arcas shall be �vell maintained in perpetuity.
B. Screeaing requireinents.
I. All off-street parking areas shall be screened to minirni�e the visual impact oil adjacent streets and
properties. No parking space shall be located within 6 fect of a street property line. Any open arexs in the
interiors shall be landscapcd with appropriate plant materials.
2. Open parking facility or a loading area shall be screened from a residential district adjoining or
directly aciross � street or alley. Screening shall be 6 feet in height, execpt that screening to protect properties
across a street may not be less than 4 fiect in hcight.
Figure 25.52-3: Parking Lot Landscaping Reyuirements
littp://www.qcode.us/codes/palmdesert/view.php?topic-25-25_52-2�_52_O50&frames=on 10/6/2014
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C. Tree requirements.
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l. fhe intent of this code is to improve and maximize the landscaping within the off"-street open parking
ar•eas to provide 50 percent or more of shade coverage in 10 ycars. In order to achieve this coverage, the
applicant shall plant singlc-trunk, low-branching trees in windy areas, and design, whcre possible,
norlh/south-oriented parking areas to provide maximum shade. Landscaping shall be Urovided and maintained
to Yhe exteirt that at lcast one mediurn- or large-scale tree is planted for every thrce parking stalls. A diversity
of Cree species is required.
2. The minimum size tree planted shall be no less �han a 24-inch box tree, sized to specifications
according to lhe American Standard for Nursery Stock (ANSI Z60.1) and Ari�ona Nursery Association
Grower's standards.
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Low water use and native plant materials shall be cncouraged and used to the greatest extent possible.
Problematic treey having shallow or invasive roots or having brittle or weak branching structure shall
be prohibited.
5. Parking lot trees adaptable to the Coachclla Valley environment shall be selected and plantcd
according to thc rccommended parking lot tree list in the City's parking lot tree design criteria and
spcciticaCions on file in the City Clerk's office.
6. Where trccs already esisl, lhe parking lot shall be designed to make the besL use of this existing
growlh and shade wherever it is reasonably possible.
D. Parking lut hardscape requirements. Parking lot dividers, islands, planters, and planting areas shall
be a minimum of 5 feet wide and 10 feet long except that all new or retrofittcd tree planters shal( be a
minimum of 9 feet by 7 feet, measured to the inside perirneter of Lhe planter, 3nd shall have no less than 48
square fect of permeable soil planting area.
Figure 25.52-4: Parking Lot Hardscape Requirements
Pagc 2 of 3
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E. Parking lot tree irrigation requirements. Automatic irrigation systems within parking lots shall be
installed. Trees shall bc irrigated with drip emitters, bubbler heads, or subterranean low-volume drip system.
Trccs shall be irrigated separately from shrubs and �;round covers.
F. Parking lot tree maintenance and installation requirements. All plants and irrigation systems
shall be installed according to Chapter 24.04 (Water-Efticicnt Landscape). The owner shall guarantee the
quality of work, health, and condition of plants and installation of materials ineluding but not limited to plant
types, size, spaeing, and irrigation systems. Prior to tinal acceptance of the project, the City shall inspect ailci
verify th�.t the installation is in compliance with the approvcd plans and specifications. All corrections,
adjustments, and/or replaccment of landscape elements shall be done prior to tinal approval by lhe City. ln the
evei�t corrections cannot be made or an installation cannot be compictcd prior to issuance of a certific�te of
occupancy, lhe City shall require a eash deposit equal in value to the amount of landscaping not completed. A
cash deposit is returned oi�ly when the City gives tinal approval of the project.
G. Carport structures in lieu of required treeti. Shade coverage requirements may bc rcplaced by
installing carnort structures throughout the parking lot with some trees tl�roughout tl�e parking lot. The use of
carport structures shall bc approved through the architectural review process. The provision of carports shall
not preclude tl�e necessiry for providing on-site perime�er landscaping.
The earport design sh�ll be integrated with the prqject architecture and landscaping providing space for
trees between rows of carports creating an aesthetically wcll-designed projeeY. Three carport-covered parkin�
spaces shall be considered the equivalent of planting of one required tree. (Ord. 1259 § l, 2013)
http://wevw.qcodaus/codes/palmdesert/view.php?topic-25-25_52-25_52_O50&frames=on 10/6/2014
Interactive Design Corporation
ARCHITECTURE� I TOWNSCAPF I PT:ACF.
It's a miserable life for trees in parking lots
August 12, 2�11 § Leave a cvn�in�ient
MAYBE WE NEED TO RE7'HINK "fREES IN OUR PARKING i.OTS.
It's a miserable life for trees u1 parking lots.
Yeah, I kilow, they sl�ade our cars, and they reduce the "heat islancl" effect; but really, it's i��iserable for
trees — actually for us as well.
First of all, a parking lot really is hotter than hell; at 6 foot above the asphalt the temperature at mid-day
can be 150 deg. F when the air te.mperature is jtist 105; secondly, they are crammed into planters
surrounded by that hot impervious as�halt so po rain gets to their roots; thirdly, that hot �sphalt bakes
t11e undersides of the leaves where the stomata release the wat�r that cools them and the air around and
makes photosynthesis efficient; thirdly, a�ain, tl�osc little roots that are supposed to be out at the
perimeter (drrp line), the ones that actually soak up the water, dley need oxygen and relatively loose
soil, but you Irnow wl�at ha�ppei�s with pavement — compaction, cc�mp�etion, and then impervious toxic
asphalt; fourthly, the sprulkleis are r�ight next ta the trunk not out at the drip line where they should be,
fourthly (again), c�f course the sprinkter heads get broken; fif�l�ly, they are all alone, they are r�ot part of a
system so all the enviroaimentai assaults come full bore — the wind, thc reflected heat, you name it; and
lastly, they are never maintan�ed correciiy eitller b�cause t�iey are hacked out af ignorance, or the
buildi��g owner doesn't want lzis signs hidc(en.
So, what to do. Install PV panels as carports. A study done at ASU cc>mparing trees to carports in terms
of l�cat island reduction �nd water rec3uction noted the followuZg:
1. T�e shade from carports reduced the temp about 56 deg coinpared to 43 deg fi�om tree shade;
2. The canopies used no w�ter;
3. The canopies generate electricity.
Reduce the heat island effect and water usage — not bad far a sustainable practicc But what about
aestlletics, you say. Who wants a harsh street environmcnt of pavement and metal roofs, dark PV
panels, and cars; at lcast trees bring some softness t� our oversized parkiiig lots.
Corre��t, but I think we could change city ordinances requiring shade so that they are favorable toward
PV carports, not trees. Use the trces in ways that n�ake them happy, 4hade wl�at can't be shaded by
canopics and make a strong urban design statement.
1. Use trees selectively to line the nlain drive aisies in generous continuous planters. (We can steal
some width from the overly wide drive aisles.) This will make a stronger urban design statenzent and
provide shade on driveways.
2. Use permeable pavers or pervious concrete in the area around thc trces (out to the drip line.) Some
rain can get thrc>ugh these, and perl�aps we can adjust the substrate to make the svil more root-
friendly.
3. Concentrate tree planting at important (pedestrian and urban desi�n) locations so the trees create a
bosque/microclimate, and have a strong visual impression. They also have a better ch�nce to thrive
because they provide mutual support, irrigation is more efficicnt, and store owners won't be trying
to kill thcm off.
4. Use PV panel carports to cov�>r cars. They generate electricity, and l�y reducing the need for more
fossil fizel or nuclear generating plants, they reduce overall water usage. (It takes a lot of water to
generate electricity. Accordin�, to one Canadian study, it takes up to 30 ga] of water per kWh for
natural gas, and 50 gal per kWh fc�r nucicar plants.)
-30-
Ref: `Thotvvoltaic Canopies: Tl�ermodynamics to Achieve a Sustainable Systems Approach to Mitigate
the Urban Heat Island Hysteresis Lag Effect."
Jay S. Goldcn, Director
Sustainable M�terials and Renewable Technologies Program
Ari�ona State University
Main Campus
P.�. Box 873211
Temp�, Ari�ona 85287-3211
Phone / Fax: +1-(480) 9E5-4951 / (480) 965-8087
Email: jay.golden(�'asu.edu
Interactive Design Corporation
Foll�w
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fteturn to: Pro� ision ?� � Gr�und Sur��ec
Guideline5 for Devefoping and
Evalua-�ing Tree Ordinance5
Evaluating parking lot shading
Shade provided by trees in parking lots reduces excessive heat buildup which can adversely affect the local
microciimate and air quality (Centcr i'or Urban F<,rctt Kcsr�arch 2001 a). Recognizing tl�is fact, ma�ry cities
have adopted ordinances ti�at require set a�nounts of tree plai�ting or shading in parking lots (see pro��ision
25}. Yarking lot shade ordinances lend thetnseives readily to retrospective analysis to determinc whcthcr the
goals of the ordinance are indeed being met Greg McPherson and coworkct-s at the USDA Forest Setvice
Paci�c Southwest Rescarch Station C'cntcr 1�or (Irban F'orest Research evaluated shade in parking lots in
Davis and Sacramento, CA. Like many otl�er Califarnia coinmu��ities, these eities l�ave ordinances t(�at
rec�uire parki��g lots to be landscdped so that 50% of paved area is shaded l5 years after development of the
lot.
ln Davis, iive parking lots were selected f'or evaluation. Ground surveys were undertaken lo iden�fy tree
species, size, condition, and management neecls. Tree cano}ry cover in these lots was evaluated via remotc
sensing techniques. Acrial color infr•ared photographs were taken of the parking lots. 'The researchers then
used ima�c analysis and GIS sofitware to dEteri��ine the percentage of paved area shaded by existing tree
canopy. An overlay was created based on the original landscape plans lo show the plat7ned mature size of
trees (below).
t
T�'e�� C't�vc'r Suz'VCy�
�I�avi� IIi�h S�;h��c�l ! C«mn�lt��t�ity C'c;ta[cr I'a�rkit�g Lc�i, 13�n�i,, f'aiif«rni:�)
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-- Paved s�ea boundery P����Q,� Very lerge trea I12.0 m}
�`� •� �_` A` M� A�tue1 trae shede 'r'���� Lgege tree t1p.0 m)
Percent of Paved l�rea Sha�led - planned 44% Medium tree {s.o m�
Percent of Paved Area Shaded - Actual 8°�fo
Image courtesy of USDA Forest Scrvice, PaciCic Southwest Research Station, Center Ibr Urb�ri Forest
Rcscarch.
Tl�e rescarchers found that currei�t shade coverage ranged from 8 to 45% of the pavcd area of tl�e lots.
1�'urtllermore, thc�y found that the original designs showed prqjected pavemei�t shading of 1 S% to 47% by 15
years after developtnent, all less than the ardinance standard of 50% sl�ad ing. The Davis ordinance, which
was adopted in 1979, was updated in 1997 based on informatio�� fi�om tl�c parking lot sl�ade survey.
A similar ai�alysis of' 15 parking lots in Sacrameuto, CA (McPherson subn�itted) was made with the help of
volunleers from tl�e Sacramenio Tree Foundation. Using ground survcys only, volunieers recorded the
fi�llowing �lata:
. tree species
. D[31 i
. average crown diameter (determincd by measuring canopy two radii at 90 clegrees to each other to the
nearest 0.5 meler by tape)
. the percentage of crown that sl�ades parking ]ot pavement to the nearest 25% excluding overlapping
shade
. nianagement needs
. vlcant pl�i�ting sites.
In addition, tl�e� researchecs used originll site plans on fle with Uie Planning l�epart�T�ent to calculatc� thc
total paved area in each IoL Shading provided by each trce was cstimated assuming tliat crowns were
circular iu outline. For the 10 lots in which the trees were less than 15 years old (range 1-14 years), tt�e
i•esearcheis used empirical data on tree spre�td at diflerent ages collected fi�on�i the nearby city of Modesto to
estimate crown diarneter after 15 years. Since much of this data was based on street trees growing in
residential yards, it probably ova•estimatcs parking lot tree growth.
This survey found that the ordinanec, cnactcd in 1983, was only pai-�ially ef'fective in meeting its goals. One
of the lots over 15 ycars old act�ially exceeded tl�e sl�ading standard (�5%), and another was close to the
standard (47%). However, projected tree shade I 5 years after developmez�t averaged only 21 % ovcrall. Thc
atialysis also showed that h•ee shading was generally lower in retail business lots than in office or apartiuent
Uai`king luls.
Researchers found that the following factars contributed to ihe failure of parking lots to meet shade
standards. Scveral of these factors are also likely to coiitribute to failure oL'other rypes of parking lot
planting ordi��ances.
. Trees sl�own on plans were i�c�t planted or else were removed shortly afte�r planting. This was a
partieular proble�n near store fronts where business owners feared trecs woirid block their signs.
. Tree species planted in lots were not lhose shown on plans.
. Crown diameters listed for tree specics in thc sup�orting regulatioi�s were larger than trees would
�ctually attaii� un<ler parking lot conditions.
. There was ��o crown spread data in tl�e supportii�g planning regulations fbr some of tl�e species
commonly planted in parking lots.
. Submitted parking tot plaus used tl�e wrong crown spreads for the trees in the plans and the �rrors
wcrc not caugl�t by the Planning Department.
. Tree shade was overestimated in cases where overla�ping sliadc from acljaeent trees was counted
twice.
Trees growing in }�arking €ots are often stunted becausc soil cotnpaction and i�npermeable pavement liinils
the am�unt o['rootable soil voEuanc av�ilable a�ld becaiase tempe�rature aild soil moisture regimes i��i parking
lot islands are often ui�favorable for tree g�•owth. In additio��, somctimes soil is treated witil chemicals
during the construction process (c.g., high aino��nts of lime) that may render it unCavorable for plant growth.
By measuring crown spread of irees in Sacramenlo parking lots, researchers wcre able to determine the
likely crown spread 111at various tree specics eould attaii� when grown in parl<ing l�ts. "l�ree crown projection
arcas (i.c., area of sl3ade provided by trees) after 15 years, as measured by McPherson's group, were
considerably less ttian tl�ose listed in lhe supportin� rcgulations.
McPherso�� also conducted an economic analysis to calculate botli the loss ii� benefit value associated witl�
the lack of compliance with the ordinaiice (estimatcd at about $2.2 million per year citywide) as well as the
likely costs of various remcdial actions. In addition to suggestions for improving the parking lot shading
ordinance, this analysis provided insight it�Co elements of site pJanning and parking lot design that could be
modified to rcduce total amounts of area devoted to �arking an� inerease shading of paved areas
(McPher,c,a� subn7itled).
Parking Lot Shade Regulations:
Review and Recommendations
Prepared for the City of Davis
By Jennifer Tso, Tree Davis intern
February 2014
�'�b��z� °T�ai� ���c��t
This report is a compilation of findings from a Tree Davis internship project on parking lot shade
regulations. It focuses on studies conducted in Davis, California, but has general recommendations so
other municipalities may find it useful.
The majority of the information in the "Trees and Parking Lots" chapter is based on Kathleen Wolf's
2004 paper, titled "Trees, Parking and Green Law." Her publication was sponsored by the USDA Forest
Service, Southern Region (Southern Center for Urban Forestry Research and Information�, and the
Georgia Forestry Commission. It is a valuable reference for regulating parking lot trees.
Many suggestions in the "Recommendations" chapter are based on findings discussed in earlier
chapters. If you skip ahead, note that numbers in parentheses (#) refer to a city in Table 3.2. Literature
references are noted with author(s) and date (e.g. Wolf, 2004). If available, you can find download or
website links in the "References" section. Other materials, such as surveying documents or notes on
municipal codes, are available by request.
This report was reviewed by peers for content and grammar. Errors are solely the responsibility of the
author.
This report can be downloaded from the �iree J�ti=i� website.
2
"1 ��1��� �a�° �:���t�z���
A6outThis Report .........................................................................................................................................2
Tableof Contents ..........................................................................................................................................3
Acknowledgements....................................................................................................................................... 4
ExecutiveSummary .......................................................................................................................................5
Chapter 1: Davis' Parking Lot Shade Ordinance ...........................................................................................7
Introduction & Project Rationale ..............................................................................................................7
UCDavis Research .....................................................................................................................................7
TreeDavis Studies .....................................................................................................................................9
Chapter 2: Trees and Parking Lots ..............................................................................................................10
Introduction............................................................................................................................................10
Parking lots and the Environment ..........................................................................................................10
Treesin Parking Lots ...............................................................................................................................11
Chapter3: Municipal Code Review .............................................................................................................13
Introduction............................................................................................................................................13
Methods..................................................................................................................................................13
Results.....................................................................................................................................................14
CodeExamples ........................................................................................................................................16
CaseStudies ............................................................................................................................................20
Chapter4: Parking Lot Surveying ................................................................................................................22
Introduction............................................................................................................................................ 22
Methods.................................................................................................................................................. 22
Results..................................................................................................................................................... 24
Problems................................................................................................................................................. 25
Discussion................................................................................................................................................ 26
Chapter 5: Recommended Practices ...........................................................................................................27
References..................................................................................................................................................32
Appendix 1: 2006 & 2007 Parking Lots .......................................................................................................34
Appendix 2: Code Practices by City .............................................................................................................35
Appendix 3: Davis' Parking Lot Shade Code ................................................................................................37
Appendix 4: Correspondence with Derek Linn of Fayetteville, AR .............................................................38
Appendix 5: Field Surveying Protocol .........................................................................................................40
3
�<��:���c����c����n�t�t�
This project involved many people through its multiple components. Much thanks to:
Keith McAleer, Tree Davis Executive Director, for discussions, paper review, and keeping me on-task;
Morgan McMahon, Tree Davis intern, forsurveying parking lots;
Rob Cain, City of Davis Urban Forest Manager, for providing documentation of earlier work;
Members of the Tree Davis Board of Directors and Davis Tree Commission, for guidance;
Derek Linn, City of Fayetteville, for answering many, many questions;
Walter Passmore and Dave Dockter, City of Palo Alto, for discussing practices, providing further
direction, and furnishing copies of the Tree Technical Manua! and Planner's Toolbox;
Sarah and Ruth for providing information about earlier Tree Davis studies;
John de Goede, fo� his assistance with G/S;
Loren, Eric, Julia, Jared, and Jeffrey for reviewing the report;
And other staff from the following cities for fielding questions:
Davis, CA
Fayettevifle, AR
Leesburg, VA
Los Angeles, CA
Palo Alto, CA
Portland, OR
Sacramento, CA
4
���c�tiva� ��a���r����
Plants in parking lots have been traditionally used for aesthetics and traffic guidance. Regulations
generally mandate the quantity and distribution of plants, including trees, based on the size of lots.
Increasing emphasis is placed on the ecological services and benefits of urban vegetation, a trend that
can be seen in laws regarding parking lot trees. Davis, a small city about 20 miles west of Sacramento,
California, was one of the pioneers of parking lot shade regulations. Davis' ordinance requires that all
parking lots be 50% shaded by tree canopy 15 years after development. Although the regulation has
been in place for nearly 40 years, there are been no enforcement of shade coverage. The city partnered
with Tree Davis to monitor parking lots in 2006 and 2007, but the project was terminated soon after due
to budget cuts. In 2013, a Tree Davis intern revisited parking lot shade regulations in Davis as well as
other cities in the U.S. The report titled "Parking Lot Shade Regulations: Review and Recommendations"
is a summary of that work.
Part 1: Trees & Parking Lots
The search for information about the impact of parking lots and the ways in which trees mitigate those
effects turned up research that was conducted in Davis and nearby cities. Most of these were
summarized in a report by Dr. Kathleen Wolf of the University of Washington, titled "Trees, Parking and
Green Law: Strategies for Sustainability." It is an indispensable resource for anyone interested in
parking lot green law, from residents to nonprofit organizations to municipal staff.
Part 2: Municipal Code Review
Since there are plans to revise Davis' shade ordinance, particularly to strengthen enforcement, codes
from 38 cities were reviewed to find practices that could be adopted. Parking lot green laws, or laws
dealing with vegetation in parking lots, were grouped by their requirements into three categories:
landscaping only, trees only, and parking lot shade. Landscaping and trees only regulations may have
been primarily concerned with aesthetics and traffic guidance, whereas parking lot shade regulations
indicate a shift towards valuing environmental benefits. Promising and innovative practices were
discussed, and two cities (Fayetteville, AR and Palo Alto, CA) were selected as case studies.
Part 3: Parl<ing Lot Surveying
The earlier Tree Davis studies had interns and volunteers measure parking lot tree canopies. The 2013
project revisited five of the lots with 6oth field and i-Tree Canopy surveying. i-Tree Canopy is a tool in
the i-Tree software suite used by urban forestry professionals to quantify environmental and monetary
6enefits provided by trees. It was evaluated as an alternative to field surveying, since it allows the user
to upload property boundaries and assess canopy coverage using satellite imagery. Both methods had
major problems that rendered them questionable for quantifying canopy, especially if the assessment
had to be accurate enough to provide a basis for imposing fines. A field surveying protocol was
developed based on a U.S. Forest Service monitoring document, but it may not be cost-effective for
most municipalities.
5
Conclusion
The findings from each component of the study were summarized into recommendations for cities
interested in creating or improving a parking lot shade regulation. Since enforcement of shade coverage
is difficult, it may be easier for cities to require a minimum number of trees distributed across a lot.
Specifying proper planting details and preventing unnecessary pruning will enhance growth and allow
each tree to reach its canopy potential.
��������.r 1: ���ri�' P'��•i�i�o�; Lc�� Si����e €?�°�������
�°',¢"..`E�E�.2<t < . . �g� °17'p , .��T>�, "".x�'°
Davis is a small city located about 20 miles west of Sacramento, California. It has a population ot
approximately 66,400 (US Census Bureau, 2012) and is home to the largest University of California
campus. Known for its liberal culture and politics, Davis' code reflects its progressive attitude towards
environmental protection. One example is the Parking Lot Shade Ordinance (Municipal Code 37.04;
Appendix 3), which was introduced in 1977.
The ordinance requires that 50% of paved parking lot area be shaded by tree canopy 15 years after the
building permit is issued. In 2000, it was updated to the current version by the Parks Department and
the Davis Tree Commission. As one of the earliest parking lot shade ordinances, it can still be considered
innovative compared to traditional landscaping codes. However, the ordinance has been surpassed by
other cities with more detailed codes or guidelines. Despite its early adoption, there has been no
enforcement of compliance and many parking lots appear to fall short of the 50% shade requirement.
The city commissioned Tree Davis, Davis' nonprofit tree organization, to assess canopies of several
parking lots in 2006 and 2007. The results indicated that only a few lots were on track to compliance.
Surveying was discontinued as of 2007 following funding cuts.
The impetus to revisit the ordinance grew as discontent with newly installed parking lots spread.
Shading plans with the location and shade contribution of every tree are required, but exemptions may
be granted by City Council even after plans are approved by the urban forest manager. Since existing
parking lots are not monitored, shade enforcement of new parking lots is more difficult. This project
arose from the desire to enforce compliance and to revise the shading guidelines.
This study observed the tree canopy status of a sample of parking lots with field and remote sensing
surveys. A review of municipal codes provided examples of suggestions for improving Davis' code. This
report details previous work and summarizes new findings to provide a solid and historical foundation
forfuture projects.
_" �: i, _ _��
The first study on Davis' shade ordinance was conducted before any lot had reached its compliance
date. Kathryn Elliot's master's thesis "Tree Shade in Urban Parking Facilities: An Evaluation of Parking
Patterns and the Davis Mandatory Shade Ordinance" was published in 1988. She discussed parking lots
as "machine space," a concept describing places where machines have priority over humans. An
example is highways, where bicyclists and pedestrians are forbidden. In the case of parking lots, she
states that a shade tree ordinance can "transfer machine space into human space and provide people
with a sense of place." Her project explored the shade contributions of trees, temporal preference for
shaded parking spaces, and property manager perceptions of the ordinance.
The study was conducted on 10 parking lots over the course of 50 weeks. Elliot measured the number
of partially and completely shaded spaces as an average of three daily measurements. There was an
7
overall average of 47% spaces shaded and 28% completely shaded. Her method of ineasuring shade
may have been appropriate for the original ordinance but not under the current guidelines, which
expand the area of the parking lot that must be shaded. Although quantifying shadows cast by trees is
more representative of actual shaded area, enforcement using this method is infeasible since shade
patterns change rapidly over a day.
On average, 52% of parking spots were utilized, depending on the type of business associated with the
lot. Preference for shade increased with higher temperature but was overshadowed by preference for
proximity to the business. A survey of property owners and managers revealed that most were unaware
of the ordinance but did not consider costs to meet its requirements unreasonable. Even so, one
manager wanted more trees for aesthetics, not to meet regulations.
Elliot suggested a second ordinance to address retrofits of older lots. Tree preservation, placement,
and tree lists needed to be emphasized. She also suggested continuing enforcement to ensure shade
beyond the 15 years.
Another study followed in 1996, using the original 1977 ordinance. A landscape architecture student,
Tin-Wah Wong, focused his senior project on evaluating parking lots and making recommendations on
various aspects of the code. He identified the following weaknesses: lack of pfanting site details, no
incentives or penalties, overly simple diagrams (Figure 1.1�, and omission of shade provided by trees not
physically in the lot.
SAMtC� SHAO£ O/AGRAM
�
srarer
Like Elliot, Wong assessed canopy cover and interviewed
property managers of five parking lots. His assessment
using infrared photography allowed him to accurately
� ''"���! distinguish between tree canopies and paved areas.
� `��
_�r Growth of trees was projected to 15 years to determine
�.r�?� :� _.
�-�w.� � compliance progress, with none of the lots found to be
���� ��° ��
�� a��, � compliant. An analysis of shade plans revealed that they
,�b,= �
had not actually been designed to be 50% shaded.
�.R' '�s Manager interviews revealed the following problems:
'�� ����� budget, legal restrictions (e.g. pesticide approval), lack of
4 I
�, ;..
tree replacement, previously poor maintenance, and
� � � I � .� � change in ownership.
� t���" .
#� ���`� Wong suggested clearly defining terminology and
.rvaesrsrm� 9+vco aw xcmea er
� ��
7DTAL NNfD ARfA $G,�:AR! �Ei�
7DFAL tNVl1� ARf.1 S'NLYD �`-KZ/JARE F�ET
�ecurrnac a� vA✓ro �aaEo swoacv _ �
Figure 1.1: 1977 Davis ordinance diagram
increasing requirements for approval, issues which have
been resolved by the 2000 revision of the ordinance. He
also recommended conducting outreach and issuing fines
based on how much canopy deviated from 50%. Other
suggestions, such as unannounced site visits, were not
F:l
appropriate because they require unrealistic amounts of city resources.
Many of the conclusions made by the two students are still valid today and offer a social and managerial
perspective not addressed in the Tree Davis studies.
. F� . �;- . . r:� �.#;°.:_
Tree Davis became involved in 2004 when it was contracted by the city to survey parking lots.
Conflicting accounts and records from the Davis urban forest manager and former Tree Davis executive
director confound whether surveys were actually conducted that year. However, in the same year, the
U.S. Forest Service (USFS) produced a"Parking Lot Shade Tree Inspection and Monitoring Guide"
specifically for Davis. It was created to "assist volunteer inspectors in making the most accurate
evaluations possible of the conditions of parking lot trees and their surroundings" (USFS, 2004). The
guide was accompanied by a spreadsheet for recording data and calculating projected canopy area. The
document could also generate a summary report for property owners and city staff. To date, neither
resource appears to have been utilized except as a basis for a surveying protocol described in Appendix
5.
Parking lot surveys were conducted in 2006 and 2007 by Tree Davis workers under city contract. The
goal was to measure tree canopies of a sample of parking lots to establish a baseline of shade coverage.
Most of the data from the 10 lots surveyed in 2006 has been lost, with the exception of a progress
summary. A 20-year old lot was found to be non-compliant, while three lots were projected to comply
and the remainder projected to fail to comply with the shade ordinance.
Volunteers were enlisted to survey 11 different lots in 2007. Only one lot exceeded 50% shade, with 3
projected to comply and 7 projected to fail to comply (Appendix 1). 5hade plans for each lot and canopy
measurements for each tree were available, so these lots were se�ected for the 2013 study.
The 2013 study was conceived to provide updates on previously surveyed parking tots and code
examples from other cities for the revision of Davis' shading guidelines. It was expanded to include a
summary of the benefits of trees in parking lots. The work was performed by a Tree Davis intern in
consultation with the urban forest manager and the Tree Commission.
0
{:����t�z� L; �'��c�c� �z�a� ��A����i��, i,c�t�
�t£4��a`�� k�e...s
Whereas the previous chapter discussed studies specific to the Davis shade ordinance, this chapter
highiights peer-reviewed literature relating to functions of trees in parking lots. In addition to producing
the "Parking Lot Shade Tree �nspection and Monitoring Guide," researchers at the USFS have conducted
scientific research on parking lots in Davis and Sacramento. The primary resource, however, should be a
report by Kathleen Wolf of the University of Washington titled "Trees, Parking and Green Law:
5trategies for 5ustainability" (Wolf, 2004). It is useful for various interest groups with its discussion of
the impacts of parking lots and how legal strategies can reduce them. This chapter is a summary of the
report, with a focus on benefits that are more pertinent and tangible to both the public and property
owners. For a more extensive discussion, the report can be found at Dr. Wolf's hom€.=�;;�€;��.
� ��_ � ` =' '
s = vt:s. �?" �'�` ",�
Parking lots occupy about 10°/o of land in US cities, reaching up to 20-30% in downtown core areas
(Beatty, 1989). In many cases parking demand is fulfilled by surface lots (Stocks, 1983), which can
occupy two to three times the building space. Conversion to paved surfaces may have significant
negative environmental, health, and societal impacts. Among them are higher temperatures, greater
use of personal vehicles, and increased pollutant emissions (McPherson, 2001). Still, adequate parking
is a major factor in the success of commercial buildings and must be balanced with other uses of the
space. This discussion focuses on surface parking lots as they comprise a significant part of urban land
use. 5ince their sole function is to provide temporary vehicle storage, their impact seems
disproportionate to their purpose.
�t; � �.
Paved surfaces function as "thermal batteries" due to the heat retention properties of the materials.
They absorb and retain heat, releasing it slowly at night. In the daytime, unshaded asphalt can reach
temperatures as high as 160°F. Materials such paint, plastics, rubber, and asphalt deteriorate more
rapidly as they expand and contract with temperature fluctuations. This translates to decreased vehicle
value and reduced pavement lifespan, which may lead to a financial impact on parking lot users and
property owners. Higher temperatures also encourage greater use of energy for cooling, which can
"push supply to or beyond capacity" (Wolf, 2004).
The collective effect creates an urban heat island (UHI), where temperatures in urban areas can be as
much as 10°F higher than in surrounding rural areas. The difference is greater at night because
pavement materials release heat slowly, compared to vegetated areas cooled by evaporation. The
temperature difference can result in temperature inversions, where a layer of warm air prevents
upward movement of airfrom the surface. This phenomenon can trap pollutants close to the ground.
Paving dramatically changes the hydrology ot a site by introducing impermeable surfaces that reduce
infiltration and promote runoff. These surfaces can generate two to six times more runoff volume than
the original landscape (USGS, 2D03). Pollutants such as gasoline, motor oil, and salts deposited on
F[�:
parking lot surfaces are washed away by the first flush of precipitation. Biological treatment by soil
microorganisms must be substituted with wastewater processing facilities, which incur costs in transport
and treatment. Since runoff is increased, water transportation infrastructure and treatment facilities
must be designed to accommodate unusually large volumes during storm events. Should the
infrastructure capacity be exceeded, flooding, erosion, and overflow of stream channels can occur.
Water pollution and loss of habitat may follow.
.' E �+ �fa
Vehicles are one of the sources of nitrous and sulfurous oxides and volatile organic compounds (VOCs).
When these chemicals react in the presence of sunlight, they can form tropospheric ozone —ozone in
the layer of the atmosphere closest to the ground. Although ozone is often associated with protection
from ultraviolet (UV) radiation, this only applies to stratospheric ozone found at higher altitudes.
Ground-level ozone can affect lung function, increase allergen sensitivity, irritate eyes, and provoke
dizziness and nausea (EPA, 2003). High concentrations of ozone can also lead to smog formation.
Parking lots add another dimension to the problem. Most emissions are from tailpipe exhaust, but
approximately 16% can come from gasoline evaporation when vehicies are not in use (Scott et al, 1999J.
Higher temperatures in unshaded lots increase emissions from the fuel tank through volatilization.
There are also hidden indirect costs of parking lots. Taxpayers finance infrastructure to substitute for
natural processes impacted by development. Respiratory and heat ailments may result from the
collective effect of urbanization. Wolf (2004) presents a case for reducing these impacts and costs by
focusing on one solution — planting trees.
� � � �� i � �.a���FG � .
Trees have been traditionally included in parking lots for aesthetics or traffic control. However, they
simultaneously provide a multitude of benefits for lots and adjacent buildings. These benefits include a
reduction in energy use, greenhouse gas emissions, air pollution, noise levels, and runoff, as well as an
enhancement of ecosystem functions, property values, public health, and overall quality of life.
� � ,� ��s ,��, _
Air temperatures can be 20°F - 40°F higher in the parts of cities with parking lots, with lower
temperatures around vegetation (NASA, 2003). Unshaded asphalt can reach temperatures as high as
160�F in the daytime. Vegetated areas tend to be around 7�°F with less temporal fluctuation, thanks to
evaporative cooling from the soil and foliage. A study conducted in Alabama by the National
Aeronautics and Space Administration (NASA) in 2003 illustrates this difference. When the surface
temperature of parking lot pavement was 120°F, the temperature in a tree island was only 89°F (NASA,
2003) — a difference of 31°F!
Wolf (2004) considers tree planting as one of the "most cost-effective means of mitigating urban heat
island." Trees have a greater effect than shrubs and groundcovers due to their tall and large canopies,
which prevent radiation from reaching and heating the ground. The collective leaf surface area also
results in more transpiration. A 109'o increase in canopy can reduce air temperatures by 1°F (Simpson et
al, 1994). A study conducted in Davis showed that there is a major difference in temperature of cars
11
parked under trees. The surface of the parking lot was 36°F cooler under tree shade and the vehicle
cabin was over 47°F cooler (Litman, 2002�.
Litman (2002) also found that the fuel tank temperature was reduced by 7°F under tree canopies, which
reduces emissions of hydrocarbons and other ozone precursors. Energy usage for cooling is reduced
with lower temperatures, in turn decreasing demand on utilities that also produce emissions.
While water treatment facilities are designed to accommodate large volumes of storm runoff, restoring
natural processes may be more cost-effective. A consortium of soil microorganisms can provide on-site
treatment of a variety of contaminants without the need to transport water to another location. Plants
may also take up contaminants and nutrients, enhancing the treatment process. Water can then
percolate through the soil to repfenish groundwater supplies. Not only do vegetated areas reduce
infrastructure and treatment costs, they also enhance the appearance of developed areas. Although
restoration of original ecosystems is difficult or nearly impossible, other practices such as rain gardens
or bioswales have been gaining popularity. These design elements combine function and aesthetics to
transform paved areas into permanent stormwater processing facilities. Trees in such gardens provide
many functions such as shade, photosynthesis, carbon sequestration, and more. Research on green
design elements in landscape architecture and horticulture is abundant and will provide a strong
foundation for practice.
Wolf (2004) discusses a variety of social benefits associated with urban greenery, such asjob
productivity and satisfaction, patient recovery, and youth recreational creativity. Property values
increase for both residential and commercial sites, with commercial buildings commanding higher rental
rates (La Verne & Winson-Geidemann, 2003). Trees encourage more frequent and fonger visits to
businesses, with a greater willingness to pay more (Wolf, 2003). Well-managed landscaping extends "a
message of care and quality from merchants to potential customers." (Wolf, 2004) The benefits of trees
are not limited to the property but will extend to the neighborhood or city level.
� � .y �a .
Trees are not without costs, no matter where they are planted in the urban landscape. Concerns of
property owners regarding parking lot trees may include increased water use, maintenance costs,
obstruction of signage, and intrastructure conflict. Parking lot users may be concerned with pollen,
litter, honeydew, and bird excrement. Trees should be considered infrastructure. Potential problems
should be addressed in the planning stage, when designers choose suitable species and provide site
preparation guidelines. Once established, trees may not need much care at all, especially if
unnecessary maintenance such as overpruning is reduced. When possible, healthy mature trees should
be preserved because they provide greater benefits than new plantings. Strategies to address some of
these problems are discussed in Chapter 5.
Fia
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This component of the study is designed to facilitate revision of Davis' shading guidelines by providing
examples from other cities. The chapter summarizes code findings and highlights two cities as case
studies. Recommendations based on the findings can be found in Chapter 5.
Historically, green law (code regarding vegetation, stormwater, and other environmental issues) has
been concerned with aesthetics. Innovative laws are based on scientific research and address
sustainability and public health goals. Part of the difficulty of establishing green law is that there is no
national standard to use as a model, especially since local law is influenced by regional environment,
social values, and political factors. Simply borrowing code from other municipalities will not be effective
unless the tools are locally adapted and applied (Wolf, 2004).
Traditional parking lot green law focuses on aesthetics and traffic control using perimeter and interior
{within the lot boundaries) landscaping. Perimeter trees are usually planted as buffers for aesthetic
mitigation and only contribute partial shade. In some cases, trees are not required at all. In contrast,
innovative code varies regionally depending on what is appropriate and valued by the community.
Progressive practices include paved area reduction, tree preservation, canopy cover and shading, plant
specification, and stormwater management.
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Entering "parking lot shade" into an internet search engine yielded municipalities with shade regulations
and turned up research papers (Wolf, 2004; McPherson, 2001) with more cities. The t�r,€�.+=r�. L<,i�{�fs
�+�f bsit€= has examples of code, some of which mention parking lot landscaping. The search yielded 39
cities whose codes were explored. Since new practices were not encountered towards the end of the
list, this component was concluded.
Municipal codes were accessed through the city website, generally under the Development or Zoning
sections but occasionally in a separate tree section. Parking lot landscaping code did not always
reference maintenance, preservation, or enforcement requirements in other locations, so these are
included only if encountered. Codes may also have been updated between the time of review
(September 2013) and report writing (December 2013) — such was the case for Bentonville, AR.
Codes were categorized into landscaping only, trees only, and parking lot shade (Tabie 3.1). Cities that
covered more than one category are placed into the most specific one. For example, those with tree
and shading requirements would be placed in the parking lot shade category.
13
Table 3.1: Code categories
Category Description
Landscaping only* Requires a minimum of parking lot landscaping, but does not mention or
require a minimum of trees; general purpose is for aesthetics or traffic
manipulation; may be limited to perimeter landscaping or may specify
interior requirements
Trees only* Requires a minimum of trees, which could be based on parking area,
number of parking stalls, etc.; may require distribution across lot but does
not mention shade
Parking lot shade Requires that a specific percentage of the parking lot area be shaded
within a certain time; purposes shifts from aesthetics and traffic to other
benefits of trees
�onsiaerea traaitionai coae py woit, LUU4.
Requirements of the codes in the latter two categories were divided into 19 subcategories to visualize
the diversity of practices. Municipalities that integrated greater quantities of practices to accompiish
their canopy goals were identified, and of those, 7 cities were contacted. Palo Alto, CA and Fayetteville,
AR are used as case studies.
� , ��'�
Of the 39 codes reviewed, 17 had parking lot shade requirements, 14 otherwise required trees and 8 did
not (Table 3.2). Thirteen of the 17 cities requiring parking lot shade were found in California, which may
have been due to selection bias.
Table 3.2: Cities reviewed. (The first column is referenced in parentheses in the discussion of practices.)
City # City Name Parking Lot Trees Only Landscaping
Shade Only
1 Agoura Hills, CA x
2 Austin, TX x
3 eellevue, WA x
4 Bentonville, AR x
5 Brookfield, WI x
6 Burbank, CA x
7 Chicagq IL X
8 Chico, CA x
9 Colorado Springs, CO x
10 Concord, NH x
11 Coral 5prings, FL x
12 Davis, CA x
13 Eureka Springs, AR X
14 Fayetteville, AR x
14
City # City Name Parking Lot Trees Only Landscaping
Shade Only
15 Folsom, CA x
16 Grand Junction, CO x
17 Indian Wells, CA x
18 La Verne, CA x
19 Leesburg, VA x
20 Lewiston, ID x
21 Los Angeles, CA x
22 Minneapolis x
23 Mobile, AL x
24 Modesto, CA x
25 Orlando, FL x
26 Oroville, CA x
27 Palo Alto, CA x
28 Portland, OR x
29 Redmond, WA x
3� Redwood City, CA x
31 Sacramento, CA x
32 San Antonio, TX x
33 San Francisco, CA x
34 Scottsdale, AZ x
35 Suisun City, CA x
36 Tucson, AZ x
37 Wasilla, AK x
38 West Sacramento, CA x
39 Woodland, CA x
Total 17 14 8
The 19 subcategories were arranged in a spreadsheet (Appendix 2; summarized in Table 3.3) to visualize
the frequency of occurrence. Overiap does occur across subcategories. For example, code requiring
50% shade essentially requires that the trees be distributed across a lot. Additionally, a subcategory
such as "interior landscaping" encompasses many practices and is found more frequently than a very
specific subcategory like "shade plan." Note that not having an innovative requirement such as shade
coverage does not preclude a city from being progressive in other regionally appropriate ways. Table
3.4 lists the cities with the most diverse codes.
15
Table 3.3: Subcategories of practices ranked by
frequency of occurrence in 38 codes
Subcategory Frequency
Interior landscaping 24
Spatial requirement 19
Shadecover 17
Minimum planter size 15
Tree size 14
Maintenance/replacement 13
Substitution/flexibility 13
Perimeter landscaping 10
Planter range 8
Tree lists 8
Extra lists 7
Diversity 7
Sliding scale 7
Deposits 5
In lieu fee 5
Landscape or Tree Manual 5
Shade plan 4
Tree Fund 4
. E � � . _.
Table 3.4: Top 10 cities with the greatest
number of code practices
City #* City Name Practices
14 Fayetteville, AR 17
31 Sacramento, CA 14
19 Leesburg, VA 12
28 Portland, OR 12
11 Coral Springs, FL 10
27 Palo Alto, CA 10
29 Redmond, WA 9
26 Oroville, CA 8
21 Los Angeles, CA 7
24 Modesto, CA 7
�`The city numbers are from Table 3.2.
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The Davis code (Appendix 3) requires that 50%o of paved parking area must be shaded by tree canopy 15
years after the building permit is issued. Paved area is defined as surface upon which a vehicle can
maneuver, which includes parking stalls and drive aisles but not planters. Separate shading guidelines
dictate which trees to use, describe shading plan requirements, and detail planter specifications. A
separate section of the chapter (37.06.040) discusses penalties for violating the tree preservation
ordinance, which include tree replacement or in-lieu fees to be placed into the tree preservation fund.
Preservation was not referenced by the shade ordinance.
While the ordinance was once ahead of the times, the code review identified several dimensions where
it is lacking. The remainder of this chapter presents practices utilized by other cities absent from the
Davis code. Each practice or city is followed by the city numbers (see Table 3.2) so the reader can refer
to the code for greater detail.
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In cities without shade requirements, traditional perimeter and interior landscaping requirements can
nevertheless enhance parking lot urban forests by mandating evenly distributed trees. Perimeter
landscaping describes buffer requirements and is usually located in a different section of the code. Two
unique practices were found: in Palo Alto (27}, 50% of perimeter trees may be included in shade
calculations, while Chico (8) grants a 10% shade bonus for trees planted along the western perimeter
provided they are in sufficiently large planters. The emphasis on placement is especially important since
trees planted along the north or east sides of a lot may provide minimal shade during hours when solar
heating is greatest.
? �.... _ .�. .. . ,
Interior landscaping requires a minimum number of planters for lots over certain sizes and may require
a minimum number of trees in each planter. Sliding scale systems require more landscaping in larger
lots to offset the increased impact. They are more common for interior landscaping but may be applied
to shade requirements — larger lots must have a greater percentage of tree canopy (17) or more tree
points (21).
,<: ,�.';��
Almost all the cities with shade requirements mandated that parking lots be covered by minimum
canopy (209'0-50%) anywhere from 10-20 years after building permits are issued. The exception, Orlando
�25), uses a system of tree points based on acreage and location of the site. Preserving larger trees
contribute more points than smaller trees and the difference may be made up with tree plantings.
Although 16 cities require shade, only four (6, 12, 26, 31) require a shade plan with the location and
shade contribution of each tree. One of the difficulties with enforcement in Davis is that there is no
specified date and time at which a parking lot must meet the shading requirement. Los Angeles (21), in
contrast, requires 50% shade during zenith on the summer soistice. Although this detail may seem
insignificant, it indicates that the assessment will be performed when the trees are in full canopy.
Additionally, Davis' area calculation complicates enforcement as it excludes planters from the total
paved area. While logical because cars do not operate on this space, the planter still represents an area
that is shaded. By exc�uding this area from the paved area calculation, shade is overestimated.
Subtracting the planter area from the canopy area is an option but requires an additional step. It may
be easier to include planters in the calculation as �roville does (8�.
�
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The most common tree stock quality requirement is that trees must be of a minimum size for planting
and replacement. Davis does not require species diversity, but six other cities do (8, 11, 14, 16, 19, 28).
Restricting monocultures prevents canopy decimation by species-specific pathogens or pests, which
could wipe out many trees if only a few species dominate. A diverse parking lot urban forest provides
resilience against outbreaks and allows lots to recover quickly with fewer tree replacements. Tree lists
facilitate diversity but will not be effective without limiting the use of a single species or genus.
Some cities go beyond this recommended list with more detail, such as native or prohibited species.
Prohibited species may be invasive, unsuitabie for parking lots, or palms which do not contribute much
17
shade. A prohibited species list complements a recommended list by restricting trees that could be used
by innovative planners. A city encouraging flexibility could approve species not on either list without the
need to repeatedly reject unsuitabie species. Fayetteville (14) also has a list of construction-sensitive
species to aid in preservation efforts, since it may not be cost-effective to save a healthy specimen that
is very sensitive to construction impacts. Lists may also include water requirements for different plants
(25). These specialized lists require more work by the municipality as the species to include or prohibit
varies regionally and requires regular update. Examples of tree lists can be found in the codes of seven
cities (11, 14, 19, 21, 25, 28, 31).
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Proper soil conditions maximize the growth and shade contribution of trees but are often lacking in
parking lots. Although 15 cities require a minimum planter size, the size may be inadequate. Overhang
requirements, which dictate how far the bumper of a vehicle can extend into a planter or walkway, are
especially important in preventing trunk damage and should be based on mature trunk diameter. Some
cities permit a range of planter sizes for interior landscaping (4, 8, 11, 14, 27, 28, 29), with large trees
restricted to the largest planters. Placing trees in an elongated planter parallel to a parking aisle wiil
promote growth by providing greater rooting volume. One of the most progressive practices found was
the use of engineered soils in parking lot planters (27). Though effective, it may only be feasible for
communities that value trees enough to justify the increased costs.
Davis' guidelines describe site preparation and irrigation installation but with less detail than other
codes. Water management is especially important for the establishment and survival of parking lot
trees. They are often bound by pavement on all sides and are subject to increased glare and heat from
vehicles. Portland (28) not only describes a range of planters but also three different irrigation systems.
Cities may also require the use of low-water plants (18, 24). San Francisco (33) requires a minimum of
20% permeable surfaces in parking lots and that landscaping adhere to the Water Efficient Irrigation
Ordinance (Chapter 63 of the 5an Francisco Administrati�e Code�.
Most cities list these requirements in their municipal codes, which could be difficult to update regularly.
An alternative is to provide tree or parking lot design manuals with details not appropriate for code (12,
14, 27, 28, 31�. Landscaping code can refer developers to the manuals, which contain language such as
"shall" for required practices and "should" for recommendations. The Palo Alto Tree Technicai Manual
and the Sacramento Shading Guidelines are respectively the best examples of general and specific
manuals found during the study.
Code should be detailed enough to ensure that canopy coverage is achieved but also offer flexibility. A
few cities are explicit in this regard, but none so much as Lewiston (20). Its code states that "it is not the
intent...to inhibit creative solutions to land use problems. An alternative design or modification
[is]...allowed with...approval." Modifications should be allowed if they improve upon existing
requirements or where the property cannot accommodate the required trees. Examples of code
flexibility encountered in 13 cities are described below.
f E:?
Substitutions
• Trees with other plant materials
o Los Angeles (21): up to 50% may be substituted with vine-covered ramadas
o Agoura Hilis (1): up to 20% may be substituted with shade structures or amenities
• Off-site mitigation or in-lieu fee (1, 14, 23 19, 28, 31, 39)
Variahle credit
• Bonus for placement along western perimeter (8)
• Preservation of qualifying trees can substitute for credit (9)
• Paims get limited partial credit (11)
Otlier
• Islands can be placed further apart if size is increased (11)
• Diversity restriction is waived for trees planted in excess of minimum (11)
• Extra or preserved trees can reduce parking spaces required (20, 28)
• Points system to allow planners to meet requirements as desired (21, 25)
Substituting trees with photovoltaic (PV) structures can be a contentious subject. Although PV systems
simultaneously shade and produce electricity, other benefits such as evaporative cooling and
greenhouse gas reduction are lost. Municipalities should carefully consider allowing this substitution.
� „�� ar �r,
Regardless of how detailed or progressive code is, compliance is unlikely to occur without enforcement.
Several methods of enforcement may be used, ranging from pre-construction approval procedures to
perpetual maintenance requirements.
Davis is limited by resources. With one urban forester in charge of the city's trees, there is no other
qualified staff to oversee the development process. Scheduled inspections by staff may work for cities
with sufficient manpower (9, 14), while those more limited can transfer the work to credentialed
professionals hired by the developer (9, 27). Palo Alto (27) is especially stringent, requiring that an
arborist and landscape architect be hired at the very beginning of a project to prepare and sign reports
throughout.
A more common practice, found in 5 of the codes, is to require monetary deposits to guarantee
Iandscape quality for a fixed period. The deposit can be calculated in several ways. Fayetteville (14)
requires $675 per tree, which covers the costs of purchase, installation, and three years of maintenance.
Leesburg (20) requires $990 per tree as the cost to establish a new tree with 20 year canopy area. Palo
Alto (29) requires 150% of replacement value per tree in their Open 5pace District. Portland (29) bases
mitigation fees on market value, which allows for regular adjustment. If a developer or owner fails to
bring the landscape to standard within the time specified by the city, the deposit is forfeited and used
for tree planting or maintenance. A separate account may be set up to hold the funds (14, 19, 27, 28);
Fayetteville (14) does not allow this money to revert to the generai fund. Unfortunately, deposits
19
guarantee care during establishment but trees may be neglected, damaged, or removed thereafter if
enforcement does not persist. This is problematic not oniy for young trees, but also for established
trees that are to live beyond the shade enforcement date. Palo Alto (29) instead requires indefinite
maintenance of the landscaping, regardless of change of ownership of the property.
.Y". . .. �..�.r
Of the seven cities contacted, two were selected for further examination. Staff from Fayetteville, AR
and Palo Alto, CA provided detailed information about their practices.
Table 3.5: Case study cities, including Davis
City Area Population Contacts Notes
Davis, CA 10.5 mi2 66,000 Rob Cain, Urban Forest Home to University of
Manager California, Davis
Fayetteville, AR 55.2 miz 77,000 Derek Linn, Urban Forestry Home to University of
Program Arkansas
Palo Alto, CA 25.8 mi� 66,300 Walter Passmore, Urban Home to part of
Forester; Dave Dockter, Stanford University
Planning Arborist
f- 'i,`r� �'
The code contains two ordinances, one for landscaping (Chapter 177) and the other preservation
(Chapter 167). Overall existing site canopy of 10-30% must be preserved on development projects and
is independent of landscaping requirements. There is no parking lot shade regulation but the
landscaping manual recommends planting trees that will provide 50% canopy. Parking lot landscaping is
accomplished with traditional code, with perimeter and interior landscaping required for lots larger than
a minimum size. Plantings in the interior must be placed in islands or elongated planters. Trees are
required as buffers and along entrance drives to parking lots.
Developers are referred to the "Palo Alto Tree and Landscape Manual" that includes a list of trees
suitabie for parking lots, as well as species that are sensitive to construction disturbance. Where
preservation or minimum canopy requirement cannot be attained, the developer can choose on-site
mitigation, off-site preservation or forestation, or contributions to the Tree Escrow Account. This fund is
dedicated to tree planting and maintenance activities and does not revert to the general fund.
According to Derek Linn of the Urban Forestry program, this money has been used to plant over 500
trees since 2010.
A 2012 Urban Tree Canopy Assessment found that the city had a"net loss of approximately 1.5% of its
canopy since 2002," (Linn, personal communication, 2013) a loss that would have been higher without
the existing ordinances. Fayetteville demonstrates that shading code is not required for success of
parking lot plantings.
The correspondence with Derek Linn can be found in Appendix 4.
20
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Palo Alto was the second most expensive city in which to live in the US in 2010. Community values and
higher land prices give the city more leverage against developers in accomplishing its tree goais. The
"Palo Alto Tree Technical Manual," written by Dave Dockter, addresses all aspects of trees in
development and includes parking lot shade as an appendix. Parking lots must attain 50%canopy in 15
years, with 50°/o of the perimeter trees counting towards the total. To receive shade credit, parking lot
trees have an additional engineered soil requirement. The manual has very detailed requirements and
references specific work standards, rather than a general American National Standards Institute (ANSI)
or International Society of Arboriculture (ISA) standard like most codes.
Preservation is heavily emphasized with three different categories of trees. A project arborist and
landscape architect must be involved from the very beginning of the development process to ensure
that preservation measures are sufficient. They are to prepare tree inventories, landscape plans, and
reports. They must also sign off on inspections before the Certificate of Occupancy is issued. Since site
inspections are performed by non-city professionals, city resources are conserved.
Palo Alto is currently able to fulfill its urban forestry goals with general funds. Public care permits (which
allow residents to maintain a city tree) provide additional money to the tree fund. The city has at
minimum three full-time ptanning staff, which oversees the stringent approval process. To facilitate the
work, the PEann�ar"�s�(c���lkao;; (an index of conditions for rejection) is provided and tailored to individual
projects. Following installation, property owners must maintain landscapes according to code even
after change in ownership.
The approaches have been effective for the respective cities. Neither can be considered a"better"
approach since there are many factors that can limit the local feasibility of these methods. Rather, they
demonstrate measures that can be taken to achieve parking lot shade goals.
21
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The canopy status of a parking lot is the most important piece of information needed to enforce shade
regulations. Previous Tree Davis surveys provided this information for a sample of Davis parking lots,
some of which were revisited to examine progress after six years. Realistically, field surveying is too
time and labor intensive to be practical, especially when conducted regularly to provide updates to city
staff or property owners. The i-Tree Canopy tool, designed by the USFS to classify vegetation and paved
surfaces, was explored as an alternative for remote analysis of parking lot urban forests. Unfortunately,
neither method provided useable data because of various problems. This chapter discusses difficulties,
qualitative findings, and updated protocois (should surveying still 6e an attractive option).
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The 11 parking lots from the 2007 Tree Davis survey were selected for this study, representing a
diversity of commercial uses and sizes (Figure 4.1�. The 10 lots from the 2006 survey were not used
because shade plans and individuai tree data had been lost.
Figure 4.1: 2013 survey sites.
Only the lots indicated by the green markers were completed.
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Maps for field surveying were prepared using shade plans and GIS parking lot data from the c;ii�l7sitr�.
Individual parking lots were exported into separate layers in ArcGIS and modified to match the 2007
survey areas. Because the earlier method of calculating area was uncertain, parking lot shapefiles were
tx�
changed to include the planters — a violation of Davis' shade regulation. The rationale is that planters
are nevertheless shaded and it eliminated the steps of ineasuring and subtracting planter area from
canopy area. Trees were manually plotted according to previously assigned tree numbers. Data sheets
with the tree numbers, species, and 2007 measurements were used to record information in the field.
Measurements were transferred to Microsoft Excel for calculations. (Although some tasks could be
performed within ArcG15, skill limitations of future workers were considered in selecting the primary
software.)
Another Tree Davis intern assisted with tree canopy measurements in October 2013. Surveys were
conducted in the afternoon, ranging from 3-5 PM. Canopy diameter was taken as an average of
measurements made with a tape measure in 2 perpendicular dimensions. Shaded area was calculated
by multiplying total canopy area by the shade credit (0.25, 0.5, 0.75, or 1) contributed by each tree.
Partial credit was given to trees with overlapping canopies or where only part of the canopy shaded
parking space. Shade area of all trees were summed and divided by the paved parking area (derived
from the GIS data) to determine percentage shaded. Major problems that could be obstacles to
compliance were also recorded. Diameter (at breast height, or DBH) of the trunk was not measured
because there was no previous data for comparison.
. . ���� �
The i-Tree software suite was developed by the USFS for analyzing urban forest benefits. i-T� ��G= �'3�>�
can be used to assess canopy coverage based on a sample of points.
Figure 4.2: i-Tree Canopy interface
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23
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GIS shapefiles were modified via instructions from the i-Tr��..C=_�e�opv t'oraaxn and uploaded to the online
tool. Each shapefile represents a parking lot and is overlaid on 2012 satellite imagery. The operator
selects classes of interest (e.g. tree, non-tree) and is prompted to categorize random points into the
selected classes (Figure 4.2�. Canopy cover percentage and standard error is displayed on the upper
right, so the operator can sample as many points as needed tor the desired confidence level. The
number of points sampled for this study varied but approximated a 5% error rate, with the exception of
an especially sparse lot. The data was then compared to canopy percentages calculated with field
measurements.
�� �`_
Measurements of five parking lots were completed before a progress presentation to the Davis Tree
Commission on October 17, 2013. Average field surveying rate was 41 trees per hour. Table 4.1
contains canopy coverage of the five lots as determined in 2007, 2013, and by the i-Tree Canopy tool.
After discussing problems and concerns about the utility of the data, surveying activities using either
method were terminated before the remaining lots were assessed.
Table 4.1: 2013 Results of field and i-Tree surveying
Site Compliance %Shaded %Shaded %Shaded Standard Error
Date (2007) (2013) (i-Tree� (i-Tree)
Davis Commons 8/19/2012 26.81 37.76 41.2 S%
University Mall 10/31/2012 19.07 17.95 46.� 4.98%
Konditorei 10/12/2014 20.24 26.67 40.8 4.96%
Oak Tree Plaza 1/18/2015 10.56 9.67 27.9 4.84%
Davis Home Trends 8/23/2017 0.93 3.34 4.08 2.89%
The 2007 study projected that three of the parking lots (Konditorei, Davis Home Trends, and University
Mall) would 6e compliant after 15 years. The validity of the prediction is confounded by issues
discovered during this study, such as inaccurate area. As of October 2013, University Mall and Davis
Commons have passed the compliance date but neither had attained 50%shade. Wong (1996) had
previously concluded that the University Mall parking lot had not actually been designed to comply.
The i-Tree percentages are more similar to canopy coverage calculated using the 2007 areas (Table 4.2,
column 6), despite being based on the 2013 shapefiles that span a larger area. Since the imagery used
for i-Tree was taken in 2012, pruning may have occurred in the interim. Unknown factors such as this
render the methods incomparable. These were some of the issues that made it difficult to provide
accurate data for city staff or to confidently draw conclusions. Therefore, 15-year projections, data
analysis, and surveys of the remaining lots were not attempted. Fortunately, this component provided
valuable qualitative information.
iZ!
�t� ir�.i,a..i:.>
�€. g{ 4`k�.4_��,�:
To illustrate a significant problem encountered during surveying, Ta61e 4.2 compares canopy coverage
derived from the areas used in the 2007 and 2013 calculations. Sometimes, the 2007 areas were copied
from the original shade plans, which often did not match existing modified lots. In instances where the
landscape pian didn't include area, the method of area calculation was unclear. Because of the
uncertainties, the areas derived from the city GIS data were used for the 2013 calculations.
Table 4.2: Comparison of shade coverage based on 2007 and 2013 areas. Shade calculated using 2007
areas is overestimated, since the 2013 areas were determined using ArcGIS and can be considered more
affllY�tP
Site Area Area % Shaded % Shaded % Shaded % Shaded
(ftz, 2007) (ftZ, 2013)* (2007) (2007)* (2013) (2013)*
Davis Commons 68,819 75,821* 29.54 26.81* 41.60 37.76*
University Mall 94,800 213,601* 42.97 19.07* 40.44 17.95*
Konditorei 9,100 9,312* 20.71 20.24* 27.29 26.67*
Oak Tree Plaza 71,200 194,746* 28.90 10.56* 26.46 9.67*
Davis Home Trends 8,537 33,793* 3.69 0.93* 13.20 3.34*
* Asterisked values were derived from or calculated using ��s vaiues. �von-asrensKea vaiues are uaseu
on areas used for the 2007 calculations and included derivations which were ambiguous and could not be
confirmed.
Other problems stemmed from attempting to use methods and data from earlier studies. Materials
from the 2007 survey were frustrating because of poor quality control or lack of documentation. The
latter made it difficult to accurately replicate methods, such as paved area calculation, and were
ultimately discarded. Quatity issues included misidentified species and poor field records, such as when
new trees were measured but their locations unrecorded. Several lots are actually only sections of the
complete lot but were selected because of available shade plans. The shade plans were also inaccurate
for lots that had been modified.
The GIS data was indispensable for the study. It contains every parking lot in Davis and excludes
planters per the shading guidelines. In the Davis Commons case, however, the entryway to the lot was
excluded despite being considered paved parking area. The shapefiles were modified in such cases to
match the ordinance though it was then violated by including the planters as discussed above. Persona
interpretation should have been avoided by consulting city staff to determine why the GIS data omitted
these areas.
� ,. -
The strength of the i-Tree Canopy tool is that it requires minimal training. However, there are inherently
limiting factors that may render it unsuitable for canopy assessment. The satellite imagery is recent but
resolution is poor (Figure 4.3). Depending on when the imagery was taken, trees may not be in full leaf
25
or shadows may interfere with objective assessment. Additionally, the sampling crosshairs may be
centered over the boundary between shadow and canopy, further obstructing classification. Further
studies must be performed before making conclusions on its utility.
canopy or paving? When was imagery taken?
"�' .S,e;�:e' €1
Trees should have been measured when the
canopy was in full leaf to avoid confusion
between dieback and autumn leaf drop.
Unfortunately, the assisting Tree Davis intern
was not hired until October. Attempts at solo
surveying were inefficient and difficult in
cases where vehicles were in the way. Two
surveyors also appear to discourage extended
inquiries from curious passersby. DBH tape
measures are more suitable than
conventional tape measures due to flexibility
and length. DBH should be measured to
check whether trees have been replaced and
to track actual growth, since the canopy can
be pruned at any time.
The major limitations are time and trained
labor. In addition to time spent on actual
measurements, surveyors also have to
accommodate traffic and field questions from
passersby. Since the latter presents an opportunity for outreach, surveyors shouid also be trained to
answer questions. Unless a stringent training process can guarantee consistent data and observations
from all surveyors, a quality control survey by knowledgeable personnel is recommended. In general,
the surveyor's skiil in GIS, tree knowledge, species identification, detailed observation, and record
keeping must be considered in determining the cost-effectiveness of a survey.
Field surveying is superior to remote analysis in that it provides information about conditions that may
affect growth, but other obstacles to compliance are not so easily observed. �deally, an interview of
property owners or managers would accompany the survey to provide additionai data. However, based
on the methods used in this study, neither field surveying nor i-Tree appears to be reliable enough to
justify penalizing non-compliant property owners. However, staff consistently expressed a desire for a
reliable method to assess all lots to establish a baseline of parking lot canopies. A field surveying
protocol (Appendix 5) was developed based on findings from this study. A GIS protocol could not be
successfully designed because of limitations imposed by imagery resolution and recency. It is likely that
there are various methods that can be used within a city's resource limitations, and the surveying
protocol presented provides a single starting point.
C�".
Figure 4.3: i-Tree problems. Shadow or canopy? Sparse
Ch����r �. ���:s���a ��ci��i �'��ctic��
This chapter is based on findings discussed in previous chapters. Consider incorporating promising
practices from Chapter 4 after modifying them to suit regional values and municipal resources.
Municipalities without a shade ordinance should read the "Trees, Parking and Green Law" (Wolf, 2004)
paper for a complete overview of the information in this section. Landscaping code should include a
purpose statement to "make community values explicit, generate support for the legislation, and guide
lawmaking" (Wolf, 2004). The statement could be categorized according to several themes, such as
visual quality, mitigation of annoyances, regional character, property value, and ecological services.
A shade ordinance is not a substitute for but complements traditional and interior landscaping code. It
magnifies the function of trees in parking lots by emphasizing shade and ecosystem benefits. The most
common regulation is to achieve 50% shade in 15 years. Shade reguiation may also be modeled after
Orlando (25), which uses tree points. If resources are available for additional enforcement activities,
consider setting progress markers at regular intervals (e.g. 10% coverage in 5 years, 25% in 10 years).
The ordinance should require a shading plan, offer a list of suitable tree species, describe flexi6le
alternatives, and elaborate upon enforcement methods. If perimeter landscaping is required for all
developments, it may be prudent to set a minimum lot size to which the shade ordinance will apply.
This will lessen the enforcement load on staff provided that the perimeter trees contribute shade.
::�i,�erf, r;t:_ .r, r;,
If a landscape and tree manual does not exist for the city, create one. The manual can include additional
details not appropriate for code and a�lows for regular updates without city council approval. Shading
guidelines should only be a part of this manual, since it should be the ultimate reference for trees and
landscaping in development. Examples can be found on the websites of Fayetteville (14), Palo Alto (27�,
and Portland (28). If the community is not "politically committed to extensive regulation of trees and
landscape," the city could offer a handbook of best management practices (BMPs) with "technical
references...in an informative manner" for those who wish to implement more sustainable practices
(Wolf, 2004). Most importantly, the manual should be updated regularly— perhaps with a mandate in
the municipal code like Fayetteville (14) —to replace outdated information and to implement new and
effective methods of enforcement.
:� ta. -7� �pfar
A shade plan is valuable for both developers and city staff because it ensures that lots are designed to
meet regulation. The city should provide resources that facilitate this process to encourage compliance.
Shade is generally assessed according to canopy area at the time of enforcement, with partial credit
given to overlapping and perimeter trees. Shade coverage is calculated by dividing canopy area by
paved parking area. When deciding on a coverage requirement, consider specifying more trees per area
or greater canopy area as trees often underperform in typical parking lot conditions. A more effective
requirement may be to specify improved growth environments.
27
Paved parking area must be explicitly defined. Bentonville (4) includes pianters in its shade calculations,
while Davis (12) does not. The Davis method is more complicated and overestimates shade because the
guidelines do not require that planter area be subtracted from canopy area. Formulas may be used to
automate calculations, but it is an additional step that excludes the first spaces to be shaded by growing
trees.
Emphasize preservation over clear cutting to maximize immediate benefits in new developments, but
preserve only healthy, structural�y sound, and desirable specimens. Fayetteviile (14) provides a list of
trees that are sensitive to construction impacts, a valuable resource since damage may take years to
manifest. Such selective preservation will maximize benefits at reduced cost.
' � ; . ,z� ', ; ; .: �
A list of species suitable for parking lots should be provided, with projected canopy sizes at the time of
enforcement. Growth projections should be more conservative since parking lots are not ideal for tree
growth. When constructing the list, consider as many aspects of suitability as possible including soil,
climate, growth characteristics, longevity, ultimate size, and aesthetics. At minimum, trees should
tolerate restricted root spaces and low water. Discouraged species may include those that attract birds,
are high maintenance (e.g. brittle wood or excessive litter), have sparse canopies or disruptive roots, or
are susceptible to pathogens and pests (especially insects that produce honeydew). Some cities provide
additional tree lists, especially if variable or bonus credit is granted. These lists could include native
trees or species tolerant of pollution, salt, recycled water, and drought. There may also be lists that
prohibit species that are invasive, serve as hosts for serious pests or pathogens, or have narrow crowns.
Providing extensive lists allows a city to promote diversity while restricting the trees that can be used.
Parking lots will thus be protected from major canopy loss caused by species-specific decline.
. ,r.r�r>, r r ..� r
Specifications should include planting details that enhance tree growth in parking lots, where effects of
glare, heat, vehicular damage, and restricted soil volume may be greater than in other urban settings.
Mandating larger planters to increase rooting volume translates to more aboveground growth.
Decreasing overhang allowance or specifying shrubs in planters protect trunks from bumper damage.
For example, a 2' overhang may be sufficient for a newly planted tree in a small planter but could permit
vehicle contact with a mature tree. If turf is used for interior landscaping, trees placed in the same
planter should be matched to the irrigation regime or they will suffer from overwatering. Irrigation
systems should be as detailed as appropriate. The system design should not deliver water inside a tube
that would conduct water past the root zone.
Progressive communities may embrace design elements such as rain gardens, permeable surfaces, and
structura� soil. Rain gardens are vegetated, low-lying areas that collect and retain runoff to increase on-
site biological treatment by soil microorganisms. They can be impiemented in new or retrofitted lots
and may replace lawns to reduce irrigation and maintenance. If encouraged, an additional list of trees
tolerant of periodic soil saturation and prolonged dryness should be provided. More progressive
�
communities may consider specifying permeabie paving or structural soil. Permeable surfaces increase
water infiltration and oxygen exchange, and structural soil reduces compaction and increases pore space
for roots. While the use of such aiternative methods is gaining traction, costs may still be prohibitive
compared to the use of conventional paving materials.
_ . , .�.;i'''€`
Flexibility should be allowed within reason. Common practices include substitutions with vegetated
shade structures or tree preservation in place of new plantings. Non-vegetated shade structures such as
photovoltaic arrays are not recommended because they do not provide as many benefits as trees.
Ultimately, however, it is the city's decision. Cities that promote non-vehicular modes of transportation
may permit fewer parking stalis if installed landscaping exceeds minimum requirements. Alternatively,
cities that charge stormwater fees based on paved area, like Charleston, SC, may grant partial fee
waivers for additional landscaping. If habitat conservation is desired, clumping can be allowed to
preserve trees that may suffer if isolated individually, but this practice may not increase shade coverage.
If a specific shade percentage seems too difficult to attain or enforce, aim tor a lower or modified
requirement. Shade coverage can still be attained by combining several traditional landscaping
practices. For example, a city may specify interior landscaping and a minimum number of trees based
on area or number of parking spaces. When this specification is linked to a requirement that each
parking space be within a maximum distance from a tree, it effectively distribute trees across a lot (24).
However, unless a maintenance standard is set forth, unnecessary pruning or insufficient tree care could
reduce canopy coverage. The code must require practices that enhance tree growth and encourage
proper maintenance to maximize and sustain canopy size (6, 11, 14, 27, 28). Keep in mind that some of
the cities with progressive or effective codes did not have extensive shade regulations, but other
stringent requirements ensured the success of tree plantings.
Encourage creativity as much as possible, because the most effective practices from innovative
designers can be incorporated as a requirement. Consider mandating as many practices as will enhance
the spatial distribution and proper growth of trees without rendering the process unwieldy. A points
system, like those used by Los Angeles (21) and Orlando (25), or something similar may help encourage
creativity while tracking basic requirements.
d' `�-',+.iT�;,, ,.
Enforcement is the most difficult part of implementing any regulation. Municipalities must fairly and
accurately assess parking lot tree canopies before penalties can be imposed, but many are restricted by
resources.
A shade regulation can pose problems for enforcement if it is not specific enough; yet, great specificity
also casts doubts on its enforceability. For instance, most cities do not state the time of day when a lot
has to be 50% shaded in the year of enforcement. 5pecifying noon on the summer solstice (8, 21) is an
improvement but may still seem arbitrary to a developer. The requirement implies an assumption that
the sun is directly overhead and therefore provides maximum shade. In reality, this varies with latitude
29
and even if true, would be the case for only a few hours. What staff and developers must understand is
that the exactitude of the specification is for fairness to the property owners and for feasibility of
enforcement for the city. Shade cast may be greater at another time, or where tall narrow trees are
strategically placed to provide more shade than is expected of their canopy dimensions. The most
important detail is that there are enough healthy trees to provide a close approximation of the
requirement. Incentives or bonuses for tree placement along the south and west perimeters can
enhance shading without increasing demands on the developer. Change in ownership is another
important factor, which is where perpetual maintenance requirements are beneficial. The new owner
must continue to meet the requirements, even if the trees were in poor condition at the time of
purchase. This could increase pressure on property owners to maintain trees in good condition to
protect their future interests. Explicitly discussing contentious points will provide justification for any
method of enforcement adopted by a city.
A unique situation was encountered during the field survey of the Davis Commons lot, where several
perimeter trees on the original shade plan are actualiy part of the UC Davis Arboretum. Should the
Arboretum prune or remove those trees, shade reduction would occur beyond the owner's control. In
such cases, there should be leniency so property owners are not unreasonably penalized.
To enforce shade regulations, a city would ideally conduct a shade analysis of every lot to determine
compliance. Thereafter, regular analysis would have to be conducted to provide progress information
to property owners. Such analyses may be too demanding for many municipalities unless powerful tools
(such as GIS) or efficient methods are used. Parking lot shade should be quantified and compliance
progress communicated to the owner. This point of contact is an opportunity to increase awareness of
the regulation, identify issues with attaining compliance, and provide solutions to recurring problems.
In cities with recently implemented regulations, older lots comprise a subset of lots that are generally
exempt except when they are expanded or redeveloped. They will remain untouchable until compliance
is enforced for newer lots. Successful enforcement can lead to additional ordinances that require
retrofits of older lots.
Inquiries made to cities revealed that they do not monitor shade co�erage but focus on other details to
characterize the success of parking lot urban forests. These could be pre-planting practices that create
conditions conducive to growth or may occur post-development to ensure that plantings thrive. If pre-
development measures are conducted by staff, the urban forester or arborist must be an officially
designated reviewer in the process. Otherwise, the planning staff must have "proper technicai
knowledge and commitment to the purposes of the code (Wolf, 2004)." If this is not feasible due to lack
of staff, the work can be transferred to an external entity. Code may require that an accredited arborist
be involved in the project from its inception. The arborist can provide professional input, inventory trees
for preservation, and perform inspections.
If post-development enforcement is preferred but limited by resources, consider collaborating with local
non-profit urban forestry groups. They are present in many communities and command a sizable
volunteer force for tree planting, care, and outreach activities. Volunteers can be used for parking lot
fKil
surveying, but this method of monitoring is not recommended. Sophisticated equipment and highly
trained personnel can increase the accuracy and precision of canopy measurements but have a
proportionately higher cost. A field surveying protocol is included in Appendix 5.
Non-profit organizations are more appropriately used for outreach. They often organize tree-related
events on city property, which provide a forum for dispensing information about proper planting and
care. Volunteers who attend these events can disseminate information beyond the event to family or
friends. Occasionally, events are conducted under contract with the city. Property owners could
similarly contract out tree care (during the establishment period) to the group for lower cost
maintenance. Businesses would also benefit by drawing volunteers to the area. Whether this is
permissible may depend on city code.
Regardless of the methods used, there must be sufficient funds to support them. A"tree bank" should
be created to hold funds for tree-related activities without reverting to the general fund. Imposing a
deadline after which unused money is refunded is fair to developers. Suggested sources of funds
include: damage compensation; permit/plan review/inspection fees to be used for site visits; a fixed
percentage of developers' fee; fees from non-municipal utilities that may impact trees; donations or
corporate sponsorships; utility bill donations (e.g. where a resident can simply check a box to donate an
amount); fundraising; and sales of firewood, mulch, and wood (Davey, 2006). This "bank" will be
especially useful in cities where urban forestry does not receive enough money from the general fund.
Finally, enforcement must continue until shaded parking lots become the status quo. Monetary
deposits guarantee that trees perform during the establishment period, and successful shade
enforcement can guarantee tree canopies for 10-20 years. What then? Although a city with sufficient
resources can continue to monitor and enforce, outreach and education may be most effective. �wners
and developers aware of the benefits of trees are more powerful in creating change than staff imposing
penalties. There must be a heavy investment in disseminating knowledge about how trees properly
selected and appropriately located promote commercial success despite initial costs or sacrifices.
Signage blocked by tall trees can be used as an example. Topping to clear the line-of-sight incurs a
perpetual maintenance cost until the trees are ultimately removed. Not only are the collective costs of
maintenance and replacement greater, but the property also loses out on services provided by the
trees. Smaller and wider trees could be used with tall signage to simultaneously allow visibility and
provide shade. If signage is at a lower height, trees could be clearance pruned after a few years. An
alternative or supplement is to provide signage at shopping center entryways, which will offer visi6ility
until interior trees have grown tall enough to clear signs. Effectively communicating that the concerns
and values of business owners are understood and have been considered will encourage compliance.
Additional effort in appealing to the concerns of other interest groups will also pay off by gaining public
support against non-compliant owners.
As mentioned previously, there is no standard green law, for good reason. These suggestions should be
adopted only if locally appropriate and valued by the community.
31
Beatty, R. A. 1989. Planting Guidelines for Heat Island Mitigation and Energy Conservation. In K. Garbesi,
H. Akbari, & P. Martien (eds.), Proceedings of the Workshop on Saving Energy and Reducing
Atmospheric Pollution by Controlling Summer Heat Islands. Berkeley, CA: Lawrence Berkeley National
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City of Davis, 2000. Parking Lot Shading Guidelines and Master Parking Lot Tree List. Davis, CA:
Community Development Department. h[tr�� `cr,rt�er���ni�
rE� „�l,�:�r�e���fciavis.crr� E�ne�li�,�CJ�f��^9tI1Jc�ci.r�p„ts�l�t��i'C(3�P(G�r7r�rn�/Fs�rrrislPark€���-Lc�t
�i�11f;i�..,.�.tiAlP�C.'�;C7f__m� __'S.�iii�
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Staff of Fayetteville, AR.
13ttp:f��;�uw.ac��essf�+���tevi�I�.or�Iaovernrr3en�ipianr�in `dt�cuet�en[stlanclsc�K�e n�ar�a�aalJE.�r��isca�e%20
iVlan�aal3��C7 r/��C��a'#o�t��i�} t2�3C39 _;�"�� ��i. ;c1f
City of Sacramento. 2002. City of Sacramento Parking Lot Tree Shading Design and Maintenance
Guidelines. Sacramento, CA: City Planning Department.
hitt?:/fo���rvw.c€tvofsac;r��rrser�ta.o€�� ��ar3<sam�rec�ea�iinr�[}���dc���f��SHr'�C7l�� �;tiiC�ELI�iES �J�a-(75-03.pcff
Davey Resource Group, 2006. Urban Forestry Management Plan for Town of Leesburg, VA. Kent, OH:
Davey Resource Group. P. 93-96.
f�ttlr�/L'��vwvv.l�e<�P�u�€;v�.�s_svl��,ac�ufs��(���wl)��� �� �_�nt_�s.px?�'uru�nc���;��1���1C�i�3_
Elliot, K. 1988. Tree Shade in Urban Parking Facilities: An Evaluation of Parking Patterns and the Davis
Mandatory Shade Ordinance.
EPA— Environmental Protection Agency. 2003. Smog— Who Does It Hurt? What You Need to Know
about Ozone and Your Health. Washington, D.C.: author.
http://www.epa.gov/airnow/hea Ith/smogl.htm I
Laverne, R. J., & K. Winson-Geideman. 2003. The Influence of Trees and Landscaping On Rental Rates at
Office Buildings. Journal of Arboriculture 29,5281-290.
Litman, L. 2002. Where Are All the Cool Parking Lots? Center for Urban Forest Research. Davis, CA: USDA
Forest Service Pacific Southwest Research Station.
McPherson, E. G. 2001. Sacramento's Parking Lot Shading Ordinance: Environmental and Economic
Costs of Compliance. Landscape and Urban Planning 57:105-123.
32
NASA— U.S. National Aeronautics and Space Administration. 2003. WhaYs Hot in Huntsville and What's
Not: A NASAThermal Remote Sensing Project. 1�tt : yvw�nd�hcc.rr�sfr.r�<sa.�ov/Iand heati.s.l�ilcatisl.htrr�
Palo Alto. 2001. Tree Technical Manual: Standards and Specifications. City of Palo Alto, CA: Department
of Planning and Community Environment.
ht.t,p,s:�lsr.�vwl.cifV�"�f�aloa(to ors�(c.ivRt��fife�;<�n�Cfk�(c�L7dfc�ad.as�"�ilak�9E) �3�5
Scott, K. I., J. R. Simpson, & E. G. McPherson. 1999. Effects of Tree Cover on Parking Lot Microclimate
and Vehicle Emissions. Journal of Arboriculture 25,3:129-141.
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American Meteorological Society.
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Georgia Forestry Commission, Urban and Community Forestry.
is,kt�';/fli,�+rr;n.i�d�t�Freurst��in.isi%u tr*3ris.pc�r.t�tiori_ht�r�l
Wong, T. 1996. Parking lot shade study: A critical examination of Davis Parking Lot Tree Shade.
htt�: "v�ti�r��,_i�.ft_E"s us[�as��Ipr«�;ra€r€> G��sci�ue�jres� K�rri�(stsadies c�etail,,sh�Pry;lC� =27
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City of Davis and USFS Western Center for Urban Forest Research and Education.
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f��tp:/1dc.;nrat�r,uses.�ov(f�r�jfloads.Y�km(
33
r�������r�i� � w Z0�€�3 � Z���7 �'���•�i��; L��ts
Address Name Compliance Paved area Shade Shade Notes
date (ftz) area (h�) cover
1411 W Covell Blvd The Marketplace 12/26/Z001 223,386.00 5,547.00 2.48% Failed to obtain
required shade
ZSS Cousteau Pl 7/14/2015 72,580.00 9,422.00 12.98% Not compliant,
trees need to be
replared
2795 Pena Drive 8/31/2008 66,484.00 8,180.00 12.30% Not compliant
trees need to be
replaced
P.O. Box 1333 Cove!( 12/30/2011 9,685.00 572.00 5.90% Not compliont,
trees need to be
replaced
202 Cousteau P! 8/21/2016 144,352.00 13,409.00 9.29% Not cornpliant,
trees need to be
replaced
1970LakeBlvd 12/21/2013 5,153.00 104.00 2.02% Notcompliant
2801 2nd St Davis Indoor Rec 6/26/2016 30,060.00 2,093.00 7.00% Not compliant
trees need to be
replaced
ZSSOSpaffordSt 9/3/2012 9,758.00 3,709.00 38.01% Compliant
2860Covell8lvd 6/14/2016 22,536.00 763.00 3.39% Notcompliant
2940Spafford5t 7/1/2014 12,928.00 3,177.00 24.57% Compliant
2000ShostaDr A�rayo 7/31/2015 19,730.00 1,498.00 7.59% Compliant
Community Park
737-885 Russell Blvd University Mall 10/31/2012 94,800.00 40,734.80 42.90% Compliant
1414 East Covell Blvd Oaktree Plaza 1/18/2015 71,200.00 20,574.10 29.00% Not compliant,
trees need to be
replaced
500 ist St Davis Commons 8/19/2012 68,819.00 15,945.00 23.00% Not compliant,
trees need to 6e
replaced
2710 E Sth St Konditorei 10/12/2014 9,100.00 1,884.50 20J0% Compliant
2300 Sth St Davis Home 8/23/2017 8,537.00 315.20 3.70% Compliant
Trends
1550 Drew Ave 9/30/2020 48,050.00 4,007.80 8.3D% Not compliant,
trees need to be
replaced
2727 Del Rio PI 3/21/2016 15,200.00 3,315.62 21.82% Not compliant,
trees need to be
replaced
1640 Research Park Dr Comfort Suites 8/10/2014 30,000.00 7,956.6D 26.50% Not compliant,
trees need to be
replaced
1771 Research Park Dr Holiday Inn 1/31/2009 19,60D.00 4,055.10 20J0% Not compliant,
trees need to be
replaced
2323 Rockwell Dr Wildhorse 4/8/2014 75,200.00 6,508.70 8.70% Not compliant,
trees need to be
replaced
1600 Research Park �r Wendy's 9/26/2010 17,425.00 9,306.95 53.00% Compliant
�vuo �i�e� are nancizea.
34
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Parking lot landscaping practices were organized into 19 subcategories. The subcategories vary in
specificity, with some encompassing others. Assigning the practices was subjective but offered a means
of visualizing the diversity of practices used.
Subcategories
• Perimeter: landscaping generally used as aesthetic or noise buffers
• Interior: landscaping for aesthetics or traffic control
• Sliding scale: requires more landscape or tree cover for larger lots
• Minimum planter size: specifies a minimum planter size (trees or general landscape)
• Planter range: specifies larger planters for larger plants
• Spatial requirement: plantings must be distributed across a lot
• Preservation: requires preservation of trees larger than a specified size
• Shade: requires that parking lots be shaded a certain amount
• Shade plan: requires shade plan for above
• Tree size: specifies minimum size of stock for planting or replacement
• Tree list: offers list of species suitable for parking lots
• Extra lists: additional information, including but not limited to: water use, native, prohibited
• Diversity: sets a maximum use per genus, species, or cultivar
• Maintenance or replacement requirement
• Substitutions/flexibility/mitigation: allows alternatives such as off-site mitigation where planting
sites are insufficient; permits substitutions of landscaping for other structures or amenities; etc.
• Deposits: requires monetary deposit, generally to guarantee landscape maintenance
• In lieu fee: collects fee if requirements are not met or if regulations are violated
• Tree Fund: holds money for tree activities
• Manual: offers a landscape/tree manual or shading guidelines
The following table counts the practices used by each city. Total practices per city are in the third
column and total cities per practice are in the last row. Those marked with "1" ciosely follow the
subcategory descriptions, while "-1" indicates a deviation. For example, Portland, OR has a sliding scale
requirement not for landscaping but for contributions to the Tree Fund. Davis, CA received a"-1" for
diversity since its code recommends 6ut does not require species diversity in parking lots.
35
Total Sliding Planter Planter Spatial Shade Tree Tree Extra Maint. or Subs/flex/ In lieu Tree
# City Practices F�rimeter Interior scale size range req Resery Shade Plan size list lists Diversity replace mitigation Deposits fee Fund Manual
� Agoura Hllls, CA 4 1 1 1 1
2 Austin, TX 0
3 Bellevue, WA 4 1 1 1 �
4 Bentonville, AR 6 1 1 1 1 1 1
5 Brookfield, WI 0
6 Burbank, GA 4 1 1 1 1 -1 -1
7 Chicago, IL 3 � � �
8 Chico, CA 5 1 1 1 1 1
9 Colorado Springs, CO 5 -1 -1 1 1 1 1 1
10 Concord, NH 3 1 1 1
11 Coral Springs, FL 10 1 1 -1 1 1 1 1 1 1 1 1
�2 Davis, CA 6 1 -1 1 1 1 -1 1 _� �
13 Eureka Springs, AR 1 1
14 Fayetteville, AR 17 1 1 -1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
15 Folsom, CA 3 � � �
16 Grand Junction, CO 6 1 -1 1 1 1 1 1
17 Indian Wells, CA 5 1 1 1 � �
18 La Verne, G4 4 1 1 1 1 _�
19 Leesburg, VA 12 1 1 -1 1 1 1 1 1 1 1 1 1 1
20 Lew iston, ID 5 1 1 1 1 1 -1
21 Los Angeles, GA 7 1 1 1 1 1 1 �
22 Minneapolis, MN 1 1
23 Nbbile, AL 3 1 � � _�
24 Nbdestq ('A 7 1 1 1 � � � �
25 Orlando, FL 5 1 1 1 1 1
26 Oroville, CA 8 1 1 1 1 1 1 1 �
27 Palo Alto, CA 10 1 -1 1 1 -1 1 1 1 1 1 1 1
28 Portland, OR 12 1 -1 1 1 1 � � � � � � � �
29 Redmond, WA 9 1 1 1 1 1 1 � � �
30 Redw ood Gty, CA 1 1
31 Sacramento, G4 14 1 1 1 1 1 1 1 1 1 1 1 1 1 �
32 San Antonio, TX 0
33 San Francisco, CA 3 1 1 1
34 Scottsdale, AZ 4 1 1 1 1
35 Suisun City, CA 0 _�
36 Tucson, AZ 1 1
37 Wasilla, AK 1 �
38 West Sacramento, GA 0
39 Woodland, CA 7 1 1 1 1 1 1 1
Sum 10 24 7 15 8 19 11 17 4 14 8 7 7 13 13 5 5 4 5
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37.04 Parking Lot Trees:
. 37.t��.�s1i�l�ppl�c��i'itv_Regulations contained within this article relate to all improved off-street
parking lots within the City of Davis. Per Section ;C3.1_5._LGJ of the Davis Municipal Code and the
parking lot shading guidelines, fifty percent of the paved parking lot surface shall be shaded with
tree canopies within fifteen years of the acquisition of a building permit. (�rd. 2099 § 1, 2002)
. 37.{)rt.€�20 P<�rki�,� I�at �fli��9in� Eree �>€�I<�c:*is.E� �i�d sl��ti�r=�; �;!a_n,..Tree selection shall be in
accordance with the provisions of the parking lot shading guidelines and the city master tree list;
only trees identified as parking lot shade trees may be planted unless otherwise approved by
the director. The tree species should be varied, but are not required to be, throughout the
parking lot.
. A parking lot shading plan and related shade calculations shall be submitted to the community
development and sustainability department along with the building permit or discretionary
project permit for all new and/or reconstructed parking lots. (Ord. 2099 § 1, 2002)
. 3, �i�i ��3Q E'��;�=<li�= i,}k �r.iarri3nt�lrx�z�.ir�t�r����c� <t���ei��r;��. Parking lot planter design, materials,
planting and irrigation details shall be as per the city tree planting and maintenance
specifications and the parking lot shading guidelines. (Ord. 2099 § 1, 20o2)
Shading Guidelines can be downloaded from 3���(corr=r,�unity-
el�velc�prn,e€�t.cit��€afr�avis.or�/Meclia f llE_F�ul;�oct�,��^nts'�'DF/��3U(F'(ai�s�ln��'f=c;rmslPar'<arrt�-Lot-
Sh�i_�I.;��;_�;ui�J�lins*s. �lf.
r������c��� �: �"c������*��c�a��c����°� �v�ll� I��z�e��� �i�z� r�f��^��yc��tt���11�, �1�
The following information is taken from an email exchange with Derek Linn of the Urban Forestry
Program. Details covered in c�de have been omitted.
Q: Your city's ordinance [has] a lot of promising ideas - options for mitigation, Tree and Landscape
Manual, and reasonable exemptions. I also saw that the Tree Escrow account has been used to fund
planting projects. Could you offer some suggestions as to how these practices were
implemented...? Would you consider the ordinance successful?
"We handle compliance by holding the owner's Certificate of Occupancy until inspections can
verify that required landscape elements have been initially installed; when communicating with the
public or owner, we try to remind them that shrub buffers and street trees are required public
infrastructure and no less important than sewer lines, curbs, or sidewalks. In addition, we look for long
term (3 year) compliance on street and mitigation trees through required surety. At the 3 year mark
after CofO, if 9�% of street and mitigation trees are found in Fair/Good/Excellent condition, the owner
receives their surety back. If we find less than 90%, the owner is required to replant to bring the total
back to 100% before surety is released. if the surety is forfeited, the City is to plant the trees. After a
few too many surety forfeits, staff proposed and City Council recently approved an increase in the value
of a street / mitigation tree. The original rate of $250/tree was upped to $675/tree to better refiect
current costs of purchase, installation, and 3 years of maintenance. Hopefully this will further
encourage owners to keep their trees a�ive during this establishment period.
You mentioned the Tree Escrow account as well. We will be planting 117 public street trees this
autumn with this fund; I think we have planted a little over 500 trees with this account since we started
the projects in 2010. As the number of trees outgrew City staff, we have begun using some of the
Escrow fund to pay for a vendor to water and mulch the trees.
As the landscape and preservation ordinances predate me and my supervisor, we can't speak at
detail on the initial establishment or extent of involved stakeholders in the implementation of these
ordinances.
While our Urban Tree Canopy Assessment in �ate 2012 found that the City had a net loss of
approximately 1.5%of its canopy since 2002, iYs difficult to imagine what the loss would have been
without the ordinance requirements. I think the preservation ordinance has been fairly successful in
maintaining our tree canopy, but there is certainly room for debate about improving it."
Q: How often are inspections conducted, and by which staff?
"Inspections are conducted a minimum of two times on a property. The initial inspection for
CofO mentioned above is conducted by the Urban Forester/Landscape Administrator. They make sure
required trees are installed properly and then sign off on the CofO. Inspection #2 for the property
comes a6out two (2) months before the 3 year maintenance period passes. So any inspections we
complete today (Oct 1st) should be for sureties that expire around December 1st. This two month
buffer from expiration date gives us time to communicate with the owner before the surety expires. If
�c�:]
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less than 90% was found and trees are to be re-planted, we want to make sure the owner has time to
either extend or re-issue another bond to extend this surety period (Of course if the surety was in the
form of a check, we can just continue to hold the money). These 3 year inspections are conducted by
the urban forester or by another support staff person, with a quick review by the urban forester. In the
past we have had assistants or summer staff help with the 3 year inspections. We have probably echoed
some of your concerns with lack of finances and limited staff. We also only have one urban forester, but
probably could really benefit from having two*. Having assistants help with these 3 year inspections
has helped keep things rolling."
*As of December 2013, Fayetteville has 2 urban foresters. A department-funded reorganization
provided support for the additional position.
Q: Does the Escrow account also pay for staff expenses, e.g. for inspections?
"Staff salaries and hourly wages typically come from a more general operating fund, but the
way the ordinance reads, it does look like escrow money could be used to pay staff wages, as long as
their time was spent focused on actions related to the intent of the Escrow account. Indeed we
currently use escrow money for acquisition, planting, and maintenance, all of which are done through
contract labor. One of the most important parts of this section is that the escrow money "(ii) Shall not
revert to the general fund". Otherwise, a city's tree money could get pulled for something else
unrelated. A couple paragraphs down in the code, you'll see that the City has 7 years to use the money
from the date it was received."
Q: What was the response to increasing the surety per tree to $675?
"Any ordinance change requires City Council approval, which invites public comment through
public meeting. I did not attend that meeting, but from what I heard it passed fairly smoothly after
justification was provided. (When required trees are not cared for and developers forfeit their sureties,
the old amount of $250 was simply not enough money for the City to acquire, plant, and maintain for 3
years, as required by ordinance when sureties are torfeited. This put an unnecessary burden and
expense on the City and taxpayers)."
39
E
��a���r�c��x 5; I#'i��c� Sa���v�yi�a�; ����tc���l
This protocol is adapted from the USFS t�arkin�_ C.c�t Shave Tr�e I��s��=ctic�r �nc� �€�r�i¢o.E ir��: Guide and
modified with field surveying experiences. Details to consider for relevance are included but not
everything in the guide is necessary to enforce shade requirements.
Shade area research (performed once per lot)
1. Download the SE��de Area �ria�,y.�es S�radsh�et from the Tree Davis Dropbox.
2. Obtain project plans from the P�anning Department. If a shade plan is not available, a landscape
plan with tree species, locations, and permit date will suffice. Verify the accuracy of the original
plan against GIS parking lot data, if available. Otherwise, qualified personnel should inspect for
changes before measurements are taken. Enter tree information into columns E and D.
3. Fill in Initial Planting Date and Current Date (cells D9 & D10, in green). # Tree 5ites Planned and
# Actual Tree Sites (celis D12 & D13) is optional. The spreadsheet will automatically calculate
Shade Area Planned at 15, Actual, Projected at 15, and Deficit at 15 when measurements are
entered (Columns K to N).
4. Conduct a preliminary parking lot inspection to confirm shade credits, adjusting them where
trees have been removed or planted. Enter these values in columns E and F.
5. Calculate paved areas as described by your local regulation. If the shade plans have paved area
calculated, confirm the accuracy of the values. If GIS data is available, the ArcG15 Geometry
Calculator function can be accessed through the attribute table. Enter this value into the F2 cell
(blue�.
Parking lot survey
1. Develop a protocol to train and assess surveyors to ensure consistent measurements and
detailed observations. Visuals, particularly of common tree probiems, will be useful for training
personnel that do not have an arboriculture background. The USFS guide provides a foundation
for training that can be tailored to the staff's priorities. Include outreach training in case the
surveyors are approached by passersby. Provide safety vests and identification of the surveyors'
affiliation (e.g. apparel or nametags with the city or organization's name).
2. For each tree, measure DBH and canopy diameter, the latter in 2 perpendicular directions. This
data should be entered into columns G and H. Work in groups of two using a DBH tape with
standard measurements on one side. The USFS guide has instructions for measuring DBH in
special cases, such as trees with a lean or multiple trunks.
3. Class size and annual growth crown radius of common species can be found in Attachment 2 of
the USFS Parl<ing Lot Monitoring Guide. Enter this information into columns I and J.
4. Inspect the conditions ot and around the trees to determine obstacles to maximum growth.
Consult the guide for an extensive list of conditions and maintenance practices to address the
problems. These can be added to Column A as comments.
A summary and graph (in the Parking Lot Shading tab) is automatically generated by the spreadsheet,
which can be given to staff or property owners. The USFS guide suggests surveying 8 times over 15
years, with greatest frequency after planting.
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