7/31/2019 Making Parking Lots More Tree Friendly: References - Fact sheet #3

1/2

January 2002 Urban Forest Research

Fact Sheet #3: Making Parking Lots More Tree Friendly

Site Planning and Design

Reduce Paved SurfacesK Reduce parking ratios to decrease the number of unused parking spaces.

K Identify peripheral and overflow parking areas, especially in retail lots,and determine the appropriate landscape treatment (e.g., perviouspaving, stormwater infiltration areas)(Girling, et al. 2000).

K Narrow the width of aisles between rows of spaces. In many cases aislewidths exceed the standard.

K Increase the ratio of compact to full-sized spaces.

K Increase use of one-way aisles, angled parking spaces, and shared parkingto reduce overall imperviousness (ULI, 1983; Center for WatershedProtection, 1998).

Promote Tree Growth

K Reduce soil compaction in tree planting areas.

K Increase tree well and planting island minimum dimensions to 8 feet.

K Require soil in tree wells to be excavated to a depth of 3 feet andamended as necessary.

K Use structural soil mix under paving to retain parking spaces whileincreasing soil volume (Grabosky and Bassuk 1996).

Increase Environmental Benefits

K Use vegetated swales instead of tree wells or convex-shaped islands totreat stormwater, promote infiltration, and increase soil volume for trees(Richman 1997).

K Convert double-loaded full-size spaces to compact spaces with a tree in

between to increase shade without reducing the number of spaces.K Reduce conflicts between trees, lighting, and signage by coordinating

location of trees, light poles, and signs. 1. Reduce the maximum height ofparking lot light poles to the height trees are typically pruned forclearance. 2. Amend sign ordinances to allow monument signs (eye-levelsigns located near the street) and promote site designs that locatebusinesses closer to the street and move parking behind the buildings.

K Insure adequate species diversity.

K Develop a master tree list, omit species that are not suitable for parkinglots (e.g., pines, poplars, birch, etc.) and consider specifying recommend-ed tree spacing and minimum planting island widths for each species.

After InstallationPromote adequate tree care afterinstallation to increase tree vigor,

crown growth, and shade density.K Require that proper tree care

practices are used by qualifiedprofessionals.

K Remove stakes as soon as youngtrees can support themselves.

K Prune young trees early to traintheir growth.

K Allow tree crowns to reach theirfull potential.

K Make property owners, managersand arborists aware of shade

benefits as well as the benefits ofa commitment to professionalcare on a regular and long-termbasis.

K Enforce the ordinance to ensurethat trees are growing atacceptable rates, properly prunedand watered, and promptlyreplaced after removal.

K Replace removed trees with treesof equivalent size or value.

Strengthen OrdinancesK Link inspection fees to the

issuance of a building permit.

K Develop a monitoring andenforcement program thatrecords information on themanagement needs of everytree and results in a letter sentto the property managerrequesting corrective action in

a specified time.K Establish a mechanism to

collect fines or place a lien onthe property if the owner failsto make the requestedimprovements.

K Require interest-bearing bondsto pay for landscape improve-ments throughout the life ofthe project.

7/31/2019 Making Parking Lots More Tree Friendly: References - Fact sheet #3

2/2

Urban Forest Research January 2002

Center for Watershed Protection.1998. Better site design: a hand-

book for changing developmentrules in your community. Centerfor Watershed Protection. EllicottCity, MD. 174 p.

Girling, C.; Kellett, R.; Rochefort,J.; Roe, C. 2000. Greenneighborhoods: planning and

design guidelines for air, water,and urban forest quality. Centerfor Housing Innovation. University

of Oregon, Eugene. 132 p.

Grabosky, J.; Bassuk, N. 1996.Testing of structural urban treesoil materials for use under

pavement to increase street treerooting volumes. J. Arbor. 22: 255262.

For more information on parking lots, refer to the following publications written by

Center researchers and associates:

Visit ourwebsite athttp://cufr.ucdavis.edu

Increasing Effectiveness in Parking Lots

It is necessary to make key planning decisions prior to starting theretrofitting process. Some actions need to be taken and others avoided.Consider the following during the planning phase:

k Avoid double-counting tree shade where tree shade overlaps.

k Do not allow planting of trees not on the ordinances RecommendedTree List. Improve the Tree List if necessary.

k Be sure crown diameters on parking lot plans correctly reflect crowndiameters specified in the Tree List.

k Be sure crown diameters for mature trees are not overstated in theTree List, thus allowing parking lot plans to reflect more shade thanthey can actually achieve. Correct diameters in the List if necessary.

k Follow-up to ensure trees are actually planted, as well as notremoved shortly after planting, especially at sites near store frontswhere trees could obstruct signs.

k Do not allow smaller-sized substitutions after the plans have beenapproved.

k Do not allow parking lot ratios to exceed those stipulated in theordinance.

McPherson, E.G. 2001.Sacramento's parking lot shadingordinance: environmental and

economic costs of compliance.

Landscape and Urban Planning57:105123.

McPherson, E.G.; Simpson, J.R.;Scott, K.I. 2000.Actualizingmicroclimate and air quality

benefits with parking lot tree

shade ordinances.Wetter undLeben. 50: 353369.

Richman, T. 1997. Start at thesource: residential site planningand design guidance manual for

stormwater quality protection. BayArea Stormwater ManagementAgencies Association. Oakland, CA.75 p.

References: Making Parking Lots More Tree Friendly

This fact sheet is provided for you to copy and distribute. Please credit the Center for Urban Forest Research, Pacific Southwest ResearchStation, USDA Forest Service, Davis, California. January 2002.

Scott, K.I.; Simpson, J.R.;McPherson, E.G. 1999. Effects oftree cover on parking lotmicroclimate and vehicle

emissions. J. Arbor.25: 129141.Scott, K.I.; Simpson, J.R.;

McPherson, E.G. 1999. Greenparking lots: can trees improve air

quality? In McPherson, E.G.;Mathis, S., editors. Proceedings ofthe best of the west summit. CAES.University of California, Davis,Davis, CA; 8687.

Urban Land Institute. 1983. Sharedparking. Urban Land Institute,Washington, D.C. 86 p.