The Parking Forest is an assembly of materials to incorporate trees and stormwater management into parking lots without losing parking spaces. This presentation, which is an overview of stormwater and water quality, was presented by Brian Wegener of the Tualatin Riverkeepers and is posted with his permission.
17. New MS4 Permit Requirements
1) Incorporate sitespecific management
practices to mimic
natural surface or
predevelopment
hydrologic functions as
much as practicable.
The site-specific
management practices
should optimize on-site
retention based on the
site conditions;
18. New MS4 Permit Requirements
2) Reduce site specific postdevelopment stormwater
runoff volume, duration and
rates of discharges to the
municipal separate storm
sewer system (MS4) to
minimize hydrological and
water quality impacts from
impervious surfaces;
19. New MS4 Permit Requirements
3) Prioritize and include
implementation of LowImpact Development (LID),
Green Infrastructure (GI) or
equivalent planning, design
and construction
approaches;
20. Can we use
trees in parking
lots for
stormwater
runoff
reduction?
25. Challenges of Putting Trees in Parking Lots
Sacramento
Adopted in 1983,
Sacramento’s parking
lot ordinance requires
50 percent shading
within 15 years of
development.
Fifteen years after
development average
parking lot shade was
22%, not 50% as
stipulated by
ordinance.
27. Which trees are best for
stormwater management?
Deciduous?
Coniferous?
Broadleaf Evergreen?
28. Average Monthly Precipitation Downtown Portland
8
7
6
Inches
5
4
3
2
1
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Month
Aug
Sep
Oct
Nov
Dec
29. Rain Throughfall of European
Beech in Italy
Source: ALDO PAVARI, Director, Forest Experiment Station, Florence, Italy
30. Rainfall interception by Santa Monica’s
municipal urban forest
Xiao & McPherson – UC Davis
Tree Species
Season
Range of
% Rain
Interception
Camphor
Summer
Winter
28.4%-68.4%
19.3%-58.3%
Summer
Winter
42.5%-70.5%
5.4%-5.5%
(Broadleaf
Evergreen)
Sweetgum
(Deciduous)
33. Brian Wegener
503.218.2580
brian@tualatinriverkeepers.org
"This Project has been funded wholly or in part by the United States
Environmental Protection Agency under a federal grant issued under
Section 319(h) of the Clean Water Act. The contents of this document
do not necessarily reflect the views and policies of the Environmental
Protection Agency, nor does mention of trade names or commercial
products constitute endorsement or recommendation for use."
35. Sunset Swim Center Parking Lot Construction Expenses
Item
Porous Concrete
Cost
$200,000
Drain Rock
$62,000
Excavation
$35,000
Mobilization
$30,000
Curbs/Sidewalk
$26,000
Landscaping
$23,500
Soil/Structural Soil/Installation
$18,000
Demolition/Removal
$11,000
Striping/Wheel Stops/Signs
$10,000
French Drain / Drain Pipe
$3,000
12 Trees for Linear Well
$1,600
Other Stuff
$8,500
TOTAL CONSTRUCTION
$427,600
Notes de l'éditeur
In the urban part of the Tualatin basin we have a separate storm sewer system (unlike muck of Portland). Runoff from streets and parking lots in most cases goes directly to the nearest creek.
Sediments containing legacy pollutants are re-suspended in the rapid rise of an urban creek.
Trees intercept rain and send it back into the air. Tree roots can help water infiltrate. Fallen leaves can build an organic layer that acts like a sponge.
New regulatory requirements from DEQ are pushing changes in stormwater management, with a new emphasis on hydrology as well as chemistry.
Here is another way to build a parking lot (or parking forest) that uses trees to intercept rain before it becomes runoff. This site is at WalMart in Hilton Head South Carolina.
Compacted soil makes it hard for roots to penetrate.
Sacramento had some challenges in implementing tree canopy goals for parking lots through ordinance. Note that some of the parking lots did achieve their 50% canopy goal.
We get the largest portion of our rain when the deciduous trees have dropped their leaves.
At Sunset Swim Center we planted deciduous trees, Because of the porous concrete parking lot rainfall interception is less critical.
At our smaller demonstration project at PCC Sylvania, where there is no pervious pavement we planted native Douglas fir to maximize rainfall interception.