12/9/2004; Parks Eastside Field Office 1

Aerial view of the PP&R field office, 

2002, prior to project construction. 

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Portland Parks & Recreation (PP&R) 

Natural Resource Program 

Eastside Field Office 

5701 SE 86th Street at Foster Road

Project Summary 

Overview of the Stormwater System 

• Runoff from the 4,200 sq. ft. warehouse roof discharges to 

a landscape infiltration basin on the west side of the 

property. 

• Runoff from 2,000 sq. ft. of parking area (and brick patio) 

also drains to the landscape infiltration basin on the west 

side of the property. 

• Three downspouts drain runoff from the 1,015 sq. ft. 

residential office roof to shallow landscape basins. There 

are two basins in front of the building and one in the back. 

• Runoff from 1,000 sq. ft. of re-graded asphalt on the east 

side of the property drains to shallow landscape basins at 

the front of the office and warehouse. 

• Almost 6,000 sq. ft. of asphalt was replaced with pervious 

surface areas (landscape and gravel). 

 

1

 Portland’s Bureau of Environmental Services implemented the Willamette Stormwater Control Program in 2001. The 

Program offered financial grants and technical support for a series of projects to retrofit existing commercial properties with

stormwater controls incorporating green technologies. The Program recruited these demonstration projects in order to research 

the feasibility, cost and performance of commercial stormwater retrofits in the area served by the combined sewer. The 

Program provided grant funds for a total of eleven projects. The projects were completed by July 1, 2003. 

Project Type: Commercial/residential stormwater retrofit - demonstration project 

Technologies: Landscape swales, landscape infiltration basin, vegetated filter, and downspout disconnections 

Major Benefits: • Runoff from 14,000 sq. ft. of impervious roof and parking lot surface has been removed from 

the combined sewer. 

• The stormwater facilities remove more than 314,000 gallons of runoff from the sewer in a 

typical rain year, with corresponding reductions in runoff pollutants. 

• More than 6,200 sq. ft. of native landscaping was added, improving the urban environment and 

the aesthetic appeal of the property. 

Cost: $55,183 (unit cost of $ 3.94 per sq. ft. of impervious area managed). Environmental Services 

granted $30,000 for the project through the Willamette Stormwater Control Program1. 

Constructed: Summer 2002 
12/9/2004; Parks Eastside Field Office 2

Stormwater Capacity and System Components 

Stormwater Management Goal

The stormwater management goal was to meet the Bureau of 

Development Services (BDS)2 standards for stormwater disposal. In 2002 

the disposal standard was to infiltrate at least 3 in. of runoff in 24 hours 

(the size of the 10 year design storm). All design standards cited in this 

report were current in 2002. 

Geotechnical Evaluation/Infiltration Test

City staff did not require site-specific infiltration tests - local drainage 

characteristics had been adequately documented by other projects in the 

vicinity. The Natural Resources Conservation Service (NRCS) soil survey 

for Multnomah County classifies the soils as 50A - Urban Land/ 

Multnomah Complex. The survey indicates the soils typically have been 

disturbed and mixed with fill material. The predicted infiltration range is 

0.6 – 2.0 in. per hour.

System Components

Landscaped Infiltration Basin 

(See Site Plan for details; Figure 1, pg. 9)

Catchment Area: 6,500 sq. ft. (warehouse roof and asphalt)

Facility footprint3

: 630 sq. ft.

Internal Volume: 850 cu. ft. 

Overflow: The facility does not have a piped overflow; it will fill to a 

depth of approximately 3 ft. before overflowing to a gravel area in the 

southwest corner of the property (formerly the site of the demolished 

garage). 

Capacity: The facility is larger and provides substantially more capacity 

than the eastside soakage trench4 required by the Stormwater 

Management Manual for a similar catchment (the soakage trench 

would have a footprint of 360 sq. ft. and a volume of 378 cu. ft.).

Additional Information: 

• The basin is 45 ft. long, 14 ft. wide, and 3 ft. deep. 

• It is located behind the office along the west side of the property. A 5-

ft. buffer separates the facility from the property line. 

 

2

 BDS is responsible for developing standards for stormwater disposal and inspecting projects to confirm compliance with those standards. 3

 For the purpose of comparing the capacity of the facility with the standard eastside soakage trench, the footprint has been calculated as the 

wetted (ponded) surface area when the facility reaches maximum capacity. 4 The standard eastside soakage trench meets the City’s standard for complete stormwater disposal in soils, which infiltrate at least 2 in. per 

hour. The City requires 24 ft. of trench per 1000 sq. ft. of impervious area (drainage catchment). The trench is 3 ft. deep, 2.5 ft. wide, and 

filled with drainage rock. Flow enters the trench through a pervious pipe that travels the length of the top of the trench. Assuming a porosity 

of 35%, the trench provides an internal volume of approximately 63 cu. ft. per 1000 sq. ft. of catchment.

Street-front view of the Parks Eastside 

Field Office - just after planting; 2002

Prior to the project - view from the 

back of the property toward the 

entrance; warehouse is on left; 2002

Prior to the project - entrance view of 

the warehouse; 2002
12/9/2004; Parks Eastside Field Office 3

Shallow Landscape Infiltration Basins

• There are 4 shallow landscape depressions that capture and 

infiltrate runoff. They are typically 6 inches deep.

• The areas occupy a total of 1,500 sq. ft. of landscape. 

• The three shallow landscape areas along the east side of the 

property together manage runoff from 750 sq. ft. of office roof and 

approximately 1,000 sq. ft. of adjacent asphalt.

Warehouse Rain Drains 

• Fifty lineal ft. of ABS pipe (4 in. diameter) was installed along the 

ceiling of the warehouse. The new pipe collects runoff from the 

warehouse roof and conveys it to the south wall of the building.

• Runoff is piped through the south wall of the building and down 

the exterior, discharging to the landscape infiltration basin.

Office Downspout Disconnections 

• Three simple downspout disconnections drain 1,500 sq. ft. of 

office roof.

• Simple residential-type drain rock helps convey roof runoff to 3 

shallow landscape infiltration areas, one behind the office and 2 in 

front.

Removal and Replacement of Asphalt 

A contractor removed all of the existing asphalt (8,500 sq. ft.). Part of 

the asphalt was replaced – a total of 2,500 sq. ft. – and graded to direct 

runoff into the landscape infiltration areas.

General Landscaping

• The landscaping includes mostly native plants - trees, shrubs, 

grasses, and wildflowers selected for their tolerance to dry and 

moist soil conditions. 

• In some upland areas - outside the facilities in front of the office 

building - prairie grass plugs and seed were planted as an 

alternative to a standard lawn. 

• Trees and shrubs were placed in strategic locations to help reduce 

the seasonal heating and cooling needs for the building. 

• All of the soils in the landscaped areas were ripped to a depth of 2 

ft. using a standard soil tiller. 

• Over 75 cu. yd. of clean fill was imported to grade the landscape 

areas as basins. The imported soil consisted of a blend of 

composted (weed free) yard debris and soil. 

• Immediately after excavating the large infiltration basin, standard 

turf sod was installed on the floor of the facility as a substrate for 

seeding wetland plants. A herbicide, glyphosate, was applied to 

kill the grass before seeding. 

Prior to planting - landscape 

infiltration area on the NE corner of 

the property; 2002

Graded landscape infiltration basin - 

west side of property; 2002

Construction of lined swale draining 

runoff from warehouse downspout to 

infiltration basin; 2002

Preparing landscape in front of the 

offices for planting; 2002
12/9/2004; Parks Eastside Field Office 4

Vegetated Filter Strip 

The east side of the main landscape infiltration basin was designed as 

an evenly-sloped filter strip with the purpose of filtering and slowing 

runoff (as sheet flow) from the parking lot. The area has not 

functioned as designed: runoff from the parking lot concentrates into a 

couple of flow paths rather than spreading throughout the strip. 

Emergency Overflow 

There are no emergency overflow pipes. If the landscape facilities 

reach capacity, they will safely overflow into adjacent landscaped or 

paved areas. 

Irrigation 

Temporary soaker hoses will be used to irrigate the plants during the 

two-year establishment period. Because the landscape is comprised of 

native plant species adapted to regional climate conditions, 

supplemental summer irrigation will typically not be required after 

they are established. 

The landscape infiltration basin on 

the west side of the property just after 

planting; 2002

Another shot of the basin just after 

planting - note that the side of the 

basin next to the pavement was 

designed as a filter strip for pavement 

runoff

The basin after rain; 2003

The basin in October 2004; Lupin has 

become the dominant plant species
12/9/2004; Parks Eastside Field Office 5

Budget 

Portland Parks and Recreation (PP&R) submitted a total budget of $55,183 including management, design, and 

construction. The final budget is shown below. 

I. Budget Elements

Non-Construction Activities 

The cost for management, design, and permitting was $8,029, comprising or about 15% of the budget. PP&R 

staff provided 140 hours of unpaid volunteer services for design, project and construction management, as 

well as permit submittals. 

• Management and Design 

Management (for the overall project as well as construction) and design was $6,951, comprising 12% 

of the budget. 

 Item Item Cost 

Volunteer 

Effort Total Cost 

Project Design, Project Management & Construction 

Management (unpaid labor) $6,951.00 $6,951.00

 Demolition, excavation, grading: $ 13,800.00

 Remove asphalt & partially remove sub-base (8,300 sq.ft.) 13,000.00 $ 

Excavate stormwater management facilities 600.00 $ 

Demolish structure (500 sq.ft.) 200.00 $ 

 Construction $ 11,842.83

 Asphalt re-surface [2,500 sq.ft.] 7,912.00 $ 

Re-plumb warehouse roof drains 3,000.00 $ 

Modify office downspouts (downspout disconnect) 642.40 $ 

Misc.hardscaping (lumber, pavers, etc.) 288.43 $ 

 Landscaping (6,200 s.f.) : 21,510.95 $ 

Plant material (trees, shrubs, seed, groundcover) 4,823.00 $ 

 1 cu. yd. 1/4 in. minus gravel & bark mulch 34.50 $ 

Misc. planting material (sod, fabric, etc.) 157.35 $ 

Drain rock (downspout disconnect) 54.20 $ 

 10 cubic units (75 cu. yds.) Compost/soil blend 1,352.25 $ 

Erosion control (straw, plastic, etc) 550.00 $ 

 Irrigation (hose bibs & soaker hoses) 1,132.41 $ 

Subtotal $ 8,103.71

Unpaid Volunteer Labor

 Installation - volunteers ($10/ hr) 1,206.00 $ 

Installation - PP&R staff ($49/hr) $10,995.24

Subtotal $ 12,201.24

 Permitting: 

 Permit - Planning/Zoning/Landuse 1,077.84 $ $ 1,077.84

TOTAL 34,824.38 $ 19,152.24 $ $55,182.62

Portland Parks and Recreation Budget Summary 
12/9/2004; Parks Eastside Field Office 6

• Permitting 

The Site Development Permit cost $1,077, comprising 2% of 

the total budget. The staff cost for coordinating the submittal 

and resolving permitting issues is included in the management 

costs. 

Construction Activities 

Demolition, excavation, construction, and landscaping costs were 

$47,154, comprising 85 % of the budget. 

• Demolition, Excavation, and Grading 

The activities cost $13,800 (25% of the budget), including 

removal of 8,500 sq. ft. of asphalt. Also included was the 

removal and re-grading of the 6-in. sub grade. A licensed 

contractor removed the asphalt; Parks staff did all other 

demolition work, including removal of a 500 sq. ft. garage on 

the southwest corner of the property. 

• Construction 

Construction cost $11,843, comprising 21% of the budget. The 

work included disconnection of three office downspouts, replumbing the internal rain drains of the warehouse, installation 

of walkways (flagstone pavers and brick paths), and asphalt repaving. A contractor did the asphalt work. 

• Landscaping 

The project added 6,200 sq. ft. of new landscaping (about 40% 

of the surface area of the site). The cost for landscaping was 

$21,511, including plant material, imported clean soil, and over 

300 hours of volunteer labor valued at $13,407. The average 

unit cost for landscaping was $3.59 per sq. ft. including the 

volunteer labor and temporary irrigation materials. 

II. Cost Components

Pavement

• Asphalt removal and re-grading was the largest single cost, comprising almost 40% of the budget.

• The unit cost of removing and exporting asphalt was $1.50 per sq. ft., including removal and some regrading of the 6 in. gravel sub-base. 

• The unit cost to install 2,500 sq. ft. of asphalt was $3.16 per sq. ft. (not including sub grade)

Landscaping

• Many trees were larger than required by the City (in 2002 the City required minimum diameters of 1.5 

in. to 3 in.). 

• One-third of the new landscape was not associated with the stormwater facilities. 

Disconnected downspout on the 

front of the office building; spring 

2004 

Wildflowers in bloom; 2004 
12/9/2004; Parks Eastside Field Office 7

• Over 75 cu. yds. of clean topsoil was imported to re-grade the site. 

The clean soil was more costly than recycled topsoil, but the 

designer specified it to help minimize the introduction of undesirable 

invasive weed species. 

• Native grasslands were selected for the upland areas because they 

are deep rooted, require no supplemental irrigation, and provide 

habitat for a variety of insects including pollinators. PP&R installed 

plugs of three native perennial bunchgrasses as well as seeds and 

plugs of 14 species of native wildflowers. Plugs are typically more 

expensive and require more labor to plant than seeds, but they tend 

to have a higher success rate than many seeds and produce a high 

quality cover of diverse species. 

• Although installation costs were relatively high, the planting 

approach for the upland areas should require less maintenance and 

watering than other landscapes, and be aesthetically pleasing quickly. 

Design

Design costs were relatively low in part because engineering services were not required. The project did not 

include structural elements; it was designed by a PP&R staff person with a landscaping contractors license. 

Plumbing

There were few plumbing modifications with the exception of re-directing the warehouse roof drains to the 

landscape infiltration basin. No overflow pipes were required for the basin system: it is large enough to 

capture and infiltrate all of the runoff from the warehouse roof and the adjacent parking lot. 

III. Cost Comparisons

This project is an example of a fairly complex retrofit project. While adequate space existed for landscape 

infiltration areas, creating the areas and delivering runoff to them required some substantial modifications. 

The most significant changes were re-grading and removing existing pavement. 

Similar private sector projects might cost less. Although a private contractor installed the new pavement, all 

other construction and planting was performed by City staff. The staff provided much of their work free of 

charge, but the project budget includes their effort at almost $50 per hour (their normal billable rate). The 

residential portion of the work – simple downspout disconnections to landscape infiltration areas – was 

inexpensive when compared to other project components. 

Maintenance and Monitoring 

PP&R is responsible for the facility and its maintenance. Environmental Services and PP&R will monitor the 

performance of the facilities at the PP&R field office for at least five years. Confirming the hydraulic 

performance of the facility will be a primary focus. Environmental Services will also regularly evaluate the 

effort required to maintain the facility and the success of the planting regime. 

Recently planted landscape 

infiltration area in front of the office 

building - note flow path on asphalt 

driveway.
12/9/2004; Parks Eastside Field Office 8

Successes and Lessons Learned

Design - This project is a good example of a site retrofit with a mix of simple components (downspout 

disconnections, excavated shallow landscape depressions) and more complex components (re-plumbing of 

roof drains, asphalt re-contouring). The components clearly demonstrate to both the residential homeowner 

and commercial property owner the different ways a site may be assessed and retrofitted for stormwater 

management. 

Oversight of Asphalt Work – The project manager suggested that the project might not have been successful 

had he not provided extensive oversight during installation of the asphalt. His chief concern was producing 

the relatively subtle slope needed to convey runoff into the landscape facilities. The success of similar 

projects is expected to require the same degree of oversight. 

Vegetated Filter Strip – The vegetated filter strip along the edge of the parking lot (west side of property) was 

designed to slow and filter sheet-flow entering the landscape infiltration basin from the adjacent parking lot. 

In practice the runoff concentrates into one or two flow paths; the result illustrates the challenges associated 

with achieving the grades required for filter strips in similar situations. 

Landscaping

In 2004 the PP&R staff observed that the landscape facilities are less frequently ponded with runoff – 

monitoring is needed to confirm if infiltration rates have improved. 
12/9/2004; Parks Eastside Field Office 9

BASIN 

Downspout

2,500 SQ. FT. 

ASPHALT 

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Figure 1. Site Plan of the Parks Field Office. 
12/9/2004; Parks Eastside Field Office 10