12/9/2004; Parks Eastside Field Office 1 Aerial view of th e 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 86 th 

### Street at Foster Road

Project Summary

Overview of the Stormwater System

• Runoff from the 4,200 sq. ft. wa rehouse roof discharges to a landscape infiltration basin on the west side of the property.

• Runoff from 2,000 sq. ft. of park ing 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 implemente d the Willamette Stormwater Control Program in 2001. The Program offered financial grants and technical support for a seri es of projects to retrofit ex isting commercial properties with stormwater controls incorporating green technologies. The Program recruited these demonstration projects in order to research the feasibility, cost and performance of co mmercial stormwater retrofits in the ar ea served by the combined sewer. The Program provided grant funds for a to tal of eleven projects. The projects were completed by July 1, 2003. Project Type: Commercial/residential stormwater retrofit - demonstration project
Technologies: Landscape swales, landscape inf iltration 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 correspondin g 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 Program 1

. Constructed: Summer 200212/9/2004; Parks Eastside Field Office 2 

### Stormwater Capacity a nd System Components

Stormwater Management Goal The stormwater management goal was to meet the Bureau of Development Services (BDS) 2 standards for stormwat er 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 standard s 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 Re sources Conservation Serv ice (NRCS) soil survey for Multnomah County classifies the soils as 50A - Urban Land/ Multnomah Complex. The survey indicat es 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 footprint 3 : 630 sq. ft. Internal Volume : 850 cu. ft. Overflow : The facility does not have a pi ped overflow; it will fill to a depth of approximately 3 ft. before overflowing to a gravel area in the southwest corner of the property (f ormerly the site of the demolished garage). Capacity : The facility is larger and pr ovides substantially more capacity than the eastside soakage trench 4 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 th e west side of the property. A 5- ft. buffer separates the facility from the property line

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2 BDS is responsible for developing standards for stormwater disp osal and inspecting projects to confirm compliance with those s tandards.

3 For the purpose of comparing the capacity of the facility with the standard eastside soakage trench, the footprint has been ca lculated as the wetted (ponded) surface area when the facility reaches ma ximum capacity.

4 The standard eastside soakage trench meets the City’s standard for complete stormwater disposal in soils, which infiltrate at l east 2 in. per hour. The City requires 24 ft. of trench per 1000 sq. ft. of imperv ious area (drainage catchment) . The trench is 3 ft. deep, 2. 5 ft. wide, and filled with drainage rock. Flow enters the trench through a pervio us pipe that travels the length of the top of the trench. Ass uming a porosity of 35%, the trench provides an internal volume of a pproximately 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; 200212/9/2004; Parks Eastside Field Office 3 Shallow Landscape Infiltration Basins

• There are 4 shallow landscape de pressions 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 sout h wall of the building and down the exterior, discharging to th e landscape infiltration basin.

Office Downspout Disconnections

• Three simple downspout disconne ctions drain 1,500 sq. ft. of office roof.

• Simple residential-type drain ro ck 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 exis ting 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 an d 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 c ooling 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 la rge infiltration basin, standard turf sod was installed on the floor of the facility as a substrate for seeding wetland plants. A herbic ide, 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; 200212/9/2004; 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 pa rking lot. The area has not functioned as designed: runoff from th e 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. Becaus e 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 species12/9/2004; Parks Eastside Field Office 5 

### Budget

Portland Parks and Recreation (PP&R) submitted a to tal 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 fo r 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
S ubtota l 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 Summary12/9/2004; 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, construc tion, 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. Thework 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, im ported 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 si ngle cost, comprising almost 40% of the budget.

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

• The unit cost to install 2,500 sq. ft. of aspha lt 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 mi nimum diameters of 1.5 in. to 3 in.).

• One-third of the new landscape was not asso ciated with the stormwater facilities. Disconnected downspout on the front of the office building; spring

2004

Wildflowers in bloom; 200412/9/2004; Parks Eastside Field Office 7 • Over 75 cu. yds. of clean topsoil wa s 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 suppl emental irrigation, and provide habitat for a variety of insects in cluding pollinators. PP&R installed plugs of three native perennial bu nchgrasses as well as seeds and plugs of 14 species of native wildfl owers. Plugs are typically more expensive and require more labor to plant than seeds, but they tend to have a higher success rate th an 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 engine ering services were not required. The project did not include structural elements; it wa s 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 re quired 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 retrof it project. While adequate space existed for landscape infiltration areas, creating the areas and delivering runoff to them require d some substantial modifications. The most significant changes were re-g rading 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 st aff. 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 di sconnections to landscape infiltration areas – was inexpensive when compared to other project components.



### Maintenance and Monitoring

PP&R is responsible for the facility and its maintenan ce. Environmental Services and PP&R will monitor the performance of the facilit ies at the PP&R field offi ce for at least five years. Confirming the hydraulic performance of the facility will be a primary focus. E nvironmental 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 depression s) and more complex co mponents (re-plumbing of roof drains, asphalt re-contouring). The components cl early demonstrate to both the residential homeowner and commercial property owner the di fferent ways a site may be assesse d 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 oversi ght during installation of the aspha lt. His chief concern was producing the relatively subtle slope needed to convey runoff in to 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-fl ow 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 f acilities 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 Downs p out

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