12/9/2004; ONRC 1

The property in 2002 before 

the project 

Oregon Natural Resources Council 

5825 N. Greeley Avenue, Portland

Project Summary 

Project Type: Commercial stormwater retrofit – demonstration project 

Technologies: Porous paver system; landscape infiltration basin; simple downspout disconnections (to splash blocks). 

Major 

Benefits: 

• Runoff from more than 13,000 sq. ft. of impervious surface (roof and pavement) has been removed 

from the combined sewer. 

• The stormwater facilities remove more than 300,000 gallons of runoff from the sewer in a typical 

rain year, with corresponding reductions in runoff pollutants. 

• The project added 4,700 sq. ft. of native landscaping, improving the aesthetic appeal of the property 

and benefiting the urban environment. 

Cost: $82,946 (unit cost of $6.00 per sq. ft. of impervious area managed). The total cost includes some 

components that were not essential to the stormwater management goals (e.g. a rain harvesting system 

and a bridge). Environmental Services provided a $30,000 grant. 

Constructed: Fall 2002 

Project Background 

The Oregon Natural Resources Council (ONRC), a non-profit 

conservation organization, moved to the site in 1996. ONRC was 

planning a comprehensive site renovation project in 2001 when it 

received information about the Willamette Stormwater Control 

Program1

. ONRC then contracted with a landscape architect to 

develop a proposal to completely disconnect the site from the 

combined sewer system, managing the stormwater entirely onsite. Environmental Services accepted the project into the Program 

in 2001. 

ONRC viewed the project as an opportunity to enhance the site 

renovation project to better exemplify the sustainability goals of 

its mission. It wanted to provide an example of the environmental 

benefits associated with on-site stormwater management, and save 

money on its stormwater utility bill. 

 

1

 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 eleven projects. The projects were completed by July 1, 2003. 
12/9/2004; ONRC 2

Project Scope 

• Removed all existing asphalt (approximately 9,100 sq. ft.) 

• Installed a pervious paver system (5,500 sq. ft. of pavers for the 

parking lot; 250 sq. ft. for the patio). 

• Installed a 1,700 gallon rain harvesting system to provide irrigation 

water. 

• Constructed a landscape infiltration basin to manage roof runoff 

and any overflow from the paver system. 

• Planted almost 5,000 sq. ft. of landscape with native vegetation. 

• Re-routed all roof runoff to landscape areas. 

• Installed a small bridge and a gravel path. 

Notable Features 

• The entire site has been completely disconnected from the 

combined sewer system. 

• The project includes two relatively new technologies - a rain 

harvesting system and pervious paver system. 

• Retrofitting the parking lot resulted in the loss of four non-essential 

parking spaces. 

• The large infiltration basin is integral to the landscaping at the 

building entrance. 

Project Design 

ONRC contracted with the Lando and Associates, Landscape 

Architecture Inc. to design the project. The stormwater management 

goal was to provide complete on-site disposal of all stormwater runoff. 

Overview of the Stormwater System

• Approximately 1,200 sq. ft. of the roof on the south side of the 

building drains to adjacent landscaped areas via splash blocks. 

• About 3,200 sq. ft. of roof drains to the cistern buried at the west 

end of the landscape infiltration basin. 

• The cistern overflows to the adjacent landscape infiltration basin. 

• The pervious pavers infiltrate all rainfall that lands on the 5,500 sq. 

ft. parking lot. If the paver system ever reaches capacity, it would 

overflow to the landscape infiltration basin. 

The new sign with the 

infiltration basin in the 

background; September 2003

View from the NW corner of 

the property - note landscape 

infiltration basin behind wheel 

stops; February 2003

The walkway and the landscape 

infiltration basin; June 2004
12/9/2004; ONRC 3

I. Introduction

The overall stormwater management goal was to meet the Bureau of 

Development Services (BDS)2

 standards for stormwater disposal. When 

BDS approved the project in 2002, the disposal standard was to infiltrate 

at least 3 inches of runoff in 24 hours (approximately the size of the 10 

year design storm). All standards cited in this report were current in 2002. 

City permit staff did not require site-specific infiltration tests as local 

drainage characteristics had already been adequately documented by other 

projects in the vicinity. The Natural Resources Conservation Service 

(NRCS) Soil Survey for Multnomah County classifies the soils as part of 

the Latourell Complex. The Survey gives an estimated infiltration range of 

0.6 – 2.0 in. per hour. 

II. Facility Components

(See Site Plan, pg. 6, for more details) 

Rain Harvesting System 

Catchment Area: 3,200 sq. ft. of roof 

Internal Volume (empty): 1,700 gallons (227 cu. ft.) 

Overflow: Drains to landscape infiltration basin. 

Capacity: A little under an inch of rain (.85 in.) will fill the cistern. The 

cistern provides stormwater capacity during the drier months when the 

stored runoff is used to supplement irrigation needs. If plans are 

realized to reuse stormwater for toilet flushing, the cistern will provide 

additional runoff capacity even during the months when no irrigation 

is required. 

Additional Information: 

• The cistern is buried at the west end of the landscape infiltration 

basin. 

• The cistern water is distributed for irrigation via a pump after 

passing through two sediment filters. 

 

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

Detail of the pavers during 

construction; October 2002

Installation of the pavers - 

looking south toward the ONRC 

office

Excavation of the landscape 

infiltration basin - note workers 

applying gravel to paver spaces

Excavation of the landscape 

infiltration basin
12/9/2004; ONRC 4

Landscape Infiltration Basin 

Catchment: 3,200 sq. ft. of roof (runoff enters via the cistern) 

Facility footprint3: 520 sq. ft. 

Internal volume: 660 cu. ft. (includes sub-surface gravel trench) 

Overflow: If the basin ever crests in a large storm, it will spill north 

across the parking lot, away from the building foundation, and fill the 

sub-base of the paver system before flowing across the surface to the 

public right-of-way. 

Capacity: The basin has a capacity much larger than the comparable 

standard eastside soakage trench4

 that would be required for a similar 

catchment. The soakage trench would have a footprint of 192 sq. ft. 

and an internal volume of 200 cu. ft. 

Additional Information: 

• The basin is linear and deep: in the main body of the facility the 

centerline is about 3 ft. below grade. 

• A narrow gravel trench lies under the east part of the facility. It is 

20 ft. long, has a cross section of 12 in. by 12 in., and is buried 

about a foot below the floor of the basin. Neither perforated 

piping nor filter fabric was used in its construction. 

Porous Paver System (Parking Lot) 

Catchment: 5,500 sq. ft. (as direct rainfall) 

Facility footprint: 5,500 sq. ft. 

Internal volume: 1,650 cu. ft. (as pore space in the gravel sub-grade). 

Overflow: The bottom of the gravel layer under the pavers slopes gently 

toward the adjacent landscape infiltration basin. While the paver 

system has an enormous capacity for runoff, overflows to the 

basin are possible. 

Capacity: The system has an extremely large internal volume compared 

to the standard eastside soakage trench4

 that would be required 

for a catchment of 5,500 sq. ft. (the soakage trench would have a 

footprint of 330 sq. ft. and an internal volume of 345 cu. ft.). 

Additional Information:

• The pavers are 8 in. square and 3 in. thick. 

• They are constructed of concrete and recycled fly ash. 

• They are set in one inch of pea gravel with an 8-inch sub-base 

of crushed rock. 

• They were supplied by SF-Rima TM (by WestCon). 

• The parking lot is pitched slightly toward the infiltration 

basis, so if rainfall exceeds the infiltration rate, it will seep 

into the basin.

 

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 inches 

per hour. The City requires 24 feet 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 1,000 sq. ft. of catchment.

The landscape infiltration basin 

with final grading; October 2002

Arrival of the cistern

Installation of the cistern; 

October 2002
12/9/2004; ONRC 5

Downspout Disconnections 

There are nine downspouts on the building. Six of the downspouts drain 

approximately 3,200 sq. ft. of roof, sending runoff to the cistern. Three 

downspouts on the south side of the building have been disconnected to 

splash blocks, draining to the adjacent landscape. 

 

Emergency Overflow 

If the basin ever crests in a large storm, it will spill north across the 

parking lot, away from the building foundation, and fill the sub-base of the 

paver system prior to flowing across the surface to the public right-of-way. 

Landscaping 

Most of the plants are natives selected from the plant list in the 

Environmental Services Stormwater Management Manual. The plantings 

meet manual requirements for size and spacing. The designer selected 

species such as Red Osier Dogwood that grow relatively tall and respond 

well to pruning. 

Irrigation 

The project included installation of a new permanent irrigation system 

with pop-up spray heads. It serves a total of 4,700 sq. ft. of landscape with 

water supplied by the cistern as well as City water (as needed). 

 

Other Components 

A gravel walkway provides handicap access to the front entrance as 

required by City code. The gravel walkway was easily integrated into the 

landscape and provides a pervious surface at a lower cost than pavers or 

other Americans With Disabilities Act (ADA)- approved material. The 

bridge over the north end of the landscape infiltration basin connects the 

parking lot with the primary building entrance. 

Installation of rain drains within 

two feet of fourndation; October

2002

Newly planted infiltration basin 

after rain; January 2003

Newly planted infiltration basin 

after rain; January 2003
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12/9/2004; ONRC 7

Budget 

ONRC provided the budget, which is detailed on the following page. The total cost for the project was 

$82,946 including management, design, and construction. 

BES contributed $30,000 in grant funds to the project. Bureau costs for administering the grant program 

and providing limited technical support are not included in the budget. 

Parking Lot Paver System – 5,500 Sq. Ft. Cost 

 Asphalt demolition, removal, export* $ 770.00 

 Excavation - parking lot subgrade $ 3,693.00 

 Sub-base - import and compact (8in.) $ 3,400.00 

 # Pavers - 9790 SF-RIMA pavers * $ 8,910.00 

 Installation - contractor labor $ 10,378.00 

 Installation - volunteers @ $10 per hour $ 936.00 

 Survey, setting bed $ 985.00 

 Erosion Control* $ 825.00 

 Wheel stops (7) $ 277.00 

 Paver protection - plywood rental $ 20.00 

 

 Total $ 30,194.00 

 Cost Per Sq. Ft. $ 5.49 

 

 * Calculated as a portion of a larger cost 

Costs For Parking Lot Paver System 
12/9/2004; ONRC 8

ONRC Budget Summary 

 Item Item Cost Total Cost In Kind Cost 

 Project Management $ 10,957.00 

 General management (ONRC) $ 9,367.00 

 Contract management (L.A.) $ 1,590.00 

 Design $ 2,359.00 

 Demolition, excavation, grading $ 13,441.00 

 Asphalt demo, removal, export (9100 sq. ft.) $ 1,325.00 

 Excavation - parking lot subgrade (6in. depth) $ 3,693.00 

 Excavation & grading - swale, patio, walk $ 3,140.00 

 Excavation - trenching for rain drains $ 693.00 

 Remove catch basin, cap line $ 250.00 

 Equipment rental $ 400.00 

 Excavation, etc. - cistern $ 1,720.00 

 Erosion control $ 1,365.00 

 Miscellaneous (waste export, recycling, etc.) $ 855.00 

 Construction Management $ 2,634.00 

 Construction: $ 31,568.00 

 Paver System & Patio - 5,750 sq. ft. 

 Sub-base - import and compact (8 in.) $ 3,400.00 

 Pavers - 10,240 sq. ft.-RimaTM pavers $ 9,357.00 

 Installation - contractor labor $ 10,378.00 

 Installation - volunteers $ 936.00 $ 936.00 

 Survey, setting bed $ 985.00 

 Wheel stops (7) $ 277.00 

 Paver protection - plywood rental $ 20.00 

 Subtotal $ 25,353.00 

 Bridge 

 Fittings for bridge & ramp $ 500.00 

 Plastic decking $ 1,072.00 

 Subtotal $ 1,572.00 

 Rain Water Harvesting System 

 Concrete Cistern $ 1,850.00 

 System Pump $ 1,086.00 

 Piping $ 976.00 

 Electrical irrigation controls $ 731.00 

 Subtotal $ 4,643.00 

 Landscaping (4,670 sq. ft.) $ 16,058.00 

 Installation - contract labor, mulch, etc. $ 3,280.00 

 Transplant existing plants $ 600.00 

 Installation - volunteer labor ($10/hr) $ 320.00 $ 320.00 

 Irrigation $ 5,891.00 

 Plant material $ 5,967.00 

 Miscellaneous: $ 5,929.00 

 Permitting 

 Coordination of submittal and appeal $ 2,865.00 

 Permit - Planning/Zoning/Land use $ 1,369.00 

 Permit – Environmental Services $ 787.00 

 Permit - Plumbing $ 423.00 

 Maintenance agreement $ 248.00 

 Subtotal $ 5,692.00 

 Other 

 Porta-potty rental $ 187.00 

 Handicap paint and signage $ 50.00 

 Subtotal $ 237.00 

 TOTAL $ 82,946.00 
12/9/2004; ONRC 9

I. Budget Elements

Non-construction Activities 

The total estimated cost for management, design, and permitting was $21,642, comprising approximately 

26% of the total budget. 

• Project and Construction Management 

The total for project and construction management was $13,591, comprising 16% of the total 

budget. Two ONRC staff managed the project, providing a total of 540 hours of effort over 18 

weeks. They managed the budget, worked as liaisons between the designer and subcontractors, 

and scheduled volunteer labor. Management also includes the landscape architect’s time for 

managing the contract and overseeing construction. 

• Design 

The landscape architect’s cost for designing the project was $2,359, comprising 3% of the total 

budget. 

• Permitting 

Permitting costs, including the labor costs to coordinate the original submittal and appeal, were 

$5,692, comprising almost 7% of the total budget. 

Construction Activities 

Demolition, excavation, construction, and landscaping costs totaled $61,304, comprising 67% of the total 

budget. The paver system for the parking lot is the largest single component, comprising 80% of total 

construction costs (see Table 2 at the end of this section). The rainwater harvesting system, including the 

cistern and related components, comprises 15% of the construction budget. 

• Demolition, Excavation, and Grading 

The site preparation activities, including removal of the existing asphalt (9,100 sq. ft.), cost 

$13,441, comprising 16% of the total budget. 

• Construction 

The core construction activities, including installation of the paver system, the rainwater 

harvesting system, and the bridge cost $31,568, comprising 38% of the total budget. 

• Landscaping 

The project included almost 5,000 sq. ft. of landscaping (about one-third of the total site). It 

cost $16,058, comprising 19% of the total budget. 

II. Cost Efficiencies 

Paver System 

The cost of the porous paver system was $5.49 per sq. ft., including demolition and recycling of the 

existing asphalt, excavation, and installation of an 8-in. sub-base of crushed rock. The unit cost for the 

paver system is likely lower than typical since ONRC purchased the pavers at a discounted rate. 
12/9/2004; ONRC 10

Plumbing 

Extensive sub-surface piping was needed to extend the building’s downspouts to the cistern. The parking 

lot retrofit required only the capping of the existing stormwater inlet. The landscape infiltration basin did 

not require any piping for overflow events. 

Landscaping 

Although the overall cost of landscaping was a significant budget component, the unit cost of purchasing 

and installing the plants was relatively low at $2.00 per sq. ft. The permanent irrigation system added 

substantially to the total landscaping budget, costing an additional $1.21 per sq. ft. 

Asphalt Removal 

The unit cost for removing and exporting 9,100 sq. ft. of asphalt was $0.15 per sq. ft. for a total cost of 

$1,325. That includes removal of the sub-grade, which was “almost non-existent” according to the 

landscape architect. 

III. Cost Comparisons 

This project is a good example of the type of intensive retrofit that a long-term property owner might 

undertake as part of a substantial renovation project. While part of the runoff is managed in a simple 

landscape system, the budget is dominated by the installation of the paver system. The stormwater 

harvesting system also makes this a more complex, costly retrofit. It is clear that for some property 

owners the many long-term benefits associated with these approaches outweigh their costs relative to 

simpler stormwater management approaches. 

Bidding and Permitting 

I. Bidding 

ONRC contracted directly with Lando and Associates, Landscape Architects Inc. for design and 

construction management for the project. Lando and Associates coordinated the work schedule and 

approved the completion of work for each sub-contractor. 

II. Permits 

Plumbing Permit 

A plumbing permit was required for the following: disconnecting the downspouts; installing the 

subsurface rainwater harvesting cistern; installing the backflow prevention and irrigation system; and 

removing and capping the stormwater inlet in the parking lot. 

Building Permit 

The City issued a commercial building permit for the project because it was part of a larger renovation 

project. The process included reviews for the adequacy of erosion control and grading plans, a review for 

compliance with the Environmental Services Stormwater Management Manual (for water quality and 

flow control requirements), and a review for the capacity of the system since the goal was to provide 

complete on-site disposal. 

Planning and Zoning Review 

Due to the cost of the renovation project, the City required ONRC to meet current parking lot standards 

for setbacks and landscaping. The project did not trigger other requirements related to conditional uses or 
12/9/2004; ONRC 11

overlay districts (such as trails, e-zones, plan districts, etc.). No reviews were required for transportation, 

pedestrian issues, or seismic issues. A review for ADA access was required. 

Appeals 

An appeal was required for the gravel path between the building and the infiltration basin. The City 

required a special review for the gravel walkways due to concerns about slope, gravel movement/failure 

and the safety of wheelchair access. The City also required an appeal for the commercial installation of a 

rain harvesting cistern. Note: rain washers (to treat the first flush of roof runoff) were not required 

because the cistern water will be used for landscaping. Rain washers will be required if the water is used 

for indoor applications. 

III. Permitting Issues

The City expressed initial concern about the lack of a piped emergency overflow for the landscape 

infiltration basin. ONRC then doubled the capacity of the basin and demonstrated that if it ever reaches 

capacity it will overflow to the pervious parking lot without threatening any structures. City inspectors 

confirmed that the paver system was installed consistent with the manufacturer’s guidelines – the City did 

not have standards for paver systems at the time of the project. 

 Construction 

I. Summary

ONRC contracted for the installation of the pavers in the parking lot and patio, although a volunteer labor 

force provided some assistance. Volunteers also helped with installation of the landscape. ONRC staff 

helped oversee the work and acted as a liaison to the designer. Construction began in September 2002 and 

was completed in December 2002. 

II. Issues

Paver protection - After the pavers were installed, the parking lot continued to serve as a staging area for 

other construction activities. To ensure the paver system was protected during construction, ONRC 

covered the pavers with plywood and tarps to prevent sedimentation and clogging. 

Rain harvesting system – The original plans specified a plastic cistern, however a decision was made in 

the field to replace it with a concrete cistern in order to accommodate discrepancies between survey 

information and actual field elevations. There were also concerns about the buoyancy of a plastic cistern 

and resistance to vehicle load (the cistern sits next to the parking lot). The concrete cistern required an 

additional 16 in. of depth to provide clearance for its overflow pipe. The difference resulted in a 

corresponding deepening of the landscape infiltration basin. 

 Maintenance and Monitoring 

ONRC owns the facility and is responsible for maintenance. BES will monitor the performance of the 

facilities at ONRC for five years or more. Confirming the hydraulic performance of the facility will be a 

primary focus. The Bureau will also regularly evaluate the level of effort required to maintain the facility, 

the success of the planting regime, and comments from the owner. ONRC staff has volunteered to gather 

information about how visitors are influenced by the project and how they incorporate similar techniques 

at their own sites. 
12/9/2004; ONRC 12

Successes and Lessons Learned

Good design – The landscape infiltration basin is an integral part of the surrounding near the building’s 

entrance. The project demonstrates that stormwater management features can be integrated into attractive 

landscape areas rather than being designed as “facilities” relegated to peripheral areas. 

Overall demonstration value – The project provides an example for others interested in similar projects. In 

addition to being an important educational tool that advances the City’s interests in sustainable site 

design, the project provides important lessons about the challenges of integrating new technologies given 

the existing City codes. 

Space-efficiency of the paver system – This project demonstrates the space-efficiency of pervious parking 

surfaces. They do not require additional adjacent areas for stormwater treatment and disposal. 

Pavers and clogging during construction – The project confirmed the paver systems may be vulnerable to 

clogging as a result of construction activities, and that protecting the pavers should be a priority for any 

paver installation project. 

Downspout rain drain pipes

A couple of the downspouts are more than 40 ft. from the rain harvesting system (cistern) to which their 

drainage is piped. The designer successfully kept the pipes at an acceptable elevation by positioning them 

within two feet of the foundation for most of the distance. At the time the project was implemented the 

City allowed stormwater pipes within two feet of a foundation at grades of less than 1%. 

Owner motivation – ONRC viewed the project as an opportunity to support its environmental mission, 

improve the neighborhood, and reduce its stormwater utility bill. 
12/9/2004; ONRC 13