Reducing Stormwater Runoff Impacts

U-Tech: Underground Technology Cutting Edge Technical Information for Utility Construction and Rehabilitation
By Aaron Eder, P.E., Kennedy/Jenks Consultants | May 2010 Vol. 65 No. 5

Powell Butte is a 578-acre nature park of vast meadowlands and forests, located in southeast Portland, OR, within easy reach of city dwellers. The park is bounded roughly by SE Powell Blvd. to the north, SE 141st Ave. on the west, SE 162nd Ave. on the east, and the Springwater Trail Corridor on the south (Figure 1). The butte, an extinct cinder cone volcano, rises near the headwaters of Johnson Creek – an urban creek with remnant populations of native salmon and steelhead. It is Portland's second-largest park.

In the late 1800s, the large meadow area was cleared and an orchard planted. In 1925, the city of Portland purchased the land for future water reservoirs, but continued to lease the northeast portion of the property to Henry Anderegg, a farmer and owner of Meadowland Crest Dairy, until 1948 when the farming was discontinued. However, dairy cattle were permitted to graze on the acreage to preserve the pastures.

In the mid-1970s the Portland Water Bureau (PWB) prepared a development plan for Powell Butte that called for the construction of four, 50-million gallon underground reservoirs to be located at the north end of the butte. In 1981, the first, and currently only, 50-million gallon reservoir was built and still serves as one of the hubs of PWB’s distribution system. Also, the Powell Valley Water District had three reservoirs on the butte prior to its acquisition by PWB in 2005. In 1987, the city officially established Powell Butte as a nature park and it was opened to the public in 1990.

Since the early 1990’s, Powell Butte has been co-managed by both PWB and Portland Parks and Recreation (PPR). PWB owns the Butte and manages water facilities, and PPR manages the security, nature, and recreation functions.

Existing conditions
Despite all it has to offer as a nature park, a large portion of the northeast quadrant of the butte slopes toward Meadowland Mobile Home Park (MMHP), a community of approximately 200 residents. Since it was developed in 1988, MMHP has historically experienced flooding and saturated ground conditions each winter during severe storm events (Figure 2). The relatively impermeable soils and high local groundwater conditions exacerbate the problem.

Figure 2