FLOOD CONTROL, STORMWATER CAPTURE, AND GROUNDWATER RECHARGE: THE RORY M. SHAW WETLANDS PARK PROJECT

The Rory M. Shaw Wetlands Park Project, in the City and County of Los Angeles, consists of three major elements: 1) 4.2 miles of storm drain trunk line within an industrial area; 2) a 21-acre detention pond, 10 acres of wetlands, and 15 acres of recreational facilities and open space within the area of a Class 4 inert debris landfill and former concrete plant; and 3) recharge of the San Fernando Valley aquifer through underground infiltration galleries beneath ball fields in Sun Valley Park. The 48-inch to 96-inch main storm drain will direct water from 140 catch basins over a drainage area of 929 acres into the detention pond. The drain will be constructed in an open trench along four major streets, as well as tunneling 160 linear feet under the active Metrolink Rail line. This drain will alleviate street flooding in Sun Valley which lacks a master flood control system.

Strathern Pit was mined for sand and gravel from 1926 to 1972. The 160-foot-deep gravel pit was approved as a 30-acre inert landfill in 1991and filled until 2008. Strathern Pit and the concrete plant were obtained by the Los Angeles County Flood Control District in 2010 and renamed Rory M. Shaw Wetlands Park. The former concrete plant is partially underlain by municipal waste of the Newberry landfill.

Mitigation of settlement in the upper 20 to 60 feet of the wetlands park will include a combination of debris removal, crushing, and placement as an engineered fill, dynamic compaction, and compaction grouting, followed by placement of liners.

The proposed wetlands will remove metals from the water prior to pumping uphill to the adjacent Sun Valley Park where infiltration galleries were constructed in 2006. Depth to the aquifer is approximately 300 feet. The water conservation benefit is expected to be 590 acre-feet per year.

The project will be constructed within the recent flood plain deposits of the Tujunga Wash which emanates from the San Gabriel Mountains some 4 miles to the north. Project constraints include large boulders, caving ground, methane gas, settlement of landfill materials, and lead contamination.

The opinions expressed are solely those of the authors, and do not represent the opinions of, nor endorsement by, the LACDPW.