LID Best Management Practices Pilot Study

(Olympia, WA)  Landau Associates provided geotechnical engineering services to the City of Olympia for the Decatur Street SW Stormwater Low-Impact Development (LID) pilot study to evaluate the effectiveness of bioswales, porous pavement, and storm filters in reducing stormwater runoff. Prior to construction, we conducted a geotechnical investigation of near-surface soil and groundwater conditions on Decatur Street between 9th Avenue SW and 13th Avenue SW. Grain size testing was performed on representative soil samples obtained from borings and analyzed to determine long-term infiltration rates and support the design and in accordance with the City of Olympia’s Stormwater Manual. In addition, the strength of the subgrade soils was determined to aid in the City’s structural pavement design.

Sampling and evaluation of stormwater from the three best management practices (BMP) treatment systems over eight storm events indicated that catch basin filter cartridges performed best in removal of stormwater contaminants.