Client: Walgreens, Aloha, Oregon
An existing restaurant was to be removed and the parking lot expanded to serve Walgreens. New stormwater treatment requirements would have required the entire site to be retrofitted to meet current storm water treatment requirements even though the finished parking lot would reduce impervious areas contributed to storm water runoff. Site topography, existing drainage facilities and soil conditions severely limited treatment options available.
CESNW worked Clean Water Services staff to develop an approach utilizing Low Impact Development (LID) approach to construct the proposed parking lot with pervious pavement yet allow for potential overflows due to poor soil infiltration rates. The critical storm water design event would be stored and percolated into the existing soils yet allowing larger events to overflow into the existing drainage system if necessary.