Business Park UIC Evaluation and Pervious Pavement Design

(Lake Oswego, OR)  Landau Associates assisted a commercial property owner in evaluating the effectiveness of existing Underground Injection Control (UIC) drywell systems to treat stormwater from over an acre of paved surfaces at its two-acre business park in Lake Oswego, Oregon. The Oregon Department of Environmental Quality (DEQ), which regulates UIC permitting, construction, operation, and maintenance to ensure the protection of groundwater in accordance with Oregon Administrative Rule (OAR) 340-040, had requested an assessment of the business park UICs’ impacts to shallow groundwater.

Though the UICs had operated for more than 20 years, the results of our investigation of sediment and groundwater in and around the business park UICs indicated that stormwater had not adversely impacted shallow groundwater. However, through consultation with DEQ, it was determined that the UICs did not meet the regulatory requirements pertaining to setback and would need to be removed. We evaluated several alternatives for stormwater management and treatment for the site and provided a preliminary cost analysis of each alternative. Alternatives evaluated included surface infiltration, a low-impact development (LID) technique that utilizes stormwater management features such as bioretention swales; connection to the city storm sewer system (which would require treatment of stormwater to meet total maximum daily loads for the Tualatin River prior to discharge); and pervious pavement. Pervious pavement was selected as the preferred alternative due to its long-term cost and maintenance considerations.

Landau Associates designed the pervious pavement, and performed in situ percolation tests to confirm design parameters.