Seattle-Tacoma International Airport (STIA) Infiltration Feasibility Assessment

To comply with its NPDES permit, the Port of Seattle is developing LID BMP guidelines for future development and redevelopment projects at STIA. In support, Aspect identified shallow and subsurface stormwater infiltration opportunities using existing GIS layers, geologic data, and other relevant data. Infiltration feasibility was based on evaluation of factors that affect infiltration potential and identification of units that represent unique combinations of these factors. The results were used to create infiltration feasibility maps for both the shallow and subsurface hydrostratigraphic units, and are now being incorporated into the Port’s Stormwater Management Manual for Aviation Division Property.

Aspect's Tom Atkins presented the STIA infiltration assessment project at the 2017 Municipal Stormwater Conference (MuniCon) Infiltration Workshop.

City of Moscow Stormwater Utility Study

Aspect is initiating the development of a stormwater utility for the City of Moscow, ID (City) to help the City develop, fund, and carry out a stormwater program that meets future NPDES Phase II requirements. Services for this phase include collecting data about the City’s existing stormwater system, CIP, and program activities; identifying future staffing and equipment needs; estimating future program costs and revenue needs; estimating preliminary utility rates; and guiding the City on stormwater utility legal issues, policies, and alternative rate structures. Aspect will also be coordinating with the University of Idaho on the proposed utility’s impacts. 

City of Bellingham Bioretention Hydrologic Performance Study

Aspect is examining the effectiveness of 10 bioretention facilities across the Puget Sound and North Sound through the combined analysis of continuous flow and rainfall data, vegetation, geotechnical, and modeling. Aspect designed and installed custom hydrologic monitoring stations to work with the unique inflow and outflow designs of each facility. We are maintaining the monitoring stations and managing and analyzing level, flow, groundwater, and rainfall data over a ten-month study period. Aspect will perform the analysis of the hydrologic mass balance data set and work with the project team to write the final report once data collection is complete. The results of this study will be submitted to the Regional Stormwater Monitoring Program/Stormwater Action Monitoring and will inform NPDES permittees in the specification and design of bioretention facilities that perform well and meet the requirements of the stormwater manual and their permits.