Phase I Municipal Stormwater Permit Monitoring: Stormwater Treatment and Hydrologic Management Best Management Practice (BMP) Evaluation Monitoring (S8.F)

S8.F requires Phase I Municipal Stormwater Permittees to measure the effectiveness of stormwater treatment and hydrologic management BMPs. Permittees are required to collect influent and effluent water quality and flow data from each BMP in accordance with Ecology’s Guidance for Evaluating Emerging Stormwater Treatment, Technology Assessment Protocol-Ecology (TAPE). This monitoring component also includes a requirement for Phase I Permittees (with the exception of Ports) to monitor the effectiveness of one flow reduction strategy that is in use or planned for installation. This monitoring includes continuous rainfall and runoff monitoring.

Ecology required Phase I Permittees to develop Quality Assurance Project Plans (QAPPs). The following describes each Phase I permittee’s effectiveness study with links to each QAPP.

King County

King County is monitoring two, large sand filters and two, pre-settling basins. These stormwater facilities are located at a multi-family development on the East-Lake Sammamish Plateau.

S8.F.7: Flow Reduction Strategy
King County is monitoring organic compost added as a soil amendment in an urban planned housing development (part of the Redmond Ridge project). Amending soil is an attempt to mitigate the traditional clearing and grading of land for building that leaves little organic soil in place after construction has been completed. The study hypothesis is that adding organic compost to native soils will absorb more stormwater than un-composted soil and enhance the growth of the planted landscape that will additionally prevent more runoff. Flow will be monitored from a basin with compost-amended soils and from a basin in a similar development without compost-amended soils (control). The paired data will be compared to determine differences between the basins.

King County’s QAPP for S8.F and S8.F.7

Snohomish County

Snohomish County is monitoring four modified wet ponds to determine which design is most effective at removing pollutants from stormwater. These wet ponds are located northeast of Mill Creek, southeast of Mill Creek and two ponds located south of Everett.

S8.F.7 Flow Reduction Strategy
For flow reduction, the County is monitoring a modified drainage structure in a subdivision southeast of Mill Creek to determine if a reduction of stormwater volume is occurring from retrofits designed to encourage infiltration.

Snohomish County’s QAPP for S8.F and S8.F.7

Clark County

Clark County is monitoring two treatment wetlands located in the City of Vancouver, WA and a two-facility treatment train located near the Klineline Bridge over Salmon Creek on Highway 99. The first treatment facility is a bio-filtration swale followed by a StormFilter® media filter vault system equipped with 28 media filter cartridges with zeolite-perlite-granular activated carbon filtration media.

Clark County’s QAPP for S8.F

S8.F.7 Flow Reduction Strategy
The County is also monitoring the flow reduction capability of permeable pavers as a low impact development (LID) practice at the Vancouver Toyota car dealership.

Clark County’s QAPP for S8.F.7

Pierce County

Pierce County is monitoring two wet ponds and two media filter systems. The goal of monitoring is to compare the performance of the extra large perlite (XLP) media and zeolite-perlite-granular activated carbon filtration media (ZPG) media for TSS removal.

Pierce County’s QAPP for S8.F

Pierce County’s S8.F QAPP Addendum

S8.F.7 Flow Reduction Strategy
Pierce County is testing the flow reduction potential of a parking lot retrofitted with porous pavement and bio-retention. The purpose of this project is to enhance infiltration and ground water recharge and reduce the direct peak flow discharge in Spanaway Creek.

Pierce County’s QAPP for S8.F.7

City of Tacoma

The City of Tacoma has selected two bio-infiltration facilities at the Salishan Hope VI Redevelopment Project Site and two bio-filtration facilities located at East 32nd Street and Trolley Court for BMP evaluation monitoring.

S8.F.7: Flow Reduction Strategy
The City is testing the potential of pervious pavements at the Tacoma Landfill for flow reduction. Tacoma is testing 3 types of pervious pavement systems (pervious concrete, pervious pavers and pervious asphalt) along with a control, standard asphalt.

City of Tacoma’s QAPP for S8, S8.F, and S8.F.7

City of Seattle

The City of Seattle has selected two catch basin StormFilter® for BMP evaluation monitoring. The devices consist of a modified catch basin that houses rechargeable cartridge filled with zeolite-perlite-granular activated carbon filtration media. Seattle is also testing the water quality treatment performance of a bio-retention soil mix located within mesocosms at the Washington State University Research and Extension Center in Puyallup, WA.

City of Seattle S8.F (Catch Basin StormFilter®)
City of Seattle S8.F (Mesocosm Study)

S8.F.7 Flow Reduction Strategy
For flow reduction, the City is monitoring two bio-retention swales located in the High Point development in West Seattle.

City of Seattle S8.F.7
Note: Ecology approved this QAPP only for meeting the hydrologic management BMP monitoring requirements in S8.F. This QAPP includes other monitoring that was not used for the purposes of meeting Phase I permit monitoring requirements.

Port of Tacoma

The Port of Tacoma selected to test two Filterra® systems located on a Port-owned site. The Port is monitoring the effectiveness of these flow-through systems for removing metals, total suspended solids and other pollutants.

Port of Tacoma’s QAPP for S8.F

Port of Seattle

The Port of Seattle selected two oil water separators located at two Port-owned terminal sites for BMP effectiveness monitoring. One oil water separate is located at a container operation facility across the East Waterway from Harbor Island near the heart of downtown Seattle. The other oil water separator is located at Terminal 25, currently used as a container terminal.

Port of Seattle’s QAPP for S8.F Coming soon!

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TAPE Guidance

Stormwater Monitoring Report Guidance-Phase I

EAP Quality Assurance

Phase I Permit

Phase I S8.D Monitoring

Phase I S8.E Monitoring