USDA Forest Service

Pacific Southwest Research Station

Pacific Southwest
Research Station

800 Buchanan Street
Albany, CA 94710-0011
(510) 883-8830
United States Department of Agriculture Forest Service. USDA logo which links to the department's national site. Forest Service logo which links to the agency's national site.

Urban stormwater fine sediment filtration using granular perlite

Principal Investigators:
Michael Alexander, El Dorado County Department of Transportation
Russell Wigart, El Dorado County Department of Transportation

Proposal [pdf]

Final Report [pdf]

Please contact Russell Wigart with questions regarding the final report.

Project Summary

The infiltration of stormwater is not always practical as a treatment Best Management Practice (BMP) in the Lake Tahoe Basin, so an effective and economical treatment alternative is needed. The operation of manned sedimentation or filtration systems for stormwater is not currently technically or economically feasible. Granular Perlite has been tested and utilized as an unmanned stormwater filter media, however, the benefits and costs relative to improving Lake Tahoe clarity are not well understood.

In order to further the understanding of the benefits and costs of a perlite filter media as a treatment BMP in the Lake Tahoe Basin, the County of El Dorado conducted full scale testing of this BMP in an existing urban stormwater system that currently discharges directly to Trout Creek.

The final report presents data collected from field tests of perlite filtration from a drop inlet in an urban setting. Actual event based data collected for an entire Water Year indicates that perlite has potential as a water quality BMP. The measured data suggests that the concentration of <16 micron particles can be reduced by as much as 75% on an event basis with an annual load reduction for this study indicating a 43% to 34% reduction respectively for Total Suspended Solids (TSS) and <16 micron TSS. Although the perlite filter data suggests it to be effective at fine particle removal, the study did unveil some operational concerns relative to maintenance and flooding that depending on the site may render this type of filtration not practical for an urban subdivision setting in the Lake Tahoe Basin.