The County’s National Pollutant Discharge Elimination System and State Waste Discharge General Permit (NPDES) permit requires that Pierce County maintain mapping data for all known MS4 outfalls and discharge points. The permit requires basin delineation for all tributary conveyances to all known outfalls and discharge points with a 24-inch nominal diameter or larger, or an equivalent cross-sectional area for non-pipe systems.In September 2016, Pierce County Department of Public Works (County) hired Herrera Environmental Consultants (Herrera) to delineate watershed and drainage basin boundaries in GIS to meet the mapping requirements of the current NPDES Phase I Municipal Stormwater Permit. In 2017, Herrera produced an amendment to the original SOW to assist the County with a) conducting a review of 570 existing mapped outfall and discharge points for accuracy and completeness and b)mapping all remaining outfall and discharge points within Pierce County (excluding cities).Herrera has produced a Technical Memorandum documenting all methods and results entitled “Pierce County Drainage Basin and Watershed Delineation Summary Memorandum” (dated December 28, 2017).Please read the metadata (https://matterhorn.piercecountywa.gov/GISmetadata/pdbswm_watersheds_hec.html) for additional information. Any data download constitutes acceptance of the Terms of Use (https://matterhorn.piercecountywa.gov/disclaimer/PierceCountyGISDataTermsofUse.pdf).

The County’s National Pollutant Discharge Elimination System and State Waste Discharge General Permit (NPDES) permit requires that Pierce County maintain mapping data for all known MS4 outfalls and discharge points. The permit requires basin delineation for all tributary conveyances to all known outfalls and discharge points with a 24-inch nominal diameter or larger, or an equivalent cross-sectional area for non-pipe systems.In September 2016, Pierce County Department of Public Works (County) hired Herrera Environmental Consultants (Herrera) to delineate watershed and drainage basin boundaries in GIS to meet the mapping requirements of the current NPDES Phase I Municipal Stormwater Permit. In 2017, Herrera produced an amendment to the original SOW to assist the County with a) conducting a review of 570 existing mapped outfall and discharge points for accuracy and completeness and b)mapping all remaining outfall and discharge points within Pierce County (excluding cities).Herrera has produced a Technical Memorandum documenting all methods and results entitled “Pierce County Drainage Basin and Watershed Delineation Summary Memorandum” (dated December 28, 2017). Please read metadata for additional information (https://matterhorn.co.pierce.wa.us/GISmetadata/pdbswm_watersheds_hec.html). Any data download constitutes acceptance of the Terms of Use (https://matterhorn.co.pierce.wa.us/Disclaimer/PierceCountyGISDataTermsofUse.pdf).