Black Lake Basin Study

Study Summary
Thurston County conducted a study of Black Lake Basin to identify land use policies to preserve the basin's future health. The study was recommended in the County's earlier Science to Local Policy Study, because the basin is impacted by moderate residential development. 

Study Dates  2013-2015

Completed Work (PDFs)
Final Report
Basin Aerial Map
12 Study Maps 
Maps of Three Future Options


Background on the Black Lake Basin
Black Lake Basin includes almost 5,000 acres that drain into one of the largest lakes in Thurston County. Historically, Black Lake was the headwaters of the Black River system, but since the excavation of the Black Lake Ditch in 1922, it has been linked hydrologically to Percival Creek and drains into Puget Sound via Budd Inlet. The basin is moderately impacted by development, with less than 10 percent of covered by impervious surfaces (e.g., roads and parking lots) and reduced tree canopy. Algal blooms are a recurring and increasing problem in Black Lake. Black Lake Ditch, which drains the lake at its northern end, violates fecal coliform and dissolved oxygen standards.

In the coming decades, the Black Lake Basin, which includes northwestern Tumwater and its unincorporated urban growth area, will see new commercial and residential development under current zoning. This growth could increase the amount of impervious surfaces and stormwater runoff, exacerbating water quality issues. The aim of this project is to identify policies that can be put in place now to preserve the health of the basin into the future.

Public Outreach

Meeting Date
Meeting Materials (PDFs)
​October 30, 2014 (Community Workshop)
Maps of Three Future Options
​April 9, 2014 (Community Workshop)
Presentation - About the Science to Policy Project
Fact Sheet - Black Lake Basin
Handout - Sensitive Basins
Handout - Urban Basins

Project Funding 
This project was funded in whole or part by the United States Environmental Protection Agency (EPA) under assistance agreement (PO -00J12401-0) to Thurston County. The contents of this website do not necessarily reflect the views and policies of the EPA, nor does mention of trade names or commercial products constitute endorsement or recommendation for use.