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Thurston County, Washington

The content on the Thurston County website is currently provided in English. We are providing the “Translation” for approximately 10 languages. The goal of the translation is to provide visitors with limited English proficiency to access information on the website in other languages. The translations do not translate all types of documents, and it may not give you an exact translation all the time. The translations are made through an automated process, which may not result in accurate or precise translations, particularly of technical and legal terminology.

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) Presentation

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.