Herrera Environmental Consultants Cost Analysis Report

Title: COST ANALYSIS - Washington Department of Ecology Year 2001 Minimum Requirements for Stormwater Management in Western Washington. (click here to view report in pdf format)

Credits: Report prepared for Washington State Departments of Ecology and Transportation. Funding provided by the Washington State Department of Transportation.

In 1993, Herrera Environmental Consultants prepared a report on the cost of implementing Ecology’s Minimum Requirements for stormwater management, as described in the 1992 Puget Sound Stormwater Manual. This report updates the 1993 analysis, drawing on the examples used in that study. The intent is to compare the difference in cost of complying with the 1992 manual versus Ecology’s 2001 manual.

This report provides information on costs of stormwater control measures required for new single-family residential and commercial developments in western Washington based on the minimum requirements set forth by the Washington Department of Ecology (Ecology) in the 2001 Stormwater Management Manual for Western Washington (manual). The manual describes the stormwater management requirements applicable to various development and redevelopment scenarios, including many types of development other than single-family residential and commercial land use. There are a multitude of development scenarios that could potentially be evaluated for stormwater management implementation costs but doing so would require extensive amounts of time and effort. This report discusses the range of stormwater management costs that could be expected for some representative examples, and the reader must necessarily use the information as a general guide to understand the cost implications for a specific project of interest.

The overall trend that can be expected in stormwater management costs for sites where infiltration cannot be accomplished is a significant increase relative to the costs associated with satisfaction of the 1992 requirements. If infiltration can be accomplished, the overall stormwater management costs may be similar, and possibly lower, in comparison to the costs associated with the 1992 requirements. Some cost components, such as the costs for temporary erosion and sediment control, may not change significantly.