In 1998 Mason County adopted Washington State Department of Ecology's STORM WATER MANAGEMENT MANUAL FOR THE PUGET SOUND BASIN, often termed "the Technical Manual".

All development and land disturbing activities in Mason County are subject to the minimum requirements which can be found in Chapter I-2 of the 1992 edition of the Technical Manual. For activities exceeding 1 acre of clearing, or creating 5000 square feet of new imperviousness or more, a Large Parcel Storm water Site Plan (SSP) is required to be developed by a licensed engineer. For projects not exceeding the threshold for a Large Parcel activity, construction activities are required to control erosion and sediment within the project area and protect neighboring properties from adverse storm water impacts.

Mason County Public Works can be contacted at 360-427-9670 extension 461 for specific information pertaining to storm water runoff requirements, or visit Washington State Department of Ecology's web page pertaining to water quality issues and requirements.