Millersylvania Water Improvements

Grayling Engineers assisted the Washington State Parks and Recreation Commission with the preparation of a preliminary design report for the replacement of the aging potable water system at Millersylvania State Park in Thurston County, Washington. Originally constructed in the 1930s, the existing system includes a partially buried 21,000-gallon gravity reservoir, aging PVC distribution mains, and two groundwater wells. Increasing leakage, limited reservoir access, pressure deficiencies, and lack of fire flow capacity prompted the development of a comprehensive basis of design for system replacement.

The recommended improvements include construction of a new approximately 91,000-gallon cast-in-place concrete reservoir at the Tilley Square site, a booster pump station with dual adjustable frequency drive pumps and backup generator, new 3- to 4-inch distribution mains (including HDD installation through wetlands), stormwater improvements, and fire access provisions. The project also includes demolition of the existing reservoir, hydraulic modeling, storage and demand analysis, geotechnical feasibility review, and coordination of environmental and land use permitting.