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Wastewater Reservoir and Floating Cover – Chehalis, WA




PROBLEM: The City of Chehalis, Washington, desired to expand their water system.

They wanted to keep the cost reasonable, and yet provide a long term reservoir with a cover of some type as required by the State of Washington.

SOLUTION: Construct a Reservoir System using Geosynthetic Products. An HDPE Liner and Reinforced Polypropylene Floating Cover.

MATERIALS REQUIRED: 8 ounce Non-Woven Geotextile Pad. 60 Mil HDPE Liner systems, and a 45 Mil thick Reinforced Polypropylene. 4 inch by 12 inch by 9 foot Polyethylene Foam. Two submersible pumps were installed on the cover.

CONSTRUCTION DETAILS: Prepare the dirt subgrade to accept a liner system. Install a concrete ring wall around the basin to provide a system to attach a plastic liner and floating cover system. Install an 8 ounce non-woven geotextile pad over the subgrade surface. The next step is to install a 60 Mil HDPE Smooth liner and secure it in to the perimeter concrete ringwall. Once the liner has been installed, a 45 Mil Reinforced Polypropylene cover with foam floatation and a weighted ballast system was installed. The purpose of the weighted balance system is to direct the rain water to the two submersible pumps that are on the cover and remove that rain water to the airport storm drain system.


8oz. Non-Woven Geotextile 60mil HDPE

45mil RPP Polyethylene Foam Submersible pumps

AREA: 65,000 SF