CASE STUDY: DOMESTIC SEWAGE LAGOON
USING 30 MIL PVC WITH A 12” SOIL COVER
PROBLEM: The city of College Ditch Washington wanted to construct a domestic waste water treatment pond that would blend in with the local area and look like a natural lake.
SOLUTION: The material of choice for this application was 30 mil PVC which has over 40 years of application history for similar facilities. PVC is a tough geomembrane that when protected from the sun by 12 inches of soil will last 30 years or more.
CONSTRUCTION DETAILS: The subgrade was prepared utilizing select soils where fines did not exceed ½ inch in size. The subgrade was rolled and compacted. A perimeter anchor trench was dug 24 inches back from the top of the slope. The PVC panels 100 foot by 230 foot (23,000 SF) were deployed by a crew of 8 men. 100,000 SF of 30 mil PVC can be deployed in one day. The liner was affixed to the penetrating pipes by booting custom fitting pieces of 30 mil PVC and banding with hose clamps. The 12 inches of backfill was accomplished by constructing a 36 inch thick roadway down to the toe of the slope and then fanning out a 24 inch pad where trucks could turn around and drop their load. This resulted in a fan shape movement of dirt onto the liner. Trucks went in and out the same road. Dozers spread the cover material out to uniform depth, across the base of the pond. Remaining slopes were covered by pushing the dirt up slope to the top. The liner deploy crew worked ahead of the contractor deploying the soil cover. Once completed, the slopes were sown with grass seed and the waste water started entering the facility.
PROJECT: Natural looking lake that functions as a waste water containment pond.
LOCATION: College Ditch, WA ENGINEER: CONTRACTOR:
LINER INSTALLER: Northwest Linings & Geotextile Products, Inc.
MATERIAL: 30 mil PVC
AREA: 300,000 SF