In an icy, cold fog, 11 men began the long-awaited process Thursday of patching the holes in Prospect Lake. The men, working for two contractors, laid a polyvinyl chloride membrane liner — PVC, for short — across a small part of the lake bottom.
They will work through July 1 — hoping to lay two acres of PVC a day if the weather cooperates — and turn over the job to the city, which plans to fill the lake by Labor Day. This PVC liner is Colorado Springs’ answer to a 50-year leak in the Memorial Park swimming and fishing hole. It comes after 2½ years of receding shorelines have left the 51-acre lake unusable, and after voters gave up tax refunds April 5 to let the city fix the problem. “This is wonderful to see it going,” Parks and Recreation director Paul Butcher said as he looked over the work. “I have to confess: Two years ago we didn’t know how we were going to seal this permanently.” An anonymous donor offered to give the city enough clay to line the lake last year, but officials determined that type of clay was permeable. The only effective kind, bentonite clay, would have to be shipped by train from Wyoming, and Butcher didn’t like that solution. He settled instead on the more expensive — $1.8 million — but more durable liner, about as thick as the material in an inner tube. PVC is put on the bottom of hazardous material dumps, landfills and other lakes. Once 150 PVC sheets are wrapped around lake edges and bolted to the wall of the south-end fishing dock, they will be welded together to form a continuous liner. It will be covered by a geotextile fabric to protect lake-bottom rock and glass shards from puncturing it and then will be topped by a foot of dirt. Where the 143-million gallon lake once lost 2 million gallons of water a day, the liner has been shown to leak just 1 million gallons a year in lab tests, Butcher said. Even that number is exaggerated because lab tests don’t occur in real conditions, said Kyle Hier, president of Scientific Site Construction, the company installing the liner. He expects an influx of soil to seal the lake naturally and believes the liner won’t ever have to be replaced. Good weather is key to the project. The soil can be neither too wet nor too dry if it is to cling to the liner, parks financial analyst Mike McCauley said. So, there is the rub: To repair and refill a 114-year-old man-made lake, the city must get cooperation from nature. “This whole project is extremely weather-dependent,” McCauley said. CONTACT THE WRITER: 636-0184 or firstname.lastname@example.org