60 mil RPP & CSPE for Water Reservoir Liner & Cover

Location: Rancho Santa Margarita

Timeframe: 2010 - 2011

Scope of Work: 244 million gallon reservoir Reservoir area 900,000 SF Liner: 60 mil RPP Tan/Black Cover: 60 mil CSPE Tan/Black 18 hatches 71 "T" Vents 40 pumps 

Project Partners: Sukut Construction Santa Margarita WD

Challenge

This large reservoir has a number of unique details. The first is that the reservoir is over 120 feet deep with slopes between 3 to 1 and 2 to 1. This depth led to safety concerns during construction and as well as problems in removing rainwater. During construction the area received rainfall that exceeded the 100 year storm estimate. This rainfall led to slope failures within the pond and erosion underneath some of the lined areas. In some areas the liner had to be removed and the slopes rebuilt before lining could resume.

The second issue with the reservoir was its triangular shape. Designing a defined-sump floating cover on an unusual shape requires some different techniques.

The third issue was a leak that developed after commissioning. The leak was traced to poor concrete in a trench that ran across the bottom of the reservoir. Repairs by divers did not fix the leakage so the reservoir was drained and the cover and liner peeled back for a repair.

Solution

The best solution, as usual, is to hire Layfield to install a REVOC Defined Sump Cover and appropriate liner system. The steep slope issues were managed by adding 6 ATV vehicles and two 10,000 lb zoom-boom type forklifts. Installing the cover on the triangular shape was difficult but not a problem for our skilled Layfield crews.
The repairs to the concrete in the concrete trench were particularly interesting. The trench was filled in with concrete, encapsulating the piping in the trench. Then back-up piping was installed on top of the liner so that it could be maintained when the trench piping reached the end of its life. The liner and cover were repaired and the reservoir is in service.

Results

The reservoir is now in service and meets all performance requirements. The Upper Chiquita reservoir now stands ready to supply 168,000 families in the Santa Magarita Water District with the water they need.

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