Floating Cover for Massive Potable Water Reservoir

Floating Covers


Layfield was chosen to fabricate and install a 45 mil weight tensioned HypaFlex™ CSPE floating cover, rainwater removal system and various cover appurtenances for a massive potable water reservoir in California. This process would require removing and constructing the reservoir floor asphalt liner and asphalt concrete pavement on the access ramp.

Background Information and Challenge

This open-top reservoir was larger than 67 million gallons, located minutes from downtown Beverly Hills, California. The project was highly impacted by traffic and urban density, and the construction site had poor site access and limited space to work. Maintaining a safe worksite based on the site access problems was also a significant challenge and priority. The HypaFlex™ CSPE floating cover needed to be prefabricated in Layfield’s San Diego fabrication plant, and all material shipments needed to be tightly coordinated and scheduled.


An experienced and high-quality project management and installation team addressed the congested site conditions and limited workspace access. The reservoir design had a weight-tensioned cover system made of 45 mil HypaFlex™ CSPE 3-ply in a unique green color.

This cover design allowed it to rise and fall with the change in the freeboard water level. With this design, the excess slack in the cover is pulled down by sand tube weights within the rainwater collection troughs as the water level increases. The defined sump design ensures the cover is always kept in a tensioned position. The floating cover was equipped with the following appurtenances.

  • Seventeen access hatches.
  • Six 12’’ diameter floating cover vents.
  • Five rainwater pump towers with 3’’ submersible pumps that automatically remove rainwater from the top of the cover.
  • Five Storage Rafts that support the fiberglass grating and davit crane assembly for each pump tower.
  • Five textured walkway surfaces that are located from the top of slope and extend to the rainwater collection troughs.
  • One 210LF air baffle on the underside of the floating cover located 202’-6’’ south of the inlet spillway.


There was excellent communication and cooperation between the project owner, engineers and floating cover installation contractor. The project was completed on time and within budget while maintaining strict safety standards.

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