Geomembranes Used on Wastewater Treatment Plants Provide Sustainable Solution

Alan Strecker on Oct 31, 2017 10:09:11 AM

Olivenhain LinerWastewater treatment plants often utilize geomembranes to help protect the environment and maximize resources. In San Diego County, the Olivenhain Municipal Water District (OMWD) treats up to 34 million gallons of wastewater each day. The treated water is provided to the community through 45+ miles of recycled water pipelines. With a seasonal increase in rain, the demand for recycled water drops off and the treated water is stored in a wet weather pond. 

This pond has a 13.4 million gallon capacity and was initially only lined on the bottom. This caused problems as the lined capacity was exceeded. The result was water loss and contaminants entering the water from the unlined slopes. Re-treatment of the tertiary water was required before it was safe for use. Compounding the problem, the existing polypropylene liner was failing.

Given the cost and logistical challenges of replacement of the liner, the district needed a long-lasting option that was much more durable, had superior mechanical strength and was resistant to weathering. The project specification called for an Ethylene Interpolymer Alloy (EIA) based product. EIA is a blended material utilizing stable ethylene-based polymers in a non cryatalline matrix. The result is a stable, UV and chemically resistant, liner.

In 2013, OMWD selected a 36-mil XR-5 Geomembrane from Seaman Corporation to replace the existing liner and the district took this opportunity to extend it beyond the access drive near the bottom to the crest of the reservoir. They liked the cream-colored option because it blended into the environment and helped reduce surface temperature, leading to less evaporation losses. The project met a number of the district’s long-term needs:

  • The Regional Board requires that wastewater treatment plants have 84 days of wet weather (seasonal) storage per 1 MGD (Million Gallons per Day) of treatment capacity.
  • The 4S Ranch pond is a 410 acre-ft pond which equates to capacity of 134 MG.   Or enough storage capacity for 1.6 MGD  
  • The water treatment plant has a capacity to process 2 MGD of wastewater.  It is currently processing 1.0 MGD.  The relined pond helps OMWD to meet long term growth plans.

Completed in 2015, the timing of the project was excellent because the region saw exceptionally large amounts of rain in the winter of 2016-2017.

The finished product allows OMWD to conserve more water more effectively for a longer period while helping to protect the environment.

To learn about how XR Geomembranes work for storage ponds and more, contact XR Geomembranes.

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