Part 2: 4 Key Factors in Selecting Reinforced Ethylene CoPolymer Geomembranes for Reuse Impoundment Applications

Series: Efficient Reclaimed Water Storage Using Geomembranes

Part 2: 4 Key Factors in Selecting Reinforced Ethylene CoPolymer Geomembranes for Reuse Impoundment Applications

In Part 1, background was provided for the water reuse industry and the need for extended storage of reclaimed water due to seasonal applications such as irrigation. Now, let’s look at two projects that demonstrated the need for a reinforced Ethylene CoPolymer geomembrane to line storage impoundments for reclaimed water. 

Two projects are contrasted below: 

The Olivenhain Municipal Water District in San Diego recycles all its treated effluent. In fact, the plant does not have a discharge permit. To have adequate assurance of sufficient containment capacity, an effluent storage impoundment located adjacent to the Water Recovery Facility (WRF) was expanded and the geomembrane was replaced. The site is very urbanized, located between major highways and surrounded by residential developments. Minimal offline time for site modifications and liner installation was critical. Granular cover over the geomembrane was not practical due to maintenance requirements and introducing other pollutants into the recycled water.

Olivenhain Municipal Water District

Travis County/Austin TX has an aggressive water reuse program with numerous storage sites of several types throughout their system. Municipal Utility District (MUD) No. 4 Barton Creek Section N Effluent Storage Impoundment is the largest above ground reuse impoundment in their system. It is located to serve the southernmost portion of Travis County MUD No. 4 and is designed to store reclaimed water from an adjacent WRF. 

Barton Creek
Source: Bryce Canady, Murfree Engineering

Both projects utilized the XR-5 Geomembrane for lining the effluent storage impoundments, considering the following requirements: 

1. Protective cover could not be used. Granular or earthen cover would introduce foreign matter into the system and increase maintenance. The water needed to stay as clean as possible prior to entering the distribution system for ultimate reuse.  A geomembrane with low thermal expansion-contraction properties was needed in order to remain sunlight exposed. 
2. Construction time was critical. Project delays with extensive field seaming were undesirable. A flexible product that lends itself to a second manufacturing process which creates large panels, minimized field seams, field testing and time-consuming Installation Construction Quality Assurance (CQA). 
3. The geomembrane would be placed on slopes and anchored to walls (Barton Creek). The configuration of both impoundments included areas where the slopes and/or walls required lining. The geomembrane would be supporting its own weight parallel to slopes and would be at elevated temperature from sunlight daily. This loading would be sustained. The selected geomembrane needed high yield tensile strength and seam strength equal to the sheet material. 
4. Redundant protective layers were not practical. Whether under or over, the complexity, cost and delays associated with adding protective layers was to be avoided. A geomembrane was selected which had a composite structure, providing high strength and chemical/environmental resistance in one layer. 

Water reuse projects can be a source of pride for a community. Properly engineering the reclaimed water treatment, storage and distribution systems is essential to success. 

For more information about the Olivenhain project:  https://www.xrgeomembranes.com/project-profiles/xr-geomembrane-achieves-zero-discharge-in-utility-facility

For more information about the Barton Creek project: https://www.xrgeomembranes.com/project-profiles/xr-geomembrane-protects-environment-in-reuse-application