8/3/2019 Como Evitar Baleias

1/2

Free access geosynthetics information

Home About Advertise SHARE GEOSYNTHETICA

Buyer's Guide Calendar Employment Links News Pubs/Tech Docs Resin Specifications Standards Directory

Containment Drainage Erosion Control Filtration Reinforcement Separation

Agriculture Aquaculture Construction Mining Recreation Transportation Waste Management Water Management

G E O G R I D - W A L L R E I N FO R C E M E N T

A Primer and Guide for HDPE Geomembrane Liners in Wastewater Treatment Plant (WWTP) Lagoons -- Avoiding Whales

By Ian D. Peggs

A common "whale" failure in a WWTP liner. These failures arepreventable with proper design and ins tallation understanding.

There continue to be many (whale) failures of geomembrane liners in waste wate r treatment plant lagoons and farm manure ponds . Thesefailures are generally due to leakage through the liner, the inability to remove leakage, the generation of methane, and the subsequentinability to vent the methane.

Therefore, when using high-density polyethylene (HDPE) geomembrane liners, carefully consider the following points during the design andinstallation of these lining systems:

1. Assume that the geomembrane liner will leak a little. It may not, but it probably will.

2. Identify an acceptable leakage flow rate. This is the Action Leakage Rate (ALR) above which theresponsible holes must be found and repaired.

3. There are two frequently specified ALRs -- 20 gpad for landfills unde r a 1 ft head, and 500 gpad formunicipal WWTP with 6 ft head.

4. Zero leakage is not an option. It might be achieved but it should not be relied upon.

5. Whatever ALR is assumed there should be a leak drainage, collection, and removal system underthe geomembrane to handle this leak flow rate.

6. Leaked liquid must be continuous ly removed to minimize the generation o f methane.

7. The floor of the lagoon should be s loped to a sump. It should not be flat.

8. A sloped geocomposite LDS under the liner is desirable for rapid reporting of a leak anywhere inthe liner and for allowing gas venting upslope to a ir vents.

9. A network of geocomposite strips under seams may work but has often been seen not to work.

10. A light geotextile will not function as leak drainage and gas venting system.

11. If concrete embedment strips are used for sealing liner to concrete structures ensure the strip iswell-embedded in concrete -- no voids underneath, and no gaps or concrete between strip butt jointsor beveled corners.

12. Embedment strips and batten strips should be in same plane as liner, not perpendicular w ith only

a short distance between corner and seal.

13. Ensure grinding in preparation for welding is continuous along strip surface.

14. When welding, allow for larger heat sink in strip than in geomembrane.

15. Batten strip sea ls must have gasket be tween geomembrane and concrete.

16. Batten strip bolts should not be cranked tight -- the objective is to compress the gasket no morethan its compressive yield strain.

01/06/2011 geosynthetica.net - geosynthetics

geosynthetica.net//Peggs_PrimerWW 1/2

8/3/2019 Como Evitar Baleias

2/2

2000 - 2011 Geosynthetica.net. All Rights Reserved. tel: +1-561-768-9487 elizabeth@geosynthetica.net CSS

17. Ensure subgrade is well compacted at edge of concrete, and that concrete corner is rounded.

18. Use geotextile cushion between geomembrane and concrete.

19. Try to avoid underwater seals.

20. Liner should be fully supported when filled. This may need some slack in liner between fixedpoints if installation is done at higher temperatures. If installation is done at lower temperatures noslack need be built in.

21. Amount of slackness depends on material coefficient of thermal expansion and temperaturedifference expected

22. The only temperature of interest is the geomembrane temperature.

23. Liner under aerators should be ballasted (concrete slab) to p revent uplift and to provide supportfor aerator at low wa ter levels.

24. Seriously consider a geoelectric liner integrity/leak location survey when the liner has beencompleted.

AN ADDITION, COURTESY OF GLENN DARLIEK of LEAK LOCATION SERVICES INC.

25. Don't plan on puncturing the whales to get rid of them.

Special thanks to Glenn for the contribution! You are right. Mark Smith (formerly of Vector) also addedan entertaining note on Geosynthetica's Facebook page which many of us have heard (and perhapswitnessed the aftermath of): "The most interesting advise I was ever given on whales came from anold timer at a WWTP perhaps 25 years ago. When I asked what he did to ge t rid of them, he smiledand patted the shotgun hanging in the rack of his pickup truck."

The primary objectives are to minimize leakage, remove leaked liquids, and vent gases.

Ian Peggs is the president ofI-CORP INTERNATIONAL, Inc. He can be reached aticorp@geosynthetic.com.

geosynthetica.net is a free technical information r esource for all geosynthetics users and industry m embers. Technical informati on is available regar ding geomembr anes, woven & nonwoven geotextiles,

geogr ids, geosy nthetic clay liner s (gcls), geocomposites, geocells, geotexti le tubes, geonets, geofoam and all other forms of geosyntheti cs. As well, the site cover s many di fferent applications including

environmental & hazardous w aste containment, landfill, mining, agri culture, aquaculture, construction, transporta tion, recreation, er osion control, reinforcement, barr iers, drainage and filtrati on. Please use

the navigation bar above to sear ch for standar ds, specifications, technical guidance tools, calendar of events, industry resour ces, directory, news, employment opportunities, r esin pr icing and much mor e!

Home About Advertise Buyer's Guide Calendar Employment Links News Pubs/Tech Docs Resin Specifications Standards Directory Admin

01/06/2011 geosynthetica.net - geosynthetics

geosynthetica.net//Peggs_PrimerWW 2/2