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Efficient Storage Through Geomembrane Floating Covers

Properly designed reservoir floating cover systems prevent fluid loss due to evaporation, reduce chemical demand and improve water quality by preventing contamination from bird droppings, airborne particulates, dead animals pollen and other pollutants. Floating covers block off sunlight preventing algae bloom. They also reduce the production of trialomethane (THM) type compounds such as chloroform from forming that result from the combining of organic substances with chlorine due to reductions in chlorine demand. In anaerobic digester systems, floating covers are increasingly being used to capture organic gases and to reduce biological oxygen demand (BOD).

Floating cover systems were introduced over 30 years ago.  Many have provided a service life beyond 20 years. When first introduced, materials and designs were not developed and in some cases had limited success. Today, with advancements in design and materials, floating covers offer the low cost quality solution of choice where water quality standards require potable water reservoirs be covered.

Floating cover applications range from anaerobic digestion covers for wastewater systems, to potable water reservoir covers for municipal drinking water applications. In farming applications they have been successfully used with enzymes to capture methane gas that is used to fuel electricity producing generators that can satisfy 150% of a typical swine farm’s electrical power requirements. This alternative generates renewable "green energy" from an otherwise polluting system that provides zero return on investment. In agricultural and other water management applications, floating covers are increasing being used for evaporation control and odor control.

Floating cover systems offer the best performance when they are constructed with a polyester fabric reinforced geomembrane such as Hypalon® or polypropylene. Reinforced cover membranes with United States National Sanitation Foundation Standard No. 61 (NSF-61) approval for contact with drinking water are often encountered in thicknesses of .91mm to 1.14mm and are engineered and manufactured to survive the effects of weathering for 20-30 years. Through geomembrane polymer advancements, Layfield has developed durable long term floating covers systems for evaporation and odor control from .75 mm to 1.0 mm unsupported geomembranes such as Enviro Liner® 6030,  6040 and .75 mm unsupported polypropylene.

Floating cover systems require site specific planning and design to be successful.  Floating covers must be designed to rise and fall with varying reservoir water levels and have drainage systems for the removal of storm water. Depending upon site, storm water can be conducted through a reservoir and drained to the outside by way of gravity flow or removed from the cover via electrical pumps and discharge hoses. Reservoir access is maintained by the installation of hatches. There are essentially two types of water-tight floating cover systems commonly specified for drinking water storage applications: the weight tensioned defined sump style (Burke® style) and the mechanically tensioned (REVOC® style). Weight tensioned defined sump covers use a combination of floats and weights to affect tension and surface geometry. The geometry is controlled in such a manner that strategically located drainage channels or sumps are formed for the collection of storm water. Storm water is conducted through the sump channels to either gravity drains or sump pumps for removal. Mechanically tensioned (or REVOC® ) type systems use spring or weight loaded cable tension to achieve definition and stability in the cover. A REVOC® style floating cover system consists of tension producing elements attached to the cover’s interior at specific intervals all around the reservoir’s perimeter. The mechanically tensioned portion of the cover is thus held into place and becomes a defined plate that is protected from wind uplift and drifting. The outer cover perimeter is relaxed and forms a sump where storm water can be diverted off of the cover through a drainage system. The cover geomembrane material makes direct contact on top of the water without additional floats for buoyancy. The REVOC® cover system requires less maintenance and lower cover membrane replacement costs and is generally considered a superior system in cold weather applications. The key design elements making both types of floating covers hugely successful is that they are water-tight and designed to function at all water levels without undue stress.

Floating covers are a very economical method of protecting precious water. The cost can be 20% of that for other cover options. Industry recognized guidelines exist for the design, installation and maintenance of floating cover systems. An example is the American Waterworks Association (AWWA) standard D130-87 which contains the most current standard practices observed for system compliance to US national health and safety regulations. The California-Nevada Section American Water Works Reservoir Floating Cover Guidelines dated March 1999 offers an excellent source of design, operations and maintenance guidelines. Most agencies have found the best way to procure a state of the art operational floating cover system is to engage in a negotiated contract method with an experienced and reputable supplier. The second best alternative is to work through a qualified engineering firm to develop proper plans and specifications for the solicitation of competitive bids.

Layfield Environmental Systems Corporation (formerly CW Neal) is an industry leader and innovator of high quality floating cover systems. We offer both weight tensioned defined sump and mechanically tensioned floating cover systems. In an effort to promote public health and safety as well as the floating cover industry, Layfield is actively involved in developing guidelines for North American state and national regulation pertaining to floating cover systems used in municipal drinking water applications.

Layfield Environmental Systems offers the most advanced mechanically tensioned or REVOC® style floating covers available. Our patent pending cover tensioning motors are a major breakthrough in floating cover technology representing an ongoing commitment to the water storage industry. Many other design elements including inflation systems introduced to the floating cover industry by the former C. W. Neal have become standardized details adopted by many municipal drinking water agencies. As with all covering technologies, maintenance issues are a concern. To address this, Layfield has made many inroads to ease operational maintenance with such provisions as floating stair steps and pathways leading to cover hatches that are large enough to easily accommodate fully outfitted inspection divers. We also pioneered floating cover inflation systems that raise floating covers allowing complete reservoir and cover inspection from within the interior.

Layfield offers full design/build, rehabilitation and maintenance capabilities with the most experienced staff available anywhere. Proper consideration and effort towards operational considerations, design, manufacturing, fabrication, field installation, quality assurance, personnel training and proper operations and maintenance plans are essential to the success of any floating cover.


Revolutionary Waste Management Using Geomembrane Floating Covers

Layfield Environmental Systems Corp, in cooperation with industry partners, can design and install anaerobic digester and bio gas collection cover systems for swine and dairy farming applications. These proven agricultural systems use enzymes to enhance methane gas production from the farm wastes. The Methane gas is used to fuel an electricity producing generator that can satisfy 150% of a typical swine farm’s electrical power requirements. This alternative generates renewable "green energy" from an otherwise wholly polluting loss type system. In the United States, a typical system installation can pay for itself within 5 years while reducing waste and odor pollution. Excess gases can be channeled into various regeneration applications or metered and put into the municipal power grid. Having a system properly engineered and designed is a crucial step to the development of a successful system. Since no two installations are the same each project requires site specific considerations.Construction plans can then be developed which specify the various components required for the system to be effective. Layfield can then furnish and install the critical components required.

Layfield Environmental Systems is an industry leader with cover and containment systems used in dairies, poultry farms, feed lots, landfills and human waste disposal facilities.

 

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