With a benchless design, the following items can reduce overall costs.
- Reduction/elimination of diversion berms and down slope channels
- Reduction/elimination of energy dissipation devices
- Reduction/elimination of sediment storage and water quality for smaller pond volume
- Detention of storm water rather than retention allowing for smaller pond volume
- Reduction of maintenance
Elimination/Reduction of Deep Gas Wells
Deep gas wells extending to within feet of the base liner were designed so that their expected radius of influence to collect gas would overlap. One aspect of a gas design that was not often discussed was the ‘radius of influence’ of each gas well was not a 2D object as drawn, but rather it was a 3D area of influence. The gas that migrated above the well screen and beyond the vertical radius of influence would certainly cause pressure to build on the final cover system. Deep gas wells also introduced many new problems. The change in temperature at ~200 feet deep versus the surface temperature caused large quantities of condensate. Condensate, simply state, is instant leachate. Since the wells must be designed to allow the free flow of gas, they are prone to watering in both from the percolation of leachate and the creation of leachate as the deep well produces condensate. This is a major reason why used in conjunction with ClosureTurf®, landfill gas is collected without the expense of these deep wells, potentially eliminating or at least greatly reducing the need altogether.
Borrow pits necessitate the destruction of land. Often times this land is native, undistrubed and it is only being destroyed to provide soil for a landfill cover. Eliminating the need for a borrow pit makes environmental as well as economical sense. Depending upon the proximity of borrow sources, soil can be a costly item to get on site. Not only does ClosureTurf® eliminate this layer, it also reduces the need for construction vehicles to transport.
ClosureTurf® makes it easy to install in smaller, incremental closures. The sooner full cells can be capped, the sooner gas is controlled and captured and leachate is reduced, providing significant savings for the owner.
Accelerated Project Schedule
The consistency offered by a standardized system such as ClosureTurf® provides efficiencies that can be easily realized, from pre-design through construction. From standardized construction details, to a reduction in site elevation surveys, including the elimination of the typical 24” (600 mm) soil layer across the entire surface of the closure cap. A significantly larger amount of closure acreage can be constructed versus a traditional soil cover, effectively allowing more projects to be constructed with a given set of fixed resources. Typically, ClosureTurf® installs at least 50% faster than traditional covers.
Post ClosureTurf® Care
The annual maintenance costs for ClosureTurf® runs, on average, 90% lower than those for a traditional soil and vegetated cover system. The following is an example of a maintenance activity comparison.
- Over a 30-year period, the average cost to maintain a prescriptive cover is $1,200-1,500 acre/year. ClosureTurf averages around $250 acre/year.
- To date, no more than 2% cumulative (from construction completion to present day) sand loss has occurred on any ClosureTurf® site.
- Several ClosureTurf sites have experienced hurricane-force winds and multiple 100- year storms. The most severe storm event occurred at a 25-acre closure in Pensacola, Florida, with the storm occurrence exceeding 500-years (25+ inches of rain over 24 hours). The required maintenance to bring the installation back to specification was performed solely with 1 infill spreader and a 3-man crew over 2.5 days.
- The projected long term performance is well in excess of 100 years for the turf and 400 years for the membrane. As part of a redundant protection approach, the engineered turf backing is designed to resist UV from potential exposure. Any infill that may be dislodged due to unanticipated concentrated flows or settlement does not require immediate or even annual infill addition (suggest a 5-year evaluation of infill condition). ClosureTurf eliminates on-going maintenance in perpetuity for soil versus over 100 plus years of stability.
- Sites experience less erosion (5 to 10 cy per acre per year for soil versus negligible for ClosureTurf).
- ClosureTurf provides predictability of final cover performance and post-closure maintenance costs. This predictability is assured independently of site-specific or weather-related factors. Furthermore, this predictable performance is economically competitive with typical methods.
ClosureTurf is designed to passively allow LFG to rise to the surface, and once trapped underneath the structured geomembrane, collection points across the surface which are integrated into the geomembrane component and can relieve the system actively or passively based on specific site needs and desires. This collection mechanism provides for an increased quantity of gas collected as well as an increase in quality of gas collected all because gas collection can be performed at the surface of a landfill. Surface collection also reduces protential oxygen intrusion through wells and supports a safer gas management system with much lower exposure to oxygen migration into the landfill.
Reduction of Leakage
HELP Model and JP Giroud Model analyses prove ClosureTurf has significantly less leakage than traditional soil covers.