Monarch Hill Landfill is a 385-acre landfill with a waste flow of 5,000 tons per day, located in Pompano Beach, Florida. It is one of 267 landfill sites, and over a thousand facilities owned and operated by Waste Management, Inc., one of North America’s leading solid waste services providers.
SCS Engineers continues to support the Monarch Hill Landfill (since 1998), providing liquids management expertise in the design, permitting, construction and monitoring phases of numerous projects.
Reducing Leachate Formation
SCS helped decrease leachate formation as part of overall landfill design and operation.
- Temporary caps. SCS designed and provided monitoring services during installation of a 10-acre temporary geomembrane cap over a portion of the top intermediate plateau of the landfill. It reduced leachate generation, decreased odors, increased gas collection efficiencies, and addressed leachate seeps on the slope, as well as making surface water runoff over the top of the landfill easier and more effective.
- Final covers. SCS designed, permitted, and provided monitoring services during construction of six partial closure projects.
- The final covers were equipped with leachate toe drain systems below the final cover geomembrane, enabling leachate seeps to be collected and disposed of effectively. This also allowed collection of gas from the lower portion of the slope after completion.
- Rainwater toe drain systems above the final cover geomembrane enabled water to be collected and diverted to the landfill perimeter ditches, preventing pore pressure build up and keeping the system stable.
- Tack-on swales were implemented to catch runoff and convey water to downchute pipes. They could be easily adjusted based on the size of each partial closure and the overall management of storm water.
Leachate Management
SCS designed, permitted, and constructed a leachate management conveyance system.
- Conveyance system. The leachate is pumped to a publicly owned treatment plant (POTW) a few miles south through dedicated buried 8-inch pipe. Special booster pump stations on site provide additional pressure. The cost of leachate disposal is offset by accepting sludge from the POTW at the landfill. High moisture content sludge is mixed with incoming waste to ensure the stability of the landfill slope.
- Ash monofill leachate. The leachate from an existing closed ash monofill is handled separately, before being mixed with leachate from the rest of the landfill and entering the off-site line to the POTW.
- Liquids from gas wells. Liquids from gas wells are stored in tanks to settle suspended particles before the liquid is pushed into the leachate force main. Condensate collected from the gas system is placed directly in the leachate force main.
Stormwater Management
SCS designed, permitted, and constructed a significantly complicated stormwater management system for the entire 525-acre facility, to handle a 25-year, 72-hour storm. SCS continues to monitor water quality discharged from the site and carries out compliance reporting summarizing sampling and laboratory analysis.
- Features. The stormwater system includes drainage perimeter ditches that are classified as dry detention systems connected to a wet detention pond. The permitting agency allows infiltration of stormwater in detention system into the underlying aquifer to be incorporated in the model during the storm period, but percolation is allowed after the storm is over.
- Continued redesign. With each lateral expansion to the landfill footprint, SCS redesigned the stormwater system at the site-level to accommodate the larger quantity of runoff reaching the landfill perimeter system.
- Grading plan. SCS also prepared a grading plan for each lift of waste placed in the landfill (or in a new cell) with proper slopes to maximize runoff from the intermediate cover over the plateau of the lift to specific temporary downchutes. This allows for continued filling in dry conditions without the risk of water running into the active face.
