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Landfill Closure Issues. Stormwater Retention. Florida Regulations - must collect and detain runoff from first 1” of rainfall (for > 100 acres, 0.5” for < 100 acres) detain for 24 hrs. Stormwater Control. Direct surface water run-off away from the landfill . Stormwater Management.
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Stormwater Retention • Florida Regulations - • must collect and detain runoff from first 1” of rainfall (for > 100 acres, 0.5” for < 100 acres) • detain for 24 hrs.
Stormwater Control Direct surface water run-off away from the landfill
Monitoring • Leachate head within landfill • leakage through landfill liner (groundwater) • ambient air quality • gas • leachate quality • stability of final cover
Minimum Groundwater Monitoring One line of three (minimum) well down gradient from landfill perpendicular to groundwater flow, penetrating entire saturated thickness of aquifer (1/250 ft of landfill frontage at boundary of site or at surface water)
Minimum Groundwater Monitoring • One well immediately adjacent to downgradient edge of filled area at point where leachate plume meets GW. Screened to intercept water table • one well in area upgradient from landfill
Monitoring wells Groundwater Direction Landfill
Monitoring Wells Landfill Water Table Confining Unit
Closure • financial assurance criteria • estimate cost of closure/post closure care • demonstrate financial assurance • cash • irrevocable letter of credit • trust funds with licensed trust company or state • surety bonds
Final Cover Drainage Design Objective: To reduce pore water pressure, avoid seepage-induced instability and limit infiltration
Post closure • 30 years • maintain integrity of cover • maintain LCS • monitor GW • maintain gas monitoring system
Thoughts on Post-Closure • 30-years may not be the right time • Can one ever “walk away”? • Must have a risk based approach to end
The End of Post-closure Care • Regulatory-stipulate 30 years is arbitrary • No clearly defined process on how to exit post-closure care period