Practical Method for Specifying MSW Landfill Drainage Media to Avoid Turbidity Contamination

Municipal solid waste landfills utilize drainage material (oftentimes a sand with high-hydraulic conductivity) to prevent the accumulation of leachate on the bottom liner. The drainage media must meet specification criteria to ensure adequate performance. At a Florida landfill site, the mine tailings meeting all specification criteria were used as drainage media, and after heavy rainfall prior to waste placement, humic substances washed from the media into unlined stormwater collection ponds, causing elevated turbidity levels. Effluent turbidity of landfill drainage sand can have negative impacts on leachate collection and stormwater systems, but may not be adequately addressed by typical material specifications. Tests were performed on impacted stormwater and the mine tailings, as well as several control materials, and while all met the standard material specification requirements, differences in organic material content and effluent turbidity were noted. Stricter organic content specifications and/or additional test specifications for effluent turbidity are recommended to prevent turbidity impacts caused by organic material in drainage sand.