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Landfills and the Environment

Design

DesignThe San Juan County Regional Landfill is designed to dispose of non-hazardous solid wastes. All disposal areas are constructed with a composite liner system and leachate collection system. The leachate collection system gathers wastewater that is generated by the overlying municipal solid waste.

The primary liner consists of a synthetic 60-mil-thick high-density polyethylene (HDPE). Under the primary liner is 2-ft of low permeability soil, or equivalent material. Together, these two components of the liner system prevent contaminants from penetrating the surrounding environment. 

The leachate collection system consists of synthetic drainage material called geocomposite. The geocomposite is comprised of high-density polyethylene channels manufactured to rapidly convey liquids such as leachate. It is considered to be an acceptable equivalent to one-foot of granular drainage material. A non-woven filter geotextile is attached to prevent infiltration of soil that will clog the geocomposite. Base grades are sloped to a central collection sump, which is designed for subsequent removal of leachate. 

All areas of the liner system are protected by a 2 ft thick soil layer. The soil layer prevents the overlying waste from penetrating and damaging the liner system. 

Open refuse is minimized by the construction of daily work areas sized to handle only each day's volume, and subsequently covered and sealed with soil at the end of each day.

Groundwater MonitoringGroundwater Monitoring

The current groundwater-monitoring program includes monitoring wells placed around the active areas of the San Juan County Regional Landfill. The locations of the wells are principally selected to intercept groundwater that flows beneath the landfill. The depth of the monitoring wells has been selected to monitor the uppermost groundwater. Monitoring wells are sampled and inspected on a regular basis in accordance with state and federal guidelines.

The site is underlain by alternating sandstone, claystone. 

Landfill LinersLandfill Liners

The landfill liner system and its components, including the HDPE (high density polyethylene) liner are designed to provide maximum protection to the environment. Installation of the liner system is supervised and inspected to ensure that it meets or exceeds environmental standards. 

Preparation of the existing ground surface is performed prior to construction of the liner system to achieve the design subgrade configuration and remove rocks that could penetrate the liner. The 60 mil HDPE liner is installed over the GCl material. Finally, a drainage geocomposite is placed above the HDPE liner. Geo-textile is installed over drainage geocomposite in order to filter solids out of the leachate. The HDPE liner is fabricated, installed, tested and repaired in accordance with approved guidelines. All manufacturer's recommendations and installation procedures are overseen by independent Quality Assurance personnel. Prior to implementation, Quality Assurance/Quality Control (QA/QC) consultants certified that the geosynthetic materials have been properly installed. 

Leachate Collection and Removal Systemleachate collection and recovery

State-of-the-art technologies prevent environmental contamination. One mechanism for ensuring environmental safety is a leachate collection system. Leachate is precipitation that lands upon open cells and percolates through them. Our leachate collection system removes this liquid from the cell so that it does not rest on the cell liner. The liquid is removed and treated. 

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Gas MonitoringLandfill Gas Monitoring

A regular gas-monitoring program has been in effect at the landfill since its inception and includes permanent probes located along the perimeter of the landfill. The probes are installed to monitor the entire depth of waste to ensure that methane gas does not migrate off the landfill property. The gas probes are monitored on a monthly basis.