As a regulated Solid Waste Disposal Facility, the ARL, under the direction of the Solid Waste Services Department, is committed to adherence to State and Federal Regulations. The facility design encompasses several features that exist specifically to protect the public and the environment. The days of the open dump have long passed and ARL represents the current standards in solid waste disposal technologies. The following paragraphs describe some of the monitoring programs and design features that ARL utilizes to protect the environment.
At the ARL facility there is a network of groundwater monitoring wells located around the perimeter of the facility. These wells allow access to groundwater beneath the site. The network currently incorporates 4 up-gradient wells and 4 down-gradient wells. Up-gradient wells determine the quality of groundwater before any influences from the site and down-gradient wells indicate the influence of the facility on groundwater quality. If the facility has no effect, the up-gradient and down-gradient groundwater quality would be equal. The wells are sampled semi-annually by a qualified groundwater sampling contractor. Groundwater samples are sent to analytical laboratories for testing and the results are compiled in a report that is transmitted to the Alaska Department of Environmental Conservation. The contractor analyzes the lab results to determine if there are any signs of groundwater contamination. To date, no contamination from the ARL facility has occurred.
Leachate Collection and Disposal
As refuse is deposited, it is subjected to the elements including snow and rain. The water from these events that comes in contact with the refuse has to be collectedand treated. This liquid is called leachate. The formation of leachate best resembles a coffee-making machine. As water percolates through the garbage, it collects pieces or samples of the refuse. The dirty water (leachate) or "coffee” collects at the base of the refuse on the base liner system. Under state and federal regulations, the facility must remove collected leachate from the landfill regularly to keep the leachate level on the baseliner to less than twelve (12) inches. At ARL, the collected leachate is transferred to holding ponds through plastic piping.
The holding ponds are double lined with plastic liners. Plastic liners and pipes are used because of their high ability to resist degradation. The leachate is held until it can be loaded into a tanker truckand ultimately discharged to the Point Woronzof Wastewater Treatment Facility. While the leachate is stored, blowers force air through the leachate from piping on the base of the pond. The air speeds up the ability of the leachate to reduce the biological oxygen demand (BOD). By reducing the BOD, the leachate can be more easily handled at the wastewater treatment plant. The two operating lagoons are sized to handle the required capacity of the currently developed site.
Liner and Final Cover
Under the refuse at ARL is a composite liner system. This system includes two layers of geosynthetic materials which provide containment for the refuse. The layers consist of a geosynthetic clay layer or GCL and a high density polyethylene (HDPE) plastic liner. The GCL is made from two geotextiles (synthetic fabric) sandwiched around a bentonite clay layer. The bentonite is a mineral that absorbs large quantities of water and expands as it adsorbs. If leachate was to contact the GCL, the bentonite would absorb the leachate and expand, closing up the hole where leachate leaked through. The HDPE liner is located on top of the GCL. The liner used at ARL is 80 mils thick which is 80/1000 of an inch thick. The HDPE material is similar to the plastics used for milk cartons, but much thicker.
The liner provides an impermeable layer under the refuse. All leachate generated gets collected on this liner and removed for treatment. Together, these layers provide a barrier that protects the groundwater from potential contamination. When the landfill is completed, a final cover will be placed over the entire site. The final cover will include similar materials as the base liner as well as protective soils. The protective soils are placed on the liner system to protect against damage from the environment and they also allow for vegetation to be established. The liners help to keep water from entering the refuse and creating more leachate, plus they help to keep landfill gas from being released to the atmosphere. With a liner beneath the waste and a liner above the waste, the waste will be encapsulated and prevented from causing harm to the environment. View a detail of the Liner System.
As refuse decomposes, gases are generated and released. Landfill gas contains three primary ingredients: 1) methane (CH4), 2) carbon dioxide (CO2), and 3) trace organics. Methane is a colorless, odorless gas that is highly flammable. Methane is the same gas found in natural gas lines. Since it is odorless, the gas company adds a perfume agent to allow leaks to be detected by smell. Carbon dioxide is also colorless and odorless but is non-flammable. Both these gases are considered to be contributors to greenhouse gases and are detrimental to the ozone. As such, large landfills are required to collect and control gases from being emitted. The trace organics in landfill gas are responsible for the odors often associated with landfills. They represent a very small fraction of landfill gas (less than 2%) but they are the source of most of the complaints that some landfills receive.
Under New Source Performance Standard (NSPS) provisions of the Clean Air Act, ARL will be required to eventually install a landfill gas collection system. The estimated date for operation of this system is approximately 2006. At that time, ARL will collect the landfill gas and direct it to a system for treatment. Most often, treatment is accomplished in a landfill gas flare where the methane and organics are incinerated. Methane has been estimated as being 23 times worse than carbon dioxide is to the atmosphere and its effect on the ozone layer.
ARL monitors a series of gas probes around the facility to ensure that landfill gas is not migrating through the surrounding soils. As the methane portion of landfill gas is highly flammable, testing is performed at ARL once every quarter for its presence in the soils. If landfill gas was detected in the soils, ARL is required by state and federal regulations to take necessary action to protect human health and the environment. These probes act similarly to groundwater monitoring wells, which are monitored for groundwater contamination from leachate.
Bird Control Systems
With the proximity of the landfill to Fort Richardson, the US Army and the Federal Aviation Administration expressed concerns over bird hazards to aircraft. As part of the Municipality’s agreement with the Army, a bird control program was developed to deter birds from accumulating at the landfill. The bird control system involves the use of cables that are strung across the landfill above the ground surface.
These cables are suspended well above the working equipment and are spaced at approximately 40-foot intervals. Seagulls often cause the largest bird problem at landfills. These birds tend to migrate to landfills as a source for food. The cables confuse the seagulls who are not capable of understanding how to land under the cables even though there is plenty of space between the cables. To date, the staff at Fort Richardson has been pleased with the control of birds at the facility.