By John Trotti

GOLD EXCELLENCE AWARD WINNER
Metro Waste Authority, Metro Park East Landfill

The Metro Park East (MPE) Landfill has been serving residents of Des Moines and surrounding parts of central Iowa since Metro Waste Authority (MWA) was formed in 1969. The MPE Landfill is the largest publicly owned landfill in Iowa, managing approximately 1,500 tpd of solid waste and serving almost 400,000 residents. The facility averages 300 customers each day. In the past 30 years, the MPE Landfill has become one of the greatest environmental assets to the Des Moines metropolitan area. To date, the facility has received approximately 10 million tons of waste. The site receives an average of 450,000 tpy of waste, including about 380,000 tons of MSW; 50,000 tons of construction and demolition (C&D) waste; and 20,000 tons of special waste.

In 1993, MWA, Waste Management Inc., and MidAmerican Energy partnered to provide an environmentally sound solution to the issue of methane gas escaping into the atmosphere: the Metro Methane Recovery Facility. The facility is the first in the state of Iowa to directly produce electricity from landfill gas (LFG). It also is the first joint effort that Waste Management has entered into with a publicly owned and operated landfill for the purpose of landfill gas-to-energy (LFGTE) production.

By establishing the Metro Methane Recovery Facility, located next to the MPE Landfill, MWA and its partners created a way to manage a renewable energy source that is both produced and consumed locally. In the past, methane gas was flared off into the atmosphere, wasting a valuable resource and causing a potential environmental hazard. Today the gas is collected and burned to create electricity that is delivered directly to MidAmerican Energy’s power grid.

More than 70 gas recovery wells, 90% of which are on-line, tunnel 100 ft. deep to collect methane from the landfill. The individual wells are connected to a 10-mi.-long underground piping system through which the gas is drawn to the Metro Methane Recovery Facility. Here, eight engines burn the gas and distribute it to approximately 10,000 homes and businesses in a 6-mi. radius of the MPE Landfill.

Innovation and Creativity

MWA management believes that in order to exceed environmental regulations and customer expectations, it must do all it can to explore innovative and resourceful methods for managing solid waste. In addition to its award-winning and nationally recognized management practices for leachate, methane gas, and ground- and surface-water protection, MWA has implemented the following innovations at the MPE Landfill:

Shredded Waste Tires. In 1999, MWA received a grant from the Iowa Department of Natural Resources (IDNR) to research how shredded waste tires could be utilized for daily operations. MWA now uses these tire chips, which are more cost-effective than gravel, as an alternative drainage material in correcting leachate seeps. MWA also explored the use of shredded tires as an inexpensive sub-base for road construction and the wet-weather pad. Unfortunately, the steel belts in the shredded tires caused many flat tires. Additional processing of the tires to remove the steel prior to shredding would be required to make the program viable.

Mobile Litter Vacuum. MWA created a mobile litter vacuum to remove debris from the litter fences surrounding the MPE Landfill. The system consists of a large blower that creates a vacuum and an 18-in. hose attached to a farm tractor. MPE staff recently modified the "litter vac" with an arm-mounted hose and hydraulic controls so a single employee can easily operate it. This has greatly reduced the amount of labor required to clean litter from fences and keeps the facility cleaner. Additional money has been budgeted to further improve this device.

Compost as Erosion Control. MWA uses the compost produced at the MPE Landfill for erosion control and as a soil amendment throughout the facility. The compost, consisting of larger-size particles, has proven to be an effective mechanism in preventing soil erosion. MWA has also contributed compost materials to an erosion study performed by IDNR and the Iowa Department of Transportation. Not surprisingly, MWA’s compost was most effective in prevention of erosion during the study, as MWA has utilized this material for several years with the same excellent results.

Geographic Information Systems (GIS). All monitoring data generated at the MPE Landfill is entered into a GIS database accessible on the Internet. The GIS provides:

• a fully functional and easily updated system that allows users to access information about the landfill facilities from any location via the Internet;
• a tool that facilitates the preparation of reports used in making future decisions about maintenance schedules, budget planning, facility design, and development;
• a database of monitoring points, events, and water chemistry with mapping capabilities;
• a document control system that allows the user to quickly obtain permits and other important documents.

Settlement Monitoring. MWA has installed several dozen steel plates over the closed areas of the MPE Landfill to monitor landfill settlement during the closure period. MWA predicts that the evaluation will indicate the landfill’s stability in the short and long term and during earthquake loading conditions.

C&D Disposal Area. MWA recently refilled a previously closed area that had settled 10-15 ft. from the maximum elevation of 990 ft. During filling operations, additional volume was gained by the surcharging effect that the waste mass provided. By repermitting this area for C&D waste, MWA was able to provide better surface-water management, regain airspace lost to settlement, and provide revenue to replace the existing soils cap with a synthetic geocomposite cap system.

Serving All of Central Iowa

MWA’s service area consists of 16 member communities, one county, and six planning-member communities. Planning-member communities (Alleman, Carlisle, Hartford, Mingo, Prairie City, and Sheldahl) are offered MWA programs and facilities but do not have a voting representative on MWA’s Board of Directors. Altogether MWA serves just fewer than 400,000 residents with the MPE Landfill and recycling and waste reduction programs and education. Additionally, 18 counties in central Iowa are included in the expansion area for the Regional Collection Center for Household Hazardous Waste. These communities are served with a mobile collection unit. Total population for these counties is approximately 416,000.

As MWA and MPE Landfill look to the future, environmental stewardship will continue to drive technology and services at a faster pace than ever before. While focusing on environmental protection, employee safety, public health, and financial viability, MWA works hard to ensure MPE Landfill’s continued viability and its role in community service. As a governmental agency required to balance competing interests–public good with private-sector economics and political will with businesslike development, for example–MWA’s mission and vision will continue to guide it to meet the challenges ahead.

SILVER EXCELLENCE AWARD WINNER
Onyx Waste Services/Superior Emerald Park Landfill

Onyx Waste Services/Superior Emerald Park Landfill (EPL) is one of the most recently constructed and technologically engineered sites in the state of Wisconsin. The landfill is located in Muskego, which is in close proximity to major metropolitan areas such as Milwaukee, Racine, and Waukesha.

The 35-ac. landfill site, which is situated on 480 ac., was originally opened in 1994 and began a three-phase expansion in 1996. With the 55-ac. expansion, EPL has a life expectancy of more than 10 years.

The landfill is a zone of saturation, ingradient design featuring a base of bedrock, sand, and 75-125 ft. of native clay soils. Below the clay component of the composite liner, a gradient control system has been constructed. The gradient control system consists of a 6-in. drainage layer with a perforated pipe collection system. The system allows shallow groundwater to be collected from the clay liner above and the clay soils below the gradient control system. The system relieves the uplift pressure on the composite liner and acts as a leak detector.

The clay liner is covered with a 60-mil high-density polyethylene (HDPE) geomembrane liner. A 1-ft. leachate drainage layer and leachate collection pipes are constructed directly above the composite liner.

As cells of EPL are completed, they are capped with a 2-ft. recompacted clay liner, a 40-mil HDPE geomembrane liner, a geosynthetic drainage layer, and a 4.5-ft. layer of general fill and 6 in. of topsoil. Other features of the design include gas extraction wells, sedimentation basins, and biofilter systems.

There has been much thought and discussion about the end use of EPL. The site is already beautifully landscaped and features two ponds at its entrance that regularly attract ducks, geese, and other wildlife. Likely options for the site include a park and nature center, bike and hiking trails, a wildlife habitat, or a game preserve. A secluded area of the site currently serves as a shooting range for local law enforcement training, and that partnership could also be expanded as part of the end-use plan.

Leachate

EPL has a comprehensive, state-of-the-art system that moves leachate downslope through a highly permeable drainage blanket to collection lines, which then transmit the flow to sumps at the lowest base elevation of each phase. From these sumps, the leachate is then pumped out of the landfill to a holding tank and recirculated back into the waste mass or disposed of at a wastewater treatment facility.

The estimated peak leachate generation rate is approximately 25,000 gpd and would occur when the final cell of the landfill is being filled. After that final cell in the expansion is filled and covered with 2 ft. of compacted clay and a 40-mil synthetic geomembrane, the infiltration of water would be reduced. It is estimated that after that final cell is closed, approximately 9,300 gpd of leachate would be produced.

Gas Monitoring and Burning

EPL’s design also incorporated a composite liner and cover system with an active gas extraction system. These controls, along with the very low-permeability soils that surround the site, prevent any significant offsite, subsurface gas migration. Gas monitoring probes are installed around the landfill to monitor for gas migration.

Gas generated by the site is burned off in an onsite flare. The gas collection and control system meets the USEPA New Source Performance Standards for hazardous air pollutants.

Five gas extraction wells, as well as 17 horizontal recirculation lines, which are used to extract LFG when not being used for leachate recirculation, are located at the EPL site. Staff and state and city regulators regularly inspect them.

Other Air-Quality Issues

In addition to LFG, dust, hazardous air pollutants, and exhaust emissions could potentially impact air quality near the site.

EPL has established a program that monitors air quality for suspended particles and controlling dust. Since the program’s inception in 1999, there have been no accedences of air-quality standards.

Odors and Debris Controls

In its continual efforts to be a good neighbor, EPL has a program in place to help control odors and debris coming from the site. As part of its operations, the landfill maintains only a small active area, uses daily cover, and utilizes moveable and stationary screens. Multiple catch fences aid operations on windy days, and a daily pickup of windblown debris helps to maintain aesthetics. This program and ongoing commitment by EPL has resulted in good relationships with its neighboring businesses and residents.

Groundwater Protection

The EPL design limits adverse impact to groundwater quality by including a composite liner with 4 ft. of clay overlain by a 60-mil synthetic geomembrane. This composite liner, in conjunction with the efficient collection and removal of leachate from within the landfill, virtually eliminates infiltration of leachate to the native soils and the water table. A groundwater gradient control system installed beneath the landfill liner relieves groundwater pressure and allows monitoring of the integrity of the liner.

Groundwater monitoring wells at the site are checked semiannually for a variety of contaminants and indicator substances to ensure that any contamination that occurs would be detected and remediated before traveling to a point of groundwater use.

EPL’s design and construction have proven successful in preventing any groundwater impact. To date, there has been no demonstrable impact on groundwater quality as indicated by the semiannual monitoring results.

BRONZE EXCELLENCE AWARD WINNER
Middlesex County Landfill

The Middlesex County Utilities Authority (MCUA), through its Solid Waste Division, operates the Middlesex County Landfill (MCLF), a state-of-the-art sanitary landfill located in East Brunswick, NJ. The landfill opened in February 1992 and is located on a 315-ac. tract surrounded by a bentonite clay slurry cut-off wall that also contains the closed and capped Edgeboro Landfill. The closed facility encompasses approximately 215 ac. inside the slurry cut-off wall area.

Location of Middlesex County Landfill. Click here for larger view

MCLF is a double composite liner system consisting of HDPE liners and clay. It is constructed as a lateral expansion adjacent to the Edgeboro Landfill at two locations with a "piggyback" section over the closed landfill to connect the areas. Eventually the landfill will cover more than 200 ac. of the former landfill site and is presently permitted to reach a maximum height of 165 ft. above mean sea level with an estimated life expectancy until year 2018.

The in-ground bentonite clay slurry cut-off wall is keyed into either the Raritan Fire Clay or the Passaic formation and provides a barrier of the horizontal movement of liquid in the Farrington Sand Formation under the landfill, thereby isolating the site from the surrounding groundwater. The liner system itself is considered state of the art and consists of both clay and geomembrane components.

Owing to the nature of the landfill’s piggyback design, the stability of the closed Edgeboro Landfill is of concern. Potential slope movement due to additional loading from the new landfill is monitored through a series of inclinometers that have been installed along the perimeter of the critical interface areas. Projected life expectancy of MCLF at the current rate of waste placement and cover volumes being used is between 15 and 18 years.

MCLF collects leachate from the 18-in. drainage sand layer on top of a drainage net that is overlying an 80-mil HDPE liner. The leachate is collected in 12-in.-diameter perforated pipes that eventually discharge into a respective primary pump station. The secondary collection layer consists of 18 in. of drainage sand situated between the 80-mil HDPE primary liner and the 60-mil HDPE secondary liner. In this layer, there is a network of 6-in.-diameter perforated pipes that collects any drainage and discharges it into a secondary collection system.

As with most landfills, the generation and control of LFG is of major concern. Both Edgeboro Landfill and MCLF have their own LFG extraction systems. To address this concern, MCUA contracted with National Energy Resource Corporation to construct an LFGTE project. This project consists of a combination of vertical gas wells and horizontal gas collection pipes that presently collect approximately 3,000 scfm. The LFG is transported, along with gas from two other inactive landfills–one capped the other uncapped and also located in Middlesex County via a 6-mi., 16-in.-diameter pipeline–to an LFGTE facility located at the MCUA Wastewater Treatment Plant site. The LFGTE facility was designed to generate a net 16 mW of electrical energy that is utilized by the wastewater treatment facility; any excess power is sold to the power grid of the local utility.

Innovation and Creativity

Typical scale-house transaction

Numerous aspects of MCLF distinguish it from other landfill sites. The unique design of the liner, a piggyback system, has won awards for Fostering Excellence in Engineering Design from both the Consulting Engineers Council of New Jersey and the American Consulting Engineers Council. The LFGTE project won the 2001 USEPA Landfill Methane Outreach Program Project of the Year. In July 1996, SWANA conducted a National Training and Certification Program at MCLF.

Exceptional operational aspects include the use of a sludge-derived product from the MCUA Wastewater Treatment Plant for daily cover and as a component in the topsoil mixing operation; the segregation of recyclable-rich loads that are separated into scrap metal and taken to an outside market; the wood that is ground into another type of alternative daily cover; and the leachate system that discharges directly into a local county trunk sewer, which eliminates the need for storage or recirculation in order to reduce volume.

All of these operations are conducted on a double-lined landfill that is part of a site surrounded by an in-ground bentonite slurry cut-off wall with a minimal amount of operational personnel as compared to facilities similar in size. In addition to typical solid waste activities, MCLF has ventured into show business. On two separate occasions during 2001, crews from 20th Century Fox constructed onsite movie sets for segments of a picture titled Unfaithful, directed by Adrian Lyne and starring Richard Gere and Diane Lane. The landfill was also host to a television crew from NBC that was filming a skit for the Conan O’Brien Anniversary Show.

John Trotti is editor of MSW Management.

MSW - September/October 2002