Lawton Sanitary Landfill

Lawton Sanitary Landfill

Location: Lawton, Okla.

Client: City of Lawton

Burns & McDonnell has provided a variety of professional consulting services for the city of Lawton's Sanitary Landfill. The landfill is located in Comanche County, Okla., and receives approximately 500 tons of solid waste per day. The Subtitle D portion of the landfill is approximately 160 acres.

The waste disposed at the site is primarily municipal solid waste from private haulers and from city collection. The pre-Subtitle D portion of the landfill contains an area that was used exclusively for disposal of waste from a Goodyear rubber plant.

Investigations

Burns & McDonnell conducted a hydrogeologic investigation at the city’s existing landfill site as part of permitting effort for the new Subtitle D landfill expansion. All field investigation activities, including the installation of piezometers, monitoring wells, soil borings and test pits were supervised by Burns & McDonnell personnel. A final hydrogeologic report was prepared and submitted to the Oklahoma Department of Environmental Quality (ODEQ) as part of the landfill permit application.

As a result of the investigation, a new groundwater monitoring system was designed and additional wells were installed. In addition, a gravity-flow underdrain system consisting of drainage media and high density polyethylene pipe was designed and constructed below the liner system. This task became necessary when the hydrogeologic investigation located an isolated zone of perched water at an elevation just below the proposed composite liner system. The underdrain was completed in an effort to relieve any hydrostatic pressure that the zone might create on the liner system.

Permitting and Design

Burns & McDonnell was hired by the City of Lawton to provide solid waste design and permitting services related to its existing landfill and to a new 160-acre landfill. The principal features included a composite liner system, leachate collection and treatment, hydrogeologic investigation, storm water management, methane gas management, and other requirements established under the EPA Subtitle D Regulations.

The project involved the design of a 40-acre expansion of the existing sanitary landfill to meet new state and federal solid waste regulations effective Oct. 9, 1993. The design allowed the city to continue operations at its existing landfill site in compliance with all regulations for an additional eight to 10 years. The expansion included the installation of a compacted clay liner overlain by a 60 mil high density polyethylene liner, complete leachate collection and treatment system, and a groundwater monitoring program.

Permits for these facilities were obtained from the Oklahoma State Department of Health. In addition, NPDES storm water design, permitting and pollution prevention plans were prepared for the existing and proposed sanitary landfills.

The design for the 40-acre area met all state and federal Subtitle D regulations and included a composite liner system, leachate collection and treatment systems, final cap system, operations plans, and closure/post-closure plans. The final design included three 10- to 15-acre cells to be constructed in three phases. Burns & McDonnell also prepared bid specifications and drawings for the city’s bidding process and reviewed all bids for technical compliance and financial aptitude.

In addition to the solid waste permits, Burns & McDonnell prepared NPDES stormwater and wastewater permits for surface water runoff and the leachate evaporation lagoon, respectively.

Feasibility Study

Burns & McDonnell provided a feasibility study of a compost program for the city's yard waste. The feasibility study included an evaluation of site criteria, an analysis of landfill airspace, savings, a survey of collection and transportation requirements, and an operations and maintenance cost estimate.

The study also examined the utilization of yard waste paper bags, as opposed to bulk collection, as a means to improve the efficiency of yard waste collection.

Medium level composting technology was selected as the most feasible method for the city's yard waste program because of both time and site restraints. The site restraints made it imperative to be able to remove stable compost product from the site by the time the next year's deposition occurred. Medium level composting is a technique of turning the compost windrows so that mixing, aeration, control of excess heat, and release of metabolic wastes (CO2 and H2O) are accomplished for optimum decomposition of the material.

Burns & McDonnell provided design requirements for the medium level technology compost facility that included windrow, curing, staging, screening, finished product areas and a leachate holding basin. The compost pad design requirements followed current Oklahoma regulations. The most economically feasible design alternative consisted of a 2-foot-thick recompacted clay liner overlaid with 6 inches of 3/4-inch crushed limestone rock covered with 6 inches of quarry fines.

Compliance Monitoring

As part of the effort to bring the landfill into compliance with Subtitle D regulations, Burns & McDonnell prepared a comprehensive groundwater monitoring plan. The effort involved evaluating the existing groundwater monitoring network, identifying components of the network which were not in compliance, and overseeing construction of new groundwater monitoring wells.

Burns & McDonnell prepared groundwater monitoring and gas monitoring plans to comply with all state and federal regulations. Both plans included background information relevant to monitoring system design, operational and monitoring procedures, reporting requirements, and appropriate reporting forms. Burns & McDonnell also prepared a stormwater pollution prevention plan (SWPPP) for the site as a requirement of its National Pollution Discharge Elimination System (NPDES) stormwater permit.

Gas

Burns & McDonnell prepared a gas monitoring plan and designed the associated gas monitoring system for the Lawton Sanitary Landfill. Gas monitoring probes were spaced at approximately 500 feet at the property line to adequately monitor any gas concentrations. The plan also included monitoring to be completed in all structures located on the site to comply with ODEQ regulations.

Construction Services

Burns & McDonnell prepared construction bid documents for construction of the first cell in the new Subtitle D area. Burns & McDonnell also completed an evaluation of construction bid submittals. All bids were evaluated for technical approach and consistency with design, financial proposal, and subcontractor arrangements. Each contractor was also evaluated separately on the basis of representative experience and financial stability.

Closure

As part of the permit application report, Burns & McDonnell prepared closure and post-closure plans for the Lawton Sanitary Landfill in accordance to ODEQ guidelines. The closure plan outlined closure sequencing, the final cap system, additional monitoring systems, a closure cost estimate, and notification requirements. The post-closure plan included descriptions of post-closure activities such as cap repair, vegetative repair, environmental monitoring, and a post-closure cost estimate and has been updated on an annual basis.