Preventing The Problem Of Stormwater Pollution

One of the most significant responsibilities of a landfill owner or operator is to protect their community's groundwater. Although leachate collection and treatment often receives the lion's share of attention, managing the site's stormwater is equally important.

Working with its state agency and a consultant, one of the nation's smaller landfills has tackled this job in a big way.

The Magnolia Sanitary Landfill in Summerdale, Ala., is owned and op-erated by the Baldwin County Board of Commissioners. The Alabama De-partment of Environmental Man-agement (ADEM) permit requires the county to prepare and implement a best management practices plan (BMP) to prevent the problem of contaminated stormwater coming from the landfill.

The county hired BCM Engineers Inc. to prepare the BMP plan, while the Baldwin County Environmental Management Department, which op-erates the landfill, will oversee the plan's implementation.

"Developing a workable plan is a process of give and take on both sides," said Tom Granger, BCM's project manager for the Magnolia Landfill. "Each site's topography and activities are different."

First on the list of projects is the walk-through inspection where po-tential sources of stormwater pollution are identified.

Common sources include the e-quipment maintenance area, where there is potential for oil, grease and hydraulic fluid spills; satellite fueling sites; loose trash; side slopes; and disturbed ground.

In conjunction with the Magnolia Landfill walk-through, a facility map was prepared to show the overall layout of the landfill. This included proposed stormwater collection ponds and landfill disposal cells in the design to upgrade the landfill to comply with Subtitle D.

Fortunately, the site is well-located, said Steve Tapia, deputy director of the Baldwin County Environment-al Management Department. "Our groundwater monitoring over the years has shown we have a good site in terms of its impermeability," he noted.

"As far as the surface water goes, ADEM doesn't require us to monitor our ditches during storms because nothing was coming off. While we are digging our Subtitle D facilities, we are still permitted to expand vertically," said Tapia.

The Best Management Plan Magnolia's BMP plan incorporates efficient administrative practices, general management practices and management practices for specific areas of the landfill, such as active and inactive cells and stormwater ditches.

The administrative practices section details each employee's role to help implement the plan, including the board of directors and landfill director. Granger says it is essential that upper management support the plan.

"The people who work at the site need to know about potential sources of pollutants and must have the authority and the budget to im-plement pollution prevention procedures," he said.

The landfill director must provide adequate staff training for all landfill workers. "We have decided to put everybody through landfill management operations training," said Tapia.

To reduce or eliminate potential sources of stormwater pollutants, the following general practices were suggested: * Store Magnolia's used oil in a designated storage tank.

* Provide sediment and erosion control structures to prevent or control stormwater pollution by soil particles in order to maintain compliance with the suspended solids limitation stated on the permit. Silt fencing and hay bales may be used for this purpose.

* Wash all vehicles and equipment within the designated washing area so the residual wash water can be collected and treated by the leachate collection and removal (LCR) system.

* Operate the satellite fueling facilities located throughout the landfill in accordance with 40 CFR Part 112 of the federal regulations. This in-cludes placing secondary containment around satellite fuel tanks to prevent migration of any released fuel to the environment from a leak or spill.

In Magnolia's case, many of the practices were already in place, but the operators have begun making improvements. "We have to install a bigger wash facility for our equipment and will attach a water recycling plant to it to take out the solid waste," Tapia said.

"We will continue to use portable fuel tanks, and we are in the process of installing catch pans under them," he said.

The landfill's BMP plan includes practices designed to reduce the potential sources of pollution in the key areas of the landfill - active and inactive cells, stormwater ditches, the LCR and stormwater collection ponds.

Under active landfill cells, for ex-ample, the plan requires diversionary structures such as ditches and berms, and equipment to be in-stalled as needed to prevent storm-water from flowing onto the active portion of the landfill from adjacent areas. "This is very important," Granger explained. "Once stormwater permeates the active cell, the po-tential for contamination greatly increases," he said.

Similarly, silt fencing, hay bales and/or grassing must be placed around the perimeter working faces of the landfill to prevent transport of eroded soils. "When rain falls on steep side slopes of exposed dirt, there is great potential for erosion and the washing of mud and suspended solids into nearby receiving streams," said Granger.

"We want to limit the slope, plant grass on the slope if possible and use hay bales and silt fences to slow the water flow and trap the sediment," he said.

Frequent Inspections Magnolia's BMP plan states that stormwater on an active cell or infiltrating through the daily or intermediate cover becomes leachate. It must be collected by the LCR and conveyed to the leachate treatment system to be treated before discharge.

"The stormwater permit is only for surface water run-off, which must be kept separate from leachate - a de-tail to which the state of Alabama pays careful attention," noted Gran-ger.

The LCR valves and liner must be inspected weekly and evaluated on the inspection log. Magnolia will treat leachate in a constructed wetland setting.

Stormwater collection ponds are being designed for the Magnolia Landfill with varying levels of operation. The BMP plan requires daily inspections to ensure that the controlled discharge level in each pond (that is, lower gate most opened) will provide enough detention time to remove suspended solids.

The BMP plan requires daily in-spection for oil sheen or solid waste, and specifies that the proper corrective actions should be noted. It also calls for periodic inspection of bottom elevations of the retention ponds to ensure that there is not a significant reduction in detention capacity due to a build-up of suspended solids.

An inspection log sheet was created with the following criteria: cover soil, grassing/seeding, stormwater ponds, stormwater ditches, leachate collection system and ponds, erosion control structures and storage of po-tential contaminants. Inspectors must note the general condition, de-ficiencies and required maintenance and repairs on the log sheet.

The BMP plan was completed last May. According to the regulations, it may only be modified if there is a stormwater pollution problem. Granger and Tapia agree that best management practices will need to change with the times. "You always have to make improvements, especially as you add different materials,. For instance, we are getting a lot of lead-acid batteries which we have to accommodate," Tapia said.

A BMP can be the first step toward solving the stormwater pollution prevention problem.