<a href="http://www.flickr.com/photos/rdecom/4688582698/" title="Army continues clean-up efforts at APG site by RDECOM, on Flickr"><img src="http://farm2.static.flickr.com/1290/4688582698_ba4d1e520c_o.jpg" width="250" align="right" hspace="10" height="224" alt="Army continues clean-up efforts at APG site" /></a>ABERDEEN PROVING GROUND, Md. -- Aberdeen Proving Ground's efforts to clean up a contaminated site at New O-Field will achieve the complicated task in an environmentally-friendly way. After considering several options, the installation has chosen a cleanup approach that will remediate the site while being mindful of the sensitive natural environment.
New O-Field is a hazardous waste site being investigated and remediated by the APG Directorate of Public Works Installation Restoration Program under a Federal Facility Agreement with the EPA. New O-Field was active from the 1950s through the late 1970s as a destruction, demilitarization, disposal and training area. It consists of an open field containing trenches, a pile of contaminated soil and a pond created by past cleanup efforts. Pollution from these areas near Watson Creek eventually flows to the Chesapeake Bay via the Gunpowder River.
"The New O-Field project team developed a well thought out remedial action using a combination of containment methods and biological treatment to produce a safe and effective plan of action with the least impact to the ecology," said Frank Vavra of the Environmental Protection Agency.
Multiple investigations of New O-Field, which started as early as 1993, identified several environmental concerns requiring remediation. These include hazards to human health and wildlife from buried munitions and chemical warfare materiel; metals and white phosphorus (in pond sediment and stockpiled soil); and metals and solvents seeping into the pond from groundwater.
The draft Feasibility Study for New O-Field originally identified seven active remediation alternatives that included combinations of capping or covering the buried waste, treating groundwater in place or via a treatment wetland, filling in the pond and full excavation. Preparation of the final Feasibility Study of the site revealed a separate eighth alternative that also combined several technologies to create an improved remedial solution. The eighth alternative includes:
Constructing a wetland buffer and bio-beneficial sediment cover. Extracting groundwater and re-injecting it with special amendments to create a bio-enhancement zone for groundwater between the buried waste and the pond. Constructing permeable soil cover over the contaminated surface soil and buried waste utilizing the soil stockpile and other soils.
<a href="http://www.flickr.com/photos/rdecom/4688582694/" title="Army continues clean-up efforts at APG site by RDECOM, on Flickr"><img src="http://farm5.static.flickr.com/4037/4688582694_a39e03b65c_o.jpg" width="400" align="left" hspace="10" height="196" alt="Army continues clean-up efforts at APG site" /></a>Monitoring and maintaining the site over the long term to ensure remedial technologies are working. Implementing land use controls to prevent any future use of the site that is incompatible with the remedy.
"The New O-Field site presented human health, environmental and immediate safety concerns," says Elisabeth Green, Ph.D., who works in the Federal Facilities Division of the Maryland Department of the Environment. "By working cooperatively with the state, APG is able to implement an innovative response to achieve a level of protection equal to or greater than strict Applicable or Relevant and Appropriate Requirements compliance, and was cost effective considering the unique nature and condition of the site."
"Our approach was based in part on using the natural features of the site as an advantage for the remediation," said Mike Ciarlo, the Project Manager and Senior Scientist for EA Engineering, Science and Technology, Inc., APG's contractor on the project. "Using natural processes can produce a remedy that is more sustainable, is more efficient and provides more habitat."
The approach offers a "green" remediation alternative using natural materials and sustainable natural processes to advantage. The wetland buffer and bio-beneficial sediment cover of sand mixed with a carbon source will restore the wetland and pond site by preventing exposures to chemicals in the sediment and addressing chemicals in groundwater that have already moved beyond the groundwater treatment zone. The sediment cover eliminates risks from white phosphorus and chemicals in sediment and water by preventing exposures and creating conditions that help break down or sequester chemicals. The planned addition of native wetland plants will not only restore habitat, but will add carbon to the site over time that will enhance remedial conditions by acting as a carbon sink through a self-sustaining natural process.
The chitin-based carbon source recommended to create the wetland buffer and sediment cover is made of crushed crab shells. Using the shells is ideal because it helps to control pH, provides nutrients for plants, and provides a food source for bacteria that break down contamination.
The bio-enhancement zone aspect involves injecting a food source to promote growth of naturally occurring bacteria that help remediate groundwater. The naturally occurring bacteria create conditions that break down chemicals, such as solvents, and lock metals in forms that are less soluble and less toxic. This minimizes risks from chemicals in groundwater by treating it before it enters the wetland and pond area.
The purpose of the permeable cover that will be constructed over the waste burial site is to eliminate exposure to the buried hazards and wastes. The cover will be planted, and will control run-off and soil erosion into the pond. The permeable cover allows water to infiltrate to the buried waste. While water promotes munitions corrosion which decreases their explosive potential, it also helps break down most chemical warfare agents into relatively non-toxic chemicals through hydrolysis.
"The components of the remediation work together to be more effective," said Cindy Powels, an environmental engineer with the APG DPW. "The permeable cover, groundwater bio-enhancement, the wetland buffer and the sediment cover are all complementary. The cover allows water to break down waste, which is further treated through bio-enhancement and further polished by the wetland buffer, and the pond sediment cover. Chemicals in groundwater that have moved beyond the bio-enhancement zone are still addressed in the planted wetland buffer and sediment cover in the deeper areas of the pond."
Implementation of the plan to remediate the New O-Field pond area began on Nov. 30, 2009, with the construction of three temporary causeways into the pond, which accommodated a 110-foot, long-reach conveyor with an "elephant trunk" used to install 3,500 tons of the sand mix containing 0.25% chitin-based carbon source. The pond wetland buffer was initially lined with geo-textile fabric prior to the sand mix application to minimize potential wildlife exposure in the shallower areas. Bio-logs were placed between the wetland buffer and the open water areas of the pond by hand to further establish a sustainable remedial activity zone between the pond and the permeable capped landfill.
Both the groundwater remediation and pond construction plans were presented to the Army, the Environmental Protection Agency and the Maryland Department of the Environment. Approvals were received and initial work began back in September 2009. Construction of the permeable cover and planting of the wetland are planned for summer 2010. Upon remedial construction completion, the next step in the project is to conduct groundwater monitoring in the spring of 2010 and establish land use controls. Periodic monitoring will establish and track the effectiveness of the implemented design and allow any necessary modifications to be made.
"The work we did last fall and over the hard winter held up beautifully" said Powels. "We're excited about wrapping up the construction phase and getting everything in order for the next phase of the project."
Aberdeen Proving Ground is taking a sustainable approach to cleaning up New O-Field, officials said. When the project is complete, the final cost is expected to be half of the lowest estimate for the other remediation alternatives. This project is an example of utilizing a green remedial approach to protect the Chesapeake Bay, its tributaries, and the surrounding environment here at APG, and is a tribute to the collaborative efforts of all participants in the process.
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