The U.S. EPA has found that a simple, inexpensive rooftop solar panel can provide enough power to run a fan and remove toxic fumes from homes sitting on contaminated ground. The EPA gave solar-powered venting a test run on several homes earlier this year, in a Superfund action aimed at tricholoroethene (TCE) vapors in a Grand Prairie, Texas neighborhood. The pollution had been traced to a site occupied by the now-bankrupt Delfasco Forge company.
Compared to conventional remediation that involves weeks, months or even years of work along with a potentially huge carbon footprint for transporting or capping soil, the solar-powered exhaust systems took mere hours to install and resulted in an immediate 95% reduction in TCE vapors within the homes. The EPA plans to extend the program this fall to other homes affected by the Delfasco site.
The Delfasco Forge Site
According to the Dallas News, the Delfasco Forge company went bankrupt in August 2008, after the EPA found excess levels of TCE in several homes near the property and ordered a clean-up. Among its other uses, TCE is an industrial de-greaser with short term exposure effects that include damage to the nervous system, liver and lungs. Long term exposure is considered a likely carcinogen. The company had been cooperating with EPA to delineate the plume of contaminated groundwater coming from the site since 2002, but bankruptcy threw a monkey wrench into the prospects for a conventional remediation.
TCE at the Delfasco Forge Site
Cleaning up TCE groundwater contamination is a notoriously expensive, drawn-out process. Sometimes the only option is to allow the vapors to dissipate over time, which in the case of the Delfasco site is expected to take 30 years. The EPA’s investigation revealed that the groundwater contamination covers approximately 65 acres occupied by 500 homes and several businesses, underscoring the need for quick action. With time of essence, last winter the EPA identified the heart of the plume and focused on the homes in that area. Most were “pier and beam” structures with a crawlspace, a configuration that lends itself to preventing TCE buildup indoors simply by venting the air from the crawlspace.
The Solar-Powered TCE Cleanup
To date, the EPA has installed commercially available fans and small rooftop solar units on four homes that were found to have the highest concentration of TCE. The systems were up and running in all four homes within two days. Aside from labor and administrative costs, the equipment cost about $1,000 for four fans, solar panels, and back-up batteries. Immediately after the fans went to work, TCE levels in the homes dropped by 95%. The EPA plans to continue sampling and offering the systems to any other homes in the contaminated area that exceed action levels for TCE.
Solar Power and Sustainable Cleanup
Homes that are build on slabs will be costlier to remediate than the pier-and-beam homes because they require a more powerful fan and a subsurface exhaust system. Either way, the use of an in-place, more sustainable remediation process helps to avoid the high cost and carbon footprint of conventional approaches such as abandoning or demolishing buildings on the site, capping off the site, or excavating it. Other examples of the growing trend toward sustainable remediation are the use of brownfields to grow biofuel crops or other plants that can absorb contaminants – including radioactive material – for proper disposal. Researchers are also experimenting vitamin b12 as a way to stimulate bacteria that can naturally remediate TCE and other contaminants in place, without the need for excavating and transporting soil.
Image: Solar panels at Wayne National Forest on flickr.com.
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