Nov 20, 2014

Perchlorate Plumes at AU & Sibley Still Exceed Federal Advisory Level

The quarterly sampling of the wells in front of Kreeger Hall on American University and the Sibley Hospital sump was concluded in September.  The September quarterly sampling detected perchlorate concentrations above 15 parts per billion (ppb) at MW-44 and PZ-4D on AU’s campus ... The wells PZ-4S&D (sampled since 2006), MW-44, and MW-45S&D in front of Kreeger Hall at AU all represent different depths to get vertical delineation of the areas’ groundwater ... 
MW-44 was installed in March 2012.  Its results consistently range from 33 to 50 ppb.  MW-44 is a deeper well.  The groundwater flow at this depth is an order of magnitude less than PZ-4S, which means that the groundwater flow at PZ-4S may be around a foot a day, compared to an inch a day at MW-44.  This means that the contamination seen at MW-44 may take longer to flush out over time ... 
MW-21 and MW-22 are shallow wells along MacArthur Boulevard, and the Sibley sump is in the bottom of the elevator shaft at Sibley Hospital ... When MW-22 was first sampled, the perchlorate concentrations were around 5-10 ppb.  The most recent sampling results in December 2013 and June 2014 detected perchlorate concentrations at 17 and 25 ppb.
Todd Beckwith, USACE
RAB Meeting
November 18, 2014

 
The other new well was placed in the road on Rockwood Parkway, near the tip of the Rockwood Parkway "island."  This multi-port well will further evaluate if there is any connection between the American University perchlorate plume and the plume detected in the vicinity of Sibley Hospital ... The Groundwater RI [Remedial Investigation] report will provide a summary of the groundwater investigation to include ... the nature and extent of contamination ... If the HHRA [Human Health Risk Assessment] does determine that any of the COPCs [Chemicals of Potential Concern] pose an unacceptable risk, a Feasibility Study will be performed to evaluate alternatives to address the unacceptable risk and identify Remedial Action objectives.
 
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