|In September 1944 during a rail shipment of mustard (H) from Black Hills Ordnance Depot, South Dakota, to Rocky Mountain Arsenal, Colorado, three 55 gallon drums of Mustard (H) chemical agent were discovered leaking. Personnel dispatched from Edgewood Arsenal to assess the damaged drums decided to destroy the remaining liquid Mustard. Railroad workers dug a pit (four feet wide, eight feet long, and six and half feet deep) for the disposal of the liquid mustard on the Union Pacific right of way. The liquid mustard was then poured into the pit and neutralized with 450 pounds of calcium bleach, 200 gallons of water, and 10 gallons of decontaminating agent, non-corrosive. The pit was filled with alternating layers of soil and bleach and then marked with a sign that read "POISON."
The two contaminated rail cars were removed from the track and decontaminated at the Marysville freight yard, using decontaminating agent and kerosene. The potentially contaminated railroad tracks and ground areas were washed with decontaminating agent or covered with chloride of lime. Documentation exists confirming that three empty 55-gallon drums were transferred to Pine Bluff Arsenal.
A site visit was conducted by the US Army Corps of Engineers in July of 1992, with a second visit in June 1993. An Archive Search Report was completed in August 1993. Although the exact location of the burial pit could not be verified due to the removal of the marking signs, the location has been narrowed down to about a 500 foot strip along the northeast side of the track. There was one spot within this strip with stressed vegetation.
A memorandum dated 30 September 1944 included in the August 1993 report stated that the decontamination site was approximately 3 miles north of Marysville near Mile Post 116. The property is still owned by Union Pacific Railroad. No visual evidence of OEW/CWM was observed by CEMRK personnel during 7-92.
KDHE completed an Initial Site Screening (ISS) in April 2003 and recommended further investigation to identify and document the location of the pit, and sampling to determine if any untreated mustard or potentially harmful chemicals resulting from the treatment process remain at the site. KDHE then completed a Site Reconnaissance and Evaluation (SRE) in March 2004 and found no release or threat of release of hazardous substances, pollutants, or contaminates to ground water or soils.
USACE conducted additional investigations of the site. A March 2004-Historical Photographic Analysis Report prepared by TEC as part of the RCWM Scoping and Security Study confirmed potential burial area ground scars. A July 2006 site visit as part of the Technical Project Plan meeting attended by USACE, KDHE and UP Railroad further narrowed the potential location of the burial pit to two areas. Geophysical surveys of the areas (2007) identified anomalies; these were confirmed to be non-military debris. Three additional areas of interest were identified during the site reconnaissance. However, laboratory analysis of soil samples collected at the five identified areas did not detect any contaminants of concern.
EPA’s contractor performed a site reconnaissance in 2010 during which they interviewed longtime residents familiar with the area; none could remember seeing evidence of the disposal activities. An Abbreviated Preliminary Assessment followed in 2011; samples were collected from four Washington County RWD#1 wells located between 0.8 and 1.3 miles southeast (downgradient) from the site. No volatile organic compounds or mustard agent breakdown products were detected in the groundwater samples. The APA report recommended no further investigation of the site.
Investigations to date have not detected a release to the environment and it is possible that the Army’s response action in 1944 resulted in complete destruction of the mustard agent. It is noted, however, that the burial pit has not been located.