Fire Training Zone Plume
Several small, unconnected TCE plumes were present in the former Fire Training Zone (FTZ), which is located adjacent to 1st Avenue on property currently owned by the Colorado Golf Association. There were several potential sources for the TCE in the groundwater at the FTZ. TCE likely reached groundwater through pits used for fire-fighting training activities, a former septic leach field, and/or potential solvent releases related to activities at Building 1023 and 1026. TCE appears to have migrated in sand near the base of the alluvial water-bearing zone, into weathered and fractured bedrock.
Based on historical groundwater monitoring data, the plumes are non-mobile and remain isolated from potential migration pathways. The depth to groundwater at the FTZ area ranges from approximately 6 feet below ground surface (bgs) in the upgradient portion of the northern TCE plume to approximately 21 feet bgs where the northern TCE plume occupies an erosional low eroded into the top of the bedrock surface. The depth to bedrock in this area ranges from approximately 5 feet bgs in the upgradient portion of the northern TCE Plume to 39 feet bgs in the erosional low.
The FTZ TCE Plumes are located underneath the Common Ground Golf Course which is currently owned and operated by the Colorado Golf Association. Groundwater in the FTZ is present in the bedrock; the target TCE mass in this area is present within bedrock fractures with little or no overlying saturated alluvium. Treatment of TCE in bedrock was accomplished through two rounds of KMnO4 injection that occurred over a two year period; over 13,150 pounds (by weight) of potassium permanganate (KMnO4) were injected into the bedrock groundwater through 51 injection points.
The overall TCE concentrations and the extent of the localized plumes in bedrock groundwater in the FTZ have been reduced greatly since August 2001. As illustrated in the FTZ Plume Map from July 2018, TCE concentrations in several localized areas in bedrock remain slightly above the site-specific standard of 11 µg/l.