TO 0009 Environmental Cleanup Plan
Section 2 - Site Conditions
2.1 - Site Description and History
AOC 55 consists of potential contaminated source areas associated with landfilling of non-hazardous waste. These areas have been identified by the presence of metal debris exposed during a previous flooding events.
The site was used as a landfill and is located south of Tenberg Drive and both east and west of Salado Creek. It is approximately 3.6 acres in size and contains approximately 32,700 cubic yards of waste material. Initial site surveys indicate that the waste consist of ash, metal debris, and trash, to include UXO, from the World War I era.
Further background information regarding the location, size, and known historical use of the site is included in the Environmental Encyclopedia (Volume 1-3, AOC 55).
2.2 - Geology and Hydrogeology
The Trinity and Frio soils predominate AOC 55, although there is significant evidence that soils in the area were removed to allow burial of waste material(s). The Trinity and Frio soils are frequently subjected to flooding, and make up the main channel soils for Salado Creek, which is located on the western flank of the site. Trinity soils are 3 to 5 feet deep and composed of clayey to gravely loam. Frio soils are a dark grayish-brown clay loam, 3 to 4 feet deep. Detailed descriptions of all CSSA soil types are given in the CSSA Environmental Encyclopedia (Volume 1-1, Background Information Report, Soils and Geology).
AOC 55 is sited over the Lower Glen Rose (LGR) limestone. The LGR formation is a massive, fossiliferous, vuggy limestone that grades upward into thin beds of limestone, marl, and shale; it is estimated to be 300 feet thick beneath CSSA. The LGR is underlain by the Bexar Shale facies of the Hensell Sand, which is estimated to be from 60 to 150 feet thick under the CSSA area. The Bexar Shale consists of silty dolomite, marl, calcareous shale, and shaley limestone. The geologic strata dip approximately 10 to 12 degrees to the south-southeast at CSSA.
Surface topography at and in the vicinity of AOC 55 slopes gently (less than 2 percent grade) toward Salado Creek, so run-off is generally toward the southeast and southwest.
The middle Trinity aquifer is unconfined and functions as the primary source of groundwater at CSSA. It consists of LGR Limestone, Bexar Shale, and Cow Creek Limestone. The middle Trinity aquifer is separated from the lower Trinity aquifer by the Hammett Shale, which is an aquitard and not considered to be part of either the middle or lower Trinity aquifers. The LGR Limestone outcrops north of CSSA along Cibolo Creek and within the central and southwest portions of CSSA. As such, principal recharge into the middle Trinity aquifer is via precipitation infiltration at outcrops. At CSSA, the Bexar Shale is interpreted as a confining layer, except where it is fractured and faulted, allowing vertical flow from the up-dip Cow Creek Limestone into the overlying, but down-dip LGR. Fractures and faults within the Bexar Shale are thought to allow hydraulic communication between the LGR and Cow Creek Limestone. (Background Information Report, Volume 1-1 Environmental Encyclopedia).