Here’s the executive summary from the report:
This report documents the work, findings, analysis, and recommendations of the Colorado Geological Survey (CGS) in executing the scope of work commissioned by El Paso County, through the Groundwater Study Committee, established in reference to Resolution No. 09‐202. The subject of this report is the groundwater quality of the alluvial aquifer within the Upper Black Squirrel Creek (UBSC) basin (Figure 1.1). The Phase 1 study objectives are to characterize the current groundwater quality in the alluvial aquifer and determine whether there is a correlation between existing and future land uses and groundwater quality. The scope of work for Phase 1 was finalized in January 2010, and the County contracted with CGS to perform the work.
The current study is limited to evaluation of existing water quality data for groundwater in the alluvial aquifer system of the Upper Black Squirrel Creek Designated Groundwater basin (UBSC basin) of east‐central El Paso County, Colorado. As part of the study a literature review identified 34 relevant publications and an annotated bibliography was prepared. Previous published studies indicated that the groundwater was of good quality, but identified nitrate as a contaminant of concern. Water quality data was acquired from a variety of public sources (county, state, and federal) and study cooperators. The data represent 150 samples collected from 72 different wells between 1954 and 2009. Samples collected for water quality analysis within the study area have a limited spatial and temporal distribution. Approximately 80% of the data were collected in the 1980s and 1990s, and the great majority of wells are within three miles of the Ellicott Highway. One of the most important characteristics of this data is the lack of multiple samples from individual locations. The northern and western portions of the UBSC basin where rapid development has occurred and is expected to continue are not represented in the data.
Groundwater chemical analysis data for inorganic compounds, total dissolved solids (TDS), nitrate, metals, organic compounds, and radionuclides were evaluated to characterize the UBSC basin alluvial aquifer’s water quality. The groundwater sample data indicate that, where sampled, the water is generally acceptable with respect to drinking water standards; of moderate hardness; and free of pesticides, herbicides, and regulated organic contaminants. At certain times and locations, some water quality parameters were detected at concentrations in violation of primary and secondary drinking water standards including: arsenic, nitrate, pH, TDS, sulfate, and iron. Nitrate values greater than 5.0 mg/L are common in the basin, and suggest that the alluvial water quality has been influenced by sources of nutrient loading.
No clear relationship between land uses and groundwater quality was evident from the available data. Existing UBSC basin land uses evaluated include residential, agricultural, urban, commercial, industrial, military, and unregulated industrial waste disposal. Elevated nitrate concentrations are distributed over parcels associated with residential, dry land farming/grazing, and irrigated agriculture, suggesting localized sources rather than being impacted from categorical land use. Groundwater quality data are lacking in the northwest portion of the basin where the majority of the development is occurring. Consequently, information regarding nitrate concentrations in areas with higher density ISDSs is missing. Elevated TDS values are associated with both dryland farming/grazing land and rural residential land use. Potential contaminant sources associated with future land uses have been summarized in Table 5.1. Anticipated future land uses within the basin are a continuation and expansion of current land uses, primarily consisting of residential development in urban, rural residential and rural development densities with accompanying commercial development. Figure 5.2 summarizes activity nodes and transportation corridors where future development is expected to be concentrated.
Due to the spatial and temporal limitations of the compiled water quality data, this study was only partially successful in meeting the objectives established by the study committee. Unfortunately, there is no groundwater quality data available in the northwest portion of the basin, where urban land uses and ISDSs are concentrated and continued development is expected.
Decision makers in El Paso County attempting to assess the vulnerability of the groundwater resource currently lack a complete understanding of the hydrogeology of the aquifer system and the associated anthropogenic effects controlling the source, transport, and fate of potential contaminants. To address this gap, we recommend implementing a Phase 2 investigation focusing on refining our understanding of the groundwater flow system and acquiring the water quality data needed to support and scientifically defend land use planning decisions.
More coverage from The Colorado Springs Gazette (R. Scott Rappold):
The Colorado Geological Survey recently analyzed records of water quality samples from 1954 to 2009, a $53,000 project initiated by county commissioners to help guide land-use decisions in the basin. More than half of the water samples showed nitrate levels of 5 milligrams per liter or higher. That’s below the federal drinking water standard of 10, but the study’s author said it is still higher than it should be given the natural conditions, in the 2 to 3 milligrams per liter range.
“Five is just higher than one would expect in a native groundwater environment. It suggests there are some human influences on the increased concentrations,” said hydrogeologist Ralf Topper.
Nitrates are a by-product of fertilizer, which can get into the aquifer as runoff from farm fields and cattle pens. They can also come from the breakdown of human waste in septic systems…
Public meeting on groundwater study
El Paso County’s Groundwater Quality Study Committee will hold a public meeting 6-8 p.m. Monday in the Falcon High School cafeteria, 10255 Lambert Road in Falcon. Members will present information on the recently completed study of groundwater quality in the alluvial aquifer of the Upper Black Squirrel Creek Basin.
More groundwater coverage here and here.