National Water-Quality Assessment (NAWQA) Program - South Platte River Basin
Two groundwater studies were conducted in South Platte alluvial aquifer (groundwater adjacent to the stream) in the Denver Metropolitan area: 1) a large-scale study of the effects of urban land use on groundwater quality, and 2) a small-scale study nested within the land use study on the transport of volatile organic compounds (VOCs) in the alluvial aquifer to the South Platte River.
Effects of Urban Land Use on Groundwater Quality
Provide a broad overview of the quality of groundwater in the Denver Metropolitan area by sampling recently recharged groundwater in the South Platte alluvial aquifer.
Relate observed groundwater quality to overlying land use.
Sampled 30 existing wells randomly distributed throughout the South Platte alluvial aquifer in the Denver Metropolitan area.
Subdivided wells into three urban land-use categories: commercial, residential, and industrial.
July through September 1993
Major ions, nutrients, pesticides, (VOCs), trace elements, and dissolved organic compounds (DOC).
The pesticides atrazine, prometon, and simazine were frequently detected at low concentrations in the shallow groundwater.
Three of the 30 samples of shallow alluvial groundwater had nitrate concentrations that exceeded the U.S. Environmental Protection Agency 10 mg/L drinking water standard; however, alluvial groundwater in 1998 was not used as drinking water sources in the Denver area.
VOCs, derived from gasoline and cleaning solvents, were detected in 86 percent of shallow groundwater and highest concentrations occurred in samples from industrial settings. The most frequently detected VOC was the gasoline additive methyl tert-butyl ether (MTBE).
Transport of VOCs in the Urban Alluvial Aquifer to the South Platte River.
Examine degradation of VOCs in the aquifer and estimate fluxes to the river.
Determine persistence of these compounds in the South Platte River.
Ground water and surface water were sampled.