Provide a broad overview of the quality of ground water in the Denver Metropolitan area by sampling recently recharged ground water in the South Platte alluvial aquifer.

Relate observed ground-water 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 ground water.

Three of the 30 samples of shallow alluvial ground water had nitrate concentrations that exceeded the U.S. Environmental Protection Agency 10 mg/L drinking water standard; however, alluvial ground water 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 ground water 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.

Study the transport of volatile organic compounds (VOCs) from a known VOC contaminant source to its discharge 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.

Monitoring wells were installed and sampled along flow paths (plume) of known VOC contaminant sources to its discharge to the South Platte River. Wells were nested and completed at multiple depths.

Ground water and surface water were sampled.

Sampled two rounds in 1994, one round in 1995, and one round in 1996.

Major ions, nutrients, dissolved gasses, VOCs, stable isotopes of carbon, and dissolved organic carbon (DOC).

The gasoline additive MTBE was not readily degraded in the alluvial aquifer.