Project Summary

Location: Denver, Colorado
Clients: Hartwig & Assoc. for CDOT
Contract Value: $38,000

RMC conducted to supplement a Phase I study in connection with the preconstruction and redevelopment of two bridges in the City and County of Denver: the U.S. Highway 6 (6th Avenue) and I-25 Bridge and 6th Avenue and Burlington Northern Santa Fe (BNSF) Railroad Bridge. All work was performed within the Colorado Department of Transportation (CDOT) right-of-way.

Phase II ESA Tasks

  • Prepared Work Plan and Safety and Health Plan
  • Drilled two boreholes at each bridge site using hollow-stem auger and a 5-foot split-spoon sampler
  • Collected three soils samples from each borehole for laboratory analysis
  • Installed temporary wells in each borehole and collected
  • Prepared letter report

Phase II Results

  • No environmental concerns were identified in the soil at the BNSF bridge.
  • 4,4-DDE and 4,4-DDT were identified in the soil from the 6th Avenue/I-25 bridge location at concentrations exceeding the residential soil screening levels. No special handling of this soil is required if it remains on site.
  • Groundwater at the BNSF bridge location exceeded water quality standards for total arsenic, cadmium, and lead, as well as total suspended solids.
  • Groundwater at the 6th Avenue/I-25 bridge location only exceeded groundwater standards for total suspended solids.
  • If dewatering is required during bridge replacement, the groundwater will likely require treatment before discharge.
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