GUIDE FOR ASSESSING WATER-QUALITY IMPACTS OF HIGHWAY OPERATIONS AND MAINTENANCE

A 5-year effort to characterize highway runoff in Washington State resulted in the accumulation of data from more than 500 storms at nine locations and the development of a guide for assessing aquatic impacts of operating highways. The data were used to construct a simple model that expresses cumulative pollutant loadings as functions of highway segment length, average runoff coefficient, and vehicles traveling during storm periods. To assess pollutant loadings and concentrations in runoff from an individual storm, cumulative distributions were analyzed to determine the probability of specific loading and concentration values being exceeded in a given case. Bioassay studies of highway runoff indicated toxicity to aquatic life when heavy deposition of metals from high traffic volumes (is less than 10,000 vehicles per day) or high concentrations of metals in rainfall caused concentrations in runoff to exceed lethal levels. Draining highway runoff through grass channels 200 to 300 ft long greatly reduced concentrations of solids and metals and the consequent toxic effects. The impact assessment guide incorporates these results in a stepwise procedure for use by highway designers and environmental impact analysts in the Pacific Northwest. The guide is organized in three analysis levels, ranging from a rapid screening method intended to identify those cases with a low probability of extensive impacts (level 1) to a detailed evaluation focusing on impact mitigation (level 3). It presents methods for assessing the water-quality impacts of winter maintenance and special problems in addition to the effects of runoff from routinely operating highways. (Author)

Media Info

  • Media Type: Print
  • Features: Figures; References; Tables;
  • Pagination: pp 31-40
  • Monograph Title: WETLANDS, FLOODPLAINS, EROSION, AND STORM WATER PUMPING
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00389551
  • Record Type: Publication
  • ISBN: 0309036690
  • Files: TRIS, TRB
  • Created Date: Nov 30 1984 12:00AM