ALKALINE LEACHATE AND CALCAREOUS TUFA ORIGINATING FROM SLAG IN A HIGHWAY EMBANKMENT NEAR BALTIMORE, MARYLAND

A series of springs located along the lower contact of a slag bed 3 to 7 m thick sandwiched within an embankment for Interstate 695 in Baltimore County, Maryland, discharges water with a pH of 12.5 to 13 and a dissolved calcium concentration of roughly 1000 mg/L. Further reactions with atmospheric CO2 cause this leachate to precipitate copious quantities of calcite (CaCO3) in the form of surficial tufa, interstitial cement within the fill, or fine powdery sediment in surface water. Because of its high pH, the leachate is classed as a hazardous waste, and the Maryland State Highway Administration has been required to construct a fenced enclosure and containment pond for the springs and to haul away the leachate or treat it before discharge. The cost of remediation had reached $1,000,000 by early 1994, when a treatment plant using hydrochloric acid to neutralize the leachate was about to begin operation. This case history demonstrates that great caution should be exercised in use of industrial by-products as construction materials. Although other recent studies have clarified the mechanism of tufa formation, unanswered questions remain regarding the mobility and fate of labile constituents other than calcium. Such questions must be answered before such reactive materials are dispersed into the environment in the name of recycling.

Language

  • English

Media Info

  • Features: Figures; References; Tables;
  • Pagination: p. 3-7
  • Monograph Title: Subsurface drainage, soil-fluid interface phenomena, and management of unpaved surfaces
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00666223
  • Record Type: Publication
  • ISBN: 0309055113
  • Files: TRIS, TRB
  • Created Date: Sep 16 1994 12:00AM