Crews perform hydro-demolition of bridge decking on New York's 1-481. Photos: Christopher Anderson
Left: A previous version of the settlement basin had slurry overtopping the structure—also known as the “swimming pool effect.” Right: The updated fast-filtration basin used crushed glass in its design.
Testing the Results
Specialists took a set of grab samples as the slurry entered the filtration system, and from the area at the base of the filter bed (the exit point) to quantify the percent removal of TSS and change in pH. Life Science Laboratories of East Syracuse, N.Y. (a New York State Department of Health certified lab) conducted the analysis, determining the average TSS concentration of the influent to be about 2950 mg/L and the effluent about 115 mg/L. This indicated a TSS removal rate of approximately 96% and a reduction of pH from 11.8 to 11.6 standard units. Although there are not any quantitative limits for a specific pollutant of concern from such operations to date, water quality violations can still be issued based on visual cues, such as turbidity.
The regional staff also has discussed the idea of placing pine mulch or peat moss around the base of the basin to promote a natural neutralization of the effluent. In other parts of the state where acid rain is a major concern, such as the Adirondacks, the high pH of the effluent may prove to be a suitable low-cost method for temporarily liming surface waters.
Although the contractor initially had reservations about using glass, it turned out to be lightweight, less difficult to manage, and more economical than stone; the contractor vowed to use it again on similar projects. Even officials from the NYS Department of Environmental Conservation—the body that regulates the SPDES program—visited the site and were pleased with the operation.
Based on the successful filtration achieved at the test site, a number of projects within the region have been designed to use crushed glass as a component for structures for temporary and/or permanent stormwater management.
The filtration system using the crushed glass cullet is a beneficial solution. The material is a recycled product that reduces the waste stream; is environmental friendly, cost-effective, and easy to handle; and most of all, it works.
—Anderson is an environmental specialist with the NYSDOT's Landscape Architecture and Environmental Service Unit. Steele is the Construction Unit's environmental contact for the Region 3 office in Syracuse, N.Y.