Mining Publication: CO Migration from Trench Blasting in Amherst, New York

The New York State Department of Transportation (NYSDOT) recently began highway widening and drainage improvement projects in Clarence and Amherst, New York. Drainage improvements including the installation of storm sewer lines required excavation to a depth of 2.5 m (8.2 ft). In September 2002, NYSDOT stopped further blasting when 800 ppm carbon monoxide (CO) was detected in the basement of a house near the blasting site. At the insistence of NYSDOT, the general contractor developed a new blast plan with the assistance of an environmental consultant. The plan provided for the installation of multigas monitors in buildings of special concern and/or with basements and residential-type CO monitors in all other buildings within 100 m (330 ft) of the blast. The multigas monitors would be remotely monitored. The plan provided action levels that would ensure public safety. The blast design was also modified to allow for better venting of CO. Blasts were limited to 20-ft lengths. The overburden was to be removed from the rock and blasting mats put in place to prevent flyrock. About 20 ft of trench adjacent to the blast was left open to allow ground movement and gas release. The use of CO monitors was effective to alert occupants of a building to the presence of CO. The most effective seemed to be the residential-type CO alarms with digital readouts. They were simple and easy to use and allowed the public to participate in the process. False alarms were repeatedly received with the more sophisticated instrumentation. Residential-type CO monitors are preferable to warn people near blast sites. More sophisticated instrumentation should be avoided unless personnel are experienced in its use. A general overview of the blasting and monitoring is presented and discussed. The use and effectiveness of residential-type CO monitors and multigas monitors are discussed.