LIMITING WATER QUALITY IMPACTS DUE TO LARGE SCALE BLASTING

We will present concepts regarding design of rock blasting programs for construction, with the goal of limiting blasting-related water quality impacts. The 160-acre site is one of the largest private construction projects in Northern New England in the last decade, and included the use of 900 tons of blasting agents to remove approximately 1 million cubic yards of rock. From the permitting phase through construction (2007 to present), Sanborn Head has been the lead consultant on development, implementation and oversight of blasting and water quality monitoring programs.

Municipal officials were very concerned about the potential impact to the Town’s water supply well field located 3,000 feet away from the site, given the project’s magnitude. These concerns were further heightened due to several highly publicized incidents of blasting impacts to drinking water wells in southern New Hampshire over the past 5 years.

Because of the level of concern about the proposed blasting, a blasting and water quality monitoring program, that we believe is one of the most rigorous in the country to date, was developed and implemented in concert with the Town and their hydrogeological consultant. The water quality monitoring program included pre-construction monitoring and monthly monitoring for approximately 18 months of construction, of 17 monitoring wells and five surface water locations for a broad list of parameters. Semi-annual monitoring for up to five years after construction is also planned.

As of the date of this abstract and completion of blasting in November 2011, only very limited exceedances of the project groundwater or surface water quality criteria potentially attributable to blasting, have been observed at the site. These were limited to short-term nitrate exceedances in the vicinity of a blasting “misfire”, and the observed nitrate concentrations quickly returned to within project water quality criteria.