FEASIBILITY ANALYSIS FOR EPA’S DRAFT GREAT BAY TOTAL NITROGEN GENERAL PERMIT IN DOVER, DURHAM, EPPING, EXETER, MILTON, NEWFIELDS, NEWINGTON, NEWMARKET, PORTSMOUTH, ROCHESTER, ROLLINSFORD, SOMERSWORTH NH AND BERWICK, KITTERY, NORTH BERWICK AND SOUTH BERWICK ME

Although this document was not produced by PREP, it is being listed with the permission of the Conservation Law Foundation here due to its importance to PREP’s mission, which is to protect the Great Bay and Hampton-Seabrook Estuaries. This report was developed by Waterstone Engineering, PLLC, and prepared for the Conservation Law Foundation. The intent of this report is to determine the feasibility and cost for regulated communities in the Great Bay watershed to implement the optional non-point source and stormwater point source nitrogen pathway outlined in EPA’s draft Greay Bay Total Nitrogen General Permit. Feasibility was evaluated for a community’s ability to reduce non-point source and stormwater-derived nitrogen by 45% over four 5-year permit periods. This study represents one scenario of many possible pathways and encourages communities to implement innovative nutrient control strategies including a combination of non-structural and low-cost best management practices in addition to more conventional strategies in order to achieve reduction targets

Quantifying groundwater discharge using thermal imagery and conventional groundwater exploration techniques for estimating the nitrogen loading to a meso-scale inland estuary

This dissertation presents the results of a study to evaluate groundwater inflow and nutrient loadings to the Great Bay Estuary, New Hampshire. The evaluation of inflow was accomplished independently by two methods: one, used thermal imagery, and the other, piezometric mapping. The thermal imagery method assessed groundwater that was observed to discharge within the intertidal zone of an inland estuary. The groundwater piezometric mapping method used the monitoring wells around the bay to create an overall piezometric map of the near-bay area. Groundwater discharge was evaluated with respect to flow, concentration, and ultimately nitrogen loading to coastal waters. The results represent a snapshot for these variables, examined by a thermal infrared aerial survey in the spring of 2000, and water quality, specific discharge, and piezometric surface maps in the summer of 2001. Monitoring wells upgradient of the Great Bay were analyzed for nitrogen as an indicator of potential discharge source waters. Total groundwater discharge to the estuary was calculated as 24.2 cubic feet per second (cfs) with an average of 0.81 +/- 0.89 mg dissolved inorganic nitrogen (DIN)/L, with a maximum value of 2.7 mg DIN/L (n = 20). Nutrient concentrations, averaging 0.83 +/- 1.34 mg DIN/L, with a maximum value of 10.2 mg DIN/L, were observed in upgradient bedrock groundwater analyzed from 192 monitoring wells. Nutrient loading was calculated to be 19.3 +/- 21.2 tons of N per year for the total Great Bay Estuary, covering nearly 144 miles of shoreline. The groundwater derived nutrient loading accounts for approximately 5% of the total non-point source load to the estuary. The thermal imagery method was found to be an effective and affordable alternative to conventional groundwater exploration approaches