Optimization of Interim Offshore Monitoring Program at Portsmouth Naval Shipyard, Kittery, Maine

摘要

Background/Objectives. Portsmouth Naval Shipyard (PNS), Kittery, Maine, is located on an island in the Piscataqua River, referred to as Seavey Island. The Piscataqua River is a tidal estuary that forms the southern boundary between Maine and New Hampshire. An Interim Record of Decision for OU4 was signed in May 1999 that required the Navy to conduct interim offshore monitoring for OU4. Therefore, the Navy prepared and implemented a monitoring plan to provide data on the offshore areas to determine whether onshore remedial actions, natural process, and/or other sources have affected the chemical concentrations in OU4. The data quality objective (DQO) process was used to identify data needs, decision rules, and data evaluation methodology. Approach/Activities. Sampling was conducted at 14 monitoring stations located around PNS and at four reference stations in the Great Bay Estuary. The sampling program initially consisted of collecting sediment, mussel, and juvenile lobsters at the monitoring and reference stations, which were analyzed for a variety of parameters. Data evaluations were conducted throughout the monitoring program such as determining whether chemical concentrations were: (1) changing over time, (2) similar to background concentrations, and (3) greater than interim remediation goals, to name a few. To date, eleven rounds of samples have been collected. Based on the results of the data evaluations, several modifications were made to optimize the monitoring program. Results/Lessons Learned. These modifications occurred at various points in the monitoring program and included the following: discontinuation of juvenile lobster and mussel sampling (after Round 5 and 7, respectively), reduction of analyte list (after Round 5, 7, and 10), and elimination of sampling stations (after Round 8). These modifications resulted in significant cost savings for the Navy, and allowed the project team to focus on those chemicals that were considered the risk drivers and on those stations that continue to potentially impact ecological receptors. Having several rounds of monitoring data allowed the Navy to better support the recommendation of remedial actions at four monitoring stations and no further action at ten monitoring stations.