Project Title:

Inflow Loadings from Ground Water to the Great Bay Estuary

Principal Investigator(s):

Larry K. Brannaka

Thomas P. Ballestero

Tom Mack (USGS)

I. Accomplishments

Scheduled Tasks

There are two tasks, scheduled for the first year of the project, which have been continued into the second year of the project. These tasks include collection and verification of thermal imagery data for the Great Bay Estuarine system, and the preparation of potentiometric maps of the groundwater surface in both the overburden and bedrock aquifers. The first task, part of the first phase of the project, involved several subtasks, including geophysical surveys, aerial infrared surveys, and temperature profiling in the waters of the Great Bay. The second carry-over task is an integral part of the second phase of the project, which is to quantify the groundwater discharge to the bay. This task is to collect data for the preparation of groundwater potentiometric maps of the Great Bay Estuary. The task involves extensive use of private homeowner wells, from which static water level measurements will be made for use in constructing the maps. Each well must be surveyed prior to a coordinated measuring event for static levels in each well.

In addition to these carry-over tasks, the second year task schedule also lists installing monitoring wells in the bedrock, installation of small diameter wells in the overburden, and performing single well tests for aquifer parameters (slug tests).

Progress on Tasks

Progress on the first carry-over task has been steady, although slow. The literature review failed to produce usable thermal imagery in the public sector for the Great Bay Estuarine system. The use of classified data was pursued, and thought to be infeasible for use on this project. Recent developments hold promise for obtaining infrared coverage for our study area. As soon as this data becomes available for review, Mr. Tom Mack of USGS will travel to the Reston, VA office of the USGS to interpret the data.

Since other sources of infrared data are currently unavailable, it was decided to pursue having a thermal infrared aerial survey flown over the Great Bay Estuary and the mouths of the tributary rivers. Several vendors were contacted and reviewed with respect to qualifications, experience, and equipment. Larry Davis Aviation was selected as the vendor to perform the survey. This vendor was chosen specifically for his related experience and desire to participate in scientific research-based application of thermal infrared for groundwater exploration. The survey was contracted for September, when skies were clearest, and there was still more than 4° C difference between the surface waters and groundwater temperatures. UNH researchers planned a series of groundtruth instrument installations to collect actual temperature data during the aerial survey to use to calibrate the images. The vendor chose to ignore the arrangements of the contract, and flew the survey without first contacting the UNH team. Without the groundtruthing, the survey results were inadequate. The contract was subsequently renegotiated, and the vendor agreed to resurvey during the winter months. The optimum time for the survey is when the surface water and groundwater temperatures have at least a 4° C difference, at night, with clear skies, no ground fog, when the bay reaches low tide. The survey could not be performed during the early winter months due to inappropriate weather conditions. In January, ice formed over a large portion of the estuary waters and tributary inlets, preventing a meaningful survey. The survey will be flown in late winter when the ice is dissipated, and the above conditions are met. Based on the success of this survey, a summer survey may be contracted to verify discharge zones observed in the winter survey.

Improvements were made to the research plan simplifying logistical coordination with the survey vendor. Specifically, a moored thermometer array with datalogging capability was deployed throughout the bay. The temperature-logging array was designed to replace groundtruthing by individuals. Instrumentation was selected and purchased, and set out in the bay waters. The array was set up such that calibration points exist through out the entire study area, including a transect to evaluate conditions from the ambient air, ground surface, mud flats, and varying depths of water. These data will be used to assign actual temperature values to the survey results in a gray scale of 0-256.

To better understand conditions which affect survey resolution, an experiment was run to study the temperature of the various landforms in relative to ambient air temperature. The landforms included ground surface, mud flats, and varying depths of water. From this experiment, we concluded the critical environmental conditions to consider for the thermal infrared aerial survey are air, groundwater, and surface water temperatures. The air temperature as well as the groundwater and surface water must have a significant differential; otherwise delineation of groundwater discharge zones will be obscured by environmental conditions. Potential survey times were chosen to maintain a minimum of 4ºC temperature difference between expected groundwater temperatures and ambient air and surface water.

The delay in the Phase 1 task of obtaining thermal infrared images of the Great Bay Estuary has had at least one benefit. It has provided time to develop instrumentation for groundtruthing submarine groundwater discharge (SGWD) zones. Groundtruthing will be required for the discharge zones in the form of temperature profiles. These will be performed using a boat and a submersible temperature/specific conductivity probe at locations obtained from the thermal infrared coverage. Instrumentation for the groundtruthing has been assembled, completed and tested. This includes a GPS instrument which will be used in conjunction with the temperature probe for mapping temperature anomalies. A differential correction beacon has been obtained which enables improved GPS accuracy. A laptop computer will be used for datalogging temperature and GPS information on the boat. Datalogging software was written to interface with the GPS and the temperature/specific conductivity meter to provide real-time logging capability. Robert Roseen has been certified as a boat pilot through the US power squadron boating safety course, thereby qualifying him to pilot vessels at the Jackson Estuarine Lab.

Substantial progress has been made on the second carry-over task for Phase 2 of the project. To construct a potentiometric surface map of the groundwater aquifer in both the overburden and bedrock, we solicited help from homeowners surrounding the Great Bay. Over 300 homeowners responded positively to participate in this study. To date, 174 residential wells have been surveyed as to latitude and longitude, relative elevation, and depth to water. Each has been evaluated for future use in aquifer characterization, and water quality assessment. The relative elevation of site was established by creating a temporary benchmark along the roadway frontage of the residence, referenced to the well casing elevation. The temporary benchmarks will be later surveyed with reference to existing benchmarks of known elevation. Completion of the well surveys is expected sometime in the spring or when approximately 250-300 wells have been completed. Additional well data is being obtained from public records of monitoring wells at Pease International Tradeport to fill out the coverage around the Great Bay. It anticipated that 30 or more wells from the Tradeport will provide critical data points for construction of the piezometric surface maps for the study area.

Additional progress has been made on the second phase of the project. This includes the drilling, coring, and installation of three bedrock monitoring wells around the bay. Sites were selected in conjunction with the USGS. Wells were installed at Adams Point, to evaluate the structure and geochemistry of the Kittery formation; Fabyan Point, and the National Wildlife Refuge (NWR) to evaluate the Elliot formation. The Adams Point well is located on Adams Point Wildlife Management Reserve (APWMR) which is under jurisdiction of the New Hampshire department of Fish and Game and a part of the Great Bay Research Reserve (GBNERR). The New Hampshire Fish and Game department supported the University of New Hampshire’s research efforts in conjunction with the GBNERR. The permit agreement includes mutual ownership of the well and university maintenance as long as research continues, remediation, and revegetation as necessary resulting from the drilling efforts. Additionally, the UNH research team agreed to produce a one page informative placard to be mounted at the viewing platform at the APWMR . The placard will explain the purpose of the research and the role that the well, in full view of the viewing platform, plays.

Permitting at Fabyan Point was with a private landowner who is interested in supporting research efforts around the bay. The landowner has volunteered the well for a clean water source for another UNH research project at Pease International Tradeport.

The well at the NWR required a special use permit from the US Fish and Wildlife Service. The permit specifies advance notification to the NWR for use of the well and a copy of the final report. Pump tests have been run at two the wells and the third will be completed when weather permits. The pump tests will provide aquifer characteristics critical to quantifying groundwater flow.

The three project wells support cooperative efforts of three research projects. The bedrock core is being used for doctoral research in structural geology with the Department of Earth Sciences at UNH. To date, a detailed core analysis has been performed for at least one of the well cores. This analysis may provide insight to groundwater origins and transport. The study has been performed by Jose Cruz Escamilla-Casas under the direction Dr. Wallace A. Bothner. The wells and the bedrock core have become a part of the National Water Quality Assessment (NAWQA). NAWQA is a USGS project studying the geochemistry of the bedrock with particular emphasis on arsenic. Mr. Joseph Ayotte of the USGS, has taken water quality samples during and after pump tests on these wells to further the USGS study. Additional NAWQA work includes analysis for sulfur isotopes in the core and the water, and examining mineral assemblages of the sulfides in the core. All information gathered by the cooperative research projects will be made available to this study.

 

Difficulties Encountered

The largest difficulty encountered to date has been in the first phase efforts to obtain a usable thermal infrared image of the Great Bay Estuary. This difficulty still remains the primary delay in the first phase of the project. Fortunately, work has been able to progress on the other aspects of the first phase and the second phase of the project, such that the difficulty with the infrared imagery has not resulted in a delay in the project completion. As mentioned above, the solution to this difficulty will be in the flight of an infrared thermal aerial survey, along with possible classified imagery. The aerial survey was initially planned for the late summer however schedule conflicts by the vendor prevented flying at optimal times. The vendor eventually did fly an unsuccessful survey in late fall without notification of the university research team. The lack of notification prevented deployment of critical groundtruthing instrumentation for calibration of the thermal imagery. Without the calibration data, the survey was useless must be reflown. Renegotiations with the vendor ensued and a resurvey in the winter was contracted at virtually no additional cost to the project. The redrafted contract was explicit with requirements for coordination of the survey and calibration efforts. Provisions were included requiring the vendor to obtain permission prior to flying. Furthermore, the deployment of the thermometer array months in advance of the survey greatly simplified coordination efforts. The coordination with the university research team and the vendor is now limited to verification of the proper weather and tidal conditions. Considering the limited number of qualified vendors and the large time investment with the current vendor, it was felt in the best interest of the project to continue to work with Larry Davis Aviation. The extremely detailed research requirements are beyond the usual commercial uses and necessitate a vendor willing to accept a multitude of demands.

Difficulties have also been encountered in the second phase efforts to construct a potentiometric surface map of the groundwater aquifers. The difficulty is in the process of economically surveying the actual elevations of the well casings used in the study. The overwhelming public support and participation in the project has resulted in a large number of widely spaced survey locations. The potentially three hundred wells, (if all respondent wells are used), will increase accuracy and resolution of the potentiometric surface maps. The large numbers, however, adds up to many miles of roads to survey, which by traditional means may be prohibitively expensive. Alternatives are currently being reviewed as to how best to reasonably utilize as many data points as is feasible.

Anticipated Success in Meeting Project Objectives in Scheduled Project Period

None of the delays will affect the completion of scheduled project objectives. Should the difficulties in obtaining the thermal infrared imagery continue into the summer, this delay has the potential to become a problem. The Phase 2 work is on schedule for completion by the end of the summer.

Preliminary data

The project is still within the data gathering stage, and preliminary analyses stage. An example of preliminary data is presented in the form of Map 1. This map illustrates the geographic distribution of completed well surveys that will be used to construct the regional groundwater map for the overburden and bedrock water tables. The map illustrates the areal coverage of the homeowners participating in the study, and is used to target areas with insufficient coverage. Homeowners in these areas are put on the higher priority list for well surveys.

The preliminary analyses of the reflection survey, the lithology, and the bedrock topography are interpretable for some areas of the bay, primarily where the depth of water was more than 10 feet. Since the initial analyses of the side-scan radar survey did not reveal large pock-mark discharge zones, the survey data is undergoing more detailed analyses in conjunction with the lineament survey, seismic reflection data, and site-specific mapping. The mapping has revealed that the west and east sides of Great Bay have very different fracture characteristics. The east-side of the bay had more cold springs that are possibly related to bedrock fracture zones. A number of possible bedrock fracture zones were targeted for observation wells, which have been installed.