CAN WE BALANCE USES OF SAND AND GRAVEL DEPOSITS TO SUPPORT LOCAL INDUSTRIES AND PROTECT GROUNDWATER SUPPLIES?
Lamoine, Hancock, and Ellsworth, Maine
Project goals and objectives – The goal of this project was to determine if sand and gravel mining (pits), or pit reclamation, is causing a deterioration of ground water resources in the towns of Lamoine, Hancock, and Ellsworth, Maine. The objectives were:
- inventory drinking water supplies near active pits to update existing GIS coverage;
- inventory drinking water supplies near large reclaimed pits;
- assess changes in water quality using existing information from selected well locations;
- develop a methodology to assign risk rankings to groundwater resources;
- assess how well current regulations are protecting the water resources; and,
- provide the results of this study to towns, concerned citizens, and regulators to help them manage local resources more effectively.
The need – Maine is a state rich in natural resources that provide the support for a diverse economy. These same natural resources also are subject to multiple uses that can establish antagonism between resource consumption and conservation. We proposed to look at one specific area of conflict: sand and gravel deposits. These deposits are a legacy of the glaciers that melted away 10,000 years ago. This geological material is also a source of large quantities of high-quality ground water. The tensions arise when the gravel mining interests intersect the ground water extraction interests. Since sand and gravel aquifers/resources cover less than 5% of the state, these conflicts are comparatively frequent over the competing needs of construction and drinking water.
There are over 3,000 public water-supply wells in Maine and many thousands of private wells. Many of the highest-yielding wells are constructed in sand and gravel aquifers. Sand and gravel mining can affect aquifers through loss of recharge area and by developing new avenues for contamination. Traditionally, old gravel pits were used for dumps and because of that, portions of many aquifers are no longer usable for drinking water.
According to the Maine Department of Environmental Protection (M. Stebbins, pers. com.), the state currently has 160 active sand and gravel pits. These pits cover areas from four to 260 acres. The pits are distributed unevenly and some towns may have up to 14 active pits within their borders. The potential for the pits to alter water quality is high because water can move rapidly through sand and gravel. Gravel pit reclamation also affects water quality, sometimes to a degree greater than mining (Maine Department of Environmental Protection, unpublished data).
This study has provided the context for evaluating how well our natural resources are being protected by state regulations.
The project started with a compilation of geological mapping, gravel pit locations, and well locations from published reports and State of Maine files for Lamoine, Hancock, and Ellsworth (Department of Environmental Protection, Maine Geological Survey, and Drinking Water Program). Much of the data were geo-referenced and available in a GIS format. The inventory first addressed public water supplies because of the larger number of private wells. Also, public water supplies were more likely to have routine water quality testing results.
Detailed studies were conducted in three towns to collect information about private wells in the same aquifer system. We attempted to locate all private wells from within 0.25 miles of the mapped aquifer. Surface water bodies (ponds), streams, and springs draining the aquifer were located and sampled.
Water quality was defined by interviews to assess complaints or concerns, and by a limited amount of water quality testing. Well construction information and distance to pits were recorded. This work included a visual spot check of sand and gravel public-water-supply wells. Chemical properties measured included: water temperature, pH (acidity), Conductivity, Calcium, Magnesium, Sodium, Chloride, Nitrate, Sulfate, and Dissolved Organic Carbon.
Risk rankings were derived from size of pit, pit output, distance from well to pit, depth of well, quality of water (potable or non-potable), slope of terrain, and geology. These relative risk ratings, will be tested for each general location to determine if the Maine gravel mining regulations adequately protect ground water resources. This future testing will be a semi-quantitative process using statistical associations.
Location of sand and gravel aquifer (orange and red shape) in Ellsworth, Hancock, and Lamoine, Maine. Public water supply wells are shown in green.
From Maine Drinking Water Program.
The study area is shown in Figure 1. The dark orange and red shape is the mapped sand and gravel aquifer. The green dots are public water supply wells.
Field data are summarized as follows.
- Met with gravel pit owners (23 owners identified for active pits) to get historical information and permission to sample pit sites (many have been helpful).
- Received permission to obtain any studies of the properties completed by owners.
- Viewed active and abandoned pits between Fletcher’s Landing and Lamoine Beach, approximately 18 locations (not all locations are active pits).
- Size range: 2 to 85 acres.
- Approximately 25% of the surface area of the aquifer is used for gravel pits.
- 55 of the sites visited had accessible wells (as identified by tax map & lot). Only one had water test results.
- Water levels in 55 wells measured. Some properties had more than one well and some properties share a common well.
- The water levels in dug wells ranged in depth from 45cm to 355cm from the surface
- The water levels in drilled wells range from 11m to > 30m (beyond the range of our water-level gauge).
- The bedrock aquifer is likely hydraulically separated from the sand and gravel aquifer.
- Started water sampling and analysis to establish baseline water quality.
- Sampled two seepage ponds: Blunts Pond and Simmons Pond.
- Sampled nine springs.
- Sampled three streams.
- Sampled one public water supply well and four groundwater monitoring wells around source spring (Cold Spring Water Company).
- Evidence of widespread low-level salt contamination, approaching recommended limits for sodium in some samples.
- Evidence of nitrate contamination by public water supply spring.
Is There an Impact from Gravel Pits?
- Field data indicate that significant Water Quality degradation is limited in Magnitude and Occurrence.
- Evidence of salt and nitrate in groundwater, sources are unclear, but likely due to human activity.
- No evidence of large changes in Quantity (changed water levels).
- Problems from former Lamoine Landfill demonstrate importance of Pit Reclamation.
This work has established baseline data to document any future changes. Copies of preliminary laboratory results are shown below. A complete report will be prepared in Fall 2005.
Preliminary Water Quality Testing Results.
Values exceeding the EPA Maximum Concentration Level are in italic.
Thanks to the Lamoine Conservation Commission and the Boards of Selectmen in Lamoine and Hancock and to the Ellsworth City Planning Office for giving their official as well as personal support and to the helpful staff in each of these town offices.
Thanks to Frenchman Bay Conservancy, Hancock County Planning Office, and Union River Watershed Coalition for their in-kind contributions and encouragement.
Thanks to the many volunteers from the area who stepped forward to help.
Burnett, Joan Bragdon
Beth Boland Levesque
Lynda Tadema Wielandt
Chris Aaront, College of the Atlantic
Shari Latulippe, Franklin
Diana Cate, Audubon Society
Elias Kiros Gebreliwot, College of the Atlantic
Simon Michaud, College of the Atlantic
And lastly, many thanks for critical financial support provided by:
- Federal monies granted to the Mitchell Center for on-going projects.
- State of Maine, Department of Human Services, Wellhead Protection grant.
- Maine Community Foundation grant.
- New England Grassroots Environment Fund grant.
- The Island Foundation grant.