1999 Assessment, Prioritization and Environmental Impacts of Uncovered Sand/Salt Piles

A report, entitled Sand and Salt Storage in Maine (pdf file), was prepared for the 120th Maine Legislature. Download Adobe Acrobat Reader (off-site).

In late 1998, the DEP began to re-register and re-prioritize all public and private sand and salt piles. A sand/salt pile re-registration form was mailed to all municipalities. Because of limited staff resources at the DEP, these registration forms were used as a "first cut" to determine which sand/salt piles would need on-site assessments. The sand/salt pile registration form had several key questions on it that determined whether or not a sand/salt pile was visited, such as whether the sand/salt pile was in the same location as registered in 1986, whether there was any visible damage to vegetation in the area, and the distance to the nearest drinking water well.

DEP staff conducted the majority of site assessments on municipal and county sand/salt storage areas and all assessments on private sand/salt piles. DOT’s Division of Environmental Assessment the majority of work at DOT sand/salt piles and assisted on some municipal sites as well. As time allowed, the DEP conducted additional site investigations, however, for the majority of those sites which did not trigger a site visit, the information provided on the registration form alone was used to re-prioritize the site. More than 300 on-site assessments were conducted by DEP and DOT staff.

Through the course of this effort, 674 public and private sand/salt storage areas were registered with the DEP. Of those, one-third (225) were in buildings. The remaining 449 storage sites contained uncovered sand/salt piles (Figure 1). Municipal and county sand/salt piles account for 306 (68%) of uncovered sites; private and state entities account for 143 (32%) uncovered sand/salt piles (Figure 2).

Figure 1 and Figure 2

Impact on Private Water Supplies

One important question that the DEP wanted to answer was "How are private wells currently being impacted by sand/salt piles?"

DEP and DOT staff collected 270 water samples during the course of the project and 243 of those samples were analyzed for chloride. The majority of the analyzed samples (222) were domestic well water samples collected from the homes of residents near sand/salt piles. These individuals voluntarily provided these samples for which the DEP is exceedingly grateful. Twenty-one samples analyzed were from surface water sources. Surface water sources included culverts, ditches, streams and wetlands near sand/salt piles. Two of the twenty-one surface water samples were from brooks used as domestic drinking water sources.

Combining ground and surface water sources of drinking water, the DEP found that just under half of the drinking water samples (47% or 107) had chloride levels less than 20 parts per million (ppm) -- the chloride level considered to be "background" for well water in Maine. Ninety-five samples (43%) had elevated chloride levels, yet below the U.S. EPA-established Secondary Maximum Contaminant Level (MCL) for chloride of 250 mg/l. Twenty-three samples (10%) had chloride levels exceeding the drinking water standard for chloride (Figure 3).

Nearly all the samples with chloride levels that exceeded the drinking water standard came from homeowners; the remaining from public works facilities and garages operated by the owners of the sand/salt piles. All the households affected are in rural areas -- Alexander, Allagash, Brownfield, Carthage, Corinna, Corinth, Fayette, Gouldsboro, Jonesboro, Lowell, Parkman, Sullivan, Sweden, Upton, and Westport. With no public water supply readily available in any of the towns, these homeowners were left to find their own replacement source of drinking water.

The DEP has no fund available to provide immediate relief for individuals whose drinking water has been impacted by salt from sand/salt piles. A 1987 law created a process by which a landowner who believes his/her water supply had been impacted by a public sand/salt pile can apply to the political subdivision (town, county or state) for remedy. The law establishes time frames for response by the political subdivision and allows homeowners to file suit in Superior Court should a satisfactory solution not be reached.

Relationship of Other Site Factors

Three other factors considered in establishing the project priority number for a sand/salt pile were: (1) whether the sand/salt pile was within 2500 feet of a public water supply; (2) whether or not the sand/salt pile overlay a significant sand and gravel aquifer; and (3) the presence of vegetation damage. Broader assessment criteria were used to identify sand/salt piles that may be impacting the environment, but not drinking water, or those piles likely to have a future impact upon drinking water. A cross-tabulation of the factors is found in Figure 4.

The majority of uncovered sand/salt piles (42%) were negative for all three additional factors. Provided there were no current impacts upon a local drinking water supply, it would be unlikely that these sand/salt piles would be of significant concern in the future. Only 2% (11) of uncovered sand/salt piles were positive for all three factors. Ten of those eleven sites are ranked Priority 3 or higher and scheduled to have buildings constructed within the next few years.

The single factor encountered most frequently was vegetation damage. During the site assessment stage, vegetation damage was observed ranging from areas of dead grass and "browning" pines adjacent to the pile to more than 10 acres of dead wetland with salt-encrusted soil adjacent to a maintenance lot. Twelve sites out of the hundreds which were visited were considered to have severe vegetation damage (multiple dead species and soil incapable of supporting plant life). Eight of these twelve are ranked a Priority 3 or higher and are scheduled to have buildings constructed. For comparison, in 1986 only four of the twelve were ranked as a Priority 3 or higher.

Assigning Priority Numbers to Uncovered Sand/Salt Piles

Criteria for assigning priority numbers was based on the work of the Environmental Subcommittee. Although still weighted heavily to the protection of local drinking water, a matrix of five factors was used to determine the project priority number for an uncovered sand/salt pile:

Ground water monitoring data from nearby wells, or, if there are no wells to sample, the presence or absence of a public water system. The starting point of the priority setting process mirrored the 1986 system so as to provide initial consistency between project lists.

The extent of visible damage to trees and wetlands. Because of the effort and resources that would be needed to quantify such damage, a qualitative assessment was done. The impact was judged by investigating staff as begin either none (no noticeable or substantive damage to grass and low-growing vegetation), slight (dead grass/vegetation, browning of leaves and needles/desiccation effects on trees), moderate (dead trees and a larger area of dead grass/vegetation), severe (multiple trees and vegetation species dead, significant area where vegetation is incapable of growing).

Whether the pile is located in an area zoned for commercial, industrial or similar use, or, in the absence of zoning, the likelihood that new houses with wells would be built near the sand/salt pile. Zoning was factored in because municipalities have it within their powers to place sand/salt piles -- public and private -- in areas unlikely to experience residential development and thus reduce the likelihood of impacts to future drinking water supplies.

Distance to the nearest public water supply well and intake. To complement on-going source water protection efforts, a sand/salt pile’s risk was considered higher if it was located within 2500 feet of a public water supply well or intake. Geospatial data on the location of public wells and intakes was provided by the Department of Human Services, Drinking Water Program.

Whether the sand/salt pile is located on a significant sand and gravel aquifer. Significant sand and gravel aquifers are considered a unique ground water resource and are mapped by the Department of Conservation, Maine Geological Survey (MGS). MGS provided current geospatial data to DEP for this determination.

As before, all public and private sand/salt piles were given a project priority number between 1 and 5. Priority 1 sites were those having an immediate and substantial impact upon local drinking water supplies and the environment. Priority 5 sites have no impact upon local drinking water supplies and are unlikely to do so in the future.

At their March 16, 2000 meeting, the Board of Environmental Protection approved the first project priority list, "Project Priority List for Municipal and County Sand/Salt Storage Areas." This first list included project priority numbers for more than 300 municipal and county sand/salt piles. On September 21, 2000, two remaining lists were approved by the Board: (1) the final priority list for more than 140 state and private sand/salt piles and (2) the final priority list for twelve municipal and county sites about which DEP had too little information to finalize a priority number in March.

Summary of Results

As Figure 5 shows, there are 19 new municipal and county Priority 1 sites – sites having an immediate and substantial impact upon drinking water and the environment. Combined, Priority 1, 2 and 3 municipal and county sites – whose owners are still obligated to construct a facility and still eligible for State funding – totaled 91 (30%). Several of these sites contain sand/salt for more than one municipality or are shared by one or more municipalities and the county government. Seventy percent of the uncovered municipal and county sand/salt piles fell in the Priority 4 and 5 categories. Owners of these sand/salt piles are no longer required to construct a sand/salt storage building and no longer eligible for construction reimbursement.

State and private sites show roughly the same proportion as municipalities and counties across the five priorities (Figure 6). Five DOT sand/salt piles and one belonging to a private contractor were ranked as Priority 1 on the state and private sand/salt pile list. All the Priority 2 sites and 28 of the 36 Priority 3 sites on the state and private list are DOT sand/salt piles. The DEP believes that the higher proportion of DOT sand/salt piles in Priorities 1 through 3 may be related to the relative size and age of DOT sand/salt piles to those operated by private contractors. The average registered size of a DOT sand/salt pile is 4,550 cubic yards and has been on its site for more than 35 years. The average registered size of a sand/salt pile operated by a private contractor is 1,465 cubic yards and has been on its site for 20 years. A larger pile on the same site for a longer time simply has the ability to leach larger amounts of salt into the immediate environment.

Map depicting all uncovered sand/salt piles by priority ranking. Looking at the geographic distribution of priority numbers, there are a couple of interesting things to note. First, Priority 1, 2 and 3 sites, while confined primarily to rural areas, are geographically disbursed throughout the state. The DEP does not believe that sand/salt storage presents a more significant ground water contamination problem in one geographic area of the state versus another. Second, Priority 5 sites are confined to urban areas and Priority 4 sites are predominantly in remote rural areas. The reasons are that a site may only be given a Priority 5 ranking when there is a public water supply in the area, something most often found in urban and developed areas. Conversely, most Priority 4 sites are those having absolutely no impact upon private water supplies, so they are found in remote areas away from residences and development. The implications of this are that Maine's larger cities and smaller, rural towns will be least likely to receive funding for construction of a sand/salt building under this program now that Priority 4 and 5 sites are no longer eligible to receive construction funding.