INTRODUCTION

This Libby River Watershed Survey Report was prepared by the Friends of Scarborough Marsh, a coalition of private citizens and organizations pledged to conserve, protect, restore, and enhance the Scarborough Marsh Watershed. The report begins by providing background information on the Libby River and the potential origins and effects of pollutants that may be affecting water quality. The report then discusses the purposes and scope of the watershed survey, the survey findings, and the results of evaluations that are related to the survey. The report concludes with recommendations for protecting and restoring water quality in the Libby River Watershed. While the findings and recommendations contained in this report relate to the Libby River Watershed, much of the information is transferable to similar land uses in other watersheds that are connected to the Scarborough River Estuary. In particular, the recommendations presented in this report could be used as the basis for initiating watershed stewardship and planning activities in all of the estuary watersheds.

The Libby River is an integral part of the Scarborough River Estuary (Figure 1). Estuaries are partially enclosed bodies of water where saltwater from the ocean mixes with freshwater from rivers and streams. Like all estuaries, the Scarborough River Estuary is a food factory for flora and fauna living in the estuary and in the adjoining marine waters. The engine that drives the food factory is "detritus", or the bits and pieces of marsh plants that provide food for organisms at the bottom of the food chain. In turn, the finfish and shellfish that are higher up in the food chain thrive on the organisms that eat detritus.

One measure of the productivity of the Scarborough River Estuary is the economic value of clams harvested by Scarborough clam diggers. For the years 1997 through 1999, Scarborough’s ranking among the 92 Maine towns that reported clam landings in at least one of those years ranged from 4^th to 12^th place (Maine Department of Marine Resources, 2000). Assuming that the average price paid to diggers was $1.50 per pound, the 254,752 pounds of clams reportedly harvested by Scarborough diggers in 1999 earned them approximately $382,128 (Lyon, 2000). Depending on how the clams were processed and sold to consumers (e.g., steamed clams or fried clams), wholesale and retail businesses could have earned another $4 to $8 per pound!

Aside from its high productivity, the Scarborough River Estuary provides several other benefits. The marsh can be likened to a giant, natural water filter. Many types of pollutants that are flushed into coastal and inland waters attach themselves to particles suspended in the water. The suspended particles act like transport vehicles for the pollutants, and when carried into the estuary by rivers, streams, or tidal currents, they either settle or are filtered out of the water by the thick marsh vegetation. The pollutants then become entrapped by layers of sediment and vegetation. Because the broad expanses of marsh slow the incoming currents, the estuary also provides natural flood controls by moderating storm surges that may otherwise inundate low-lying areas. The thick marsh vegetation is also a buffer between open waters and the shoreline and helps to protect the shoreline against wave erosion.

Overall, the Libby River appears to be healthy. Former land uses such as gravel mining and junk- yards, which once contributed to a decline in water quality and habitat, have ceased operation (Town of Scarborough, 1989). Most of the watershed is now served by public sewer which reduces the threat of pollution from failing septic systems. However, old land uses are being replaced by new land uses with a new set of problems. There has been considerable residential development in the upper portions of the Libby River watershed during the last decade. As a watershed becomes developed, the portion of rainfall and snowmelt that seeps into the ground diminishes and the amount that flows into streams from road ditches and storm sewers increases. Much of the water, or runoff, that enters ditches and storm sewers has washed over a landscape that includes lawns, driveways, and roads. Substances that have dripped, dropped, or been deposited onto lawns and pavement are flushed from these surfaces by runoff, yielding polluted runoff. Polluted runoff can ultimately harm water quality in the Libby River and the Scarborough River Estuary.

Polluted runoff can contain a variety of pollutants, depending on the land use in the watershed. In urban watersheds, runoff typically contains the following pollutants:

• elevated levels of nutrients such as nitrogen and phosphorous
• sediment from soil erosion
• bacteria
• toxic substances such as pesticides, herbicides, petroleum products, and metals

Nutrients. Although nutrients are necessary for plant growth both on land and in the water, water bodies that are overloaded with nutrients sometimes experience algal booms, which can rob the water of the dissolved oxygen that aquatic organisms need to survive. Nutrients found in polluted runoff are often associated with the overuse of fertilizers on lawns, gardens, and crops. Phosphorous is the primary nutrient of concern for freshwater bodies, while nitrogen is the primary nutrient of concern for saltwater bodies. In Maine, a 1988 algal bloom that killed shellfish in Maquoit Bay in Brunswick was likely caused by nitrogen enrichment (Casco Bay Estuary Project, 1996). Further from home, low concentrations of dissolved oxygen, or hypoxia, in Long Island Sound have resulted in numerous fish kills. Trawl catches in Long Island Sound have indicated that the abundance of fish is about 40 percent less in hypoxic areas as compared to areas with normal oxygen concentrations (Kennish, 1999). Nitrogen enrichment has been linked to algal blooms and oxygen depletion in the waters of Long Island Sound.

Sediment. Sediment from soil erosion not only carries attached nutrients and toxic substances into water bodies, it also can settle out and smother habitat located on the bottom. It can clog and abrade fish gills, hinder the feeding processes of some shellfish, suffocate eggs and aquatic insect larvae on the bottom, and fill in the pore space between bottom cobbles where some species of fish lay eggs.

Bacteria. Although high bacterial concentrations do not necessarily present a health hazard to humans, they do indicate the possible presence of pathogens, or disease-causing microbes. While urban wildlife and failing septic systems can be a major source of bacteria in polluted runoff, one of the largest sources is pet waste that enters storm sewer systems. National studies have found that polluted runoff in storm sewers contains an average fecal coliform bacteria level of 15,000 to 20,000 counts per 100 milliliters (ml) of water (Center for Watershed Protection, 1999). These numbers far surpass standards used to set safe levels for water uses such as swimming and clamming. The fecal coliform standard typically used for swimming is 200 counts per 100 ml of water and the standard typically used for shellfish beds is 14 counts per 100 ml of water.

Toxic Substances. Sources of toxic substances in polluted runoff are not just limited to industrial land uses in a watershed but include the following potential sources that can be found in residential or commercial areas:

• Oil, grease, and antifreeze leaking or washed from cars and trucks onto paved areas are ultimately flushed into storm sewers or ditches.
• "Do-it-yourselfers" that perform their own car maintenance sometimes unwittingly dispose of used automotive fluids in storm drains.
• Sump pumps and floor drains in homes and businesses connected to storm sewers can produce severe toxic effects on the receiving water body because hazardous waste is sometimes illegally disposed of in this manner.
• Pesticides and herbicides applied to lawns, gardens, and crops can eventually find their way into waterways, even if they are applied according to the manufacturer’s instructions. Some herbicides and insecticides, such as diazinon, can be harmful to aquatic life even at very low levels (Center for Watershed Protection, 2000).

Many of the toxic substances found in polluted runoff are persistent in the environment, meaning that they degrade slowly and can accumulate in the food chain.

Water quality data for the Libby River were acquired from two sources: 1) a study performed by the Town of Scarborough in 1989 and 2) bacteria test results collected by the Maine Department of Marine Resources (DMR). A summary of the water quality data is presented in the following paragraphs.

1989 Study. Limited testing of Libby River water was conducted in 1989 for the Libby River Watershed Water Quality Management Study (Town of Scarborough, 1989). In summary, test results and field observations prompted the following concerns:

• low pH (slightly acidic) and low dissolved oxygen in some of the headwater streams;
• "bad" odors, evidence of petroleum products, and high levels of lead and nickel in water samples collected from areas of dead forest that surrounded gravel pits located off of Black Point Road;
• high levels of metals in water samples that may have been associated with potential sources such as an old landfill in the northern part of the watershed, an old septage dumping area on the Larrabee farm fields, and/or an auto junk yard located near Black Point Road;
• strong sewage smell emanating from a tributary ditch that passes under Marion Jordan Road, and;
• sewage smell from a ditch downstream of a farm pond located near the junction of Spurwink Road and Black Point Road.

Land Use Changes Since 1989 Study. Land uses in the Libby River Watershed have changed significantly since the 1989 study and, although there may be lingering effects on water quality from former land uses, it is expected that they are not having the same impact as they did in 1989. The gravel pits are no longer in operation and in many cases have been converted into ponds surrounded by new homes. Other possible sources of pollutants, such as old landfills and junkyards, have either been covered or have ceased operations.

The sources of the sewage smells noted in the 1989 study were probably associated with failing septic systems. Although most homes and businesses in the watershed are now served by public sewer, some neighborhoods remain on septic systems.

1990 – 2000 DMR Test Results. DMR has been receiving and analyzing water samples collected in the Scarborough River Estuary for decades. The number of samples collected each year has varied, but in order to keep clam flats in the estuary open for harvesting, at least six samples must be collected in the area of the flats each year and analyzed for fecal coliform bacteria (Livingston, 2000).

The standards that DMR uses to determine whether a clam flat is open for harvesting is a geometric mean less than or equal to 14 counts per 100 ml and a 90^th percentile value less than or equal to 49 counts per 100 ml. DMR performs their statistical analyses on the last 30 test results in order to determine whether a clam flat is an open area (Livingston, 2000). Other standards are used to determine if a clam flat that fails to meet the open standards is approved for restricted harvesting.

DMR test results for three sampling stations (i.e., G39, G41, and G42) on the Libby River were evaluated for this report (see Figure 2). The test results are from samples collected in January 1990 through September 2000. Factors that appeared to influence the levels of fecal coliforms in the water samples included the timing of the sampling relative to the tidal cycle, and the amount of precipitation in the days prior to the sampling. The influence that the amount of rainfall has on the levels of fecal coliforms at each sampling station is shown in the following table.

As seen in the table, the amount of rainfall had a significant influence on the levels of fecal coliforms near the mouth of the Libby River (i.e., Station G39) but apparently had little influence on the fecal coliforms levels at the Black Point Road crossing (i.e., Station G42). This suggests that the fecal contamination at Station G42 was associated with a source that supplies a steady stream of pollutants regardless of the weather conditions. This apparent source of dry weather fecal contamination may be a symptom of the "sewage odors" that were detected near the junction of Spurwink Road and Black Point Road during the 1989 Study.

Another evaluation of the DMR test results was performed in order to compare the levels of fecal contamination between the sampling stations. A fair comparison can be made if samples were collected from all three stations at approximately the same time, when the weather conditions and the tidal cycle were similar. Accordingly, the DMR test results were screened to include only the dates on which samples were collected from all three stations. The annual geometric means for each station were then calculated using the test results from those dates and plotted in Figure 3.

Figure 3 confirms that, until 1999, levels of fecal coliforms at Station G42 were consistently greater than the levels at the other two stations, sometimes by a wide margin. This again indicates a source of fecal contamination near Station G42. Figure 3 also explains why the area near the Black Point Road crossing has either been closed or restricted to clam digging for many years. However, since 1995, the geometric means for the Station G42 data plotted in Figure 3 have fallen below the DMR standard of 14 counts per 100 ml. Assuming this trend continues

until there is sufficient data collected to meet DMR requirements, this area could be reopened to clam digging.

Because rainfall and the associated polluted runoff can dramatically increase the levels of fecal coliforms in the Scarborough River Estuary, DMR automatically imposes emergency closures on certain areas (i.e., "conditional rainfall areas") when more than 1 inch of rain falls in a 24-hour period. One of these areas is in the Libby River, upstream of an imaginary line located about 1,000 feet south of Black Point Road.

Most of the salt marsh bordering the main stem of the Libby River is owned by the Maine Department of Inland Fisheries and Wildlife and there are some sections of private conservation land that extend from the salt marsh into upland areas. The State and private conservation land not only protects valuable wildlife habitat but also serves as a natural vegetated buffer that filters polluted runoff from developed upland areas before it reaches the river.

The Maine Department of Environmental Protection (DEP) has determined that the Scarborough River Estuary warrants special consideration in terms of protecting it from polluted runoff. The estuary has been listed as a "Non-Point Source Priority Watershed" in the State of Maine because its water quality is either impaired or threatened to some degree due to polluted runoff. Non-point source pollution is a widely used term for polluted runoff. Its listing as a Priority Watershed means that eligible projects designed to cleanup polluted runoff in the Scarborough River Estuary are more likely to receive federal funding than similar projects in another watershed that is not on the list.

The Scarborough River Estuary is also classified as a "Coastal Wetland Most at Risk from New Development" by the Maine DEP. Consequently, land development projects in the estuary watershed are subject to stricter standards for stormwater management under the State’s stormwater rules. A developer must apply for and receive a stormwater permit (among other permits) before he can proceed with construction. The developer must demonstrate in the permit application to the Maine DEP that he will be able to meet the standards.