summary

                The Maryland Department of the Environment’s Water Supply Program (WSP) has conducted a Source Water Assessment for thirty-five community water systems in Saint Mary’s County.  The required components of this report as described in Maryland’s Source Water Assessment Program (SWAP) are 1) delineation of an area that contributes water to each source, 2) identification of potential sources of contamination within the areas, and 3) determination of the susceptibility of each water supply to contamination.  Recommendations for protecting the drinking water supplies conclude this report.

            The water supply sources of community systems in Saint Mary’s County are naturally protected confined Coastal Plain aquifers. The thirty-five community water systems included in this report are currently using 104 wells that draw from four different confined aquifer systems.  The wells are completed in the Piney Point, Nanjemoy, Aquia, and Patapsco Aquifers respectively.  The Source Water Assessment areas were delineated by the WSP using ten year time-of-travel particle pathlines modeled by the Maryland Geological Survey for specific public supply wells, and by other U.S. EPA approved methods specifically designed for sources in confined aquifers. 

            Potential point sources of contamination within and near the assessment areas were noted from field inspections and contaminant inventory databases.  In confined aquifer settings, sources of contamination at the land surface near the wells are generally not a threat unless there is a pathway for direct injection into the deeper aquifer such as through unused wells or along well casings that have no grout seal.  A map showing the   wellhead protection areas for each community system is enclosed at the end of the report.

            The susceptibility analysis is based on a review of the existing water quality data for each water system, the presence of potential sources of contamination in the individual assessment areas, well integrity, and aquifer characteristics.  It was determined that the community water systems are not susceptible to contaminants originating at the land surface due to the protected nature of confined aquifers.  Some naturally occurring contaminants pose a risk to the water supplies that have detected these elements at levels of concern.  It was determined that twenty-one systems are susceptible to arsenic (based on the new EPA standard).  Twenty-six systems may be susceptible to radon depending on the final MCL that is adopted for this contaminant.

Introduction

            The Water Supply Program has conducted a Source Water Assessment for the thirty-five community water systems in Saint Mary’s County.  Saint Mary’s County forms the southernmost peninsula of the Western Shore of Maryland.  The county is bounded by Charles County to the northwest, the Patuxent River to the northeast, the Potomac River to the south, and by the Chesapeake Bay to the east (Figure 1).  Based on July 2001 data, the total population of Saint Mary’s County is 92,100 persons (Md. Assoc. of Counties, 2001).  The thirty-five community systems serve a population of approximately 51,401 residents, while the remaining residents in the county obtain their water supply from individual wells.  The community systems include the incorporated municipality of Leonardtown, twenty-four unincorporated areas whose water systems are owned and operated by the Saint Mary’s County Metropolitan Commission (METCOM), seven privately owned and operated systems, two State institutions including St. Mary’s College, and Charlotte Hall Veterans Home, and the Patuxent Naval Air Station.  All of the community systems in Saint Mary’s County obtain their water supply from confined, unconsolidated Coastal Plain sediments. 

Well Information

            Well information for each system was obtained from the Water Supply Program’s database, site visits, well completion reports, sanitary survey inspection reports, and published reports.  A total of 104 wells are used by the 35 systems assessed in this report.  Seventy-seven of the wells were drilled in or after 1973 and should comply with Maryland’s well construction regulations for grouting and casing.  A review of the available well completion report data indicates that three other wells drilled in 1972, and one well drilled in 1970, were also grouted around their respective casings.  Nineteen wells that were drilled prior to 1973, when current regulations went into effect, may not meet the current construction standards.  Well completion data was not available for the remaining four wells. Table 1 contains a summary of well information for each of the community water systems.

Based on site surveys, the supply wells were generally in good condition.  Some of the older wells should have a two-piece well cap installed to prevent contamination from insects through unscreened vents and electrical conduits. A review of the Public Drinking Water Information System (PDWIS) database indicates unused wells completed in the same aquifers as the production wells for fourteen of the systems in this report (Table 1a). Unused wells that are not exercised regularly, have no pumps, or that are no longer connected to the system may provide a direct pathway for ground water contamination to the deep, confined aquifers.  These wells should be properly abandoned and sealed by a licensed well driller according to the current State regulations.  

Hydrogeology

Ground water flows through pores between gravel, sand, and silt grains in unconsolidated Coastal Plain formations that are used by all of the community water systems in Saint Mary’s County.  An aquifer is any formation that is capable of yielding a significant amount of water.  Transmissivity is a measure of the amount of water that an aquifer is capable of producing, and is the product of hydraulic conductivity and aquifer thickness.  Confining layers are composed of fine-grained clay and silt material that have very small pore spaces and therefore transmit very little water.  Confined aquifers are those formations that are overlain by one or more confining layers.  They are recharged very slowly from the water stored in the confining layers above, and from precipitation that infiltrates into the formation where it reaches the ground surface, referred to as the outcrop area.

Saint Mary’s County is underlain by unconsolidated sediments of the Coastal Plain Physiographic Province.  The sediments were deposited in a southeasterly thickening wedge extending from the Fall Line (roughly the area east of Interstate 95) to the Continental Shelf.  They consist of layers of clay, silt, sand, and gravel that form a series of interbedded aquifers, and confining layers that gently dip to the southeast (Achmad & Hansen, 1997).  The unconsolidated sediments overlie a complex assemblage of crystalline bedrock.  The age of the deposits (from oldest to youngest), range from Cretaceous, just above the crystalline basement rocks, to Tertiary, to Quaternary near the land surface.  A generalized description of the water bearing properties and lithology of the major aquifers and confining units of Southern Maryland is shown in Table 2.  The confined aquifers used by the community water systems in this report include the Eocene aquifers Piney Point, and Nanjemoy Formations, the Aquia Formation of Paleocene age, and the Lower Cretaceous Patapsco Formation respectively.  Multiple confining clay units of low permeability that inhibit the infiltration of contaminants from the land surface overlie these aquifers.  General descriptions of each aquifer are shown below.  The reader may refer to the referenced Maryland Geological Survey reports for additional information.

Piney Point Formation

            The Piney Point aquifer is used by nine of the Saint Mary’s County community water systems.  The thickness of the Piney Point Formation ranges from 0 feet (northwest of Leonardtown) to 130 feet at Point Lookout (Figure 4).  It does not exist in the northwest portions of the county.  The formation consists of medium to course grained mottled grayish green slightly glauconitic sand with interbedded clayey layers, and small shell fragments.  The top of the Piney Point Formation ranges from 50 feet to about 350 feet below sea level in Saint Mary’s County (Figure 5).  Transmissivity values range from 125 to 740 ft²/day (Achmad & Hansen, 1997).  The Piney Point aquifer is overlain by the Chesapeake Group Formations that function as upper confining beds in Saint Mary’s County.  The Piney Point aquifer does not outcrop at the ground surface.  Recharge is derived from water table aquifers above, and possibly the Nanjemoy Formation below.

Nanjemoy Formation

            The Nanjemoy aquifer is used by the Christmas Tree Farm Trailer Park.  The cumulative sand thickness of the Nanjemoy Formation ranges from 0 feet to 15 feet and generally thickens to the northwest (Figure 4).  The formation consists mainly of greenish-black to yellowish glauconitic clayey to clean sand (Ferguson, 1953).  The formation tends to coarsen upward, as the upper part of the Nanjemoy is commonly a glauconitic medium-sorted fine sand whereas the lower layers consist of silty clay (Chapelle & Drummond, 1983).  The top of the Nanjemoy Formation ranges from sea level to about 400 feet below sea level in Saint Mary’s County.  The Piney Point and Nanjemoy aquifers are often hydrologically connected (Achmad & Hansen, 1997).  The Nanjemoy Formation lies under the Piney Point Formation, and overlies the Marlboro Clay in Southern Maryland.  The outcrop areas of the Nanjemoy Formation are illustrated in Figures 4 and 5.

Aquia Formation

            The Aquia is the most widely used aquifer by the Saint Mary’s County community water systems as twenty-seven of the systems withdraw water from this aquifer.  The thickness of the Aquia Formation ranges from 0 feet (near the Point Lookout Area) to 175 feet near the northwest county border (Figure 2).  Hydraulically, the Aquia functions as a confining bed in the southern-most tip of Saint Mary’s County (Achmad & Hansen, 1997).  The formation consists of moderately to well-sorted, medium to course grained light colored to greenish-black glauconitic sand with calcareous-cemented sand and shell beds.  The top of the Aquia Formation ranges from 250 feet to about 520 feet below sea level in Saint Mary’s County (Figure 3).  Transmissivity values range from 365 to 885 ft²/day (Achmad & Hansen, 1997).  The Aquia aquifer is overlain by the Marlboro Clay that functions hydrologically as a confining unit.  The Marlboro clay is described as a very tight, pink to silver-gray plastic clay (Chapelle & Drummond, 1983).  The Aquia Formation outcrops along the Potomac River in northwestern Charles County and in a band about 10 miles wide from Capital Heights and Upper Marlboro northeast into Anne Arundel County (see Figures 2 and 3).

Patapsco Formation

            The Patapsco aquifer is used by four of the Saint Mary’s County community water systems.  The Patapsco Formation consists of fine to medium grained greenish gray sand, with layers of mottled clay.  The top of the Patapsco Formation ranges from about 540 feet to 700 feet below sea level in Saint Mary’s County (Achmad & Hansen Plate 2, 1997).  The Patapsco aquifer is overlain by one or more Cretaceous Units combined with the Brightseat Formation of Lower Paleocene age to form a composite lower confining bed of variable thickness in Saint Mary’s County (Table 2).  Arundel clay lies immediately below the Patapsco Formation.  The outcrop area extends from Washington D.C. to Elkton, Maryland in a band of varying width.  Between Washington and Baltimore, the outcrop area is between 10 and 20 miles wide. 

 

Source Water Assessment Area Delineation

            For ground water systems, a Wellhead Protection Area (WHPA) is considered to be the source water assessment area for the system.  In July 2000, the Maryland Department of the Environment (MDE) provided a grant to the Saint Mary’s County Metropolitan Commission to develop a Wellhead Protection Program.  The program was to include an investigation of all well sites owned and operated by the Commission.  In cooperation with MDE, the Maryland Geological Survey delineated wellhead protection areas for public water supply wells operated by METCOM, and other selected ground water users in Saint Mary’s County.  The ground water flow model (MODFLOW), and the particle-tracking post-processor (MODPATH) were used to backtrack particle pathlines from production wells completed in the Piney Point and Aquia Formations respectively for time periods of one, ten years, and twenty years (Achmad & Fewster, 2003).  MDE staff then delineated the WHPAs in this report based on the endpoints of the pathlines that define the ten-year zone of transport for the production wells.  The reader may refer to the MGS report for further details regarding the ground water modeling study (Achmad & Fewster, 2003).

            Community water system wells that were not addressed in the MGS study were delineated by MDE based on the methodology described in Maryland’s Source Water Assessment Plan (MDE, 1999). Wells drilled into confined aquifers in the Coastal Plain are to be delineated using a volumetric equation referred to as “The Florida Method”.  The method is used to calculate the volume of aquifer needed to store the quantity of water pumped from the well for a ten-year period.  The equation is as follows:

where:    r = calculated fixed radius (ft)

                    Q = pumping rate of well (ft³ / yr)

               t = time of travel in years (yr)

                         n = aquifer porosity (dimensionless)

             H = length of well screen (ft)

            A porosity (n) of 40% was assumed for each of the aquifers based on published reports (Morris & Johnson, 1967).  For systems with multiple wells, the average well pumpage was based on the percentage of use for each well from monthly operating reports over the past two years.  For systems with standby wells, the total average permitted amount (where available) was used for each well.  The lengths of well screens (H) were obtained from well completion reports and published reports.  The sum of the individual screen lengths was used for wells that draw water from multiple screens.  The volumetric equation was solved for each well using the pertinent data as shown in Table 3.  The resulting WHPAs are radial zones of transport based on a ten-year time of travel     (Figure 1).  The average permitted amount for Hills Mobile Home Park from the MGS study pertains to Lord Calvert, and not Hills Trailer Park respectively (Achmad & Fewster, 2003).  Based on monthly operating reports pumpage data from the past year, the average daily useage for this system is 23, 435 gallons per day (gpd).  The WHPA was re-delineated by MDE using the Florida Method as shown in Table 3, and Figure 1.

            Systems with multiple wells that share the same aquifer and whose radial areas overlap were combined to form one larger WHPA.  The protection areas for assessment purposes are located within the aquifer below the confining layers at depths below the land surface. Diagram 1 is a conceptual illustration of a WHPA in a confined Coastal Plain aquifer setting.

Diagram 1.  Conceptual Illustration of a Zone of Transport for a Confined Aquifer

Potential Sources of Contamination

            Potential sources of contamination are classified as either point or non-point sources.  Examples of point sources of contamination are leaking underground storage tanks, landfills, discharge permits, large-scale feeding operations, and known ground water contamination sites.  These sites are generally associated with commercial or industrial facilities that use chemical substances that may, if inappropriately handled, contaminate ground water via a discrete point location.  Non-point sources of contamination are associated with certain types of land use practices such as the use of pesticides, application of fertilizers, sludge or animal wastes, or septic systems all that may lead to ground water contamination over a larger area.  All of the community water systems in this report draw water from confined aquifers.  In confined aquifer settings, sources of contamination at the land surface are generally not a threat unless there is a pathway for direct injection into the deeper aquifers such as through unused wells that have not been properly abandoned, or along well casings that have no grout seal.

            Several inspections of facilities located within and near the WHPAs were conducted by MDE staff to determine the potential for contamination to the aquifers of any unpermitted ground water discharges (e.g. open floor drains), and unused wells.  One such facility received a notice of violation (NOV) for the use of an open floor drain. The company addressed this issue, and is now in compliance with the MDE Ground Water Permits Program.  Four other facilities have potential discharge issues that are pending to date.  The details of these inspections are discussed in Appendix A.  Ground water discharges to the shallow unconfined aquifers should not pose a threat to the deeper confined aquifers.  These aquifers are naturally protected from land use activities originating from the ground surface unless there is a pathway for direct injection (e.g. unused wells) into the confined aquifer.  Fourteen of the community water systems from this report have one or more unused wells located within their respective WHPAs (Table 1a).  No other unused wells were reported from underground injection control (UIC) inspections conducted by MDE staff.  However, there may be others (e.g. unused residential wells) that are currently not inventoried, due to limitations in database, and inspection staff resources.  Reports of additional sites that were inspected are available from MDE.

            The Saint Mary’s County Metropolitan Commission, and the Maryland Rural Water Association conducted an on-site investigation of potential contaminant sources located within the wellhead protection areas of the community systems operated by METCOM in March 2003.  As part of this study, potential sources were mapped, and identified on aerial photographs that displayed each of the wellhead protection areas.  The results of this investigation can be found in the Commission’s Well Head Protection Program report (METCOM, 2003).    

            Two sites have been identified as having historical or potential soil and shallow ground water contamination concerns within or near the wellhead protection areas of three community systems.  These sites are located near the Lexington Park’s Saint Mary’s Industrial Park Well 1R, the Peggs Road Well, and Patuxent Naval Air Station Building 536 Well 1R, and Building 587 Well 5A.  Appendix B provides general site information and fact sheets for these facilities.  There are also several facilities along the commercial corridors of MD Routes 5, 235, 245, 246, and within the Leonardtown, Lexington Park, and Patuxent Naval Air Station boundaries that have underground storage tanks located within or near respective WHPAs.  Many of these facilities have had their tanks replaced with newer ones due to leaks or non-compliance with current State tank regulations. Other facilities had their USTs permanently removed due to leaks or non-compliance issues.  Still others are currently under investigation by the MDE Oil Control Program (Appendix C).  None of these sites should present a water quality threat to any of the community supply wells from this report due to the natural confining clay layers that protect the aquifers from contamination that occurs near the ground surface.  Contamination from these sites may threaten the water quality of the shallow unconfined aquifers only.  The sites listed in the appendices are for awareness purposes only.  The reader may contact the specific programs within the MDE Waste Management Administration for additional information regarding potential contaminant sites in Saint Mary’s County.

Water Quality Data

                Water Quality data was reviewed from the Water Supply Program’s database and system files for Safe Drinking Water Act contaminants.  Raw water testing was conducted in 2003 for all METCOM production wells as part of their Well Head Protection Program grant agreement.  The parameters that were tested are as follows:  conductivity, turbidity, temperature, pH, coliform, hardness, sodium, arsenic, bromide, chloride, gross alpha, gross beta, and dissolved oxygen.  These tests were conducted to check the overall integrity of each of the METCOM wells, to address possible concerns regarding salt water intrusion, naturally occurring arsenic levels, and to establish a baseline for future comparative purposes.  The State’s SWAP defines a threshold for reporting water quality data as 50% of the Maximum Contaminant Level (MCL). If a monitoring result is at or greater than 50% of a MCL, this assessment will describe the sources of such a contaminant and, if possible, locate the specific sources which are the cause of the elevated contaminant level. The data reported is from finished (treated) water except for the special raw water sampling conducted for the METCOM wells.  Only one of the systems currently does not use water treatment. The treatment methods currently in use for the remaining 34 systems included in this report are summarized in Table 4.

A review of the monitoring data since 1993 indicates that the water supplies for the 35 systems in this report meet the drinking water standards with the exception of arsenic (Table 5).  Tables 6a-6c provide a list of all detections above 50% of the respective MCLs. Radon-222 was detected in eight of the systems at levels at or above the more conservative MCL proposed by EPA for regulations in drinking water       (Table 6b).  However, no standard has been established for radon in drinking water. Volatile organic compounds have been detected at very low levels well below their respective MCLs in the water supplies of 12 systems.  However, subsequent sampling events at all but one of the systems has shown no detects of these compounds.  Synthetic Organic Compounds were detected at very low levels in 12 of the 35 systems tested from this report.  However, the only SOC compound detected above 50% of its respective MCL was found in laboratory blank samples, and therefore does not represent actual water quality of this system (Table 6c).  

Inorganic Compounds (IOCs)

A review of the available data shows that arsenic, chromium, and fluoride were the only IOCs detected at or above 50% of their respective MCLs (Table 6a).  Chromium was detected in only one sample at the Patuxent Naval Air Station Plant 19 in 1999, and was not detected again in a subsequent sampling event.  Fluoride was also detected over the 50% MCL threshold of 4 parts per million (ppm) in only one sample in 1998 at the Patuxent Naval Air Station Plant 3.  Subsequent sampling at this plant showed fluoride levels at 1.1 ppm. 

Arsenic was detected above 50% of the MCL in 27 of the 35 systems, and was detected in repeat sampling for 22 of the systems (Table 5).  The arsenic standard was recently lowered from 0.050 ppm to 0.010 ppm by the USEPA.  With the exception of one detect over the 50% MCL threshold in the Piney Point and  Patapsco Formations respectively, arsenic was primarily detected in wells drawing from the Aquia aquifer (Table 6a).  Based on available data, arsenic was detected once in the well completed in the Nanjemoy aquifer at 0.003 ppm.  No other regulated IOCs were detected at levels of concern for the 35 community systems.  

Radionuclides

There is currently no MCL for Radon-222, however EPA has proposed an MCL of 300 picocuries per Liter (pCi/L) or an alternate of 4000 pCi/L for community water systems if the State has a program to address the more significant risk from radon in indoor air.  Since an MCL has not been finalized, this report considers the lowest proposed MCL of 300 pCi/L, in an effort to be more conservative and protective of public health.  Radon-222 has been detected at levels above 50% of this more conservative proposed MCL in 26 of the 34 community systems that have tested for this contaminant (Table 6b).  The available data indicates that radon was detected in wells drawing from the Aquia, Piney Point, and one well in the Patapsco Aquifer, respectively.  No other radiological contaminants were detected at levels of concern for the community water systems in this report.

Volatile Organic Compounds (VOCs)

No VOCs were detected at levels above 50% of their respective MCLs for any of the community water systems in this report. Twelve systems had VOCs detected at very low levels well below their respective MCLs.  The detections include the compounds dichlorobenzene, ethylbenzene, xylenes, toluene, monochlorobenzene, methylene chloride, 1,2,4-trichlorobenzene, and carbon tetrachloride.  However, subsequent sampling events at all but one of the systems has shown no detects of these compounds.  Persimmon Hills had a low level detect of total xylenes of 1.1 ppb in 1999. The MCL for total xylenes is 10,000 ppb.  No other VOCs were detected from available sampling results of the remaining 23 systems.

Synthetic Organic Compounds (SOCs)

The only SOC detected above the 50% threshold was Di (2-Ethylhexyl) Phthalate (Table 6d).  This contaminant was found in laboratory blank samples accompanying this detection, and therefore should not affect actual water quality of the system.  This SOC was also detected at low levels well below its respective MCL of 6 ppb at 11 other systems from this report.     

Dalapon was detected from one set of available sampling data for Lexington Park Plant 19, Saint Mary’s College Plant 3, and Hills Trailer Park, at levels many times less than its MCL of 200 ppb.  Dalapon has been reported in many samples at very low levels across the state, and its reported detections may also be an artifact of the testing procedure.  No other SOCs were detected from available sampling results for the remaining systems.     

Microbiological Contaminants

Ground water under the direct influence of surface water (GWUDI) raw water testing is not required for any of the 35 community water systems in Saint Mary’s County, since the wells draw water from confined aquifers that are considered not at risk to surface water influence.  For integrity purposes, however, raw water bacteriological testing was completed for the wells operated by METCOM as part of their funded wellhead protection study.  With the exception of one positive dry weather sample collected at Lexington Park’s Peggs Road Plant at 5-mpn/100 ml (most probable number per 100 milliliter), all other GWUDI sample results were negative for the presence of coliform bacteria.  The numbers of coliform colonies found in a 100-milliliter sample are extrapolated in the lab to determine “the most probable number” over the entire sample.  Wet weather GWUDI results were coliform negative at the Peggs Road Plant.

All of the community systems have monthly routine bacteriological samples that are collected as required by the Safe Drinking Water Act.  Since 34 of the water systems disinfect their water at the treatment plants, the finished water data is not indicative of the quality of raw water directly from the well.  Total coliform bacteria are not pathogenic, but are used as an indicator organism for other disease-causing microorganisms.  Six systems had positive total coliform results in at least one sample, and in four instances, follow-up samples were found to have total coliform present (Table 7).  A positive total and fecal coliform result was reported in June 2002 at Country Lakes.  However, ten repeat samples taken since then have shown no positive total or fecal coliform detections.  In addition, several repeat samples taken at the remaining five systems have had no positive coliform detects.  No positive coliform results were reported from the remaining 29 community systems from samples collected monthly since 1997.    

Susceptibility Analysis

The wells serving the Saint Mary’s County community water systems draw water from confined aquifers.  Confined aquifers are naturally protected from land use activities at the ground surface due to the confining layers that provide a barrier for water movement from the surface into the aquifers below.  A properly constructed well with the casing extended to the confined aquifer and with sufficient grout should be well protected from contamination at the land surface.  A contaminant released in a confined WHPA setting must travel through either the annular space of a poorly grouted well, an unused improperly abandoned well, or an underground injection well drilled into the confined aquifer to potentially contaminate the aquifer.  Confined aquifers are recharged very slowly from the water stored in the confining unit above, and from precipitation that infiltrates into the formation where it reaches the ground surface.  Figures 2 & 3 illustrate the outcrop area of the Aquia aquifer (the area where it reaches the ground surface).  Note that this area is in Prince George’s, and Anne Arundel Counties respectively, some 20 plus miles north of the northern-most Saint Mary’s County border. Generally, water stored in confined aquifers has traveled great distances from its origin at the ground surface.  Based on simulated 1995 pumpage under steady-state conditions, a contaminant that enters the outcrop area of the Aquia aquifer, traveling at the same rate as ground water, would take thousands of years to be withdrawn from an Aquia well pumping in Lexington Park (Achmad & Hansen, 1997).  Likewise, the vertical travel-time of a contaminant through the very low permeability confining layers, to ultimately reach the Aquia aquifer would also take thousands of years.

Some contaminants like radon-222 and the elements arsenic and iron are naturally occurring in the aquifers, and may reach concentrations that pose a risk to the water supply.  This is generally more problematic in confined aquifer settings than contaminants at the land surface.

              The susceptibility analysis of the individual water supplies to each group of contaminants has been completed based on the following criteria: 1) the presence of potential contaminant sources within the WHPA, 2) water quality data, 3) well integrity and 4) the aquifer conditions. Table 8 summarizes the susceptibility of each of the 35 systems covered in this report to each of the groups of contaminants.

Inorganic Compounds

EPA lowered the MCL for arsenic from 0.050 ppm to 0.010 ppm on February 22, 2002.  The regulations will be effective for new sources on or after January 23, 2004.  Existing water systems must meet the new standard by January 23, 2006.  Arsenic is a naturally occurring element that is present in the aquifer material of 27 systems at levels greater than 50% of this new MCL standard (Table 6a).  Based on a preliminary study by MGS, the highest arsenic concentrations from the major Coastal Plain aquifers in Maryland are from the Aquia aquifer (Bolton, 2003).  The arsenic data in this report is consistent with this finding.      

From available data, three of the twenty-seven systems including two that draw water from the Patapsco and Piney Point aquifers respectively, had one arsenic detection of concern only, and three to five subsequent samples showed no arsenic detects (Table 6a).  Therefore, these three systems were determined not susceptible to arsenic contamination.  Based on the natural occurrence of arsenic at certain locations within the Aquia aquifer, and their presence at or above 50% of this newly established MCL, twenty-four systems are susceptible to arsenic.  The arsenic levels of the remaining eight systems were below the newly established 50% MCL threshold, and therefore are not susceptible to this contaminant (Table 8).

Fluoride is a naturally occurring element that is present in aquifer material at low levels at all of the systems in this report.  As water moves through the aquifer sands, elements such as fluoride are leached into the water.  Only one fluoride sample was detected above 50% of the 4 ppm MCL at Patuxent Naval Air Station Plant 3   (Table 6a).  A subsequent sample at this plant was below the 50% MCL threshold.  Based on available sampling data, the thirty-five systems in this report were determined not susceptible to this contaminant.

Chromium is also a naturally deposited element present in aquifer material. It may also be discharged from steel and pulp mills.  It was detected in only one sample at Patuxent Naval Air Station Plant 19 in 1999, and was not detected again from a subsequent sample.  Therefore, the system was determined not to be susceptible to this contaminant.    

Iron is a naturally occurring element that was detected in aquifer material at or above the secondary standard at two systems, and above 50% of the secondary standard at four other systems from this report.  The secondary standard for iron is 0.3 ppm.  Other iron results from these six systems were below levels of concern, or not detected.  Excessive iron levels can cause taste, color, and odor problems in drinking water as well as iron bacteria build-up around well screens.    No aquifer correlation can be deduced from these results as iron was detected at varying levels from wells drawing from all of the aquifers described in this report. 

Based on available water quality data, all of the systems in this report were determined not susceptible to regulated inorganic compounds other than arsenic.

Radionuclides

An MCL for radon-222 has not been adopted yet for Maryland. However, the U.S. EPA is proposing an MCL of 300 pCi/L or an alternative of 4000 pCi/L for drinking water if the State has a program to reduce the more significant risk from radon in indoor air, which is the primary health concern.  Radon is present in 26 of the 34 systems that have tested for this contaminant at levels above 50% of the more conservative proposed MCL of 300 pCi/L (Table 6b).  Saint Mary’s College and Garrett Park Mobile Home Park had radon results over 1,000 pCi/L (Table 6b). 

Radon is present in ground water due to the natural radioactive decay of uranium bearing minerals in the sediment that makes up the aquifer material.  The EPA has information on proposed regulations for radon in indoor air and drinking water on their web site (http://www.epa.gov/safewater/radon.html).  The systems in Table 6b may be susceptible to radon-222 if the more conservative MCL of 300 pCi/L is adopted.  No radon data was available for Southgate, and therefore, the susceptibility to this contaminant could not be determined at this time (Table 8).  No other radiological contaminants were detected at levels of concern for any of the community systems in this report based on available sampling data.

Volatile Organic Compounds

Volatile Organic Compounds (VOCs) have not been detected at 50% of their respective MCLs in any of the community water systems in this report.  Facilities that have potential point sources of VOCs (e.g. USTs) are located within or near several WHPAs from this report (Appendix C).  However, none of these sites should present a water quality threat to the supply wells due to the natural confining clay layers that protect the aquifers from contamination that occurs near the ground surface.  Contamination from these sites should threaten the water quality of the shallow, unconfined aquifers only.

Based on the water quality data, well integrity, and confined aquifer characteristics, the thirty-five systems from this report were determined not susceptible to VOCs. 

Synthetic Organic Compounds

The sources of SOCs to ground water include point and non-point sources.  Non-point sources include pesticides, and herbicides applied to agricultural fields, and residential lawns. 

The only contaminant in this group detected above 50% of the MCL was di (2-ethylhexyl) phthalate, which was attributed to its presence in laboratory blank samples, and therefore does not represent actual water quality (Table 6c). The only other SOC that was detected at levels well below its respective MCL of 200 ppb was dalapon.  This contaminant was detected once from one set of available sampling results at Lexington Park Plant 19, Saint Mary’s College, and Hills Trailer Park respectively.  Dalapon is a herbicide used on orchards, beans, lawns, and road/railway lines.  As stated previously in the Water Quality Section, dalapon has been reported in many samples at very low levels across the state, and its reported detections may be an artifact of the testing procedure.      

A confined aquifer waiver has been issued for synthetic organic compounds.  The waiver permits confined systems to reduce the sampling frequency of SOCs to once every 12 years.  Based on the available water quality data, and confined aquifer characteristics, all of the systems in this report were determined not susceptible to SOC contamination.  

Microbiological Contaminants

Water stored in confined aquifers has traveled great distances through the naturally filtering sands, and is considered “ very old”.  Microbial organisms in ground water generally have a maximum survival time of one year, and therefore they would have long since perished in a confined aquifer setting.  Additionally, confined aquifer wells are generally well protected from microbiological contaminants originating from the ground surface due to the overlying protective confining layers.   

Raw water monitoring for microbiological contaminants is not required for systems drawing water from confined aquifers because they are considered naturally protected from sources of pathogens at the land surface.  However, dry and wet weather raw water bacteriological testing was completed as part of the METCOM funded wellhead protection study to assess the integrity of their production wells.  Based on the GWUDI results, the overall integrity of the wells is good.  The Lexington Park Peggs Road Well had one positive dry weather coliform detect, but a wet weather sample, which should be more indicative of surface water influence, showed no coliform present.

Six of the systems in this report had routine positive coliform results in at least one sample (Table 7).  This does not imply, however, that the wells of these systems are susceptible to bacteriological contaminants from the aquifer source.  There are numerous ways that bacteria can enter a water system despite raw water being free of bacteria.  They may include any of the following: damaged or improperly grouted well casing, improperly sealed well cap that allows insect or rodent intrusion, damaged or improperly sealed electrical conduit, damaged or improperly installed pitless adaptor, cracked distribution piping, improperly screened air vent, cracks or damage to storage tank structures, improper flushing of the distribution system etc.  Several repeat samples taken from the six community systems since have shown no positive coliform results.          

Based on available sampling data, and confined aquifer characteristics, the source water at each of the 35 community systems in this report is not susceptible to microbiological contaminants. 

Management of the Source Water Assessment Area

With the information contained in this report, the individual community water system owners as well as the Saint Mary’s County government are in a position to protect their water supplies by staying aware of the areas delineated for source water protection and evaluating future development and land use planning.  Specific management recommendations for consideration are listed below.  The following recommendations are intended for individual water systems.

Public Awareness and Outreach

·        The Consumer Confidence Report should list that this report is available to the general public through their county library, or by contacting the water system operator or MDE.

Monitoring

·        Systems should continue to monitor for all Safe Drinking Water Act contaminants as required by MDE.

·        Annual raw water bacteriological testing is a good check on well integrity. 

Contingency Plan

·        All water system owners should have a Contingency Plan for their water system.  COMAR 26.04.01.22 requires all community water systems to prepare and submit for approval a plan for providing a safe and adequate drinking water supply under emergency conditions.

Contaminant Source Inventory Updates/ Inspections

·        Water system owners should conduct its own survey of their wellhead protection areas to ensure that there are no additional potential sources of contamination.  Updated records of new development within the WHPAs should be maintained.

·        Water system operators should have a program for periodic inspections and maintenance of the supply wells to ensure their integrity and to protect the aquifers from contamination. 

·        Unused wells with no potential for use in the future should be properly abandoned and sealed according to current State well construction standards.  The WSP encourages METCOM to follow through with the recommendation of properly abandoning and sealing unused wells as was outlined in their Wellhead Protection Program Report (METCOM, 2003).  

·        The community systems should work with the Saint Mary’s County Health Department to ensure that there are no other unused wells within the respective WHPAs.  An improperly abandoned well may provide a direct route for ground water contamination to an aquifer.

Changes in Use

·        Water system owners are required to notify the MDE Water Supply Program if new wells are to be added or if they wish to increase their water useage.  The addition of new wells or an increase in pumpage of the existing wells may require revisions to the WHPA.

REFERENCES

Achmad, Grufron, and Fewster, Brandon T., 2003, Delineation of Zones of Transport for
        Public-Supply Wells in St. Mary’s County, Maryland: Maryland Geological Survey
        Open-File Report No. 2003-02-16, 82 p.

Achmad, Grufron, and Hansen, Harry J., 1997, Hydrogeology, Model Simulation, and
        Water-Supply Potential of the Aquia and Piney Point-Nanjemoy Aquifers in Calvert
        and Saint Mary’s Counties, Maryland: Maryland Geological Survey Report of
        Investigations No. 64, 197 p.

Bolton, David W., 2003, Interim Report: Summary of Ground-Water Arsenic
       Concentrations in the Major Aquifers of the Maryland Coastal Plain: Maryland
       Geological Survey, Resource Assessment Service, Maryland Department of Natural
       Resources, 23 p.

Chapelle, Francis H., and Drummond, David D., 1983, Hydrogeology, Digital
       Simulation, and Geochemistry of the Aquia and Piney Point-Nanjemoy Aquifer
       System in Southern Maryland: Maryland Geological Survey Report of Investigations
       No. 38, 100 p.

Committee on Health Risks of Exposure to Radon, 1999, Health Effects of Exposure
 to Radon: BEIR VI,  (http://www.epa.gov/iaq/radon/beirvi1.html).

Martin, Robert O.R., and Ferguson, H.F., 1953, The Water Resources of St. Mary’s
 County: Department of Geology, Mines, and Water Resources State of Maryland
 Bulletin 11, 195 p.

Maryland Association of Counties, 2001/2002 Directory of County Officials, 419 p.

Maryland Department of the Environment, Water Supply Program, 1999, Maryland's

       Source Water Assessment Plan, 36 p.

Morris, D.A., and Johnson, A.I., 1967, Summary of Hydrologic and Physical Properties
       of Rock and Soil Materials as Analyzed by the Hydrologic Laboratory of the U.S.
       Geological Survey: U.S. Geological Survey Water-Supply Paper 1839-D, D42 p.

Saint Mary’s County Metopolitan Commission Well Head Protection Program, 2003

Water Supply Division, Planning and Engineering Section, 1987, The Quantity and
       Natural Quality of Ground Water in Maryland: Maryland Department of Natural
       Resources Water Resources Administration, 150 p.

Other Sources of Data

Water Appropriation and Use Permits

Public Water Supply Sanitary Survey Inspection Reports

MDE Water Supply Program Oracle® Database

MDE Waste Management Sites Database

Base Map from St. Mary’s County Metropolitan Commission Digital File 1:100,000

Department of Natural Resources Digital Orthophoto Quarter Quadrangles

USGS Topographic 7.5-Minute Quadrangles

Tables

Table 1. Well Information

Table 2. Generalized Stratigraphy of Southern Maryland

                                                Table 3. Parameters Used for Florida Method WHPA

                                                               Delineations

Table 4. Treatment Methods

Table 5. Total Water Quality Samples

Table 6. Water Quality Data

Table 7. Bacteriological Samples

Table 8. Susceptibility Analysis Summary

Figures

                        Figure 1.      Wellhead Protection Areas for Community Water Systems

                                             (In Pocket) 

                        Figure 2.      Approximate Thickness of the Aquia Aquifer

                        Figure 3.      Approximate Altitude of the Top of the Aquia Aquifer

                        Figure 4.      Approximate Thickness of the Piney Point Aquifer

                        Figure 5.      Approximate Altitude of the Top of the Piney Pt. Aquifer

APPENDICES

Appendix A

           Report of underground injection control inspections with

Notice of Violations (NOVs) or with pending issues from MDE Ground Water Permits Program

Appendix B

General information of sites with known soil, or shallow aquifer

ground water contamination concerns near St. Mary’s Co.

Community Water Systems from MDE Waste Management Admin.

Appendix C

Report of cases within or near WHPAs from MDE Oil Control Program

Appendix D

Executive Summaries for Community Systems
 

Executive Summary BRETON BAY

            The Maryland Department of the Environment’s Water Supply Program (WSP) has conducted a Source Water Assessment for the thirty-five community water systems in Saint Mary’s County, including the Breton Bay community supply.  The required components of this report as described in Maryland’s Source Water Assessment Program (SWAP) are 1) delineation of an area that contributes water to the source, 2) identification of potential sources of contamination within the areas, and 3) determination of the susceptibility of the water supply to contamination.  Recommendations for protecting the drinking water supply conclude this report.

            The water supply sources of the community systems in Saint Mary’s County are naturally protected confined aquifers of the Atlantic Coastal Plain physiographic province.  The Breton Bay water system is currently using two wells that pump water from the Aquia Formation.  The Wellhead Protection area was delineated by the WSP using U.S. EPA’s approved methods specifically designed for this source.

            Potential point sources of contamination within and near the assessment areas were noted from field inspections and contaminant inventory databases.  Well information and water quality data were also reviewed.  Figure 1 shows the wellhead protection areas for all of the community water systems.

            The susceptibility analysis is based on a review of the existing water quality data for each water system, the presence of potential sources of contamination in the individual assessment areas, well integrity, and aquifer characteristics.  It was determined that the Breton Bay water supply is not susceptible to contaminants originating at the land surface due to the protected nature of confined aquifers.  The water supply is susceptible to naturally occurring arsenic (based on the new EPA standard).
 

EXECUTIVE SUMMARY CEDAR COVE

            The Maryland Department of the Environment’s Water Supply Program (WSP) has conducted a Source Water Assessment for the thirty-five community water systems in Saint Mary’s County, including the Cedar Cove community supply.  The required components of this report as described in Maryland’s Source Water Assessment Program (SWAP) are 1) delineation of an area that contributes water to the source, 2) identification of potential sources of contamination within the areas, and 3) determination of the susceptibility of the water supply to contamination.  Recommendations for protecting the drinking water supply conclude this report.

            The water supply sources of the community systems in Saint Mary’s County are naturally protected confined aquifers of the Atlantic Coastal Plain physiographic province.  The Cedar Cove water system is currently using two wells that pump water from the Aquia Formation.  The Wellhead Protection area was delineated by the WSP using U.S. EPA’s approved methods specifically designed for this source.

            Potential point sources of contamination within and near the assessment areas were noted from field inspections and contaminant inventory databases.  Well information and water quality data were also reviewed.  Figure 1 shows the wellhead protection areas for all of the community water systems.

           The susceptibility analysis is based on a review of the existing water quality data for each water system, the presence of potential sources of contamination in the individual assessment areas, well integrity, and aquifer characteristics.  It was determined that the Cedar Cove water supply is not susceptible to contaminants originating at the land surface due to the protected nature of confined aquifers.  The water supply is susceptible to naturally occurring arsenic (based on the new EPA standard).  The susceptibility of the water supply to radon-222, a naturally occurring element, will depend on the final MCL that is adopted for this contaminant.

Executive Summary LEONARDTOWN

            The Maryland Department of the Environment’s Water Supply Program (WSP) has conducted a Source Water Assessment for the thirty-five community water systems in Saint Mary’s County, including the Leonardtown community supply.  The required components of this report as described in Maryland’s Source Water Assessment Program (SWAP) are 1) delineation of an area that contributes water to the source, 2) identification of potential sources of contamination within the areas, and 3) determination of the susceptibility of the water supply to contamination.  Recommendations for protecting the drinking water supply conclude this report.

            The water supply sources of the community systems in Saint Mary’s County are naturally protected confined aquifers of the Atlantic Coastal Plain physiographic province.  The Leonardtown water system is currently using three wells that pump water from the Aquia Formation.  The Wellhead Protection area was delineated by the WSP using U.S. EPA’s approved methods specifically designed for this source.

            Potential point sources of contamination within and near the assessment areas were noted from field inspections and contaminant inventory databases.  Well information and water quality data were also reviewed.  Figure 1 shows the wellhead protection areas for all of the community water systems.

            The susceptibility analysis is based on a review of the existing water quality data for each water system, the presence of potential sources of contamination in the individual assessment areas, well integrity, and aquifer characteristics.  It was determined that the Leonardtown water supply is not susceptible to contaminants originating at the land surface due to the protected nature of confined aquifers.  The water supply is susceptible to naturally occurring arsenic (based on the new EPA standard).  The susceptibility of the water supply to radon-222, a naturally occurring element, will depend on the final MCL that is adopted for this contaminant.

Executive Summary LEXINGTON PARK

            The Maryland Department of the Environment’s Water Supply Program (WSP) has conducted a Source Water Assessment for the thirty-five community water systems in Saint Mary’s County, including the Lexington Park community supply.  The required components of this report as described in Maryland’s Source Water Assessment Program (SWAP) are 1) delineation of an area that contributes water to the source, 2) identification of potential sources of contamination within the areas, and 3) determination of the susceptibility of the water supply to contamination.  Recommendations for protecting the drinking water supply conclude this report.

            The water supply sources of the community systems in Saint Mary’s County are naturally protected confined aquifers of the Atlantic Coastal Plain physiographic province.  The Lexington Park water system is currently using twenty-two wells from twenty treatment plants that pump water from the Aquia, Piney Point, and Patapsco Formations respectively.  The Wellhead Protection areas were delineated by the WSP using U.S. EPA’s approved methods specifically designed for each source.

            Potential point sources of contamination within and near the assessment areas were noted from field inspections and contaminant inventory databases.  Well information and water quality data were also reviewed.  Figure 1 shows the wellhead protection areas for all of the community water systems.

           The susceptibility analysis is based on a review of the existing water quality data for each water system, the presence of potential sources of contamination in the individual assessment areas, well integrity, and aquifer characteristics.  It was determined that the Lexington Park water supply is not susceptible to contaminants originating at the land surface due to the protected nature of confined aquifers.  The wells pumping water from the Aquia Formation (Plants 1, 2, 6-10, 12, 16-18, 20, & 21) are susceptible to naturally occurring arsenic (based on the new EPA standard).  The susceptibility of the water supply to radon-222, a naturally occurring element, will depend on the final MCL that is adopted for this contaminant.

Executive Summary KING-KENNEDY

             The Maryland Department of the Environment’s Water Supply Program (WSP) has conducted a Source Water Assessment for the thirty-five community water systems in Saint Mary’s County, including the King-Kennedy community supply.  The required components of this report as described in Maryland’s Source Water Assessment Program (SWAP) are 1) delineation of an area that contributes water to the source, 2) identification of potential sources of contamination within the areas, and 3) determination of the susceptibility of the water supply to contamination.  Recommendations for protecting the drinking water supply conclude this report.

            The water supply sources of the community systems in Saint Mary’s County are naturally protected confined aquifers of the Atlantic Coastal Plain physiographic province.  The King-Kennedy water system is currently using two wells that pump water from the Aquia Formation.  The Wellhead Protection area was delineated by the WSP using U.S. EPA’s approved methods specifically designed for this source.

            Potential point sources of contamination within and near the assessment areas were noted from field inspections and contaminant inventory databases.  Well information and water quality data were also reviewed.  Figure 1 shows the wellhead protection areas for all of the community water systems.

           The susceptibility analysis is based on a review of the existing water quality data for each water system, the presence of potential sources of contamination in the individual assessment areas, well integrity, and aquifer characteristics.  It was determined that the King-Kennedy water supply is not susceptible to contaminants originating at the land surface due to the protected nature of confined aquifers.  The water supply is susceptible to naturally occurring arsenic (based on the new EPA standard).  The susceptibility of the water supply to radon-222, a naturally occurring element, will depend on the final MCL that is adopted for this contaminant.

Executive Summary MOUNT PLEASANT WATER CO.

            The Maryland Department of the Environment’s Water Supply Program (WSP) has conducted a Source Water Assessment for the thirty-five community water systems in Saint Mary’s County, including the Mount Pleasant Water Company community supply.  The required components of this report as described in Maryland’s Source Water Assessment Program (SWAP) are 1) delineation of an area that contributes water to the source, 2) identification of potential sources of contamination within the areas, and 3) determination of the susceptibility of the water supply to contamination.  Recommendations for protecting the drinking water supply conclude this report.

            The water supply sources of the community systems in Saint Mary’s County are naturally protected confined aquifers of the Atlantic Coastal Plain physiographic province.  The Mount Pleasant water system is currently using two wells that pump water from the Aquia Formation.  The Wellhead Protection area was delineated by the WSP using U.S. EPA’s approved methods specifically designed for this source.

                Potential point sources of contamination within and near the assessment areas were noted from field inspections and contaminant inventory databases.  Well information and water quality data were also reviewed.  Figure 1 shows the wellhead protection areas for all of the community water systems.

           The susceptibility analysis is based on a review of the existing water quality data for each water system, the presence of potential sources of contamination in the individual assessment areas, well integrity, and aquifer characteristics.  It was determined that the Mount Pleasant water supply is not susceptible to contaminants originating at the land surface due to the protected nature of confined aquifers.  The water supply is susceptible to naturally occurring arsenic (based on the new EPA standard).  The susceptibility of the water supply to radon-222, a naturally occurring element, will depend on the final MCL that is adopted for this contaminant.

Executive SummarY SAINT CLEMENTS SHORES

            The Maryland Department of the Environment’s Water Supply Program (WSP) has conducted a Source Water Assessment for the thirty-five community water systems in Saint Mary’s County, including the Saint Clements Shores community supply.  The required components of this report as described in Maryland’s Source Water Assessment Program (SWAP) are 1) delineation of an area that contributes water to the source, 2) identification of potential sources of contamination within the areas, and 3) determination of the susceptibility of the water supply to contamination.  Recommendations for protecting the drinking water supply conclude this report.

            The water supply sources of the community systems in Saint Mary’s County are naturally protected confined aquifers of the Atlantic Coastal Plain physiographic province.  The Saint Clements Shores water system is currently using one well that pumps water from the Aquia Formation.  The Wellhead Protection area was delineated by the WSP using U.S. EPA’s approved methods specifically designed for this source.

                Potential point sources of contamination within and near the assessment areas were noted from field inspections and contaminant inventory databases.  Well information and water quality data were also reviewed.  Figure 1 shows the wellhead protection areas for all of the community water systems.

            The susceptibility analysis is based on a review of the existing water quality data for each water system, the presence of potential sources of contamination in the individual assessment areas, well integrity, and aquifer characteristics.  It was determined that the Saint Clements Shores water supply is not susceptible to contaminants originating at the land surface due to the protected nature of confined aquifers.  The water supply is susceptible to naturally occurring arsenic (based on the new EPA standard).  The susceptibility of the water supply to radon-222, a naturally occurring element, will depend on the final MCL that is adopted for this contaminant.

Executive Summary Saint Mary’s College

           The Maryland Department of the Environment’s Water Supply Program (WSP) has conducted a Source Water Assessment for the thirty-five community water systems in Saint Mary’s County, including the Saint Mary’s College community supply.  The required components of this report as described in Maryland’s Source Water Assessment Program (SWAP) are 1) delineation of an area that contributes water to the source, 2) identification of potential sources of contamination within the areas, and 3) determination of the susceptibility of the water supply to contamination.  Recommendations for protecting the drinking water supply conclude this report.

            The water supply sources of the community systems in Saint Mary’s County are naturally protected confined aquifers of the Atlantic Coastal Plain physiographic province.  The Saint Mary’s College water system is currently using three wells that pump water from the Aquia Formation.  The Wellhead Protection areas were delineated by the WSP using U.S. EPA’s approved methods specifically designed for this source.

Potential point sources of contamination within and near the assessment areas were noted from field inspections and contaminant inventory databases.  Well information and water quality data were also reviewed.  Figure 1 shows the wellhead protection areas for all of the community water systems.

           The susceptibility analysis is based on a review of the existing water quality data for each water system, the presence of potential sources of contamination in the individual assessment areas, well integrity, and aquifer characteristics.  It was determined that the Saint Mary’s College water supply is not susceptible to contaminants originating at the land surface due to the protected nature of confined aquifers.  The water supply is susceptible to naturally occurring arsenic (based on the new EPA standard).  The susceptibility of the water supply to radon-222, a naturally occurring element, will depend on the final MCL that is adopted for this contaminant.

Executive Summary BIRCH MANOR

            The Maryland Department of the Environment’s Water Supply Program (WSP) has conducted a Source Water Assessment for the thirty-five community water systems in Saint Mary’s County, including the Birch Manor community supply.  The required components of this report as described in Maryland’s Source Water Assessment Program (SWAP) are 1) delineation of an area that contributes water to the source, 2) identification of potential sources of contamination within the areas, and 3) determination of the susceptibility of the water supply to contamination.  Recommendations for protecting the drinking water supply conclude this report.

            The water supply sources of the community systems in Saint Mary’s County are naturally protected confined aquifers of the Atlantic Coastal Plain physiographic province.  The Birch Manor water system is currently using two wells that pump water from the Aquia Formation.  The Wellhead Protection area was delineated by the WSP using U.S. EPA’s approved methods specifically designed for this source.

                Potential point sources of contamination within and near the assessment areas were noted from field inspections and contaminant inventory databases.  Well information and water quality data were also reviewed.  Figure 1 shows the wellhead protection areas for all of the community water systems.

           The susceptibility analysis is based on a review of the existing water quality data for each water system, the presence of potential sources of contamination in the individual assessment areas, well integrity, and aquifer characteristics.  It was determined that the Birch Manor water supply is not susceptible to contaminants originating at the land surface due to the protected nature of confined aquifers.  The water supply is susceptible to naturally occurring arsenic (based on the new EPA standard).  The susceptibility of the water supply to radon-222, a naturally occurring element, will depend on the final MCL that is adopted for this contaminant.

Executive Summary ROLLING ACRES

           The Maryland Department of the Environment’s Water Supply Program (WSP) has conducted a Source Water Assessment for the thirty-five community water systems in Saint Mary’s County, including the Rolling Acres community supply.  The required components of this report as described in Maryland’s Source Water Assessment Program (SWAP) are 1) delineation of an area that contributes water to the source, 2) identification of potential sources of contamination within the areas, and 3) determination of the susceptibility of the water supply to contamination.  Recommendations for protecting the drinking water supply conclude this report.

            The water supply sources of the community systems in Saint Mary’s County are naturally protected confined aquifers of the Atlantic Coastal Plain physiographic province.  The Rolling Acres water system is currently using two wells that pump water from the Aquia Formation.  The Wellhead Protection area was delineated by the WSP using U.S. EPA’s approved methods specifically designed for this source.

            Potential point sources of contamination within and near the assessment areas were noted from field inspections and contaminant inventory databases.  Well information and water quality data were also reviewed.  Figure 1 shows the wellhead protection areas for all of the community water systems.

           The susceptibility analysis is based on a review of the existing water quality data for each water system, the presence of potential sources of contamination in the individual assessment areas, well integrity, and aquifer characteristics.  It was determined that the Rolling Acres water supply is not susceptible to contaminants originating at the land surface due to the protected nature of confined aquifers.  The water supply is susceptible to naturally occurring arsenic (based on the new EPA standard).  The susceptibility of the water supply to radon-222, a naturally occurring element, will depend on the final MCL that is adopted for this contaminant.

Executive Summary WICOMICO SHORES

           The Maryland Department of the Environment’s Water Supply Program (WSP) has conducted a Source Water Assessment for the thirty-five community water systems in Saint Mary’s County, including the Wicomico Shores community supply.  The required components of this report as described in Maryland’s Source Water Assessment Program (SWAP) are 1) delineation of an area that contributes water to the source, 2) identification of potential sources of contamination within the areas, and 3) determination of the susceptibility of the water supply to contamination.  Recommendations for protecting the drinking water supply conclude this report.