The Greater Fallston Association, Inc. extends its thanks to the numerous local and national environmental consultants, hydrogeologists, academicians as well as community experts for donating their time and expertise in analyzing the data presented in the ExxonMobil Site Assessment Reports of October 8, 2004 (SAROct2004) and March 22, 2005 (SARMar2005).

The Maryland Department of the Environment (MDE) is charged with protecting the health, safety and welfare of the citizens of Maryland. Given that the aquifer of the Uppercrossroads region is the only source of potable water for the residents of the area, it is vital that the MDE be protective of the interests of the community they are designed to serve. The financial impact alone of an incorrect adverse decision against the interests of the community would be in the order of 5 to 10 million dollars, out-of pocket, over the next 10 to 20 years just to insure a clean uncontaminated water supply to the affected households. (SECTION 12 “COMMUNITY WATER”)

In response to the historical elevations of methyl-tertiary-butyl-ether (MTBE) at the ExxonMobil station dating back to 1990 and the occurrence of a significant release of MTBE in 2003 extending into 2004, the MDE charged ExxonMobil to conduct an investigation to determine the extent of contamination from the ExxonMobil station site. This included a comprehensive assessment of the underlying geology; the determination of groundwater, depth, flow rate, direction and storage capacity in the surrounding aquifer; and the measurement of MTBE levels and other volatile organic chemicals (VOCs) in and around the ExxonMobil site, including the surrounding community.

From a scientific standpoint, the conclusions of ExxonMobil’s report are suspect, because the design of the study was built around a single hypothesis: that groundwater in the bedrock aquifer only flows to the southwest at an infinitesimally slow rate. With this limited perspective, ExxonMobil restricted its investigation to substantiate their foregone conclusion.

As will be detailed in this Comprehensive Review, the design of ExxonMobil’s study was flawed from the very beginning, which lead to an inaccurate site conceptual model and, consequently, broad and inaccurate assumptions regarding the transmissivity and storage capacity of the regional aquifer. At best, the conclusions from their investigation are “well specific”, not “area-wide specific”.

Upon extensive review of the data provided by ExxonMobil, as well as additional evidence not presented in ExxonMobil’s report, we present a strong argument demonstrating that the ExxonMobil site at Uppercrossroads, Maryland is the epicenter of a massive MTBE vapor release that has migrated into the regional aquifer and contaminated the private supply wells in the current study area and beyond.

SECTION 2: THE SOIL

1. General

As will be detailed below, review of the boring logs of monitoring wells (MWs) 1 through 27 (SAROct2004, Appendix M) and MWs 28 through 33 (SARMar2005, Appendix F) revealed the following inconsistencies in the soil descriptions of MWs 1 through 4 drilled in 2003 and MWs 5 through 33 drilled in 2004.

First, the boring logs in 2004 do not even indicate the presence of fill that would be present in a developed area. This is a minor notation, but important to establish the accuracy of the soil descriptions to follow.

Second, saprolite, commonly referred to in the field as “rotten rock”, is weathered bedrock in which fine fabrics are retained. At times, the consultant geologists seem to confuse the natural soil for saprolite or fail to recognize the boundary between fill, soil and true saprolite (assumed to be the “schist”) in their field descriptions. These inconsistencies seriously call in to question the accuracy of the soil descriptions and the validity of any conclusions drawn from these descriptions.

Third, the geologist who logged most of the bedrock monitoring wells did not provide the Unified Soil Classification System designations for the unconsolidated materials on the boring logs. This reflects either a lack of attention to detail or, worse, a bias to a particular conclusion.

2. Comparison of 2003 and 2004 Boring Logs

Monitoring wells 2 and 5 are only 25 feet apart. MW-2 was drilled in 2003, and MW-5 was drilled in 2004. The boring log for MW-2 reveals, “clayey sand”, “sand and silt” and “weathered bedrock (saprolite)” beginning at 30 feet. In contrast when MW-5 was drilled a short distance away, the soil becomes “clay”, “clayey sand” and “silty saprolitic clay” at 25 feet with schist appearing at 49 feet. (FIGURES 1-2) (Reference Appendices 1, 2, and 3 may be used throughout this review to view the locations of monitoring wells and pertinent supply wells.)

Monitoring wells 4 and 11, which are only 50 feet apart, show an even more dramatic redefinition. In 2003, the boring log for MW 4 shows “clayey sand” and “clay and silt” with schist bedrock beginning at 40 feet. Suddenly in 2004, however, the soil for MW-11 converts to pure clay and “silty saprolitic clay” beginning at 11 feet with schist bedrock at 51 feet.

In fact, as FIGURE 1 illustrates, the soil in the entire region in and around the Exxon station has become almost pure clay and “silty saprolitic clay” in the span of a year. Even MW 33 near Green Road. (SARMar2005, Appendix F) shows clay and “silty saprolitic clay”. With each successive monitoring well, the soil horizon shrinks to nearly nothing and everything becomes “silty saprolitic clay”, which is eventually assumed to be saprolite. Significantly, ExxonMobil did not collect soil samples for geotechnical analysis to verify the soil classification. We are only provided with the field descriptions CL (clay, low compressibility), SC (clayey sand), and MH (silt, high compressibility). The inconsistency in soil classification and the lack of independent laboratory confirmation of clay and silt content cast doubt on the validity of the soil descriptions and the subsequent conclusion that the “unconsolidated materials demonstrate very low hydraulic conductivity”. (SARMar2005, p.11) The relationship of the overburden to an aquifer system will be discussed under SECTION 6 “GROUNDWATER”. Nevertheless, it is important to note that the presence and thickness of a confining layer will determine the model used for aquifer test data analysis.

Also included for comparison in FIGURE 1 are the “crude” boring logs from 1981, 1987 and 1991 at the Exxon site. Recognizing that geologists did not record these descriptions, it still indicates the fact the drillers noted a brown silty loam (a United States Department of Agriculture designation) in the subsurface, not clay. APPENDIX A, B, C, D provides well completion reports for adjacent properties, 2401 Baldwin Mill Road (MT&T Bank) and 2719 Fallston Road (Shopping Center).

ExxonMobil would have us believe that the entire property (and its surroundings) is composed of a clay overburden to support their contention that MTBE would not have migrated beyond the confines of the station, because clay retards water flow and its adsorption potential for chemicals such as MTBE is high.

3. Area Percolation

According to the soil descriptions presented by ExxonMobil (SAROct2004, Appendix M), clay is the predominate soil type in the shallow overburden at the ExxonMobil site. Clayey soils demonstrate slow percolation times of 30 minutes or more. Interestingly, the percolation tests performed on the Exxon site in 1975 and 1984 showed percolation times of 4 minutes and 5 minutes respectively, which is characteristic of a silty loam. APPENDIX E-F A fast percolation rate of 2 minutes is characteristic of sandy loams. Indeed, most of the soils in the Fallston area percolate well in the range of 2 to 4 minutes at 5 feet. These percolation times do not comport with the alleged regional presence of a confining clay.

In their report, (SAROct2004), ExxonMobil states that a “locally, … thin perched and/or water table exists just above the weathered bedrock”. To have a perched water table, there must be a confining layer below it. ExxonMobil has not defined the confining layer. The report presents no figures or cross-sections demonstrating the lateral extent or thickness of the confining layer or the perched water table. ExxonMobil’s report (SAROct2004) only presents ill-constructed cross sections that illustrate “fill” versus “silty saprolitic clay”. Stating that the perched water is just above the weathered bedrock confuses matters even further. (SARMar2005, p. 11) By definition, perched water is separated from the water table aquifer by a confining layer. If that is so, then the “silty saprolitic clay” described by ExxonMobil must be the same as “weathered bedrock.” However, ExxonMobil seems to differentiate the two as separate lithologic units.

Simply put, the report fails to establish that the overburden acts as a confining layer given the inconsistent terminology; lack of geotechnical confirmation of the percentage of clay in the overburden; and the lack of cross-sections showing the extent of the so-called confining layer.

4. Soil Vacuum Extraction

Exxon claims that the soil vacuum extraction (SVE) system has been effective in reducing the levels of MTBE as evidenced by the low levels of MTBE in subsequent soil analysis. (SARMar2005, Table 2) The report states that MTBE levels dropped from 4940 ppb in June of 2004 to non-detect (ND) in January 2005. While we are happy to see reductions of MTBE vapors in site soils, we must point out that SVE is not highly effective in clay soils, because of clay’s low permeability and chemically adsorptive properties. Thus, if the overburden at the Exxon site truly consists of clay, the SVE system would not have recovered MTBE vapor completely in less than eight months. Exxon’s conclusion about the effectiveness of SVE at the site thus contradicts its own soil descriptions.

5. Summary

1. ExxonMobil’s describes the soil characteristics of the site as almost entirely clay and “silty saprolitic clay”. This description does not match the descriptions provided in previous borings on the site and is not confirmed by reports on well completion logs of adjacent properties.

2. Soil classifications have not been confirmed by geotechnical analysis.

3. Soil percolations on the ExxonMobil site show fast percolation not characteristic of clayey soils.

4. The documented effectiveness of SVE in removing MTBE from the soils on site is inconsistent with the alleged high clay content in the soil.

SECTION 3: MONITORING WELL DEPTH

1. General

One of the first steps in any hydrogeological investigation of a contaminated aquifer is to determine the depth of the wells in the area, particularly the contaminated ones. Boring logs from wells already drilled provide a wealth of information about the aquifer, and allow geologists to best position monitoring wells and determine potential water-bearing zones in the subsurface. As a general rule, well depths should be converted to elevation above mean sea level (amsl) rather than distance from ground surface, especially in areas with moderate to high topographic relief. Exxon, however, solely uses depth from ground surface. While ExxonMobil’s blanket drilling of bedrock monitoring wells to the same depth of 200 feet “below ground surface” (bgs) may be acceptable in certain sedimentary geologic regimes where the regional dip is negligible and topographic relief is low, it is not appropriate in an area such as Uppercrossroads where the subsurface is composed of folded and fractured metamorphic rock under a variable surface topography. Exxon’s installation of bedrock wells, all to the same depth from surface in this complex geologic formation, does not allow the adequate characterization of the aquifer.

2. Depth Determination

ExxonMobil bored 12 bedrock monitoring wells as part of their site assessment in August and September 2004 and three additional bedrock monitoring wells in late 2004. With exception of MW 10, all were bored to 200 feet bgs. MW 10 was bored to 250 feet bgs (337 feet amsl). FIGURE 3 ExxonMobil acknowledged that the community’s supply well data was not reviewed prior to the construction of the wells in a meeting on November 17^th 2004 with the Greater Fallston Association, Inc. (GFA), MDE, and the Harford County Health Department (HCHD). Roux Associates, Inc. also did not review the community’s supply well boring logs in determining the depth of the bedrock monitoring wells.

3. Community Supply Well Depth Investigation

The GFA obtained all available boring logs for wells in a one-half mile radius of the Exxon site as well as properties greater than a half-mile south of the site. For wells with no boring logs available, the GFA made a direct request to residents for the pertinent information. One hundred and forty eight (148) well boring logs were obtained. Seventy three percent (73%) of the community “well base” elevations were substantially below the “well base” elevations of the ExxonMobil monitoring wells. FIGURE 4 One hundred eight (108) of 148 community wells bottom out at elevations significantly less than 337 feet amsl (the base elevation of ExxonMobil’s deepest well). In addition to the static graphic representation, a 3-D rotational computer generated graphic compares the depth of the community “well bases” with those of the ExxonMobil monitoring wells. One static image from this rotational graphic is presented in FIGURE 5. As the graphic is rotated, it is clear that the ExxonMobil bedrock monitoring wells are shallow compared to the community supply wells. (3-D rotational graphics are available upon request.) As such, they cannot adequately assess the water-bearing zones at depth that supply a majority of the community’s wells. Moreover, these bedrock monitoring wells can provide few meaningful data regarding the relationship between shallow and deep water-bearing zones in the bedrock.

4. Well Yields and Information from Local Well Drillers

Another good source of information about a local aquifer are the drillers that drilled the community’s supply wells. Consultation with different well drilling companies in the Fallston area (Barlow 410-838-6910, Bel Air, Caswell, Inc 410-557-9355, Jarrettsville, Jones 410-692-6981, Jarrettsville) provided important information on the depth of water bearing zones in the Uppercrossroads region. According to the local well drillers, the average well depth was 280-350 feet. In Haddon Hurst, water was not reached until 700 feet bgs; in Delmar Farms, 350-500 feet bgs; and in Franklin’s Chance, 800 feet bgs. The company that drilled the well for 2419 Baldwin Mill Road (Dipasquales) hit water at 500 feet. The drillers quoted the average well yield for the area between 2 and 4 gallons per minute. At a property near the Fire Station (approximately 1 mile west of the ExxonMobil site), a 50-gallon per minute yield was obtained at 655 feet bgs. Although less frequent, area wells have intersected intervals in the deep bedrock yielding 10 gallons per minute.

This information strongly counters the position taken by ExxonMobil that the probability of hitting significant water bearing fractures below 100 feet diminishes dramatically. The fact that private supply wells may be receiving water from upper water bearing zones in the bedrock, which the Exxon monitoring wells do intersect, does not mean that there are no significant water-bearing zones below the 100 foot bgs depth mark. If that were so, only a few wells would be dug so deep.

5. Well Reservoir Depth

ExxonMobil contends that the deep wells in the community were only bored to provide a reservoir of water. If that were true, many community wells would only extend to about 233 feet bgs on average. However, the following analysis demonstrates otherwise. The state of Maryland requires that a well yield 1 gallon per minute and 500 gallons in 2 hours. If we know the average yield of wells in the area and the static water levels, we can calculate the well depth necessary to meet these requirements.

Required depth = (500 gal – [(yield gal/min) x 120 min])/1.5 gal/feet) + static water level

The formula is based on the fact that each foot of well depth provides 1-1/2 gallons of water storage. Yields in the area range from 1 gallon/minute to as high as 8 gallons/minute. Static water level ranges from 40-80 feet. TABLE 1 below provides the range of required well depths calculated with this formula.

TABLE 1 Required Well Depths as a Function of Yield and Static Water Level

Yield (gal/min)	1	2	3	4	5	6
Static water level (Feet)
40 (min)	293	213	133	53	0	0
80 (max)	333	253	173	93	13	0

Assuming and average yield of 2 gallons per minute and a static water level of 60 feet, the required well depth would be 233 feet. From the data collected, 90 of the 148 wells or 61% of community supply wells had well depths that exceeded 233 feet. Even assuming a yield of 1 gallon per minute and 60 feet of static depth, 34 percent, or more than a third, of the community’s supply wells have depths greater than the required well depth.

In conclusion, ExxonMobil’s cursory comment that deep supply wells are bored solely for purposes of establishing a reservoir is unfounded and misleading. Wells are drilled with both purposes in mind: (1) establishing a reservoir for storage and (2) reaching deeper water bearing fracture zones. The fact that deep wells were bored in the Uppercrossroads area supports our contention that water-bearing zones exist as deep as 655 feet bgs in the area.

6. Geophysical Data Confirming Fractures Below 100 feet

ExxonMobil asserts that there are few “fractures capable of transmitting water” below the 100 ft depth. (SARMar2005, p.32) Nevertheless, the geophysical data do not support this conclusion. To begin, the P278 (Morgan well) is only 77 feet deep; therefore, data from this well can imply nothing about the bedrock beyond the 100-foot depth. As for the remaining wells tested, there were data in each well indicating zones of secondary porosity. For instance, the D.R. Horton Lot 33 well exhibited potential water bearing zones at the 156-170 foot bgs interval and at 206 feet bgs. The JD (formerly Wawa) P244 supply well exhibited signs of water bearing zones at the 180-187 foot bgs and the 276-277 foot bgs intervals. There were also indications of water bearing zones at the 120-125 foot bgs, 135-140 foot bgs, 150-165 foot bgs, and 175-190 foot bgs intervals in the monitoring wells tested. These correspond with “soft zones” identified in the boring logs for the monitoring wells. Such soft zones can indicate fractures. It should also be noted that MW-22 was meant to be 200 feet deep, like the rest of the monitoring wells, but it collapsed at 180 feet and was finally set at 150 feet. The most likely cause of this collapse was a major fracture zone. The presence of an extraordinary high level of MTBE in this well and the fact that there was deep collapse is strongly suggestive that this well contained a water-bearing fracture zone near 180 feet.

All of this data provides strong evidence that the folded metamorphic rock in the Uppercrossroads region contains water-bearing fractures extending below 100 feet. ExxonMobil’s conclusion is simply incorrect.

7. Cross-Contamination of Deep Fracture Zones via the Well Boreholes

While most of groundwater may flow in fractures closer to the top of bedrock and these intervals may be the most heavily contaminated, Exxon ignores the risk of contamination of deeper zones via the wells in the area and on the Exxon site. The possibility of cross-contamination via the boreholes of wells drilled through a contaminated zone and into deeper bedrock is well accepted. This is also a significant element of the hydrogeological framework. The presence of so many supply wells extending to deep water-bearing zones in the bedrock creates a leaky aquifer scenario, which affects the analysis of any aquifer test data. This will be discussed further in the section on groundwater and aquifer testing.

8. Summary

1. Monitoring wells were bored without the consideration of available boring logs from local supply wells in the contaminated region.

2. The depth of the monitoring wells was based on total depth below ground surface rather than elevation. Well design based on a comparison of the elevation of “well bases” to contaminated supply wells is the only way to ensure proper assessment of the fracture zones in the bedrock aquifer system.

3. Seventy three percent (73%) of the community’s supply wells are deeper than ExxonMobil’s deepest monitoring well.

4. The depths of the community’s wells are not solely reservoir based.

5. Water bearing fractures in the Uppercrossroads area occur between 100 to 200 feet bgs on average with water bearing fracture zones as deep as 800 feet bgs according to the well drillers for the developments of Haddon Hurst, Franklins Chance and Delmar Farms. Water was not hit until 500 feet for the Dipasquales property. A yield of 50 gallons per minute at 685 feet bgs at a well adjacent to the study area is conclusive evidence of deep aquifers in the study region.

6. ExxonMobil’s geophysical data supports the fact that water bearing fractures occur below 100 feet bgs and even as low 276 feet bgs.

The failure to consider the depths of the existing supply wells in establishing the depths of the monitoring wells and to construct the monitoring wells so as to intersect all the water-bearing zones contributing water to community’s wells is a major flaw in study design. This seriously calls into question the validity of any conclusion regarding groundwater flow in the bedrock aquifer.

SECTION 4: SURFACE ELECTRICAL RESISTIVITY TESTING

In general, ExxonMobil failed to perform a thorough investigation by including areas northwest of the site and to use the surface electrical resistivity profiles to their greatest advantage. The result is a cursory discussion that does not contribute to the greater understanding of the hydrogeological framework of the area around the site. What might have been more useful was a detailed soil investigation on the ExxonMobil site itself that included sampling along the product lines, near the dispensers, in the tank field and near the garage. This was not accomplished.

1. The Northern Transect

ExxonMobil failed to perform any Surface Electrical Resistivity (SER) Testing in the sector northwest of the site. The only test performed north of the station was a transect oriented east to west and located 100 feet north of the Cross Roads Shopping Center. The profile along this transect showed two less resistive zones at the 50-foot and the 70-foot depths. These correspond to the upper and middle units in Exxon’s site conceptual model. Accordingly, MW-25 and MW26 appear to have been located in these areas. However, the casing of MW 25 extends to 61 feet bgs and the casing of MW 26 extends to 40 feet bgs. The setting of the surface casings in these wells is problematic, because the casings in both wells could seal off potential water-bearing zones. Had they not been partially sealed by the casing, these areas of potential conductivity could have provided some evidence regarding groundwater transport in the area north of the site.

2. The Transect behind the ExxonMobil Station building

The results of the SER test for Line E offer striking evidence of a permeable zone in the overburden of the Exxon site. Line E runs southeast to northwest along the back of the ExxonMobil station site, paralleling the “B line” drainage system. FIGURE 6 provides a composite of information from SARMar2005 and illustrates transect lines from the SER tests. There is a markedly less resistive zone extending to the lower limits of depth detection toward the weathered bedrock and competent bedrock that extends 50 to 60 feet below surface. This area courses through the “epicenter” of the contaminant zone. While a low resistivity area can indicate the presence of clay, it also suggests increasing porosity with water saturation and/or dissolved ions in the groundwater. This zone is evidence of a plume on the ExxonMobil site itself, and at the very minimum, lends support to the premise that the overburden is permeable and a probable route for MTBE migration, especially as this area falls under the southerly drainage ditch discussed later in SECTION 6 “STORM WATER DRAINAGE”. This is consistent with the high level of contaminations found in MW 22 and MW 9.

3. Summary

1. A single Surface Electrical Resistivity Test northward above the shopping mall indicated the presence of two areas of low resistivity that were not investigated. The casings for MW 25 and 26 were set too deep to yield meaningful information on the transport of contaminants in the upper unit north of the site.

2. An SER profile located south of the ExxonMobil site revealed an area of low resistivity in close proximity to the contaminant “epicenter” on the ExxonMobil site. These findings support the conclusion that the Exxon station is the source of contamination.

SECTION 5: NORTHERN PROPERTIES AND THE NORTHWEST SECTOR

1. General

ExxonMobil’s investigation and data interpretation is based on the singular hypothesis that groundwater flow in both the overburden and the bedrock is solely towards the southwest. Consequently, ExxonMobil has refused to perform any meaningful investigation of flow to the north of the site.

2. The Strike

[CU1] While the predominant strike in the area is N30^oE to N50^oE, the predominant dip is to the northwest at N25^oW to N35^oW, with a less prominent dip to the southeast at S35^oE. This means that groundwater can flow to the northwest and the southeast. Furthermore, there are a substantial number of northwest trending lineaments and features. Given these data, the northwest sector is a critical area of study. ExxonMobil has refused to even consider studying these sectors in spite of its own data. In line with the ExxonMobil hypothesis, two bedrock wells and zero overburden wells were installed northeast of the site, and no bedrock or overburden monitoring wells were drilled in the quadrant northwest of the site. FIGURE 2

[CU2]

First, the strikes represented in a rose diagram only suggest the probability of the strike direction. Both MW-25 and the Wawa well (P244) are situated on the outer margin of ExxonMobil’s own strike axis as depicted on their rose diagram. (SARMar2005, Figure 7) FIGURE 7 A contaminant will follow the path least resistance, and in a fracture-controlled aquifer system, that path will be a fracture. Locating that fracture line becomes more difficult the further one moves from the “epicenter” as the arc of the potential contaminant paths widens with increasing distance from the epicenter. FIGURE 8 Although MW 26 falls within the axis range, it must be emphasized that the strike axis only represents a probability that the strike will fall at any point in the path of the axis. A relatively short distance away, still within the strike axis zone, might be the predominant water-bearing fracture path.

At the ExxonMobil site there are differentials in MTBE contamination of over 1000 ppb in a 200-foot distance, e.g., MW-22 with 3770 ppb MTBE versus MW-18 with 2 ppb MTBE. FIGURE 9 [CU3] . Thus, it is just as probable that there will be similar MTBE level differentials to the east or west of the P244 supply well or the other monitoring wells and supply wells north of the site.

There are also other potential pathways in the overburden that could have directed groundwater to the northwest. For example, the construction of MD 165 and MD 152 resulted in significant disturbance of the overburden. MTBE could have migrated through the overburden under the roadway. Exxon failed to address this possibility as well as the potential migration of MTBE through the storm water drainage system both to the southeast and the northwest. The storm water drainage systems on the site will be discussed in greater detail in SECTION 6 “STORM WATER DRAINAGE” below.

[CU4]

3. Levels of MTBE at Northern Supply Wells

Comparing the P244 well to an ExxonMobil monitoring well in terms of MTBE level is comparing apples to oranges. Note for example, MW 10 with an MTBE level of 7.5 (250 bgs, 337 amsl, 43) versus P244 with a MTBE level of 8.7 (504 bgs, 71 amsl, 44). The well at P244 is 254 feet deeper than MW 10. The reservoir (assuming a standard 6” pipe) holds 381 more gallons of water than MW 10. An adjusted level of MTBE for the P244 well accounting for the dilutional effect of the reservoir is 15.2 ppb MTBE as a baseline comparison. The Packer Test (SARMar2005, Figure 9) shows the expected result for MW 10 with the shallow zone demonstrating a level equal to the pretest equilibrated value. For P244, all zones shows significantly less MTBE than the pre-equilibration value. This can only be explained by the fact the Packer itself obstructed a feeding fracture zone.

4. Water and Contaminant Flow Northward

Another major concern is that there is significant horizontal flow of groundwater in the overburden in addition to vertical flow through the overburden and into the bedrock. The point at which horizontal flow descends into the bedrock in all four quadrants is not known, but this is especially true to the north. A major flaw in the study design is that there were no overburden wells bored northward.

The fact that groundwater flow in the overburden does not solely follow a preferential path southeastward will be discussed under the SECTION 7, “GROUNDWATER”, but it is worth reemphasizing that the ExxonMobil site sits at a topographic high for the study region. It is on top of the “mountain” on Mountain Road. There are almost equidistant downward sloping gradients topographically extending northward, southward, eastward and westward. In fact, the steepest and closest gradient is directed to the northwest. The flow of water in all of these directions is highly probable and even more so considering the draw by the private supply wells during the drought of the 1990’s. The effect of drought and groundwater flow in the Central District has been recorded and documented from 1987 to present by the State of Maryland. Indeed, if most of the groundwater is flowing parallel to the land surface as claimed by ExxonMobil, then it follows that at least some water is flowing to the north, east and west of the ExxonMobil site. Without question, shallow groundwater has flowed in those directions during the extreme aquifer draw during the drought of the 1990s. Again, it is a major flaw in the study design, based on topography alone, that extensive monitoring of the overburden and bedrock was not conducted in the area northwest of the site.

ExxonMobil’s selective use of surface electrical resistivity profiling (SAR Mar2005, Subsection 6.1) reflects the predeterminative approach of the entire investigation. Exxon refuses to consider that any water could have flowed northwest of the site. Thus, it did not perform a surface electrical resistivity profile for the area northwest of the site, and has not installed any monitoring wells in that area, not even to confirm its staunch presupposition. As long as Exxon refuses to collect any data from this quadrant, it cannot state conclusively that no water flows to the north of the site.

Through its consultant, Roux Associates, ExxonMobil argued at the 5/02/05 community meeting that there is no northward contaminant migration because the contaminant levels north of the site are lower than the contaminant levels found along the same strike line to the south of the site. The consultant pointed out that P244 (Wawa supply well) only showed a level of 8.7 ppb MTBE. However, this incorrectly assumes that the wells to the south are identical to the wells in the north – that is they draw water from the exact same zones – and that the aquifer is homogenous in all directions.

As will be discussed below, there are three significant locations in line with the strike northeastward that have MTBE elevations. The property at 2716 Farmview (15-20 degrees NE, 0 .17 mile) showed a maximum MTBE level of 11.6 ppb in the summer of 2004 and 7.5 ppb in January 2005. The property at 2719 Fallston (shopping center) (20 degrees NE, 0.1 mile) showed a maximum MTBE level of 7.6 ppb in January 2005. The property at 2801 Fallston Road (P244, 9 degrees NE, .07 mile) showed a maximum MTBE level of 8.7 ppb MTBE in January 2005. Thus, it is indisputable that there was contaminant migration northward.

Second, these wells are private supply wells, and their casings (2716 Farmview-63 feet bgs, 2719 Fallston- 54 feet bgs, 2801 Fallston- 40 feet bgs) extend into bedrock. Consequently, these wells do not directly receive any groundwater from the overburden.

Third the depths of these wells are not comparable to the depths of the ExxonMobil monitoring wells (2716 Farmview 350 feet bgs, 2719 Fallston 400 feet bgs and 2801 Fallston 505 feet bgs). Hence the measured levels in these wells represent a diluted concentration of MTBE compared to the ExxonMobil monitoring wells as was so readily observed in the P244 site (Wawa supply well).

Fourth, there is a significant lineament extending northwestward right up to 2716 Farmview and ending near the entrance to Cross Country Estates. Lineaments again are only indicators of the underlying geologic morphology. The magnitude of this NW-SE lineament is equally impressive as the NE-SW lineament. It is highly probable that there is a juncture between the NE-SW and NW-SE lineaments in the bedrock driving contaminated water in the direction of Cross Country Estates and Franklin’s Chance.

5. Summary

Geophysical, lineaments and bedrock outcropping features have clearly demonstrated the presence of a major NE-SW strike, a major Northwest dip as well as a minor but significant NW-SE strike. Despite these data, ExxonMobil has not undertaken any investigation to determine the geomorphology of the area northwest of the site.

To support their only hypothesis, ExxonMobil only placed two bedrock wells to the north of the site. One of these wells was placed at outer boundary of their described strike axis of N30^oE and N50^oE. Hence 50% (1 of the only 2) wells were placed in a location with a low probability of intersecting the main axis of contaminant flow.

A major rationale for not exploring the northwest sector is ExxonMobil’s contention that groundwater only flows southeastward. They base this conclusion on static water isocontour maps, topography, surface electrical resistivity, hydraulic conductivity and the transmissivity of the aquifer. These factors will be addressed in subsequent sections. Furthermore, they also contend that since the MTBE level at P244 is low in comparison to an equidistant point southwest, that contamination from the site has not migrated northward. However, both the P244 well and MW 25 are beyond the limits of ExxonMobil’s own defined axis of the strike. (Note, that even though the P244 supply well is not within the strike axis, it is still contaminated). The decline in MTBE levels over short distances is amply demonstrated on the monitoring wells on ExxonMobil’s own site. Hence, even though the level of MTBE at P244 is only 8.7, it is possible that a short distance away the level could be significantly higher. The lower level may reflect the fact that P244 is not in the direct path of contaminant flux. Four properties as far as 0.17 miles northward show evidence of significant MTBE contamination. Clearly, there is a geomorphologic pathway for contaminant flux northward. The rational behind ExxonMobil’s theory cannot be supported.

ExxonMobil sits on a topographic high with a relief of 100 feet within one-half mile of the Exxon site in all four quadrants. The steepest and closest downward slope is to the northwest.

A major lineament comparable to the NE-SW lineament extends southeast to northwest ending at the base of Cross Country Court near Baldwin Mill Road. Despite the presence of this major indicator of a significant underlying geologic structure change, ExxonMobil did not investigate this northern sector.

SECTION 6: STORM WATER DRAINAGE

1. General

On of the most disturbing elements regarding the layout of the ExxonMobil site is the location of the storm drain inlets, pathways and outlets in relationship to potential point sources of contamination.

The storm drain is deeply trenched as seen in the photograph of FIGURE 10. There are two main drainage culverts on the station. (FIGURE 11)

2. Northwestern Storm Drainage Culvert

The first system, labeled “A” runs in an open ditch along the front peripheral edge of the station. The open ditch eventually enters a culvert and discharges northwestward into a rip- rap channel just alongside the MD 152 easement. One storm water inlet, one storm drain inlet and a storm water infiltration device empty into the same conduit leading to the rip-rap channel.

3. Southeastern Storm Drainage Culvert

The second drainage system labeled “B” in FIGURE 11 is a drainage system of major concern. Water collecting to the rear of the property flows behind the station building directly over MW 22 and MW 9. Bedrock MW 22 is the “epicenter” well on site with an MTBE level of 3770 ppb. MW 9 is an overburden well with an MTBE level of 1150 ppb MTBE. The drainage courses behind the station building along the northeast edge of P278 (Morgan Property) before turning northwestward and emptying into the same rip-rap channel as drainage system “A”. What is most disconcerting is that drainage channel "B" is less than 10 feet from the septic system on the property. On site Sewage Disposal Records and HCHD records as noted previously have demonstrated that the soil exhibited a fast percolation rate (4 minutes and 5 minutes) (at 5 feet). Hence any superficial contamination would be quickly moved by water sieving through the drainage ditch. Contamination could migrate in two directions a) vertically into the soil of the drainage ditch by percolation or b) carried by the drainage waters to the rip-rap channel adjacent to MD 152. Because MTBE is extremely hydrophilic, water flowing over the highly contaminated area near MW 22 and MW 9 could draw the contamination with the flow, spreading the contamination along the course of the ditch an into the rip-rap channel. The fact that drainage ditch course along the northeast property line of P278 and the fact that the well on P278 is shallow at 75 feet suggests that contaminant migration via the drainage ditch could have been an alternative overburden route that contributed to the contamination of this well. ExxonMobil failed to adequately investigate and address this potential pathway of contaminant flow.

4. Storm Drain Egress Topography

Of greater concern is the fate of any contaminant that reached the rip-rap channel. Given the topography of the rip-rap site, the water has no alternative but to percolate into the overburden. The only question remaining is what direction the water will take once it penetrates into the overburden. A detailed topographic map of the elevation isocontours in the northwest region of the ExxonMobil site near the riprap channel illustrates a major route of potential contaminant spread to be northwestward. (FIGURE 12)