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1 Saltwater Transport to Lake Ballard Through a Remnant Valley at Hoffler Creek Wildlife Preserve Alicia Dobyns, Preston Lewis, Jennifer MacDonald, Heather Moore, Nathan Rycroft, Gretchen Teed, and Kellie Wright OEAS 441-442 Field Studies I and II Summer 2008 Instructors: Dr. David Burdige, Dr. Richard Whittecar, & Amy Pitts Department of Ocean, Earth, and Atmospheric Sciences Old Dominion University 2 Introduction Lake Ballard, located in Portsmouth, Virginia, was originally created as a borrow pit by the Virginia Department of Transportation in the late 1970’s and 1980’s in order to provide construction materials for the local highway system (Figure 1). The lake and its surrounding forested areas are now part of the Hoffler Creek Wildlife Preserve and are currently used for a multitude of purposes including recreation, education, and research. Hoffler Creek, a brackish tidal estuary, marks the border to the west and south of the preserve while a residential community along the James River borders its northern side. Another development of single family homes frames the eastern edge of the preserve. The borrow pit was excavated in two major sections; one was approximately 8 meters deep on the western side of the current lake while the other was approximately 16 meters deep and located on the eastern side. During the excavation, it was necessary to steadily dewater the pit as groundwater flooded in from the shallow Tabb and deeper Yorktown aquifers. The Tabb aquifer is made up of mostly sand deposited during the late Pleistocene period. The Yorktown aquifer, which lies below the Tabb, is composed of gravelly clayey sand and large amounts of shell fragments (Whittecar et al., 2005). The pumping of water caused saltwater intrusion into the aquifers which contaminated local wells. After excavation, the pit filled with brackish water to approximately the point where it is currently, close to 13 meters at its deepest point. It was expected that after a period of time, groundwater recharge and precipitation would reduce the salinity of the lake and eventually return it to a fresh water state. The salinity of the lake has remained relatively constant since it filled nearly twenty years ago (Wolny, 1999; Allen, 2004). 3 Previous Studies Numerous research projects in and around Hoffler Creek Wildlife Preserve have analyzed chemical and geologic aspects. Allen (2004) mapped the spatial distribution of multiple physical and chemical properties of Lake Ballard. He found the existence of a thermocline and a halocline which were approximately mirror images of each other, both existing at approximately 6 meters. Allen also found that the pH of Lake Ballard was approximately 9 at the surface and then decreased linearly as the depth increased. Another finding was that there was a large anoxic zone at the bottom of the lake which he attributed to poor vertical circulation and seasonal algal blooms. Austin (2005) described her three-year study which ran from 1999 to 2001. She found that the thermocline existed mainly in the spring and summer months while there was no change in the vertical temperature gradient during the winter. Her data also showed that chloride and alkalinity concentrations remained relatively constant from the surface until approximately 7 meters of depth and then increased dramatically. Austin concluded from her data that there is little to no mixing in the deep sections of the lake but the top 7 meters are well mixed. Whittecar et al. (2005) ran a resistivity survey in the surrounding areas of Lake Ballard in order to find the areas where saltwater existed underground and the effects that saline water had on the lake. The study found that a majority of the Tabb aquifer is filled with freshwater except for areas near the James River, the western end of the lake stretching into Hoffler Creek, and a channel which exists on the South end of the lake in a remnant creek valley (Figure 2). Although the data from the Yorktown aquifer was limited, it was presumed that the entire area of the aquifer underneath the study area contained brackish water. The conclusion of the study was that the major source of salinity in Lake Ballard is the Yorktown aquifer which comes into direct 4 contact with the deepest areas of the lake. It was also concluded that the broad area of saline water which exists on the west side of the lake is seeping from the lake into the Tabb and eventually into Hoffler Creek. Boehmer et al. (2005) and Ranck et al. (2006), both summer field study classes, confirmed the theory that the broad area of saline water on the west side of the lake is groundwater which flows from the lake toward Hoffler Creek. They accomplished this by constructing wells and analyzing head data. Ranck et al. (2006) took the study further and found that the groundwater flow through the Tabb aquifer around the lake is from east to west. By collecting water samples and recording data from the YSI meter, the study also found highly reduced water in the deepest parts of the lake, confirming the observations made by Allen (2004). The 2006 study found that the reduction of sulfate is a major source of alkalinity in the lake but cannot be the sole source of the high alkalinity levels at the greatest depths. Alexander et al. (2007), another summer field study group, concentrated on the sources of alkalinity in Lake Ballard. Their results showed that sulfate reduction and calcium carbonate dissolution are the major sources of the alkalinity in the lake. The study concluded that the lake does not overturn due to temperature-induced density variations between the upper and lower waters of Lake Ballard. The study left open the possibility of mixing caused by physical processes. In addition, the study showed that the lake is not a closed system and concluded that a source could be introducing ions from either the north or the south side of the lake. Research Goal The primary goal of the Summer 2008 Field Study students is to determine the significance of a remnant valley on the south side of Lake Ballard as a source of saltwater to the lake. A secondary purpose is to continue the chemical analyses of the lake and the adjacent aquifers. 5 Approach Previous studies centered on Hoffler Creek Wildlife Preserve indicated that there is a continuing source of saline water into Lake Ballard. Using the evidence from the Whittecar, Nowroozi, and Hall (2005) resistivity study and the suggestion of the Summer 2007 Field Study class that a source of ions may be intruding from the north or south, we chose to concentrate on an area of low elevation between Hoffler Creek and Lake Ballard on the southern side of the preserve. The remnant valley, as it is referred to here, was analyzed using various geochemical and geophysical methods. Methods Surveying Surveying was used in order to find the elevations of both existing and newly established wells as well as the water table. By using the lake as a daily local datum, it was possible to find relative elevations at selected locations around the lake. Measurements were taken with a self- adjusting level and a stadia rod. Because water level readings were taken from the top of the casing of each well, the rod was placed on top of the casing of each well where the reading was then taken. The elevation of the lake was later verified by measuring the creek at a known high tide and adjusting all elevations relative to sea level. Vibracore We collected five vibracores along the length of the remnant valley located on the south side of the Hoffler Creek Wildlife Preserve between Lake Ballard and Hoffler Creek. In order to start the coring in saturated sediments, we used a post-hole digger to excavate a hole down to the water table. We used a gasoline engine to power the vibrating head attached to six-meter-long 6 aluminum core tubes. While it was vibrating, we drove the tube into the saturated soil by pulling down on ropes connected to the head. Using a jack and attaching it to the head, we hoisted the core tube out of the ground and sliced it into manageable lengths. In the lab we sliced open the tubes, described and sampled them, and used a scanner to obtain an image of the archived half. Pore Water Sampling After the soil samples were collected from the vibracore columns, a portion was placed into labeled centrifuge tubes. The samples were positioned in the centrifuge according to weight so opposing sides were balanced. The centrifuge was turned on for thirty minutes so the water would settle on top. The water was then poured into a filter leading to a smaller test tube to store it, with a couple of drops being placed on a refractometer to determine the salinity. Sulfate and chloride concentrations were determined in the pore water samples using an ion chromatograph. Sediment analysis Sediments that were collected were analyzed visually and by particle analysis. After being split, each vibracore tube half was visually analyzed for compilation of a stratigraphic cross section of the valley. Soil samples were taken to the lab for particle size analysis. The purpose of particle size analysis is to determine D 10 to use for the Hazen permeability approximation. In order to determine this value, we ran pipette and sieve analyses. We placed the samples on separate sheets of paper and used the quartering technique to split the sample, then transferred it into a pre-weighed beaker. We weighed the sample and beaker then subtracted the weight of both from the initial weight of the beaker. While we did this, we noted the type and size of any coarse organic particles present. Using 10mL of sodium hexametaphosphate, we deflocculated each sample individually to disperse the clay particles. To ensure that all samples 7 were thoroughly washed, we filled the beaker with enough deionized water to cover the sample in its entirety. The samples were allowed to sit overnight. To separate sand from finer sediment we wet-sieved it using a 4-phi sieve. The water was captured in a 500mL beaker. Once the water flowing into the beaker was clear, the remaining sample in the sieve was placed in a new, clean, pre-weighed beaker and set in the oven to bake. The liquid portions were placed in 1000mL-graduated cylinders and filled up to 1000mL. For the pipette test, two samples were drawn from each graduated cylinder at intervals of 20 seconds and 2 hours. The sample for 20 seconds was taken 20cm down from the top of the water level; the 2-hour reading was taken at 10 cm down from the top of the water level. The samples were then placed in clean, pre-weighed beakers and allowed to bake at 65°C overnight. They were then removed from the oven and immediately weighed. We dry sieved the coarse portion of the oven-dried samples. Using sieves of -1, 0, 1, 2, 3, and 4 phi, we placed the sample individually in the top of the sieve stack and placed on the sieve machine for 15-minute intervals. Each pan was emptied into a pre-weighed and labeled boat and then re-weighed. The weight of the sample was then found by subtracting the tray from the tray/sample weight. Well Construction and Development To expand our knowledge of the possible groundwater interaction between Hoffler Creek and the southern side of Lake Ballard, we decided to construct nine wells in a remnant creek bed. The number and depth of wells was chosen as the result of visual examination of extracted vibracores and refractometer readings from the pore water samples collected in the cores. At the location of vibracore 1 (VC1), closest to Hoffler Creek in the range of Spartina alterniflora, we found three layers containing mixtures of sand or combinations of sand and mud. Wells were 8 hand augered to depths of 70 centimeters and 125 centimeters. For a third well, we utilized the core sample hole by removing fallen sediments from the bottom to a depth of 3.6 meters. The wells became named 11a, 11b, and 11c respectively. The second set of wells were placed 14 meters inland toward the lake amongst Spartina patens at the location of VC2. A team of four students with Dr. Whittecar hand augered two wells, numbers 12a and 12b, to depths of 110 centimeters and 3.75 meters, again using the core sample hole drilled ten days earlier for the deeper well. Four days later, a second team of students assisted in hand augering one well at the site of VC3, later named well 13a, in a wooded area between the creek and lake. The well, located 21 meters north of well 12, penetrates to a depth of 2.03 meters. Two new holes were excavated on the southern side of the road surrounding the lake to show where peaty valley sediments of the Kennon Formation had been truncated by excavation and the underlying sandy Tabb Formation appeared near Lake Ballard. We augered well 14a to a depth of 2.05 meters and well 14b to 3.51 meters. The last well was placed in the location of VC4 on the edge of the lake within the reeds. Well 15, as it was named, is 2.21 meters deep and was set into Tabb Formation sands. Each well is constructed of a 1¼ -inch diameter PVC pipe riser with varying lengths of PVC well screen and a cap at the base. We glued extensions together with clear PVC cement after preparing the surface with purple primer. Once the riser was in place, we filled the hole with sand to cover the screen, and then added a layer of bentonite to preserve the integrity of water entering the well. Castings and additional sand filled the remainder of the hole, and then it was topped by more bentonite at the surface. Details of each construction are located in Appendix A. Each well was developed using a plunger to improve the flow of groundwater 9 through the well screen and remove settled matter from the base. A hand-held PVC bailer was also used to remove all standing water as a way to develop the wells and to test recovery rate. Water Sampling By collecting many water samples from Lake Ballard, Hoffler Creek, and the wells constructed from this summer as well as prior years, chemical content was analyzed to better explain groundwater flow. By using a Water Level Indicator, YSI Model 85, bailer, and Masterflex E/S Portable Sampler, data about water level heads and concentrations of chloride, sulfate, and saltwater can be observed. Oxygen content, conductivity and temperature is also observed by the YSI. The following sections detail the YSI, Water Level Indicator, Masterflex E/S Portable Sampler, and bailer. YSI Model 85: Oxygen, Conductivity, Salinity, and Temperature The YSI is a handheld device that is used to determine oxygen, conductivity, salinity, and temperature of a water sample at certain depths. The handheld device is attached to a wire with three electrode sensors on the other end that are lowered into the water at a desired depth. After the numbers stabilize on the YSI handheld screen, they can be recorded. The oxygen is recorded in milligrams per liter, the salinity in parts per thousand, and the temperature in degrees Celsius. This is used on all wells, Lake Ballard, and Hoffler Creek. Water Level Indicator The Water Level Indicator is used to measure the level of the heads in the wells by indicating the top of the water standing in them. Once the indicator is turned on, the wire with the sensor on the end is lowered down into the well until a slight buzzing noise is heard. The reader’s fingers are then placed on the wire at the top of casing measuring the depth to water. 10 The number on the wire where the reader’s fingers are placed is recorded, signifying the depth to water. Masterflex E/S Portable Sampler and Bailer The portable sampler and bailer are used to take water samples out of Lake Ballard, Hoffler Creek, and wells around the lake. The liquid is placed in clean bottles, and taken back to the lab for testing of chloride and sulfate content. The bailer, used for the wells containing too little water to sample with the Masterflex E/S Portable, is lowered until it is filled with water. A ball within the bailer traps water in once the bailer is pulled up, then the water is poured into a bottle from the other end of the bailer. Each bottle is labeled with a date of when it is taken and what well number the sample came from. This process is done for all wells including preexisting wells 1-8 and the nine wells constructed this summer (11a-c, 12a-b, 13, 14a-b, and 15). For the samples in Lake Ballard and Hoffler Creek, the portable sampler is used by clamping the soft part of a tube to the machine and lowering the other end to the desired depth. A filter is attached to the soft end of the tubing to ensure an accurate sample. The pump switch is then turned on and the water sample flows through for a moment to clear the tube of any other water sample. A bottle is then placed at the tip of the filter and filled with the sample. Each bottle is labeled at what depth, station, and date the sample is taken. A weight must be placed on the end of the tube in order to ensure it reaches the desired depth without curling. All lake samples were taken on June 2nd, 2008 at stations 1-6 (Figure 3). At station one, samples were taken at depths of 1 to 8 meters and at station two they were taken at depths of 1 to 13 meters. Station three’s samples were collected at every meter between 1 through 6. An additional collection was made at 6.5 meters for clarification of the thermocline. Then samples were taken every meter between 7 and 11 meters. Closer to the halocline, sampling was taken at 11 every half meter at 11.5, 12, and 12.5 meters. Station four was relatively shallow, so samples were taken at 1 to 4 meters. Station five samples were taken at depths of 1 to 6 meters and station six samples came from 1 to 6, 6.5, and 7 through 12 meters. Two small boats were used to arrive at these stations within the lake and an anchor was dropped to keep the boats stationary. The station’s GPS readings were recorded along with the rest of the YSI data. Ion Chromatograph (IC) Ion Chromatography is used to measure concentrations of major ions in an aqueous solution. Michael Tswett originally developed the principles and application of ion chromatography in 1903, and techniques incorporating elluent suppression were perfected in the 1970’s (Dionex Corporation, 2002). Within the study area, water samples were collected from Lake Ballard, Hoffler Creek, and from each well. An ion chromatograph (IC) consisting of Rainin and Dionex components was used in order to obtain a chemical profile of each water sample from the study area. Each pore water, lake, creek, and well sample was analyzed for chloride (Cl-) and sulfate (SO 4 2-) ions. At the beginning of each run, standards of chloride with concentrations ranging from 0 µM to 1,000 µM and sulfate with concentrations ranging from 0 µM to 2,000 µM were used to calibrate the IC and create a daily calibration curve. On average, five standards were run prior to the analysis of samples. The retention time was used to determine the peak associated with a specific ion, and the area count of the peak used to determine the concentrations of each sample. Each sample from the study area was filtered using Whatman 0.45 µm prior to injection. Approximately 0.5 mL of each sample was injected into the sample loop, where it was combined with elluent and the ions were allowed to separate from the sample for detection. The conductivity detector was set at 1000 µS. Some of the samples had to be diluted using deionized 12 (DI) water in order to obtain a reading for chloride. Mac Integrator II software was set up to acquire and analyze data from the chromatographs. The computer then displayed the area of each peak and the data collected from Lake Ballard, Hoffler Creek, and from each well and vibracore site. Data was then entered into a spreadsheet to calculate the concentration levels in each sample. The following equation used the displayed area to calculate the concentration of anions in each of the non-diluted samples. Anion Concentration = (Area Under the Curve – Y-Intercept) Slope The concentration levels in the diluted samples were determined using the following equation. Adjusted Concentration = (Ion Concentration x Total Volume) (Sample Volume x 1000) **Where: total volume = sample volume + DI water Titration The main purpose of completing a titration is to determine alkalinity. Alkalinity can be defined as the ability of water to resist a change in pH. When a sample of water is said to have a high alkalinity, it has a greater ability to resist a change in pH. When a sample has a low alkalinity, small changes in pH make a difference in the solution and only small amounts of buffering occur. In the lab, an automated titrator is used to take out human error and give more accurate results. After water samples were taken in the field, the Titrino automated titrator was used to measure the alkalinity. The machine does this by the addition of small amounts of hydrochloric acid (HCl) to the water until the sample can no longer resist the change in pH. The equation that the computer uses to give a value to alkalinity is: alkalinity = . 13 While the samples are tested in an automated machine, it is possible to get similar results with a manual titration and use this same equation to obtain alkalinity numbers. The Titrino pH electrode was calibrated using buffers with a pH of 4, 7, and 10. In order to verify that the calibration of the machine was accurate, a slope close to a standard should be generated. After we calibrated the machine we obtained a slope that was reasonably close, which meant that we could begin titrating lake samples. To begin the titration, two grams of the sample were placed into a 4 mL vial with a small stir bar. The small amount is used so that a volume of HCl could be added and not overflow. After the correct program was downloaded to the machine, the weight of the sample could be entered in to the machine so that the alkalinity could be calculated. If these pieces of information are entered wrong it is possible that the end point of the titration could be over-shot and require a second run. During the process, the downloaded program placed a predetermined volume of HCl into the vial, and then small additional doses were metered periodically. During the titration the pH is constantly measured. When the pH is unable to resist the change, the titration is complete. Ground-Penetrating Radar (GPR) Ground-Penetrating Radar was used in attempt to estimate the thickness and width of fluvial sediment deposited in the remnant valley and to determine the possible presence of saltwater. This radar, a PulseEKKO 100, sends repetitive pulses of electromagnetic waves in frequencies of 100 MHz into the ground. Once the waves have reached the reflectors or changes in strata, they reflect a pulse back to the surface. While the leading paddle, the transmitter, sends the signal into the ground, the second paddle, the receiver, collects the waves bounced back to the surface. Data is transferred to an attached computer until it can be processed. Along each 14 GPR transect, the spacing of the antennae, or the transmitter and receiver, was 1.0 m and the step distance was 0.5 m. After the relative elevations of points around the lake and across the remnant valley were surveyed with a level and rod, GPR transects were run along the road on the south side of Lake Ballard across the top of the remnant valley (LB266 TP), down the middle of the remnant valley, across the valley near the creek (LBI2), and a control on the north end of the parking lot (LBLOT). A common mid-point test (LBCMP) for velocity was shot on the east side of the lake where the transmitter and receiver were moved 1.0 m apart each run, the final spacing distance equaling 10 m (Figure 4). During the run along the road, the transmitter and receiver at each shot was placed 1.0 m apart along a 140 meter distance, with a break in the run made at the 60 meter mark. For the run across the creek, the transmitter and receiver set at 1.0 m apart shot a total distance of 65 meters. The run along the North end of the parking lot was run the same way along a total distance of 40 m. The run down the middle of the remnant valley was aborted due to rain and battery problems. In the lab, files were created for each transect and placed in the radar program. A graph was then created and the velocities for each were changed to fit a better slope and account for depth of radar penetration. The elevations from the survey were also entered into the chart. Data were processed with PulseEKKO software, including modifications for topography. Results Mechanical Sediment Analysis Four vibracores were taken from the area through the remnant valley (Figure 5). The vibracores were then sealed and taken back to the lab for further analysis. Upon visual analysis, the core closest to the creek (VC 1) was observed to be reduced mud with fibrous organics mixed 15 throughout. Vibracores two (VC 2) and three (VC 3) both showed visible signs of mud with mixed organics. Some sand was present in the upper layers of each core. The fourth vibracore (VC 4) was extracted closest to Lake Ballard and contained mainly construction fill with Tabb sands at the bottom. Pictures were taken of each core and pieced together in order to assemble a complete cross-section (Figure 6). Using the cross-section constructed from the visual interpretations of the cores, a geologic interpretation was constructed (Figure 7). The peat- and mud-rich sediments throughout the remnant valley is the Kennon Formation, deposited during the present sea-level rise approximately 10,000 years to present. This formation consists of mainly tidal marsh fill. Close to Lake Ballard, we drew a thick, black vertical line where we estimate the location of the wall of the remnant valley. On the north side of the thick, black vertical line are Tabb Formation sediments. This sediment was deposited 120,000 years to 70,000 years ago during the last interglacial time period. It contains clean sands with pebbles. The thick horizontal black line over the Kennon and Tabb sediments is a geologic unconformity separating anthropogenic fill from the Kennon and Tabb. The anthropogenic fill consists of agricultural runoff from farmlands and mining waste from the removal of Tabb sands. From half of each vibracore, samples were extracted and used for particle size analysis. For vibracore one, two samples were taken at 80-90 cm and at 270-280 cm. The first sample has a very low percentage of very coarse sand with the most abundant grain size being medium-fine sand. In the second sample, medium-fine grained sand is also the most abundant grain size with very coarse sand being the least abundant. From VC 2, two samples were taken at 90-100 cm and 200-210 cm respectively. For 90- 100 cm, the most abundant grain size is silt followed by clay with the least abundant being very 16 coarse sand. The second sample was well sorted. The majority of grain sizes were between medium-fine sand to silt. The third vibracore was extracted from the middle of the forest and also at the highest elevation. The samples were taken from 50-60 cm and 130-140 cm. In the shallow sample, the majority of sediment was silt. Very fine sand was not as abundant as the rest of the sediment. The deeper sample showed the majority of grains being medium-fine sand and contained little clay. For Well 14, we hand dug down to 3.5 meters. Two samples were taken from the sand and mud. The sand showed a majority of medium-fine sand grain and very coarse sand to be less abundant. The mud section of the hole showed a very high percentage of silt with very little sand. VC 4 came from the shore of Lake Ballard. The sample from 0-10 cm showed the majority being medium-fine sand. The sample from 120-130 cm revealed that medium-fine sand was the majority, followed by very-fine sand, and medium sand. The least abundant grain size at this level was silt. Details of each particle size analysis are found in Appendix B. Head Data/Rainfall Head data was collected from the nine new wells in the remnant valley and from the existing wells around Lake Ballard. Four data sets were taken from wells 11 through 15, beginning approximately one week after construction (Figure 8). On June 23, 2008, the depth to water was the greatest in each of the wells. Two weeks later, on July 7, wells 11 and 12 exhibited a shallower water table. Wells 13, 14, and 15 all remained approximately the same. Three days 17 afterwards, water rose near the surface at well 12. The wells closer to Lake Ballard remained at similar levels as on the previous sample dates. On the last day of testing, July 14, levels in the wells near Hoffler Creek had resided toward the original head levels. Measurements of depth to water were collected on the west side of Lake Ballard on three of the same dates as the remnant valley. The east side was tested twice. Separating the data from the shallow wells that penetrate the Tabb Formation, results showed a general decrease in head from east to west (Figure 9). The two deep wells that sample the Yorktown aquifer, one on the west side of the lake, and one on the east gave elevations lower than the lake (Figure 10). Rainfall data for the period of the study was collected from www.weather.com. Very little precipitation occurred during the first two weeks in the field. On June 17, accumulation of over two centimeters fell. Rain became more common as June ended and July began. Between the first and second head sampling dates, on July 4, over three centimeters were recorded by the weather service. Details of each accumulation were graphed along with our key field dates (Figure 11). Tide Data Based on a conversation with a Hoffler Creek Wildlife Preserve Foundation member, we know that at only one time, during hurricane Isabel in September 2003, has saltwater from the creek flooded over the berm reaching 2.4 meters above sea level, and spilling into Lake Ballard. This information led us to research how tides influence the presence of saltwater in the lake on a more frequent basis. Hoffler Creek is a tidal creek that branches off of the James River. The creek is greatly affected by the rise and fall of the Chesapeake Bay’s semidiurnal tidal fluctuations. Using the National Oceanic and Atmospheric Administration (NOAA) website, we were able to browse 18 through an immense resource of historic tide data from various locations throughout the Chesapeake Bay watershed. The nearest location to Hoffler Creek that records regular tidal data was located at Sewell’s Point which is in Norfolk, VA. Maps found on Google Earth indicate Hoffler Creek is approximately 5 miles from Sewell’s Point (Figure 12). To use the vast database we had to first ensure that the Sewell’s Point data would correspond to the tidal fluctuations occurring at our location at Hoffler Creek. We took tidal data from October 5-6, 2007 at Hoffler Creek and compared it to the tidal data from Sewell’s Point on those same days (Figure 13). With these results we were able to calculate a lag time of 3 hours and 42 minutes. We then normalized the tide readings from Sewell’s Point and Hoffler Creek (Figure 14). The results prove that the tidal record taken from Sewell’s Point correlates with and can be used to predict the tide levels occurring at Hoffler Creek. This correlation now opens up for us and future researchers an extensive tidal database. Using the NOAA database and its high tide record, and comparing this with the elevations of the remnant valley which are known through surveying, we can estimate how far the saltwater from the creek rises in the remnant valley that connects the lake and the creek. During the time we took water samples, there was a significantly higher storm tide of 1.1 meters on the 17th of June (Figure 15), which correlates with our rainfall record. This storm tide rose past the surface at well 12. Pore Water & Well Profiles In order to help validate the remnant creek valley as a source of ions into Lake Ballard, it was necessary to examine the soils and groundwater in that area. Using the vibracore, four samples were taken of the soil at locations VC1, VC2, VC3, and VC4. These locations correspond with the locations of wells 11, 12, 13, and 15. Well 14 was constructed at a point 19 where no core sample was taken, therefore, there are no pore water samples from that site. Pore water samples were taken from multiple sections in each core. A refractometer was used to find salinity readings immediately after centrifuging each pore water sample (Figure 16). The result showed a decrease in salinity with depth and across the remnant valley from Hoffler Creek towards Lake Ballard. The ion chromatograph was used in order to find the concentrations of both chloride and sulfate. Because we were most concerned with the areas which lie just above the confining mud bed, we mainly took into account the samples which originate from that area. Also, several of the wells which we constructed (11b, 12a, and 13) were placed specifically in the area above the mud layer so that we could observe the groundwater which flows at that level. The pore water sample from VC1 taken at a depth of 85 cm was found to have a chloride concentration of 141.04 mM and a sulfate concentration of 385.09 mM. The sample from VC2 taken at a depth of 95 cm had a chloride concentration of 73.32 mM and a sulfate concentration of 0.26 mM. The sample from VC3 taken at a depth of 95 cm had a chloride concentration of 37.89 mM and a sulfate concentration of 0.12 mM (Figure 17). The well water samples in these areas were found to have very similar concentrations. On July 14th, wells 12 and 14 were found to have much higher chloride concentrations. Lake Profiles Water samples from Lake Ballard were analyzed in order to determine the depth, temperature, salinity, dissolved oxygen, sulfate, chloride, and alkalinity measurements. The YSI meter was used to determine the levels of temperature, salinity, and dissolved oxygen. The data was then plotted into depth profiles of temperature and salinity values. The temperature decreased consistently with depth, although at approximately 12 meters the temperature of the 20 lake water began to increase slightly (Figure 18). The salinity remained fairly stable until around 10.5 meters where it began to drastically increase (Figure 19). Dissolved oxygen data showed that the anoxic zone of the lake has become more shallow over the past year, beginning at 6.5 meters in depth (Figure 20). The ion chromatograph determined concentrations of the sulfate and chloride levels in the samples taken from the lake. These concentrations, when plotted in a depth profile, showed that sulfate decreases slightly with depth and that chloride increases slightly until 10 meters. At that point, sulfate ions drop significantly while chloride increases (Figure 21). The alkalinity data measured by the Titrino Titrator was recorded against the depth of the lake. The data showed that there was a dramatic increase in alkalinity values at 10.5 meters. Well Recovery Rate After developing the nine new wells on July 7, they were emptied with a bailer to test the recovery rate. Both shallow wells close to Hoffler Creek could not be emptied because the water returned before it could be withdrawn completely. The deep well at the same location, number 11c, did not recover during the testing period. Well 12a did not refill completely after thirty eight minutes. A malfunction of the plunger line lost the developing tool in well 12b, making it impossible to test for recovery rate. Wells 13, 14a, and 14b all refilled completely between tests. The well closest to Lake Ballard, well 15, did not return to its initial water level within one hour. Details of the test are listed in Appendix C. Ground Penetrating Radar (GPR) The Ground Penetrating Radar was used to determine the presence of a valley shape and saline water within our area of interest, the remnant valley. In order to find this, 4 tests were run: velocity test between the pavilion and Lake Ballard, background check in the parking lot, and 2 21 runs across the remnant valley (Figure 4). For the velocity run, a common midpoint analysis had to be run in order to find a velocity of the pulse through these materials. Over a 10 meter run, it took 35 nanoseconds for the radar to bounce back to the surface or receiver giving us a velocity of 10 m per 35 ns or 0.14 m/ns (Figure 23). The background check in the parking lot was done to determine how far the GPR penetrates in a non-saline environment. Figure 24 shows the penetration to be about 10 meters down, but strangely attenuates the rest of the run. The run done nearest to the creek (Figure 25), shows the radar penetrating about 2 meters down along the sides or tops of the valley, whereas the middle of the valley shows about just barely a meter. Figure 26, the run along the road, shows a penetration of 2 to 3 meters on the sides of the valley and about 1 meter in the middle of the valley. ***ANALYSIS NOT EDITED*** Analysis Sediment Analysis After the particle size analysis had been conducted, D10 could be found for the Hazzen Approximation. We used the Hazzen Approximation in order to estimate permeability and ease of groundwater flow. D10 was collected for samples containing less than 10% mud and then displayed graphically on the Hydraulic Conductivity graphic (Figure ). It was found that the easiest conduit for groundwater to move from Hoffler Creek to Lake Ballard would be above the mud layer and, by density flow, sink through the Tabb sediments and into the depths of Lake Ballard. Hydro-geologic Sediment Analysis (Preston) When trying to understand how salt can travel from Hoffler Creek to Lake Ballard the subject of diffusion was brought up as a possible explanation. When looking at the sediment 22 cores diffusion is seems like a sound explanation the problem. However, after plugging in the values from Lake Ballard into the Einstein-Smoluchowski equation I have a much different idea of how long it takes for ions to diffuse though sediment. When solving the equation, distance was one of the variables that needed to be accounted for. To do this, measurements were taken from Google Earth at the high tide, low tide, and an average of the two in order to get representative distances to consider. After plugging in the variables that we needed for the equation, it was evident that it would take orders of magnitude longer than the lake has been there. Going back to the equation I rearranged the variables to solve for distance, given that the lake has been there for 20 years in order to see how far ions could have moved since the lake was created. The equation showed ions could have only moved a distance of 84 cm, not nearly enough to have an effect on the salinity of the lake. This same equation was used to show the time it would take ions to move from Hoffler creek to the Lake on the west to east direction. Once again, diffusion could be ruled out as a possible source of salt in the lake. Originally diffusion was an explanation for the salinity of the lake. However, the equations results tell us that it is safe to say diffusion is not possible in the time that the lake has been there. This will allow us to concentrate our efforts elsewhere to find the source of salinity. After all of the vibracore samples were separated and run through a series of particle size analysis, it was possible to use the Hazen approximation. This is an equation that uses an empirical equation to estimate the conductivity of particular sediment using effective grain size ). When using this approximation only samples that have 10 percent or less mud can be used to obtain reliable results. The results that are obtained from this method are given in cm/sec, which can later be converted into an actual velocity. Once the permeability (K) is obtained then that value can be plugged into the seepage velocity equation to get the approximate 23 velocity of the ground water. This equation is Vs= , where “K” is permeability, “ne” is porosity (obtained from a table of values), “dh” is the difference in head between two wells and “dx” is the change is distance between two wells. With results from this equation we will be able to determine of the sediment in the area has the ability to move water at a velocity that can move saline water from the creek to the lake. In order to get values from the seepage velocity equation that were reliable, the correct gradients had to be choose. To do so, the change in head was determined from a single day of sampling in which the head in well 12 was higher that that of well 15. The change in head (41cm) divided by the distance (50m) gave us a value that we could complete the equation with. After plugging in all of the values it was determined that ground water has the ability to flow through the system in the order of several days. Using other gradients obtained from the wells and the distances gave the same results, orders of days not weeks or months (salt flow rate figure). The seepage velocity equation works very well for our project. This is because all of the variables that are used in the equation are site specific. This allows us to use a range of particle sizes and varying gradients to see if it is even possible to get through flow from the creek to the lake. Well and Creek Discussion Section (Nate) The data retrieved by the YSI meter and water samples on each of the thirteen wells studied showed the temperature, salinity, chloride, sulfate, and dissolved oxygen of the groundwater at the specific depths of the screens in each well. The data shows that there is a clear pattern of salt water in both the Tabb Aquifer on the West side of the lake and in the remnant creek valley on the South end. The analyses of water samples from wells which penetrate to the top of the mud layer in the Kennon Formation (Wells 11b, 12a, 13, and 14a) show a pattern of steadily decreasing salinity from the well closest to Hoffler Creek (Well 11b; 24 8.8 ppt) to the well which is closest to the lake (Well 14; 3.3 ppt). Because the mud layer was excavated during the initial construction, Well 15 does not come into contact with the mud layer hence the reason that it is not included in the analysis. The wells which border the west side of the lake show a pattern of salinity which indicate the possible movement of ions across a gradient from the creek (25.0 ppt) through Well 8 (2.9 ppt) and Well 1 (2.4 ppt) and possibly into the lake (2.9 ppt). Of course, this data is not necessarily conclusive because well 8 and well 1 are at different depths with Well 8 located just above the Yorktown Formation and well 1 being fairly shallow into the Tabb. The difference in depths could affect the salinity because the more saline water will tend to fall to the bottom of the formation while less brackish water will remain higher in the column. Also, head data (discussed earlier) shows that advection actually opposes the concentration gradient thereby retarding the diffusion of ions into the lake. In the well samples, there were several odd chloride concentrations found in Wells 12 and 14 where the chloride levels were much higher than expected. These findings occurred after several days of heavy rains leading to the possibility that salt which was deposited in the soils was dissolved by the rain and then affected those wells. Conclusions Future Work • Salt Budget for Lake Ballard • Residence time of ions in Lake Ballard • Continued GPR studies around the lake 25 • To measure water table levels in the valley during a storm surge. Year round lake sampling 26 Figures Figure 1. Lake Ballard is located within Hoffler Creek Wildlife Preserve in Portsmouth, Virginia. The site lies within Virginia’s Coastal Plain. Figure 2. The shaded area to the west and northwest of Lake Ballard in addition to lobes at the north and south indicate areas of brackish water found during the Whittecar et al. (2005) resistivity study. 27 Figure 3. Locations of Lake Ballard samples taken on June 2, 2008 are pictured. GPR Paths Velocity Test Run: LB-CMP Parking Lot: LBLOT Southside Rd: LB 266 TP Bottom of Remnant Creek Valley: LBI12TOPO Figure 4. This shows the paths run for the GPR including a velocity run, background check in the parking lot, and two runs across the remnant valley. 28 Figure 5. Vibracore samples were extracted along the southern side of Lake Ballard. The locations became the sites of the wells constructed during the Summer 2008 Field Study. 29 VC 1 VC 2 VC 3 VC 4 0 M Vibraco Mud layer 1 M 2 M Figure 6. Vibracores scans show detail used in visual analysis. A layer of mud is indicated above between the blue lines. Scale for the length of each vibracore is indicated on the left. 30 Figure 7. This stratigraphic cross-section of the remnant valley is oriented with Hoffler Creek to the left, off the diagram, and Lake Ballard to the north at the right. Vertical lines represent the 5 primary holes used for sediment analysis. Horizontal Distance from Mean Tide (m) 10 20 30 40 50 60 2 14a 13 6/23 7/7 11a 12a 1 11b 7/10 FILL 7/14 Elevation (m) 15 0 Lake Ballard Lake Elev. Unconformity -1 (0.36 m) Qt -2 Kennon/Tabb Boundary Qk -3 Hydraulic Head Data S N Summer 2008 Figure 8. Depth to standing water in wells was recorded on four sampling dates. n/a 1.19 m 2.13 m 31 1.44m 0.26 m 1.18 m 0.85 m Dry Dry 2 7 8 1.51 m Results 0.98 m 0.76 m -0.13 m 5 0.37 m 6 1 0.30 m 0.76 m 3 0.24 m 0.36 m 0.0 m HCk Qt Qt Qk Groundwater Flow Elevation (m) Density Methods Ty E W 0 90 180 270 360 450 540 630 720 810 900 990 ’ 1080 1170 1260 Distance (m) Hydraulic Head 2008 Summer 2006 Hydraulic Head and Groundwater Flow Summer 2007 Tabb Aquifer Summer 2008 Summer 2008 Figure 9. Well heads around Lake Ballard along the East to West cross-section indicate groundwater flow in the shallow Tabb aquifer and a general drop in water level. n/a Hydraulic Head and Groundwater Flow 1.03 m 1.37 m Yorktown Aquifer 0.22 m 2 7 8 Results Summer 2008 5 6 0.82 m -0.13 m 1 HCk 3 0.0 m 0.98 m Qt Elevation (m) 0.76 m Qt 0.36 m Qk Density Methods Ty E W 0 90 180 270 360 450 540 630 720 810 900 990 ’ 1080 1170 1260 Distance (m) Summer 2006 Summer 2007 Summer 2008 Figure 10. Hydraulic head data from the Yorktown aquifer wells indicate a decrease in water level, similar to the Tabb wells. Data for groundwater flow is inconclusive. Portsmouth Rainfall 2008 Portsmouth Rainfall 2008 32 4.00 3.50 3.00 Amount(cm)cm 2.50 in s 2.00 Amount 1.50 v/s s s s w w 1.00 0.50 0.00 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 June Day July V – Vibracore W – Well Construction S – Sample Dates Figure 11. During the two months of field study, several rain events in Portsmouth occurred. Dates of interest are indicated by arrows. Vibracore sampling was taken on June 2, 2008. Well construction occurred on June 12 & 16. Water samples and/or head data was collected June 23 through July 14, 2008. Sewell’s Point Tide Observation Station James River Hoffler Creek Preserve Elizabeth River Figure 12. Map of James River and study area show proximity of NOAA Sewell’s Point Tide Observation Station to Hoffler Creek Wildlife Preserve. (photo courtesy of Google Earth) 33 Comparing Tidal Readings From Sew ells Point and Hoffler Creek On 10/5/2007-10/6/2007 1.4 Tidal 1.2 Readings at Sewells Point from NOAA 1 Tide Levels in Meters Tidal 0.8 Pressure Readings From Hoffler 0.6 Creek Average 0.4 (Sewell’s Pt) 0.2 Average 0 (Hoffler Creek) 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36 Time in Minutes Figure 13. The tidal pressure readings taken at Hoffler Creek between October 5 & 6, 2007 show a wave curve similar to readings from Sewell’s Point on the same days. 34 Comparing Tidal data from Sewell's Point and Hoffler Creek with adjusted lag time and adjusted height difference 1 0.9 0.8 Tide data from 0.7 NOAA Tide level in meters 0.6 0.5 0.4 0.3 Tide data from Hoffler Creek adjusted for a 3:42 0.2 lag time and a 0.399 tidal difference 0.1 0 10:12 11:54 13:36 15:18 17:00 18:42 20:24 22:06 23:48 10:00 11:42 13:24 15:06 16:48 18:30 20:12 21:54 23:36 0:00 1:42 3:24 5:06 6:48 8:30 1:30 3:12 4:54 6:36 8:18 Time in minutes Figure 14. When adjusted for time lag and normalized, the overlain tidal data curves from Sewell’s Point and Hoffler Creek are virtually identical. 35 High and Low tidal levels at Sewell’s Point in Norfolk, VA June 1st - July 31st 2008 Figure 15. Observed water level on June 17, 2008 was approximately 1.1m at Sewell’s Point, according to NOAA. This coincides with a large rainfall event in Portsmouth. Salinity for Pore Water Samples (ppt) Summer 2008 Horizontal Distance from Mean Tide (m) 10 20 30 40 50 60 2 Pore Water June 2, 2008 1 5 13 7 Elevation (m) 6 2 0 N/A 10 5 Lake 5 3.5 0 Unconformity N/A Ballard Lake Elev. -1 (.36 m) 2 0.5 N/A 2 Qt 1 -2 Kennon/Tabb 2 Boundary 0.5 Qk -3 S N Figure 16. Salinity measurements from pore water samples were taken using a refractometer. 36 Chloride Averages for Pore Water/ Wells (mM/L) Summer 2008 Horizontal Distance from Mean Tide (m) 10 20 30 40 50 60 2 Pore Water June 2, 2008 Hoffler Creek Well Water June 23, 2008 270.51 1 290.54 Elevation (m) 42.48 141.04 N/A 73.32 24.83 40.30 46.85 0 157.48 100.77 33.22 Lake 83.02 Ballard 113.22 Unconformity Lake Elev. -1 (.36 m) N/A Q 12.06 t -2 Kennon/Tabb Boundary Qk -3 S N Figure 17. Chloride data for the creek, lake, and wells Temperature vs Depth 0 5 10 15 20 25 30 35 40 0 -2 -4 Depth (m) 2006 -6 2007 -8 2008 -10 -12 -14 Temperature (C) Figure 18. Lake Ballard temperature vs. depth profile. The 2008 thermocline mirrors prior years when considering that each sample was taken under slightly different conditions. Of particular note is the small increase in temperature at the bottom of the lake. 37 Salinity vs Depth 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 0 -2 -4 Depth (m) 2006 -6 2007 -8 2008 -10 -12 -14 Salinity (ppt) Figure 19. Lake Ballard has a halocline at approximately 11 meters. Summer 2008 data is consistent with previous summer studies. Lake Ballard Data Dissolved Oxygen vs Depth 0 5 10 15 20 25 0 -2 -4 Depth (m) 2006 -6 2007 -8 2008 -10 -12 -14 Dissolved Oxygen (mg/L) Figure 20. The profile for dissolved oxygen in Lake Ballard shows a significant difference in depth at which the level drops to zero mg/L when compared to 2006 and 2007. 2008 measurements are similar to those taken by Allen (2004). 38 Figure 21. Ion chromatograph data for Lake Ballard. Sulfate decreases below 10 meters. Chloride ions increase at approximately the same depth. 39 Well Data 7/07/2008 Depth to Water Minutes (DTW) between Recovery Well # ft DTW DTW ft Comment unable to 11a 1.37 18 1.49 empty unable to 11b 1.45 23 1.51 empty 11c 3.08 16 11.33 slow 12a 2.49 38 4.78 slow 12b 4.66 13a 5.11 49 5.11 14a 6.31 66 6.28 14b 6.55 70 7.05 15 1.97 59 4.94 slow Figure 22. Well recovery rates. Shallow wells closest to Hoffler Creek could not be emptied by bailing. Deep well 11c, shallow well 12a, and well 15 all failed to recover to their initial water levels. Well 12b could not be tested due to a line failure that left the plunger in the well. GPR-Velocity Test Run-LBCMP 10m/35ns= 0.14 m/ns Velocity Test Run: LB-CMP Parking Lot: LBLOT Figure 23: This shows the velocity run where a common midpoint analysis was run to find the velocity through materials in this area. 40 GPR-Parking Lot-LBLOT Figure 24: This shows a background check done in the parking lot at Hoffler Creek Wildlife Preserve and was done to show how far the radar penetrates the ground in a non-saline environment, here being about 10m. Bottom of Remnant Creek Valley-LBI2TOPO Well 11c 0 2 8.8ppt 4 5.1ppt 6 Figure 25: This run was done across the remnant valley closest to Hoffler Creek. The shows salinity concentrations in Well 11c, with a mud layer 2 meters down. 41 GPR-Southside Road-LB175TO 0 Well 14a 3.3ppt 2.9ppt 5 Figure 26: This run was done along the south side road around Lake Ballard showing us the salinity concentrations in Well 14a and mud layer 2 meters in depth. Valley strata are also very well present here. 42 Hydraulic Conductivity of Core Samples Figure 27. Using D10 and the Hazen Approximation, the permeability of sediments along the remnant valley could be calculated. The most permeable areas are indicated by the largest octagons. The small squares show where samples were tested but contained more than 10% mud, so they fell outside of the test’s range of computation. Figure 27. Calculation of time for saltwater to travel through a variety of sediment sizes 43 Stratigraphic Controls: 10 20 30 40 50 60 2 Storm surge/Spring tide 1 FILL 0 FILL -1 Qt -2 Qk -3 Figure 28. In the event of a storm surge or spring tide, the saltwater of Hoffler Creek could cover ground above well 12 then travel through the sediments in the pattern indicated. Sulfate vs. Chloride with Seawater Mixing Line 15.00 13.00 11.00 Sulfate (mM) 9.00 SULFATE VS. CHLORIDE 7.00 LAKE BALLARD Linear (MIX LINE) 5.00 3.00 1.00 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 -1.00 Chloride (mM) Figure 29. Sulfate vs. Chloride data indicates diluted seawater. 44 Appendix A: Well Completion Reports Well Completion Report Project: Lake Ballard Ancient Creek Well Name: 11a Location: 36.89108N, 76.39969W Constructed by Alicia Dobyns, Jennifer MacDonald, Top of casing elevation: 1.06 m (3.49 ft) Nathan Rycroft, Gretchen Teed, Dr. Rich Whittecar Construction Date: 06/12/08 Scale (cm) Borehole Information Well Construction Information Above ground riser of 40 cm 0 0-10 cm: mud & roots (initial hole) Bentonite 50 10-70 cm: gray sand Filter pack of medium sand 100 150 200 250 300 350 Hand augered to 0.70 m Riser: Schedule 40 PVC 1¼ inch diameter 400 Joints: glued using purple primer and clear PVC cement 450 Screen: 0.010 slot PVC well screen Well developed by hand plunger and bailing to remove fines. 500 Report Approved by:______________________ Department of Ocean Earth and Atmospheric Sciences Old Dominion University, Norfolk, Virginia 45 Well Completion Report Project: Lake Ballard Ancient Creek Well Name: 11b Location: 36.89108N, 76.39969W Constructed by Alicia Dobyns, Jennifer MacDonald, Top of casing elevation: 1.09 m (3.58 ft) Nathan Rycroft, Gretchen Teed, Dr. Rich Whittecar Construction Date: 06/12/08 Scale (cm) Borehole Information Well Construction Information Above ground riser of 37 cm 0 0-10 cm: mud & roots (initial hole) Bentonite 50 10-70 cm: gray sand 70-125 cm: sand grading into gray mud Filter pack of medium sand 100 with organic matter 150 200 250 300 350 Hand augered to 1.25 m Riser: Schedule 40 PVC 1¼ inch diameter 400 Joints: glued using purple primer and clear PVC cement 450 Screen: 0.010 slot PVC well screen Well developed by hand plunger and bailing to remove fines. 500 Report Approved by:______________________ Department of Ocean Earth and Atmospheric Sciences Old Dominion University, Norfolk, Virginia 46 Well Completion Report Project: Lake Ballard Ancient Creek Well Name: 11c – VC1 Location: 36.89108N, 76.39969W Constructed by Alicia Dobyns, Jennifer MacDonald, Top of casing elevation: 1.13 m (3.70 ft) Nathan Rycroft, Gretchen Teed, Dr. Rich Whittecar Construction Date: 06/12/08 Scale (cm) Borehole Information Well Construction Information Depths of pore water samples from VC 1 Above ground riser of 40 cm 0 0-10 cm: mud & roots (initial hole) 50 10-70 cm: gray sand Sandy cuttings 100 70-140 cm: sand grading into gray mud with organic matter 150 Bentonite 200 140-260 cm: black mud with fibrous organic matter 250 Filter pack of medium sand 300 260-360 cm: gray mud with sand and 350 roots Hand augered to 3.6 m Riser: Schedule 40 PVC 1¼ inch diameter 400 Joints: glued using purple primer and clear PVC cement 450 Screen: 0.010 slot PVC well screen Well developed by hand plunger and bailing to remove fines. 500 Report Approved by:______________________ Department of Ocean Earth and Atmospheric Sciences Old Dominion University, Norfolk, Virginia 47 Well Completion Report Project: Lake Ballard Ancient Creek Well Name: 12a Location: 36.89114N, 76.39971W Constructed by Alicia Dobyns, Jennifer MacDonald, Top of casing elevation: 1.34 m (4.39 ft) Nathan Rycroft, Gretchen Teed, Dr. Rich Whittecar Construction Date: 06/12/08 Scale (cm) Borehole Information Well Construction Information Above ground riser of 25 cm 0 0-76 cm: muddy sand (initial hole) Bentonite 50 76-86 cm: gray & black sand Filter pack of medium sand 100 86-110 cm: finely bedded sand mud lamination 150 200 250 300 350 Riser: Schedule 40 PVC 1¼ inch diameter 400 Joints: glued using purple primer and clear PVC cement Hand augered to 1.10 m 450 Screen: 0.010 slot PVC well screen Well developed by hand plunger and bailing to remove fines. 500 Report Approved by:______________________ Department of Ocean Earth and Atmospheric Sciences Old Dominion University, Norfolk, Virginia 48 Well Completion Report Project: Lake Ballard Ancient Creek Well Name: 12b – VC2 Location: 36.89114N, 76.39971W Constructed by Alicia Dobyns, Jennifer MacDonald, Top of casing elevation: 1.55 m (5.07 ft) Nathan Rycroft, Gretchen Teed, Dr. Rich Whittecar Construction Date: 06/12/08 Scale (cm) Borehole Information Well Construction Information Depths of pore water samples from VC2 Above ground riser of 25 cm 0 0-76 cm: muddy sand (initial hole) Bentonite 50 76-86 cm: gray & black sand 100 86-116 cm: finely bedded sand mud lamination 116-146 cm: mud with trace amounts of Filter pack of medium sand 150 fibrous organic matter 146-156 cm: sand & mud with organic matter 200 156-366 cm: mud with fibrous organic Bentonite matter 250 Filter pack of medium sand 300 350 366-375 cm: gray mud and sand Riser: Schedule 40 PVC 1¼ inch diameter 400 Joints: glued using purple primer and clear PVC cement Hand augered to 3.75 m 450 Screen: 0.010 slot PVC Johnson well screen Well developed by hand plunger and bailing to remove fines. 500 Report Approved by:______________________ Department of Ocean Earth and Atmospheric Sciences Old Dominion University, Norfolk, Virginia 49 Well Completion Report Project: Lake Ballard Ancient Creek Well Name: 13 – VC3 Location: 36.89130N, 76.39964W Constructed by Preston Lewis, Heather Moore, Top of casing elevation: 1.62 m (5.31 ft) Gretchen Teed, Kellie Wright, Dr. Rich Whittecar Construction Date: 06/16/08 Scale (cm) Borehole Information Well Construction Information Depths of pore water samples from VC3 Above ground riser of 27 cm 0 0-120 cm: sands (initial hole) Bentonite 50 100 150 120-203 cm: finely bedded mud & sand with organic matter Filter pack of medium sand 200 250 300 350 Hand augered to 2.03 m Riser: Schedule 40 PVC 1¼ inch diameter 400 Joints: glued using purple primer and clear PVC cement 450 Screen: 0.010 slot PVC well screen Well developed by hand plunger and bailing to remove fines. 500 Report Approved by:______________________ Department of Ocean Earth and Atmospheric Sciences Old Dominion University, Norfolk, Virginia 50 Well Completion Report Project: Lake Ballard Ancient Creek Well Name: 14a Location: 36.891389N, 76.399236W Constructed by Preston Lewis, Heather Moore, Top of casing elevation: 2.00 m (6.56 ft) Gretchen Teed, Kellie Wright, Dr. Rich Whittecar Construction Date: 06/16/08 Scale (cm) Borehole Information Well Construction Information Above ground riser of 38 cm 0 0-107 cm: very compacted silty sand Bentonite 50 Sandy cuttings 100 Bentonite 107-137 cm: cleaner tan sand grading to gray sand 150 137-168 cm: clay with organic matter Filter pack of medium sand 200 168-205 cm: clay grading to gray sand 250 300 350 Hand augered to 2.05 m Riser: Schedule 40 PVC 1¼ inch diameter 400 Joints: glued using purple primer and clear PVC cement 450 Screen: 0.010 slot PVC well screen Well developed by hand plunger and bailing to remove fines. 500 Report Approved by:______________________ Department of Ocean Earth and Atmospheric Sciences Old Dominion University, Norfolk, Virginia 51 Well Completion Report Project: Lake Ballard Ancient Creek Well Name: 14b Location: 36.891389N, 76.399236W Constructed by Preston Lewis, Heather Moore, Top of casing elevation: 2.08 m (6.83 ft) Gretchen Teed, Kellie Wright, Dr. Rich Whittecar Construction Date: 06/16/08 Scale (cm) Borehole Information Well Construction Information Above ground riser of 46 cm 0 0-137 cm: sandy fill with clean sand at Bentonite bottom 50 Sandy cuttings 100 150 200 137-274 cm: silt/sand with lots of organic chunks, roots, fibers 250 Bentonite 300 Filter pack of medium sand 274-351 cm: fine grey clean sand 350 Hand augered to 3.51 m Riser: Schedule 40 PVC 1¼ inch diameter 400 Joints: glued using purple primer and clear PVC cement 450 Screen: 0.010 slot PVC well screen Well developed by hand plunger and bailing to remove fines. 500 Report Approved by:______________________ Department of Ocean Earth and Atmospheric Sciences Old Dominion University, Norfolk, Virginia 52 Well Completion Report Project: Lake Ballard Ancient Creek Well Name: 15 – VC4 Location: 36.89158N, 76.39942W Constructed by Preston Lewis, Heather Moore, Top of casing elevation: 1.04 m (3.42 ft) Gretchen Teed, Kellie Wright, Dr. Rich Whittecar Construction Date: 06/16/08 Scale (cm) Borehole Information Well Construction Information Above ground riser of 39 cm 0 0-91 cm: construction fill (initial hole) Bentonite 50 Sandy cuttings 100 91-121 cm: medium to fine grained orange/yellow sand 150 121-171 cm: medium to fine yellow sand Bentonite with black spots 171-173 cm: mud lens 173-193 cm: medium to fine sand with Filter pack of medium sand 200 black spots 193-221 cm: coarse sand yellow grading to tan 250 300 350 Hand augered to 2.21 m Riser: Schedule 40 PVC 1¼ inch diameter 400 Joints: glued using purple primer and clear PVC cement 450 Screen: 0.010 slot PVC well screen Well developed by hand plunger and bailing to remove fines. 500 Report Approved by:______________________ Department of Ocean Earth and Atmospheric Sciences Old Dominion University, Norfolk, Virginia 53 Appendix B: Sediment Analysis Reports Vibracore 1: Sediment Analysis Results Description based on visual inspection 2.486 1.383 1.698 15.579 0.980 9.225 41.589 21.810 0.419 11.778 15.456 9.777 6.890 0.931 5.773 16.155 54 Vibracore 2: Sediment Analysis Results Description based on visual inspection 0.682 0.641 0.125 1.058 5.919 20.716 9.665 3.370 2.235 15.166 9.447 6.239 0.951 8.827 6.482 16.925 55 Vibracore 3: Sediment Analysis Results 8.842 7.967 Description based on visual inspection 30.007 6.435 6.347 5.253 9.849 4.771 3.937 0.140 1.850 4.259 1.597 10.284 13.227 59.997 56 Well 14 Sediment Analysis Results Description based on visual inspection 1.235 0.797 1.328 6.467 3.067 6.108 27.141 53.857 0.908 0.928 1.197 2.517 7.737 22.385 2.125 1.032 57 Vibracore 4: Sediment Analysis Results 2.809 2.679 2.312 0.605 2.571 Description based on visual inspection 6.569 3.522 73.099 0.621 6.337 12.177 8.834 12.078 7.741 16.153 31.710 58 Appendix C: Tables Table I – YSI data collected from Lake Ballard June 2, 2008 Lake Ballard - Station 1 - N 36.89250 W 76.40062 Depth from D. O. Surface (m) Temp ( C ) Salinity (ppt) (mg/L) -1 25.7 2.8 8.1 -2 25.5 2.8 8.5 -3 24.2 2.8 7.9 -4 22.1 2.8 9.8 -5 17.1 2.8 10.4 -6 12.1 2.8 10.6 -7 10.2 2.9 0.4 -8 9.3 2.8 0 Lake Ballard - Station 2 - N 36.89236 W 76.39981 Depth from D. O. Surface (m) Temp ( C ) Salinity (ppt) (mg/L) -1 25.7 2.9 8.3 -2 25.5 2.9 8.9 -3 24.3 2.8 8.8 -4 21.9 2.8 8.5 -5 16.8 2.8 11.2 -6 12.4 2.8 10.6 -7 10.3 2.8 0.13 -8 9.1 2.8 0 -9 8.6 2.9 0 -10 8.3 2.9 0 -11 8.3 3.1 0 -12 8.7 5.7 0 -13 9.1 6.3 0 59 Lake Ballard - Station 3 - N 36.89223 W 76.39972 Depth from Salinity D. O. Surface (m) Temp ( C ) (ppt) (mg/L) -1 25.1 2.9 8 -2 25 2.9 8.9 -3 24 2.8 8.3 -4 22.1 2.8 8.7 -5 17 2.8 10.8 -6 12.3 2.7 10.5 -6.5 10.7 2.9 2.6 -7 10 2.8 0.11 -8 9 2.9 0 -9 8.5 2.9 0 -10 8.2 2.9 0 -11 8.3 3.1 0 -11.5 8.5 3.2 0 -12 8.7 5.6 0 -12.5 8.9 6.1 0 Lake Ballard - Station 4 - N 36.89295 W 76.40158 Depth from Salinity D. O. Surface (m) Temp (C) (ppt) (mg/L) -1 26.9 2.8 8.3 -2 25.9 2.8 9.6 -3 24.5 2.8 8.7 -4 23.8 2.8 3.8 Lake Ballard - Station 5 - N 36.89287 W 76.40068 Depth from Salinity D. O. Surface (m) Temp ( C ) (ppt) (mg/L) -1 26.6 2.9 8.8 -2 25.7 2.8 9.5 -3 24 2.8 9.3 -4 22.2 2.8 9.5 -5 16.6 2.8 10.4 -6 12.8 2.8 9.8 60 Lake Ballard - Station 6 - N 36.89297 W 76.40015 Depth from Surface (m) Temp ( C ) Salinity (ppt) D. O. (mg/L) -1 26.9 2.8 8.8 -2 25.4 2.8 9.2 -3 24.1 2.8 9 -4 22.4 2.8 9.7 -5 16.7 2.8 11.7 -6 12.8 2.9 11.4 -6.5 10.5 2.9 0.79 -7 9.9 2.9 0.2 -8 9 2.9 0 -9 8.5 2.9 0 -10 8.2 2.9 0 -11 8.3 3 0 -12 8.6 5.5 0 Table II – Alkalinity data for Lake Ballard (blank for dropped or no runs) Lake Ballard - Station 3 - N 36.89223 W 76.39972 Alkalinity Alk. Alkalinity (meq) Depth Alkalinity Alkalinity Alkalinity Average (meq) Std. Average (m) (meq) 1 (meq) 2 (meq)3 (meq) Dev Std. Dev 2 1.9171 1.8996 1.9112 1.9093 0.00890337 0.00726957 4 2.0342 1.9454 1.9430 1.9742 0.05197538 0.04243772 6 1.9098 1.9122 1.9155 1.9125 0.00286182 0.00233666 7 2.0350 2.0027 2.0189 0.02283955 0.01615 9 2.0080 1.9402 2.0262 1.9915 0.04532122 0.03700462 10 2.1988 2.2051 2.2020 0.00445477 0.00315 11 2.5849 2.5874 2.5862 0.00176777 0.00125 12 5.5487 5.7264 5.6376 0.12565288 0.08885 Lake Ballard - Station 6 - N 36.89297 W 76.40015 Alkalinity Alk. Alkalinity (meq) Depth Alkalinity Alkalinity Alkalinity Average (meg)Std Average (m) (meq) 1 (meq) 2 (meq)3 (meq) Deviation Std. Dev 2 1.9322 2.0072 1.9312 1.9568667 0.04359281 0.03559338 4 1.9509 1.9456 1.94825 0.00374767 0.00265 6 1.8821 1.9012 1.9146 1.8993 0.0163331 0.01333592 7 2.0059 2.0403 2.0231 0.02432447 0.0172 9 1.7136 2.1613 2.1563 2.0104 0.2570485 0.20987922 10 2.1961 2.1938 2.19495 0.00162635 0.00115 11 2.9037 2.8907 2.8972 0.00919239 0.0065 12 11.6594 11.6762 11.6678 0.01187939 0.0084 61 Table III – Well Data YSI Well Data 6/23/2008 Well Data 7/14/2008 Dissolved Dissolved Temp Salinity Oxygen Temp Salinity Oxygen Well # °C ppt mg/L Well # °C ppt mg/L 1 19.9 2.2 0.09 1 20.7 2.4 0.08 2 2 7 20.0 2.8 0.38 7 17.1 3.1 0.00 8 19.9 2.5 0.28 8 17.6 2.9 0.23 3 20.1 0.8 0.00 11a 23.0 10.0 0.15 5 17.0 0.5 0.00 11b 21.5 8.8 0.06 6 16.3 1.4 0.00 11c 16.6 2.9 0.13 11a 21.9 0.3 6.48 12a 21.3 6.5 0.10 11b 22.2 0.0 1.85 12b n/a n/a n/a 11c 15.9 5.1 0.00 13a 19.5 2.7 0.03 12a 20.0 7.2 0.01 14a 20.1 3.3 0.31 12b 20.2 3.5 0.07 14b 16.9 2.2 0.26 13a 17.9 2.4 0.01 15 21.2 1.5 0.16 14a 19.4 2.9 0.31 Creek 27.0 25.0 4.70 14b 18.3 2.2 0.59 Lake 29.5 2.9 7.50 15 23.2 1.0 0.29 Creek 26.3 18.6 6.48 Lake 28.9 2.9 5.25 62 Head Data Well Data 6/23/2008 Depth to Top of Water Bottom Amt of Casing TOC in (DTW) Head Head Depth H2O in Well # (TOC) ft m ft ft in m ft ft Notes: 1 7.64 2.33 6.68 0.96 0.29 9.51 2.83 Lake rod reading 12.06 ft 2 8.63 2.63 dry <1 7.61 dry Lake elevation 1.17 ft 7 11.09 3.38 10.18 0.91 0.28 40.99 30.81 (0.36 m) 8 10.37 3.16 9.48 0.89 0.27 26.31 16.83 Based on tide data from 3 7.75 2.36 8.18 -0.43 -0.13 10.85 2.67 6/23/08 @ Old Pt. Comfort 5 10.21 3.11 10.56 -0.35 -0.11 17.54 6.98 (2.2 ft @ time of data) 6 9.60 2.93 9.85 -0.25 -0.08 50.30 40.45 11a 3.49 1.06 2.88 0.61 0.19 3.70 0.82 Creek rod reading 11.03 ft 11b 3.58 1.09 2.66 0.92 0.28 5.51 2.85 11c 3.70 1.13 3.82 -0.12 -0.04 11.58 7.76 12a 4.39 1.34 3.77 0.62 0.19 5.55 1.78 12b 5.07 1.55 4.54 0.53 0.16 14.83 10.29 13a 5.31 1.62 5.11 0.20 0.06 6.66 1.55 14a 6.56 2.00 6.265 0.30 0.09 6.73 0.465 14b 6.83 2.08 6.46 0.37 0.11 11.49 5.03 15 3.42 1.04 2.08 1.34 0.41 7.29 5.21 Well Data 7/07/2008 Depth Top of to Casing Water Bottom Amt of (TOC) ft TOC in (DTW) Head Head Depth ft H2O in Well # 6/23 m ft ft in m (6/23) ft Notes: 11a 3.49 1.06 1.37 2.12 0.65 3.70 2.33 DTW taken after several 11b 3.58 1.09 1.45 2.13 0.65 5.51 4.06 days of heavy rain 11c 3.70 1.13 3.08 0.62 0.19 11.58 8.50 Metric conversion by 12a 4.39 1.34 2.49 1.90 0.58 5.55 3.06 OnlineConversion.com 12b 5.07 1.55 4.66 0.41 0.12 14.83 10.17 Plunger dropped in 12b 13a 5.31 1.62 5.11 0.20 0.06 6.66 1.55 14a 6.56 2.00 6.31 0.25 0.08 6.73 0.42 14b 6.83 2.08 6.55 0.28 0.09 11.49 4.94 15 3.42 1.04 1.97 1.45 0.44 7.29 5.32 63 Well Data 7/10/2008 Depth Top of to Casing Water Bottom Amt of (TOC) TOC in (DTW) Head Head Depth H2O in Well # ft 6/23 m ft ft in m ft (6/23) ft 1 7.64 2.33 6.87 0.77 0.23 9.51 2.64 2 8.63 2.63 dry <1 7.61 7 11.09 3.38 10.34 0.75 0.23 40.99 30.65 8 10.37 3.16 9.35 1.02 0.31 26.31 16.96 3 7.75 2.36 n/s 10.85 5 10.21 3.11 7.46 2.75 0.84 17.54 10.08 6 9.60 2.93 10.21 -0.61 -0.19 50.30 40.09 11a 3.49 1.06 1.31 2.18 0.66 3.70 2.39 11b 3.58 1.09 1.42 2.16 0.66 5.51 4.09 11c 3.70 1.13 7.01 -3.31 -1.01 11.58 4.57 12a 4.39 1.34 1.72 2.67 0.81 5.55 3.83 12b 5.07 1.55 4.49 0.58 0.18 14.83 10.34 13a 5.31 1.62 4.83 0.48 0.15 6.66 1.83 14a 6.56 2.00 6.17 0.39 0.12 6.73 0.56 14b 6.83 2.08 6.44 0.39 0.12 11.49 5.05 15 3.42 1.04 2.12 1.30 0.4 7.29 5.17 Well Data 7/14/2008 Depth Top of to Casing Water Bottom Amt of (TOC) TOC in (DTW) Head Head Depth H2O in Well # ft m ft ft in m ft (6/23) ft Notes: 1 7.64 2.33 6.99 0.65 0.20 9.51 2.52 No rain over weekend 2 8.63 2.63 dry <1 7.61 dry 7 11.09 3.38 10.63 0.46 0.14 40.99 30.36 8 10.37 3.16 9.69 0.68 0.21 26.31 16.62 11a 3.49 1.06 2.38 1.11 0.34 3.70 1.32 11b 3.58 1.09 2.51 1.07 0.33 5.51 3 11c 3.70 1.13 5.02 -1.32 -0.40 11.58 6.56 12a 4.39 1.34 2.75 1.64 0.50 5.55 2.8 12b 5.07 1.55 4.36 0.71 0.22 14.83 10.47 13a 5.31 1.62 4.87 0.44 0.13 6.66 1.79 14a 6.56 2.00 6.22 0.34 0.10 6.73 0.51 14b 6.83 2.08 6.41 0.42 0.13 11.49 5.08 15 3.42 1.04 2.18 1.24 0.38 7.29 5.11 64 Table IV – Pore Water Salinity Data VCI VC2 VC3 Depth mid Salinity mid Salinity mid Salinity (m) depth (ppt) Depth (m) depth (ppt) Depth (m) depth (ppt) 0 0 0 No 0.1 0.1 0.1 data 0.2 0.2 0.15 7 0.2 0.3 0.25 13 0.3 0.3 0.4 0.4 0.4 0.35 5 0.5 0.5 0.5 0.6 0.6 0.6 0.7 0.7 0.65 6 0.7 0.8 0.8 0.8 0.9 0.85 10 0.9 0.9 1 1 0.85 5 1 0.95 2 1.1 1.1 1.1 1.2 1.2 1.15 3.5 1.2 1.3 1.25 5 1.3 1.3 1.4 1.4 1.4 1.5 1.45 4.5 1.5 1.5 1.6 1.6 1.6 1.55 0 1.7 1.7 1.7 1.8 1.8 1.8 1.9 1.85 2 1.9 1.9 2 2 2 2.1 2.1 2.05 2 2.1 2.2 2.2 2.2 2.15 0.5 2.3 2.25 1 2.3 2.3 2.4 2.4 2.4 2.5 2.5 2.5 2.6 2.6 2.6 2.7 2.7 2.7 2.8 2.75 2 2.8 2.8 2.9 2.9 2.9 3 3 3 3.1 3.1 3.05 0.5 3.1 3.2 3.2 3.2 3.3 3.3 3.3 3.4 3.4 3.4 No data was recovered from VC4 due to the absence of pore water in the sediment samples. 65 Table V – Ion Chromatograph Data Lake Data June 2, 2008 June 2, 2008 June 16, 2008 June 16, 2008 Depth Sulfate Depth Chloride Station (m) (mM) Station (m) (mM) Station 3 2 1.43 Station 3 2 42.48 3 4 1.44 3 4 41.69 3 6 1.40 3 6 43.11 3 7 1.42 3 7 42.69 3 9 1.44 3 9 43.19 3 10 1.43 3 10 43.33 3 11 1.31 3 11 46.41 3 12 1.09 3 12 58.20 Station 6 2 1.38 Station 6 2 39.53 6 4 1.44 6 4 40.76 6 6 1.45 6 6 40.98 6 7 1.44 6 7 43.90 6 9 1.44 6 9 45.10 6 10 1.43 6 10 45.63 6 11 1.40 6 11 50.02 6 12 0.88 6 12 80.64 Well Data Well Data June 23, 2008 June 23, 2008 June 30, 2008 June 30, 2008 Chloride Sulfate Well # (mM) Well # (mM) 1 39.54 1 0.60 3 - 3 0.19 6 17.85 6 1.36 7 41.68 7 1.35 8 41.37 8 1.10 10 1.04 10 0.03 11A 157.48 11A 0.11 11B 113.22 11B 0.26 11C 129.07 11C 2.00 12A 100.77 12A 0.17 12B 2.00 12B 0.32 13A 44.80 13A 0.57 14A 40.30 14A 1.56 14B 30.02 14B 1.24 15 12.06 15 0.25 66 Core Data Core Data June 2, 2008 June 2, 2008 June 26, 2008 June 26, 2008 Chloride Sulfate Sample (mM) Sample (mM) VC-1 24.83 VC-1 4.52 VC-3A 62.41 VC-3A 0.34 VC-3C 100.16 VC-3C 6.79 VC-4A 29.72 VC-4A 1.83 VC-6A 128.38 VC-8A 230.66 VC-6B 73.32 VC-11A 103.67 VC-8A 136.31 VC-14 16.54 VC-8B 165.04 VC-15 4.63 VC-11A 24.66 VC-16 385.09 VC-11B 13.84 VC-24 0.90 VC-14 83.02 VC-15 39.23 VC-16 141.04 VC-18 20.12 VC-22 37.89 VC-24 24.83 67 References Allen, S. E. (2004). “Understanding Lake Ballard in Portsmouth, Virginia through the application of various field data collection and GIS techniques.” Unpublished report. Old Dominion University, Norfolk, Virginia, 9 pgs. Alexander, B., Jones, C., Schweitzer, C., Taylor, S., & Williams, J. (2007). “The sources of alkalinity and other chemical and physical parameters of Lake Ballard.” Unpublished report. Old Dominion University, Norfolk, Virginia, 63 pgs. Austin, D. D. (2005). “A comprehensive physical and chemical study of Lake Ballard, a brackish water lake in Portsmouth, Virginia.” Unpublished M.S. thesis, Christopher Newport University, Newport News, Virginia, 67 pgs. Dionex Corporation. (2002). Principles and Troubleshooting Techniques in ION CHROMATOGRAPHY. Google Earth [computer software]. (2008). Available from http: www.google.com (Hoffler Creek Wildlife Preserve Foundation, personal communication, July 2008). Ranck, T., Talley, L., & Tillman, D. (2006). “Origin of salinity in a near-coastal borrow pit lake.” Unpublished report. Old Dominion University, Norfolk, Virginia, 36 pgs. The Weather Channel. Portsmouth rainfall data [Data file]. Retrieved from http://www.weather.com Tides and Currents. (July, 2008). National Oceanic and Atmospheric Association. Retrieved July 28, 2008, from http://tidesandcurrents.noaa.gov/index.shtml. Whittecar, G. R., Nowroozi, A. A., & Hall, J. R. (2005). Delineation of saltwater intrusion through a coastal borrow pit by resistivity survey. Environmental and Engineering Geoscience, XI(3), 209-219. 68 Wolny, J. L. (1999). A study of the seasonal composition and abundance of phytoplankton and autotrophic picoplankton in a brackish water lake, Portsmouth, Virginia. Unpublished M.S. thesis, Old Dominion University, Norfolk, Virginia, 54 pgs.
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