TCE and SD-5 South Selectmen’s Meeting
August 11, 1999
Mashpee Town Hall

Meeting Minutes

Agenda Item #1. Introductions

Mr. Marsters convened the meeting at 6:33 PM. He reviewed the format of the meeting and welcomed State Representative Nancy Caffyn.

Mr. Snyder, the program manager for the Air Force Center for Environmental Excellence (AFCEE), stated that the purpose of tonight’s presentation is to discuss the cleanup system for the remaining portion of the Storm Drain 5 (SD-5) plume, and the trichloroethylene (TCE) plume, currently believed to be part of the leading edge of the Chemical Spill 10 (CS-10) plume. He stated that Mr. Carman of Jacobs Engineering will provide an update on the two recirculating wells that have been cleaning up the SD-5 plume, as well as AFCEE’s proposal for construction this fall.

Agenda Item #2. SD-5 System Update

Mr. Carman reported that the SD-5 North system was turned on in August 1997. He noted that the SD-5 North plume is detached, which indicates that the system is successfully removing contaminants from the groundwater. He reported that from August 1997 to May 1999, approximately 320 million gallons of water have been treated and over 33 pounds of volatile organic contaminants (VOCs) have been removed from the SD-5 North plume. Mr. Carman stated that the contaminated water is treated to non-detectable levels by carbon filtration. He explained that the water is pumped through large carbon vessels and the clean water is returned to the aquifer through a series of reinjection wells. He displayed a map of the SD-5 North well layout and explained that the red dots indicate extraction wells and the blue dots indicate reinjection wells.

Mr. Carman reported that on June 17, 1999 the SD-5 South recirculating wells were brought on line. The site restoration is complete and the roads in Briarwood were reopened on July 2, 1999. Mr. Carman reported that ongoing monitoring has been conducted since the startup of the system. He stated that the system is currently in the "shakedown" mode, during which any "bugs" in the system are being worked out. Mr. Carman reported that during the shakedown period plume constituents were detected in the off-gas. He noted that, unlike the SD-5 North system, the SD-5 South system utilizes recirculating wells. He displayed a schematic of the SD-5 South treatment systems and explained that water is extracted and brought up to an air stripper where the contaminants are stripped out of the water; air containing the contaminants is pushed through carbon vessels for filtration, and the clean air is discharged to the atmosphere. The clean water is reinjected below the plume, within the same well. Mr. Carman explained that some of the reinjected water also is recaptured, which is the recirculating well phenomenon – a certain amount of water is recirculated between the reinjection screen and the extraction screen.

Mr. Carman stated that AFCEE made a commitment to the Mashpee Selectmen that the SD-5 South design would not emit contaminants into the air. Once it was determined that contaminants were in fact breaking through, necessary steps were taken to rectify the situation. Those steps included notification of the breakthrough to the Town of Mashpee, the regulators, and the Massachusetts Department of Public Health (MDPH). Mr. Carman reported that the primary contaminant detected was cis 1,2-dichloroethylene (DCE), which was not widely detected within the SD-5 plume during the characterization for the design of this system. He noted that the levels detected were very low and although, in conference with the MDPH, it was confirmed that the detections do not pose any health-related concern, AFCEE stands by its commitment to prevent any emissions of contaminants into the atmosphere.

Mr. Carman reported that in order to address the contaminant breakthrough the carbon was changed out on July 24, 1999. In addition, the SD-5 South system was modified to a closed-loop system, thereby eliminating any emissions into the air. The modification was completed last Saturday (8/799). Mr. Carman explained that a pipeline from the effluent side of the lag carbon vessel was connected to the air stripper so that the cleaned air, which might contain small amounts of plume constituents, would be utilized to further strip the contaminants. He noted that the small amount of constituents is not expected to have a significant effect on the performance of the air stripper. He reported that, prior to going to a closed-loop system, the system was achieving 93% stripping efficiency, which is what would be expected with a recirculating well. Currently the air intake and discharge stacks are open to the vaults and, although they provide ventilation and air exchange into the vaults, they do not serve the process in terms of treatment. He stated that currently there are no emissions from the system and the system, including pressure, humidity, and heat, is being monitored. The influent and effluent values in the water, and the performance of the carbon units, also are being monitored to determine stripping efficiency. He noted that an advantage of going to a closed-loop system without any air emissions is that fuller use of the carbon units can be achieved and the carbon can be changed when breakthrough is seen on the lag vessel.

Mr. Carman reported that the success of the closed-loop modification will continue to be monitored, as will the air. The analytical data will provide evidence as to whether the cleanup goals are being achieved. Mr. Carman reported that ambient air monitoring has been done in the vicinity of the two sites on Wheeler Road and Hillside Road, and the results of that monitoring are expected back soon. He mentioned that another benefit of the closed-loop modification is that it is very quiet – it eliminates the low frequency noise associated with the discharge of the air with the previous open-loop system.

Agenda Item #3. SD-5 South/TCE Plume Treatment and Related Construction

Mr. Carman reported that this project includes the installation of two extraction wells along Hooppole Road, one to address the SD-5 South plume and one to address the TCE plume. The pumping rates for the TCE plume would be 75 gallons per minute (gpm), and 100 gpm for the SD-5 South plume. Mr. Carman displayed a map of the TCE/SD-5 South plume extraction well and pipeline layout (see attachment #1) and identified the extraction well for the TCE plume, the extraction wells for the SD-5 South plume, the recirculating well at the intersection of Highland Road and Hillside Road, and the recirculating well at Wheeler Road. Mr. Carman stated that "these" two wells are different than the recirculating wells in the axis of the SD-5 plume in that they are solely extraction wells. He explained that the water will be extracted and pumped to the Sandwich Road Treatment Facility – treatment will not occur in the neighborhood; the water will simply be extracted and piped.

Mr. Carman reported that the well pumps will be monitored and controlled at the existing Sandwich Road Treatment Facility. The water will be transmitted via double-wall piping to the Sandwich Road Treatment Facility, where it will be treated. The treated water will be reinjected within the existing SD-5 North wellfield. Mr. Carman reported that the system will pump 175 gpm, which is about 6% of the 500,000 gallons per day (gpd) total flux into Johns Pond. He noted that there will not be any significant drawdown that would affect Johns Pond, and the system should not cause any undesirable effects on the operation of private wells in the area.

Mr. Carman displayed a slide titled "SD-5 South and TCE Plume Remedial System Capture Zones." He stated that the TCE plume, which flows across the isthmus from west to east, could be captured by pumping at a rate of 45 gpm. The TCE plume remedial system employs a rate of 75 gpm to ensure that the full extent of the TCE plume is captured. He stated that the well located on Hooppole Road, which will address the SD-5 South plume, will employ a rate of 100 gpm and will have a comparably larger capture zone. He explained that the larger capture zone is mainly due to the effects of the extraction occurring in the axis of the plume. He further explained that as the extraction wells are lined up parallel to groundwater flow, they build upon each other, resulting in an additive effect of capture zones, which will allow for the capture of over 98% of the available mass for the SD-5 South plume. Mr. Carman noted that these three wells are expected to operate for approximately six years.

Mr. Carman reported that the extraction well for the TCE plume will effectively capture 100% of the available mass upgradient of that well. He noted that the period of operation for that extraction well is undetermined, pending collection of further information underneath Ashumet Pond and further design work. He stated that the extraction well for the TCE plume will likely be located in the adjacent unpaved portion of the road easement of the Town of Mashpee, which is an area that has some clearance. The intent is to stay out of the road if at all possible. The SD-5 well, however, is located on Hooppole Road, just south of the state boat ramp, and is expected to be finished within the paved portion of the road.

Mr. Carman reported that all of the construction activities for the wells and the pipeline will utilize the existing town road easements within the Town of Mashpee. The northern portion of the pipeline will be just north of the southern boundary of the base. He stated that each well will be approximately 150 feet deep and will have an 8 X 6 foot concrete vault at the surface of the wellhead to allow for valving and controls within the well. The total length of the pipeline is approximately 5800 feet – the portion of the pipeline on Hooppole Road is approximately 3500 feet. The pipeline consists of a double-wall pipe with a 6-inch interior pipe with a 2-inch annulus, within which there is space intended to provide additional security should a leak occur. The outer diameter of the containment pipe is 10 inches. Mr. Carman reported that the proposal is to open-cut a trench for the pipeline, which will require periodic closure of Hooppole Road. He stated that the intent is to stay within the paved portion of the road for the placement of the pipeline in order to minimize impacts on adjacent property and landscaping and to minimize residential concerns.

Mr. Carman reported that once the well drilling is complete, the pipeline construction will be initiated. He explained that the construction would proceed from the intersection of Highland Avenue and Hooppole Road to the north, with the intent of completing that portion prior to the onset of cold weather. He stated that, as part of the restoration plan, AFCEE would like to resurface Hooppole Road this fall. After well drilling is complete, a 600-foot run of Hooppole Road, from Highland Avenue to Hillside Avenue, would be cut and the pipe would be installed beneath the existing laterals for residential drinking water. The approximate depth would be four feet to the top of the pipe and the cut may be as deep as 5.5 feet. Once that cut is back-filled and cold patched, AFCEE would proceed to the next block. Mr. Carman displayed a map and explained that the initial 600-foot run would be followed by construction occurring in 300-foot runs. He explained that a portion of the road would be closed, the pipe would be installed, the cut would be back-filled, the road would be cold patched and reopened to traffic, and the process would proceed to the north.

Mr. Carman reviewed the schedule summary. He reported that a draft wellfield design report was completed on July 12, 1999 and has been sent to the Massachusetts Department of Environmental Protection (MA DEP). Engineering and pipeline design is scheduled for completion in mid-September 1999. He stated that there are major procurements for drilling, pipeline construction, excavation and installation of vaults, and project mechanical work. Electrical and Instrumentation (E&I) subcontract work also will be part of this effort. Mr. Carman reported that the procurement portion of this effort is expected to conclude around November 1999. Extraction well drilling is anticipated to proceed after Labor Day and extend to the end of October 1999. Upon completion of the extraction well drilling, the plan would be to initiate excavation and vault installation, and then proceed with pipeline construction on November 1, 1999. Mr. Carman reported that pipeline construction to the Sandwich Road Treatment Facility is expected to be concluded by December 31, 1999, mechanical and E&I activity will extend into January 15, 2000, and the anticipated system startup date is January 31, 2000.

Mr. Carman reported that in the spring of this year AFCEE and the Town of Mashpee developed a management plan to help guide construction activities and interaction with the neighborhood. This plan includes: public notification, which involves a public hearing; certified residential mailing to abutters, which has been completed; preparation of news releases to advise the public of plans and progress; and a site visit for selectmen. He noted that yesterday a number of selectmen visited the site to view the layout of the project.

Mr. Carman stated that AFCEE does not anticipate any noise issues; however, noise monitoring will be conducted to ensure that objectionable noises to the public are not generated and are within safe levels. He noted that necessary measures will be taken to mitigate noise where possible. He reported that the work hours established by the management plan are Monday through Friday, from 7:30 AM to 6:00 PM, with actual motors and work starting at 8:00 AM, and on Saturday’s from 8:00 AM to 4:30 PM, when required. Mr. Carman stated that police detail would be required, and security fencing would be employed to provide a safe mechanism to prevent unauthorized entry and provide containment of the construction zone. He reported that the Department of Public Works (DPW) will be involved in technical review of the plans and designs. Mr. Carman noted that this morning he and Mr. Carl Gustafson met with Mr. Greg Taylor from the DPW to review the details being discussed tonight. Coordination also will be conducted with the Mashpee Police and Fire Departments. The Board of Health is expected to conduct periodic site inspections to ensure that the public health and environmental concerns are "well-in-hand" during the execution of the construction.

Agenda Item #4. Question and Answer Session

Mr. Lewis introduced himself as a resident of Hooppole Road and member of the Public Information Team (PIT). He then asked, in regard to the two wells installed at Wooley Park and Wheeler Road, if the closed-loop system that is currently being "experimented" with, potentially means the removal of the utility pole and the pipes. Mr. Carman replied that although he does not have a definitive answer, AFCEE understands that the Briarwood residents want those items removed, and an attempt will be made to accommodate the request.

Mr. Lewis then asked Mr. Carman to explain why the treated water will be reinjected within the existing SD-5 North wellfield rather than return the clean water to the "other end" to be reinjected. Mr. Carman replied that 175 gpm is a very small amount of water relative to the daily flux into Johns Pond. He stated that economically it does not make sense to run that pipeline back down to the area where the water was withdrawn. He explained that if there were a problem with the piping system, then the complications would double. He said that it is much simpler to add the 175 gpm to the water that is already being reinjected. Mr. Lewis commented that the people need to hear that the water level of the lake will not drop down as a result of utilizing the single pipe system. Mr. Carman assured him that it would not.

Mr. Lewis asked if a decision has been made regarding the use of open trench versus horizontal drilling on Hooppole Road. Mr. Carman replied that operations are continuing as if the open-cut method will be implemented. He noted that AFCEE has made requests for proposals and plans from subcontractors for trenchless designs, but it does not want to experiment in this area. The current plan is to use a "tried-and-true" method that can be utilized in a manner that will limit impacts. He stated that there are advantages and disadvantages associated with trenchless technology. Mr. Carman emphasized the importance of making sure that the chosen contractor has sufficient experience, that it is competitive, and that the best plan is selected. Currently AFCEE believes that the open-cut method will allow the project to proceed most effectively. Mr. Lewis commented that he raises this issue because it is his understanding that if AFCEE were to proceed with horizontal drilling, there would be "big machines with a lot of noise." Mr. Carman said that horizontal drilling is essentially like conventional drilling, so there would be a machine that would be in a certain area for a period of time. Mr. Lewis asked if the residents would be informed of that decision before the activity begins. Mr. Carman replied that they would.

Mr. Lewis then suggested that if flower gardens or lawns located within the first six feet of the roadside would be disrupted during construction, that residents should be informed ahead of time and assured that any disrupted area will be restored. Mr. Carman stated that AFCEE intends to maintain this type of communication with the residents. He then stated that although through traffic would be limited for portions of the road at different times in the project, access to homes would always be maintained. The only exception would be for a short period of time, when the construction is moving past someone’s driveway, and those residents would be notified in advance.

Mr. Marsters referred to yesterday’s site visit for the selectmen and noted that Mr. Carman had indicated that all of the open trenching would be within the paved portion of the road and not on road easements to prevent interference with electrical, water, telephone, or cable installations. Mr. Carman said that this correct, and added that the intent is to maintain the activity within the paved portion of the road. There would always be the potential, however, for a bush to get knocked over or a flower to get trampled. He reiterated that the objective is to restore the site to its original condition.

Mr. Blythe asked if AFCEE plans to "mark off" where the trenching will be done, as a way to notify the residents prior to the activity taking place. Mr. Carman replied that residents will either be notified door-to-door, or a site plan will be developed and distributed to the residents that shows where the construction will be occurring. He said that markers could be put up, and caution tape will be used to delineate the zone of construction. Mr. Blythe asked if the "spoils" are going to be on the road layout and not on private property. Mr. Carman replied that this is the intent.

Mr. Tides, a resident of Hooppole Road, said that he would like to see additional "No Parking" signs at the boat ramp. He commented that most people overflow the boat ramp area and park alongside the road. He also suggested that school buses exit the area via Sandwich Road in order to take advantage of the traffic light at Route 151. He said that he believes that the exit near the Barnstable County Fairground is an "accident waiting to happen."

Mr. Baker commented that Mr. Carman had said that 33 pounds of VOCs were removed in 320 million gallons of water. He then asked for a comparison between what that amount is in parts per billion (ppb) and the average numbers seen in the extraction wells for the SD-5 plume. Mr. Snyder replied that the average influent concentrations from the SD-5 North plant have always been below 5 ppb of total VOCs. He explained that the 33 pounds of VOCs removed is only equivalent to a lot of water being pumped. Mr. Baker asked what the average concentration level in the plume is in ppb, and what the 33 pounds out of 320 million gallons of water is in ppb. Mr. Snyder replied that the maximum concentration in the northern part of the plume is approximately 40 to 50 ppb of TCE. He stated that because so much additional water is pumped up to capture that plume, the influent has always been less than 5 ppb of total VOCs. He stated that there are higher concentrations that define that groundwater contamination zone, but by the time it is captured in a well and pumped to a plant, it has been diluted to about 5 ppb. Mr. Baker asked if it is correct that 33 pounds in 320 million gallons of water is a number less than five. Mr. Snyder replied that this is correct.

Mr. Baker then asked if there is a method that would indicate a leak in the inner wall of the double-wall pipe. Mr. Snyder replied that there are lower points in the line where moisture will collect – if there is build up in the lower points of the line, it would be captured and brought to the well vault. He added that the pipeline is welded construction and could only be broken if a backhoe actually went through it. He noted that each section of the pipeline is tested as it is installed. Mr. Baker asked if it is correct that if there were a leak, sooner or later it would end up in the "well house?" Mr. Snyder replied that this is correct. He stated that sensitive electronic detection lines were considered; however, at the FS-12 system, for example, this type of detection line was set off from just the moisture buildup in the system.

Mr. Baker asked if there is a built-in monitor in the closed-loop system to indicate that the carbon strippers are being effective and the air being reinserted into that well is in fact clean or close to clean. Mr. Snyder replied that the carbon still needs to be tested. The output side of the second carbon vessel is being tested and will be sampled on a frequent basis to make sure that the VOC levels have not risen. He stated that AFCEE expects that the low levels of cis 1,2-DCE may continue; however, that air stream will continue to be monitored.

Mr. Baker asked if it is correct that "less-than-clean" air will be used and sampled on a periodic basis, but there is nothing that samples the air on a continuous basis. Mr. Snyder replied that the levels coming off the carbon are so low that no continuous monitors are effective. Mr. Baker asked if it was like a process control method, whereby samples will be taken periodically. Mr. Snyder replied that this is correct.

Mr. Baker asked if there is a sampling plan, and if there is, whether calculations have been done to determine a confidence level in terms of accuracy of that sampling plan. Mr. Carman replied that during the shakedown period, prior to the detection of a breakthrough, samples were collected on a weekly basis. The sampling frequency has been increased to twice a week, a frequency that is believed to provide the information required. He stated that the follow-up sampling conducted since the carbon change-out indicates that the TCE is being adsorbed. Cis 1,2-DCE is present in very low concentrations and is not stripped effectively by carbon. Mr. Carman also stated that a small amount of cis 1,2-DCE may remain in this closed-loop system; however, the presence of the cis 1,2-DCE should not have a significant effect on the ability of the system to strip the TCE. He reported that monitoring will continue on an increased frequency for the breakthrough of TCE.

Mr. Baker commented that sooner or later the cis 1,2-DCE ends up going back into the water that leaves the well site. He then said that what AFCEE is doing is a sampling, and there are old fashioned calculations that are very simple to do, which provide a confidence level of how accurate the sampling represents the universe being investigated. He then asked if those calculations have been done, and if not, whether they will be done, and whether AFCEE will inform the public of that confidence level. Mr. Snyder replied that sampling protocols for the water or air filtration are established to ensure that the saturation point is captured. He added, in regard to Mr. Baker’s comment that the recirculated cis 1,2-DCE would get back into the water with which it is being percolated, that all of those compounds have a higher affinity for air than water – given the opportunity, those compounds will remain in the air stream. Mr. Baker commented that this is correct until the air becomes saturated in the closed-loop system. Mr. Snyder agreed, but added that the system is a long way away from saturation.

Mr. Baker asked if the amount of water going into Johns Pond every day is about 500,000 gallons. Mr. Carman replied that this is correct. Mr. Baker then asked if the amount of water that would be pumped is 6% of the daily flux into Johns Pond. Mr. Carman replied that this is correct. Mr. Baker then said that 175 gpm is about 200,000 gpd, which is about 40% of 500,000 gpd. Ms. Armstrong, from Jacobs Engineering, clarified that the flux through Johns Pond is approximately 500,000 cubic feet per day.

Mr. Baker then stated that in the presentation there was discussion of the Board of Health (BOH) "doing something," about the DPW "doing something," and every time he attends town meeting the BOH wants more money and the DPW wants more money. He said that they do not get everything that they ask for, but they usually get a little bit, and that little bit comes out of taxpayers’ dollars. He commented that he feels that if there were only one person doing a job and that person had to work a little bit harder to cover these areas, then the cost would not be a meaningful thing, but that is not the way the world operates anymore. He explained that people are looking for overtime, people are looking for additional employees, and all of this represents a cost to the town. He questioned when the federal government is going to stand up and recognize the cost it is imposing upon the administration of this town, and do something about it.

Mr. Orlando asked Mr. Carman to define DCE. Mr. Carman replied that TCE degrades naturally and one of the breakdown products, commonly seen in these plumes, is DCE. He added that DCE was seen in isolated locations within the SD-5 plume, but it was not widely detected. Mr. Carman noted that the maximum contaminant level (MCL) for DCE is 70 ppb, and the MCL for TCE is 5 ppb. Mr. Orlando asked why DCE was found at "this" location and not anywhere else. Mr. Carman replied that the wells were strategically placed to address the largest mass within the SD-5 South plume. Some concentrations of TCE, which are higher than anticipated, are being seen. He said that it could be that there is more DCE than anticipated and that is affecting the system. There also was speculation that the TCE is breaking down; however, TCE degrades to DCE under anaerobic conditions and that is not the condition in this system.

Mr. Orlando commented that he is happy with the closed-loop system if it works. He then asked if there would again be a problem with the carbon filters if it were necessary to go back to using the intake. He then inquired about the possibility of a device that would shut down the entire system if VOCs were detected on the other side of the carbon filter. Mr. Carman replied that this is a point that can be explored. Mr. Orlando commented that he would like it to be more than explored – he said he feels that the Board of Health should insist upon it, and the system should be shut down if it does not have such a device.

Mr. Orlando then commented that now that the CS-10 plume is upwelling into Ashumet Pond, although extraction wells were installed to prevent the plume from going into the pond, it now seems that there is a greater amount of VOCs entering the pond. He asked what will be done to address the greater amount of VOCs entering the pond. Mr. Snyder replied that in May 1999 the Sandwich Road Fence was turned on and it is cutting off the plume upgradient of Ashumet Pond, at the base border. He stated that what is being seen is the tail end of the CS-10 plume that will be coming into Ashumet Pond – by the time a system is installed there, there would not be a good chance of capturing any plume mass before it got underneath the pond shoreline. Mr. Orlando asked where the CS-10 plume is being detected in the pond. Mr. Snyder referred to where SD-5 upwells into Johns Pond, and stated that there is a similar footprint, 100 feet off the Ashumet Pond shoreline, where CS-10 is located. He noted that both Ashumet Pond and Johns Pond draw from the groundwater on the uphill side, which is believed to be pulling the top part of CS-10 up, and the portion of the plume that is under-running the pond is ending up as the TCE plume. He added that the portion of the plume that did not make it into Ashumet Pond was pulled up high enough to be influenced by Johns Pond’s vacuum effect.

Mr. Orlando inquired about the concentrations in the pond. Mr. Snyder replied that currently there is no water data from samples collected in the pond. He noted that vapor diffusion samplers were used to identify a footprint where VOCs are coming through, and drilling is being done through the pond bottom in the areas of the highest vapor sampler readings.

Mr. Orlando asked if the portion of the CS-10 plume that is under Ashumet Pond would come up on the other side of Ashumet Pond and head towards Johns Pond in a different area. Mr. Snyder replied that part of the investigation with the barge on the pond, is to connect the dots from "here" to the edge of the CS-10 plume. He said that this may lead to other areas, and pointed to the area that is the only place CS-10 has come out to date. Mr. Orlando asked if there could be more drilling north of that area. Mr. Snyder replied that this is possible. He pointed to a location on the map and stated that it is unlikely that there would be drilling north of there because a lot of the wells in the SD-5 investigation went to bedrock, so the chances of another plume being in that zone are not likely. He stated that the groundwater model predicts that most of the CS-10 plume comes through the northern part of Ashumet Pond and is caught up in Johns Pond’s influence.

Mr. Orlando commented that although the CS-10 plume has been cut off, there is still a portion of it yet to go through. Mr. Snyder agreed and added that the model predicts that that portion will come "this" way. He explained that the well and the pipeline have been built with a flow capacity to handle much more water than is currently being proposed, just in case the plume footprint does get wider in the future.

Mr. Orlando then asked if the recirculating wells could be converted to pump and treat wells if needed. Mr. Snyder replied that this is possible and could be considered.

Ms. Caffyn commented that it is amazing to her that a year ago natural attenuation, with no pumping, was proposed. She stated that it astounds her that so many elements are being put forth and commented that this seems very "patchwork." She said that she understands that the TCE plume was discovered, but if her memory is correct, originally five recirculating wells were recommended to address the SD-5 plume. She questioned whether the plume is bigger than the system can handle, whether a comprehensive analysis of the plume itself is being done, and whether the proposed equipment is going to be adequate. Mr. Carman replied that the SD-5 plume footprint was found to be smaller than originally thought, so it required a lower rate of extraction and fewer wells to capture the plume. He added that "these" wells are positioned where they can and are accepting the largest mass of the plume. He stated that going with an axial approach and adding this well "here" will effectively capture 98% of the available mass.

Mr. Snyder attributed the patchwork description of the SD-5 process to the discovery of the TCE plume. He stated that it was important to be careful with the proposed leading edge recirculating wells because of the potential that they might smear the TCE plume in areas where AFCEE did not want it moved. He said that if the requirement for an extraction well instead of a recirculating well had been known, a different approach might have been taken. He explained that there was a schedule and part of a design was ready to go – when AFCEE proposed doing less or doing nothing at all in that plume, the general sentiment was "get busy with what you have on the board," and then a decision was made to go forward with half of the recirculating well system. Mr. Snyder explained that if a decision had been made to wait until the full concept for design was established, those recirculating wells, more than likely, would have ended up being extraction wells.

Ms Caffyn asked if the choice would have been extraction versus making the two extraction wells into recirculating wells. Mr. Snyder replied that this is correct. He explained that the high concentration and the fast water movement in the TCE plume are not conducive to recirculating wells.

Ms. Caffyn asked if Mashpee’s consultant, Mr. Bill Fisher, is reviewing and overseeing this process. Mr. Marsters stated that a packet of information about this proposal was sent to Mr. Fisher yesterday. Ms. Caffyn commented that the proposal involves many fragments, the system is not one that is normally seen, and she feels that the proposal is "spotty at best." She also said that for years she has requested testing in Ashumet Pond, and she was assured that the CS-10 plume was going under the pond, and now it is understood that perhaps the plume is upwelling into Ashumet Pond. Ms. Caffyn also remarked that the history of this problem is very long and exhausting for the affected residents. She then noted that Briarwood was diagnosed with a problem approximately 20 years ago. She further commented that it is very sad that this system does not seem to be pulled together – there are different systems, systems that are not working correctly, and the possibility of future monitoring problems. Ms. Caffyn stated that perhaps the best approach would have been to have piped the contamination, which is now being proposed. She said that she is disappointed with the way this has turned out.

Mr. Snyder stated that the system will be effective at capturing the groundwater – the recirculating wells are capturing and removing mass. The only problem encountered is the air emissions issue, which was not foreseen by the vendors who developed the technology, and corrective measures are being taken. He stated that the systems are working in terms of groundwater treatments, and although it may look piecemeal, it has been built very carefully, with every step taken into consideration for what needs to be done next. Mr. Carman added that the data that was required to define the TCE plume, to the extent that it is known now, was developed fully in February 1999 – and now, just a few months later, there is a plan to remediate that plume.

Mr. Marsters stated that there has been discussion about bad emissions problems, and he agrees that closer monitoring is necessary and that the carbon filtration system should employ an alarm that would shut down the system if anything were being emitted into the air. Mr. Snyder stated that this could be considered. He also said that the closed-loop system eliminates the emissions problem. He added that there is not a method that is sensitive enough to detect the levels currently being seen. Nevertheless, AFCEE will continue to look for more sensitive methods and will share any new information with Mr. Fisher.

Mr. McQuaid commented that it seems to him that if DCE is not being adsorbed to the carbon filters, and the loop is being closed, the concentrations of DCE are going to keep increasing in the closed-loop system to a point where even TCE is not going to be adsorbed to the carbon. He then asked what would be done with the contaminated air mass located inside the system when and if that happens. Mr. Hodge, from Jacobs Engineering, replied that there is no accumulation of VOCs in the gas stream as it is recirculated around the system. He explained that the air phase reaches equilibrium with the water phase and there is no mass transfer, and therefore, there is no accumulation.

Mr. Carman added that on many similar projects, under regulatory environments that operate under the same laws that are established here, a carbon filtration system would not be required, and those emissions would be allowed to discharge. He reiterated that AFCEE has made a commitment to go above and beyond what is required, based on the wishes of the community. He said that the levels detected are so low that they could be attributed either to materials that are used in the construction of the system, or to materials coming off of the paving that was done in the neighborhood. He noted that other constituents associated with paints or glues used in the construction of the site were also detected.

A member of the audience stated that at a previous meeting he heard that there are plans to widen and repave Hooppole Road as part of the after-phase in the spring of 2000. A member of the board replied that this is being considered in order to provide more shared access to walk along the road. The audience member then suggested that if this were to occur, it should be coordinated with the DPW in order to help mitigate some of the cost to the town.

Mr. Leveille stated that Mr. Carman had indicated that AFCEE would be re-paving Hooppole Road. He then asked if the re-paving will occur only where Hooppole Road was disturbed during construction. Mr. Carman replied that this is correct, and noted that the section of Hooppole Road from Highland Avenue to Back Road is expected to be disturbed during construction.

Mr. McQuaid referred to his earlier question and asked if the issue of equilibrium means that once equilibrium is reached, the DCE will remain in the water and there is no concern because the concentrations are so far below the MCLs. Mr. Carman replied that this is correct.

Mr. Lewis inquired about the status of the recent electrical outage on Wheeler Road. Mr. Carman replied that as of August 7, 1999, both sites have been in full communication with the Sandwich Road Treatment Facility. Mr. Lewis asked if there is a monitoring mechanism that would alarm in the event of a power outage, and if a similar method would be used for the pumps when this installation is complete. Mr. Carman replied that such a mechanism would be implemented.

Mr. Lewis asked Mr. Snyder to discuss the success of SD-5 North. Mr. Snyder explained that, based on the monitoring program, the SD-5 North plume is detaching from the extraction fence. He stated that the trailing edge of SD-5 is coming to the wells currently in place and to those being installed in the Briarwood neighborhood. He referred to the map displayed and said that the "clean space" shown on the map, where there was previously a contamination plume drawn, is the real measure of success of what AFCEE is trying to accomplish.

Mr. Keaney from the Upper Cape Codder newspaper noted that earlier it was said that if there were a break in the lag vessel with the closed-loop system, a change in carbon could be made. He then questioned why this was not in the original design. Mr. Carman explained that the original design was an open-loop system where clean air would be drawn in, used to strip the contaminants out of the groundwater, and sent through a primary and secondary carbon unit. The commitment was to not have emissions of plume constituents in the air. He stated that there were three sample points, one located upstream of the primary carbon, one located between the two carbons, and one located downstream of the secondary carbon. These sampling locations allow for a safety valve, so when the contaminant breakthrough was detected, a change-out could be performed and breakthrough on the second vessel could be avoided. Mr. Carman explained that with the closed-loop system, there is no longer the need for that safety valve, breakthrough can be monitored "here." There will not be any emissions, and therefore, the mass of carbon can be utilized more effectively, and when a breakthrough is detected, a change-out can be performed. Mr. Keaney commented that the closed-loop system seems better than the original system that discharged the air, and asked why this was not in the original plan. Mr. Carman replied that recirculating well technology is a patented technology and the subcontractor that designed this system had not performed a closed-loop system prior to this project. He stated that AFCEE agreed to explore the design for an open-loop system, but the thought remained that it might be necessary to go to a closed-loop system. He added that it was understood that the community preferred a closed-loop system, but it was not a tried-and-true technique.

Mr. Snyder added that the system initially was piped in such a way that, if necessary, it could be converted to a closed-loop system. He also stated that air strippers are often used for groundwater treatment systems, in lieu of a carbon filtration unit, and not necessarily with the recirculating well approach.

Mr. Keaney asked if this closed-loop system is being used anywhere else. Mr. Carman replied that he is not aware of another site where this particular patent is being used. He added that there are other closed-loop recirculating well designs – one was pilot tested at the CS-10 site, but it did not work as effectively. He noted that the system used at the CS-10 site was a totally different patented approach, and was much noisier than the system being proposed for this site.

Mr. Cahalane acknowledged that this system was designed to be open-loop and it is now a closed-loop system. He then asked if it is correct that no one has any idea whether or not this system will work. Mr. Carman replied that the theory of closed-loop is well established. He also noted that AFCEE did not want to initially propose a design that had not before been proven by its subcontractor. He said that AFCEE explored the advantages and disadvantages of closed-loop and it felt confident that, if needed, an adjustment to closed-loop could be made. An attempt is being made to make that adjustment now and AFCEE is encouraged at this point. Mr. Cahalane asked if this is an experimental stage in that this system was not built to be a closed-loop system. Mr. Carman replied that accommodations were built into the system that allow the open-loop system to be converted to a closed-loop system. He stated that closed-loop is not something that is totally unique – this project is not in the research and development stage.

Mr. Snyder added that the closed-loop technology has been used more extensively in Germany and Europe. He stated that the air is being recirculated across the water and the main concern is with the possibility of moisture saturating the carbon. He explained that the concerns are more related to the operational aspect of the system, and noted that engineering problems do not typically arise with the closed-loop system. He also noted that the closed-loop system would not fail because of moisture buildup. Mr. Cahalane asked how long this system would be operating. Mr. Snyder replied that it would be operational for approximately six years. Mr. Cahalane asked if the system would be monitored for six years. Mr. Snyder replied that it would.

Mr. Bowman asked why the wells are being drilled to the same depth of 150 feet if the TCE plume is at one depth and the SD-5 plume is at another. Mr. Carman referred to the cross-section that shows the relationship of the TCE plume to the SD-5 plume. He explained that in the plane of that section the two plumes are vertically separated. He stated that the SD-5 South plume is somewhat thicker to the north, which leads to a common depth for the extraction wells. Mr. Snyder added that the wells will not be screened at the same depths, rather they will be screened based on the location of the contaminants at the plume location.

Mr. Bowman commented that many different types of glues were used to construct the system and the plastic exhaust and intake pipes. He asked if the glue or the plastic used contains TCE or DCE, and if there is a possibility that this is what was detected. Mr. Snyder replied that a lab scale test of that is currently being conducted. He explained that some of the piping was reconstructed and put in a sample chest, and after it sat for a while, an air sample was pulled. Mr. Bowman asked if it is a possibility that the detection of DCE came from the system. Mr. Snyder replied that it is a possibility. Mr. Carman added that toluene, which can be associated with freshly glued polyvinyl chloride (PVC) fittings, was detected. Mr. Snyder also added that if tape containing toluene is used when collecting water samples, it will contaminate the samples.

Mr. Bowman expressed concern about the construction on Hooppole Road interfering with the water lines. He noted that the water lines have tracer copper on them so that their location can be identified. He also stated that some of the water lines are located less than five feet underground, so the construction crews should be certain that all the water lines are marked.

Mr. Leveille commented that, although as a layman he feels this proposal looks good and makes a lot of sense, he wants to make sure that Mr. Fisher’s opinion on the proposal is sought as soon as possible.

A member of the audience commented that part of the problem with the recirculating wells is that the carbon does not filter the DCE. He asked, should the closed-loop system not work, if there is a way to filter the DCE out using a different type of filtration. Mr. Carman replied that other options could be explored, such as turning those recirculating wells into extraction wells, or adding additional carbon.

Mr. Wayne Taylor asked who would maintain the cold patching in the winter months when the roads are dug up with plows. Mr. Snyder replied that AFCEE, working with the DPW, will repair any cold patch that fails or sinks during the winter months. Mr. Greg Taylor added that hot mix is available through the winter from a plant just off Cape, so cold patch might not have to be used at all. He said that other methods that would allow the road to be patched as soon as possible were discussed today.

Mr. Wayne Taylor asked how a normal winter could affect the trenching. Mr. Snyder replied that most of the trenching is scheduled to be complete by December 1999 – any snow or heavy ice at that time is pretty rare. Mr. Taylor asked if security and signage would be in place. Mr. Snyder replied that it would. Mr. Taylor asked if police officers would help residents getting to and from their homes. Mr. Snyder replied that they would.

Mr. Marsters asked Mr. Carman to address the issue of residents not being able to access their homes for a short period of time during construction. Mr. Carman explained that as a backhoe is used to drill a hole in front of someone’s driveway, for a matter of hours it would be infeasible to get a vehicle in or out of that driveway; however, AFCEE intends to be in contact with the residents and will provide advanced notification of this activity so that the residents can plan accordingly.

Mr. Lewis asked if installing the two wells will be initiated first. Mr. Carman replied that initially the pipeline construction would proceed in late October 1999. Mr. Lewis inquired about the size of the vaults. Mr. Carman replied that the vaults would be 8 X 6 feet. He said that the idea would be to get the pipeline construction initiated, and it is estimated that the first 600-foot leg would take seven days, and it would take two days for the subsequent 300-foot legs. Mr. Lewis asked if Hooppole Road will be closed for a couple of days with each section of construction. Mr. Carman replied that this is correct. Mr. Lewis inquired about access for school buses. Mr. Carman replied that AFCEE will coordinate with the town as the construction proceeds.

Mr. Snyder asked when the Mashpee Board of Selectmen will indicate if it approves AFCEE’s process. Mr. Whritenour stated that there are steps that need to be taken prior to a recommendation from the Board of Selectmen. He stated that the Selectmen would like first to receive a formal recommendation from the town’s consulting engineer, the DPW, the Health Department, and the Police and Fire Departments. Mr. Whritenour said that he would like to hear from Mr. Greg Taylor regarding the issue of what impacts this construction may have to the drainage in the area, and what remediation will take place to ensure that there will be adequate drainage in the post-construction phase. He stated that the Board of Selectmen has a meeting scheduled for August 23, 1999 and this item is on the agenda for consideration. Mr. Snyder asked if this issue will be brought to the Selectmen’s agenda once all of those items are addressed. Mr. Whritenour replied that this is correct, and added that an attempt will be made to expedite this process.

Agenda Item #5. Adjourn

Mr. Marsters adjourned the meeting at 8:00 PM