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MINUTES June 15, 2000 3 BOARD OF HEALTH some upwelling of contamination that is actually coming up into the pond. As you move further south of the pond, the water actually drains out of the pond. The water enters in the north side and discharges from the midway point down, sinking within the aquifer. We see shallow contamination which is definitely coming into the pond, although not detectable. We have sampled the surface water where this upwelling is occurring and we are not seeing it because of the relatively low mass amount of contamination and the fact that these are large bodies of water that it's being put into." "We are talking about a mass of contamination just north of the pond. There is contamination underneath the pond. We know there is a finger and there may be other fingers south of the pond that they need to find. That is part of the land-based drilling. In theory within the next three years, this extraction fence will serve the purpose of cutting off this plume and allowing clean water to fill in through rainfall and from coming in through the sides. This area of contamination should be gone within about a 3 year window and we can move out of that Horseshoe Bend, Tri-Town Circle area." "We do have two extraction wells in the area between the ponds that we started up in January, along Hooppole Road. One is addressing the CS-10, very narrow contamination, the other addressing the lower portion of storm drain 5 (SD-5). Both of these plumes, SD-5 and CS-10 plume, discharge to John's Pond. It's proven through our on-pond drilling and other work that we've done out there. We've never seen evidence of SD-5 contamination showing up in John's Pond, however we have been able to measure very low levels of TCE contamination about 75 feet off the shore at this location, upwards of about 3 ppb 6-inches from the pond bottom in five feet of water at that location. It's a very small area of discharge and that information has been shared with the public health agencies and there is no risk at all with that." "I don't believe we've done any recent re-sampling of the water in that area." "These systems have been operational since January. Within a very short timeframe, about a 2-year timeframe, they should be effectively cutting off the contamination entering John's Pond. The groundwater flow in this area is fairly rapid so you should see this area clearing out within a year and a half." "There are two recirculation wells with a little different type of technology. Instead of pumping water out, we are actually treating below ground surface using an air stripper. They are right in the neighborhoods. Those will operate for about 7 more years, until the contamination makes its way down to the recirculation wells and the extraction wells." "We have a system of wells right at the base boundary up off of Back Road cutting off the SD-5 plume. That was installed 2'/z years ago; over the 21/2 years, because the groundwater flow rate is about 1.5-2 feet per day, there is all clean water out in that area. We are going to continue to see this back edge of the plume move down and eventually, within about a 7-year window now, Briarwood will not have any of the SD-5 plume present. At least that is what our computer modeling suggests." "We are achieving 100% r at the extraction count. There is nothing presently getting by and we don't capture gP Y P anticipate that to happen. We expect to see the same kind of separation over here P PP unless we get more data in the next 6-12 months well be able to show that separation." Mr. Karson continued, "In talking about pond testing, Elias has been coordinating pond testing for a number of years on John's and Ashumet Ponds that we've been funding. Some of that work, we've done a lot of testing over the years looking at pond water quality and not seeing any problems with the pond water quality. The detects that we saw in John's Pond associated with the upwelling of CS-10, but based on the fact sheet handed out earlier, there is a statement in there that it does not pose a