EcoSaf e Barg e r H o l lo w h y d r o geo lo g i c a l and En viron me n tal Sit e assessm e n t
Boring samples of rock cores showing fracture zones (dark splits) and infill by precipitation of calcite (white fill). Traces of residual organics are seen in various depths of the soil and indicate that the ground is not structurally sound in this area.
EcoSafe Systems, LLC Blountville, Sullivan County, Tennessee Engineering
*Not the project, but the process of obtaining core samples. To understand the subsurface environment allowing conceptual design of the entire site’s soil, rock, and groundwater interactions and mechanics, the GS&P Environmental Compliance team collected over 1,000 samples.
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Previous state geotechnical studies at Barger Hollow, near Blountville, Tennessee, had fallen short of showing exactly how a proposed new landfill would affect surrounding spring-fed streams. GS&P’s environmental compliance team reviewed years of geological information and hypothesized a new scenario to explain the inconsistent data. The concept used a harmless commercial groundwater dye injected into several access points and, mimicking a wide range of groundwater flows, showed a combination of slow-flow and quick-release of the dye into nearby streams. GS&P’s successful hypothesis proved that the proposed landfill area can be safely monitored to protect local residents and wildlife, and the research will benefit other groundwater scientists studying similar conditions throughout the Appalachian region.
A soil stratification sample showing the profile of limestone now weathered to soil in the area. This sample allows the geologists to understand the soilâ€™s permeability.
Jason Repsher, P.G.
Keith Barnhill, P.G.
Randy Curtis, P.G.
RANDY C U RTI S , J A S ON R E P S H E R
What first prompted the client to contact GS&P regarding a proposed landfill near Blountville, Tennessee?
The client was having difficulty proving the existing and proposed landfill release could be monitored. The client came to us and said this monitoring issue is something that other consultants/professionals have looked at and haven’t been able to resolve. That was the problem — how to do what hadn’t been done to that point.
Is it standard procedure to geologically review proposed landfill areas? What’s involved in monitoring an area?
Yes. It’s what everyone calls the Part IIA in Tennessee, but yes, standard policy. That’s where you end up doing the hydrogeologic site characterizations so you can understand both soil and groundwater issues on one side, and then the next phase is where you actually design a landfill based on those parameters. Jason:
old-timers just dumping food dye into a sinkhole
Everyone has to remember that the limestone at this site is sitting at a 70 degree angle in most cases. It’s not a flat tabletop where water goes in a particular spot and drains out in a semi-uniform pattern.
Randy: Think of a hay barn. You usually have a steep A-shape roof, but there is another barn next to it that’s at a lower angle. When a raindrop hits the steep roof, it can run down the tin or off the roof or into a gutter or on to the next roof. How do you figure out exactly where it’s going to go?
Based on your evaluations, what was your hypothesis?
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Randy: In actual engineering design, you say we would need to put a well here or we need to monitor a spring there, but in the hydrogeologic investigation, you are just trying to say rainfall comes onto the land here and exits the land there.
substance into groundwater to see if you could detect it. That had been tried several times by consultants and regulators in the past over about a 10-year period, ranging from the rudimentary — old-timers just dumping food dye into a sinkhole — to sophisticated protocols. What we did was look at all of that past data to try to get a feeling for why the old dye traces were failing and what we could do to make it succeed.
And what did you find at Barger Hollow?
How long did it take to evaluate the area?
The analysis took about six months, factoring in previous studies as well as current water flow conditions.
The general problem is that the area is predominantly limestone rock. Limestone, by its very nature, does not present a uniform, flat surface, but instead is made of millions of ancient sea organisms solidified and cemented with calcium allowing for the potential of springs in many areas. The technical term is karst — sinkholes and springs issuing from limestone rock — and the disconnect in the past was that people were putting dye in the ground expecting it to come out in the springs, but they weren’t seeing it. So where did it go? The question we were wrestling with was how to demonstrate a dye that would mimic a potential release from a landfill. If a landfill was leaking and you were trying to monitor it, you would put a harmless colored Randy:
Randy: Based on all the existing data, both old and new, GS&P developed a conceptual model that accounted for the various water flow issues that occur within unpredictable surfaces like limestone. We identified and focused on three types of water flow and tried various ways of mimicking each scenario. The final analysis proved that there were fast flow areas (such as in storm water situations) and slow flow areas, which explained the emergence of dye that had been placed in the rock as much as 10 years before.
Other studies didn’t completely solve the problem. How was your approach able to determine a solution?
importance of monitoring the slow flow components and its issues with potential pollutants.
Previous studies were trying to uncover definitive start and end points of water flow. We took a more holistic approach in the beginning by acknowledging that water could have any number of start and end points. We tried to mimic the entire landfill footprint (269 acres) as the start point and where water could, conceivably, come out. It was a pretty tedious process because we had to make sure we weren’t pushing water too hard in areas where we were trying to mimic natural water flow, which might have collapsed any small openings we’d created. Instead, we had to watch and wait for the water to travel on its own time so that we wouldn’t negate any new analyses.
What care and consideration were given to the surrounding community and the landfill’s affect on the environment?
Through our testing, we determined that an older landfill had, in fact, had a negative impact on the environment. The best solution is to relocate the waste from the old landfill and replace it in the proposed new one, which would be lined and have the benefit of modern technology that would allow collection of both leachate and landfill gas to reduce greenhouse emissions. The new system will also allow the tracking of a cleanup effort of the old landfill to ensure that there are no health hazards in the local water supply.
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Was the county aware of the existing landfill issues and the associated hazards?
Everyone knew about the landfill, but did not realize just how serious the situation is. Our analysis showed them the importance of stepping up their efforts to improve the area. Unfortunately, there is a lack of funding preventing them from completely taking care of the issue. The proposed landfill project will at least clean up the existing waste, and hopefully, the state will have the funds to take all the necessary steps in the near future regarding existing groundwater contamination.
It’s also our hope that folks do realize the importance of slow flow even if it’s not a part of their present scope of short time frame dye trace analysis. It may not seem so important now to someone living near a short flow system area, but if they plan to live in that area for the next 30 years, at some point in time the flow is going to reach them.
It’s clear to see how this analysis is vital for a landfill site, but aren’t there implications for other types of projects?
Sometimes going the extra mile in the beginning can save a lot of trouble later, like in the early stages of drilling and laying foundations. When drilling cores or soil borings for location of a new hotel, apartment building, or parking garage, the boring logs clearly show you have soil on certain levels, rock at certain levels, and water at certain levels. But most people are primarily concerned with reporting bearing capacity, not water levels. Furthermore, the reports usually only show conditions on the day of drilling, not a more holistic, longer-term understanding of the site. Without understanding exactly how fast and where the water flows, whole operations have had to be redesigned because evaluations didn’t assess the impact on the entire site. Once you cut the cell out of a landfill or cut the building footprint, you have changed the groundwater regime in that area by altering its natural conditions. If you’re not careful, you’ll have a nice giant bathtub that holds water below normal stream pool, regional or localized groundwater elevations for the area. Jason:
What kind of impact can your findings at Barger Hollow have on engineering and scientific studies, specifically in the Appalachian region? Randy: There are a lot of systems that address the traditional karst fast flow, but our analysis demonstrated the
Is it your hope that standards established by GS&P will have an effect on future state regulations?
We’d like to think so. As far as regulations go, right now they just tell us to look at the short term, but we think it’s important to go a step further for true protection of human health and the environment. ■
Jason Repsher, Professional Geologist (P.G.), served as project manager. His extensive experience in hydrogeology, project management, and environmental consulting was key to finding the solution for EcoSafe. Randy Curtis, P.G., served as senior geologist. Randy’s experience in hydrogeological investigations and statistical analysis proved critical for the project.
BARGER HOLLOW SITE
Existing Landfill (30 Acres) Proposed Landfill (269 Acres)
ABOVE The existing landfill site spans 30 acres of the Barger Hollow area; the proposed landfill site will span 269 acres. The understanding that this study generated will be of significant benefit to the characterization of other challenging sites in the same region.
LEFT Randy Curtis inspects soil and pebbles that have sealed the end of a cave in the Barger Hollow area. The formation shows very high flow conditions, which deposited the material at the choke point of the cave.
ø = Monitoring Points.
LEFT During the formation of the Appalachian Mountain range by plate movement in the upper earth’s surface, the site’s bedrock foundations were folded, faulted, and even thrust over one another. Weathering of the rock formations created the existing topography and subsurface geology, and was described in detail in the team’s 2,000-page hydrogeological site review.
X = Dye Injection Locations.
In addition to proving the base monitorability of the site with the work performed, GS&P also determined flow direction and end discharge locations. This knowledge enabled the owner to purchase additional property and expand the facility while reducing future monitoring costs by over $200,000 during the anticipated life of the facility.
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LEFT Because the goal of the eosine dye trace was the verification of monitorability, and the regulations governing solid waste site operations emphasize groundwater monitoring wells, GS&P targeted specific areas of the site with new dye-detection wells. The red, green, and yellow dye were injected in existing and newly constructed wells, cores, and borings, as well as in large, medium, and small sink holes. Over 1,000 samples were collected from 16 existing wells and 14 new wells.
© Gresham, Smith and Partners