ROCKPORT — Now that core sample drilling has been completed at the Mid-Coast Solid Waste Corp. transfer station on Union Street in Rockport, manager Jim Guerra hopes that the engineers can easily come up with a solid plan to staunch the continuous flow of water from the north quarry into the south quarry.

Because the water from the north quarry flows into the south quarry and makes contact with the waste there, it becomes leachate and must be treated. If the water from the north quarry stayed put, and remained as clean at the surface as it is today, it would be allowed to spill off as storm water. Much like at Drinkwater Quarry, across Union Street, which is used by Quarry Hill for storm water runoff and detention.

Guerra annually includes $125,000 in his budget for leachate to be treated at the town's treatment plant. He estimates $25,000-$30,000 could be knocked off that line if the gut is closed.

The quarry was excavated in the late 1800s or early 1900s, and when they did it they followed the softer rock and moved up when they encountered much harder rock. Guerra said the original excavators were able to go down to a depth of 270 feet in the north quarry, and then followed the rock up and across until they were able to expand into the south quarry.

Back in the day, the south quarry was 200 feet deep. The south quarry has not only been filled, but it has grown to a large mound.

Core sample drilling was done during the week of April 14, with the goal of locating the actual position of the connection between the north and south quarries, called the gut. That drilling took place just below and to the left of where the transfer station's large green recycling bins are located.

"We found the edge of the gut, with robust solid stone under and around the gut, and the gut was filled with waste material mostly," said Guerra. "Probably half of that material was earth, but the rest was tires, steel, glass, ceramic, paper, pennies and spoons."

It was basically general waste that the towns had been dumping there all long. Guerra said the cores they pulled up were 2-inches in diameter, with 4-inch casings being put down into the ground.

Locating the gut was the first step in Guerra's plan to erect an underground grout wall to block the flow of water between the quarries.

"The Consent Agreement that the towns and the Department of Environmental Protection signed in 1994 basically treated this as one whole quarry, and they said to fill it and then get out of it. Over the years, energy was focused on filling in the south quarry, and there was a possibility of obtaining more land over there so they filled the gut and then developed the rest of the land on the south side of the gut," said Guerra. "Once they filled the gut, the DEP said it was two quarries, and that we had to stay out of the north quarry and that we were done once we filled the south quarry."

Guerra said that problem with that, is that since the north quarry drains water into the south quarry, thereby creating a constant flow of leachate, MCSWC is "doomed" to pump and treat the leachate "forever."

"That's the big difference between an engineered land fill, designed to finally cut off water flowing through it, and working in a quarry that will always have ground water flowing through it," said Guerra.

He estimates that 25 percent of what they pump for leachate is attributed to flow through the gut.

"If we can put a group wall in there, it could that 25 percent," said Guerra.

The wall will also allow the north quarry water level to rise, and as long as the water continues to meet DEP requirements, it can spill as storm water. Guerra said the top 16-feet of that water is fairly clean, and by allowing it to fill to the top, the water will be even more dilute, or clean.

If that theory proves wrong, and the water in fact isn't clean to DEP standards, Guerra said it makes a stronger argument to drain the north quarry, fill it with waste and put an engineered cover over it.

"There had been a push 10 years ago to just go ahead and fill that north quarry, but with what we've learned working in the quarry environment, you can't just fill it," said Guerra. "The days of sending a municipal employee on a bulldozer out onto a floating mass of waste over 200 feet of water are over, fortunately. So we would have to drain that quarry to the bottom. Which in itself sounds a bit intriguing to me."

A plan to drain, fill and cap the north quarry would be expensive to develop, said Guerra.

"And if the grout wall solution works, we've spared that expense and we've cut off the leachate and that leachate is what gets pumped to the treatment facility, which costs a lot of money," said Guerra.

Last week, Guerra met with DEP representatives, who he said were pleased and even "excited" about his plan.

"I think this is what they want," said Guerra. "If this works, we don't have to argue over the issue anymore. But if it doesn't work, we have a much stronger argument to fill it."

But draining the north quarry before then working to fill it comes with its own concern for Guerra.

"The other argument about draining that sucker, is that there all sorts of stories about what's down there. The thing that scares me is what this place was like when I got here. It was a stinking heap of waste wood and Sheetrock and everything else and it was spewing off all sort of hydrogen sulfide," said Guerra. "I finally realized, what if it stinks when we drain it? That would be BAD. I'd get run out of town so that's a strike against draining it."

So Guerra is banking on the grout wall solution to work.

Now that the core sample drilling and investigations are complete, he said it will take a couple of weeks to design the wall and then some time to bid the word. But with only three companies in the state that can do the work, he anticipates the bid process to also go quickly.

His goal is to have the wall in place by the middle of June. After all, he's only budgeted about $90,000 for leachate treatment this year, so it has to work.

For those who bring waste and recyclables to the transfer station, he doesn't anticipate any more disruption during the work than they experienced during the drilling.

The work will commence in the same location as the drilling, and will involve wider cores to drill down, and then various techniques to use pressure to place the grout and force it into the ground. The drilling will likely create a row of three holes, with a second row of three offset from the first row.

A design challenge will be to deal with the porous nature of the contents of the gut, which could cause some settling of the grout. A lot of glass was found in the core samples, which could cause shifting of the grout.

"But that's engineering, they will work that out," said Guerra. "And as far as disruption, people survived the week of drilling, they honored our request not to come in so much and this time out, we know we won't have to move the recycling bins as far over as we did for the drilling work. I anticipate a minimal disruption during the wall work."

Related story:

• MCSWC Transfer Station asking customers to hold off making 'deliveries' April 14-18

Editorial Director Holly S. Edwards can be reached at hollyedwards@penbaypilot.com or 706-6655.