On June 15, 2017, Sunoco/ETP started drilling into the hillside at the Shoen Road drill site, just off of Rte 100, about half a mile north of Exton, PA. They were drilling northeast, into Uwchlan Township. The drilling was for a pilot hole that was later to be enlarged to accommodate the Mariner East 2 pipeline (the Dragonpipe). Within about a week, they had a serious problem on their hands.

The area just north of Exton is one that the Pennsylvania Department of Environmental Protection (DEP) had been concerned about. The DEP had queried Sunoco about it during their process of applying for permits.

The DEP expresses concern. The DEP wrote, concerning the deficiencies in the Sunoco application: “Karst area near Exton and the East Whiteland compressor branch present additional risks of IRs [inadvertent returns—drilling fluid surfacing unexpectedly] during HDD [horizontal directional drilling]. Provide a detailed assessment of measures to reduce the risk of drilling in these areas. There are two areas are the most concerning, especially Exton. There are carbonate rocks, karst surface depressions; and identification of other public water supplies (groundwater or surface water) within one mile.“

In their response to the DEP, Sunoco/ETP identified one well owned by Aqua (the local water utility) and said it would install a monitoring well and consider changes to its drilling path to avoid problems there. But it did not mention private wells.

A note about “karst”. Karst is a geologist’s term for an area where the bedrock is limestone that has been eroded in various ways by water flowing through it over the millennia. It is often associated with sinkholes and caves, and drilling wells in karst can be problematic, as I remember from growing up in a karst area of southern Indiana. You never know how deep the water table will be, and the results can be completely different even drilling wells that are on neighboring plots of land.

Using the horizontal directional drilling technique in karst, which is what Sunoco/ETP is doing, is risky because of the gaps and channels in the limestone. And, as the DEP feared, problems soon occurred.

The problems begin. It seems that, in the course of drilling sometime around June 23, Sunoco/ETP hit an aquifer that supplies local wells.

This had at several unfortunate results. The first of these (as a nearby resident reported on Facebook) was the backflow of a large volume of water which came out of the borehole at the drilling site. Sunoco had to bring in tank trucks to take it away, in addition to setting up a pump, hose, and retention pool near the site. This suggests that, in drilling into the hillside, the drill hit a pool of water, some of which was higher than the borehole entrance, so gravity sent the water out the borehole. The pumping continued, 24 hours a day, until July 5 according to local residents.

Foul water, or none at all. The local residents who depend on well water bore the brunt of it. Some wells went dry, probably because their water came from an area higher than the drill site, and all their water was drained away. Others found that their water had been fouled—presumably by drilling fluid.

In response, Sunoco suspending drilling and began providing bottled water and putting families up in local hotels—while also asking them not to talk about the situation. (Sunoco/ETP is required to notify local authorities and the DEP immediately in situations like this; but if they did, the public did not get the word for about two weeks after the drill hit the aquifer.) But the word got out, and by July 7, it was getting covered in the news media.

Drilling suspended, restarted, suspended again. As of July 8, a local resident reported that Sunoco/ETP had been putting grout down the drill hole (presumably in hopes of sealing the drill path off from the aquifer) and would try drilling through that once it hardens.

On July 8, State Sen. Andrew Dinniman (D-19th Dist.) called for a halt in drilling. He told the Local Daily News, “I have asked Sunoco directly to cease drilling in Chester County until a comprehensive assessment of the damage to this aquifer can occur, a plan is put in place to restore safe water service to the affected residents, and steps are taken to ensure that a situation like this does not occur again.” Dinniman’s district includes the drill site, but not most of the affected homes. Sunoco, however, resumed drilling.

Then, at a community meeting on July 13 at the West Whiteland municipal building, a Sunoco spokesperson said that Sunoco had suspended drilling again, pending resolution of the water issues. Sunoco will offer to pay for affected residents with wells to be connected to the public water supply if they wish, and will give them a lump-sum payment to cover their estimated water bills for 20 years.

Is the water OK? Well water from 31 residences has been sent for testing. Of the 21 samples with results as of July 13, Sunoco says that none shows dangerous substances. Sunoco also says that the test results suggest that the aquifer has not been contaminated by drilling fluid; rather, the disturbance and draining of the aquifer has caused agitation of the material already settled in the wells, resulting in “turbidity” (cloudiness) seen in the water samples. Test results will be shared with each well owner, but not with the public.

There was no discussion of the larger questions of how extensive the aquifer is, where its water flows, and whether wells farther away from the drilling will eventually be affected.


Updated July 8, July 9, and July 14 with additional detail.