Marsh Creek | Energy Transfer

Mariner East

– – – – –

In April 2021, a member of the public reported a discovery of gray sediment on the shore of Marsh Creek Lake to the PA Department of Environmental Protection (DEP) and Pennsylvania Fish and Boat Commission, alleging it was bentonite (drilling mud) from previous Mariner East construction activity. Energy Transfer immediately conducted a preliminary inspection, and a third-party professional geologist (PG) conducted his own site inspection. The PG collected three sediment samples and submitted them to be analyzed for bentonite/montmorillonite, one of the identifying constituents of drilling mud. Upon analysis, bentonite/montmorillonite was not detected in any of the samples. The findings confirmed that the sediment observed at the site is not drilling fluid. Additionally, a review of historical aerial photographs identified a band of light gray-to-gray sediment along the same shoreline dating back to at least 2001. Thus, the sediment appears to be a historical deposit predating pipeline construction activities.

The DEP conducted its own field tests and sampling and posted the following update on its website: “DEP has received the results of all laboratory analyses. The chemical analysis did not discover any chemical constituents that indicated the material was anything other than naturally occurring substances consisting of plant and decay products. The XRD analysis identified the samples as being primarily composed of quartz with traces of other native minerals. No bentonite was found in any of the samples. Those results are posted below. The sample analyses indicate that this substance is a naturally occurring material. No cleanup of the material is necessary. This investigation is now closed.”  For more information and to view DEP’s lab results, visit

– – – – –

On Aug. 10, 2020, an inadvertent return (IR) of water and bentonite clay occurred near a Mariner East pipeline drill site in Upper Uwchlan Township, Chester County, ultimately impacting Marsh Creek Lake. Our crews responded immediately to contain and remove the nontoxic mixture of bentonite clay and water— sometimes referred to as drilling mud.

We recognize the importance of this waterbody and remain committed to fully remediating and restoring the impacted area. We are working closely with the PA Department of Environmental Protection (DEP) and the Department of Conservation and Natural Resources to complete this process. There is no hazard to the public and no impact on recreation activities.  

An “inadvertent return” is when drilling mud rises to the surface through preexisting cracks in the rock and soil during horizontal directional drill (HDD). These discharges are not unexpected during the course of HDD activity, and are covered in our permit applications approved by the DEP.

Photos from March 2021 of the tributary that has been cleared and restored.

Photo 6684803 DJI 131 jpg 9454029 0 2021327105724 photo original - Marsh Creek
Photo 6684799 DJI 127 jpg 10101958 0 2021327105624 photo original - Marsh Creek
Photo 6684796 DJI 124 jpg 9566760 0 2021327105512 photo original 1 - Marsh Creek

Questions or concerns?

24/7 Community Hotline:

Chester County Tele-Town Hall Recording – Thursday, August 20, 2020

Q: Did the drilling mud impact local drinking water?

A: No, the Pennsylvania Department of Environmental Protection (DEP) has confirmed that no public drinking water has been impacted as a result of this IR. Our environmental engineers and geologists do not believe any private wells have been impacted. In accordance with our approved plans and protocol, when an IR occurs, we provide notification to residents in the area who have private water supplies, as well as public suppliers.


Q: Is bentonite clay (“drilling mud”) hazardous to humans or wildlife?
A: No, this mixture consists predominantly of water that must adhere to safe drinking standards and naturally occurring nontoxic clay called bentonite. The drilling mud is used during the horizontal directional drilling (HDD) process to keep drilling tools cool, remove drilled material, support the drilling hole and lubricate the drill bit and pipe during the final stages of pulling the pipe.

Drilling mud is commonly used during HDD operations and is not harmful. In most cases, the drilling fluid composition ranges between 2% and 15% bentonite clay and between 85% and 98% potable water, depending on the specifics of the particular drill. Often during open excavation of fragipan wetlands, bentonite clay is added above the pipeline trench to provide a confining layer for water within the wetland. This process is approved by state and federal agencies as a way to protect the wetland hydrology.

The same bentonite used in the HDD process can be found in everyday household products, such as hand soaps and lotions, and is used in the clarifying process in winemaking and home brewing. Bentonite is also listed by the U.S. Food and Drug Administration as a “Generally Recognized Safe Food Substance” when used as a processing aid, and it serves a number of other practical uses, including medicinal purposes.

Despite the nontoxic nature of drilling mud, we are closely analyzing any potential impact to wildlife as we complete our cleanup activities. Energy Transfer is committed to wildlife conservation and the long-term integrity of the environment.

Learn more:
DEP Information About HDD and Bentonite
Energy Transfer’s Commitment to Environment and Wildlife

Q: Is the drilling mud cleaned up?

A: As of Sept. 11, third-party assessment of the lake continues. Crews previously finished cleaning up the drilling mud in the creek. The creek and lake remain open and safe for recreational purposes.

Q: How will Sunoco/Energy Transfer prevent this from happening again?

A: While IRs are not uncommon in the horizontal directional drilling (HDD) process, we take all precautions to avoid them and to minimize the impacts when they do. It is for this reason that thorough response plans are required in all HDD environmental permits with the Pennsylvania Department of Environmental Protection (DEP). We comply with an Inadvertent Return Contingency Plan by responding to and containing the IR to avoid any adverse impacts and by reporting them to the DEP.

Should another IR occur, we will stand ready to enact our HDD response plan immediately to contain, remove the drilling mud and completely restore the environment.

At all of our construction sites, we have environmental inspectors who are responsible for holding our construction methods and erosion-control devices to our specific permit requirements. The comprehensive environmental permitting process includes local, state and federal agencies, along with full public participation.

Tele-Town Hall Q&A Updates

Below are some additional questions we received from multiple callers during the Aug. 20, 2020 tele-town hall, which we did not have time to address during the call:

Q:  What happens if there is a leak once the actual products are flowing through the pipeline?

A:  Leaks from pipelines are rare, but if one does occur, pipeline operators and emergency responders are prepared to execute proper hazardous materials emergency procedures. When a pipeline release is detected, the response chain is initiated by a call to 9-1-1 to notify first responders. The pipeline operator immediately activates its response plans and shuts nearby valves along the pipeline to stop the flow of product. First responders secure the area to maintain public safety. Decisions regarding public evacuations or shelter-in-place are only ordered by government agencies. Pipeline operators assess the situation and take any and all actions needed at the site to safely stop the leak and secure the equipment. 

Additionally, government authorities, and cleanup resources all spring into action upon notification of an emergency. For more information on pipeline emergency response, visit

Keeping America’s pipelines running safely and efficiently is the number one priority for all pipeline operators. Please refer to our Mariner East FAQ page, under the “safety” section, for more information on our approved facility response plans, first responder trainings, and ongoing public awareness efforts.

We would also note that we currently have pipelines in service in this area, which have been safely operating for years. Our 12-inch NGL pipeline has been safely operating for nearly two years, and our 8-inch pipeline has been in NGL service for nearly six years, after moving refined products for more than eight decades.

Q:  What is the pH of drilling mud?     

A:  The freshwater drilling mud we use, containing bentonite, has a pH ranging from 7 to 9.5. A pH value indicates how acidic or basic water is. A pH of 7 is considered neutral and is typical of stream water. A pH of 8 is common of sea water, pH of 9 a poultry egg, and a pH of 10 an indigestion tablet, for example.

Q:  How large are these pipes in diameter?

A:  The pipelines currently being installed are 20 inches and 16 inches in diameter. Nearby, there is a 12-inch and an 8-inch diameter pipeline safely operating.

Q:  When will construction be complete and what will the cleanup and remediation afterwards look like?

A:  The timing is dependent upon receiving a few final approvals. At this time, if we are able to move forward as planned, we anticipate finishing the project in early to mid-2021.

Following construction, we are committed to working closely with landowners to restore the right-of-way to its original state or better. Crews typically begin preliminary restoration within a week after construction is complete, weather permitting. As part of restoration, fences are replaced, vegetation is reseeded and any property impacted during construction is repaired. Restoration plans and procedures are approved by the DEP in our permits. Techniques such as HDD and road boring allow us to minimize impacts to the environment. Inspectors are on-site to ensure appropriate steps are taken to meet all of the strict conditions of our DEP permits.

Q:  How often is fluid backup maintained? Are you actively monitoring leakage into the creek?

A:  Drilling fluid does not continually “backup.” If drilling fluid does surface at a drill site, we quickly contain and clean it up in compliance with the Inadvertent Return Contingency Plan (further explained in other Q&A on this page).  There has been no further “backup” of fluid at Marsh Creek. We have set up containment at the creek, which is being actively monitored. In addition, sometimes groundwater is encountered during drilling, which is monitored and managed either through a controlled release to the ground surface or storage in temporary tanks, in accordance with our approved DEP permits.  


* indicates required