WQ0000185_Complaint Investigation_20230925

North Carolina Department of Environmental Quality Division of Water Resources
Raleigh Regional Office 3800 Barrett Drive Raleigh, North Carolina 27609
919.791.4200

September 25, 2023 Ms. Pamela Rich 135 Faribault Lane Hillsborough, NC 27278 Sent Via Email Subject: Subsidence Around Former Well BIMS Incident #202301369 Ms. Rich: On September 21, 2023, Michael Hall and Kevin Fowler from the Division of Water Resources (DWR), Raleigh Regional Office (RRO) followed up on a complaint you made regarding subsidence around a former well. Based on a phone discussions between you and Mr. Hall both before and after the inspection, the DWR understands the following:
• There was a former well, presumably hand dug on your property (see attached site plan). • This well was previously capped with a concrete pad (visible on historical aerial photographs) that collapsed (see attached photographs).
• Following this collapse, you had well backfilled with crush and run, and covered with topsoil. Based on measurements at the time, the hole was approximately 17 feet deep.
• The area began to subside, culminating in your call to the DWR. During the site inspection, DWR personnel observed a depression in front of a wooden storage shed (see attached photographs). The depression was roughly circular, and covered with grass. Beneath the grass was a sheet of plywood, and then crush and run. These observations were consistent with the understanding based on the discussions with you. Following inspection of the former well, the DWR personnel examined the wooded areas North to the Eno River, and East to an unnamed tributary running North to the Eno River. To the Northwest of your property (see attached site plan), DWR personnel observed a steep bedrock cliff approximately 15 feet high, with groundwater discharging into the unnamed tributary from a hole in the bedrock or possible stone lined drain (see attached photographs) on the Southeast side of the cliff. There was an accumulation of fine sediment downstream from this discharge, suggesting that it may be coming from fractures in the rock. Based on these observations, it appears that the subsidence at the well is likely the result of surface runoff percolating through the topsoil placed over the well, and gradually eroding it and carrying it through the well, into the fractures in the underlying bedrock, and ultimately into the unnamed tributary to the Eno River. This being the case, there appears to be limited risk for catastrophic collapse around the former well; however, the concentrated flow of water through the well has likely flushed the fractures in the underlying bedrock, thereby accelerating the transport of sediment through this conduit. As a result, slow subsidence of the surrounding area may continue.
Well Abandonment North Carolina regulations require the abandonment of wells in accordance with 15A NCAC 02C .0113 (2C Rules). This has not occurred. Instead, it appears that the well was initially covered with a concrete cap, with limited, if any fill beneath this cap. According to the current property owner, the cap collapsed, and the hole was backfilled with crush and run (see attached photographic log). As a result, the well is a continuing conduit for surface water infiltration, and sink for sediment transport.
DocuSign Envelope ID: 60AA94B2-24B1-4F28-87EB-22E5CA07A78C
North Carolina Department of Environmental Quality Division of Water Resources
Raleigh Regional Office 3800 Barrett Drive Raleigh, North Carolina 27609
919.791.4200
Abandonment following 2C Rules is complicated because of backfilling with crush and run. The Division of Water Resources recommends a modified approach that will seal the well, and prevent continued surface water infiltration. Disinfection of the well prior to abandonment does appear feasible without complete removal of the crush and run, and is therefore not required. An acceptable approach could consist of the following: 1. Excavation to a depth of at least 3 feet, consistent with 15A NCAC 02C .0113(c)(4). 2. Placement of a neat cement grout, bentonite grout, or flowable fill that will percolate the crush and run in the former well/sinkhole, in addition to surrounding fractures, thereby creating a seal and limiting future infiltration of surface water consistent with 15A NCAC 02C .0113(c)(5). This grout should be brought to the top of the crush and run, and topped off as necessary during curing to keep it at this level. 3. Once the grout has set, backfill the excavation with soil. Other methods to prevent the infiltration of surface water, and limit future subsidence may also be used, and we recommend that you engage a qualified engineering or drilling firm to assist with planning and implementation of this abandonment, and request the opportunity to review the proposed approach prior to implementation. We also request the opportunity to observe implementation. We appreciate that you contacted us, and requested input regarding this issue. If you have any additional questions, please contact Michael Hall at [phone] or via email at [e-mail]. Sincerely,
Vanessa E. Manuel, Assistant Regional Supervisor
Water Quality Regional Operations Section
Raleigh Regional Office
Division of Water Resources, NCDEQ Enclosure Site Plan Photographs cc: Laserfiche
DocuSign Envelope ID: 60AA94B2-24B1-4F28-87EB-22E5CA07A78C
DocuSign Envelope ID: 60AA94B2-24B1-4F28-87EB-22E5CA07A78C
Photograph 1
Historical view of concrete collapsed into former well.

Photograph 2
Historical view to South of filled well.

C‐23‐091 (BIMS #202301369)
135Faribault Lane/Orange County
DocuSign Envelope ID: 60AA94B2-24B1-4F28-87EB-22E5CA07A78C
Photograph 3
View Northeast of subsidence around former well.

Photograph 4
View of crush and run in center of subsided area.

C‐23‐091 (BIMS #202301369)
135Faribault Lane/Orange County
DocuSign Envelope ID: 60AA94B2-24B1-4F28-87EB-22E5CA07A78C
Photograph 5
View Southwest along cliff, toward groundwater discharge.

Photograph 6
View Northwest of groundwater discharge from fracture or former
drain. Note fine sediment seƩled in the stream.

C‐23‐091 (BIMS #202301369)
135Faribault Lane/Orange County
DocuSign Envelope ID: 60AA94B2-24B1-4F28-87EB-22E5CA07A78C