Piedmont Natural Gas says it’s cleaned up a spill near Radnor Lake that happened over the weekend, but still has work to do reaching out to nearby homeowners. The company spent the last year reassuring people of its plan to build a new pipeline south of Nashville, right through a highly protected park.
Drilling horizontally under Radnor meant pumping clay and water into the 20-inch tunnel, to lubricate and cool the drill and carry cuttings away. But apparently the tunnel went past a crack or hole underground, letting some 300 gallons of the mixture seep out into Otter Creek, where it flows into Radnor Lake.
Piedmont Spokesman David Trusty emphasizes the clay is nontoxic, and workers have already cleaned up the spill by hand, using buckets.
“It’s not a moot point by any means. No matter how small, no matter whether the substance is benign, it’s important to us, it’s serious.”
Drilling at the site is on hold pending a report to state environmental officials. The affected part of Otter Creek is only a few inches deep, shallow enough to ride a mountain-bike through – not that you’d be allowed to. The park (map, PDF) is so naturally protective hikers can’t even bring dogs in.
How did this happen?
David Jackson, a geology consultant at the site, explains during drilling bentonite clay is “pumped down the drill pipe, and under pressure it flows back toward the drilling rig, carrying the cuttings. So it’s how you get the cuttings out of the bottom of the hole.” What went wrong, Jackson says, is “it went down a small fracture or bedding plane or some natural feature in the soil or the rock material that allowed it to seep out of the bore hole.”
Jackson thinks the wet spring “probably helped it migrate further than it would have otherwise.”
Piedmont gave a brief report on the incident (PDF) to the Tennessee Department of Environment and Conservation today. The department may have followup questions, and it’s not clear how long its assessment will take. In a statement TDEC spokeswoman Meg Lockhart says “The drill rig that caused the release is not operating and will not until the department is satisfied that all steps are being taken to prevent a similar occurrence.”
While the removed clay is nontoxic, a TDEC official says “turbidity” in the water could affect some insects and crayfish, adding that none of them are endangered.