In the summer of 2020, Metro Public Works was made aware of an increasingly problematic sinkhole near 601 Hickory Hollow Terrace. MPW contacted the Collier paving program manager to investigate and report. Since this project involved primarily stormwater infrastructure, MWS took over the project and financing shortly thereafter. The project area was surveyed by Collier personnel. This initial investigation included televising the adjacent storm system to determine the extent of the damage below the surface of the road. Subsurface exploration was also brokered by Collier and carried out using direct push technology (DPT) to probe the subsurface for areas of soft overburden and to acquire measurements to the bedrock surface. With this field data, Collier personnel were able to analyze and prescribe a feasible solution that was presented to MWS for approval. After presentation and review by MWS staff, Collier was granted permission to move forward with the solution.

Collier design staff then used the surveyed data to produce a design to address the sinkhole and the deficient injection well with one excavation. Due to the fact this was an injection well, Collier reached out to TDEC to advise that they had an undocumented injection well location. TDEC then advised MWS and Collier to move forward with permitting to document this location which Collier did expeditiously to accommodate the accelerated schedule of the project. The design was a hybrid between a conventional storm sewer replacement and an inverted rock plug. The inverted rock plug was used to bridge the sinkhole at the soil and bedrock interface and provide structural stability to the various matter above it. The deteriorated corrugated metal pipe (CMP) was removed and replaced with reinforced concrete pipe (RCP) and new precast structures were installed at both the inlet and outfall of the new pipe. Upon backfill of the excavation to final grade, the affected portions of the sidewalk and asphalt roadway were replaced and tied into existing facilities. With the appropriate traffic control measures in place, the roadway was kept open during all construction activities to provide access to the constituents in the vicinity. Also, all utilities present in the disturbed area remained in kind during construction and remained active to service constituents in the area.

Client: Metro Nashville Water Services