Mid-Centre County Wastewater Treatment Plant – Structural Monitoring and Nondestructive Evaluation

Project Description

As part of Herbert, Rowland & Grubic, Inc.’s evaluation of cracking observed at the Mid-Centre County Wastewater Treatment Plant (WWTP), BDI was requested to help the evaluation process by monitoring key areas of the facility during operational and seasonal periods to aid in identifying the root cause of the deterioration found on site.

BDI installed ten strain gages and five displacement gages at the facility, each equipped with their own thermistors to allow for temperature correlation. After six months of monitoring, BDI was able to assist HRG with documenting that the performance issues were due to an inability of portions of the structure to freely expand and contract, which was causing deterioration in the beam ends of the roof components – conclusions all drawn directly from correlation of the displacements, strains, and observed temperatures inside and outside the facility.

HRG then designed a retrofit to provide some relief to the components and re-engaged BDI to perform NDT-E to mark out where rebar was located at the edge of beams and along side of sidewalk panels. This NDT-E effort, utilizing GPR, was able to allow the contractor to more accurately make cuts in these concrete components without hitting the structural rebar. Once the retrofit was completed, BDI performed three months of post-retrofit monitoring to verify that the detail relieved the stresses as expected.