Raleigh, North Carolina - City of Raleigh Public Utilities Department (CORPUD)

SERVICES: Manhole Inspections • Video Survey & Evaluation • Off-Road Sewer CCTV Inspections • Rehabilitation/Repair Recommendations • Capital Improvements Project Planning

WORK PERFORMED: 2010 – 2013


Ms. Eileen Navarrete, P.E., Construction Projects Administrator

(p) 919.996.3480 • (f) 919.996.1866 •

One Exchange Plaza, Raleigh, NC 27601

COST: $240,000


Hydrostructures completed an evaluation of the gravity sewers located adjacent to sewer siphons throughout the City’s sewer collection and transmission system. The intent of the project was to identify the extent of hydrogen sulfide gas damage in the concrete sewer mains and precast manholes upstream and downstream of the siphon locations. Turbulence at both the upstream and downstream siphon manholes create conditions for release of hydrogen sulfide gas, well known as a corrosive agent that relentlessly attacks concrete and steel reinforcing. The project was initiated after several failures occurred and is the first phase of an overall project which will include inspection of the connecting siphons using multi-sensor inspection technologies. Our crews video inspected approximately 29,600 LF of large diameter reinforced concrete sewer mains ranging in size from 30” – 72” and approx. 116 manholes and siphon structures. Additionally, the project identified approximately 19,500 LF of corrosion ranging from moderate to severe.


The sewers in this project were located in extremely wet, off-road, environmentally sensitive areas which required the use of specialized equipment including all-terrain CCTV inspection vehicles. Video inspection of the large diameter mains required use of our in-house fabricated pontoon float used as a camera skid. The pontoon floated the camera downstream while being carefully guided with a series of cables.


The final phase of the project included performing condition assessments on all sewer mains and manholes, developing detailed rehabilitation and repair recommendations to correct defects resulting from hydrogen sulfide gas damage, preparing cost estimates for all recommendations and prioritizing repairs based on the severity of the damage observed. Evaluation results were used to develop project descriptions for inclusion in the City’s Capital Improvement Plan.

Browse our site today to learn more about us, our field services, our engineering and construction services, our GIS and utility mapping services, and to view photo galleries and descriptions of some of our projects. Call us today at (919) 542-5002 or contact us to learn more about how we can serve all of your water, wastewater, and stormwater needs.

Hydrostructures delivers comprehensive wastewater,  stormwater, and water system collection, conveyance, and management design and consulting services to clients throughout the Southeast and Mid-Atlantic, with offices in Pittsboro, North Carolina; Winston Salem, North Carolina; Cayce, South Carolina; and Virginia Beach, Virginia.