October 27, 2016
Rockland County Interceptor Sewer Rehabilitation
A scheduled five-year CCTV inspection of a 750-lf, 36-in. reinforced concrete pipe (RCP) sewer interceptor revealed near total failure of the interceptor’s top half due to microbially induced corrosion (MIC). Even reinforcing rebar was entirely missing in stretches, leaving exposed soil held in place by very solid root masses. This interceptor is less than a mile upstream of the region’s wastewater treatment plant, so failure threatened to cause sewage backups and disrupt nearly all of Rockland County Sewer District No. 1.
Working with project contractors ACE Pipe Cleaning Inc. and National Water Main Cleaning Co. of New Jersey, the district devised a novel method of trenchless rehabilitation featuring the use of CentriPipe, a centrifugally cast concrete pipe (CCCP) solution, and the use of rolled and banded lengths of sheet steel that were inserted into the sewer, placed in the sewer’s worst sections, allowed to expand, and then anchored. The expanded and anchored sheet steel inserts provided a smooth and clean substrate for PL-8000, the cementitious grout applied by the CentriPipe SpinCaster. This use of rolled and banded sheet steel inserts to provide CCCP substrate was entirely successful and appears to be an entirely new method of trenchless rehabilitation.
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With a smooth pipe interior provided by the sheet steel inserts, the CentriPipe system was then used to cast a new, structurally sound, 1.5-in. concrete pipe that adhered tightly to the remnants of the original RCP sewer and the new sheet steel inserts. A total of three passes were used to cast this new pipe, and seamless manhole-to-manhole coverage was achieved.
ConShield, an anti-MIC concrete additive distributed by AP/M Permaform, was mixed onsite with PL-8000. Unlike coatings, ConShield provides integral anti-microbial protection throughout the concrete matrix for MIC prevention that does not fail as concrete wears.
Honeywell Stormwater Culvert Rehabilitation
Approximately 1,200 lf of stormwater culvert pipes, upward of 63 in. in equivalent diameter, required rehabilitation in Syracuse, N.Y. The culverts experienced severe deterioration, including offset and occluded joints and infiltration of potentially impacted groundwater that ultimately entered adjacent surface water bodies.
The decision to complete the rehabilitation using ultraviolet (UV)-cured Saertex multiCom fiberglass S+ liners to create a water-tight seal prevented further groundwater infiltration and provided a long-term structural and sustainable solution.The culverts are located within a 7,000-ft-long drainage ditch that runs adjacent to an inactive industrial use site and beneath an interstate highway and several local roadways and pedestrian bridges.
Closed circuit television (CCTV) inspection results showed sometimes severe structural deterioration along with groundwater infiltration that had a tendency to form hard scale buildup around pipe joints that impeded proper flow and caused the drainage ditch, connecting laterals and drainage areas to flood. The most cost-effective and sustainable solution was to line the culverts with cured-in-place pipe (CIPP) to prevent future groundwater infiltration and pipe deterioration.
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The culverts were lined with UV-cured Saertex multiCom fiberglass S+ liners. Unlike traditional steam-cured liners, the UV-cured liners have shown resistance to site groundwater and have had no effect on first flush styrene levels. In addition to advancing the technical design process, this project included the complexity of installing the largest equivalent diameter UV-cured liner in North America. Traditional steam-cured liners were impractical because of the large size and elliptical shape of the culverts. In order to achieve the required liner strength, traditional steam-cured liners would be prohibitively thick to compensate for the ovality of the elliptical host pipe, thus inhibiting proper curing. UV-cured S+ liners are more than 10 times stronger than the traditional liners allowing for thinner liners that can be efficiently and effectively cured.