PEC COMPLETES MULTI-YEAR LARGE DIAMETER ASSESSMENT
By Michelle Coulter
PEC kicked off the New Year with completion of a multi-year Large Diameter Sewers Condition Assessment in the City of Phoenix (City). The project involved 15- to 54-inch diameter pipe segments in various stages of deterioration. Work consisted of inspecting and assessing 4,300 manholes and 223 miles of large diameter pipe of varying materials (e.g., vitrified clay pipe, cast iron pipe, ductile-iron pipe, fiberglass reinforced pipe, high-density polyethylene, and reinforced concrete pipe).
The PEC team incorporated the use of IBAK Panoramo® Optical Digital Scanning (ODS) technology to obtain a three-dimensional rendition of the pipe and manhole interior. The technology provides images using dual fish-eye lenses at the front and rear of the inspection units. Where flows within the pipe proved to be a challenge during inspection, the PEC team incorporated the use of conventional closed-circuit television (CCTV) equipment.
While these images produce high-resolution images of the interior of structures and pipe, a larger data storage space and computing power is required to store and view the data. PEC’s inspectors coded pipe and manhole defects using PipeLogix and GraniteXP softwares. The data received from these softwares were then input into InfoMaster where our team managed the assessment data, mapped the defects, rated the facilities, and generated rehabilitation projects and associated costs. Due to the large volume of inspection data received on a weekly basis, PEC needed to maintain management and quality control of the data received to eliminate any discrepancies and duplication of work.
All defects are evaluated with consideration of pipe size and location, i.e., pipe’s located under arterial streets, freeways, canals, etc. By following NASSCO’s PACP and MACP standards, PEC identified and coded the observed defects, and evaluated and recommended suitable rehabilitation methods for deficient pipe and manholes. When pipes were observed to be in critical condition (or with a grade 5 rating), PEC immediately notified the City of the scenario and prepared a “Grade 5 Memo” displaying location, defect identification, photos, and recommendations.
In the downtown area of Jefferson Street where a high-rise building is under construction, PEC observed multiple soil nails crossing through the pipe and in the flow. With the soil nail (and the broken pipe wall), our team assigned a grade 5 rating and suggested the pipe be repaired or replaced immediately. The City acted on our suggestion to avoid catastrophic failure of the pipe.
Upon completion of the assessment, PEC developed a 10-year, $214 million capital improvement program that prioritized numerous rehabilitation projects. The program includes the rehabilitation of 124 non-metallic pipe segments with a Level IV or V rehabilitation rating, 513 ductile-iron pipe segments, and 1,599 manholes. Of these segments, 10 to 15 pipe segments are considered emergencies. PEC is under contract with the City to complete rehabilitation design plans for several segments and manholes identified in our report. The project is projected to begin early this year.