City adds scanning system to combat rain-dependent infiltration

Problem: Oregon receives 2.8 inches more rainfall than the national average. As a result, rain-dependent infiltration (RDI) is an issue for cities such as Coos Bay, which receives between 60 and 80 inches of rain per year. RDI can be difficult to locate using visual methods, since in dry weather a defect may not be actively leaking, so it may not be seen. Meanwhile, in wet weather, there may be too much water in the pipe to locate the defects visually. Coos Bay has an area zoned for industrial, commercial, single-family and multifamily development, which will add a large volume of sewage to the system. The city has analyzed the existing sanitary sewer system that serves this area and has determined that it is over capacity.  

Solution: The city turned to Electro Scan technology for a way to locate and quantify its RDI. By locating and eliminating the RDI, the city hoped to be able to make room in the system for additional sewage.

Result: Electro Scan testing was completed on four pipes. Sources of infiltration were identified, and results showed that the PVC pipe was in ideal shape and no defects were detected. However, the three concrete pipes were in varying conditions of disrepair; a total of 112 defects were located, representing an overall potential leakage rate of approximately 44 gpm, or 63,461 gpd. The data resulted in the city council’s decision to purchase an ES-620 for Sewer Mains system, which was installed in December 2015. 800/975-6149; www.electroscan.com.

Related: InfoSense Wins North Carolina Technology Award

Acoustic inspection reduces precleaning in CCTV inspection program

Problem: Hillsborough County, Florida, serves a population of over 500,000 in the area surrounding Tampa. They have set an internal goal of CCTV inspection of approximately 1,700 miles of gravity sewer over the next five years. Management wanted to maximize the efficiency of the process and target its precleaning efforts on the pipes that needed it.

Solution: The Sewer Line Rapid Assessment Tool (SL-RAT) from InfoSense was developed for rapidly identifying sewer line blockage conditions. It is based on measuring an acoustic signal transmitted between manholes in an active sewer line segment. Commonly encountered sanitary sewer defects, such as roots, grease and breakages, naturally obstruct acoustic energy; this changes the pipeline’s acoustic properties and produces a measurable impact on the acoustic profile. An algorithm is used to exploit these variations and provide a real-time evaluation of the segment’s blockage condition. A two-person crew can typically screen 2 to 3 miles of sewer per day. The units are GPS-enabled. Downloaded data can be visualized in Google Earth or integrated with a GIS system using SHP file exports.

Result: Hillsborough County purchased two SL-RAT units in mid-2015. In the first eight months of operation, the technology had screened over 170 miles of the system and reduced unnecessary precleaning activity by over 80 percent, saving the county over $500,000 so far. 877/747-3245; www.infosenseinc.com.

Related: Technology Test Drive: Down the Tube

Software helps city manage sanitary collections system

Problem: Chula Vista, California, maintains a digital asset management program to help provide the foundation for sustainable best practices. Collections system manager Dave McRoberts collects infrastructure data, running two CCTV inspection trucks with two tractors each, and a shared large storm drain tractor. He works closely with Public Works specialist Yuen Cheng and engineering technician Tim Weinman to share comprehensive, current information between departments. Together, they manage and maintain a sanitary collections system serving 265,000 customers with 515 miles of sanitary line — 98 percent gravity feed and 2 percent force main — 14 pump stations and 10,800 manholes. The city needed a software program capable of organizing collected data into an easy-to-use form.

Solution: The city has been using PipeLogix pipeline assessment software since 1998 to work with its CCTV inspection cameras. Cheng collects CCTV survey data for the GIS department and imports it into an ESRI ArcGIS mapping program. “Citywide, users can click on any given pipe and bring up its video survey footage,” she explains. She uses PipeLogix to help plan upcoming inspections, and pulls data into the city’s core software, Lucity, which handles asset inventory, maintenance management and GIS compatibility. McRoberts uses PipeLogix’s PACP-rated asset data to determine which lines get rehabilitated or replaced, and in planning new development.

Result: Having all of the data in a digital format allows it to be available to all departments, on demand, eliminating any waiting for hard copy data, or having to manually match up printed reports with video. By all measures, the software-aided asset management campaign is a success. 866/299-3150; www.pipelogix.com.

Related: Cover Story: SEWER: Open to Suggestion

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