R2008-147 AUTHORIZING AN AGREEMENT FOR WATER DISTRIBUTION SYSTEM LEAK DETECTION SURVEY

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� �� . i • Exhibit A SCOPE OF WORK Article 1 of the Agreement is amended and supplemented to include the following agreement of the Parties. ADS shall provide Basic and Additional Services as set forth below. Part 1—Basic Services ADS will conduct a leak detection/location survey with acoustic and sonic detection equipment on the City's water system using a one-man crew.We will survey approximately one-third of the total length of water main—estimated to be 176 miles—each year for three years. We investigate the system by listening directly on all hydrants and main line valves, selected b-box and service valves with highly sensitive sound intensifying instruments. When ADS encounters potential listening points that are not accessible,such as buried valves and covered meter boxes,a list of these will be provided to the Water Department and when conected they will be listened to provided the leak survey is still in progress. AD3 understands the value of completing a through leak detection survey and our sounding and listening points between hydrants, valves and curb stops will not exceed S00 feet. On the PVC mains correlation points will not exceed 300 feet between points. If suitable sounding points are not available at or less than these distances, a conelator may be used to complete the sounding and leak detection on these specific areas. Depending on the type of pipe material and the specific leak correlator used,we have successfully correlated leaks at distances greater than 500 feet. For a project of this size our general approach is to complete three to four days of sounding the system followed by one to two day of resounding and leak correlating at each potential leak location. After three to four full days of sounding the system and marking down the potential leak sounds, one to two days will be taken to return to those locations to see if the sound is still present. The sound may simply be due to usage and resounding will confirm whether or not it is a leak sound. If the sound is a leak sound, the location will be further investigated with the electronic correlator.This approach of three to four days sounding and one to two days resounding and correlating will provide a set of organized results for the weekly report that will be submitted to the City. When a leak is suspected and correlated with a positive result, the location of the leak indicated by the correlator will be further checked with electronic-ground sounding instruments to verify the position of the leak. It is encouraged that all leaks identified during the survey are repaired while the ADS engineers are still working in the City so that the immediate area can be sounded again in case another leak may have been masked by the original leak noise. In areas showing indications of leakage, ADS will thoroughly investigate the mains, hydrants, valves and/or services with an electronic leak correlator and ground microphone to pinpoint the leaks for repair. Leak locations will be marked with environmentally formulated engineering blue marking paint.ADS will also record all defective system components such as valves,hydrants and curb stops,as well as any map errors that are noted in the course of carrying out other field activities. The ADS leakage technicians will be able to conduct the large majority of the survey during normal working hours. In areas of high traf�ic volume, ADS will perform this work during"off-hours"and will provide the City with the necessary 24-hour notice. E�tibits ADS Environmental Services