Earthquake Preparedness: Locating Underground Utilities

Locating Underground Utilities CUS

Keith Williams knows that if San Francisco were to have a repeat performance of the earthquake that rocked the city in 1906, the results would be catastrophic. Keith owns California Utility Surveys (CUS), which specializes in utility locating and has worked on several projects in San Francisco designed to allow for a speedy return to full operation after an earthquake.

These projects include the retrofit of Interstate 280, and the Golden Gate Bridge and Bay Bridge approaches. Keith stays abreast of the latest equipment and technology by attending industry trade shows. At one such show, he saw the RIDGID® SeekTech® SR-20 utility line locator from Ridge Tool Company. He soon purchased two and began using them in January 2006 for all of the company's jobs.


A Good Fit

The SR-20 locator uses a combination of multi-directional antennas, a revolutionary mapping display, and state-of-the-art processing to provide users with more information to effectively locate underground utilities. "I like that it is lighter and that it has a shorter-length design," says Keith. "Other locators are longer, which is ideal for taller people. I'm 5'8", and would always get a sore elbow on time-intensive projects. Since using the SR-20, I don't."

Marking Underground Utilities

New locators provide more information to the user so they can effectively locate underground utilities.

The locator's passive modes may also be used to search for other metallic lines. By using the combination of different locate readings, the user quickly and easily confirms a good signal and locate, or finds that there is distortion due to signal coupling in congested areas. If that's the case, the locator provides additional information to allow the user to effectively work through the distortion to provide a more accurate and more confident locate.

For one project, CUS helped a San Francisco transportation system establish a retrofit rail program. The city wanted to increase its rails' foundation size to prevent damage to the supports during a potential earthquake. CUS located underground utilities so another contractor could vacuum potholes to visually verify lines.

"I decided to use the SR-20 to relocate the utility lines to determine if the new location readings were in conflict with the old readings," says Keith. "Underground utility locating is not a black-and-white science. You not only need to understand advanced locating technology, but also to have a level of comfort with your locating skills. The SR-20 satisfies both."

While working on the San Francisco transportation project, CUS quickly found new lines that both the old locator and the transportation system designers did not know existed. Ultimately, Keith's decision to use the RIDGID locator to verify lines prevented unnecessary work. CUS was able to virtually eliminate its clients "dry holes," or potholes that contractors dig thinking they contain utility lines, but are actually vacant. This may be due to either poor locating or inadequate locating equipment.

Following completion of an overall pre-designation survey using the SR-20, CUS determined that more than 50 percent of the estimated holes were not required. This saved the San Francisco transportation system about $120,000 and its design consultants' time.

Better Accuracy

Keith attributes the locator's advanced features to the accurate location reading. The detailed information on the mapping display provides target line direction and changes in direction as they occur, left right guidance arrows, signal strength, and a proximity number that increases as distance to the target decreases. "Using those features gave us more confidence that the lines were actually there and that they were at the right depth," says Keith.

One of the locator's greatest values can't be summed up with a price tag. "We were searching for a particular utility, but we didn't find the line because it wasn't there. However, we did locate an 18-inch, steel-wrapped inactive fuel or gas main that no one knew about," says Keith. The location was next to a large commercial fueling site, commercial offices and a major highway. If this pipeline had been put into service and damaged during the excavation of the area, significant damage to both life and property would have resulted.

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