Well-Managed Assets

Texas utility’s award-winning collections system is backed by a ‘digital warehouse of data.’
Well-Managed Assets
Dario Garibay uses an inspection camera to photograph a placard held by David Brown. The placard identifies where in the nearly 500 miles of sewer line the photos were taken.

Interested in Infrastructure?

Get Infrastructure articles, news and videos right in your inbox! Sign up now.

Infrastructure + Get Alerts

The sewer system serving the City of Denton, Texas, has been growing with the city and has experienced plenty of growing pains.

But over the last few years, Denton’s sewer utility has been getting a handle on some of those growing pains.

Sophisticated software and attentive deployment of manpower get the credit. So does a culture that values and encourages employee participation. And Texas has taken notice. In April 2014, the Water Environment Association of Texas gave Denton its annual Sidney L. Allison Award recognizing the utility’s asset management program for how it’s improved productivity and service for the Denton Wastewater Collection System and its customers.

The operation has come a long way. Denton’s total population is just 124,000, but the area served by the city’s sewer utility “is pretty substantial” beyond the city limits, says P. S. Arora, assistant wastewater director for Denton, a suburb of Dallas-Fort Worth. Altogether, it takes in wastewater from a territory of 158 square miles.

The city also has wholesale agreements to provide sewer service to smaller cities around Denton.

“The sewer system is pretty spread out,” Arora says, with lift stations scattered throughout the network. The large footprint makes keeping up on malfunctions something of a challenge. “Our dollars are limited and our manpower is limited.”

So Denton has turned to asset management, trying to systematically understand the needs, conditions and urgency for repairs to all parts of the sewer network.

Starting out

The city already had what would become the backbone of its asset management system. In the mid-1990s, Denton acquired an Esri GIS mapping system and mapped the entire sewer and water systems.

In the late 1990s, the city installed a computerized maintenance management system from Azteca Systems, which has since been upgraded to the company’s current Cityworks system.

“All of the work done by our crews, whether it is CCTV work, smoke testing, line flushing, point repair, fixing a line, root cutting, applying chemicals – it doesn’t matter what they do, everything goes through the computerized maintenance management system,” Arora says.

This CMMS work-order system has helped build a database of the system as time goes on, he explains. “We have lots of data now for the maintenance side of the collection system.”

Denton also uses InfoWorks (Innovyze) for sewer system capacity evaluation and master planning of the system.

All this technology has brought Denton “a very nice maintenance- and capacity-management system,” Arora says. “But we didn’t have a full asset-management program.”

A crisis situation helped change that.

Growth and challenge

Denton’s growth required the city to begin replacing existing sewer pipe with larger-diameter lines. In 1998, officials began developing a master plan to identify pipe requirements for adequate capacity in response to increased demand.

But about eight years ago, a developer walked away from a major project that had led Denton to budget for a new wastewater treatment plant and install 6 miles of new, larger sewer line to the new facility. The bonds for the plant had been sold, but the new customer base that was anticipated with the development was suddenly pulled out from under the city.

“We got in a fiscal straitjacket,” says Arora, who eventually came across the Sewer Cataloging, Retrieval and Prioritization System – SCRAPS for short. Produced by the Water Environment Research Foundation, SCRAPS enables wastewater utilities “to focus their inspection program in areas most likely to need attention.”

The city retained the engineering consulting firm Burns & McDonnell, which had been involved in developing SCRAPS, to implement the model in 2008.

Setting priorities

The task began with putting in more than 80 data points for every sewer line in the system. “The best part of going through that process is you learn what you don’t know about your system,” says Arora.

Each line was then graded on a scale from 1 to 100 for the priority of correcting problems that could lead to failure: The higher the number, the higher the priority. After completing those ratings in 2009, Denton followed up by using the information to organize its sewer line cleaning program into one-, five- and 10-year cleaning cycles.

For example, recently installed PVC lines in a new subdivision would not be expected to fail anytime soon; those sort of lines were put on a 10-year cleaning and inspection program. Smaller lines in older parts of the community might be put on a five-year schedule. Lines deemed to be at the greatest risk, as well as lines serving high-volume sources like restaurants or apartment complexes, are scheduled to be checked annually.

In ranking the lines by priority, Denton didn’t just rely on its consultant’s recommendations though. Instead, Arora and his management team ran the recommendations by the most experienced employees in the sewer department.

“We made sure the results coming out of the program were matching up with the judgment of the guys who have been here 20, 25, 30 years,” Arora says. “This allowed great buy-in. The best part was the involvement of the operations guys, who also came up with the need for the one-year cleaning cycle.”

Since those initial priorities were set, experience has led to adjustments. Some lines originally considered at high risk for failing have proved to be more durable, for instance, so they’ve been moved to a less frequent cleaning and inspection cycle.

Ongoing inspection

Denton also changed its approach to CCTV inspection, again based on the priority rankings. The city bought an Envirosight Rovver 125 camera and tractor in 2007. At the time, though, its use of CCTV was “mainly in reaction to problems,” says David Brown, an engineering technician who now heads up a two-man daily inspection crew. Starting in 2011, Brown and an associate began a program of conducting routine inspections every day. By 2013, Brown’s team was inspecting 200,000 feet of wastewater line per year – about 1,000 feet per day.

Some of those inspections were ordered for immediate concerns, mostly roots choking off lines, but increasingly they’re being built into a routine process based on the priority ratings. Even if called out to an urgent problem, Brown makes it a point to check if there are lines in the vicinity that are high on the priority list for inspection and to include them in the day’s work if possible.

Along the way, if they encounter problems that need a quick fix – flushing out a clogged pipe or removing roots, for example – they can arrange for immediate follow-up by one of Denton’s flushing trucks. The program’s high productivity has enabled Arora to persuade city officials to expand personnel and equipment, such as recently acquiring the city’s fifth flushing truck in its fleet.

The inspection program also allows Brown and his associate technician to make more mundane improvements, such as correcting the GIS database when the address for a line location is listed incorrectly or the composition of a line is erroneous – clay instead of PVC, for instance.

“We’re basically doing several things at one time,” says Brown. “We’re inspecting the line, looking for problems, inspecting the GIS mapping system – and doing manhole inspections.”

Even if a problem can’t be fixed immediately, it can be marked. “Then when the field crew comes out, they can fix it without having to look for it,” he says.

Camera versatility

Denton relies heavily on the Envirosight RC90 pan/tilt/zoom camera for routine inspections. To minimize downtime, the city acquired a second RC90 so they can keep working if one is damaged.

When both are in use, one is set up for 6-inch pipe and the other for 8-inch or larger pipe. That saves time by eliminating the need to make adjustments for different line sizes, Brown points out.

More recently, Denton began using Envirosight’s Jetscan unit, which combines jetting and inspection in a single tool.  “Basically, the camera work has gone from being reactive to being proactive,” Brown says.

Denton’s latest step was implementing CapPlan software, now upgraded to InfoMaster Sewer, from Innovyze. It was chosen, Arora says, because it’s “a complete infrastructure support and asset management and planning tool for sewer systems.”

Continued refinement

The CapPlan database integrates the GIS maps with data from Cityworks and the priority rankings from SCRAPS. It employs CCTV video from inspections as well. The CCTV database is matched to the scoring system employed under the Pipeline Assessment Certification Program established by the National Association of Sewer Service Companies.

The priority scores generated for each segment of the system are entered into InfoMaster, and the software identifies repair projects, evaluates their necessity, runs calculations for full replacement costs of the defective asset compared with the rehab cost and even recommends a particular method for rehab.

“When we run it, we can create a beautiful map from the InfoWorks model results,” Arora says. “It will give us a priority ranking for all the CCTV work to be done.”

Denton’s asset management program has grown so robust it even includes trees. At the University of North Texas, located in the city, researchers have mapped Denton’s tree canopy using satellite imagery. Where the canopy is especially dense, corresponding sewer lines are targeted for a closer look for possible root damage.

That type of creative, out-of-the-box thinking is made possible by the immense depth of information already at the city’s disposal. “What you have is a digital warehouse of data for the entire system,” Arora says. “You find a lot of different ways to make things better.”

All these investments in technology, equipment and people have paid off. Arora says Denton has cut wet-weather overflow volume by 99.5 percent, and instances of choked sewer mains – whether from roots, clogs or other problems – have fallen by as much as 94 percent, he says.

“We have come a long way from where we were in 2000,” he says.

Arora has already calculated the likely savings the city will experience from shifting to prioritized asset management and away from standard 50-year depreciation: some $20 million over 10 years.

And Denton has no plans to stop now.

More Information

Cityworks - 801/523-2751 - www.cityworks.com

Envirosight - 866/936-8476 - www.envirosight.com

Esri - 800/447-9778 - www.esri.com

Innovyze - 626/568-6868 - www.innovyze.com


Comments on this site are submitted by users and are not endorsed by nor do they reflect the views or opinions of COLE Publishing, Inc. Comments are moderated before being posted.