Fresno Says No to Fats, Oils and Grease
August 21, 2012The City of Fresno, Calif., has taken a proactive approach to the care and upkeep of its sanitary sewer system, resulting in fewer sanitary sewer overflows (SSOs) and a stronger system for its customers.
Fresno is no different than any other city in North America — large or small. Public works/utilities officials must maintain its sewer system the best way they can, using the most cost-effective means available to them. Programs such as the ones for pipe cleaning, inspection and a fats, oils and grease (FOG) control are just a few ways cities can maintain its lines — and Fresno uses all of these avenues.
Located in the San Joaquin Valley, the City of Fresno was established just after the famed California Gold Rush in 1856. The city and county of Fresno is situated between two well-known cities — San Francisco and Los Angeles — and is south of the state capitol of Sacramento. The sanitary sewer system is used to service the City and County of Fresno, as well as the City of Clovis and other unincorporated areas of the Fresno County. With a population of approximately 496,000, Fresno is the fifth largest city in California. The primary industry for the County of Fresno is agriculture, with crops and livestock ranging from turkeys and cattle to grapes, milk and oranges to name a few.
Fresno’s sewer system is not as old as others in the United States, but like those systems, it is starting to show its age and needs cost-effective programs to maintain it. “The system in general dates back to the early 1900s but there are few sections that were built as early as 1890,” says Arturo Alvarez, collections supervisor for the City of Fresno Department of Public Utilities Wastewater Management Division. “We had a lot of growth — city and system — in the early 1970s and another growth spurt in the mid-2000s. Percentage-wise, 6 to 7 percent of our system is more than 75 years old. Overall, our [sewer] pipes are in pretty good condition.”
The Department of Public Utilities Wastewater Management Division (DPUWMD) maintains 1,500 miles of sanitary sewer, as well as 23,000 manholes and 15 lift stations. A majority of the pipes are made up of vitrified clay pipe (VCP) and polyvinyl chloride (PVC) with a few other types in the mix. “We have 840 miles of vitrified clay pipe vs. 400 miles of PVC,” Alvarez said. “The vitrified clay is found mostly in the city, with the PVC in the outlying areas [or newer sections of Fresno].”
In 2006, the State Water Resources Control Board in California issued Statewide General Waste Discharge Requirements (WDR) for Sanitary Sewers Systems, affecting those entities that operate/own collection systems greater than one mile in length and requiring them to design and implement a sanitary sewer management plan (SSMP). Within this plan, a FOG control program needed to be included.
Fresno had a head start over some California collections systems as the DPUWMD already had a basic FOG program designed and was working to fine tune and implement it. “We were really close to having a FOG control program in place when the mandates were made,” said Rosa Staggs, DPUWMD chief of wastewater environmental services. “We improved on what we had come up with and added it to the sanitary sewer management plan.”
In developing Fresno’s FOG control program, Staggs said other cities similar in make-up and system size, such as the City of San Jose, were contacted to learn how they approached designing their programs. “We have also attended a number of training conference seminars related to FOG — long before the 2006 mandate,” she said. “We were trying to be proactive and see what other cities were doing in relation to inspection of restaurants — we have approximately 800 restaurants — and how they deal with grease haulers to dispose of FOG once they clean the interceptors and grease traps.”
The DPUWMD has worked hand-in-hand with the DPUWMD’s industrial, commercial and residential customers to execute the FOG program and both Alvarez and Staggs said the program has received everyone’s cooperation. “The best selling point for food service establishments is that if best management practices are not followed, such as scheduled cleaning of grease traps or interceptors, grease can accumulate on private laterals, and they will have to call a plumber to have it cleaned, which is costly,” Staggs said.
Alvarez has been with the DPUWMD for 15 years and he recalled that prior to 2007, there was a need to better understand what was going on in their sewers. “Until 2007, we only had one CCTV truck. We purchased three [Aries] video trucks in 2007, which has allowed us to get a better idea of what the system has inside and what the grease does to the pipes,” he said.
“When you are cleaning, you assume you are getting everything off the walls but some of that grease solidifies to the point where it’s surprising how hard it gets and you have to use other means beyond jetting to remove it,” he said. “Now, we are able to video inspect sewer lines, to view what the system is doing, to better understand root-cause problems that influences the delivery of our services.” Staggs and Alvarez describe the problems the system has encountered as blockages, overflows and loss of pipe diameter due to FOG. “There wasn’t any serious damage to the affected pipes, such as corrosion but there were sanitary sewer overflows due to grease blockages,” said Staggs.
Beyond the FOG issues, the system also was somewhat affected by roots. Alvarez noted that a chemical root control program was implemented four years ago and it is showing good success with it. “We definitely have some areas affected by roots,” he said, attributing a lot of the root issues to the older vitrified clay pipe that has gotten displaced and had joint movement over the years due to ground movement. “There were a lot of things they couldn’t foresee when they laid these pipes in,” he said. “I doubt they considered we’d have [heavy] trucks running over these roads on a weekly basis,” which could cause settlement.
With the root control program, work crews CCTV the lines in historically root-infected areas prior to chemically treating them, determining which lines are in need of the chemical application. “By videoing the lines first, we won’t treat lines that don’t need it,” Alvarez said. “We are able to document it as we go to determine the treatment’s effectiveness.”
The DPUWMD also has a pipe cleaning program in place, in which they clean all its lines under 15 in. in diameter annually, using its fleet of six jetter/vacuum trucks and four jetter trucks (all Vactor Mfg. and Super Products brands). “As our CCTV library grows and we are able to document the characteristics of each line, we can make adjustments. Some may not need to be cleaned every year, allowing us to allocate personnel and cost to other jobs,” Alvarez said.
Through its FOG program, pipe cleaning and general maintenance efforts, the DPUWMD has seen improvement in the lines, noting fewer SSOs and the frequency of cleaning at its commercial users has come down. “Everything is still a learning process right now,” Alvarez said. “We have eliminated repeat SSOs in the same location and we are treating the grease at the source.”
Staggs noted the importance and priority DPUWMD has placed on training its staff to handle the maintenance program. “It is very important to train our staff and we try to send them to as many training opportunities as possible. Today, it’s more than just cleaning the sewer lines. The staff gives us input on the condition of the lines which can translate into future rehabilitation and/or capital improvement projects. We want the staff to understand that. We have really stepped this up the last two years and it’s making a difference,” she said.
Sharon M. Bueno is managing editor of Trenchless Technology.