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Shortly after 1:30 a.m. on Saturday, September 7, 2002, a police officer noticed a problem in the pavement on West Speedway Boulevard in Tucson, Arizona. The officer cordoned off the area. At 2:20 a.m., the first Pima County Wastewater Management employees arrived on the scene. By 3:30 a.m., all utilities were notified of the situation. It was the beginning of an eleven-week project that, for the first several weeks, would require round-the-clock staffing by county employees and contracted employees. Sinkholes Form on West Speedway Boulevard in Tucson Soon after the problem was discovered, a large sinkhole formed near the Arizona School for the Deaf and the Blind on Speedway Boulevard. By 9:00 a.m., a second sinkhole had formed just west of the first sinkhole. A section of Speedway (which is a major east/west thoroughfare in Tucson) would be closed for weeks. All utilities were affected by the sinkholes: sanitary sewer, storm water sewer, water, cable, gas, electric, and phone.
Two sinkholes formed on Speedway -- Northwest Outfall Interceptor sewer crushed. Photo by Jan McDonald Unlike the sanitary sewer system, most other utilities can disconnect service with the turn of a valve or the flip of a switch, and the other utilities in the area were able to turn off service, reroute and then restore most services within 24 hours. However, the sanitary sewer system operates by gravity, and there is no way to “turn off” gravity. In addition to the two sinkholes on Speedway, another problem arose north of the sinkholes. Although no sinkhole formed there (only a depression in the pavement), the area was also cordoned off and repairs to an affected section of the same main were also made. Sewage Flows into the Santa Cruz River The sewer line that was affected was a large interceptor that carried 32 million gallons of sewage (peak dry weather flow) a day from the south side of Tucson to the 42 mgd Roger Road Treatment Plant. When the sewer was crushed, some of that sewage flowed into the sink holes and then flowed by storm water sewer into the Santa Cruz River, although some sewage continued to flow through the damaged line to the Roger Road Plant. All flows to the Santa Cruz were stopped by September 17. This was accomplished when thirteen large heavy-duty pumps were obtained from California, Texas, Utah, and New Mexico. These pumps were used to pump sewage around the sinkhole area. The Santa Cruz River is Cleaned Once flows to the Santa Cruz stopped, clean-up of the river began. Initially, Wastewater Management and Pima County Parks and Recreation employees, raked and bagged a total of 24,680 pounds of sewage-contaminated debris from the Santa Cruz River over six consecutive days. These crews were eventually replaced by contracted workers who continued for an additional 18 days to clean up debris that consisted of toilet paper, human waste, discarded tires, towels, shopping carts, blankets, old clothing, and branches. As debris was cleared, the riverbed was disinfected with a hydrated lime slurry. When the river clean-up was complete, more than 351,180 pounds of debris and garbage had been raked, bagged and disposed of, and 1,962 tons of hydrated lime slurry had been tilled six to eight inches into 179,020 square feet of the river bottom. Most Homes and Businesses Spared In spite of such a major sewer problem, there was very little back up of sewage into the neighborhood or its buildings. The Arizona School for the Deaf and Blind had two of its dormitories affected, a small church experienced a sewage backup, a home with a basement contended with sewage in the basement, and there was a release of sewage into the common area of an apartment complex. While all of these incidents were regrettable, it could have been much worse. It was a battle to keep sewage from backing up in adjoining lines and much effort was put into diverting sewage away from people’s homes. During those first hours of the emergency, assessments had to be made swiftly and plans of actions instituted with little planning. Crews from the County, other utilities and Darhil Inc. (Wastewater Management’s emergency response contractor) all pulled together and worked cohesively and cooperatively to get the project underway. Once the project was underway, subcontractors were brought in to assist. Hundreds of people from different agencies and businesses worked together. During the first hours of the emergency, pumps were installed in key manholes to assure that sewage would continue to flow away from homes. Within days, temporary sewer force mains were strung together all along the streets of the neighborhood. Staff worked long, difficult hours during those first few days; some worked more than 24 hours before going home for much needed rest, only to return a few hours later. The temporary force mains served two purposes. They served as collector sewers for the local neighborhoods, assuring that sewage flowed smoothly away from homes. The above ground pipes also served to carry approximately 32 million gallons of sewage each day from homes and businesses lying south of the ruptured line. These pipes diverted sewage around the damaged pipe in the sinkhole. By September 24, the sinkhole was dry, allowing the repair of the 42” line to begin. When repairs to the sewer main were completed on October 4, 700 linear feet of 48 inch diameter pipe and five new manholes had been installed. Acknowledged Heroes and Unsung Heroes On December 3, a party to celebrate the completion of the sinkhole repairs and to thank all who were involved in the project was held by Wastewater Management. County, city, and contractors’ employees assembled to have a group photo taken and to listen to the thanks and praise made by county officials. One of those speakers was Operations Division Manager John Warner. John’s crews were heavily involved throughout the project and he noted that they were instrumental to the work that was performed. He also remarked that in addition to staff who worked long hard hours at the site, that it was important to recognize those employees who were not directly involved but, who nonetheless, also put in long hard hours performing day-to-day work. John said that in spite of the emergency, other duties and responsibilities had to be performed. Employees who did not work at the sinkhole site performed their own duties while also filling the shoes of those workers who left their regular duties to assist with the project. This was true throughout Wastewater Management as well as in other departments where employees were pulled off regular responsibilities to assist at the site. Many employees (those who worked at the sinkholes and those who carried on with regular responsibilities) were asked to do things that are not normally in their regular job descriptions. All rose to the occasion. The Roger Road Treatment Plant And Treatment Division Staff Affected When the 42-inch sewer line was crushed, tons of dirt, grit and sand were washed away through the remaining sewer line and flowed into the Roger Road Treatment Plant where it soon clogged the facility’s pumps, tanks, basins and conveyance lines. The sediment was very difficult to remove, and some of the infrastructure needed to treat Pima County’s sewage had to be shut down, dewatered and cleaned. When a segment of the plant had to be cleaned, only a single tank, pipe, pump, or basin would be taken out of service, while the remaining facilities continued to treat sewage in spite of being plagued with layers of dirt and grit. Roger Road Plant staff did a remarkable job in keeping the processes running in the face of these problems, and met all their permit requirements in September and October. It took nearly two months for the sediment to be completely removed. Conclusion On November 25, Speedway Boulevard was fully open for the first time in 78 days. Over the course of the project, businesses suffered and the lives of area residents were disrupted. Although no evacuations were necessary, many residents who were unable to tolerate odors, nighttime construction lighting, and noisy pumps were provided hotel rooms paid for by Pima County. The department’s hourly employees logged many hours in overtime pay. Although final costs have not yet been completely figured, the emergency response and repair expenditures are estimated to be $7.7 million. In spite of the costs involved, representatives from both the private
and public sectors worked together to expedite repairs while safeguarding
the environment and public health. It was an incredible effort that
will not soon be forgotten. |
