Monday, October 1, 2012

Can the Grease to Keep Sewers Flowing

Starting this week you might begin to see utility trucks in Fairfax with signs to “Can the Grease” or “Stop the Grease.” Fairfax County Department of Public works is launching a new education and public awareness campaign to get you to stop pouring grease down the drain. When you flush it down the toilet, grind it in the garbage disposal, pour it down the drain in Fairfax county, most likely the wastewater and all that it carries with it travels through the 3,300 miles of sewer pipes within Fairfax county and ends up at one of six regional waste water treatment plants for the county: Noman C. Cole, Upper Occoquan Service Authority, Blue Plains, Alexandria Renew Enterprise, Arlington and Mooney in Prince William.  There are still a few areas in Fairfax that have septic systems covering the rest.

Fats, Oil and Grease, FOG as it is called in the waste industry comes primarily from food such as cooking oil, lard, shortening, meat fats, sauces, gravy, mayonnaise, butter, ice cream and soups. Sinks, dishwashers, cleaning wastewaters and food scraps put down disposals deliver the FOG to the sewer system, it can be liquid or solid when you put it down the drain, but turns viscous or solid as it cools in the miles of underground sewer pipes. As the FOG builds up, it restricts the flow in the pipe and can cause sewage to back up into homes and businesses, or premature failure of the sewer pipes, increased incidence of sinkholes. I was fortunate to be able to speak to Tom Russell, Director, Wastewater Collection Division Fairfax County, VA DPWES who manages the 140 employees and construction programs that keep the sewage flowing in Fairfax and has been with Wastewater Collection 16 years- about half his career as an Engineer and manager with Fairfax. Tom made sewer pipe maintenance sound so interesting that I took way too much of his time during an early morning interview.

FOG only really creates problems for the sewer lines if there is a disruption, like a tree root in a joint, or sag under a highway, a pumping station or something that might give the FOG a chance to catch on the pipe surface and cling to the walls of the sewer system. Since all pipes have some friction points, FOG is always a problem.  The FOG builds up one layer at a time making a smaller, narrower path for the water and waste to travel through, ultimately causing a backup or pipe to burst. Restaurants and fast food places produce much larger volumes of FOG than residences, so in Fairfax there is more aggressive monitoring of sewer pipes and manholes downstream of the malls and shopping centers. Time creates wear and tear on a pipe and without the aggressive maintenance in Fairfax there would be a much larger problem. In addition, restaurants and commercial kitchens are required to have grease traps between the sink and floor drains and the sewer connection and capture and recycle their grease, by having it hauled away. Nonetheless, this past year, there was a massive sewage back up along the side of I-66 across from Fair Oaks Mall. The 18 inch sewer main under I-66 will be replaced at a cost of $1,000,000 and completed in spring 2013, the Wastewater Collection Division has managed to prevent additional backups in the interim by getting the Health Department to address the compliance of the restaurants in the mall with the county regulations for grease and commercial kitchens. Better control of the grease in the mall food court prevented further backups in the damaged section of piping.

Maintaining the sewer pipes, clearing tree roots and keeping grease out of the system can prevent most sewer backups. Every day the Wastewater Collection Division does visual inspections of sewer lines and manholes using portable cameras put down manholes and a special closed circuit TV camera, CCTV, that the crews use. The manhole inspections are generally done in the neighborhoods and the larger sewer mains are checked using CCTV. The CCTV crews use their equipment to view 240 miles of sewer lines each year. Sewer lines range in size from 8-72 inch diameter, and the CCTV is used to monitor deterioration in the lines. There are 88,000 manholes in Fairfax and each manhole is viewed every 3-5 years depending on the age and material of the pipe and whether the pipe has already been rehabilitated. There are some county sewer lines that are inspected quarterly or even monthly if necessary.  Neighborhoods built after 1970’s contain PVC pipe are checked less frequently because PVC has been demonstrated to last longer, 50-100 years in other parts of the country.  

The sewer system in Fairfax County was built out over the last 70 years as the county developed. Every year Fairfax County spends $6,000,000 in a planned program to rehabilitate 125,000 feet of pipe within the sewer system. Rehabilitation of sewer pipes involves sliding a resin impregnated fiberglass liner into the pipe at a manhole and using steam to rapidly cure the lining and have it bond with the existing asbestos cement (transit) or cement pipes. After the lining is in place the connections of the lateral sewer pipes is cut out. The curing process leaves an indentation where the lateral joins the sewer main and the vendor the county hires to do the work cut out the “coupons” to open the laterals. Rehabilitating a sewer main takes just one day from early morning until late afternoon and then the residences or businesses can go back to normal use of water. The sewer system in Fairfax is fairly young, and the current program of planned replacement is a fraction of a percentage of the piping in the system.  Nonetheless, during the last fiscal year ended July 1, 2012 Fairfax had only 19 backups and manhole overflows in the Fairfax owned system and 2 pipe collapses attributable to maintenance issues.

You might be thinking that there were more sewage backups in Fairfax during the past year after all, how would the rooter companies (like Rotor-Rooter and Rescue Rooter) make a living if sewage did not backup with certain regularity. It is true, there are more sewage backups in Fairfax, but they do not belong to the county. In Fairfax County there is private ownership of the lateral sewer lines from the building until it ties into the county sewer main. The homeowner or building owner in Fairfax is responsible for the entire lateral line (even past the property line) and the connection. So, when sewage backs up into your house and you call the county they will dispatch a crew to open the manhole on your street and see if the sewer main in blocked. Chances are that the sewer main is clear and Fairfax will tell you the problem is yours. They do not count these backups in their statistics.

In the sections of the county that developed after World War II and until 1970 Orangeburg pipe was used for the sewer laterals. Orangeburg pipe was piping made by Orangeburg Manufacturing Company of  ground cellulose fibers bound together with a special water resistant adhesive, and then impregnated with liquefied coal tar- basically tar impregnated cardboard pipes. The joints were made with couplings of the tar impregnated cardboard. Over time, the pipe have proven susceptible to deformation and root intrusion two things when combined with a lot of grease cause sewer backups. This year could be a very bad year for sewer backups into homes because during droughts tree root seek the moisture in the sewer pipes and infiltrate the pipes especially the old Orangeburg pipes. Because these sewer laterals are essentially made of cardboard, using a spinning rotor to cut out the roots is likely to ultimately abrade away the pipe wall, but can be done several times before the pipe fails.

The grease from holiday cooking combined with the root infiltration from a dry summer are likely to result in a sewer backup in your home at the most inopportune time. The worst maintained pipes in Fairfax County are the laterals owned by the property owners. It is very expensive to replace your lateral sewer pipe because the homeowner not only has to trench their yard but also cut the roadway and curb to replace the pipe and connect a new lateral to the sewer main. After the pipe repair is complete the property owner is responsible for repairing the road and curb. In the late 1960’s PVC (polyvinyl chloride) pipe replaced Orangeburg pipe. There are a lot of sewer backups in Fairfax and there are other problems caused by the historic residential construction. The sanitary sewer system in Fairfax is an entirely separate system than the storm sewer system, but there are still storm related increases in flow due to the infiltration of stormwater into the sewers and flow of stormwater into drains and sump pumps illegally discharging in the sanitary sewer system. That excess flow can result in more than 150% of the average daily sewage flow.  When many of the homes in Fairfax were built, it was perfectly legal to connect basement drains to the sewer lateral and use the sewer system to transport the groundwater out of the neighborhood. Excess flow, root infiltration in the pipe and grease build up will ultimately cause the lateral to rupture. So, the County’s advice to “Can the Grease” is good advice for homeowners to save yourself some money and prevent sewer backups in your home.

I would like to thank Irene Haske and Tom Russell of Fairfax County Virginia Department of Public Works and Environmental Services for their time and help in researching this topic.    

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