Inflow & infiltration (INI)

Here's a guest post from Steve Carroll on the sewers:

Early in 2005, after an exceptionally rainy spring, the volume of waste waster flowing through Cheshire’s sewer treatment plant far exceeded the 3.5 million gallon capacity of that plant. During some particularly heavy downpours, the volume of waste water flowing through the plant exceeded 7 million gallons a day. The result was that the 6-month rolling average for daily flow through the plant broke the 90% barrier for the first time, automatically triggering the process to begin planning for an eventual expansion of the plant. By most estimates, the eventual expansion of the plant will likely cost in excess of $20,000,000 and possibly much higher.

Two years later, in April 2007, another exceptionally rainy period of 2 or 3 days caused the volume of waster water to spike again, this time spilling untreated effluent onto Riverside Drive.

So what’s wrong with this picture? Well, a couple of things. First is the fact that rainwater is supposed to be handled by our storm water system, not our sewer system. Second is the undeniable fact that, the harder it rains, the higher the flow of waste water through the sewage treatment plant. And third, here we are two years later with no real answers or substantial progress. Looking at past plant figures, one would have to conclude that Cheshire has a significant I & I (inflow and infiltration) problem, much more so than a capacity problem. It also seems apparent that the I & I problem is so serious - allowing millions of gallons of water into the sewer system in a matter of a few hours - that even if the plant were upgraded, the I & I problems would likely continue to overwhelm the facility during heavy periods of rainfall.

In 2005, as details were first emerging about the capacity issues at the plant, there was an immediate reaction from all sides to determine the underlying causes for the spike and an ensuing discussion regarding the possible remedies for each of the contributing factors. We discovered that the prison was exceeding their capacity. We stiffened penalties for homeowners with illegal hookups to the sewer system. And we hired inspectors to inspect a number of homes for illegal hookups. All the while, the WPCA, as it is required to do, advanced its plan for an eventual upgrade to the sewer treatment plant, and for increasing the overall capacity of the plant. The problem here is that despite all of these efforts, we have yet to identify a single, significant factor responsible for the spikes in volume, never mind the primary cause.

What the town has failed to do for the past two years is to initiate and undergo a thorough assessment of the sewer system infrastructure – beyond the plant - to determine if, and where, there are major structural breaches in the system, and to develop a plan to immediately address those problems that are uncovered. The fact that millions of gallons of rainwater can infiltrate the sewer system in a matter of hours and days is a strong indication that there are major breaks, and likely numerous ones, within the underground pipes that control the flow of wastewater to the treatment plant. This is an urgent problem, and probably the most pressing issue facing the town at this point in time, with long-term implications for the community and future development.

Unfortunately, this delay now may cost the town in terms of new development opportunities. Identifying and fixing major infrastructure problems will not be cheap and will likely cost in the millions of dollars to repair – but it will pale in comparison with the price tag of a new sewer treatment plant. Inspecting and assessing the sewer system infrastructure is well within the abilities of the WPCA and our Public Works department to perform. But it is way overdue. We need to encourage our elected and appointed officials to take action – now, not later. I wholeheartedly endorse the development of a plan to eventually upgrade the sewer treatment plant. It has been about 15 years since the plant was last upgraded (for capacity) and it is time to plan for the next 15 years. But the town should simultaneously – and aggressively – be making efforts to identify and correct major flaws in the existing sewer system infrastructure.

Steve Carroll