Bayonne officials have announced the results of a new technology that, over the past year, has substantially reduced the amount of both naturally-occurring and preventable sewer blockages throughout the city.
The blockages pose an added burden to Bayonne’s antiquated combined sewer system. They worsen the already massive overflows that can be seen in the streets, waterways, and homeowners’ basements.
Blockages are just one of the many factors associated with flooding. Bayonne’s pipes carry storm and waste water through the same channels. Storms cause the system to overflow and discharge untreated sewage into surrounding waterways and homes.
Storm water on impervious surfaces has nowhere to go as a result of the overload. It doesn’t help that the city is a flat peninsula, only seven feet above sea level at its highest.
“There’s more than one thing going on here,” Department of Public Works Director Timothy Boyle said. “The thunderstorms we see over the summer are far more intense than they used to be. Once the system finally gets overwhelmed by one or two inches of rain in less than an hour, it’s a volume of water that can’t be captured by our system, and gravity and geography take everything over.”
Boyle said that figuring out which areas will be hit the hardest is highly unpredictable, because storm patterns are patchy. He said that the inches of rain per-hour are too much for any utility to eliminate flooding completely.
There’s a plan that municipal utility officials believe will reduce flooding drastically, but it’s likely going to take decades to implement.
A new technology employed by Suez-Bayonne, called SL-RAT (Sewer Line Rapid Assessment Tool), can quickly detect and clear blockages in drains and storm lines caused by detergent, grease, and natural substances.
Suez-Bayonne reports that from January to June 2018, Bayonne experienced 47 sewer blockages. From January to June 2019, Bayonne had only eight blockages, representing an 83 percent decrease.
The technology transmits sonic waves through a pipe on one side. A receiver placed downstream from the transmitter picks up the acoustics, and the quality of the signal shows if there’s a full blockage. It can even pick up blockages in their early stages. The blockages are removed with pressurized water jets, restoring pipes to their original condition.
“The City of Bayonne has been concerned about sewer blockages for years,” Boyle said. “Street litter, mud, and disposable wipes which are not really flushable do not belong in our system and are a constant concern. We are impressed with the effectiveness of the SL-RAT in dealing with blockage problems.”
Judging by photos taken by Bayonne residents over the summer,which appear to show geysers of water erupting from manholes during storms, removing blockages at an efficient rate can go only so far in stemming Bayonne’s floods.
The use of SL-RAT technology is more of a stopgap in anticipation of a citywide overhaul of the sewer system, which doesn’t have the capacity to handle the volumes it takes in during increasingly heavy storms, no matter how clear the pipes are.
While clearing the pipes hasn’t eradicated Bayonne’s massive floods, the city is one of 21 New Jersey municipalities tasked with drastically reducing the amount of combined sewage overflows in their systems, in order to comply with New Jersey’s 2015 Clean Water Act.
Engineers have spent more than four years mapping the blueprint for an overhaul of Bayonne’s sewer system, which will involve 20 years of construction at a minimum.
An evaluation submitted for DEP approval estimates the cost at $300 million, according to the current plan. That would make this project the single greatest investment in infrastructure the city has ever made.
“We need to use taxpayers’ money slowly, thoughtfully, and carefully,” Boyle said. “There will be a lot more refined decision-making at ongoing public meetings.”
Bayonne’s long-term plan will rely heavily on stormwater control and underground storage upgrades, because these are the most feasible to address flooding.
“Tanks and pumps will be adding a lot more standstill capacity to our system,” Boyle said. “We’re looking at how much volume we can get the actual system to hold, how many tanks we’ll install, and how to conduct the flows. The engineering is endless, very intense, and subject to change as each piece of the plan will be installed in phases over what we expect to be a 20-year build-out period.”
Green or grey?
Bayonne officials proposed an underground cistern beneath Fitzpatrick Park, and received approval to do so, as long as they make upgrades to the park.
It sparked one of many debates between utilities and green infrastructure advocates, who would prefer to see rain gardens, bioswales, and other stormwater collection methods instead of upgrades to storage tanks, tunnels, and pumps.
Green infrastructure captures stormwater at the source before it reaches sewers. For meaningful impact, it often has to be installed over a large space.
Boyle said that a long-term control plan with heavy reliance on green infrastructure could cost as much as $1 billion.
“We’re in an urban environment, and as nice as it would be to think of parks as the last bastion of the trees, green infrastructure is very poorly understood,” Boyle said. “There’s a great deal of engineering and math involved in it.”
While Boyle said that the city might consider a long-term control plan that involves a portion of infrastructure greater than three percent, it remains a low priority for the Passaic Valley Sewerage Commission. Boyle said that the city is open to filling in patches with green infrastructure based on what it deems effective and economical.
For example, conflict arose over Fitzpatrick Park, where the utilities received approval to install an underground cistern for stormwater storage. Nearby residents have been calling for parks to be untouchable when it comes to installing grey infrastructure.
Boyle said that no matter how much green infrastructure is installed where the cistern is slated to be, it wouldn’t reduce the problems faced by residents just south of the park whose homes get severely flooded.
While the plan sacrifices the tree canopy, Boyle said the DEP advised against installing a large number of storage tanks in public parks.