The management of storm water runoff has become a priority for many communities in New Jersey in recent years due to the increase of and impact from extreme weather events. Some of the most complicated problems with storm water management occur in Combined Sewer Systems (CSS). In the late 1800s and early 1900s many cities built CSSs, which at the time provided a contemporary solution for conveying sewage and stormwater efficiently from urban areas. In optimal conditions, the stormwater and sewage were combined and conveyed to a sewage treatment plant. But today, with population growth and the concentrated development in urban areas, the piping system of a CSS can become overwhelmed by volume. In such instances, excess flows are diverted (stormwater AND sewage) into nearby waterways through combined sewer overflow (CSO) outfalls. This excess combined sewage can also flood and back up into neighborhoods, which can be a threat to human health. The abatement of CSOs is an expensive and complicated problem to address since urban areas where CSSs exist are often fully developed and because control alternatives, such as sewer separation, can result in significant disturbances. In addition, due to the inter-connected nature of sewer systems among neighboring communities, a downstream region's strategy for addressing its CSOs is directly impacted by the amount of flows from their upstream neighbors which impacts the pipe capacity of the CSS, thereby increasing the likelihood of CSOs.
In response to the Clean Water Act, the National CSO Policy, and the New Jersey Pollutant Discharge Elimination System (NJPDES) Regulations, the NJ Department of Environmental Protection (NJDEP) issued 25 individu al NJPDES permits to require the submission of a Long-Term Control Plan (LTCP) to reduce or eliminate CSOs. These permits were issued to the permittee who owns/operates the combined sewer system as well as the permittee who owns/operates the receiving wastewater treatment plant. These permits affect 21 municipalities in New Jersey with CSO outfalls. The permit requirements stress the development of regional strategies to reduce the amount of storm water that flows into CSSs and requires the municipality and sewage treatment plant to work cooperatively. Public participation and engagement are also requirements of the permit throughout the LTCP process.
Conventional stormwater management techniques include pipes, sewers, expansion of the sewage treatment plant capacity and other structures that are often referred to as "gray infrastructure." One of the more common practices is known as off-line storage, where combined effluent is diverted to a tank, a basin, or a deep tunnel until either the rain event has subsided, or a wastewater treatment plant has the capacity to treat the discharge.
Green infrastructure can also be utilized to abate CSOs. Green infrastructure projects simulate natural hydrologic methods to reduce the quantity and rate of stormwater flow to the CSS. Green infrastructure strategies can include rain gardens, bioswales, porous pavement, green roofs, infiltration planters, trees, and rainwater harvesting rain gardens. These small-scale green infrastructure strategies help to keep stormwater out of the CSS through infiltration, evapotranspiration, and rainwater harvesting. The capture and reuse of rainwater preserves the resource and keeps it out of the CSS during critical storm events. Green infrastructure is also compatible with the principals of Low Impact Development, a land development policy that reproduces natural methods of managing stormwater as close to its source as possible.
The 21 New Jersey municipalities with CSSs are encouraged to include green infrastructure projects in their LTCPs because these measures can contribute to CSO control while providing environmental, social, and economic benefits. In addition to alleviating flooding issues, green infrastructure can improve water and air quality, reduce energy use and urban heat island effects, create green jobs and improve quality of life. Larger scale green infrastructure strategies can also increase recreational and economic opportunities, improve wildlife habitat and biodiversity, and help mitigate flooding. Redevelopment opportunities become more promising as well when infrastructure can handle the population intended to use it.
As community leaders become aware of additional available funding sources, such as the NJ Water Bank, a financing program run jointly by the NJDEP and the NJ I-Bank, they can overcome some of the obstacles that have been impeding critical infrastructure repair. The NJ Water Bank is a vanguard lending institution in the State, helping communities take advantage of available funds with low-interest rate loans and principal forgiveness loans. The Water Bank has dedicated $25 million in Principal Forgiveness Loans for Combined Sewer Overflow Abatement projects utilizing gray and green practices. When NJ entities are willing to invest in their water infrastructure, the benefits are numerous. By doing so, these entities contribute to the stimulation of the economy, the reduction of environmental and health impacts, and the enhancement of communities with neighborhood beautification.
For more information, contact the New Jersey Infrastructure Bank at (609) 219-8600.
3131 Princeton Pike, Building 4 Suite 216
Lawrenceville NJ, 08648 T. 609 219 8600