Have you identified any stormwater facilities in your municipal jurisdiction that are no longer meeting current volume requirements? Well, you are not alone.
Infrastructure built as a 2-year, 24-hour design storm or even a 25-yr, 24-hour design storm may not be able to handle the frequency and intensity of rain events that have increased over the last 10 years, which is causing many municipalities to deal with localized flooding.
Engineers use the term “design storm” to determine a hypothetical storm event with specific rainfall characteristics, like intensity and duration, used to design infrastructure like drainage systems, considering a specific probability of occurrence, often referred to as a “return period” (e.g., a “100-year design storm” meaning there’s a 1% chance of such a storm happening in any given year) to ensure the infrastructure can withstand a certain level of rainfall volume and intensity.
The EPA is cracking down on the number of flooding events outside of a natural disaster. In other words, older infrastructure may not be able to handle the volume of current rain events. This causes several health and safety issues, including Sanitary Sewer Overflow’s (SSO’s) due to infiltration. Infiltration of stormwater happens when there is no place left for stormwater to go, therefore it enters the sanitary sewer. Laurie Murphy, Stormwater Specialist from the Stormwater Training Center states that, ”bacteria that is released due to infiltration is one of the largest human health issues due to seepage into drinking water supply reservoirs.”
How do we solve the problem? Murphy states, “that the first indication of a problem is when localized flooding happens without a storm sewer blockage. This is a clear indication of infrastructure failure. Other notable issues that should be ruled out are increased urban development, which generates higher runoff, further stressing older stormwater systems.
Having a Capital Improvement Plan to address the future health and safety of a community is paramount.” Of course, lack of funding is a consistent obstacle. There are a variety of options to fulfill the replacement of older infrastructure. Murphy states that, “ 319 Grants offered by the EPA are a good start as well as Public-Private Partnerships or perhaps the purchase of an Enterprise that brings in residual income.”
For more information on Municipal Training and Certification, go to www.thestormwatertrainingcenter.com
