Recently, the Federal Emergency Management Administration (FEMA) released the National Mitigation Investment Strategy (NMIS) outlining the framework for a coordinated, federal and national investment strategy for mitigation. The three goals of NMIS are to: (1) show how mitigation investments reduce risk, (2) coordinate mitigation investments to reduce risk, and (3) make mitigation investment standard practice. Now that the strategy is in place, the next planned phase is implementation.
Since the majority of infrastructure (and the funding thereof) in the United States is constructed, operated and maintained by local governments, public works professionals must step up and take the lead role in this mitigation effort. Existing public works projects are direct investments in the community that can have a role in reducing risks posed to buildings and infrastructure from hazards in the community. The important connection to make is many public works operations and projects have mitigation components. Public works professionals need to improve on outreach in communicating to stakeholders that there are mitigation activities already taking place and describe how and what these infrastructure investments mitigation benefits are.
Mitigation efforts can consist of both little and big components that collectively add up to a more prepared community. Bringing together the right stakeholders, including public works professionals, collectively working to identify mitigation opportunities will make the community more resilient.
Operational Mitigation Efforts
The city of Crystal, Minn., sweeps all city streets a few times a year to remove the debris such as sediment, vegetation and litter from the streets. Street sweeping prevents the debris from entering the stormwater system and creating issues related to water quality, stormwater flow through pipes, and pollution. Sweeping streets also has a mitigation component in that the debris removed from the streets is debris that could have clogged catch basins during rainstorms and caused localized flooding. Street sweeping is a good example of a normal public works task, funded by local governments, that has a mitigation component people might not readily think of. Like all mitigation efforts, there is no one solution and street sweeping should be thought of as one component of a larger mitigation effort by a community against hazards (primarily natural in this case).
Over the past few years, the city has been evaluating all intersection traffic control devices according to the Minnesota Manual on Uniform Traffic Control Devices (MnMUTCD). Through this process, a significant number of signs have been removed or changed. One example of the impact of this effort is that 13 percent of the stop signs have been removed in the city and another 12 percent have been changed to yield signs. The removal of the signs does bring the intersections into alignment with MnMUTCD guidance, but other benefits include reduced maintenance costs for the city, reduced vehicle delay, reduced vehicle emissions, and reduced wear and tear on vehicles. Should a major storm hit, fewer signs also means less potential debris. While this effort, and its mitigation benefit, is small in the grand scheme of disaster costs, it is an example of a very low-cost city initiative that provides benefit to the community every day.
Since 2016, the city no longer plants trees in the public right of way adjacent to streets. While this may seem counterintuitive, there are a number of benefits. First, not having trees along streets allows more sunlight to shine directly onto the roads in the winter when the sun is lower in the sky, helping with the natural melting of snow or ice. Since there is more sunlight on the roads, there are fewer problematic areas that require additional anti-ice treatment and the city is able to use less salt. Minimal salt use saves taxpayers money and is better for the environment. Another benefit of not having trees directly along streets is there are fewer leaves and other natural debris falling directly on the street that can clog catch basins and cause localized street flooding during rain events. Finally, if there is a significant storm that causes wind damage, trees located further from the road are less likely to fall and block the roadway. If a branch does fall, it is from the higher parts of the tree, which are generally smaller, and are hopefully easier to clear. From a response standpoint, reducing any potential for blockages that restrict emergency access or divert resources to clear the obstruction is a value added.
In 2018, the city completed a long-term effort to replace the existing sanitary sewer lids (manhole covers) that had holes in them with solid cover lids. This seemingly minor change reduces rainwater from entering the sanitary sewer system from surface streets. This change will save the city money by not having to pay for treating the rainwater entering the sanitary sewer system. Minimizing inflow will also reduce the flows pumped into the sanitary sewer lift stations and allow more capacity to be available. Reducing the volume of wastewater to be pumped at the lift stations also reduces the engine hours of the pumps and general wear and tear, thus extending the life of the pumps.
Project Mitigation Efforts
Starting with street reconstruction projects in 2016, the standard width of city streets was reduced from 30 feet (curb face to curb face) to 28 feet. This two-foot reduction in pavement space reduces construction costs (less asphalt and base) and reduces the future street maintenance costs. For northern climates, this is less street area to plow in the winter months. Narrower roads can have an impact on traffic and help reduce vehicle speeds, especially if vehicles are parked on the street. From a mitigation standpoint, less hard surface (impervious area) means more pervious (grass) area and less stormwater to manage, both at the location and downstream.
Taking the street width reduction to the next step, the city also had the opportunity to remove segments of streets where there had not been direct private property access. One of these street blocks had divided a park in half and removing the street segment allowed the park to be connected and provided space for a larger ballfield. Similarly, a few years ago the only remaining gravel road in the city serving fewer than 200 vehicles per day that also divided a large city park was closed. In addition to the reduced long-term maintenance costs, from a stormwater perspective the permanent road closures considerably reduced the impervious area where stormwater runoff needed to be managed.
The city has constructed four underground infiltration chambers over the past few years. One of the chamber systems was constructed as a mitigation measure against the somewhat regular flooding of the lower level of the police department. Since construction, it has been successful in preventing flooding, even with intense rains. Another underground infiltration system was constructed to capture and infiltrate water upstream of a known localized street flooding location. The underground infiltration tank alone was not enough to address the localized flooding issue, but it was an important component of reducing the volume of water that needed to be managed further downstream. This summer, the city constructed the largest underground infiltration system in the downtown area city park. Able to hold up to 2.2 million gallons of water, which is the volume of runoff from a 0.6-inch rain event over the 145-acre watershed upstream, this underground system will help reduce localized flooding as well as have a significant benefit on water quality downstream. Similar to other public works operations and projects, underground stormwater infiltration systems have a variety of benefits that include mitigation components.
One of the traditional mitigation efforts is installing backup generators at critical pumping stations (water, sanitary sewer, or stormwater) for use during power outages. The city has been working on installing generator backups at pumps for a number of years and is 50 percent complete with another one planned for installation in 2020. An important benefit of providing backup power that can be forgotten about is, by providing a fixed backup generator at a location, it reduces the staff and equipment time needed to shuttle between the different locations with a portable generator to try to keep sanitary sewer lift stations from backing up and impacting properties while there is no power.
In 2021, the city has a stormwater project planned that includes the replacement of an older stormwater pumping facility. The stormwater pumping facility is critical because it controls the water level in a landlocked pond that is at the end of a chain of ponds with various adjacent structures and roadways through the central core of the city. Pumping water out of the pond is the only way to lower the pond level after rain events. As part of the design process, providing redundancy in pumping operation is something that is being evaluated. This redundancy means that should a pump go down for whatever reason (planned maintenance or otherwise), the city will still have the ability to remove water from the pond. Additionally, relocation of the actual pumps and controls to a higher elevation from the pond is being considered to provide extra buffer space from potential flooding from mega rain events.
Public works operations and projects go hand-in-hand with mitigation. As FEMA moves toward implementation of the National Mitigation Investment Strategy (NMIS) at all levels, public works professionals must fully engage, and be engaged by other stakeholders. The National Mitigation Investment Strategy is feasible and, by looking through a mitigation lens at public works operations and projects, it can be seen there are many public works practices already being done that have a mitigation benefit. What has been done is a good foundation as we collectively move forward toward building a more resilient country and the National Mitigation Investment Strategy is an important step in speaking a common language around mitigation.