By Jake Newhall, Project Manager, WSB

Extreme rainfall events are occurring with increased frequency. Due to climate and environmental changes, many cities and communities are facing an increased flood risk and must act to protect their communities, residents, and infrastructure. A 2019 report by the National Institute of Building Sciences noted that Natural hazard mitigation saves $6 for every $1 spent on infrastructure resilience.

How can community planners, engineers, and elected officials prepare for and protect their communities from flooding? Here are some guidelines to help reduce flood risk in your community when a storm hits.

Preparing for and Understanding the Weaknesses in Your Systems 

Flood vulnerability and resiliency studies are a process for evaluating a community’s ability to withstand rainfall and identify flood risk. These studies look at the existing systems and determine the risks, and where improvements can be made to protect priority infrastructure. This is vital for communities to reduce risks and flood damage to property and public infrastructure – especially in densely populated areas and those near major roadways. 

As we face more extreme weather events, communities should consider increased rainfall depths and intensities so they can be proactive in system planning. The current storm probabilities available have not been updated since 2014, yet rainfall trends show increases over the last decade. Communities can greatly benefit if they anticipate the future probabilities of storms and construct systems that can handle more intense rainfalls. Using a range of design storms, you can determine flood depths, frequency, duration and assign risk to help prioritize funding. 

Completing a risk analysis and inundation mapping utilizing existing modeling can be a low-cost way to start evaluating your system.

Identifying Projects to Reduce Flood Risk

Locating the areas of risk in your community is critical to flood prevention. That could include finding where your system needs more capacity and storage to reduce flooding, determine what properties are prone to flooding, and creating solutions such as relocation, emergency response, or additional flood protection investments. 

Where collected water goes is important when examining and determining updates for your systems. The primary options are to either pass the water downstream into creeks and rivers, or store it in drainage ponds, underground systems, or other storage areas. Another option is to reduce the impervious footprint to reduce the amount of runoff that is generated. Emerging technology allows for predictive rainfall systems that can generate additional storage ahead of a large rainfall event by releasing water early and prior to a peak event through a critical area.

The risk with moving the storm water downstream is the possibility of flooding and eroding the creeks and rivers. If conveyance capacity is increased to the downstream system, it is necessary to make sure that proper measures are taken to avoid flooding and erosion that can harm waters and ecosystems. Water storage options like drainage ponds or underground storage, are options for many communities to utilize. Balancing needs, functionality, and the cost of storage and land is important for communities to explore. Water quality and pollutant removals can be a secondary benefit of many stormwater storage systems that can help communities achieve other goals at the same time.  

Finally, for most communities, the needs often outweigh the budget available to accomplish them all. WSB helps clients navigate flood vulnerabilities, pursue grant funding, and help make informed decisions that best serve a community’s individual needs. 

Jake has more than 15 years of engineering experience designing and managing many types of water resources projects, including modeling, planning, design, maintenance programs, and construction. Jake has worked with various municipalities, counties and state agencies to solve challenging water quality and water quantity problems.

[email protected] | 763.231.4861

By Earth Evans, Director of Water Resources, WSB

The Minnesota Department of Natural Resources (DNR), in coordination with local watershed districts, has developed updated draft Federal Emergency Management Agency (FEMA) flood risk maps and hydrologic and hydraulic analysis. The affected area includes the floodplains in the hydrologic unit code 8 (HUC8) subbasin. HUC8 includes portions of Ramsey, Washington, Anoka, and Hennepin Counties.

The updated hydrologic and hydraulic analysis is based on National Oceanic and Atmospheric Administration (NOAA) Atlas 14 precipitation events across the United States. The draft flood hazard maps may expand existing FEMA regulated floodplains within the Twin Cities metro due to the higher precipitation depth and frequency. The FEMA map updates will likely take effect in 2023. This is the first step in the process to develop updated FEMA Flood Insurance Rate Maps.

It is important that city officials pay close attention to these updates. The draft FEMA floodplain boundaries may increase with this analysis, which may reduce developable area in a municipality, increase the number of properties that are required to purchase flood insurance, and require property owners to change the type of flood insurance they possess. Additionally, the DNR is requiring that each community update their ordinance to require mitigation for fill in the modeled storage areas upstream of FEMA floodplains. 

Currently, the maps are for city officials only. City staff should cultivate a strong understanding of the implications now, before the maps become open for public comment. During the next month, there will be opportunities for city staff to connect with the DNR staff, review floodplain limits, and understand the implications on developable area and properties that will require flood insurance within the community. 

WSB can help navigate this process and facilitate meetings with DNR Floodplain Staff. City officials are encouraged to reach out to Earth Evans, WSB’s Director of Water Resources with questions.

Earth has 20 years of experience as a project engineer and project manager on technically diverse projects in water resources. She is a technical resource in hydrologic and hydraulic modeling, flood damage reduction and floodplain modeling, water quality modeling and evaluation of best management practices, permitting, and hydraulic design. She has has worked extensively with MnDOT and state aid requirements and coordinated with local, regional, and state permitting agencies.

[email protected] | 763.231.4877

By Jake Newhall, Project Manager, WSB

Minnesota’s Municipal Separate Storm Sewer System (MS4s) are currently in the process of applying for coverage under the revised MS4 General Permit. The updated MS4 General Permit creates changes in the ways that MS4 permittees will operate, starting with modifications that address procedural and programmatic changes needed to comply with updated rules. 

One of the main changes is new performance-based responses to Total Suspended Solids (TSS) and Total Phosphorus (TP); including a TMDL assessment to identify and prioritize activities to achieve reductions. WSB’s SWAMP system helps to address these new regulations by streamlining TMDL compliance through tracking and documenting improvements that have been completed to date or since the baseline of TMDL development. The SWAMP system also helps target subwatersheds that are underperforming or lacking the necessary treatment to meet water quality goals. SWAMP improves efficiency by saving time on planning and modeling when developing an efficient plan to address TMDL requirements.

Aside from improving compliance with new MS4 TMDL requirements, SWAMP continues to help address existing MS4 requirements.

• Estimate TP and TSS reduction from existing ponds and BMPs
• Prioritize inspection and maintenance activities related to ponds and BMPs
  • Ensure standard operating procedures are in place and stormwater management features continue to function as designed
• Inspection and maintenance activities are automatically updated and reflect real-time information
• Tracks and stores completed activity records for on-demand reporting

Jake has more than 15 years of engineering experience designing and managing many types of water resources projects, including modeling, planning, design, maintenance programs, and construction. Jake has worked with various municipalities, counties and state agencies to solve challenging water quality and water quantity problems.

[email protected] | 763.231.4861

By Earth Evans, Director of Water Resources, WSB

The new 2020 MS4 General Permit is now available from the Minnesota Pollution Control Agency (MPCA). While there are lots of familiar questions in the permit, the Total Maximum Daily Load (TMDL) application form is new territory for many MS4s. The goal of the TMDL application form is to document progress towards meeting waste load allocations (WLA) for impaired waterbodies that the MS4 discharges to. Unlike previous applications that allowed for a simple qualitative tracking of progress (i.e. listing education programs, ordinance updates, etc.), it is now a requirement to provide documentation of quantitative load reductions, for example how many pounds of phosphorus does your new infiltration basin remove? 

The MPCA has developed a guidance document and a template TMDL spreadsheet unique to each MS4.

But like any new process, there may be some growing pains, so we recommend starting early.

Below are some steps to follow for a smooth transition. 

1. Identify the subwatersheds in your jurisdiction that are tributary to the TMDL waterbody.
2. Gather information on structural BMPs that have been constructed or retrofitted in the subwatershed. 
   • Did you complete a pond maintenance project?
   • Have you coordinated with a Watershed District, Soil Water Conservation District or other agency to construct a BMP?
   • Did you include BMPs with a street reconstruction project?
   • Street sweeping?
   • Have you constructed streambank or slope stabilization repairs?
3. Model to determine the BMP load reduction
4. Input the load reductions into the TMDL spreadsheet

The spreadsheet will need to be updated annually with the MS4 permit application. The bulk of the effort will be invested with this first application form. 

Now that the spreadsheet is updated and there is an understanding of what progress has been made towards meeting waste load allocation and water quality improvements – the next step is outlining a plan to achieve compliance. Subwatershed Assessments are a great method for evaluating, ranking and prioritizing BMPs to continue progress towards WLAs that aren’t met. These assessments focus on identification of drainage areas with little to no stormwater treatment or opportunities for large increases in treatment.  These assessments help the MS4 achieve TMDL requirements or keep waterbodies from being added to the impaired waters list.

The BMP load reductions and cost from the Subwatershed Assessment can be used to apply for grant funding. Reach out to partnering agencies, watersheds, conservation districts to gain momentum, buy-in and funding. There are multiple grants that prioritize funding for projects that work towards compliance with TMDLs.

Earth has 20 years of experience as a project engineer and project manager on technically diverse projects in water resources. She is a technical resource in hydrologic and hydraulic modeling, flood damage reduction and floodplain modeling, water quality modeling and evaluation of best management practices, permitting, and hydraulic design. She has has worked extensively with MnDOT and state aid requirements and coordinated with local, regional, and state permitting agencies.

[email protected] | 763.231.4877

By Jake Newhall, Project Manager & Pete Willenbring, Vice President, WSB

Approaching winter conditions mean more salt in stormwater systems

Chlorides in our local bodies of water have become a rising concern in recent years.  As winter weather approaches and causes icy conditions, our parking lots, roadways and sidewalks are treated with salt to melt snow and ice.

Salt creates safer winter driving conditions, but the environmental impacts of salt use are raising concerns on the long-term effects on fisheries, plant life and surrounding wildlife. The salt used to treat our roadways and pedestrian areas contains chloride that dissolves when mixed with water.  This has resulted in increased chloride concentrations in many lakes, streams, and wetlands.  The elevated chloride levels are high enough in some cases to cause significant environmental impacts.

Removing chloride from water is possible, but the technology is incredibly expensive, and disposal of the chloride removed is a challenge. The primary way to remove chlorides requires high-tech reverse osmosis filters. This is not unlike the challenges presented in treating ocean water for potable source water.  

Monitoring the runoff and impacted surface water bodies in areas where heavy salt application is occurring is allowing us to gain a better understanding of the effects of chlorides on our environment and how communities can manage application rates to balance public and environmental safety.

In recent years, WSB has been working closely with state and local agencies to monitor and track the application, runoff concentrations, and ultimate impacts of chlorides in various locations. The goal is to develop a better methodology to manage the application, potential chloride disposal opportunities, and minimize environmental impacts. Through this research, we’ve been exploring ways to reroute chloride-saturated runoff away from local surface waters and BMPs and protect them from elevated concentrations.

As we continue to monitor and evolve our understand of chlorides, we are developing several initiatives with cities, watersheds, and the Metropolitan Council that will allow us to balance future management strategies, public safety, and environmental impacts of chlorides.

Jake has more than 15 years of engineering experience designing and managing many types of water resources projects, including modeling, planning, design, maintenance programs, and construction. Jake has worked with various municipalities, counties and state agencies to solve challenging water quality and water quantity problems.

[email protected] | 763.231.4861

Pete is a principal and co-founder of WSB. He is a professional engineer, with over 30 years of experience providing consulting services to over 100 city, county, state, and federal clients. Pete has expertise in most fields of civil engineering, but is widely recognized to have developed special expertise in the fields of water resource and environmental engineering, project management, design, and planning.

[email protected] | 612.360.7188

By Tony Havranek, Sr. Ecologist, WSB

Boating, fishing, swimming, and enjoying a day near a lake, river, or stream is part of Minnesota’s culture. Unfortunately, nearly 40 percent of Minnesota’s lakes and streams are included on the Minnesota Pollution Control Agency’s (MPCA) Impaired Waters List. (See the list at https://bit.ly/2BwTk3r.)

Meeting surface water quality standards requires monitoring pollutants that can affect the physical, chemical, or biological makeup of surface water. Phosphorus is one of the main pollutants in the state’s bodies of water. Phosphorus is a pollutant that comes from both external and internal loading sources. Today, Minnesota law limits the use of fertilizers containing phosphorus, but prior to these limits, phosphorus was widely used in several commonly used chemicals settling in our lakes, rivers and streams. Meeting water quality standards requires a reduction of phosphorus in the water column. A water column is the vertical section of water from the surface to the bottom of a body of water.

External sources include stormwater runoff, atmospheric deposition, and directed pipe runoff. Internal sources include sediment suspension, aquatic vegetation, and an overabundance of rough fish. Both internal and external loading sources contribute to surface water quality degradation.

Managing water quality is not only important to the community and the people who live and work there, but it also drives ecological integrity. Because of this, water quality is regulated by federal, state, and local governments.

Where to start
With the appropriate funding and expertise, it is possible to solve water quality challenges and get bodies of water removed from the MPCA Impaired Waters List. Fortunately, numerous funding resources are available through grants, partnerships, and coalitions.

Since water is continuous across landscapes, developing partnerships is often the most cost-effective way to approach managing water quality. It lessens financial burdens and helps many communities achieve long-term success. It also creates opportunities for communities to create long-term plans to improve and protect water quality.

To begin to make improvements, it’s important to understand a community’s water quality issues. Start putting the pieces of the puzzle together by quantifying the scale and source of the pollutant before selecting an approach. The MPCA’s website offers information on a body of water’s total maximum daily load (TMDL) at https://bit.ly/2BbsrVH.

The TMDL is the maximum amount of pollutant a body of water can receive without exceeding water quality standards, and allocates pollutant loads from internal and external sources. In other words, the TMDL identifies all sources of a pollutant and determines how much each source must reduce its contribution.

TMDL implementation actions
Once the TMDL is identified for each body of water, a plan of action can begin to be shaped. Several methods can be implemented to begin to improve water quality.

Public education and outreach. Fertilizers have a major impact on water quality and ecosystems, creating a chain reaction. Excess phosphorus found in fertilizers creates algae blooms. As algae decomposes, oxygen is removed from the water. A lack of oxygen in an aquatic ecosystem effects the native species in a body of water. Educating the public of the harmful effects caused by fertilizer runoff can help limit the amount of phosphorus or other nutrients that flow into bodies of water.

Structural best management practices (BMPs). The MPCA defines a BMP as a stationary and permanent structure that is designed, constructed, and operated to prevent or reduce the discharge of pollutants in stormwater. BMPs can be used for on-site or regional treatment and help a community take a more strategic approach to managing its water quality.

Carp management. Internal loading of phosphorus can be caused by an overabundance of the invasive common carp. High levels of phosphorus cause algae blooms, reduced clarity, loss of aquatic plant and fish habitats, and a threat to human health. Managing and mitigating carp populations improves long-term overall water quality and ecological integrity.

Vegetation management. Invasive aquatic vegetation displaces native vegetation and can release phosphorus into the water column. Vegetation management can help solve this problem. Strategically placed native vegetation can help protect soil from erosion and reduce surface water runoff. Stormwater is then held in place and slowly released, rather than flowing directly into the body of water. Native aquatic vegetation can also help reduce phosphorus-laden sediments through wind and wave action.

There isn’t a silver bullet that can solve a community’s water quality challenges at once, but these are several proven options that can lead to improved water quality and ecological integrity.

This article was originally published in the January/February 2019 issue of League of Minnesota Cities magazine.