TWM Contributor: Chris Kuester, PE, CFM

Date: April 2021

Is Your Development Drowning in the Permitting Process?

One of the largest components of successful site development is navigating the permitting process. Depending on the site’s location, this could range from a simple local municipal zoning approval to obtaining approvals through specific City Council sub-committees that require multiple public sessions and presentations. There are also numerous state and federal agencies that could require separate approvals prior to construction beginning. TWM’s Land Development Group prides itself on partnering with our clients throughout this permitting process to ensure a smooth transition from initial conceptual design to construction-ready plans.

As development continues in growing communities, prime developable land with minimal site constraints becomes more scarce and more expensive. Depending on the permit and regulatory agency, there can be extensive application and review fees which, in extreme cases, can significantly alter the project’s profitability.

One of the most common site constraints developers face when looking for obtainable land is limitations of bordering waterways or floodplains. In particular, regulatory floodplains, which are managed by FEMA, can be intimidating but their impacts can be minimized through careful planning. Several key components can help provide a clearer picture when assessing a project’s viability and profitability:

Storm Probabilities

Rainfall events are commonly categorized by their recurrence interval. For example, a 100-year storm would be a rainfall event that has a 1-in-100, or 1%, chance of occurring in any given year. Municipalities and regulatory agencies often require some aspects of developments to be designed for certain recurrence intervals. Examples include a site storm sewer that may need to provide capacity for a 25-year event (4% chance of occurring in a given year) while a roadway crossing over a culvert may need to be elevated above the high-water elevation generated by a 50-year storm (2% annual chance).

Base Floodplain Elevation

Also commonly known as the BFE, the Base Floodplain Elevation is the high-water elevation calculated for a 100-year storm. When a structure is assessed for whether it requires flood insurance, the structure’s lowest opening elevation must be located above the BFE. Many municipalities have freeboard ordinances requiring that this lowest opening for new construction be located with an additional amount of height above the BFE. Additionally, homeowners who wish to remove the requirement to carry flood insurance can submit an Elevation Certificate to FEMA in which a licensed surveyor verifies that the structure’s lowest opening is above the BFE and the structure is not at risk of flooding in a 100-year event.

Floodplain, Floodway, & Flood Fringe

While these terms appear very similar, they represent very different elements and their impacts on a project can vary greatly. Understanding how these definitions differ can help both the developer and the engineer assess a project’s necessary permitting in its conceptual stages. Illustration below: Understanding the Riverine Floodplain (per the IDNR’s OWR’s Floodplain Management in Illinois Quick Guide).

A floodplain is simply the area that will be underwater for a given rainfall event. A FEMA Flood Insurance Rate Map (also known as a FIRM) commonly shows the 100-year and 500-year floodplain extents. By contrast, the floodway is an area within the floodplain where construction would cause a high-water increase, thus exceeding the regulatory requirements. For example, the State of Illinois sets its floodway limits based on an allowable 0.1’ increase. The flood fringe is the area between the edge of the floodway and the floodplain where construction could occur without needing to provide detailed hydraulic calculations. This construction is typically done after obtaining a Conditional Letter of Map Amendment or Conditional Letter of Map Revision from FEMA.

When planning site developments, avoiding areas prone to flooding is desirable but often unavoidable. A smooth permitting process begins in the project’s conceptual stages and is best done when the developer and engineer work in concert to assess the amount of buildable land. Having a greater understanding of a floodplain’s components can help when working with local municipalities to ensure a project will be safe for its citizens as well as when obtaining a permit from FEMA or a state agency. The permitting process doesn’t have to capsize your progress – TWM has extensive experience to help you navigate the waters and keep your development afloat!

Find out more about TWM’s Water Infrastructure and Wastewater Services, including Stormwater Management.

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