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The Importance of Timing a Wetland Delineation

A wetland delineation is a procedure that determines the location and extent of wetlands on a property. This is typically completed before a property can be developed due to state and federal laws that regulate fill or drainage of wetlands. The delineation evaluates and documents wetland indicators using soils, vegetation, and hydrology. The regulatory definition of a wetland pertains to sufficient soil saturation in the upper 12 inches of soil. This saturation affects soil properties as well as the types of plants that can grow, making the concept of the growing season inherent to the definition of a wetland.

Poor Timing Affects Project Schedules

The growing season is important for many project schedules. Wetland delineations must be conducted during the growing season in order to obtain accurate identification of plant species. After field work for a wetland delineation is complete, a report is then submitted to regulatory agencies. Typically, agencies request an onsite meeting to review the wetland delineation before preparing a written concurrence with the delineation. When agencies verify a delineation, the defined wetland boundaries are valid for three to five years.

If regulatory agencies cannot verify a wetland delineation before the end of the growing season, they often wait until the following spring to perform the site visit. If there is no approved wetland delineation, the project cannot determine wetland impacts and cannot obtain federal or state wetland permits.

When Does the Growing Season End?

The end of the growing season varies every year and is indicated by falling leaves and the cessation of plants blooming. Estimated dates for the end of the growing season can be approximated by knowing the date when temperatures first drop to 28 degrees Fahrenheit. In Minneapolis/St. Paul, there is a 50 percent chance that date will occur by October 17th. In spring, the Twin Cities growing season will begin again in mid-April.

The potential to complete a valid wetland delineation, and obtain agency concurrence, decreases after the growing season ends. If frost or snow makes it difficult to identify plants and accurately distinguish plant communities and wetland boundaries, all field components of a wetland project must wait for the next spring. This pause can stall a project for months, causing costly delays.

Maintaining project schedules are crucial for many sites, and with fall approaching it’s important to think about scheduling wetland delineations before it’s too late. Even if a project is still in the planning stages, a wetland delineation can be completed and approved early, before the need for wetland permitting becomes a critical path item. Download our permitting checklist that can help guide your next wetlands project. For more information, contact Daniel DeJoode, or click here to view a webinar recording on this topic.

Daniel DeJoode, Ph.D. Senior Scientist

P: 952.995.2459