In April 2023, a wetland survey was conducted for a 3-acre project area in the town of Wyanet, found in lovely Bureau County, Illinois, intended for cell tower construction. The land use at the time was grazing pasture with a pond and drainage ditch, a wooded area to the east, and a naturalized area to the north. The client requested the survey to determine the location and size of wetlands associated with the project.
Wetland Survey Project
The wetland survey followed the technical guidelines as described in the Army Corps of Engineers Wetland Survey Manual and the Regional Supplement to the Corps of Engineers Wetland Survey Manual: Midwest Region. The process included off-site procedures and a field investigation. Off-site review analyzed maps, aerial photography, precipitation data, and wetness signatures, while field investigation took place on April 6th, 2023, examining the site for changes affecting vegetation, soils, and hydrology.
Desktop analysis assessed features in the project boundary, determining potential wetland areas using historical aerial imagery, topographical features, hillshade elevation map, wetland features identified by the USFWS National Wetland Inventory, flood hazard risk from FEMA, and hydric soils from Web Soil Survey. The area was undeveloped open space in 1941, and currently consists of roadside swales, grazing pasture, a pond, a drainage ditch, wooded areas, and naturalized vegetation.
The topographic map and aerial imagery were most helpful in identifying suspected wetland areas, while the remaining maps did not give strong indications. The pond, drainage ditch, and their surrounding areas were suspected to be wetlands, while the areas at the highest elevations were suspected to be uplands. The climate in the three-month window before the investigation was normal, with 1.26 inches of rain over the seven days prior to the survey.
Overall, the study helps to identify and map wetlands based on specific criteria, such as soil types, vegetation, and hydrology. This information is crucial for the regulatory decisions and final determinations made by the U.S. Army Corps of Engineers in relation to the cell tower installation project.
Wetland Survey Findings
Wetland A, located mostly outside the project footprint, consisted of two lobes with differing elevations and indicators. The west lobe included the pond, drainage ditch, and surrounding wet areas, while the east lobe comprised grazing pasture up the slope. These lobes connected further downstream where surface water lay.
The soils in the west lobe were mineral soils characterized by Redox Dark Surface, while the east lobe had mineral soils characterized by Depleted Matrix , Redox Dark Surface , and Depleted Below Dark Surface. Hydrology within both lobes was characterized by Surface Water, High Water Table, and Saturation, with additional secondary indicators in the west lobe.
Dominant plant species in the west lobe were common duckweed (Lemna minor) and jewelweed (Impatiens capensis), while the east lobe was dominated by river bulrush (Scirpus atrovirens) and smooth brome (Bromus inermis). The upland area featured various species including smooth brome and common dandelion (Taraxacum officinale).
The Floristic Quality Assessment results showed one wetland on-site with 10 species found, 50% of which were native.