The U.S. Army Corps of Engineers and the Diversion Authority will begin conducting field surveys along the project’s Southern Alignment (between the Diversion Inlet Structure and the Red River Control Structure and including the embankment to the east into Minnesota and the Overflow Embankment located adjacent to Cass County highway 17) as was done for other areas of the project. Required field surveys include land surveys, cultural, hazardous toxic radioactive waste (HTRW), and geotechnical borings.
Many of the surveys will require limited access to properties located on or adjacent to the Southern Alignment. The Diversion Authority will be sending letters to the property owners to request access.
A brief description of the required surveys is as follows:
1 ) Land and Hydrographic Surveys: The existing condition land and hydrographic surveys are going to be completed in areas where aerial LiDAR data does not generate an accurate depiction of the existing ground surface or river bottom (i.e. densely vegetated areas).
2) Phase 1 Cultural Resources Surveys: Archaeologists walk over the area to look for archeological sites visible on the ground surface and may hand dig small shovel tests approximately 1 foot in diameter and up to 3 feet deep to check for archeological sites below the surface or to determine the depth of sites located on the surface. Near rivers or old oxbows, a Bobcat-sized GeoProbe tracked vehicle will be used for soil coring to determine if there is potential for more deeply buried archeological sites (2-inch diameter core to 10 feet depth). All soil removed from each shovel test or soil core is screened through ¼-inch wire screen to recover any artifacts present. After screening, the soil is replaced in the shovel test or soil core hole; bentonite is used if a soil core hole cannot be filled with the natural soil. No cores are taken from the field. Artifacts encountered are analyzed and left where found; they are not collected. Standing structures are recorded by a separate field crew.
3) Hazardous, Toxic, Radiological Waste (HTRW) Phase 1 Environmental Site Assessment (ESA): A Phase 1 ESA is a report prepared for a real estate holding which identifies potential or existing environmental contamination liabilities. The analysis, often called an ESA, typically addresses both the underlying land as well as physical improvements to the property. The Contractor needs access to any parcels in order to visually inspect for signs of environmental contamination. Visual inspections, in conjunction with historical data searches and personal interviews with property owners, form the basis for any recommendation for future, more intrusive investigations (Phase 2 ESA’s).
4) Geotechnical Investigation: The exploration is conducted to determine the localized geology and ground water table in the area. Typically the exploration is completed using a drill rig mounted on a truck or on an all-terrain vehicle (i.e. balloon tire or track) and requires the drill rig to be driven to the location of the soil boring along with support vehicles (i.e. pickup trucks) which carry supplies and personnel. The soil boring is usually completed within a day or two from the start time. At the soil exploration location, multiple borings may be drilled: one to determine the water level; one to collect soil samples that are visual classified and tested to determine physical parameters and geologic formations. The soil boring(s) is backfilled once the boring is completed and then drill rig and support vehicles are removed from the site. After this, the area can be used as it was previously.
These surveys are scheduled to begin in the fall of 2014 and extend into 2016.