- Platte West Water Production Facilities
Burns & McDonnell was the third-party consultant for the preparation of an Environmental Impact Statement (EIS) for the Metropolitan Utilities District's (District) Platte West Water Production Facilities in Omaha, Neb. The district prepared the EIS to obtain a Section 404 Permit from the U.S. Army Corps of Engineers, Omaha District, for construction. Project facilities include two new groundwater well fields, a new water treatment plant, water transmission pipelines and other appurtenant facilities. The two well fields, located west of Omaha in Saunders and Douglas counties, will provide water to be used by rapidly developing western suburbs. The corps permit was issued on May 16, 2003.
Burns & McDonnell is also the wetland consultant for the district. As part of the EIS for the well field alternative sites, Burns & McDonnell's wetland staff conducted field surveys and analyses to determine existing conditions, including:
- Verified an existing wetland survey in the proposed well fields.
- Identified and mapped all wetland types and determined acreages in a two-mile radius around the proposed well fields.
- Prepared a functions and values analysis on the major classes of wetlands found in the study area using WET 2 methodology.
- Prepared a wetland impact analysis for the proposed 2,230-acre well fields and adjacent areas (cones of depression) potentially impacted by lowering the water table and by flow depletions in the Platte River.
- National Environmental Policy Act (NEPA) services and environmental planning
- Environmental studies and impact analysis
- Public involvement, scoping and hearings
- Agency coordination
- Wetland mapping and delineation
- Environmental Impact Statement
- Wetland mitigation plan
- Wetland monitoring
- Bathymetric mapping and monitoring
- Environmental permitting
- Hydrogeologic modeling
- Mitigation site selection
- Mitigation site planning and engineering design
- Mitigation site construction contracting and management services
- Construction inspection management and services
Burns & McDonnell's wetland staff performed several wetland delineations according to the guidelines of the Corps 1987 Wetlands Delineation Manual, Corps guidance, concerning jurisdictionality of watercourses and isolated wetlands, and the National Food Security Act Manual for cropland. As directed by the conditions included in the Corps Individual Section 404 Permit, these wetland delineations included:
- Douglas County and Saunders County Well Fields (2,230 acres) — The two well fields were surveyed for wetlands and mapped using global positioning satellite (GPS) technology. Over 263 wetlands, ponds and streams were delineated during the effort. These jurisdictional wetland areas cover approximately 174.3 acres of land.
- Douglas County and Saunders County Cones of Depression (13,800 acres) — Privately owned property was delineated where access was obtained from individual landowners. Nearly 155 acres of jurisdictional waters, including wetlands, were delineated within the two proposed cones of depression.
- Water Treatment Plant Site (160 acres) — Approximately 2.6 acres of wetland and 38 feet of ephemeral stream were delineated at the new water treatment plant site.
- Raw Water Transmission Pipeline (3.5-mile right-of-way) — Approximately 0.9 acre of wetland and 3,400 feet of stream channel were delineated within the raw water transmission pipeline connecting the Douglas County well field to the new Water Treatment Plant.
- Finished Water Transmission Pipeline (1.8-mile right-of-way) — Approximately 0.7 acre of wetland and 641 feet of stream channel were delineated within the finished water transmission pipeline connecting the new Water Treatment Facility to Skyline Reservoir.
- La Platte Mitigation Site (161 acres) — Approximately 13.6 acres of wetlands were delineated at the proposed mitigation site.
Conditions in the Corps Individual Section 404 Permit also stipulated that up to 30 years of wetland monitoring may be needed for the two well fields and cones of depression in Douglas County and Saunders County. Monitoring is designed to determine if project operation adversely affects wetlands through the drawdown of the existing groundwater table. Wetlands in the 2,230-acre well fields are being monitored using piezometers, false-color infrared aerial photography, and extensive vegetative sampling. Wetlands in the 13,800-acre cones of depression are being monitored using false-color infrared aerial photography since these lands are outside the two well fields and the district does not have permanent access. Bathymetric mapping and monitoring of water levels in ponds that may be influenced by Project operation is also requested by conditions in the Corps Section 404 Individual Permit to the District.
Mitigation for impacts to wetlands and streams occurring during construction and operation is a condition of the Corps Individual Section 404 Permit. A Mitigation Site Selection Study has been prepared to evaluate and rank sixteen different potential mitigation sites. Mitigation measures will take place in three phases to address impacts before they occur. Each mitigation site will be monitored for up to five years to evaluate that success criteria are met.
- A Phase I Mitigation Plan was developed to address wetland impacts resulting from (1) the construction of facilities in the two well fields and raw water transmission pipelines, and (2) the construction of a new Water Treatment Plant. The Phase I Mitigation Plan was designed to compensate for the construction impact to (1) 0.2 acres of emergent wetland through the creation of 0.3 acres or more of emergent wetland and (2) 2.9 acres of emergent wetland and 38 feet of stream channel through the creation of 4.35 acres of emergent wetland and 38-feet of stream channel divided among 8 sites.
- A Phase II Mitigation Plan is being developed to address impacts to wetlands in the two well fields that may occur due to the localized drawdown of the water table. Partnerships with local agencies such as Omaha's Henry Doorly Zoo and the Lower Platte Natural Resource District for mitigation are in-place or being developed and information on existing conditions is now being collected to facilitate Phase II mitigation efforts.
- A Phase III Mitigation Plan will be prepared to address impacts to wetlands on privately-owned property adjacent to the two well fields in the cones of depression that may occur due to the localized drawdown of the water table. A Phase III site will be selected from the Site Selection Study when Phase II Mitigation is in place and once any impacts that may occur are confirmed.