2018-14187. Notice of Availability of the Draft Feasibility Report and Integrated Environmental Impact Statement for the Adams and Denver Counties, Colorado General Investigation Study, Adams and Denver County, Colorado

AGENCY:

Department of the Army, U.S. Army Corps of Engineers, DoD.

ACTION:

Notice.

SUMMARY:

The U.S. Army Corps of Engineers (Corps) has made available for public review and comment the Adams and Denver Counties, Colorado General Investigation Study Draft Feasibility Report and Integrated Environmental Impact Statement (Draft EIS). The Draft EIS analyzes and discloses potential effects associated with the proposed Federal action to restore aquatic, wetland, and riparian habitat along the South Platte River and implement flood risk management solutions along Weir Gulch and Harvard Gulch.

DATES:

The public comment period on the Draft EIS begins on July 2, 2018 and will last 45 days. Submit written comments on the Draft EIS on or before August 16, 2018. Three public meetings to share information and for the public to provide oral or written comments will be held for specific study segments at the following locations:

• Weir Gulch: Tuesday, July 31, 2018, 5:30 p.m. to 7:30 p.m. at Barnum Recreation Center, 360 Hooker Street, Denver, CO 80219.
• South Platte River: Wednesday, August 1, 2018, 5:30 p.m. to 7:30 p.m. at REI, 1416 Platte Street, 3rd Floor, Denver, CO 80202.
• Harvard Gulch: Thursday, August 2, 2018, 5:30 p.m. to 7:30 p.m. at Porter Hospital, 2525 S Downing Street, Grand Mesa Conference Room (2nd Floor), Denver, CO 80210.

The parking garage is available and access is through the main hospital entrance. Each meeting will begin with an open house at 5:30 p.m. followed by a formal 30-minute presentation at 6:00 p.m., with the rest of the meeting consisting of an open house until 7:30 p.m.

ADDRESSES:

Send written comments, requests to be added to the mailing list, or requests for sign language interpretation for the hearing impaired or other special assistance needs to U.S. Army Corps of Engineers Omaha District, ATTN: CENWO-PMA-A, 1616 Capitol Ave., Omaha, NE 68102; or email to [e-mail].

FOR FURTHER INFORMATION CONTACT:

Mr. Jeffrey Bohlken, U.S. Army Corps of Engineers, 1616 Capitol Ave., Omaha, NE 68102, or [e-mail].

SUPPLEMENTARY INFORMATION:

The Corps is issuing this notice pursuant to section 102(2)(c) of the National Environmental Policy Act of 1969 (NEPA), as amended, 42 U.S.C. 4321 et seq.; the Council on Environmental Quality's (CEQ) regulations for implementing the procedural provisions of NEPA, 43 CFR parts 1500 through 1508; the Department of the Interior's NEPA regulations, 43 CFR part 46.

Background Information. The Adams and Denver Counties, Colorado General Investigation Study is located in eastern Colorado in Adams and Denver Counties. The study area includes three streams—the South Platte River, Weir Gulch, and Harvard Gulch. The Weir and Harvard Gulches are tributaries to the South Platte River. Stream-specific project areas were established for each stream and are as follows:

• South Platte River—6th Ave to 58th Ave.
• Harvard Gulch—Colorado Blvd. to the confluence
• Weir Gulch—Just west of Sheridan Blvd. to the confluence, including 1st Ave. and Dakota Ave. Tributaries

Original authority for the Adams County, Colorado study was expanded by a resolution adopted 24 September, 2008, by the Committee on Transportation and Infrastructure, U.S. House of Representatives, Docket 2813, Adams and Denver Counties, Colorado, directing the USACE to conduct a study on flood damage reduction, floodplain management, water supply, water quality improvement, recreation, environmental restoration, watershed management, and other allied purposes along the South Platte River and its tributaries in Adams and Denver Counties, Colorado. Additional study guidelines were provided by the USACE Northwestern Division, ensuring that the Omaha District developed measures that focus on environmental restoration (e.g., migratory bird habitat, wetlands, etc.) rather than primarily targeting improvement of aesthetic features.

This notice announces the availability of the Draft EIS and begins a 45-day public comment period on the range of alternatives and effects analysis. Analysis in the Draft EIS will support a decision on the selection of an alternative. The Draft EIS can be accessed at: http://www.nwo.usace.army.mil/​Missions/​Civil-Works/​Planning/​Project-Reports/​. The Corps is serving as the lead Federal agency for the NEPA analysis process and preparation of the Draft EIS. No Cooperating Agencies were established for this study.

Project Alternatives. The purpose of the Adams and Denver Counties, Colorado General Investigation Study is to restore aquatic, wetland, and riparian habitat along the South Platte River. Along Weir and Harvard Gulches, the purpose of the study is to implement flood risk management improvements. The Draft EIS analyzes 10 alternatives which includes a No Action Alternative for each stream.

South Platte River Alternative 1. The South Platte River No Action Alternative (NAA) would involve continued ongoing operation and maintenance of existing flood risk management features, operation and maintenance of constructed habitat restoration projects, and associated activities to comply with state and Federal law. Some actions expected to be taken under the no action alternative would include the redevelopment of the National Western Center (including some ecosystem restoration features along the east bank of the South Platte River and floodplain), relocation of sewage lines along the east bank, minor ongoing invasive species removal efforts, and ongoing water quality improvement efforts. Several ongoing master planning efforts and their proposed activities would also be expected to continue. Large-scale ecosystem restoration construction would not be expected to be implemented.

South Platte River Alternative 2. The South Platte River ecosystem restoration Plan 9 alternative would involve extensive aquatic, wetland, riparian, and some upland buffer habitat restoration and would incorporate some incidental flood risk management improvements. The footprint of this alternative spans approximately 150 acres of floodplain and approximately 95 acres in-channel. Restoration activities include dredging and removal of accreted sediment, removal and modification of multiple in-channel drop structures, regrading of floodplain banks, installation of rock jetties, construction of wetland benches, removal of invasive species vegetation, and revegetation of all disturbed land with native species. The project would result in the restoration of 85 acres of riparian habitat, 43 acres of wetland habitat, 95 acres of aquatic habitat, and the removal and replacement of 24 acres of additional invasive species vegetation with native riparian species. In addition, construction of the recommended plan would reconnect approximately 190 acres of existing riparian areas, ponds, parks, and other “green” areas in the urban landscape. These habitat areas would directly support breeding migratory birds and could serve as valuable corridors for native wildlife utilizing this area. In total, almost 450 acres of habitat would see direct and indirect improvement from this project. Infrastructure improvements conducted under this alternative would include realignment of a portion of sanitary sewer lines and the Burlington Canal; replacement of the Confluence Park diversion structure with flashboards; relocation of a pedestrian bridge; and relocation of all impacted recreational trails.

Weir Gulch Alternative 1. The Weir Gulch NAA would involve Urban Drainage & Flood Control District (UDFCD) and City and County of Denver (CCD) ongoing operation and maintenance of constructed flood risk management features along the Weir Gulch. Ongoing minor invasive species management and water quality improvements would be expected to continue, but construction of habitat restoration or additional flood risk management features would not be expected to occur.

Weir Gulch Alternative 2. The Weir Gulch flood risk management channel alternative would involve increasing conveyance through the project area by widening the channel in reaches 1 through 3 with a culvert expansion in reach 6. The channel widening in reaches 1 through 3 would involve maintaining the approximately 1-foot wide daily flow channel, excavating a low flow channel and re-grading the upper channel sides to a 3H:1V slope. The flood control channel would consist generally of a trapezoidal low-flow channel designed to convey approximately 70% of the 50% annual chance exceedance (ACE) flood event (2-year return interval flood), per UDFCD guidelines. The overall channel width varies by location and reach, but in general top of channel widths averages 100 feet. Native species vegetation plantings would also be incorporated into this alternative to restore some riparian vegetation along the channel banks as well as to restore wetland benches within the daily flow channel.

Weir Gulch Alternative 3. The Weir Gulch nonstructural flood risk management alternative includes such nonstructural measures as elevation, buyouts, relocations, wet floodproofing, dry floodproofing, etc. Incremental nonstructural measures were added to reaches 4, 5, and 7. There were only five structures with an individual benefit-cost ratio (BCR) over 1.0 in reaches these reaches, therefore to include as many structures as possible, structures with an individual BCR above 0.5 were included. A total of 13 structures were identified as part of the nonstructural alternative.

Weir Gulch Alternative 4. The Weir Gulch flood channel and nonstructural flood risk management combination alternative combines the measures and properties considered in alternatives 2 and 3 into a single alternative by looking at how isolated nonstructural measures could be used to further reduce the existing flood risk and thus generate higher flood risk reduction benefits.

Harvard Alternative 1. The Harvard Gulch NAA would involve the UDFCD and CCD ongoing operation and maintenance of constructed flood risk management features along the Harvard Gulch. Harvard Gulch Park would continue to be maintained for its current mixed use recreational purposes. Ongoing minor invasive species management and water quality improvements would be expected to continue, but construction of habitat restoration or additional flood risk management features would not be expected to occur.

Harvard Gulch Alternative 2. The Harvard Gulch flood channel alternative would involve increasing conveyance through the project area by widening the channel in reaches 2 through 5 with a culvert expansion in reach 1. The channel widening in reaches 2 through 5 would involve maintaining the approximately 1-foot wide daily flow channel, excavating a low flow channel and re-grading the upper channel sides to a 3H:1V slope. The flood control channel would consist generally of a trapezoidal low-flow channel designed to convey approximately 70% of the 50% ACE (2-year return interval flood), per UDFCD guidelines. The overall channel width varies by location and reach, but in general top of channel widths average 80 feet. Native species vegetation plantings would also be incorporated into this alternative to restore some riparian vegetation along the channel banks and restore wetland benches within the daily flow channel.

Harvard Gulch Alternative 3. The Harvard Gulch nonstructural flood risk management alternative includes structures in all reaches with an individual BCR above 1.0 and 10 buyouts located in the floodway in reach 4. The 10 residential buyouts in the floodway were selected based on flood damages beginning at the 10% ACE (10-year return interval flood) and inundation depths around 3 feet during the 1% ACE (100-year return interval flood). Of the structures meeting this criteria, the 10 closest to the channel were selected. This selection criteria also aligns with the non-Federal sponsor's Harvard Gulch Major Drainageway Plan. The nonstructural measures for the 96 structures in this alternative include elevation, basement fill, dry floodproofing, and buyouts.

Harvard Gulch Alternative 4. The Harvard Gulch flood channel and nonstructural flood risk management combination alternative combines the measures and properties considered in alternatives 2 and 3 into a single alternative by looking at how isolated nonstructural measures could be used to further reduce the existing flood risk and thus generate higher flood risk reduction benefits.

The Draft EIS evaluates the potential effects on the human environmental associated with each of the alternatives. Issues addressed include: Land use and vegetation, social and economic conditions, recreation, water resources, climate change, biological resources, cultural resources, geomorphology, preexisting contamination, utilities and infrastructure, air quality, noise, and environmental justice.

Schedule. A 45-day public comment period will begin July 2, 2018. Comments on the Draft EIS must be received by August 16, 2018. The Corps will consider and respond to all comments received on the Draft EIS when preparing the Final EIS. The Corps expects to issue the Final EIS in the spring of 2019, at which time a Notice of Availability will be published in the Federal Register.

The public meeting date or location may change based on inclement weather or exceptional circumstances. If the meeting date or location is changed, the Corps will issue a press release and post it on the web at http://www.nwo.usace.army.mil/​Media/​News-Releases/​ to announce the updated meeting details.

Special Assistance for Public Meeting. The meeting facility is physically accessible to people with disabilities. People needing special assistance to attend and/or participate in the meeting should contact: U.S. Army Corps of Engineers Omaha District, ATTN: CENWO-PMA-A, 1616 Capitol Ave., Omaha, NE 68102; or email to [e-mail]. To allow sufficient time to process special requests, please contact no later than one week before the public meeting.

Public Disclosure Statement. If you wish to comment, you may mail or email your comments as indicated under the ADDRESSES section of this notice. Before including your address, phone number, email address, or any other personal identifying information in your comment, you should be aware that your entire comment—including your personal identifying information—may be made available to the public at any time. While you can request in your comment for us to withhold your personal identifying information from public review, we cannot guarantee that we will be able to do so.

Dated: June 25, 2018.

Eric Laux,

Chief, Environmental and Cultural Resources Section.