Sacramento District
Comments Period: November 24, 2014 – December 29, 2014
SUBJECT: The U.S. Army Corps of Engineers, Sacramento District, (Corps) is evaluating a permit application to construct the Beaver Dam Resort - Flood Damage project, which would result in impacts to approximately 5.2 acres of waters of the United States, including wetlands, in or adjacent to Beaver Dam Wash. This notice is to inform interested parties of the proposed activity and to solicit comments.
AUTHORITY: This application is being evaluated under Section 404 of the Clean Water Act for the discharge of dredged or fill material in waters of the United States.
APPLICANT: Mohave County Flood District, P.O. Box 7000, 3250 E. Kino Avenue, Kingman, AZ 86402-7000
LOCATION: The 5.2-acre site is located on the Beaver Dam Wash, Section 4, Township 40 North, Range 15 West, Gila and Salt River Meridian, Latitude 36.89495°, Longitude -113.927480°, Beaver Dam, Mohave County, Arizona, and can be seen on the AZ-LITTLEFIELD USGS Topographic Quadrangle.
PROJECT DESCRIPTION: The applicant is proposing to construct a low flow channel in order to move the current low-flow channel alignment away from the Beaver Dam Estates and Beaver Dam Resort located south of the wash and back to its historical alignment (Project 1). To protect the residential areas, a new low-flow channel totaling approximately 3,300 linear feet in length would be established beginning near the County Highway 91 Bridge and continuing downstream beyond the Beaver Dam Resort. The re-established low-flow channel would have a 20-foot-wide bottom and would be approximately 1 to 2 feet deep. The channel sides would be constructed with an approximate 2:1 side slope, making the low-flow channel approximately 28 feet wide horizontally. The re-established low-flow channel would be connected to the existing low-flow channel location at the upstream end near the County Highway 91 Bridge and at the downstream beyond the Beaver Dam Resort by excavating a channel to connect the channel segments. An 80-foot-wide permanent easement would be established along the low-flow channel alignment. The entire easement, including the low-flow channel, would be cleared of vegetation during construction and again every 6 to 12 months, or as needed, to ensure access and flows within the channel are maintained. If necessary following a flow event, the proposed low-flow channel would be re-established along the proposed alignment and configuration within the permanent easement. The applicant anticipates completing the re-establishment of the low-flow channel primarily through excavation practices. Excavated material would be removed with conventional earthmoving equipment and would either be deposited in approved upland areas outside the jurisdictional limits of Beaver Dam Wash and/or in waiting material hauling vehicles.
The backfilling of the existing low-flow channel is not anticipated to occur for the establishment of the low-flow channel. However, in limited instances fill material would need to be placed within waters for the purpose of diverting flows into the new low-flow channel.
In addition to the low-flow channel, the applicant has proposed to install bank protection along 165 feet between the County Highway 91 Bridge guide banks and the existing revetments along Beaver Dam Estates (Project 2). Stabilization of this gap is recommended and considered critical to avoid flanking of existing revetment. After the December 2010 flood event, the gap was filled with an earthen embankment and lined with a riprap mattress, presumably by an owner at the Beaver Dam Estates. Under this project, the Applicant would inspect the existing riprap mattress to ensure that a 3-foot-thick layer is in place, augment as needed, and supplement with a 10-foot-deep by 10-foot-wide launchable trench filled with wire-tied 15-inch D50 riprap, for the length of the gap.
The Applicant is also proposing to strengthen the bank and prevent further lateral migration of the bank into the homes located within the Beaver Dam Resort. The homes are currently located in the 100-year floodplain (see Figure 4) and no levee system exists to contain large flood events. The project would consist of constructing 1,200 feet of bank protection along Beaver Dam Resort, which would help prevent the continued lateral migration. The proposed location and alignment of the bank protection is consistent with what was considered the southern bank and immediately adjacent upland areas along Beaver Dam Wash prior to the December 2010 flood event. To strengthen the embankment, a 3-foot-wide wire tied rip rap revetment would be installed at a depth of 10 feet using 15-inch D50 material. Construction access to the work area would be achieved via the Beaver Dam Resort.
The bank protection (Project 3) at this location would be constructed in 20-foot segments to minimize impacts of pumped dewatering of the channel, similar to Project 2. An approximately 25-foot diameter, 2-foot-deep temporary stilling basin would be constructed adjacent to the bank protection structure. It is anticipated that the bank protection structure would be built in 20-foot-long sections and each section could require 50 gpm of pumping to keep it dry during construction. The dimensions of the basin are based on the assumption that approximately 10 minutes of settling time would be necessary. The stilling basin would allow the reduction of turbid conditions of the water prior to it being discharged downstream. At the point of discharge, riprap would be used to minimize the potential for nuisance conditions to occur, such as erosion. The location of the stilling basin would be backfilled upon completion of the new structure.
The Corps has determined that the gap protection (Project 2) and bank stabilization (Project 3) along the Beaver Dam Estates and Resort can be permitted under a Nationwide 45 for Repair of Uplands Damaged by Discrete Events.
Based on the available information, the overall project purpose is for flood control along the Beaver Dam Wash. The applicant believes there is a need to protect public infrastructure and private property from flood damage. The attached drawings provide additional project details.
ADDITIONAL INFORMATION:
Environmental Setting. There are approximately 5.2 acres of “Waters of the U.S.” within the project area. The lower Beaver Dam Wash has been subjected to numerous large flood events in the past 10 years. The most recent, on September 27, 2014, created further damage and scoured out the old channel by about 5-feet in depth. Most of the herbaceous and shrub vegetation was scoured out, leaving debris and rubble behind. The project is located at the boundary of the Basin and Range and Colorado Plateau physiographic provinces in northwestern Arizona. The Beaver Dam Mountains are located to the north, while the Virgin Mountains and the Paiute Wilderness Area are located to the south, just upstream of the confluence of Beaver Dam Wash and the Virgin River. The Beaver Dam Wash is one of the Virgin River’s largest tributary and has about one-mile of perennial stream from the confluence with the Virgin River, upstream through the proposed project area.
Riparian communities support deep-rooted trees such as Fremont cottonwood (Populus fremontii), velvet mesquite (Prosopis velutina), introduced tamarisk (Tamarix spp.), a large variety of grasses, grass-like plants and herbaceous plants like bulrush (Scirpus spp.) and spike-rush (Eleocharis spp.). Since the September 2014 flood event, the community is now at an early stage of development.
Alternatives. The applicant has provided information concerning project alternatives. Additional information concerning project alternatives may be available from the applicant or their agent. Other alternatives may develop during the review process for this permit application. All reasonable project alternatives, in particular those which may be less damaging to the aquatic environment, will be considered.
The Applicant provided information on the following alternatives
1. No Action alternative: There would be no permit issued and the current conditions would continue. Future storm events could cause additional erosion to the wash and flood adjacent residential properties and potentially damage public infrastructure.
2. Alternative 1: 20-Foot-Wide Low Flow Channel (Applicant-preferred)
3. Alternative 2: 40-Foot-Wide Low Flow Channel: Similar to the preferred alternative but the width of the low flow channel would be 40 feet and the permanent easement would be 100-feet wide, increasing the impacts to “waters of the U.S.”
4. Alternative 3: 150-Foot-Wide Low Flow Channel: The re-established low-flow channel would have a 150-foot-wide bottom and would be approximately 1 to 2 feet deep. The channel sides would be constructed with an approximate 2:1 side slope, making the low-flow channel approximately 165 feet wide horizontally. A 210-foot-wide permanent easement would be established along the low-flow channel alignment and would be used for access during construction.
5. Alternative 4: Short Low-Flow Channel Option: A new low-flow channel totaling approximately 1,400 linear feet in length would be established beginning at the Golf Cart Bridge and continuing downstream beyond the Beaver Dam Resort. The re-established low-flow channel would have a 20-foot-wide bottom and would be approximately 1 to 2 feet deep. The channel sides would be constructed with an approximate 2:1 side slope, making the low-flow channel approximately 28 feet wide horizontally. An 80-foot-wide permanent easement would be established along the low-flow channel alignment and would be used for access during construction.
Mitigation. The Corps requires that applicants consider and use all reasonable and practical measures to avoid and minimize impacts to aquatic resources. If the applicant is unable to avoid or minimize all impacts, the Corps may require compensatory mitigation. The applicant has not provided any additional information on mitigation alternatives.
OTHER GOVERNMENTAL AUTHORIZATIONS: Water quality certification or a waiver, as required under Section 401 of the Clean Water Act from the Arizona Department of Environmental Quality is not required for this project. The applicant has indicated they have applied for certification.
HISTORIC PROPERTIES: Based on the available information, (including applicant's report entitled “A Class III Cultural Resources Survey of 8.57 Acres of Beaver Dam Wash within the Community of Beaver Dam, Mohave County, Arizona,” potentially eligible cultural resources may be affected by the proposed project. The Corps will initiate consultation with the State Historic Preservation Officer under Section 106 of the National Historic Preservation Act, as appropriate.
ENDANGERED SPECIES: The proposed activity may affect Federally-listed endangered or threatened species or their critical habitat. The Corps will initiate consultation with the U.S. Fish and Wildlife Service, pursuant to Section 7 of the Endangered Species Act, as appropriate.
The above determinations are based on information provided by the applicant and our preliminary review.
EVALUATION FACTORS: The decision whether to issue a permit will be based on an evaluation of the probable impacts, including cumulative impacts, of the described activity on the public interest. That decision will reflect the national concern for both protection and utilization of important resources. The benefit, which reasonably may be expected to accrue from the described activity, must be balanced against its reasonably foreseeable detriments. All factors which may be relevant to the described activity will be considered, including the cumulative effects thereof; among those are conservation, economics, aesthetics, general environmental concerns, wetlands, historic properties, fish and wildlife values, flood hazards, floodplain values, land use, navigation, shoreline erosion and accretion, recreation, water supply and conservation, water quality, energy needs, safety, food and fiber production, mineral needs, consideration of property ownership and, in general, the needs and welfare of the people. The activity's impact on the public interest will include application of the Section 404(b)(1) guidelines promulgated by the Administrator, Environmental Protection Agency (40 CFR Part 230).
The Corps is soliciting comments from the public, Federal, State, and local agencies and officials, Indian tribes, and other interested parties in order to consider and evaluate the impacts of this proposed activity. Any comments received will be considered by the Corps to determine whether to issue, modify, condition, or deny a permit for this proposal. To make this decision, comments are used to assess impacts on endangered species, historic properties, water quality, general environmental effects, and other public interest factors listed above. Comments are used in the preparation of an Environmental Assessment and/or an Environmental Impact Statement pursuant to the National Environmental Policy Act. Comments are also used to determine the need for a public hearing and to determine the overall public interest of the proposed activity.
SUBMITTING COMMENTS: Written comments, referencing Public Notice SPK-2012-00370-SG must be submitted to the office listed below on or before December 29, 2014.
Patricia Mcqueary, Project Manager
US Army Corps of Engineers, Sacramento District
St. George Field Office
196 East Tabernacle Street Room 30
St. George, Utah 84770
Email: Patricia.L.McQueary@usace.army.mil
The Corps is particularly interested in receiving comments related to the proposal's probable impacts on the affected aquatic environment and the secondary and cumulative effects. Anyone may request, in writing, that a public hearing be held to consider this application. Requests shall specifically state, with particularity, the reason(s) for holding a public hearing. If the Corps determines that the information received in response to this notice is inadequate for thorough evaluation, a public hearing may be warranted. If a public hearing is warranted, interested parties will be notified of the time, date, and location. Please note that all comment letters received are subject to release to the public through the Freedom of Information Act. If you have questions or need additional information please contact the applicant or the Corps' project manager Patricia McQueary, 435-986-3979, Patricia.L.McQueary@usace.army.mil.
Attachments: 9 drawings