SUBJECT: The U.S. Army Corps of Engineers, Sacramento District, (Corps) is evaluating a permit application to construct the Las Vegas Wash - Sloan Channel to Cedar Avenue project, which would result in impacts to approximately 4.247 acres of waters of the United States in or adjacent to the Las Vegas and Flamingo Washes. 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: Ms. Mona Stammetti, Clark County Department of Public Works, 500 Grand Central Parkway, Las Vegas, Nevada 89155-4000
LOCATION: The 4.247-acre (20,665 linear feet) project is located on the Las Vegas and Flamingo Washes through the Desert Rose Golf Course, Section 32 of Township 20 South, Range 62 East; and Sections 4, 9, and 10 of Township 21 South, Range 62 East, Mount Diablo Base and Meridian, Las Vegas, Clark County, Nevada. The northern end of the project is located at Bonanza Road. The southern end of the project is located 1,100 feet east of Sloan Lane (Figure 1).
PROJECT DESCRIPTION: The applicant is proposing to improve the flood control functions of the Las Vegas and Flamingo Washes within the existing public right-of-way. The Proposed Action also may include flood control improvements on the Flamingo Wash within the Desert Rose Gold Course. The existing right-of-way is designated as Flood Channel, Public, or Clark County Parks and Community Service lands and varies from 140 to almost 870 feet in width at the confluence of the Las Vegas Wash and Flamingo Wash. Beginning just downstream of Bonanza Road, the project would include transitioning from the existing partially improved wash section to a 90-foot wide rectangular reinforced concrete flood channel. The height of the channel walls would vary to provide for hydraulic capacity, freeboard, and to provide a bench for the existing and future trail facilities and maintenance. A concrete confluence structure would be constructed just downstream of the existing Cedar Avenue trapezoidal concrete channel. Channel lining at the Stewart Avenue Bridge would be constructed under the bridge and would not include any modifications to the bridge. The 90-foot wide rectangular channel would continue downstream to a transition just north of Charleston Boulevard. The invert of the wash would be lowered approximately 5 feet to allow for additional capacity at the Charleston Boulevard Bridge. From the Charleston Bridge, the project would transition into a 110-foot wide channel that would protect the existing 51-inch sanitary sewer that is attached to the underside of the bridge structure and eliminate overtopping of the bridge, which is a common occurrence during storm events. The 110-foot channel would continue downstream to Nellis Boulevard with a transition to an 85-foot wide rectangular reinforced concrete flood channel. Between Charleston and Nellis Boulevards, flow would be collected from two major tributary facilities; an existing reinforced concrete box at Colorado Avenue and an existing trapezoidal concrete channel along Nellis Boulevard. The Nellis Bridge would be protected through the lowering the wash channel by 12 feet below the existing elevation. The 85-foot wide channel would continue downstream to the Desert Rose Golf Course.
Between Nellis and Sloan Lane within the Desert Rose Golf Course, the golf course would be re-graded and reconfigured by lowering the elevation of the wash and surrounding area by 12 feet and increasing the cross slopes to keep flooding towards the center of the existing right-of-way. The Sahara Avenue Bridge would be replaced with a larger, 230-foot bridge and the wash would be lowered by 9 feet. Three existing golf course bridges would either be replaced or moved to span the 100-year flood channel. An existing 8-foot wide reinforced concrete low flow channel through the golf course conveys flow through the golf course. This structure would be replaced with a 20-foot wide reinforced concrete low flow channel. The flow through Flamingo Wash would also be conveyed in a reinforced concrete low flow channel through the golf course. The storm drain pipe that conveys flow through the golf course from Flamingo Wash would be removed. The Flamingo Wash invert would also be lowered up to 12 feet from South Nellis Boulevard and the confluence with Las Vegas Wash. The typical channel section for the Las Vegas and Flamingo Washes through the golf course is a 50-foot bottom width trapezoidal grass-lined channel with side slopes of 3:1 or 4:1 (horizontal:vertical) (LVMD 0912 – 1031 and FLWA 0001). The modified section through the golf course would maintain a green corridor by limiting the concrete to the low flow channel and not constructing the 75 by 100-foot rectangular concrete-lined channel that was proposed in the 2008 Master Planning Unit (MPU). Project improvements along the Flamingo Wash would also include the replacement of a72-inch sanitary sewer facility with a 104-inch facility and the addition of an 18-inch force main sanitary sewer facility. The lowered invert of the Flamingo Wash would result in the need to relocate an existing 15-inch sanitary sewer facility through the golf course to Vegas Valley Drive. The sanitary sewer manholes would be located outside of the 100-year flood limits.
The downstream portion of the project, between the confluence with the Flamingo Wash and the existing concrete-lined Sloan Channel confluence, consists of a partially improved channel section within an approximately 300-foot right-of-way that includes reinforced concrete slope lining on the north bank of the channel and areas of riprap and crushed concrete rubble protection on the channel invert and south bank. This portion of the wash would be improved and widened with a 120-foot bottom width trapezoidal reinforced concrete channel with 2:1 side slopes from the Flamingo Wash confluence to the existing trapezoidal concrete channel at the Sloan Channel confluence (LVMD 0873 – 0908).
Based on the available information, the overall project purpose is to alleviate flooding issues along Las Vegas Wash. The applicant believes there is a need to safely convey existing and future 100-year design flows through the project area, remove approximately 1,700 residents and businesses from Federal Emergency Management Agency (FEMA) designated Flood Hazard Areas, and provide erosion protection to protect existing utilities that cross and/or are located beneath the wash beds. The attached drawings provide additional project details.
Environmental Setting. The Las Vegas and Flamingo Washes were highly modified in the 1970’s and were developed primarily as flood conveyance systems in a rapidly urbanizing area. From the original ephemeral desert washes that existed prior to the 1950’s, these systems are now basically perennial drainages, driven hydrologically by urban run-off and treated water from upstream water treatment facilities. The project is situated in a predominantly residential area and includes a large section of the Desert Rose Golf Course and has been significantly altered over the past 50 years. The Las Vegas Wash is confined to a relatively narrow channel through the golf course and does not exceed 10 feet in width. The channel is much wider upstream of the golf course, in most cases averaging approximately 20 to 30 feet wide. Vegetation is limited to mainly introduced species such as bermuda grass (Cynodon dactylon) and tamarisk (Tamarix spp.), with an occasional isolated patch of narrow-leaf cattails (Typha angustifolia). These species are periodically removed through mechanical means to maintain the flow characteristics of the channel. Therefore, mature specimens do not exist within the drainage.
The project area contains approximately 6.865 acres of waters of the United States. Of these, 2.618 acres has been previously disturbed and is lined with articulated concrete blocks that failed during the past year following three large storm events in the Las Vegas Valley during the summer of 2012. The impacted area remains essentially within the same footprint and would be considered maintenance of an existing structure. The remaining 4.247 acres is an earthen channel that would be converted to concrete. There are no wetlands associated with the project area.
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.
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 proposed to mitigate on-site through the Desert Rose Golf Course.
OTHER GOVERNMENTAL AUTHORIZATIONS: Water quality certification or a waiver, as required under Section 401 of the Clean Water Act from the Nevada Department of Environmental Protection is required for this project. The applicant has not indicated whether the County has applied for certification.
HISTORIC PROPERTIES: Based on the available information, no cultural resources were identified within the project's area of potential effect. 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 project will not affect any Federally-listed threatened or endangered species or their critical habitat that are protected by the Endangered Species Act. 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-2012-01327-SG must be submitted to the office listed below on or before August 19, 2013.
Patricia McQueary, Project Manager
US Army Corps of Engineers, Sacramento District
196 East Tabernacle Street, Room 30
St. George, Utah 84770
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, telephone 435-986-3979, or email Patricia.L.McQueary@usace.army.mil.
Attachments: 5 drawings