SUBJECT: The U.S. Army Corps of Engineers, Sacramento District, (Corps) is evaluating a permit application to construct the a spur dike within the Lower Las Vegas Wash, which would result in impacts to approximately 4.0 acres of waters of the United States, including wetlands. 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: Mr. Edward Martinez, Central Federal Lands Highway Division, Federal Highway Administration, 12300 West Dakota Avenue, Lakewood, Colorado 80228-2583
AGENT: Thomas W. Parker, Contractor , FHWA-CFLHD, Thomas.email@example.com
LOCATION: The 10.88-acre site is located on the Lower Las Vegas Wash, in Section 13, Township 21 South, Range 63 East, Mount Diablo Meridian, Latitude 36.1246672254423°, Longitude -114.897051908425°, just below the Northshore Road Bridge, Clark County, Nevada, and can be seen on the NV-FRENCHMAN MOUNTAIN USGS Topographic Quadrangle.
PROJECT DESCRIPTION: The Central Federal Lands Highway Division of the Federal Highway Administration (FHWA) , in cooperation with the National Park Service (NPS) Lake Mead National Recreation Area, is proposing to construct a fourth riprap grade control structure in the Lower Las Vegas Wash, approximately 1,000 feet downstream of an existing grade control structure. Grade control structure 4 would consist of a sloping riprap structure bounded by sheet pile cut-off walls, consistent with similar structures which have been successfully used upstream. Construction of grade control structure 4 would result in permanent impacts to 3 acres of waters of the United States, including wetlands, and temporary impacts to 1 acre of waters through the discharge of earthen material, sheet piles, concrete, riprap, and granular rock. Based on the available information, the overall project purpose is to prevent further scouring and erosion that is currently creating a threat to the stability of the bridge that crosses over Las Vegas Wash on Northshore Road. Northshore Road, also known as State Route 147, crosses over Las Vegas Wash near the northern edge of the Lake Mead Recreation Area. In 2002, three grade control structures were constructed in the Wash within the park boundary to slow the flow of the Wash and dissipate some of the erosive energy. Continued high flows as well as the rapid and significant drawdown of Lake Mead have exacerbated the problem, and the three grade control structures are no longer sufficient. Repairs were made to the structure farthest downstream to protect it from further undermining. Failure of this structure would eventually cause failure to the two upstream structures, posing a threat to the foundation of the bridge and eventually to the Lake Las Vegas Dam and outlet works. The applicant believes there is a need to stabilize the lower wash to protect the North Shore Road Bridge, protect the integrity of the three existing grade control structures, and to reduce sedimentation. The sediment generated by erosion is deposited in Lake Mead at Las Vegas Bay, compromising water quality. The attached drawings provide additional project details.
Environmental Setting. There are approximately 9.75 acres of waters of the United States within the project area, including approximately 2.21 acres of palustrine scrub shrub wetlands. The site is characterized by a perennial stream system with a narrow riparian wetland community. The highly erosive nature of the system and increased stream flow has resulted in continued incising of the channel. This has resulted in wetlands being cut-off hydrologically from the Lower Las Vegas Wash. The predominant vegetation is the non-native tamarisk (Tamarix ramosissima), which creates a monoculture with little diversity in stand structure. The proposed project is located within the Lake Mead National Recreation Area.
Alternatives. The applicant has provided information concerning project alternatives. The applicant published their “Lower Las Vegas Wash Planning Study” in July 2010. This study identified the minimum number of grade control structures needed to reduce the significant channel degradation that persists within the lower Las Vegas Wash. The NPS Lake Mead National Recreation Area published an Environmental Assessment (EA), “Lower Las Vegas Wash Flow Regulation,” in February 2013. Alternatives considered included the No Action Alternative, the Preferred Alternative, and alternatives considered early in the process but later eliminated. Under the No Action Alternative, no new stabilization measures would be implemented and no additional grade control structures would be constructed. As a result, flows in the lower Las Vegas Wash would not be further regulated, the effects of channel erosion would remain, high levels of sediment would continue to be transported from the Wash into Lake Mead and the wash channel would continue to deepen and widen. Under the Preferred Alternative, up to six new grade structures would be built downstream from existing structures. This alternative would be implemented in phases, with structures built as necessary, with the need for structures dependent upon future water levels of Lake Mead. Early alternatives dismissed from further study include an alternative to retrofit the bridge to withstand the 100 feet of scour predicted by hydraulic analyses and sediment transport models and an alternative to replace the bridge with a new structure and roadway approaches. 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 application includes minimization and avoidance actions. The applicant has not proposed compensatory mitigation. However, the applicant believes the proposed project would be self-mitigating. Following construction of the three previous drop structures, significant wetland growth occurred on the lateral borders of the Wash channel and it is anticipated that wetland growth would occur along most of the 1000-foot channel between drop structure 3 and the proposed drop structure 4. The project would also reduce the amount of sedimentation flowing into Lake Mead, thereby improving water quality.
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 also indicated that prior to construction they will apply for a Dust Control Permit from the Clark County and a Construction Stormwater Permit from the Nevada Department of Environmental Quality.
HISTORIC PROPERTIES: Based on the available information (including the National Park Service Environmental Assessment of the proposed project), no cultural resources were identified within the project's area of potential effect.
ENDANGERED SPECIES: The proposed activity may affect Federally-listed endangered or threatened species or their critical habitat. The National Park Service has consulted with the U.S. Fish and Wildlife Service, pursuant to Section 7 of the Endangered Species Act, and has completed that process as of October 12, 2012.
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-2007-02240-SG must be submitted to the office listed below on or before August 26, 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, Patricia.L.McQueary@usace.army.mil.
Attachments: 11 drawings