Drawdown at Lower St. Anthony Falls Lock and Dam for Inspection of the Bassett Creek Flood Control Project

Transcription

1 DRAFT ENVIRONMENTAL ASSESSMENT Drawdown at Lower St. Anthony Falls Lock and Dam for Inspection of the Bassett Creek Flood Control Project U.S. ARMY CORPS OF ENGINEERS ST. PAUL DISTRICT JANUARY 2019

2 Table of Contents DRAFT ENVIRONMENTAL ASSESSMENT Drawdown at Lower St. Anthony Falls Lock and Dam for Inspection of the Bassett Creek Flood Control Project 1 Introduction Purpose and Need Authority Alternatives Proposed Action No-Action Alternative Alternatives Considered but Rejected Affected Environment and Environmental Consequences Natural Resources... 3 Geology and Soils... 3 Vegetation... 3 Wetlands... 3 Wildlife... 4 Mussels and Other Macroinvertebrates... 4 Fish... 4 Water Quality... 4 Threatened and Endangered Species Socio-Economic Resources... 5 Recreation... 5 Navigation... 5 Energy Needs... 5 Environmental Justice Cultural Resources Cumulative Effects ENVIRONMENTAL COMPLIANCE AND COORDINATION Coordination Applicable Environmental Laws and Executive Orders Distribution and Review of Draft Environmental Assessment Bibliography... 8 Appendix A. Correspondence Appendix B. Draft FONSI ATTACHMENTS EA-i

3 1 Introduction 1.1 Purpose and Need DRAFT ENVIRONMENTAL ASSESSMENT Drawdown at Lower St. Anthony Falls Lock and Dam for Inspection of the Bassett Creek Flood Control Project The Bassett Creek Flood Control Project was constructed under the direction of the Corps of Engineers in 1979 and is managed by the City of Minneapolis, located in Hennepin County, Minnesota. The Project includes a 12-foot tunnel, the crown of which is under the normal pool elevation of feet, and discharges into the intermediate pool of Upper and Lower St. Anthony Falls Locks and Dams (Figure 1). The Operation and Maintenance Manual for the Bassett Creek Flood Control Project states that A thorough inspection of the inside of the tunnel will be conducted at least once every 5 years, except the portion of the tunnel under water which will be dewatered and inspected at least once every 20 years. The last inspection of the underwater portion of the tunnel was in The project manager would now like to inspect the project every ten years. Inspection of the tunnel requires a drawdown of the intermediate pool. Figure 1. Project location map EA-1

4 1.2 Authority The Bassett Creek Flood Control Project was authorized by Section 173 of the 1976 Water Resources Development Act (Public Law ). There is an obligation to operate and maintain the project structures and facilities in accordance with the regulation prescribed by the Secretary of the Army. The Operation and Maintenance Manual for the Bassett Creek Flood Control Project indicates that the tunnel shall be inspected and cleaned as required. 2 Alternatives 2.1 Proposed Action To facilitate a periodic inspection of the Bassett Creek Tunnel, the intermediate pool at St. Anthony Falls must be drawn down thirteen feet to an elevation of feet. The inspection is to take place approximately once every ten years. The drawdowns would occur outside the Mississippi River Navigation season, during the winter months. The 2019 drawdown is targeted for February 25 March 1, but the dates may deviate due to weather conditions. Drawdowns for the inspections would typically last five to seven days, and the pool would be expected to return to the normal operating elevation after approximately ten days. A typical drawdown schedule is provided in Table 1 below. This schedule assumes a steady inflow of 5,475 cubic feet per second (cfs), which is the average for winter. Table 1. Typical drawdown schedule Day Elevation Flow cfs Notes: feet ,975 Pool Drawdown Begins (Increase 500 cfs) , , ,475 Maximum Drawdown (Decrease 500 cfs) , , ,975 Begin to raise pool (Decrease 500 cfs) , , ,475 Normal Operations Continues (Increase 500 cfs) The drawdown would occur gradually and the rate of pool fall must be kept under 1.5 feet per hour when the pool is outside the normal operating band. Minimizing the rate of fall reduces the potential for sloughing on the river banks and the dike constructed at the site of the former hydropower plant adjacent to Lower St. Anthony Falls Dam. EA-2

5 2.2 No-Action Alternative Under the No-Action Alternative, the pool would not be drawn down to facilitate the inspection of the Bassett Creek Flood Control project tunnel. Under this alternative, the tunnel would either not be inspected, or it would be inspected by other means that may be less thorough and/or less safe for inspectors. 2.3 Alternatives Considered but Rejected Inspecting the tunnel by dewatering the structure with a coffer dam or stop logs was also considered. There are stop logs slots in the flood control outlet structure, but there are no stop logs fabricated for the structure. It would be expensive to construct a cofferdam or to fabricate stop logs for the project and pump water out of the tunnel. Because there is only one stop log slot, the project does not offer redundancy for safely entering the tunnel under full head conditions. Prior to the inspection in 2008, the Corps of Engineers evaluated alternatives and concluded that without the redundancy of a stop log and gate system, and considering the potential risk of a pump failure during continuous tunnel dewatering, the inspection could be performed most safely by lowering the pool. For life safety and cost reasons, the alternative of dewatering the tunnel with a stop log or coffer dam was not selected. 3 Affected Environment and Environmental Consequences 3.1 Natural Resources Geology and Soils The uppermost rock layers in this area are part of the Platteville Formation, beneath which is a thin layer of Glenwood Shale. Below the Glenwood Shale is Saint Peter Sandstone, rock which was once beach sand. St. Peter Sandstone is rock which is easily eroded or worn away. No-Action Alternative The No-Action Alternative would have no effect on geology or soils. Proposed Alternative To minimize the potential for sloughing of the river banks, the drawdown would occur gradually. The Proposed Alternative may have a minor effect on soils. Vegetation There is very little vegetation in the immediate project area. The project area is a rocky gorge in a highly urban area. The shores of the pool are primarily rock or concrete. Higher on the slopes there are some areas of grass and landscaped trees and shrubs, typical of an urban setting. The project would not require the removal of any trees or shrubs. The No-Action and Proposed Alternatives would therefore have no effect on vegetation. Wetlands There are no wetlands within the project area; therefore, the No-Action and Proposed EA-3

6 Alternatives would have no effect on wetlands. Wildlife Wildlife species typical of this region include such common avian species as robin, blue jay, and chickadee, while common mammalian species include raccoon, rabbit, and gray squirrel. Due to the rocky substrate, frogs, turtles and other aquatic amphibians would likely not be using the pool for hibernation. No-Action Alternative The No-Action Alternative would have no effect on wildlife. Proposed Alternative Drawing the pool down may make it difficult for wildlife to access the river. This impact would be minor and short-term. Mussels and Other Macroinvertebrates Mussel surveys conducted in the intermediate pool between Upper and Lower St. Anthony Falls revealed low species diversity and low abundance (Kelner and Davis, 2002). No state or federally listed species were found. No-Action Alternative The No-Action Alternative would have no effect on mussels and other macroinvertebrates. Proposed Alternative Mussels and other macroinvertebrates in the drawdown zone may be killed by stranding and desiccation or freezing, whereas some mobile species may be able to escape to deeper water. Once the pool returns to its normal operating level, macroinvertebrates will recolonize the pool. The Proposed Alternative will have a short-term and minor effect on macroinvertebrates. Fish No-Action Alternative The No-Action Alternative would have no effect on fish. Proposed Alternative During the drawdown, fish are likely to move to deeper water. Any fish that become trapped during the drawdown would be subject to predation by birds and freezing temperatures. However, fish will reoccupy the pool following reflooding. Overall, the Proposed Alternative will have a short-term and minor effect on fish species. Water Quality No construction activity is planned within the river during the drawdown. The No-Action and Proposed Alternatives would have no effect on water quality. Threatened and Endangered Species There are no federally-listed species present within the defined action area; therefore, the St. Paul District has determined that the No-Action and Proposed Alternatives will have no effect on EA-4

7 threatened and endangered species. 3.2 Socio-Economic Resources Recreation There would be no recreational boating and fishing in the intermediate pool area during any proposed winter drawdowns; therefore, the No-Action and Proposed Alternatives would have no effect on recreation. Navigation Drawdowns would occur outside the navigation season. The No-Action and Proposed Alternatives would have no effect on commercial navigation. Energy Needs Xcel Energy and Brookfield Renewable Energy produce hydropower from the intermediate pool and St. Anthony Falls. No-Action Alternative There would be no effect of the No-Action Alternative on energy needs. Proposed Alternative Xcel Energy and Brookfield Renewable Energy may not be able to produce power during the drawdown resulting in a minor, short-term impact. Environmental Justice The City of Minneapolis is located in Hennepin County, Minnesota and had a population of 382,578 according to 2010 population estimates (US Census Bureau). The median household income is $55,720, represented from 183,344 housing units, which is lower than the state median household income of $63,217. A fair amount of the city is on a fixed income, with 20.7% of the population of Minneapolis being below the poverty level, which is higher than the state poverty level of 10.8%. The No-Action and Proposed Alternatives would not have any adverse impacts related to environmental justice as the action would not disproportionally impact any individuals of a particular social or economic status. 3.3 Cultural Resources Lower St. Anthony Falls (LSAF, HE-MPC-0285/0288) and Upper St. Anthony Falls (USAF, HE-MPC-0177) are eligible for listing on the National Register of Historic Places (NRHP) as is the Upper Mississippi River 9-Foot Navigation Project. In addition, the USAF is significant for its association with and location within the St. Anthony Falls Historic District. Numerous other historic properties are located adjacent to and within the intermediate pool, many associated with the St. Anthony Falls Historic District. EA-5

8 The Bassett Creek Tunnel is of relatively recent construction and does not meet the criteria for a historic property or for listing on the NRHP. The tunnel outlet is typically submerged and not visible. Almost all of the intermediate pool s shoreline has been improved with historic and modern construction, such as retaining walls, tailrace outlets, spillways, and, lock structures. None of the foundations for the historic structures would be compromised from temporary lower water levels. The Corps has determined that the No-Action and Proposed Alternatives would have no potential to cause effects to historic properties. In accordance with 36 CFR800.3(a)(1), consultation with the SHPO is not required. 3.4 Cumulative Effects The drawdown of the intermediate pool would occur approximately once every ten years. Water levels would be lower than normal for around ten days during each drawdown event. Aquatic macroinvertebrates exposed to the elements during drawdowns will likely be killed. Many of these macroinvertebrates are able to quickly recolonize. Some longer lived species, such as particular mussel species, take more time to recover. A drawdown every ten years may prevent significant mussel colonization. However, due to the highly degraded habitat and the low abundance of specimens found in the area, it is unlikely that significant mussel colonization would occur in this area. The overall cumulative effects of the project would be minor. EA-6

9 Environmental Assessment Matrix for Proposed Project No Action Alternative Proposed Alternative BENEFICIAL ADVERSE BENEFICIAL ADVERSE PARAMETER A. Social Effects SIGNIFICANT SUBSTANTIAL 1. Noise Levels X X 2. Aesthetic Values X X 3. Recreational Opportunities X X 4. Transportation X X 5. Public Health and Safety X X 6. Community Cohesion (Sense of Unity) X X 7. Community Growth and Development X X 8. Business and Home Relocations X X 9. Existing/Potential Land Use X X 10. Controversy X X B. Economic Effects 1. Property Values X X 2. Tax Revenue X X 3. Public Facilities and Services X X 4. Regional Growth X X 5. Employment X X 6. Business Activity X X 7. Farmland/Food Supply X X 8. Commercial Navigation X X 9. Flooding Effects X X 10. Energy Needs and Resources X ST C. Natural Resource Effects 1. Air Quality X X 2. Terrestrial Habitat X X 3. Wetlands X X 4. Aquatic Habitat X X 5. Habitat Diversity and Interspersion X X 6. Biological Productivity X ST 7. Surface Water Quality X X 8. Water Supply X X 9. Groundwater X X 10. Soils X X Threatened or Endangered Species X X D. Cultural Resource Effects 1. Historic Architectural Values X X 2. Precontact & Historic Archeological Values X X X = Long-term effects; ST = Short-term effects. MINOR NO EFFECT MINOR SUBSTANTIAL SIGNIFICANT SIGNIFICANT SUBSTANTIAL MINOR NO EFFECT MINOR SUBSTANTIAL SIGNIFICANT EA-7

10 4 ENVIRONMENTAL COMPLIANCE AND COORDINATION 4.1 Coordination Xcel Energy and Brookfield Renewable Energy operate hydropower facilities at St. Anthony Falls and the intermediate pool. The University of Minnesota s St. Anthony Falls Hydraulic Laboratory also operates in the area. The laboratory draws water off the upper pool and outlets into the intermediate pool. Xcel Energy, Brookfield Renewable Energy, and the University of Minnesota were notified of the plans to draw down the intermediate pool. No concerns had been identified prior to the release of this Draft Environmental Assessment. The proposed work has been coordinated with the Minnesota Department of Natural Resources, U.S. Fish and Wildlife Service and the National Park Service (Attachment 1). Agencies will also be given the opportunity to review and provide comments on the draft environmental assessment. Coordination would occur with resource agencies and affected businesses prior to future drawdowns. A public notice or press release would also be issued prior to the drawdowns. 4.2 Applicable Environmental Laws and Executive Orders The proposed alternative would comply with federal environmental laws, Executive Orders and policies, and applicable state and local laws including but not limited to the Clean Air Act, as amended; the Clean Water Act, as amended; the Endangered Species Act of 1973, as amended; the Fish and Wildlife Coordination Act of 1958, as amended; the Land and Water Conservation Fund Act of 1965, as amended; the National Historic Preservation Act of 1966, as amended; the National Environmental Policy Act of 1969, as amended; the Farmland Protection Policy Act of 1981, as amended; Executive Order Protection of Wetlands; Executive Order Environmental Justice; and Executive Order Floodplain Management. 4.3 Distribution and Review of Draft Environmental Assessment This draft environmental assessment is being made available for a 30-day public review and comment period. A copy of the draft environmental assessment can be found at Questions on the project or comments on the draft environmental assessment can be directed to Derek Ingvalson at or Derek.S.Ingvalson@usace.army.mil. 5 Bibliography Kelner, D.E. and M. Davis Final Report: Mussel (Bivalvia: Unionidae) survey of the Mississippi National River and Recreation Area Corridor, Contract report to the National Park Service Mississippi National River and Recreation Area and the Great Lakes Network Inventory and Monitoring Program. Minnesota Department of Natural Resources, Division of Ecological Services, St. Paul, MN 43pp. with appendices. EA-8

11 Appendix A. Correspondence

12 From: To: Cc: Subject: Date: Glomski, Lee Ann M CIV USARMY CEMVP (USA) "jason.spiegel@state.mn.us"; "Huber, Bill P (DNR)"; "nick_utrup@fws.gov"; "john_anfinson@nps.gov"; "dan.dieterman@state.mn.us" Ingvalson, Derek S CIV USARMY CEMVP (US); Clark, Steven J CIV USARMY CEMVP (US) intermediate pool at St. Anthony Falls drawdown Thursday, January 3, :58:00 AM All, To facilitate the inspection of the Bassett Creek Tunnel, the intermediate pool at St. Anthony Falls is proposed to be drawn down 13 feet to an elevation of feet. A target date of February 25 March 1, 2019 has been selected. Should weather conditions warrant, this date may be pushed out one week. Assuming this is the inspection date, drawdown and refilling process will follow the schedule shown in the table below. This schedule assumes a steady inflow of 5475 cfs, which is the average for this time of year. The drawdown would occur gradually. The rate of pool fall will be kept under 1.5 feet per hour when the pool is outside the normal operating band. Minimizing the rate of fall reduces the potential for sloughing on the river banks and the dike constructed at the site of the former hydropower plant adjacent to Lower St. Anthony Falls Dam. The last time a drawdown was conducted in this pool was Date Hour Elevation Flow cfs Notes: 23-Feb ft 5975 Pool Drawdown Begins (Open 500 cfs) 24-Feb ft Feb ft Feb ft 5475 Maximum Drawdown (Cut 500 cfs) 27-Feb ft Feb ft Mar ft 5475 Begin to raise pool (Cut 500 cfs) 2-Mar ft Mar ft Mar ft 4975 Normal Operations Continues (Open 500 cfs) An environmental assessment is being drafted and will be made available for a 30-day public and agency review and comment period. We will send you a copy of the EA once it is available. We apologize for the short notice. LeeAnn Glomski Biologist USACE - St. Paul District

13 Appendix B. Finding of No Significant Impact (FONSI)

14 DEPARTMENT OF THE ARMY U.S. ARMY CORPS OF ENGINEERS, ST. PAUL DISTRICT 180 FIFTH STREET EAST, SUITE 700 ST. PAUL, MN Regional Planning and Environment Division North DRAFT FINDING OF NO SIGNIFICANT IMPACT In accordance with the National Environmental Policy Act, the Corps of Engineers, St. Paul District, has assessed the environmental impacts of the following project: DRAWDOWN AT LOWER ST. ANTHONY FALLS LOCK AND DAM FOR INSPECTION OF THE BASSETT CREEK FLOOD CONTROL PROJECT The purpose of the proposed action is to allow for reoccurring inspections of the Bassett Creek Flood Control Project. The Corps of Engineers will facilitate the inspection by deviating from the normal operation of the Lower Saint Anthony Falls Lock and Dam by lowering the intermediate pool above Lower Saint Anthony Falls by thirteen feet. The entire process of lowering, inspecting, and raising the water level will occur over approximately ten days. The inspection and water level deviation will occur about once every ten years to ensure the condition and safety of the flood control project. This Environmental Assessment covers the current and future instances of this deviation. This Finding of No Significant Impact is based on the following factors: the proposed project would have temporary minor adverse impacts to wildlife, fish, and hydropower energy production. The geology and soils of the riverbank along shore of the drawdown may also experience slight adverse impacts. The Basset Creek Watershed Management Commission will benefit from being able to inspect the flood control project features to ensure the project operates as intended. For the reasons above, the proposed action does not constitute a major federal action significantly affecting the quality of the human environment. Therefore, an environmental impact statement will not be prepared. Date Elliott L. Stefanik Acting Deputy Chief, Regional Planning And Environment Division North