Lake Seventeen and Little Suction Creek Project Environmental - - PowerPoint PPT Presentation
Lake Seventeen and Little Suction Creek Project Environmental Assessment Meeting Agenda 1. Project Location and Watershed Area 7. Preliminary Alternatives (4) 2. Project Background 8. Environmental Investigations 3. Current Design Facts
1. Project Location and Watershed Area 2. Project Background 3. Current Design Facts 4. Existing Conditions 5. Purpose and Need 6. Previous Investigations 7. Preliminary Alternatives (4) 8. Environmental Investigations 9. Final Product 10. Outreach 11. Discussion
Little Suction Creek Diversion
Lake 17 Watershed ~19 mi2 Little Suction Creek Watershed above diversion ~47 mi2
resource
September 25, 1986
events and inadequate repairs Rehabilitation project in Fort Belknap
protection Repairs Needed to Rehabilitate Dam
top of dam elevation of 3025.50’
earthen auxiliary spillway
~750 feet
elevation is ~450 feet
spillway
principal spillway capacity increases to 106 cfs
General Characteristics
Breach at the Little Suction Creek Diversion Outlet Pipe Protruding on the Dam at Lake 17
2017 Watershed & Flood Prevention Operation Proposal Guidance 2014 Clean Water Act 404 Application 2014 Bureau of Indian Affairs Historic Preservation Office Findings & Report 2013 Operation & Maintenance Agreements 2012 NRCS Lake 17 Dam Plan and Little Suction Creek Diversion Drawing 2012 Breach Summary Report 2010 NRCS Biological Assessment 1987 Downstream Hazard Assessments by Bureau of Reclamation 1967 Water Resources Survey 1965 Geology and Hydrology Survey by the BIA
TWO YEAR MINIMUM SUSTAINABILITY Year 1 Cylcle Days Utilization ET Loss Net Loss/Gain NET VOLUME 18.1 83.3 32.6
18.1 83.3 32.6
18.1 104.2 11.7
15 62.5 114.6
43.0 46 325.7 135.4
327.2 76 683.8 145.8
2164.5 107 654.7 166.7
2898.5 138 314.7 208.3
2600.1 168 62.5 187.5
2327.1 183 42.3 187.5
2306.9 18.1 145.8
2241.1 18.1 104.2 11.7 2199.4 Year 2 Cylcle Days Utilization ET Loss Net Loss/Gain NET VOLUME 18.1 83.3 166.6 2032.8 18.1 83.3 166.6 2032.8 18.1 104.2 145.7 2053.7 15 62.5 114.6 91.0 2108.4 46 325.7 135.4
2392.5 76 683.8 145.8
4229.9 107 654.7 166.7
4591.4 138 314.7 208.3
4293.0 168 62.5 187.5 18.0 4020.0 183 42.3 187.5 38.2 3999.8 0.0 145.8 122.2 3915.8 0.0 104.2 163.8 3874.2
– Dam will breach. Downstream channel will headcut the reservoir and so it reverts back into a prairie pothole. Existing diversion breach will widen until the natural character of an intermittent stream channel is restored.
– Dam rehabilitation following NRCS plans. Diversion decommissioned and footprint restored to a natural intermittent stream channel.
Dam rehabilitation following NRCS plans. Diversion rehabilitation following NRCS plans.
Alternative #2 : Initially Considered But Determined
Not to Meet the Project Purpose:
Decommission Dam & Diversion – Dam
decommissioned and footprint restored to a natural prairie pothole. Diversion decommissioned and footprint restored to a natural intermittent stream channel.
ELIMINATED
Total Construction Cost = $0 Annual O&M Cost = $0 Annual Net Economic Benefit for Irrigation Based on DNRC $30 per Acre-Foot = $0 Annual Net Economic Benefit for Stock Water Based on $1 Gain per Calf = $650 Lake 17 Storage Volume = 351 Acre-Feet Potential Water Available for Irrigation Based on 19.99” of Water Required for Alfalfa = 0 Acres Potential Water Available for Livestock Based on NRCS 25 gallons per Day for Cow-Calf Pairs = 12,534 Cow-Calf Pairs *Max Cow-Calf Pairs for Grazing Acreage = 650
Wildlife Habitat Rated Overall Poor to Fair
species of concern Recreation Potential Rated Poor
Total Construction Cost = $340,817 Annual O&M Cost = $0 Annual Net Economic Benefit for Irrigation Based on DNRC $30 per Acre-Foot = $0 Annual Net Economic Benefit for Stock Water Based on $1 Gain per Calf = $650 Lake 17 Storage Volume = 351 Acre-Feet Potential Water Available for Irrigation Based on 19.99” of Water Required for Alfalfa = 0 Acres Potential Water Available for Livestock Based on NRCS 25 gallons per Day for Cow-Calf Pairs = 12,534 Cow-Calf Pairs *Max Cow-Calf Pairs for Grazing Acreage = 650
Wildlife Habitat Rated Overall Poor to Fair
Recreation Potential Rated Poor
Total Construction Cost = $1,238,281 Annual O&M Cost = $13,373 (1% of Dam Construction Cost + $15.00 O&M Costs per Acre of Irrigation) Annual Net Economic Benefit for Irrigation Based on DNRC $30 per Acre-Foot = $4,424 Annual Net Economic Benefit for Stock Water Based on $1 Gain per Calf = $650 Lake 17 Storage Volume = 934 Acre-Feet Potential Water Available for Irrigation Based on 19.99” of Water Required for Alfalfa = 147 Acres Potential Water Available for Livestock Based on NRCS 25 gallons per Day for Cow-Calf Pairs = 33,353 Cow-Calf Pairs *Max Cow-Calf Pairs for Grazing Acreage = 650
Wildlife Habitat Rated Overall Fair to Good
species of concern Recreation Potential Rated Fair to Good
Total Construction Cost = $1,998,176 Annual O&M Cost = $29,071 (1% of Dam & Diversion Construction Costs + $15.00 O&M Costs per Acre of Irrigation) Annual Net Economic Benefit for Irrigation Based on DNRC $30 per Acre-Foot = $60,570 Annual Net Economic Benefit for Stock Water Based on $1 Gain per Calf = $650 Lake 17 Storage Volume = 4,038 Acre-Feet Potential Water Available for Irrigation Based on 19.99” of Water Required for Alfalfa = 606 Acres *457 Acres can be Sustained, but Agricultural Means & Methods Could Improve Potential Potential Water Available for Livestock Based on NRCS 25 gallons per Day for Cow-Calf Pairs = 72,098 Cow-Calf Pairs *Max Cow-Calf Pairs for Grazing Acreage = 650
Wildlife Habitat Rated Overall Good
Recreation Potential Rated Good
Wetland Determination (CWA 404 jurisdictional determination & 401 EPA regulations) THPO Consultation T&E species Economics/Socioeconomics/Income Recreation uses (Improve and conserve public recreations and public fish & wildlife) Land Access Permissions & Land Ownership for Improvements Irrigation Uses, Water rights, applicability to Water Compact, and agricultural water management Cumulative Impacts
for snowfall depths expected from the 5-year & 25-year snowfall
There is a low likelihood of Lake 17 ever filling from its own watershed
the 5-year snowfall depth
snowfall depth
area increases by 460 acres as the depth increases from 5-feet to 12- feet
surface area all increases the habitat value of the area
Directing Yields from Little Suction Creek into Lake 17 significantly increases yield
Annual 2yr – 24hr 5yr – 24hr 10yr – 24hr 25yr – 24hr 50yr – 24hr 100yr – 24hr Runoff Volume (ac-ft) 2,820 Peak Flow (cfs) 29 50 136 222 367 504 665
Runoff Volumes and Peak Flows
$2.00 per acre
Unit
1967 State Water Conservation Board Report
feet per year
acre-feet = 18,350 cattle
water needed
BIA Design File
Existing Lake 17 Dam Characteristics Dam Height 16 feet Dam Length 750 feet Top Width 16 feet Top of Dam Elevation 3025.50 feet Principal Spillway Crest Elevation 3020.90 feet Auxiliary Spillway Crest Elevation 3022.10 feet Surface Area at Top of Dam Elevation 41,267,533 Square Feet or 947.37 Acres Surface Area at Principal Spillway Crest Elevation 31,931,936 Square Feet or 733.06 Acres Surface Area at Auxiliary Spillway Crest Elevation 34,551,241 Square Feet or 793.19 Acres Storage Volume at Top of Dam Elevation 7,925 Acre-Feet Storage Volume at Principal Spillway Crest Elevation 4,038 Acre-Feet Storage Volume at Auxiliary Spillway Crest Elevation 4,954 Acre-Feet Estimated Average Annual Runoff Volume 2,820 Acre-Feet Estimated Average Annual Evaporation Volume 2,566 Acre-Feet (42 inches per Year) Estimated Average Annual Conveyance Loss Volume 4.97 Cubic Feet per Second per Mile Estimated Average Annual Storage Volume 1,461 Acre-Feet Estimated 2-Year Frequency Runoff Volume (50% Probability Occurrence) 3,088 Acre-Feet Estimated Storage Volume Expected Every Other Year 1,591 Acre-Feet
2013 Proposed Lake 17 Dam Characteristics Dam Height 17 feet Dam Length 1,800 feet Top Width 16 feet Top of Dam Elevation 3026.50 feet Principal Spillway Crest Elevation 3020.90 feet Auxiliary Spillway Crest Elevation 3023.10 feet Surface Area at Top of Dam Elevation 43,286,799 Square Feet or 993.73 Acres Surface Area at Principal Spillway Crest Elevation 31,931,936 Square Feet or 733.06 Acres Surface Area at Auxiliary Spillway Crest Elevation 36,762,883 Square Feet or 843.96 Acres Storage Volume at Top of Dam Elevation 8,894 Acre-Feet Storage Volume at Principal Spillway Crest Elevation 4,038 Acre-Feet Storage Volume at Auxiliary Spillway Crest Elevation 5,773 Acre-Feet Estimated Average Annual Runoff Volume 2,820 Acre-Feet Estimated Average Annual Evaporation Volume 2,566 Acre-Feet (42 inches per Year) Estimated Average Annual Conveyance Loss Volume 4.97 Cubic Feet per Second per Mile Estimated Average Annual Storage Volume 1,461 Acre-Feet Estimated 2-Year Frequency Runoff Volume (50% Probability Occurrence) 3,088 Acre-Feet Estimated Storage Volume Expected Every Other Year 1,591 Acre-Feet
Lake 17 Pool Alternative Characteristics Characteristic With Diversion at Base Elevation of 3014 feet Without Diversion at Base Elevation of 3014 feet Removal of Diversion & Dam Pool Surface Area 467 Acre Feet 351 Acre Feet 279 Acre Feet Pool Volume 1,864 Acre Feet 934 Acre Feet 612 Acre Feet Pool Perimeter 60,130 feet 48,050 feet 38,153 feet
principal spillway when the water surface is at the crest of the auxiliary spillway (400 cfs)
(the expected 2-year flow of Little Peoples Creek is 50 cfs)
breach to the peak
start of the break to a low flow of 200 cfs
be 14,000 cfs
Breach Characteristics
were estimated at $877,022 in 2013
improvements were estimated at $681,145 in 2013
Total Construction Costs for the project were estimated to be $1,558,167 in 2013
were estimated at $1,116,136 in 2017
improvements were estimated at $882,040 in 2017
Total Construction Costs for the project were estimated to be $1,998,176 in 2017
Watershed Project Plan
Plan of work and development of alternatives to restore functions of the dam
EA
Evaluate all reasonable alternatives so that plan is sound
Watershed Project Plan- EA
Develop Sound Project Plan Developed Alternatives Environmental Assessments Economic Impact Analysis Restore Functions of the Dam
Preliminary Investigations Oct 2018 – April 2019
Prepare Draft EA April 2019 – June 2019
June 2019 – August 2019
Prepare Final EA
P u b l i c & I n t e r a g e n c y I n p u t
water
Document Project Purpose and Need Document Project Purpose and Need
Investigate public response to Preliminary Alternatives (Today!) Investigate public response to Preliminary Alternatives (Today!) Develop a physically, environmentally, socially & economically sound project plan Develop a physically, environmentally, socially & economically sound project plan
NEPA Assessment Includes: NEPA Assessment Includes:
Time Lapse Photos from 2005, 2006, 2009, 2012 shows how dep ependent Lake e 17 is on the e Little Suction Cree eek Diversion to have water throughout the e year to provide for vegetation and wildlife
These photos when looked at closely show no, or very little water as well as the completely dried up reaches of the reservoir (the dark green shown in the photos is from plant life)
Lake 17
Potentially Interested Parties
Regulatory Agencies
Potential Outreach Methods
Availability, & Other Publications