8/14/2015 1 AHMP National Conference – 2015 Joe Jenkins, PG, CHMM, CPESC POWER PLANT STORMWATER STABILIZATION THROUGH REVEGETATION, A CASE STUDY Topics • Black Hills Corporation Overview • Post Construction BMPs and Controls • Risk Assessment • BMP Repair • Engineering Design and BMP Selection • Soil Sampling and Amendments • Construction Phase • One Year Later BMP: Best Management Practice 3 4 • Based in Rapid City, SD, with corporate offices in Denver, CO, and Papillion, NE • Utility operations serve 765,000 utility customers in CO, IA, NE, SD, WY • Non-regulated businesses generate wholesale electricity, and produce natural gas, crude oil and coal. Utilities Electric Utilities Gas Utilities • Black Hills Power • Cheyenne Light* • Colorado Electric • Colorado Gas • Kansas Gas • Nebraska Gas • Iowa Gas Non-Regulated Energy Power Generation Coal Mining • Black Hills Electric Generation • Wyodak Resources Oil and Gas • Black Hills Exploration and Production Black Hills Corp. Overview
Transcript
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AHMP National Conference – 2015
Joe Jenkins, PG, CHMM, CPESC
POWER PLANT STORMWATER
STABILIZATION THROUGH
REVEGETATION, A CASE STUDY
Topics
• Black Hills Corporation Overview
• Post Construction BMPs and Controls
• Risk Assessment
• BMP Repair
• Engineering Design and BMP Selection
• Soil Sampling and Amendments
• Construction Phase
• One Year Later
BMP: Best Management Practice
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• Based in Rapid City, SD, with corporate offices in Denver, CO, and Papillion, NE
• Non-regulated businesses generate wholesale electricity, and produce natural gas, crude oil and coal.
Utilities
Electric Utilities Gas Utilities• Black Hills Power
• Cheyenne Light*
• Colorado Electric
• Colorado Gas
• Kansas Gas
• Nebraska Gas
• Iowa Gas
Non-Regulated Energy
Power Generation Coal Mining
• Black Hills Electric Generation
• Wyodak Resources
Oil and Gas
• Black Hills Exploration and Production
Black Hills Corp. Overview
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Pueblo Airport Generating Station (PAGS)January 2012
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W. N. Clark StationCanon City, CO• 48 MW• 255,425 mT CO2e
• 24 employees
PAGS• 380 MW, 29 MW wind• 317,683 mT CO2e
• 14 employees• Replaced 300 MW of
coal-based purchased power
Impact of PAGS on GHG Emissions Reduction
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37% reduction in GHG Emissions
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Location of PAGs in Respect to Arkansas River
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Facility with Respect to Local Topography
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PAGS
Arkansas River
Approx. 3.6 miles
April 2012
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Area Designations
11Go to master slide >
Site of new turbine unit, construction beginning 2016
Pueblo County Stormwater Considerations
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No stormwater retention allowed by County
Army Corp Non-Jurisdictional WOTUS
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Natural Vegetation in and Around PAGS
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Shortgrass prairie co-dominant with Greasewood shrubland:• Blue Grama• Alkali saction grass• Galetta grass• Sand dropseed• Rabbitbrush• Cholla
Post-Construction BMPs and Controls
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Engineer’s Design 2010
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Power Block March 2013
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SE Stockpile and Detention Pond Area
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March 2013
West of Powerblock
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Culvert 9, 4 ft. box culvert
Culvert 10, 3 ft. round culvert
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Floodplain Analysis Culvert 10
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10 yr
25 yr100 yr
Culvert 10 – 100 yr Flood Level Determination
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100 yr FP
10 yr FP
July 2013 – 2.05” rainfall
Culvert 10 – 100 yr Flood Level Determination
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100 yr FP
September 2013 – 2.86” rainfall
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Rain Event July 15, 2014
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Pond Slope Design
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Evaporation Ponds
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Laydown Yard March 2013
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Shale Stockpiles
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RISK ANALYSIS
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Risk Analysis – August 2013
• Review of existing stormwater restoration practices and BMPs
• State of Colorado Stormwater Civil Penalty Matrix
• Determine Base Gravity Penalty
• Account for Duration of Violation (multi-day penalties)
• Apply Aggravating or Mitigating Factors
• Add Economic Benefit
• Multiple Violations
• Ability to Pay
• Multi-Day Penalties
• Conducting Covered Activities without a Stormwater Permit
• Failure to Prepare Stormwater Management Plan (SWMP)
• Deficient Stormwater Management Plan (SWMP)
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Violation Matrix Multi-Day Penalties Example
Day 1 ($1037.50) = $ 1,037.50
+ Days 2-10 ($1037.50) X (9 days) X (50%) = $ 4,668.75
+ Days 11-50 ($1037.50) X (40 days) X (40%) = $16,600.00
+ Days 51-100 ($1037.50) X (50 days) X (30%) = $15,562.50
+ Days 101-200 ($1037.50) X (100 days) X (20%) = $20,750.00
+ Days 201-270 ($1037.50) X (70 days) X (10%) = $ 7,262.50
Multi-Day Base Gravity Penalty = $65,881.25
Applicable to each identified violation:
• Failure to Install, Maintain, or Properly Select BMPs
• Failure to Perform Inspections of Stormwater Management System
• Pollution, Contamination, or Degradation of State Waters
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PAGS at Risk Stormwater Management System
• Permit expanded in phases but no evidence of communication with State on expansions
• Initial permit described access road and plant
• Did not include evaporation ponds or shale stockpiles
• No post-construction version of the SWMP• Inadequate SWMP
− Site description changes not addressed
− Site map not updated
− BMPs not updated
− Final stabilization practices not described
• Examples of Recent Violations• 2011, Timnah Ranch, $90,223 penalty
• 2012, Sumo Development, $100,000 penalty
• 2013, Rock Mt. Materials, $65,000
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PAGS at Risk for Stormwater Management
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Maintenance and Replacement of Failed BMPs• The potential to discharge sediment-laden water from numerous outfalls around the plant site. Each outfall is a separate violation.
• Stormwater sediment retention basin SE corner of facility
• Multiple locations along both arroyos on each side of the shale pile
• All silt fence at the site
• Partially riprapped channels
• Slopes along the substation
• Unstabilized drainage along access road
• Unstabilized drainage (no controls) along the dirt road west of shale pile
• Unstabilized slopes (no controls) around evaporation ponds
• Unstabilized surfaces (no controls) around evaporation ponds
• Unstabilized surfaces (no controls) around sediment retention basin
• No perimeter control around stockpile northwest of plant
• No perimeter control around stockpile southeast of plant
• No perimeter control around small stockpile by arroyo south of access road
• No or incomplete perimeter control around shale piles
• Sediment tracking on roadways at dirt road access west of shale pile
• Sediment on road east of arroyo where it flows with run off being tracked along roadway above arroyo (potential discharge to state waters)
• Erosion (rills) on shale pile
• Erosion (rills) on evaporation pond slopes
• Erosion (rills) on access road slopes
• Erosion (rills) on south side of substation
• Erosion (rills) on sediment retention basin
• Erosion (rills) on slopes of drainage channels
• Improperly designed sediment retention basin with direct discharge potential off site
• Failed controls in “laydown yard”
• Failed controls on horizontal surfaces in power block area
• Lack of weed control
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INITIAL REPAIR OF FAILED BMPS
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Initial Repair of Failed BMPs
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Initial Repair of Failed BMPs
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Initial Repair of Failed BMPs
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Total Cost of repairs $160,000
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Initial Repair of Failed BMPs
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5/13/13 South Powerblock Drainage
Power Block 4, 2014
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BMP Maintenance 2014
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Engineering Design and BMP Selection
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• Control Technology and BMP Selection
• Available Technologies• Revegetation‒ Soil sampling
