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NRT, AN OBG COMPANY, PRESENTS:
Fountain Lake Restoration Project
Richard H. Weber, PE
SAME Kansas City Industry Day, March 28, 2017
OUTLINEProject History
Lake Modeling
Dredging Plan
Upland Sediment Placement Site
Agency and Public Coordination
Project Status
2
Shell Rock River Watershed District (SRRWD)
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Established in 2003, governed by a Board of Managers, and accountable to the MN Board of Water and Soil Resources
Watershed covers 246 square miles in Freeborn County including 11 shallow lakes
Guided by a Water Management Plan to conserve and restore water resources
Funds come from property tax, 0.5% local sales tax (since 2005), and grants ($7.5M for dredging appropriated from MN General Fund in 2014)
“SRRWD Mission is to implement reasonable and necessary improvements to the water-related and other natural resources of the district.”
Fountain Lake
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Located in Albert Lea, MN
555-acre Lake popular for recreation
63,000 acre watershed
Added to MPCA list of impaired
waters from high nutrient levels, overabundant
algae, and low clarity
Fountain Lake Restoration Project
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Improve Lake Water Quality
Dredge accumulated sediment
Reduce nutrient loads
Enhance Aquatic Habitat
Increase water depth and clarity for
improved fish habitat
Improved Recreational Opportunities
Improve water clarity for swimming
Increase water depth for boating
Phosphorous Loading
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WATER: Bottom of Lake
SEDIMENT: Lake Bottom
ElectronIron Bound-Phos Organically-
bound Phos
Phos
slow
fast
bio-degradation
• Loosely bound and redox sensitive• Released under anaerobic conditions• Primary source for internal loading
Mobile phosphorus (iron-bound)
• Released during biodegradation of organic phosphorus in sediment
• Secondary source for internal loading
Organically-bound phosphorus
Sediment Characterization
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Dredge Design –Sediment Chemistry
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Chemistry used for existing conditions / calibration
Chemistry used for post-dredge conditions
Dredge cut depth
Lake Modeling –Dredge Benefits
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Physical, chemical, and biological Lake processes are interrelated and complex
A hydrodynamic and ecological model is needed to integrate and predict potential water quality effects of dredging
With dredging/deepening of Fountain Lake: Increased lake volume, change in stratification, and new sediments with new chemistry exposed to water column
Provides a technical basis for Lake restoration planning
Lake Modeling –Delft 3D
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Calibrate hydrodynamics and sediment transport
Calibrate water quality model – solids, nutrients, phytoplankton, DO, temperature
Use model to estimate effects of dredging –mobile and organic phosphorus concentrations; greater lake volume and depth
Modeled Effects of Dredging
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Changes to bathymetry result in increased periods of thermal stratification
Increased periods of thermal stratification results in less mixing of the water column
Reductions in average and maximum summer total phosphorus concentrations
Reductions in the frequency and magnitude of phytoplankton blooms (chlorophyll a)
Increased average and maximum summer water clarity (Secchi disk depths)
Dredging Plan
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Based on sediment phosphorus chemistry
Modified for constructability
Dredging ~50% of Lake surface area
Total project volume of approximately 1.2 million CY
Average dredge cut ~3 ft
Design in permit review and subject to change
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Sedi
men
t Pla
cem
ent S
ite
FOUNTAIN LAKE
CDF SITE SEARCH AREA
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Sedi
men
t Pla
cem
ent S
ite Evaluated 9 parcels over 6 months in mid-2015 –all were removed from consideration
Presence of buried utilities
Unfavorable terrain
Difficult dredge pipeline route logistics
Unwilling landowners
Proximity of residences (high hazard dam classification)
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Sedi
men
t Pla
cem
ent S
ite Located suitable site in late 2015 with interested and cooperative landowner
Within 3 miles of farthest dredge area in Fountain Lake
Located along existing drainage features for gravity flow of return water to Fountain Lake
Usable topography and low hazard for dam permitting
Willing landowner
CELL 1
CELL 3
Geotechnical Investigation
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35 standard penetration test (SPT) borings to 15 to 25 ft in berm alignments, borrow areas, and general footprint
Also undisturbed Shelby tube samples and bulk samples off the hollow stem augers
11 temporary wells to assess seasonal water table
Additional 5 borings and 7 backhoe test pits to further characterize soft organic soils in mapped wetland
Geotechnical laboratory testing program
Site Investigation
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Soil Borings
GW Wells
Utility Marking• Buried Gas• Buried Fiber Optic• Overhead Electric
Soft Deposits
Wetland Mitigation
Geotechnical Laboratory Testing
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INDEX TESTSMoisture, Grain Size
Atterberg LimitsLoss-on-Ignition
Moisture-Density
STRENGTH TESTSUnconfined Compression
Direct ShearTriaxial Shear (UU & CU)CONSOLIDATION TESTS
Grain Size Distribution Triaxial Shear: CU with Pore Pressure Unconfined Compression
3-Cell system for phased permitting and construction
Configuration restricted by utilities, drainage ditch, and property lines
Make use of existing topography
Construct berms in low elevation
Tie into existing higher elevation
CDF Design
CELL 1
CELL 3
CELL 2
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Designed CapacityCell 1 = ~688,000 CYCell 2 = ~322,000 CYCell 3 = ~265,000 CYTotal = 1,275,000 CY
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Typical Cross-Section
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CDF Design
3H:1V Exterior Slope
Conceptual Berm Cross Section
2.5H:1V Interior Slope
12 ft Crest for Vehicle Access
25 ft Max Height
6 ft Deep Inspection Trench
Slopes Stabilized with Grass
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Slope Stability Analyses
End of Construction
Stability Analysis
Long-Term Steady Seepage
1.3
1.3
Minimum Safety Factor
Rapid Drawdown
Seismic Pseudo-Static
1.0
1.0
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Consolidation Settlement Analyses
Soil Profile Sandy Lean Clay Lean Clay Layered Peat/Clay
CDF Cell 1, 2, 3 1, 2, 3 2, 3
Total Settlement (ft)
1.7 2.6 7.4
Time to 90% (Yrs)
138 65 5.2
Settlement at 5 Yrs (ft)
0.3 0.7 5.1
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CDF Process Flow Diagram
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Box Riser Weir design and pictures courtesy of USACE Jacksonville District
CDF Weir Box Riser
U.S. Army Corps of Engineers design
Controls discharge of CDF supernatant
Weir boards are added to the box riser structure to increase ponded water within CDF
Surrounding dock and gangway float and rise along box riser structure as water rises
Provides easy safe access to weir from perimeter berm
CDF Weir Box Riser
Weir overflow water flows out the base of the box riser structure via HDPE pipe through perimeter berm
Equipped with emergency flap gate to stop flow
Concrete foundation sized to prevent flotation
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Box Riser Weir design and pictures courtesy of USACE Jacksonville District
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CDF Weir Box Riser
Long Tube Column Settling Test shows decreasing TSS with retention time
18 ft minimum weir length calculated for maximum flow of 7,160 gpm (typical of 14-inch dredge)
5 ft square box riser designed for 20 ft of weir length
CDF retention time can be controlled by slurry flow rate and ponded water depth
CDF ponded water depth expected to exceed 2 ft for majority of operation until nearing completionLong Tube Column Settling Test data analysis performed by M.R. Palermo (2016)
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Agency and Public Coordination
MN Environmental Quality Board –environmental assessment worksheet, public comment, and decision negative declaration
MN Board of Water and Soil Resources Project Plan review
MN Department of Natural Resources Project Plan review
SRRWD public hearings and Board workshops
Public outreach – e.g., booth at County fair
29
Permitting Agencies
MN Department of Natural Resources Freeborn County
Dam Safety Permit (CDF) Conditional Land Use Permit
Public Waters Work Permit (dredging) Wetland Conservation Act
Water Appropriations Permit (dredging) ROW Work Permit (Dredge pipeline route)
MN Pollution Control Agency MN Department of Transportation
Notification to Manage Dredged Material ROW Work Permit (Dredge pipeline route)
Section 401 CWA Water Quality Certification City of Albert Lea
Construction Stormwater (NPDES) Access Agreements
U.S. Army Corps of Engineers Private Citizens
Section 404 CWA CDF Discharge Access Agreements (Dredge pipeline route)
Federal Aviation Administration
Aeronautical Hazard Determination
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Permitting AgenciesEnvironmental Assessment Worksheet
Required due to mandatory category (disturbance of 1-acre or more of public waters)
Completed worksheet providing project background, necessity, benefits, and impacts
Distributed to list of agencies and posted for public comment
Responded to comments and made determination that full Environmental Impact Statement was not needed
Total duration to complete EAW process was approximately 4 months EQB Monitor Notice, August 8, 2016
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Permitting AgenciesDam Safety Permit
CDF regulated by MNDNR as a Dam due to berm height and storage capacity
Required extensive permit application submittal and review time
Required dam breach inundation study for hazard classification
Required development of Operation & Maintenance Plan and Emergency Action Plan
Total duration until permit issued approximately was 13 months
Minnesota Department of Natural Resources, Permit Guidelines for Dams
32Inundation Study performed by Barr Engineering
Project Status
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CDF Cell 1 construction is under contract with construction planned from April to August 2017
Dredging design of entire lake is complete and pending Agency review of permits for first phase
Dredge Contract 1 bid release expected May 2017; dredging to begin August or September 2017
CDF Cells 2 and 3 construction, and Dredge Contract 2, in future years
35
Option to Use District-Owned Equipment
• IMS 7012 Versi-Dredge (12”)• Flowmeter• Three 325-HP Booster Pumps• Several thousand feet of HDPE
pipe
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Future Use of CDF Site?“Mine” the sediment for topsoil and agriculturallandspreading, and continue use for dredge spoils
Return to agricultural use
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ACKNOWLEDGEMENTSShell Rock River Watershed DistrictNatural Resource Technology, Inc., an OBG CompanyBarr EngineeringPeterson, Kolker, Haedt & Benda, Ltd.Jones, Haugh & Smith, Inc.WSB & Associates, Inc.
NRT, AN OBG COMPANY, PRESENTS:NRT, AN OBG COMPANY | THERE’S A WAY
Questions?Rich Weber | [email protected] | 414.837.3582
