Gwinnett County NRCS Watershed Dam Rehabilitation Program Jonathan Semerjian, PE Dept. of Water Resources Stormwater Management Gregg Hudock, PE Golder Associates Sam Fleming, PE Dewberry
Presentation Overview Background Program at a Glance Program Drivers Planning and Implementation Challenges Yellow River Dams Other Keys to Program Summary 2
Gwinnett County, GA Metro Atlanta 437 Square Miles Population 800,000+ Piedmont Region Headwaters Watersheds 1/3 Gulf of Mexico 2/3 Atlantic Ocean 437 Square Miles Population Background 805,000 80% Unincorp. / 20% Cities (16) 3
Background Gwinnett County Government Dept. of Water Resources Stormwater Management Stormwater Utility Funded Unincorporated Gwinnett & Lilburn Implemented in 2006 $34M Annual Revenues ($2.46/100 sf) Aging Stormwater Infrastructure ~1,300 Miles County-Maintained Pipe ~1,000 Miles Corrugated Steel ~500 Miles > 20 Years Old ~80,000 Drainage Structures 4
Background 14 NRCS Watershed Dams 357 Statewide GASDP Inventoried Dams 139 30 Category I 16 County Owned/Operated 56 Category II 3 County Owned/Operated 3 Exempt High Hazard 45 Exempt 4 County Owned/Operated 1 Not a Dam 4 Not Classified 2 County Owned/Operated 5
Program at a Glance Initiated NRCS Dam CIP in 1999 Began Design 1 Dam/year 1999-2001 Planning stage for remainder 2002-2004 Construction 2003 - present Status 9 dams upgrades completed 3 dams design completed and ready for construction 2 dams met GASDP standards without upgrade needs Total Program $20 million $14.8 million County funded $5.2 million NRCS Grant funded 65 NRCS / 35 Local Match 6
Program Drivers Public Safety and Regulatory Compliance Signed O&M Agreement Responsible Operator RC&D & SWCD Co-Sponsors Generate Revenues State Regulation Safe Dams Act (1978) Original law exempted NRCS Dams Exemption ended in 2000 Population Growth 72,000 (1970) 588,000 (2000) 805,000 (2010) Originally designed to protect agricultural lands from flooding Increased Development in the Breach Zone Classification High Hazard. Inadequate Spillway Capacity and Stability Most designed prior to Act Stepped Design Criteria 7
Resource Protection Flood Protection Program Drivers Up to 98% reduction in 1% annual chance peak Recreation County Parks Fish and Wildlife Habitat Water Quality Public Infrastructure Smaller downstream bridges and culverts Roads & utilities Property Values Increased values around lakes Reduced floodplain downstream 8
Program Implementation CIP Implemented in 1999 Y15, Y14, N1 under design 6-year program outlook Funded by General Property Tax Y16 & Y17 under design by USACE thru State Design Challenges Development encroachments Existing and Planned Development No room to widen earthen auxiliary spillways Leverage dam length for overtopping chute spillways RCC most cost effective Floodplain Management No Rise 9
Program Implementation NRCS Grant funding availability Small Watershed Rehabilitation Amendments of 2000 65/35 Cost share Federal Design Criteria plus GASDP Standards Full PMP design (NRCS) GASDP design storm based on size of dam ¼ to full PMP Refocus Design Strategies Enter into MOU with NRCS Try to secure Grant Funding 10
No Business Dam No. 1 (N1) Program Implementation Located in a golf course Construction impacts to golf course operations Necessary Spillway Width Construction Staging Loss of Revenue 35% Cost Share Fed Stds > 100% County GASDP Stds Grant req d Spillway designed to full PMP Greater impacts to adjacent properties Greater costs to construct Forwent grant pursuit and fund 100% local Widened earthen auxiliary spillway 11
Program Implementation Planning Strategy Planning Studies on Remaining Dams Determine most cost effective solution 65/35 Cost Share (Fed and GASDP Stds) vs. 100% Local (GASDP Stds) Cost to meet GASDP only as little as 10% of cost to meet Fed Std 5 dams RCC overtopping spillways 3 with NRCS Grant 1 Conv. Concrete Labyrinth Weir Chute Spillway over the top of the dam (Y3 to be constructed) 6 dams combination modified earthen aux. spillways and/or wave walls Better planned CIP Funding needs for timing of design and const. Commence Design for all Structures Y14 first to commence construction (2003) 12
Challenges Design Converging Spillways Piedmont Region of GA Narrow, steep stream valleys Convergence beyond tested limits Test Studies Conducted Y15 USBR Hydraulics Laboratory County funded H3 USDA ARS HERU Laboratory NRCS funded Better to converge flow in control section Variety of Control Sections Arced Ogee, Straight Broad Crested, Arced Broad Crested, Winged Broad Crested, Sharp Crested Weirs Multi-stage spillways Floodplain Management (No Rise) 13
Challenges Elected Officials and County Administration Briefings, memos, briefings, memos, and more briefings and memos Spillways have never run around. Do we really need to spend this much money? What happens if we don t do anything? Why did we save those O&M Agreements? Can we get out of this? If we fix this once, will we have to go back again? Communication was the key Explain options, benefits, consequences Brief and to the point Funding Initially funded by General Fund Stormwater Utility Funding starting in 2006 BOC final authority on budget Securing Grant Funds 14
Public Acceptance Challenges Multiple Public Meetings Discussed alternatives and get input on selected alternative Aesthetics Exposed RCC not acceptable No exposed concrete preferred Graffiti Vegetative cover on RCC chute steps after Y14 Fish Drain lakes during construction Restock after construction Often Contentious Threatened lawsuits (Y15 and Y16) Assignment of easement offered (Y15) Had to find a champion 15
Land Rights Challenges Flowage Easement Referenced to an elevation (Top of Dam) Some amended to lower elevation Flood Flowage, Ingress/Egress, and O&M Interpreted to allow Construction Upgrades Temp Const/Perm Drainage Esmts where const activities went beyond Flowage Esmt Cost to Cure Construction Contractor Pre-qualification On-site RCC pug mills and staging areas Construction Traffic Water source for RCC Minimizing Change Orders RCC Mtls, Unsuitables, Stone, etc Complaints by local residents Grant administration 16
Yellow River Dam No. 14 (Y14) In a developed subdivision Proposed development in land between exist. aux. spillway and dam Grant funded (65/35 Cost Share) Maintained reservoir levels 3-feet below normal pool during construction (Fish) Interceptor sewer along right abutment GA Power Easement primary access Allowable construction activity coordination Stage RCC Pug Mill, material stockpiles, etc in existing earthen aux. spillway Maintain 50% width clearance Provided off-duty patrol for traffic control Converging spillway with arced ogee weir Construction 2003-2004 (Golder, Thalle) 17
Yellow River Dam No. 14 (Y14) 18
Yellow River Dam No. 15 (Y15) In a developed subdivision Active, uncooperative, and litigious HOA Threatened lawsuits Assignment of easement offered Half Dam length available for overtopping spillway control section Collins Hill Rd d/s and adjacent to dam Grant funded (65/35 Cost share) Model test at BOR Converging spillway with winged broad crested weir, vegetative cover Construction 2007-2008 (Golder, ASI) Construction bundled with Y16 Pug mill adjacent to site 19
Yellow River Dam No. 15 (Y15) 20
Yellow River Dam No. 16 (Y16) In a developed subdivision HOA coordination Took over design from GASWCC Interceptor sewer thru exist. earthen aux. spillway 20-foot wide dedicated access btwn houses Const. access thru lake bed D/S private lake normal pool elev higher than P/S outlet pipe and toe drains 100% local funded Converging spillway with sharp crested weir and vegetative cover Construction 2007-2008 (Schnabel, ASI) Construction bundled with Y15 Pug mill off-site (4-miles away) Fish kill during pre-const lake draining 21
Yellow River Dam No. 16 (Y16) 22
Yellow River Dam No. 17 (Y17) In County Park Park used for HS overflow parking Designed by USACE thru GASWCC Grant funded (65/35 Cost Share) Construction procured and administer by Gwinnett Significant unsuitables at toe of dam from original construction Converging spillway with broad crested weir and vegetative cover Construction 2004-2005 (USACE, Golder, ASI) 23
Yellow River Dam No. 17 (Y17) 24
Operation and Maintenance Other Keys to Program Mowed twice per year and removed debris as needed Annual Inspections Now quarterly No major deficiencies to address other than spillway capacity Instrumentation Remote monitoring being installed to monitor reservoir levels Plan to install on all NRCS Dams Emergency Action Plans Developed for all 14 NRCS Dams Sunny Day and Storm in Progress (PMP) Failure Events Imminent, Potential, and Non-failure Classifications Property Owner listing for notifications Reverse 911 Expanding to private dams 25
Summary Understand Needs/Drivers Benefits, Consequences, and Options Communication Elected Officials Management/Administration Public Planning Identify Funding Sources Concept Planning before Implementation EAPs Operation and Maintenance Keep O&M and Inspections Up to Date Qualified Consultants and Contractors 26
Questions Jonathan Semerjian, P.E. Section Manager Gwinnett Co. Dept. of Water Resources 684 Winder Hwy. Lawrenceville, GA 30045 678.376.6934 jonathan.semerjian@gwinnettcounty.com Gregg Hudock, P.E. Golder Associates 770.496.1893 Gregg_Hudock@golder.com Sam Fleming, P.E. Dewberry 678.537.8627 sfleming@dewberry.com 27