Rivanna Water & Sewer Authority Presentation to City of Charlottesville Workshop South Fork Rivanna Reservoir (SFRR) Dredging Concept Review May 6, 2008  Previous Studies  Other Communities Experience  Cost and Other Considerations  Summary & Conclusion OVERVIEW

Current & Future Conditions Approximately 2.2 million CY of sediment has accumulated in the useable storage portion of SFRR In the 50 year planning period, an additional 3 million CY is projected to be deposited Approximately 5 million CY must be removed over this 50 year period Dredging must continue in perpetuity Results in ~ 100,000 CY of material that must be dredged per year for 50 years plus 75,000 CY per year after 2055

Sediment Volume In Scott Stadium…… The annual dredged material volume would stack up to approximately 26 feet deep. Total dredged material removed over 50 years would fill the stadium roughly 20 times. Carl Smith Center, home of David A. Harrison III Field at Scott Stadium

Safe Yield Urban System Safe Yield is 12.8 MGD based on current useable volume at SFRR and historical voluntary stream releases If nothing is done at SFRR, safe yield will fall to about 8.8 MGD by 2055 due to lost volume If SFRR were restored as closely as possible to original conditions, the Urban System safe yield would be 14.3 MGD Regulators are likely to require additional stream releases and the safe yield would decrease

Many Logistical Uncertainties Where is the removed sediment slurry dewatered and disposed? Can it be disposed at dewatering site or is re-handling and offsite disposal required? Is any of the material marketable? Is land purchase required for dewatering and disposal? Hydraulic Dredging is predictable. Dewatering and disposal of the sediment is not.

2004 Investigations Landowners near SFRR were consulted and no one indicated they would accept 5 million CY of sediment Dredging contractors were contacted to confirm cost estimates for sediment removal at $5 / CY Charlottesville area contractors contacted (including Parham, Faulconer, and A.G. Dillard) –No market for this quantity as topsoil or general fill –Believe that disposal cost would be about $15 / CY depending on distance to disposal site –Many concerns about sediment make-up Confirmed land value with County Assessors Office at $16,500 per acre

Key Decision Pump to adjacent disposal site OR Use onsite dewatering and transport to offsite disposal site –Local Topography (need flat areas) –Available disposal sites adjacent to SFRR Selected Onsite dewatering and transport –Not enough flat terrain adjacent to SFRR –Much more costly –Local roads impacts

Experience of Other Communities Most dredging is done on coastal and navigation projects Large scale reservoir dredging projects are few. Examples: –City of Fairfax Goose Creek Reservoir –Fairfax County Lake Accotink –City of Decatur Lake Decatur

Other Community Experience 200,000 cubic yards of material dredged Pumped into adjacent dewatering/disposal –Approx.15 acre site was cleared –Approx. 70 feet high Was regulated as a dam – Gannett Fleming designed decommissioning Cost $2.44 million in 1997 (~$12/CY) 2 years to complete Current day unit cost would be about $18/CY –Excludes land cost

Fairfax County Lake Accotink Statistics 204,000 cubic yards of material to be dredged Pumped to dewatering/disposal in nearby industrial development –Approx. 3 miles pumping –Material to be used as general fill on industrial site –Project is located in congested urban environment Project will be complete later this year (2 years total) Selected as dredging method to avoid truck traffic Cost $9.5 million (~$47/CY)

Lake Decatur Statistics City has 2 projects One completed by a contractor in 1994 One ongoing project using City forces (started in 2004) City purchased 520 acre site located about 1 mile away for dewatering and permanent disposal –Disposal site is very flat –Used for both projects

Current Lake Decatur Project Statistics About 4.9 million CY of sediment remain and will take 26 years to complete at the current rate City is examining cost to improve pace and shorten time to 5-15 years Estimated remaining cost is $29.7M to $60.3M (~$6-$12 / CY) –Excludes land cost and initial capital cost. Includes some allowance for material reuse. According to Mr. Keith Alexander Director of Water Management

Photo provided by Keith Alexander City of Decatur Director of Water Management

Photo provided by Keith Alexander City of Decatur Director of Water Management

Cost and Other Considerations …..So what does this mean for SFRR??

Almost 1 square mile Dewatering / Disposal Area for Lake Decatur Available continuous flat area near SFRR

Summary Available land for disposal of 5 million CY of sediment adjacent to SFRR is limited –Can not pump to single disposal site like Decatur because very little flat land available near SFRR Land cost in Charlottesville is relatively high Marketability for 5 million CY over 50 years is uncertain Cost for construction of deep sediment disposal facilities like Goose Creek Reservoir will drive costs up dramatically Tree clearing may also be required

Compare to Current Water Supply Plan The current Water Supply Plan including the Expanded Ragged Mountain Reservoir will provide an estimated Urban System safe yield of 18.7 MGD If dredging were implemented, it would provide an estimated Urban System safe yield of only 14.3 MGD. –Dredging in perpetuity is required –An additional project would need to be constructed that provides an additional 4.4 MGD. –Additional cost for repairs in the existing system (such as SHR to RMR pipeline replacement and correcting deficiencies at RMR) would also be required. –Repairs to the existing RMR must be made.

Conclusions “…Gannett Fleming continues to conclude that future discussion of the costs and benefits of dredging as a program for the SFRR would better serve the community if studied in the context of maintenance of the reservoir, considering water quality, recreational, and aesthetic objectives, as opposed to water supply objectives...” (1) Note (1): excerpt from Gannett Fleming Memo dated June 15, 2005

Rivanna Water & Sewer Authority OVERVIEW Thank you……..