Rivanna Water and Sewer Authority

Transcription

1 Revised Draft Rivanna Water and Sewer Authority Water Supply Project S u m m a r y o f R e c o m m e n d e d A l t e r n a t i v e s Prepared by /Vanasse Hangen Brustlin, Inc. O Brien & Gere Engineers, Inc. Ellis & Thorp, LLC May, 2001

2 Table of Contents List of Figures...iii...1 Introduction... 1 Alternatives Recommended for Immediate Implementation Alternate Release at S. Fork Rivanna Reservoir Water Conservation Drought Management Reduce Sediment Load into S. Fork Rivanna Reservoir Four-foot Crest Controls Alternatives for Possible Future Implementation A. Improvements to Efficiency of Existing Water Resources Dredging Eight-foot Crest Controls Use SFRR as a Pumped Storage Reservoir Chris Greene Lake Drawdowns Use Chris Greene Lake as a Pumped Storage Reservoir Use Beaver Creek to Supplement Flows in Mechums R Dredge Sugar Hollow Reservoir Conversion of Ragged Mountain to Pumped Storage Indirect Reuse Growth Management Leak Detection and Control B. Physical Additions to the Existing Water Supply System Groundwater Reservoirs James River Withdrawal at Scottsville Rivanna River Withdrawal Mechums River Withdrawal Regional Cooperation No-Action Conclusions Table of Contents i

3 Appendices...36 Appendix A: Supply Analysis Executive Summary Appendix B: Demand Analysis Executive Summary Appendix C: Analysis of Alternatives Executive Summary Appendix D: UOSA Analysis Bibliography...41 Table of Contents ii

4 Figures Figure No. Description Follows Page 1 Water Supply and Demand Summary of Water Needs Exceedance Curve for SFRR with Alt. Release Exceedance Curve for SFRR with Crest Control Chris Greene Lake 5 Drawdown Chris Greene Lake 10 Drawdown Chris Greene Lake 15 Drawdown Chris Greene Lake 20 Drawdown Exceedance Curve for James R. Withdrawal Exceedance Curve for J. R. W.draw. plus Power Plant Rivanna R. Schematic without Withdrawal Rivanna R. Schematic with Withdrawal Exceedance Curve for 4 Crest Control at Various Releases Safe Yield for 4 Crest Control at Various Releases Table of Contents iii

5 Introduction The following recommendations result from analysis of raw water supply and demand in the Urban Service Area, along with the investigation of possible alternatives to address the identified water supply deficit. In keeping with federal and state regulatory requirements, the strategy proposed in this chapter attempts to meet the short and long-term water demand in the least environmentally intrusive manner, taking into account overall environmental effects, costs, logistics, technical feasibility, and overall project purposes. In some cases, these interests can be best served by implementing partial solutions over time, delaying environmental disturbance and maintaining the maximum amount of flexibility to deal with changing conditions. The recommended strategy involves improvements to the efficiency of existing water resources no wholly new physical additions to the system are being proposed. Each of the alternatives discussed below is described in detail earlier in Analysis of Alternatives (Feb. 2000). An executive summary of that document, as well as summaries of the Supply Report and the Demand Report (both Oct. 1997) are included in the appendices. The following sections provide supplemental information and propose an implementation strategy. Alternatives Recommended for Immediate Implementation The short-term need for additional raw water in the Urban Service area is acute. The Summary of Water Needs presented in the Analysis of Alternatives indicates that demand now exceeds safe yield in the Urban Service Area. This means that during the next severe drought the Rivanna Water and Sewer Authority will have insufficient water supplies to meet demand. Furthermore, the demand and supply projections are currently diverging at a rate of 3 million gallons per day (mgd) per decade, so that by 2010 the safe yield deficit will be 1

6 approximately 3 mgd (see Figure 1). Furthermore, diminishing supply is an equal contributor to increasing demand in causing this divergence. As such, even if demand were not to increase through 2050, the area would face a water supply deficit of roughly 7 mgd (see Figure 2). Accordingly, it is necessary to identify an alternative or alternatives capable of meeting the current deficit, and also able to provide adequate supply throughout the 2050 planning period. We recommend that the RWSA proceed to implement the following alternatives to address the immediate and mid-term water deficit. In the next section of this report, we will discuss other alternatives that may be considered further and implemented, as needed, at some point in the middle or later portions of the planning period. 1. Alternate Release Scenario at S. Fork Rivanna Reservoir Description of Alternative When this study was begun, the study team was informed and understood that SFRR was required as a regulatory matter to release at least 8 mgd at all times. The safe yield of the reservoir was accordingly calculated on that basis. Subsequent investigation has failed to identify any such regulatory requirement, however. Accordingly, the current yield of the reservoir is actually greater than that assumed in the supply study. The difference amounts to 1.6 mgd, if the reservoir is assumed to release at a rate of 8 mgd or at the rate of natural inflow to the reservoir, whichever is less. In other words, when water flowing into SFRR exceeds 8 mgd, a minimum of 8 mgd would be released; if inflow falls to 8 mgd or below, then the release would equal inflow. Correcting the reservoir s stated yield in this way indicates that the immediate, apparent water deficit identified by the Demand Analysis and Supply Analysis can be satisfied in the very short term by the SFRR. Furthermore, there would likely be no practical consequence to restating the reservoir s yield in this way. The scenario would occur only on those rare occasions when the water level falls below the top of the dam. Anecdotal evidence suggests that this has happened only 2 or 3 times since the dam was constructed in Furthermore, once a source of additional supply is obtained, the RWSA could of course adopt or accept a prescribed minimum release. Even if a severe drought should occur before a new water source is brought on-line, the natural river flow would simply be passed downstream without augmentation. 2

7 Water Supply and Demand Water Demand Projection ( ) Demand/Supply (MGD) Water Demand ( ) Water Supply Projection Year Figure 1

8 Summary of Water Needs Demand/Supply (MGD) Water Demand Projection Water Supply Projection Increase in Existing Demand Existing Demand Decrease in Existing Supply Year Figure 2

9 Effectiveness The revised release would provide 1.6 mgd in additional safe yield. It could thus meet the needs of the Urban Service Area over the next 1-2 years, until a longer-term solution is available. Practicability/Cost The cost for this alternative is quite low at $386,000, for a unit cost of $0.24/gallon. This accounts for installation of necessary gauges as well as valving and controls at the SFRR dam. It may be possible to utilize existing gauges, thereby lowering the total cost slightly this potential should be investigated. Environmental The revised release would actually be implemented only when a severe drought occurs. At such times, the release from the reservoir would equal the inflow to the reservoir. In other words, streamflows would be at their natural levels during such droughts, rather than being augmented from reservoir storage. The temporary nature of the revised release, combined with the infrequency of its use (only during rare and severe droughts), minimizes the impact to downstream flow. Figure 3 shows the flow exceedance curves for the South Fork Rivanna River downstream of the dam, with and without this alternative. The curves demonstrate the percentage of the time that flows exceed a given level. As shown, the w/o Project line ends at 8 mgd, reflecting the previously assumed required release, while the w/ Alternate Reservoir Release line drops below 8 mgd. Except for the very highest percentages, the flows are similar; for instance, river flows without the project exceed 20 mgd roughly 93% of the time. With the project, river flows exceed 20 mgd roughly 91% of the time. Furthermore, with the project, flows drop below 8 mgd less than 1% of the time. During design of the valving system, the potential for mixing surface and bottom water, to optimize temperature and oxygen levels, should be investigated. Recommendation Although designated as an alternative in this report, restating the yield of SFRR really amounts to correcting the yield stated in our original Supply Analysis to reflect the absence of the previously-assumed 8 mgd constant release, and an assumption that RWSA nevertheless would voluntarily commit to release either 8 mgd or natural inflow, whichever is less. We recommend this alternative be selected at least as a temporary measure, until another alternative is available to meet longer-term demand. It is one of the very few measures that could be implemented and meet system demand if a drought were to occur in the immediate short-term. Furthermore, the only environmental effect would be a 3

10 Flow Exceedance Curve for South Fork Rivanna Reservoir Downstream of Dam Downstream Flow (mgd) Period of Record: Oct.1,1929-Sept.30, w/o Projects (Existing Conditions) Exceedance Percentage w/ Alternate Reservoir Release Figure

11 temporary return to natural streamflow conditions downstream from the dam during severe droughts. 2. Water Conservation Description of Alternative This alternative consists of immediate development and implementation of a water conservation plan for the Urban Service Area. The resulting water conservation can be monitored, and its effectiveness documented and assessed over time. The safe yield benefit suggested herein is based on evidence from other programs, but it is possible that greater savings (or lesser) could be achieved, thereby postponing (or hastening) the need for longer-term measures outlined below. Implementation of this alternative would consist of developing a plan to take advantage of water savings resulting from a variety of measures, including plumbing fixture changeout, public education, industrial conservation, and conservation pricing. Effectiveness The Analysis of Alternatives concludes that voluntary conservation measures can reduce demand in 2050 by approximately 1.7 mgd (8% of 2050 total demand). Because a variety of factors will affect the program s success, an exact figure cannot be calculated. The effectiveness of this alternative should be monitored over time, so that the long-term benefit can be estimated. It is important to realize that the 1.7 mgd is based on 2050 water demand; benefits will be proportionately less in the short term. Since publication of the Analysis of Alternatives, additional case studies of conservation have been analyzed. The results highlight the variable results of different programs, and underscore the need to implement and monitor conservation over time. ΠΠAccording to the Water Resources Department in Asheville, North Carolina, the drought in resulted in a phased plan that included voluntary conservation as well as mandatory restrictions (treated as Drought Management in this report). The cumulative impact of those conservation and drought management efforts was a 25% short-term reduction in commercial/industrial/institutional usage and a 14% short-term reduction in residential usage (City of Asheville web page, 8/23/00). The Analysis of Alternatives treats voluntary conservation and mandatory restrictions as distinct alternatives, and suggests that their cumulative impact is 4.1 mgd (1.7 from conservation and 2.4 from drought management), or roughly 21% of total 2050 demand. The City of Greensboro, North Carolina, implemented a voluntary drought management program in In , in response to 4

12 drought conditions, the City used increased publicity and other elements to encourage additional short-term reductions in demand. The City used 20% less water in December 1998 than December 1997 (City of Greensboro web page 8/23/00). ΠIn 1991, the Irvine Ranch Water District in southern California implemented a conservation program that includes water budgeting (with price incentives), education, and installation of low-flow plumbing fixtures. Between 1991 and 1998, residential water use dropped by 13% (New Mexico Water Conservation Alliance, spring 1999). Practicability/Cost The cost for this alternative is estimated to be $2.5 million, excluding any potential reduction in revenues due to lower sales. This amounts to an overall unit cost of $19.23/gallon. However, the cost is attributable to the public education component, while most of the yield is attributable to plumbing changeout. This suggests the public education component may not be cost-effective. Environmental No negative environmental effects of water conservation were identified. Recommendation Water conservation measures can reduce demand and some measures can be cost-effective. Accordingly, we recommend immediate development and implementation of a water conservation plan and efforts to monitor its effectiveness over time. If measures should prove more successful than our investigation has assumed, that would make it possible to delay implementation of other, longer-term alternatives. Conversely, if water conservation techniques are less effective than our projections, subsequent components of a long-term water supply solution could be accelerated. This eventuality may also necessitate reevaluation and modification of the conservation program. 3. Drought Management Description of Alternative Drought management techniques consist of various voluntary and mandatory measures to reduce water use during drought conditions. These techniques are explained in greater detail in the Analysis of 5

13 Alternatives. The City of Charlottesville and Albemarle County both adopted drought management ordinances during the summer of Effectiveness It is estimated that these measures could provide the equivalent of 2.4 mgd of supply during a drought in As with conservation, the short-term benefit would be less, and the effectiveness of the program should be monitored over time. Practicability/Cost This alternative is actually comprised of two measures demand side and supply side management. The cost for demand side drought management is $250,000, for a unit cost of $0.18/gallon very low. Supply side measures involve modifications to system operations and procedures and the related costs would be difficult or impossible to quantify. However, any such costs are assumed to be reasonable. Environmental No negative environmental effects of drought management were identified, apart from loss of vegetation that may result from restrictions on outdoor water use (lawn watering) during droughts. Recommendation Drought management techniques provide a practicable, cost-effective and environmentally sound means of extending existing water supplies. Accordingly, we recommend immediate development and implementation of a drought management plan, including means to assess its effectiveness over time. 4. Reduce Sediment Load into S. Fork Rivanna Reservoir Description of Alternative To date, Albemarle County has utilized an array of techniques to reduce sedimentation in the SFRR watershed. These include: zoning regulations, construction of stormwater best management practices (BMPs), riparian buffer requirements, erosion and sediment control regulations, voluntary agricultural cost share programs, and forestry BMPs. It is possible that these efforts have prevented the rate of sedimentation from increasing over time (the actual rate has been less 6

14 than originally predicted prior to construction of the reservoir). Their actual effect is impossible to quantify at present. The Analysis of Alternatives provides a timeline of watershed management initiatives. The County s current program results from the 1998 enactment of the Water Protection Ordinance. According to the Albemarle County Department of Engineering & Public Works, the methods used to control sedimentation in the County are as follows: ΠΠΠUpland BMPs Stormwater treatment via BMP is required for all new development; BMPs are discussed in the Interim Design Manual. Though the County s keystone pollutant is phosphorus, BMPs normally capture sediment in an effort to remove bound phosphate. Multipliers in the procedure for calculating the phosphorus removal requirement lead to higher removal requirements in the water supply watersheds than in other areas. Stream Buffers Stream buffers are a special case of BMP. Stream buffers are required in Albemarle County Code using the Virginia Chesapeake Bay Preservation Act as the enabling legislation. In the SFRR watershed, buffers are required around both perennial and intermittent streams (as delineated by County staff) on all development sites. This program is most forcefully applied to new development. Buffers on previously developed sites are addressed through education and enforcement of violations. Twenty five feet buffers and conservation plans are required on cropland bordering perennial streams. For pasture land, County and Soil and Water Conservation District staff feel that the Agricultural Stewardship Act is a more effective way to correct bad actor situations. For forestry practices, the County s ordinance exempts silvicultural operations as long as forestry BMPs are followed. There is also a state law, administered by the Department of Forestry, which addresses bad actor cases. Erosion and Sediment Control The County s Erosion and Sediment Control (E&S) program regulates active development sites. This program is required by state law and overseen by the Department of Conservation and Recreation. The E&S program is staffed by three field inspectors, two plan reviewers, and one supervising engineer. The program is applied to the entire County. Because the SFRR watershed is roughly one-third of the County and there are six staff members in the program, the equivalent of two staffers are available for SFRR E&S review and enforcement. (Quoted from memo of May 15, 2000) This comprehensive approach to sediment control, the high percentage of forest cover in the watershed (73%), and the continuing rate of sedimentation raise the possibility that the SFRR is receiving natural 7

15 amounts of sedimentation from its large watershed. Furthermore, it is possible that most of the sediment delivery to the SFRR occurs during rare large storms. Given these factors, significant reductions in sediment input to the reservoir could prove extremely difficult. As originally described, this alternative consisted of constructing additional regional stormwater management ponds (similar to the Lickinghole Creek BMP) and modification to the County s riparian buffer policy. A number of factors have resulted in changes to this strategy. First, the regulatory agencies have made it clear that in-stream stormwater management ponds have significant negative environmental effects and are not a preferred alternative. The BMP focus has therefore shifted to forebays at the headwaters of the SFRR. Forebays are similar to stormwater ponds, but they would be constructed immediately upstream of the reservoir. Forebays are generally shallow, wide, and naturally vegetated; they would trap sediment at the head of the reservoir, concentrating the material in a contained area from where it could be periodically dredged. Like other BMPs, they can only remove a certain percentage of sediment, and they require periodic maintenance in the form of dredging. Second, the prevalence of forested buffers throughout the watershed and the County s active buffer program have indicated that overland flow is one contributor (but not the major contributor) to reservoir sedimentation. It appears possible that stream bank erosion is a more dominant factor, and this alternative therefore includes investigation of the potential for targeted stream restoration. However, it may also prove possible to enhance Albemarle s buffer program, and this alternative retains the need to investigate this possibility. Because the potential effectiveness of reducing sediment inputs to the S. Fork Rivanna Reservoir would require long-term study spanning decades, this alternative now is limited to beginning the necessary baseline studies discussed herein. This includes analysis of the potential for forebay construction, stream classification, and buffer enhancement. Effectiveness The dynamics of sediment transport and capture make the effectiveness of these measures impossible to quantify at present. Nevertheless, it appears plausible that past efforts have prevented an increase in the rate of sedimentation over time, and that future efforts could accomplish a similar objective. Forebays Construction of forebays has the potential to reduce, but not eliminate, sedimentation into the SFRR. Like upstream stormwater management ponds, individual forebays are estimated to have a 40% sediment removal efficiency. It is important to emphasize, however, that it would 8

16 prove impossible to treat the entire volume of water entering the reservoir, and that the bulk of sedimentation may well occur during dramatic storm events. The above efficiency therefore does not imply that forebays could reduce the total sediment load into the reservoir by 40%. Furthermore, the large size of the watershed is a contributing factor, and could diminish the overall effectiveness of forebays. Stream Restoration It is possible that identifiable segments of eroding stream banks are contributing a significant portion of the sediment load, particularly during large storm events. Restoration of erosion hot spots has the potential to reduce the overall loading into the reservoir. Natural erosion is one issue that warrants careful analysis here; based on hydrologic and geologic conditions, streams will carry a certain amount of sediment. Stream bank restoration in one area could possibly result in creation of an erosion problem downstream, as the stream attempts to pick up its natural sediment load. Practicability/Cost Forebays The cost of forebay construction would depend on the actual locations and sizes of the facilities, and a detailed analysis would be necessary to determine the most cost-effective approach to construction. This discussion assumes construction of 2 forebays one at the head of the reservoir below the confluence of the Mechums, Moorman s, and Buck Mountain Creek, and one where Ivy Creek enters the reservoir. The total estimated cost to design and construct the forebays is $232,000. Clean out maintenance could occur periodically, every 2-3 years; costs for these activities equates to an annual cost of roughly $46,000. Because no safe yield can be assigned reliably to this alternative, no unit cost can be calculated. Stream Restoration Given the number of possible locations and various scales of possible restoration sites, as well as the inability to quantify their potential effectiveness, no costs were assigned to this option. Environmental Forebays The impact of constructing sediment forebays would depend on the exact location, size, and design of the facilities. Possible effects include the loss of wetlands, but the extent of that impact would depend on the variable factors described above. No cost for wetland mitigation was included; however, depending on specific location, mitigation may be required. 9

17 Stream Restoration As part of a stream classification effort, restoration could have a positive impact, by addressing erosion hotspots. Recommendation All practical efforts to reduce sediment inputs to S. Fork Rivanna Reservoir should continue, as they might prolong the useful life of the reservoir and obviate future dredging. Accordingly, we recommend this alternative be pursued immediately as a supportive measure, and that its effects be monitored. We also recommend that additional measures, such as stream bank restoration, construction of reservoir forebays, and an enhanced riparian buffer program should be investigated further, even though their effectiveness cannot be quantified at this time. Additional studies (for instance to assess the potential for stream bank restoration) and periodic bathymetric surveys would help to determine whether the strong sediment control program currently in place could effectively be enhanced. 5. Four-foot Crest Controls Description of Alternative This alternative would involve installation of an inflatable bladder on the SFRR dam, in order to increase the reservoir pool height by 4, thereby adding storage capacity to the reservoir. A similar bladder was recently installed on the Sugar Hollow dam. Previous dam stability analyses indicated that the SFRR dam with 4 crest controls would comply with Virginia dam safety regulations. This alternative will likely require some land acquisition, although the exact amount is uncertain and will require additional investigation. For the purposes of this analysis, it is assumed that up to 100 acres would be required. Also, replacement of the Route 676 bridge over Ivy Creek may be required. We have consulted with VDOT but do not yet have definitive information as to whether the bridge must be replaced or how the associated costs might be allocated. The raised pool level would impact the location of any proposed sediment forebays, and their exact location would require site specific analysis. Effectiveness This alternative is estimated to provide approximately 35 years of additional supply, based on current demand projections and sedimentation rates. The crest controls would provide 7 mgd additional safe yield in This safe yield figure accounts for additional sedimentation over time. The immediate increase in safe yield upon completion would be approximately 11 mgd. If the rate of sedimentation 10

18 decreases, or if water conservation or drought management techniques should prove more effective than we have estimated, then this alternative may meet future water needs of the Urban Service Area for an even longer period. Practicability/Cost This alternative has a relatively low base cost of $2.26 million, for a unit cost of $0.32/gallon. It makes use of existing water treatment and transmission facilities and extends the useful life of the existing S. Fork Rivanna Reservoir. These cost figures assume no land purchase or bridge replacement. During the initial investigations into this alternative, it was assumed that the City of Charlottesville owned property to an elevation of 387 adequate for the proposed 386 pool level. It now appears that this may not be the case in all sections of the reservoir, particularly in the upper reaches of the SFRR. Given the uncertainty of the extent of City ownership, it appears likely that some property acquisition will be required. Although the exact amount could only be determined by extensive field surveys, we estimate the amount to be approximately 100 acres. This estimate is based on examination of topographic maps, as well as anecdotal evidence. The number is subject to the limitations of the topographic maps and their associated scale and topographic interval. Nevertheless, we believe this to be a reasonable estimate of the order of magnitude of the likely acreage. Using a land value of $13,000 per acre, this would increase the cost of the alternative by roughly $1.3 million. This per acre figure is somewhat higher than the average land value used for other alternatives, reflecting the potentially higher value of property fronting on the reservoir. Additional purchases of land for flood easements would not in general be required, since the bladder allows for control of the water level, and would be deflated accordingly in the event of a flood. Should replacement of the Ivy Creek bridge be required, the cost of the alternative would increase by approximately $2 million. The estimated land purchase and the bridge replacement would therefore increase total cost to roughly $5.6 million, for a unit cost of $0.80/gallon. These costs are still relatively low in comparison to other alternatives. This cost assumes mitigation for 5 acres of wetlands impacts, as described below. However, it is possible that no mitigation or mitigation for an additional 13 acres of reservoir perimeter wetlands could be required. Accordingly, the cost of this alternative could vary from just over $5 million to almost $7 million (including land and bridge costs). Initial investigations into this alternative identified 2 potential residential displacements, based on mapping analysis. Preliminary field investigations have failed to identify these structures, and costs are not included for their purchase. Furthermore, such structures would not be expected significantly to impact the total cost. Mapping analysis also identified potential archaeological resource impacts that would require 11

19 further investigation. Again, this is not expected significantly to impact total cost or feasibility. Environmental The Virginia Department of Game and Inland Fisheries conducted an intensive mussel survey in the vicinity of and upstream of the proposed pool level. Their written analysis concludes that 4 crest controls would have no impact on the James spinymussel. Increasing the pool elevation of the reservoir by 4 would inundate approximately 18 acres of wetlands. Approximately 13 acres of these are wetlands that have developed spontaneously around the perimeter of the existing reservoir; following establishment of the new pool elevation, wetlands similar in nature and greater in extent (due to the larger perimeter) would likely develop. Accordingly, this alternative would have long-term impacts to approximately 5 acres of wetlands. These impacts could be offset through appropriate mitigation. If the regulatory process should require mitigation for the full 18 acres, the cost of this alternative would increase, as discussed above. Alternatively, it is possible that this alternative will not require a permit and associated regulatory oversight, thereby lowering the mitigation cost. Figure 4 shows the flow exceedance curves with and without the project. As can be seen, river flows without the project exceed 20 mgd roughly 93% of the time. With the project, river flows exceed 20 mgd roughly 89% of the time. With the project, flows do not fall below 8 mgd, reflecting the proposed establishment of an 8 mgd constant minimum release from SFRR. Recommendation We recommend that RWSA immediately pursue design and preparation for installation of 4 crest controls. This alternative would provide significant water supply into the middle of the planning period, is costeffective, and has limited environmental impacts that may be effectively offset. Alternatives for Possible Future Implementation The above alternatives would provide sufficient water supply to meet immediate and mid-term needs. Nevertheless, demand through the 2050 planning period is expected to exceed the safe yield of the improvements discussed above, necessitating additional supply. 12

20 Flow Exceedance Curve for South Fork Rivanna Reservoir Downstream of Dam Downstream Flow (mgd) Period of Record: Oct.1,1929-Sept.30, w/o Projects (Existing Conditions) Exceedance Percentage w/ Crest Control Figure

21 Two alternatives using Chris Greene Lake for water supply purposes and dredging of SFRR appear to offer the most promise, while others appear not to be part of a practicable solution based on analysis to date of effectiveness, costs, and environmental impacts. The following sections assess and offer recommendations with respect to each of these remaining alternatives. A. Improvements to Efficiency of Existing Water Resources 1. Dredging Description of Alternative The dredging alternative consists of removing and disposing of some or all of the accumulated sediment in the upper and middle reaches of the SFRR. The reservoir is currently losing storage capacity due to siltation at a rate of approximately 13 million gallons per year, and this alternative includes two options for addressing this issue and increasing the long-term safe yield of the reservoir. The first option involves a one-time dredging event sometime prior to This action would return the reservoir to roughly its original storage capacity; thereafter sedimentation would continue and yield would diminish. The second option involves annual maintenance dredging to maintain the current yield of the SFRR. Both options would result in similar safe yield increases in Effectiveness In theory, dredging could be an effective means of restoring water storage capacity and therefore yield to the SFRR. Dredging could be structured to provide various safe yield increases (based on the volume of material removed from the reservoir). As currently described, this alternative would return or maintain the current safe yield of 7.2 mgd. Practicability/Cost Additional research performed concerning this alternative subsequent to our prior evaluation has included contacting several additional dredging contractors to solicit cost estimates. This investigation uncovered a wide range of possible costs; the original estimate in the Alternatives Evaluation is within that range. 13

22 To demonstrate the wide range of possible costs, two scenarios are outlined here both assume pumping dredged material to a site in the immediate vicinity of the reservoir (approximately the same distance in both cases). If the pumping distance were increased to the extent that an intermediate pump station were required, the cost of both scenarios would increase by $1.5 million. The first scenario assumes a one time dredging event, around year 2020, with permanent disposal at an upland site that requires a degree of construction to contain and dewater the sediment. In order to achieve 7.2 mgd in safe yield, 3.07 million cubic yards of sediment would need to be dredged (assuming siltation rates remain constant). The total cost for such an event is approximately $40 million, as detailed below, amounting to a unit cost of $5.56/gallon. The percentage costs for fees and contingencies are included in the cost of all alternatives they are shown here as line items for clarity. ΠΠΠΠΠΠΠΠΠLand purchase....$2 million Earthen dams... $2 million per cubic yard.... $21.5 million Wetland mitigation.$800,000 Improvements to WTP... $3 million SUBTOTAL..$29.3 million Eng., legal, admin. fees 15%...$4.4 million Contingencies 20%..$5.9 million TOTAL..$39.6 million This scenario uses an average value for dredging cost per cubic yard, and assumes that a single upland site could be purchased and developed for this purpose. As such, this represents the low end of the possible cost range. The appropriate site would consist of roughly 180 acres, and contain ravine topography with limited wetlands. Construction would be limited to earthen dams at the head and foot of the spoil site, utilizing steep slopes to contain the bulk of the material. Given the topography in the vicinity of the reservoir, several such sites could be available. A second scenario assumes that disposal options prove more restricted, and that spoil material has to be dewatered at a temporary site and then hauled to a permanent location. The following figures assume a 25-acre drying site, on which 8 high earthen dikes are constructed to contain sediment at a depth of 6. Such a site would be capable of containing approximately 240,000 cubic yards of sediment. Assuming 13 dredge events over 8 years (allowing roughly six months dewatering time for each event), the full 3 million cubic yards could be handled. The total cost under these conditions is approximately $75 million, as detailed below, for a unit cost of $10.42/gallon. ΠΠΠΠΠΠΠLand purchase $275,000 $17 per cubic yard.$52.2 million Improvements to WTP..$3 million SUBTOTAL.$55.5 million Eng., legal, admin. fees 15%. $8.3 million Contingencies 20%.$11.1 million TOTAL. $74.9 million 14

23 This estimate is closer to the original amount detailed in the Alternatives Analysis, and represents the upper end of the possible range. It should be noted that the time factor associated with this option could significantly increase its cost. In particular, if dredging equipment and piping could not be stored on-site during drying periods, mobilization and start up costs could be prohibitive. Site characteristics in this option include a relatively flat, upland site, requiring significant construction in the form of earthen dikes. Although the land surrounding the reservoir generally consists of rolling topography, several relatively level areas along ridgetops could be available to meet the requirements of this option. Annual maintenance dredging, as described in the Alternatives Evaluation, remains a possible solution. This option includes land purchase of approximately $2.2 million, infrastructure costs of approximately $5 million, and annual dredging, dewatering, and disposal costs of $800,000. The total cost through 2050 would therefore be roughly $47 million, or $6.53/gallon. Each of these scenarios assumes that the spoil material must be disposed of. If a beneficial use could be found for some or all of the material, costs could be reduced accordingly. In fact, depending on the use, grant funding may be available to assist with total cost. The amount of grant funding available could be very limited, however, and account for only a small portion of total project cost. Furthermore, given the large amount of material in question, finding beneficial uses for a substantial portion could prove difficult. Environmental The dredging activity itself, including equipment access and staging, would temporarily impact wetlands and shallow water habitat. In addition, additional impacts to shallow water habitat are expected in areas where accumulated sediment is removed. The first disposal scenario is also likely to involve permanent wetland impacts, and mitigation costs are factored in for impacts to approximately 9 acres. Dredging would also temporarily resuspend bottom sediments and organic detritus. Costs are included for temporary increases in water treatment resulting from this disturbance. Loss of upland farm land or wooded habitat would also result from this alternative. Recommendation For now, we recommend that RWSA make every reasonable effort to control sedimentation to the reservoir and conduct bathymetric surveys every 5 years to monitor sedimentation rates over time. Actual rates of siltation will help determine the need for, the scale of, and the timing of 15

24 dredging. This alternative offers the potential to increase safe yield over the longer-term, but has a higher unit cost and greater environmental impacts than the alternatives recommended herein for immediate implementation. 2. Eight-foot Crest Controls Description of Alternative This alternative is similar to the 4 crest controls discussed above, but would raise the reservoir pool level by 8. This action would require more extensive land purchases and would definitely require bridge replacement. Effectiveness The 8 crest controls would provide 11 mgd in additional safe yield in Practicability/Cost At $18.3 million ($1.66/gallon), the cost for this alternative is moderate, although it is significantly higher than the 4 option due in part to land purchase and other costs associated with the higher water level. Environmental This alternative would impact approximately 39 acres of wetlands, of which 13 have developed around the reservoir perimeter and could be expected to be replaced by wetlands forming at the new pool level. Accordingly, the 8 crest controls involve permanent impacts to 26 acres of wetlands. The cost analysis presumes that mitigation would be provided for these impacts. Additional investigation would be necessary to assess the potential impacts to the James spinymussel in Ivy Creek based on the higher pool elevation. Recommendation This alternative provides significant safe yield to meet the water supply needs of the Urban Service Area. However, it has a higher unit cost and greater wetland impacts than the 4 version, as well as potential impacts to the James spinymussel. Accordingly, this alternative is not recommended as a component of the water supply solution at this time. 16

25 3. Use SFRR as a Pumped Storage Reservoir Description of Alternative This alternative consists of withdrawing water from the Rivanna River and pumping it to the SFRR. It includes construction of an intake and pump station on the Rivanna River just downstream of the confluence of the North and South Forks. Effectiveness Using SFRR as a pumped storage reservoir is not practical due to lack of storage capacity in the lake during non-drought conditions and lack of sufficient flow in the Rivanna River during those times when storage is available. It would therefore provide no increase in safe yield. Practicability/Cost No costs were developed due to the impracticability of this alternative. Environmental This alternative would have minimal environmental impacts. Recommendation This alternative would provide no safe yield, and we do not recommend that it be included as part of a practicable solution at this time. 4. Chris Greene Lake Drawdowns Description of Alternative This alternative involves use of water in Chris Greene Lake to supplement the water supply system during periods of drought. The Analysis of Alternatives described two versions of this measure a drawdown of up to 5 and a drawdown of 20. Supplemental investigations have detailed the safe yield of 10 and 15 drawdowns, and have identified the frequency at which each of these events would occur. For all of these versions, water would be piped directly from the lake to the North Fork water treatment plant in order to prevent pump damage and maintenance problems that presently result from the intake 17

26 of suspended sediments in the North Fork Rivanna River at higher pumping rates. In addition, in order to describe an alternative that would take advantage of the existing 2 mgd treatment capacity of the North Fork Treatment Plant, to the extent that it is practicable to do so, while avoiding major infrastructure costs associated with other variations of this alternative, a drawdown of 0.5 utilizing a direct stream release was analyzed. This represents the maximum use of the existing North Fork facilities that is feasible given existing constraints on pump usage and maintenance. However, there is insufficient water demand presently for use of this water in the northern segment of the Urban Service Area, and infrastructure does not currently exist for distributing this water to the main portion of the service area to the south. Effectiveness The various drawdowns provide additional safe yield as follows: ΠΠΠΠΠmgd mgd 10 4 mgd mgd mgd Practical difficulties associated with capturing the released water and limited demand in the northern portion of the Urban Service Area at present minimize the overall effectiveness of the 0.5 option. Specifically, drawing higher volumes of water through the North Fork intake results in damage to the pumps, because rocks and other debris are drawn in along with the water. The estimated 0.7 mgd increase in safe yield results from an estimate of the upper end of the range of water that can effectively be withdrawn. However, there is no need for this water at present in the northern portion of the Urban Service Area and it would have to be transmitted south, involving additional infrastructure expense, to be beneficial to the system. Practicability/Cost The total costs for 0.5 option is low, while the other variations are moderate to relatively high in comparison to other alternatives: Π$500,000 Π5 - $12.8 million Π10 - $15.5 million Π15 - $17.8 million Π20 $20.1 million As stated above, the 0.5 option would utilize existing treatment capacity, and would require limited infrastructure improvements to serve the North Fork service area. The $500,000 estimate covers the cost 18

27 for control and gauging improvements at the dam, as well as valving improvements in the North Fork distribution system. Costs for the other options include the additional infrastructure necessary to transport the water from Chris Greene Lake south to the primary portion of the Urban Service Area, where the vast majority of the water demand is located. These improvements would consist of roughly 6 miles of 24 water main from the North Fork water treatment plant to the vicinity of the South Fork water treatment plant, at an estimated cost of $5.4 million. For the 5 drawdown, this increases the total project cost by 73%, and for the 20 option by 37%. This additional cost was not included in the original estimate, and is not reflected in the Alternatives Matrix. It is possible that a portion of these costs could be borne by the Virginia Department of Transportation, as part of the Route 29 improvement project. It is possible that long-term growth could increase demand in the North Fork service area. If this proves to be the case, use of Chris Greene Lake for water supply purposes could become more cost-effective as it would not be necessary to transfer this water further south. As drawdown levels increase above the 0.5 option, the unit cost and total project cost increases substantially, because of the improvements necessary to treat the additional volume of water at the North Fork plant, which currently has only 2 mgd of treatment capacity. For the 20 option, these improvements would cost $13.25 million (66% of the 20.1 million total). In contrast, the 4 crest control alternative would utilize existing capacity at the South Fork treatment plant. Although using Chris Greene Lake for water supply may not be cost-effective at this time, some version of this alternative may become attractive in the future, depending upon whether and to what extent demand in the northern portion of the Urban Service Area increases in the future. The total cost of this alternative could increase further if Albemarle County were required to replace any impacted recreational facilities, which were constructed at Chris Greene Lake using Land and Water Conservation Funds. If recreation of any kind were eliminated or suspended, Albemarle County would have to develop a replacement facility of equal recreational usefulness as determined by the State Comprehensive Outdoor Recreation Plan. Although the value of the recreational facilities at the lake is uncertain, recent recreational improvements made by the County at Walnut Creek and Darden Towe Memorial Park suggest that replacement could cost approximately $4 million. Environmental One of the primary issues with the drawdown alternatives is the impact to recreation (fishing, swimming, and boating) and fish stocks at Chris Greene Lake. According to the Virginia Department of Game and Inland Fisheries, paid attendance at the lake is approximately 20,000 people per year. This figure does not account for full attendance, because the fees are only in effect for a certain part of the year, and then only during 19

28 certain hours of the day. DGIF has further indicated that drawdowns in excess of 5-7 could result in severe predation of that year s fish fry, resulting in significant decline of the year s stock. The frequency of these events would be roughly once per decade. The durations of the drawdowns are shown in Figures 5-8. The Virginia Department of Health has raised concerns about allowing of primary contact recreation (swimming) should the lake be utilized for water supply purposes via the direct pipeline method described in the Alternatives Evaluation. Given the practical difficulty of capturing the water in the stream release option and existing pump damage and maintenance issues at higher pumping rates, the direct pipeline represents the only way to assure access to the safe yield provided by the drawdown. In a written response, the VDH has raised the possibility that use of the lake for water supply could result in prohibition of all primary contact recreation. This would represent the loss of a significant community amenity, and could also have cost implications, as discussed above. Finally, lowered pool levels would temporarily impact wetlands and submerged vegetation, but are not anticipated to have long-term impacts. Pipeline construction could result in impacts to less than 1 acre of wetlands. Recommendation Drawdowns at Chris Greene Lake offer a potentially viable future alternative, especially if and when demand should increase in the northern end of the service area. Currently, little demand exists in the northern area (less than 0.3 mgd), and the cost for treating and transporting water from Chris Greene Lake to the south makes this alternative less attractive in the short term. Utilization of the 0.5 drawdown should be seen as a potential emergency measure during severe drought periods. The difficulties associated with withdrawal using the direct stream release and the lack of demand for the resulting yield in the northern portion of the service area make full time use of this option impracticable at present. Significant impacts to recreation and fish stocks would also accompany the versions of this alternative with higher drawdowns and yields. Given the higher costs, smaller yield, and negative impacts to fish stocks and recreational amenities associated with higher drawdowns and yields, implementation of 4 crest controls is a better candidate for immediate implementation than using Chris Greene Lake. Immediate implementation of the 5 drawdown version of this alternative would involve much greater costs and provide only about 15 years of additional supply. That is insufficient time to fully assess reservoir sedimentation rates and controls, and the alternative would do nothing to extend the 20

29 Water Stage(ft) Chris Greene Lake Water Levels Based on Drawdown Up To 5 Feet (Record Period: 10/01/ /31/1989) Days below 423 Feet Minimum 1 Day Level of Feet Days below 423 Feet 56 Days below 420 Feet Minimum 1 Day Level of Feet 65 Days below 423 Feet 18 Days below 420 Feet Minimum 1 Day Level of Feet /1/29 10/1/34 10/1/39 10/1/44 10/1/49 10/1/54 10/1/ Days below 423 Feet Minimum 1 Day Level of Feet 51 Days below 423 Feet Minimum 1 Day Level of Feet /1/60 1/1/65 1/1/70 1/1/75 1/1/80 1/1/85 Figure 5

30 Water Stage(ft) Chris Greene Lake Water Levels Based on Drawdown Up To 10 Feet (Period of Record: Oct.1, 1929-Dec.31, 1989) Days below 423 Ft 39 Days below 420 Ft Minimum 1 Day Level of Ft Days below 423 Ft Minimum 1 Day Level of Ft 75 Days below 423 Ft 36 Days below 420 Ft Minimum 1 Day Level of Ft 38 Days below 423 Ft Minimum 1 Day Level of Ft Days below 423 Ft Days below 420 Ft Minimum 1 Day Level of Ft 10/1/29 10/1/34 10/1/39 10/1/44 10/1/49 10/1/54 10/1/ Days below 423 Ft Minimum 1 Day Level of Ft Days below 423 Ft 24 Days below 420 Ft Minimum 1 Day Level of Ft /1/60 1/1/65 1/1/70 1/1/75 1/1/80 1/1/85 Figure 6

31 Water Stage(ft) Chris Greene Lake Water Levels Based on Drawdown Up To 15 Feet (Period of Record: Oct.1, 1929-Dec.31, 1989) Days below 423 Ft 38 Days below 420 Ft Minimum 1 Day Level of Ft 44 Days Below 423 Ft Minimum 1 Day Level of Ft Days below 423 Ft 187 Days below 420 Ft 83 Days below 410 Ft Minimum 1 Day Level of Ft 79 Days below 423 Feet 53 Days below 420 Feet 8 Days below 410 Feet Minimum 1 Day Level of Feet /1/29 10/1/34 10/1/39 10/1/44 10/1/49 10/1/54 10/1/ Days below 423 Ft 33 Days below 420 Ft Minimum 1 Day Level of Ft /1/60 1/1/65 1/1/70 1/1/75 1/1/80 1/1/85 Figure 7

32 Water Stage(ft) Chris Greene Lake Water Levels Based on Drawdown Up To 20 Feet (Period of Record: Oct.1, 1929-Dec.31, 1989) Days below 423 Ft 52 Days below 420 Ft Minimum 1 Day Level of Ft 229 Days below 423 Ft 212 Days below 420 Ft 105 Days below 410 Ft Minimum 1 Day Level of Ft 80 Days below 423 Feet 61 Days below 420 Feet 20 Days below 410 Feet Minimum 1 Day Level of Feet 44 Days Below 423 Ft 11 Days Below 420 Ft Minimum 1 Day Level of Ft /1/29 10/1/34 10/1/39 10/1/44 10/1/49 10/1/54 10/1/ Days below 423 Ft Minimum 1 Day Level of Ft 90 Days below 423 Ft 50 Days below 420 Ft Minimum 1 Day Level of Ft /1/60 1/1/65 1/1/70 1/1/75 1/1/80 1/1/85 Figure 8

33 useful life of the SFRR. Accordingly, we recommend reserving this alternative for possible future implementation after 4 crest controls. 5. Use Chris Greene Lake as a Pumped Storage Reservoir Description of Alternative This alternative consists of withdrawing water from the North Fork Rivanna River and pumping it to Chris Greene Lake. Effectiveness This alternative would provide no increase in safe yield due to lack of storage capacity in the lake during non-drought conditions and lack of sufficient flow in the North Fork Rivanna River during those times when storage is available. Practicability/Cost No costs were developed, due to unfeasibility. Environmental This alternative would have minimal environmental impacts. Recommendation Because it would provide no safe yield, we recommend that this alternative not be included as part of a practicable solution. 6. Use Beaver Creek Reservoir to Supplement Flows in Mechums River Description of Alternative This alternative involves conveying water from Beaver Creek Reservoir to the Mechums River to supplement flows to the SFRR during severe drought conditions. 21

34 Effectiveness This alternative is not effective, because water demand in the Crozet area is expected to utilize the entire safe yield of Beaver Creek by Furthermore, the ability to capture a significant portion of any in-stream release is uncertain, and would depend on stream characteristics. Specifically, during drought conditions, when this alternative would be needed, the receiving streams could be sufficiently dry that a significant portion of the release would be lost to infiltration. The only method of documenting this possibility is field-testing during such drought conditions. Practicability/Cost A cost of $500,000 is included for necessary flow measuring equipment downstream of the reservoir. Environmental Minimal environmental impacts would result from implementation of this alternative. Recommendation Because it would provide no safe yield, we recommend that this alternative is not part of a practicable long-term solution. However, in the short-term, before demand in Crozet reaches the 2 mgd level, Beaver Creek could offer some additional yield. We therefore recommend that necessary evaluations take place during the next severe drought. 7. Dredge Sugar Hollow Reservoir Description of Alternative Dredging of Sugar Hollow would consist of a one-time dredge event to remove landslide debris and bottom sediment, returning the reservoir to its original capacity. Given the slow rate of sedimentation in Sugar Hollow, annual maintenance dredging is unnecessary. Effectiveness This alternative would provide only 0.1 mgd in additional safe yield as of

35 Practicability/Cost Dredging the reservoir would be accomplished at a cost of $4.9 million. Environmental The one-time dredging event described herein would impact approximately 2 acres of wetlands, as well as limited areas of shallow water habitat. Furthermore, temporary water quality impacts could be expected, as described in the SFRR dredging section. Recommendation Despite limited environmental impacts, the high unit cost and minimal yield of this alternative lead us to recommend that it is not part of a practicable solution at this time. 8. Conversion of Ragged Mountain to Pumped Storage Reservoir Description of Alternative This alternative involves withdrawing water from the Mechums River and pumping it to Ragged Mountain Reservoirs by rehabilitating and expanding an existing abandoned intake and pump station. The dam at Lower Ragged Mountain Reservoir would be raised by 50 and the dam between the two reservoirs would be inundated. Furthermore, the alternative includes new infrastructure and expansion of the Observatory water treatment plant. Effectiveness This alternative would provide 10 mgd in additional safe yield. Practicability/Cost Ragged Mountain conversion has a relatively high cost of $47 million. Environmental The new pool level would inundate approximately 5 acres of wetlands. As is the case with SFRR, these wetlands would be replaced by new wetlands colonizing the new pool fringe. Furthermore, the Virginia Department of Game and Inland Fisheries has expressed concern that 23

36 withdrawals could impact the fishery in the Mechums River. The presence of the James spinymussel in the Mechums also raises the prospect of negative impacts to a rare and endangered species. Recommendation Although this alternative would provide significant safe yield, it appears that other, more cost-effective alternatives are available. It is possible that there are impacts to the fishery in the Mechums River, and to rare and endangered species; such potential impacts should be investigated if this alternative is further pursued. We therefore recommend that conversion of Ragged Mountain is not part of a practicable solution at this time. 9. Indirect Reuse Description of Alternative Indirect reuse involves treating sewage at the Moore s Creek advanced wastewater treatment plant to a higher purity, and pumping the treated effluent to either the Mechums or the Moorman s River. The effluent would then flow downstream into the SFRR, thereby augmenting available water supply. The alternative includes enhanced wastewater treatment, pumping/pipeline infrastructure, and expanded drinking water treatment capacity. Effectiveness Indirect reuse represents a highly reliable source of water supply that can meet demand even during the most severe drought. This would occur because as demand increases, water treated at Moore s Creek would increase, proportionately increasing the amount available to pump back to the system. For purposes of evaluation, the alternative has been analyzed at 15 mgd, an amount adequate to meet water supply needs throughout the planning period. Practicability/Cost Refining the cost estimate for this alternative is complicated by the fact that the state has no guidance in place for the level of water treatment and quality that would be required; reuse permits are analyzed on a case-by-case basis. Based on the best available information, the Alternatives Analysis assigns to the Mechums River option a cost of $56 million and an annual operating cost of $150,000, which includes energy costs (it should be noted that potential energy costs were considered for all alternatives). Applicable figures for the Moorman s option are $69 million and $280,000 annual operating. 24

37 At the request of the Virginia Department of Health (VDH), the study team performed a review of the treatment approach used by the Upper Occoquan Sewage Authority (UOSA), as a point of reference for indirect reuse in Virginia. The memorandum included in Appendix D documents our findings. While the findings are interesting, evolution of water and wastewater treatment technology would probably lead to a different approach for RWSA. For example, ultraviolet disinfection is now recognized as an effective technique for disinfection of cryptosporidium, giardia and many other organisms, and would likely be preferred over high lime (ph) treatment for disinfection. Pinpointing the cost for enhanced treatment by RWSA s water and wastewater treatment plants is not possible because VDH does not yet have clear water quality objectives that apply to indirect reuse. Therefore, the indirect reuse alternative should anticipate a wide range of costs for additional wastewater or water treatment processes, ranging up to roughly $3/gpd (at 15 mgd this equates to $45,000,000). Most likely, the cost would range from $7 - $30 million. It should also be recognized that some or all of these same upgrades may become future requirements of the Safe Drinking Water Act or Clean Water Act, whether or not indirect reuse is implemented. Finally, it is not clear that the Virginia Department of Health would allow indirect reuse in this case. The Department s regulations require selection of the most pure source. Because other, more pure sources are available, the Department may simply not allow this alternative as is reflected in its comments to-date. The VDH has stated that this alternative does not reflect prudent public health and source water quality considerations (letter to Mr. Arthur Petrini of January 10, 2001). Environmental Neither of the indirect reuse options would adversely affect streamflows, either in the Rivanna River or the receiving river. During drought conditions, indirect reuse would reduce augmentation of flow in the Rivanna resulting from the discharge at Moore s Creek, and would augment flows in the receiving river. During severe droughts, flow in each river approaches 0 mgd. Under this alternative, gradual activation of the pumpback, commensurate with the severity of the drought, would result in maintenance of normal flow levels. This would be a substantial benefit to many species that cannot migrate to other habitats during such stressful events. The pipeline for the Mechums option would impact approximately 2 acres of wetlands, while the Moorman s pipeline would impact approximately 5 acres. The James spinymussel has been identified in the Mechums River in the vicinity of the proposed project. Because this alternative would be utilized only during severe droughts, and would maintain normal streamflows, it is unclear whether effects on the James spinymussel would be positive, negative, or neutral. 25

38 Recommendation Indirect reuse would provide substantial and reliable safe yield adequate to meet long term demand. Its costs, however, are high and also uncertain, and the alternative involves potential impacts to endangered species. Furthermore, the option may not be allowed at all by the Virginia Department of Health. We recommend that indirect reuse not be considered part of a practicable solution at this time. 10. Growth Management Description of Alternative The growth management alternative involves modification of Albemarle County s current growth management policies, which have been shown effective in meeting their goal of directing the majority of new residential development into the Urban Service Area. Changes to these policies would likely displace growth into the surrounding rural areas, given the limited growth management authority granted to local governments, in addition to property rights issues and political/economic realities. Effectiveness Assuming a reduction in the proportion of growth in the Albemarle County portion of the Urban Service Area to 50% (the Demand Analysis assumed this proportion to be 66%), the Urban Service Area would have a 2050 population of approximately 93,000 persons rather than the 110,000 persons as projected in the Demand Analysis. This would represent a decrease in the projected 2050 water demand of approximately 1.7 mgd. It is possible that a range of growth management strategies could be employed to reduce demand; this alternative represents the highest likely reduction that can reasonably be expected from growth management. Practicability/Cost Reversal of current growth management policies could have significant logistical impacts on future development and ultimate costs, but these are not quantifiable. Politically, reversal of growth management policies may not be feasible or practicable. Albemarle County currently implements an effective growth management plan designed to concentrate growth in the Urban Service Area. It may prove impossible simultaneously to prevent this growth from occurring within the Urban Service Area while preventing it from moving elsewhere in the County. In any event, there are no data or proposed policies now in existence that wold demonstrate the practicability and costs of this alternative. 26

39 Environmental If development were dispersed into the rural areas of the County by policies restricting growth within the Urban Service Area, that displaced development would utilize private wells and septic systems. Futhermore, secondary impacts would include construction and maintenance of infrastructure improvements to roads and utilities. Transportation and safety impacts would include longer trips for school buses and commuters, as well as increased time for delivery of emergency services and public transportation. Recommendation The potential reduction in the future water deficit attributable to this alternative would not be realized for many years and is not sufficiently great to obviate the need for an interim solution such as 4 crest controls at SFRR. Furthermore, the growth management alternative would reverse an effective existing policy that enjoys public and political support at present. The resulting consequences and costs of this alternative are difficult to predict but may be significant. We recommend that this alternative should continue to be considered and, if growth restricting policies are adopted in the future, their effectiveness can be assessed and factored into any decision to pursue additional alternatives in the middle and later portions of the study period. However, this alternative should not be considered part of a practicable solution at this time. 11. Leak Detection and Control Description of Alternative This alternative consists of accounting for and correcting sources of system water loss. ACSA and the City currently implement leak detection and meter calibration programs to respond to and correct water loss. Effectiveness Overall documented system losses indicate that the entire system is operating within accepted limits. It does not appear that additional measures would be effective in reducing water demand beyond the impact of ongoing efforts. 27

40 Practicability/Cost Since additional measures would not be effective, no additional costs have been calculated. Environmental Current efforts appear to have no negative environmental impacts. Recommendation Because ACSA and the City currently have effective leak detection programs, additional measures would not be effective. We therefore recommend that this alternative is not part of a practicable solution. B. Physical Additions to the Existing Water Supply System 1. Groundwater Description of Alternative The Alternatives Analysis investigated two options for utilizing groundwater resources. The first, aquifer storage and recovery, involves seasonal underground storage of treated drinking water and subsequent withdrawal to meet demand during shortages. The second, conventional withdrawal of groundwater, includes installation of shallow wells and piping to the South Fork and North Fork water treatment plants. Effectiveness Because of geological conditions, aquifer storage and recovery appears to be technically unfeasible in the Charlottesville-Albemarle area. Conventional withdrawal of groundwater from 15 wells would provide 0.1 mgd in additional safe yield. Practicability/Cost Given the unfeasibility of aquifer storage and recovery, no costs were calculated. Installation of 15 wells conveys a cost of $1.2 million, at a very high unit cost of $12/gallon. 28

41 Environmental Due to unfeasibility, environmental review of aquifer storage and recovery was not necessary. The impacts of conventional withdrawal would be minimal. Recommendation Groundwater options do not represent part of a practicable solution. 2. Reservoirs Description of Alternative The Analysis of Alternatives investigated 7 options for new water supply impoundments, including a reservoir on Buck Mountain Creek utilizing land currently owned by RWSA. Effectiveness All of the reservoir alternatives provide additional safe yield, ranging from 5.6 to Certain of the reservoirs would cover the full 15 mgd safe yield deficit for Practicability/Cost The reservoirs range in cost from $26 million to $118 million. They have relatively high unit costs ranging from $3.96/gallon to $14.22/gallon. Environmental All of the reservoir options involve residential displacements, impacts to cultural resources, and wetland impacts ranging from 52 acres to 144 acres. In addition, several reservoir options involve impacts to the James spinymussel. Recommendation Although the reservoir alternatives would provide significant safe yield, they all involve residential displacements, impacts to cultural resources, and wetland impacts. Also, they have relatively high to very high unit 29

42 costs. Accordingly, we recommend that these alternatives not be considered part of a practicable solution at this time. 3. James River Withdrawal at Scottsville Description of Alternative The James River withdrawal includes construction of an intake, pump station, and 29 mile pipeline to withdraw water from the James and pump it to the South Fork water treatment plant (which would require expansion). Effectiveness This alternative would provide 15 mgd in additional safe yield as of Practicability/Cost The James River withdrawal would cost approximately $72 million. The unit cost for this alternative is $4.80/gallon, relatively high compared to the other alternatives. Environmental Implementation of the withdrawal would impact approximately 5 acres of wetlands mitigation would be provided. The alternative also involves potential impacts to cultural and historic resources that would require additional investigation. A withdrawal of this scale would have minimal impacts to flows in the James River, even if other withdrawals occurred in the vicinity. Figure 9 shows flow exceedance curves with and without the project, while Figure 10 compares flow exceedance curves with no withdrawal versus with RWSA withdrawal plus a proposed power plant withdrawal in the same vicinity. Recommendation This alternative offers a practical source of water sufficient to meet long term demand in the Urban Service Area. Furthermore, the associated environmental impacts are relatively minor. The unit cost, however, is relatively high, and we recommend that the alternative not be considered part of a practicable solution at this time. 30

43 Flow (mgd) Flow Exceedance Curve for James River at Scottsville (RWSA Withdrawal 15 mgd) Period of Record: Oct.1, 1924-Sept.30, RWSA Withdrawal No RWSA Withdrawal Exceedance Percentage Figure 9 100

44 Flow (mgd) Flow Exceedance Curve for James River at Scottsville (RWSA Withdrawal 15 MGD and Power Plant Withdrawal 8 MGD) Period of Record: Oct.1, 1924-Sept.30, RWSA and Power Plant Withdrawal No Withdrawal Exceedance Percentage Figure

45 4. Rivanna River Withdrawal Description of Alternative To withdraw surface water from the Rivanna River, this alternative includes construction of an intake, pump station, treatment plant, and pipeline. It also utilizes the existing water main along Route 250 serving the Village of Rivanna. Effectiveness This alternative would provide additional safe yield of 4.7 mgd in Practicability/Cost This alternative would cost approximately $18 million. The unit cost is $3.83/gallon. Environmental Pipeline construction would impact approximately 2 acres of wetlands, for which mitigation would be included. Figures 11 and 12 demonstrate the minimal impact of the withdrawal, which amounts to an indirect reuse of water through the system. The Virginia Department of Health has expressed water quality concerns about this alternative, which is similar to indirect reuse. Recommendation The Rivanna River withdrawal has a relatively high unit cost, and raises public health concerns (as expressed by the VDH). We recommend that it not be considered part of a practicable solution at this time. 5. Mechums River Withdrawal Description of Alternative Withdrawal from the Mechums involves rehabilitation of the abandoned intake and pump station near Lake Albemarle. Water would be pumped to the Ragged Mountain Reservoirs. 31

46 Flow from Service Area supplied by South Fork & Observatory WTPs (20 MGD) Moores Creek WWTP Discharge (20 MGD) Rivanna River Flow (20 MGD) LEGEND: Discharge Pipeline Wastewater Treatment Plant N Year 2050 Flow Schematic for Rivanna River Alternative (without Glenmore withdrawal) File No Date: November 29, 2000 Figure 11