OWASA - Water Supply

OWASA withdraws an average of 9 million gallons per day (mgd) of water from the Cane Creek/University Lake/Quarry Reservoir system. Customer demands are expected to exceed the raw water system’s safe yield of 11.2 mgd by 2010. The present reservoir/quarry system receives sufficient streamflow and has enough storage capacity to support an average yield of 15 mgd, but is presently constrained by limitations of the infrastructure to move additional raw water from the reservoirs to the Jones Ferry Road Water Treatment Plant in Carrboro.

The present safe yield can be increased to 15 mgd through improvements to the conveyance system, such as larger raw water transmission pumps and pipelines from University Lake and Cane Creek to the water plant. Costs for these upgrades are estimated at $10 million and will be programmed into OWASA’s 15-Year Capital Improvements Plan. Under anticipated rates of growth, these improvements would meet OWASA’s raw water needs until about 2030, when anticipated demands of 15 mgd will exceed the safe yield of the upgraded system and the community will become increasingly vulnerable to drought-related water shortages. Additional raw water storage capacity will be needed to reduce these risks.

Options include developing the Jordan Lake water supply; dredging University Lake; building a new and higher dam at University Lake; raising the dam at Cane Creek; building a new reservoir on Sevenmile Creek south of Hillsborough; purchasing water from another utility, such as Durham; and expanding the storage capacity of the existing Quarry Reservoir near the intersection of NC 54 and Bethel-Hickory Grove Church Road.

OWASA has determined that increasing its raw water storage capacity by approximately three billion gallons or more through the extension of American Stone Company’s existing quarry is the most desirable long term option. When mining is completed no later than 2030, the extended quarry would be used to store excess water pumped from Cane Creek and/or University Lake and would be connected to OWASA’s existing Quarry Reservoir.

This paper presents further details and background information supporting OWASA’s selection of the extended stone quarry as its preferred future water supply alternative. Topics include the estimated rates of growth and associated water demand for the next 50 years; opportunities to manage demands through water conservation; estimated safe yield available through additional stone quarry storage capacity; costs and benefits of alternative water supply sources; and the relationship between the proposed quarry extension and the need for Jordan Lake water.

A community’s water supply is one of its most precious resources – a value that the people of Carrboro, Chapel Hill, and Orange County have recognized through an extraordinary record of water supply planning, development, and protection. Stimulated by water shortages of the 1970s and 80s and fostered by the participation of forward looking representatives of an active and enlightened citizenry, Carrboro, Chapel Hill, and Orange County are rightfully proud of the water supply future they have helped secure.

It is against this backdrop of public awareness and active involvement that OWASA presents its water supply vision for the next 50 years and asks the community to sustain its exemplary tradition of water supply stewardship.

Existing System: OWASA’s water comes from two sources: the Cane Creek Reservoir, a 3 billion gallon (bg) impoundment located eight miles west of Carrboro, and University Lake, a 0.45 bg reservoir located on Jones Ferry Road just outside of Carrboro. A 0.20 bg Quarry Reservoir west of Carrboro is available as a backup water source, and an allocation of Jordan Lake storage capacity may provide up to 10 million gallons per day (mgd) for future use. Further information about these and other potential supply sources are provided later in this report.

Details of the demand forecasting methodology are presented in two technical memoranda (TMs) prepared for OWASA’s Master Plan: TM 3.1 – Water Demand Fore-casts (June 18, 1999) and TM 3.2 – Baseline and Alternative Water Demand Forecasts (August 27, 1999).

Future forecasts were based on the disaggregation of water use among five principle customer sectors: single family residential, multifamily residential, University/UNC Hospitals, commercial, and irrigation-only accounts. The relative demand by each of these sectors is shown in Figure 2. An analysis of seven years of OWASA customer records indicated an average daily consumption of 199 gallons per day (gpd) per single family residence, 137 gpd per multi-family residence, 180 gpd per 1,000 gross square foot (gsf) of University/ UNC Hospitals space, 77 gpd per non-University/UNC Hospitals employee, and 2,073 gpd per irrigation-only account.

Future demands were then estimated by multiplying these factors by the number of units expected to exist in each category at ten-year intervals out to the year 2050. For example, single family residential demands for the year 2020 were developed by multiplying 199 gpd by the number of single family homes projected for that year. This process was applied to each of the five demand sectors in ten-year increments.

Building and employment estimates were based on an analysis of data in OWASA's service area since 1977, with residential growth based on an extrapolation of housing trends observed from 1990 through 1997. These data indicated growth rates of 343 new single family and 132 multi-family units per year within the Carrboro/Chapel Hill service area. In the absence of any predictors that these rates will change in the coming years, they were assumed to remain constant throughout the 50-year planning period. Similar analyses were conducted for the University/UNC Hospitals, commercial, and irrigation-only account sectors.

Alternative high and low demand estimates were developed on the basis of statistical variations in the historical growth and water consumption data. The high, low, and expected estimates were then modified slightly to account for hot/dry and cool/wet weather conditions. The resulting forecasts are reported in TM 3.2 – Baseline and Alternative Demand Forecasts, as noted previously.

The underlying prediction parameters for future water use are summarized in Table 1, and the resulting projections are presented in Figure 3. Because the demand forecasts were based on an extrapolation of historic growth and unit consumption data, the distribution of demand among the major user categories in 2050 is not predicted to differ substantially from the present day pattern illustrated in Figure 2. Varying the assumptions and input parameters (Table 1) will, of course, produce different future demand distributions.

Table 1. Model Parameters Used to Generate Raw Water Demand Forecasts Under the "Expected Growth" Scenario
User Category	Units 1	Base Year Value	Rate of Increase Per Year	Base Year	Water Use Per Unit (gpd) 2
SF Residential	SF Homes	11,669	343	1997	199
MF Residential	DUs	13,855	132	1998	137
UNC/UNC Hospitals	GSF x 1,000	12,670	217	1997	180
Commercial/Other	Employees	13,273	408	1995	77
Irrigation-Only Accounts	Accounts	50	0	1998	2,000
SF = Single Family MF = Multifamily DUs = Dwelling Units GSF = Gross Square Feet of total building space Numbers in this column represent finished (treated) water billed to customers, which is approximately 17% less than the total amount of raw (untreated) water used to produce it. Raw Water Pumped to Plant = Total Finished Water Produced at Plant + Discarded Process Water Where: Total Finished Water Produced at Plant = Billed Water + Unaccounted-for Water Billed Water = 0.91 x Total Finished Water Produced at Plant Unaccounted-for Water = 0.099 x Billed Water Discarded Process Water = 0.06 x Raw Water Pumped to Plant Conversion: Raw Water Pumped to Plant = 1.169 x Finished Water Billed to Customers

How Realistic Are These Demand Forecasts? Long-term growth forecasts – especially for a period that extends beyond the planning horizon of the local jurisdictions in the service area – are inherently subject to numerous uncertainties, many of which cannot be quantified or even identified at this time. It is notable that the 0.182 mgd/yr expected increase in demand is less than the 0.221 mgd/yr rate observed during the 23 years that OWASA has been in operation, as shown in Figure 3.

Future water use will reflect the complex interaction of personal choices, public policies and regulations, as well as constantly changing demographic and economic conditions during the next 50 years. OWASA believes that these forecasts represent the most realistic and reliable estimates of future water use that can be supported by the information and professional judgment available at this time. It will be necessary to periodically monitor and adjust, as appropriate, the many variables and assumptions on which these forecasts are based.

One source of uncertainty in forecasting future demands is the potential reduction through conservation practices. Technical Memorandum 3.3 – Long-Term Water Demand Forecasts with Conservation (January 24, 2000), developed for the OWASA Master Plan, provides a preliminary assessment of water conservation possibilities. However, most of the assumptions on which the analysis was based remain untested in OWASA’s service area. TM 3.3 contains the following consultant disclaimer (the italicized emphasis appears in the original text): "Recognizing there is a degree of uncertainty associated with assumptions used in this analysis, it is premature to rely on the findings of this TM as a definitive resource for planning future water and sewer facility requirements for the OWASA service area."

Nevertheless, OWASA believes that TM 3.3 provides a valuable preview of potential water savings through active and passive conservation programs, and remains committed to collecting additional data that will help validate or modify the assumptions applied to future demand forecasts.

Conservation Findings: Figure 4 provides a graphic summary of end-use water consumption by OWASA customers. It is notable that more than 50 percent of the water is used through indoor plumbing fixtures (toilets, showers, sinks, and baths) and appliances (washing machines and dishwashers). Although outdoor uses (swimming pools, lawn and garden irrigation, and car washing) contribute substantially to short duration summertime peak demands, only about 9 percent of OWASA’s total annual water production is used outdoors.

Carrboro-Chapel Hill is a relatively water-efficient community, as illustrated by the moderate residential use in both single and multifamily homes. Average residential consumption, which is derived by combining OWASA customer account data with single and multifamily Census figures, is about 75 gallons per person per day. According to TM 3.3, "this is indicative of a residential community with conservation water use patterns." TM 3.3 found that improved plumbing efficiency achieved in new construction and through the routine replacement of aging fixtures and appliances may offer substantial water savings over the next 50 years. Such changes are referred to as passive conservation because they are expected to occur without further intervention by OWASA or other outside agencies. TM 3.3 indicates that passive conservation may reduce the 2050 demand forecasts reported above by as much as 18 percent.

By contrast, active conservation programs, such as toilet replacement incentives, residential retrofit kits, conservation rates, water use audits, and individual metering of new multifamily housing units, are only expected to reduce 2050 demands by less than 2 percent. This is due to the relatively small amount of OWASA water used for outdoor purposes, and also reflects the passive water savings that will eventually accrue without the initiation of active programs. Active programs do, however, offer proportionally greater short term savings by accelerating the implementation of certain practices, such as low flow plumbing fixtures, that would otherwise occur more slowly through "natural" replacement. Such nearer term savings might defer the need to upgrade OWASA’s raw water conveyance facilities, described later in this report, until after 2010.

Except for the individual metering of new multifamily housing units, TM 3.3 found the benefit-cost ratios of active conservation to be less than 1.0, which means that implementation costs would exceed the economic savings of those active programs - even when the cost savings realized through the deferral of major capital projects, such as water and wastewater treatment plant expansions, are taken into account.

Figure 5 illustrates the conservation opportunities that may be available through the full implementation of active and passive demand management programs.

What Does This Mean for OWASA? OWASA believes that active conservation programs, such as toilet rebates, residential retrofit kits, water use audits, and conservation rate incentives, offer potential opportunities to reduce short duration seasonal peaks, which significantly affect OWASA’s ability to meet summertime demands. Such programs may also delay the need to begin expensive capital improvements to the raw water conveyance system, but active conservation programs offer little overall reduction in long term demands. OWASA plans to implement conservation rate incentives in the near future and will seriously evaluate the other active programs recommended in TM 3.3.

OWASA recognizes that significant passive water savings may eventually accrue through the continued implementation of national plumbing standards that went into effect in 1994, but OWASA does not intend to incorporate these potential savings into future raw water demand forecasts until actual conservation effects can be observed and verified in local customer data. OWASA is committed to an ongoing program of data collection and analysis that will enable the detection of such trends, which can then be used to modify unit use and other assumptions that comprise the demand forecasting model.

OWASA simply doesn’t know at this time what effects water conservation will have on long term demands. Conservation may allow the deferral of certain capital projects, such as raw water conveyance improvements, for several years or more – but we can’t be sure right now. The potential reduction in future demands from water conservation remains one of the important uncertainties challenging the 50-year forecasts.

We don't think so. OWASA believes that the demand forecasts developed in TMs 3.1 and 3.2 fulfill their intended purpose of providing the planning basis for the Comprehensive Water and Sewer Master Plan, and that the 50-year forecasts generally conform to the local buildout estimates of Carrboro and Chapel Hill, which do not look beyond the 2025 planning horizon. OWASA believes that the demand forecasts are consistent with conservative and responsible planning principles that seek to preserve multiple options for future generations of water users. These are the same principles that Carrboro, Chapel Hill, and Orange County have applied in protecting the long-term quality of the Cane Creek and University Lake water supplies.

The future is difficult to see with clarity, but OWASA firmly believes that the costs of underestimating future water demands far exceed the costs of overestimating them.

Existing System: OWASA’s existing system consists of University Lake, the Cane Creek Reservoir, and the Quarry Reservoir, as summarized in Table 2 and Figure 6.

Raw water from University Lake is pumped to the Jones Ferry Road Water Treatment Plant in Carrboro. Cane Creek water can either be pumped directly to the treatment plant or into Phil’s Creek near the existing Quarry Reservoir, where it flows downstream to University Lake for repumping to the treatment plant; or, Cane Creek water can be pumped into the existing Quarry Reservoir and stored for later use. Water pumped out of the Quarry Reservoir can only be conveyed to the treatment plant via Phil’s Creek and University Lake.

*Table 2. Characteristics of Existing OWASA Supply Sources*	University Lake	Cane Creek	Quarry Reservoir
Year Developed	1932	1989	1979
Drainage Area (square miles)	30	31	<0.1
Total Volume (bg)	0.57	3.01	0.20
Usable Volume (bg)	0.45	2.98	0.20
Surface Area at Full Volume (acres)	212	500	10
Average Inflow (mgd)	18.9	20.1	<0.1
Minimum Release Requirements (mgd)	None	0.14 – 1.9 (depends on inflow)	None

Safe Yield: An important element of OWASA’s Water and Sewer Master Plan has been the accurate determination of how much water the existing Cane Creek/University Lake/Quarry Reservoir system can reliably supply. The yield of a reservoir system is determined by inflows, outflows, and storage volume of the system. Safe yield refers to the demand that can be met under specified operating conditions. For example, a 30-year safe yield is the demand that a system can reliably support under low flow (drought) conditions that would occur on an average of once every 30 years, or have a chance of about one in 30 of occurring in any given year.

Analyses reported in TM 5.1 – OWASA Raw Water Supply Facilities Safe Yield Analysis (July 30, 1999) indicated that the 30-year safe yield of the existing raw water system is approximately 11.2 mgd. The system is presently constrained by certain limitations on the ability to pump and transmit water from University Lake, Cane Creek, and the Quarry Reservoir to the treatment plant. Increasing the capacity of raw water pumps and transmission mains can increase the 30-year safe yield of the storage system to about 15.1 mgd, which would represent the maximum practical use of the University Lake/Cane Creek/Quarry Reservoir system.

Phase I Improvements: These conveyance upgrades are estimated to cost $10 million and will be programmed into OWASA’s 15-Year Capital Improvements Plan in time to meet the increase in demands that are projected to occur by 2010 when average day demands are expected to exceed the present system’s 11.2 mgd safe yield. Additional water provided through the conveyance improvements would then meet raw water needs until about 2030, when average day demands are expected to exceed the 15.1 mgd safe yield of the upgraded system. As noted, this would represent the maximum practical use of OWASA’s existing reservoir and quarry system.

OWASA has explored a range of Phase II alternatives for meeting demands beyond the 15.1 mgd safe yield of the improved reservoir/quarry system. These are described briefly below, with Table 3 providing a comparative summary of the advantages and disadvantages of each. Additional details are available in Master Plan TM 5.2 – Planning Level Economic Evaluation of Raw Water Supply Options (September 9, 1999).

In the following discussion and in Table 3, safe yield and marginal cost estimates for each alternative are compared to the existing reservoir/quarry system assuming that the $10 million conveyance upgrades have already been completed and the system safe yield has been increased to 15.1 mgd. All costs are expressed in 1999 dollars.

Increase Stone Quarry Storage Volume to 1.0 Billion Gallons: This option assumes that OWASA can acquire American Stone’s existing (active) quarry located west of Bethel-Hickory Grove Church Road and convert it to a storage reservoir. OWASA has no rights to this property except under terms of the existing agreement with American Stone and the Philip Durham family, which is contingent on the approval of Carrboro, Chapel Hill, and Orange County to extend the quarry east of Bethel-Hickory Grove Church Road.

As of February 2000, the usable storage volume of the quarry pit was approximately 0.9 bg. One billion gallons of storage would add 2.2 mgd of capacity to OWASA’s raw water system, providing a total system safe yield of 17.3 mgd, which is less than the 18.6 mgd demand currently forecast for 2050.

The $8.25/gpd of additional yield marginal cost of this option, which is among the highest of those evaluated, is driven largely by the need for a deepwater intake structure with high lift pumping and transmission capacity. The marginal cost estimate also assumes that OWASA could acquire the property under the low-cost terms of the existing agreement with American Stone and the Durham family. Additional expenditures for property would further increase the cost of this option.

Increase Stone Quarry Storage Volume to 3.0 Billion Gallons: Up to 3 bg of additional storage volume could be developed if the proposed quarry extension is approved. The existing agreement with American Stone and the Durham family does not guarantee a specific volume when the enlarged quarry pit is eventually conveyed to OWASA, but 3 bg is expected. The agreement does specify that this transfer will occur no later than 2030.

The 0.9 bg storage volume of the present pit west of Bethel-Hickory Grove Church Road is increasing at a rate of 0.05 to 0.10 bg per year, depending on American Stone’s production activity and the elevation from which new rock is removed. If production continues at this rate, an additional 1.5 to 3.0 bg of storage could be created by 2030 for a total final volume of 2.4 to 3.9 bg. As reported in TM 5.2, 3.0 bg of total quarry storage volume would provide 5.4 mgd more capacity to OWASA’s raw water system, providing a total system safe yield of 20.5 mgd, which would likely meet the projected 2050 need of 18.6 mgd.

Due to economies of scale in developing the deepwater intake structure and high lift pumping capacity, the $3.89/gpd of safe yield marginal cost of this option is less than half the cost of the 1.0 bg option described above.

TM 5.2 estimated the safe yields and marginal costs associated with a wider range of quarry volumes than the two scenarios (1 bg and 3 bg) summarized here. For example, 2 bg of quarry storage volume would provide an additional 3.8 mgd of capacity for a system total system safe yield of 18.9 mgd, which would likely meet the 2050 raw water demand forecast. The marginal cost of a 2 bg quarry was calculated to be $5.12/gpd of additional safe yield.

A study done for OWASA by Bisesi and Paull in 1991 estimated that University Lake has lost about 20 percent of its original storage volume due to sedimentation. Most of this is believed to have occurred soon after the lake was impounded during the 1930s when much of the watershed was under intensive agricultural cultivation. The dredging option would consist of removing enough sediment from the upper portions of the lake to add about 0.12 bg of storage capacity, increasing the usable volume to about 0.57 bg. Because the University owns University Lake and the surrounding land, OWASA would have to obtain University and possibly Council of State permission to implement the dredging.

This option would yield only 0.2 mgd of additional capacity at a marginal cost of about $66.40 per gpd of increased yield. This option represents the highest cost and lowest yield of all the expansion options considered. Costs would be higher if sediment analyses revealed toxicity. Dredging-induced turbidity might require that the lake be taken out of service during the operation.

Expanding University Lake would require the construction of a new dam on Morgan Creek about 400 feet downstream of the current structure. The water surface elevation would be 22 feet higher than the lake’s current elevation. This option would include the relocation and/or improvement of several roadways, including three bridges and other structures, and would flood 265 acres of additional land. Additional property acquisition would probably be necessary. Environmental impacts would be significant.

Because the University owns University Lake and the surrounding land, OWASA would have to obtain permission from the University and the Council of State, as well as other regulatory agencies. Construction of a new dam would likely require both state and federal Environmental Impact Statements (EISs). Regulatory approvals, project design, land acquisition, and construction would likely take 10 years or more to complete.

Cane Creek Reservoir could be expanded by modifying the dam to raise the water surface elevation 20 feet above its present level, approximately doubling the usable storage volume to a total of 6 bg. This would require the relocation and/or improvement of several roadways, including two bridges, and would flood an additional 210 acres of surrounding farmland and woodland. Additional property acquisition would probably be necessary. Environmental impacts would be significant.

The project would likely require both state and federal EIS documents. Regulatory approvals, project design, land acquisition, and construction would probably take 10 years or more to complete. Litigation might impose additional delays.

Expanding Cane Creek Reservoir by raising the existing dam 20 feet would provide 5.4 mgd of additional capacity at an estimated marginal cost of $7.39 per gpd of increased safe yield.

This option, which was analyzed by Hazen & Sawyer in 1987, would impound Sevenmile Creek, a tributary to the Eno River with about 14 square miles of drainage area. More than 400 acres of bottomland would be flooded, requiring the relocation of several roads and residences. Because the watershed contains portions of the Interstate 85 and US 70 highway corridors, long term water quality protection would be substantially more problematic than for the University Lake and Cane Creek supply sources.

This project would require OWASA to acquire or obtain access to land purchased previously by Orange County for a possible reservoir on Sevenmile Creek. Additional private land would also have to be acquired. This option would require an interbasin transfer certificate from the North Carolina Environmental Management Commission as well as state and federal EIS documents. As with the University Lake and Cane Creek Reservoir expansion options, regulatory approvals, project design, land acquisition, and construction would probably require 10 years or more to complete. Litigation could impose additional delays.

A new reservoir on Sevenmile Creek would provide OWASA with 4.9 mgd of additional water supply capacity at a marginal cost of about $8.72 per gpd of increased safe yield. Environmental impacts would be significant.

This option would include the construction of a water supply intake near the western shore of Jordan Lake south of US Highway 64, two pumping stations, and a raw water transmission line to OWASA’s Jones Ferry Road Water Treatment Plant in Carrboro. For this analysis, it was assumed that OWASA would pay all costs for full use of the its Jordan Lake water supply storage allocation.

This could provide 10 mgd of additional capacity for an estimated marginal cost of $2.99 per gpd of increased safe yield. Cost-sharing with potential partners, such as Chatham County or Durham (City), might lower these costs. OWASA could develop its Jordan Lake allocation with minimal disruptions or environmental impact, but state and federal EIS documents would probably be required.

Analytical data from the past 11 years indicate that water quality in Jordan Lake is good and nearly indistinguishable in quality from other Triangle area water supply reservoirs, except in the northernmost section upstream of S.R.1008, where the water is highly enriched with nutrients. The Jordan Lake watershed is nearly 30 times larger than the combined drainage area of University Lake and Cane Creek Reservoir. Most of this lies outside of Orange County.

Wholesale purchases of treated water from another supplier, such as Chatham County or Durham (City), would involve no environmental impacts, but would subject a portion of OWASA’s water supply to contractual terms negotiated with another entity. Because no arrangements for guaranteed water sales to OWASA are currently in place or under negotiation, information is not available about additional capacity or marginal costs of this option.

The "no action" alternative would involve no costs and have no environmental impacts.

Current forecasts indicate that average day raw water demands will equal the 15.1 mgd safe yield of OWASA’s upgraded reservoir and quarry system by about 2030. It is not possible to know how future leaders will choose to meet the water demands of their time if no further actions are taken to provide for the community’s long term needs.

OWASA believes that the proposed quarry extension across Bethel-Hickory Grove Church Road is the most desirable option for providing additional water when future demands exceed the supply available from the Phase I improved Cane Creek/University Lake/Quarry Reservoir system. Three billion gallons of quarry storage volume would provide a total system safe yield of 20.5 mgd, which would likely meet the demands currently projected for 2050 (Figure 8). OWASA recognizes that the existing agreement with American Stone and the Philip Durham family does not guarantee a specific usable storage volume when quarry operations end, but OWASA will make every effort to acquire a total quarry storage volume of at least 3 billion gallons.

The marginal cost of the 3 bg quarry option is less than half the cost of the other expansion alternatives except for Jordan Lake, which is about 30 percent less than the quarry extension. OWASA prefers the quarry to Jordan Lake because of the greater degree of local control over future water quality. The total drainage area of the Cane Creek/University Lake/Stone Quarry system is approximately 61 square miles, of which 90 percent lies within Orange County and is subject to local source water protection requirements that are among the most stringent in North Carolina. By contrast, Jordan Lake drains an area of approximately 1750 square miles, nearly 30 times larger than OWASA’s local watersheds, and is more susceptible to contamination from certain pollutants, such as MTBE, than University Lake or Cane Creek. Unlike Falls Lake, which is another Corps of Engineers reservoir of comparable size, Jordan Lake has not yet been the subject of a comprehensive watershed protection study, and no coordinated management program is currently in place.

Because of the high projected costs, significant environmental impacts, and the likelihood of protracted and contentious legal/regulatory difficulties, OWASA does not intend to pursue either the University Lake or Cane Creek expansion options, nor will OWASA seek to develop a new reservoir on Sevenmile Creek. By contrast to such high impact projects, the quarry extension represents the continuation of an existing activity with little or no additional effect on the nearby community and no significant impact on the natural environment. Rather than flooding hundreds of acres of woodland, farmland, and wildlife habitat, the quarry extension will disturb less than 30 acres of property that is already owned by either OWASA, American Stone, or the Philip Durham family. When quarry operations are completed and the pit has been converted into a storage reservoir, more than 100 acres of barren land currently used for quarry and asphalt plant operations will be restored and revegetated, providing a green buffer around a reservoir that may be as large as 60 acres.

OWASA believes that the quarry extension is the preferred alternative for meeting the long term water supply needs of its customers.

Although it might be possible to meet forecasted 2050 demands with only one or two billion gallons of additional storage capacity, larger volumes offer important intangible benefits. These include:

Additional security for an uncertain future: As noted earlier, OWASA’s 50-year demand forecasts are subject to substantial uncertainty. We believe that the additional safe yield gained from more storage capacity represents a reasonable safeguard for the future.

One of the main reasons that OWASA, Carrboro, Chapel Hill, and Orange County supported large lot zoning to protect the quality of Cane Creek and University Lake was the recognition that if a less conservative approach were adopted and subsequently failed, such as higher density development with extensive structural stormwater controls, it would never be possible to go back and "undevelop" the watershed to correct the water quality damage.

OWASA believes that a similarly conservative approach is appropriate for assuring the future quantity of water available from these same supplies. OWASA continues to believe that it is preferable to err on the side of overestimating future water needs – especially when the social, economic, and environmental costs of additional quarry capacity are low.

Reduced drawdowns of University Lake and Cane Creek: Additional storage capacity and the corresponding increase in safe yield will reduce the extent and frequency of lake level drawdowns as water use continues to grow. Benefits to the aesthetic and recreational value of University Lake and Cane Creek would be substantial, as well as environmental benefits to fish, wildlife, and habitat protection.

More reliability and "drought-proofing" for the future: Additional storage capacity will increase the ability of the raw water system to sustain community needs under more severe drought conditions. Safe yield options discussed in this report represent demands that could be supported under drought conditions that occur approximately once in 30 years. Additional quarry volume would help meet community demands under more stringent conditions, such as the 1976-77 drought, which was the most severe in the 72-year record.

Increased operational flexibility and reliability: Additional water supply capacity will provide more operating flexibility if one of the reservoirs must be taken out of service due either to an emergency or for scheduled maintenance of the dam, intake, structure, or the raw water pumping and transmission facilities.

Additional water available for downstream release: Within the 50-year planning period, it is likely that regulatory agencies will determine that the maintenance of water quality in Morgan Creek requires supplemental releases from University Lake, where no minimum streamflow requirements currently exist. Additional storage volume in OWASA’s reservoir/quarry system would help offset the resulting loss in safe yield.

Sustainable resource management: A key principle of sustainability is to manage resources today in ways that maintain a full range of opportunities for future generations. Maximizing the yield of OWASA's raw water system through increased quarry volume can achieve this at little or no cost in community resources.

Optimizing local and regional water resources: Stone quarry extension offers the best opportunity to maximize the yield of OWASA's existing watersheds without developing a new supply source. One result would be less future reliance on Jordan Lake, which will likely become more important to other communities in the growing Triangle Area. Sufficient capacity will reinforce OWASA’s role as a key player in the regional water supply picture.

Will Jordan Lake still be needed? With the 20.5 mgd system safe yield provided by 3 bg of quarry capacity, it is unlikely that OWASA will have to rely on Jordan Lake to meet its water supply needs during the next 50 years. This is not to suggest that OWASA should relinquish its storage allocation or the 125 acres of property at it owns Jordan Lake, which represent valuable assets in which customers have invested more than $600,000 since 1988. It may be possible to convert or exchange these resources for valuable utility services, perhaps through a Jordan Lake partnership with other entities.

How soon after quarry operations have ended could OWASA begin using the vacant pit for water storage? A number of regulatory, design, construction, and implementation activities would have to be completed before the vacated quarry could be used for water storage. Overall, it is estimated that the quarry could be put into operation as a water storage reservoir within three to six years after the mining is completed.

How do we know that the quarry will hold water without leaking? Even though OWASA’s existing Quarry Reservoir has retained water since it was filled 20 years ago, OWASA recently commissioned a geological consulting firm to examine American Stone’s active quarry operation west of Bethel-Hickory Grove Church Road and OWASA’s existing Quarry Reservoir. The consultants did not find any structural evidence, such as fractures, fissures, permeable overburden, and so forth, to indicate that the quarry would leak when filled with water. The only elevation constraint appears to be topographic; i.e., the overflow or rim elevation of the pit, which is approximately 490 feet above sea level.

Are there any special water quality concerns about storing lake water in such a deep quiescent reservoir? Due to the extreme depth and long detention times, water stored in an expanded quarry reservoir is expected to have fewer nutrient, algae, and total organic carbon (TOC) problems and pose fewer treatment challenges than water withdrawn directly from University Lake or Cane Creek Reservoir. In addition, lakewater diverted to the quarry reservoir will have undergone a certain degree of "natural" pretreatment through biological and physical processes in the lake, resulting in lower turbidity and nutrient concentrations (but not necessarily lower TOC) than in tributary water flowing into the lakes themselves. The degree of this pretreatment would vary seasonally, depending on when water was diverted into the enlarged quarry reservoir.

Why do we need to do anything now if our existing supplies will last until 2030? The Carrboro-Chapel Hill-Southern Orange County community is recognized statewide for its proactive stewardship of environmental resources. In no area has this been more evident than local efforts to protect the long term quality of the Cane Creek and University Lake water supplies – efforts that were made with the expectation that these sources will supply water to the community for the next 100 years. It was also understood that the water quality benefits of the protective actions taken today would not be fully realized for many years to come.

OWASA believes that the same values that have guided the community’s water quality protection accomplishments should be applied to assuring an adequate quantity of water for the future.

Are there any other related issues we should be concerned about? Some nearby residents of the quarry have expressed concerns about nuisance noise, traffic, well problems, and property values, as well as possible health effects related to silica dust and radon emissions from American Stone’s existing quarry operation. OWASA is addressing these issues through a separate supplement to an Environmental Impact Statement (EIS) that was originally prepared in 1993. The principal finding of the draft document is that "The proposed project appears to pose no significant threat to human health, safety, or natural resources. No evidence of past or present significant threats to health from silica dust, radon, traffic impacts, or water quality could be identified through the research conducted under this study" (emphasis added).

The final EIS Supplement report will be completed and provided to the public by mid-March 2000.

OWASA currently withdraws an average of 9 million gallons per day (mgd) of water from the Cane Creek/University Lake/Quarry Reservoir system. Customer demands are expected to exceed the raw water system’s safe yield of 11.2 mgd by 2010. The present reservoir/quarry system receives sufficient streamflow and has enough storage capacity to support an average yield of 15 mgd, but is presently constrained by limitations of the infrastructure to move additional raw water from the reservoirs to the Jones Ferry Road Water Treatment Plant in Carrboro.

The present safe yield can be increased to 15 mgd through improvements to the conveyance system, such as larger raw water transmission pumps and pipelines from University Lake and Cane Creek to the treatment plant. Costs for these upgrades are estimated at $10 million and will be programmed into OWASA’s 15-Year Capital Improvements Plan. Under anticipated rates of growth, these improvements would meet OWASA’s raw water needs until about 2030, when anticipated demands of 15 mgd will exceed the safe yield of the upgraded system and the community will become increasingly vulnerable to drought-related water shortages. Additional raw water storage capacity will be needed to reduce these risks.

OWASA evaluated a number of options for securing additional water after 2030. These include developing the Jordan Lake water supply; dredging University Lake; building a new and higher dam at University Lake; raising the dam at Cane Creek; building a new reservoir on Sevenmile Creek; purchasing water from another utility, such as Durham; and expanding the storage capacity of the Quarry Reservoir near the intersection of NC 54 and Bethel-Hickory Grove Church Road.

OWASA has determined that increasing its storage capacity by approximately three billion gallons or more through the extension of American Stone Company’s existing quarry is the preferred alternative for meeting the long term water supply needs of its customers in a manner that is consistent with the community’s values of environmental stewardship and sustainable growth. The quarry extension represents the continuation of an existing activity with little or no additional effect on the nearby community and no significant impact on the natural environment.

CH2M HILL, 1999. OWASA Water and Sewer Master Plan Technical Memorandum
3.1 – Water Demand Forecasts, June 18, 1999.

CH2M HILL, 1999. OWASA Water and Sewer Master Plan Technical Memorandum
3.2 –Baseline and Alternative Water Demand Forecasts August 27, 1999.

CH2M HILL, 2000. OWASA Water and Sewer Master Plan Technical Memorandum
3.3 – Long-Term Water Demand Forecasts with Conservation, January 24, 2000.

CH2M HILL, 1999. OWASA Water and Sewer Master Plan Technical Memorandum
5.1 – OWASA Raw Water Supply Facilities Safe Yield Analysis July 30, 1999.

CH2M HILL, 1999. OWASA Water and Sewer Master Plan Technical Memorandum
5.2 – Planning Level Economic Evaluation of Raw Water Supply Options, September 9, 1999.

CH2M HILL, 1999. Memorandum to Orange Water and Sewer Authority. Effect of Stone Quarry Reservoir Volumes on Cane Creek Reservoir and University Lake Drawdown Levels, December 14, 1999.

CH2M HILL, 1999. Memorandum to Orange Water and Sewer Authority. Expected Water Quality in Expanded Stone Quarry Reservoir, December 27, 1999.

CH2M HILL, 1999. Memorandum to Orange Water and Sewer Authority. Implementation Schedule for an Expanded Stone Quarry Raw Water Storage Reservoir, December 15, 1999.

Orange Water and Sewer Authority, 2000. Staff Memorandum. Water Demand Forecasts and Local Buildout Projections, October 1, 1999 (Revised January 21, 2000).

Earth Tech, Inc., 1999 Report to Orange Water and Sewer Authority. Reserve and Hydrologic Evaluation of OWASA and American Stone Properties, December, 1999.

Tetra Tech, 2000. Report to Orange Water and Sewer Authority. (Draft) Supplement to the Environmental Impact Statement – Proposal to Extend the Stone Quarry and Quarry Reservoir Near the Intersection of NC 54 and Bethel-Hickory Grove Church Road, February 2000.

WATER SUPPLY