The continuing sustained growth the Town of Cary has been experiencing, fueled by a thriving business and technology environment and an attractive quality of life, presents a number of water resources management challenges. Understanding the value in proactive planning for the future, the Town of Cary began an effort in late 2005 to assess its current customer water use trends, identify future water demands, and evaluate supply, conservation, and reclaimed water alternatives to meet the anticipated increased demands from the growth in its service area.
The overall objective of the Town of Cary Integrated Water Resources Management Plan (IWRMP) is to determine the most cost-effective way to meet the current and future water supply needs of the Town’s customers, as well as the Town’s interbasin transfer (IBT) requirements. This plan recommends a cost-effective integrated water management approach that, through successive steps, focuses future expenditures of time and effort on specific areas of potential water resource management.
Integrated Water Resources Management Plan Approach
The overall approach and methodology associated with the IWRMP can be summarized in the following steps:
- Identify the study area and level of detail required for data collection, to develop the water system profile and water demand/supply projections.
- Develop a profile of the Town’s current customers in Cary and Morrisville, using 2001 to 2005 billing data, geographic information system (GIS) parcel mapping, and other available data.
- Develop population projections for single-family and multi-family residential use classifications, as well as representative unit projections for the commercial, industrial, and institutional use classifications, based on historical trends and existing county and regional projections.
- Develop water demand projections, based on population (for residential demand) and other appropriate indicators (for commercial, industrial, and institutional demand), and available water production and billing data.
- Evaluate the effectiveness of existing and potential future water conservation program elements, developing scenarios of water conservation program elements to represent different levels of conservation impact.
- Evaluate options for expansion of the Town’s reclaimed water system, utilizing hydraulic models, and evaluating implementation issues and costs associated with each alternative. This work was performed separately under the Town’s Reclaimed Water System Master Plan, and the resulting options provided to the IWRMP task for integrated analysis.
- Identify a recommended water resources management alternative incorporating both conservation and reuse elements.
Analysis of Water System Profile
Based on a review of the Town’s current customers in Cary and Morrisville, using 2001 to 2005 billing data, geographic information system (GIS) parcel mapping, and other available data, the following general characteristics were observed:
- In Cary and Morrisville, single-family and multi-family residential customers represent the largest share of active accounts, 94 and 90 percent, and water demand, 71 and 64 percent, respectively.
- For Cary’s single-family residential customers with separately-metered irrigation, approximately 42 percent of their 2001-2005 water use was for irrigation. For Morrisville, irrigation comprised 28 percent of 2001-2005 total water use for single-family residential accounts with separately-metered irrigation. Residential accounts with separate irrigation meters have significantly higher daily water use than accounts without separately-metered irrigation, 351 gpd/account versus 208 gpd/account.
- In the Cary service area, the greatest growth in separately-metered irrigation accounts is occurring in houses with a tax value between $200,000 and $500,000, and lot sizes in the 0.1-0.5 acre range, 835 and 1035 accounts respectively.
- Homes constructed after 1995 use more water on an average basis than older homes, due to more outdoor use, 51 gpcd versus 15 gpcd outdoor usage.
- The Neuse River Basin portion of the Cary service area is the area of greatest water demand, 85 percent in 2005, and the largest number of current accounts, 88 percent. Average annual demand in the Neuse River basin portion of the service area has remained relatively constant during the evaluation period, zero percent change from 2001 to 2005, in spite of continued growth. Average annual demand is increasing in the Cape Fear River Basin, 41 percent increase, which is consistent with where a majority of growth in the service area is occurring.
- Climate factors that influence the seasonal variation of demand (temperature and rainfall) have a significant impact on water production, when they depart from normal conditions. For Cary and Morrisville a one degree increase above the normal average monthly temperature will cause a 0.13 mgd and 0.001 mgd, respectively, increase in daily water production. A one inch increase above the normal average monthly rainfall for Cary will cause a 0.11 mgd decrease in daily water production.
The beginning point for the IWRMP alternatives analysis is the base water demand. This demand case assumes estimated water demands will continue current consumption behaviors by Cary and Morrisville customers. The baseline billing data for 2005 are assumed to be the base year characteristics for existing customers of all use classifications. Existing customers will have estimated per-capita demand based on the 2005 average per-capita demand of the service area. Future customers in the single family residential use classification will have estimated per-capita demand based on the 2005 per-capita demand of Cary single-family homes built between 1995 and 2005, to reflect the increased demands exhibited by customers in more recently-constructed homes.
The Voyage® model used this base data to evaluate a number of water management scenarios, including the results of the continuation of current water management policies by Cary. The base demand projections do not include assumptions about changes in future water use characteristics, since the model provides the capacity to study the effects of these assumed behaviors in a more controlled manner.
The unit-based water demand base projections were developed based on evaluation of 2001 to 2005 consumption patterns in Cary and Morrisville. Unit consumption factors were applied to the Towns’ population projections for the years 2010, 2015, 2020, and 2030.
Exhibit ES-1 summarizes the average annual water demand projections by use classification for the Cary and Morrisville service areas. Exhibit ES-2 shows the total average annual water demand projections by the Cary and Morrisville service areas, the Wake County portion of Research Triangle Park (“RTP South”), RDU Airport, and unaccounted for water. Exhibit ES-3 shows the maximum day water demand projections for Cary and Morrisville.
EXHIBIT ES-1 Baseline Water Demand Projections by Use Classification, 2005 to 2030, Annual Average Day (mgd)
|Bulk Water Sales||0.5||0.5||0.5||0.5||0.5|
|mgd = million gallons per day|
EXHIBIT ES-2 Baseline Water Demand Projections by Service Area, 2005 to 2030, Annual Average Day (mgd)
Water Service Area
|mgd = million gallons per day|
EXHIBIT ES-3 Baseline Water Demand Projections by Service Area and River Basin, 2005 to 2030, Maximum Day (mgd)
|Water Service Area
|mgd = million gallons per day|
A peaking factor of 1.64 was used to calculate the maximum day demand as a function of average annual demand. This peaking factor is close to the average of the actual maximum day peaking factors for 1996 to 2005, and is also the value Cary uses for their IBT reporting to the State.
Existing Conservation and Reclaimed Water Programs
Existing Conservation Programs
The Town of Cary has an active Water Conservation Program, currently led by a full-time Water Conservation Coordinator. The Water Conservation Coordinator has two full-time staff and one three-quarter time staff. The Program is overseen by the Water Resources Manager.
Exhibit ES-4 summarizes the existing elements of Cary’s Water Conservation Program, including target water use classes.
EXHIBIT ES-4 Existing Cary Water Conservation Program Elements
||Target Use Class|
|Public Education/Beat the Peak Campaign||All|
|School-Based Educational Programs||Residential|
|Block Leader Program||Residential|
|Water Audits||Residential & Commercial|
|Toilet Flapper Rebate||Residential|
|Tiered Rate Structure||All|
|Water Waste Ordinance||All-Outdoor|
|Rain Sensor Ordinance||All-Outdoor|
|Alternate Day Watering Ordinance||All-Outdoor|
|Land Development Ordinance||Commercial-Outdoor|
|Irrigation Plan Review||All-Outdoor|
|Separate Irrigation Meters||All-Outdoor|
Reclaimed Water Initiatives
Cary currently has a reclaimed water program in place as part of its strategy to manage and plan for future water supply needs. The Town became the first city in the State of North Carolina to pump treated wastewater effluent to homes and businesses for irrigation and cooling. Cary is currently permitted to divert up to 5 million gallons per day (mgd) of treated wastewater effluent to its reuse system, consisting of:
- Bulk Reclaimed Water: Both of the Town’s Water Reclamation Facilities (WRFs) allow approved contractors and Town employees to fill non-potable water tanks for use in irrigation, road construction, dust control, sewer flushing, and street cleaning.
- North Cary Reclaimed Water Distribution System: A reclaimed water distribution system originating from the North Cary WRF serves commercial facilities for irrigation and cooling needs, as well as, lawn irrigation for single-family homes. The North Cary WRF reclaimed water distribution system consists of approximately 9 miles of transmission and distribution lines, and includes a 7 mgd pump station and a 1 million gallon (MG) in-ground storage tank. It supplies an average of 158,000 gallons per day (gpd) to approximately 300 residential and commercial customers. The peak day demand for the current North Cary WRF reclaimed water distribution system is up to 0.57 mgd.
- South Cary Reclaimed Water Distribution System: Reclaimed water from the South Cary WRF currently serves the irrigation needs for nearby schools and a recreational complex. The South Cary WRF reclaimed water distribution system consists of 1.4 miles of transmission and distribution lines, and supplies an average of about 18,000 gpd. The peak demand for the current South Cary WRF reclaimed water distribution system is up to 70,000 gpd.
- Projects Underway: A current Town project will construct reclaimed water infrastructure needed to supply customers in West Cary and RTP South with reclaimed water from Durham County’s Triangle WWTP. As part of this effort, Town staff will work with developers to construct distribution systems within upcoming residential and commercial developments to utilize this irrigation water supply.
Conservation and Reclaimed Water Program Alternatives
Building upon an understanding of the Town’s current water use profile, anticipated system growth, and proven conservation and reclaimed water strategies, specific alternative water management programs have been developed and evaluated. The Town grouped promising potential water conservation elements, along with options to further expand the service area for the Town’s reclaimed water system, into defined alternatives which were then evaluated for their effectiveness in meeting Cary’s water resource management goals.
Water Conservation Program Elements
The Town reviewed project success criteria and developed a “short-list” of 20 potential water conservation measures from an initial listing of over 100 potential water conservation program elements across the spectrum of regulatory, economic incentive and education drivers. Exhibit ES-5 summarizes the four conservation program scenarios which were developed as combinations of conservation program options.
EXHIBIT ES-5 Summary of Water Conservation Measure Scenarios
||Conservation Measure||Scenario A||Scenario B||Scenario C||Scenario D|
|1||Toilet Retrofit on Resale||√|
|2||Require High-Efficiency Toilets and High-Efficiency Urinals in New Buildings||√|
|3||Clothes Washer Rebates||√||√||√|
|4||Distribute Retrofit Kits||√||√|
|5||Increased Residential Water Audits|
|6||New Home Efficiency Point System||√||√|
|7||Restaurant Low-Flow Spray Nozzles||√||√|
|8||Increase public education||√||√||√|
|8a||Continue existing level of public education programs||√|
|9||Turf Buy Back Program|
|10||Landscape limitations for new buildings||√|
|11||Require High Tech Irrigation Controllers||√|
|12||Free industrial/ commercial/institutional water audits||√|
|14||Automated Meter Infrastructure (AMI) Enhanced Irrigation Regulation Monitoring||√||√||√||√|
|15||Self-closing faucets on new Commercial/ Industrial/ Institutional buildings|
|16||Irrigation audits of large turf areas||√||√||√|
|17||Cooling Tower Water Audits|
|18||Cooling Tower Requirements||√|
|19||System water audits||√||√||√||√|
|20||Conservation pricing for water rates||√||√||√||√|
A modified version of Scenario C was evaluated during the Alternatives Analysis, deleting the clothes washer rebate program element and modifying implementation schedules for other program elements.
An evaluation of the existing education program (8a) was added to the conservation program evaluation, to include the existing program in one of the Alternatives to analyze the impact on water savings by maintaining the conservation program as it is currently operated.
- Scenario A reflects a continuation of existing water conservation programs and policies, with enhanced monitoring capabilities provided by the Advanced Meter Infrastructure (AMI) program to be at full implementation by 2009-2010. This will be the conservation program in effect if current approaches are not changed. Any increases in funding for conservation programs in this scenario would be solely to maintain the level of current program services as the service area population increases.
- Scenario B adds additional education and economic incentive programs (fixture rebate, rate tier adjustments, and additional resources to the conservation education program).
- Scenario C includes all the Scenario A/B elements, plus a new home and building points system to encourage voluntary adoption of water-saving strategies for indoor and outdoor water uses in new construction, and distribution of water-conserving fixture replacements to existing customers.
- Scenario D implements all potential conservation measures; but instead of the voluntary new homes/buildings point system, Scenario D makes these conservation measures mandatory.
Reclaimed Water System Master Plan Options
The reclaimed water system options represent a phased approach in an attempt to find the most economical target build-out point of the proposed distribution systems. Exhibit ES-6 summarizes the features, projected 2030 water savings, and cost of the reclaimed water system options, in 2007 dollars.
- Option 0 continues the existing reclaimed water system, with additions in West Cary only to meet existing commitments.
- Option 1 is the expected outline of the reclaimed water distribution system resulting from continuation of existing policies; growth occurs primarily through the near-term development of reuse customers in West Cary, in the Cape Fear River Basin.
Option 1A was developed as an expansion of Option 1, with additional reclaimed water distribution lines branching off the West Cary “backbone” to supply all feasible new development in the Cape Fear River Basin.
- Option 2 expands the service areas of both the North Cary WRF and South Cary WRF.
- Option 3 is a further expansion of the North Cary WRF service area to include retrofit of some existing potable water irrigation customers along the North Cary WRF reclaimed water distribution main to West Cary. This option is designed to maximize use of reclaimed water from the North Cary WRF.
The Western Wake Partners (Cary, Apex, Holly Springs, and Morrisville) have elected not to develop a reclaimed water distribution system supplied by the future Western Wake WRF at this time. While development is anticipated to occur in the vicinity of the plant eventually, few reclaimed water customers will be in close proximity to the plant in the near term.
EXHIBIT ES-6 Table of Reclaimed Water Options
|Reclaimed Water Option
||Option Features||2030 ADD Reclaimed Water Demand||2030 MDD Reclaimed Water Demand||Capital Cost ($)|
|Option 0||–||North Cary WRF reclaimed water area serves current customers||0.5 mgd||1.8 mgd||$0.7 Million|
|–||West Cary future customers with existing commitments only are served from Durham Co. Triangle WWTP; system is not served from North Cary WRF in the future|
|Option 1||–||North Cary WRF reclaimed water area serves current customers and infill of immediate vicinity||0.97 mgd||3.5 mgd||$16.5 Million|
|–||West Cary and RTP South future customers served first from Durham Co. Triangle WWTP, then North Cary WRF|
|–||South Cary WRF reuse area serves current customers and infill of immediate vicinity|
|Option 1A||–||Serves all of Reclaimed Water Option 1||1.3 mgd||4.8 mgd||$36.2 Million|
|–||Additional future West Cary customers, focusing on developer construction of infrastructure|
|Option 2||–||Serves all of Reuse Option 1A||1.5 mgd||5.5 mgd||$41.1 Million|
|–||Additional future customers in West Cary and Morrisville|
|–||South Cary WRF reuse area expands further into surrounding area|
|Option 3||–||Serves all of Reuse Option 2||1.8 mgd||6.5 mgd||$79.1 Million|
|–||Existing potable water irrigation customers in North Cary, West Cary and Morrisville converted to reuse|
|ADD = average day demand
mgd = million gallons per day
IWRMP Alternatives Analysis
Exhibit ES-7 illustrates the IWRMP Alternatives which are combinations of the potential water conservation program elements and reclaimed water system options.
EXHIBIT ES-7 Summary of IWRMP Alternatives
|Conservation Scenario A||Conservation Scenario B||Conservation Scenario C||Conservation Scenario D|
|Existing Reclaimed Water Commitments (Option 0)||A-0
|Reclaimed Water Option 1||A-1
|Reclaimed Water Option 1A||C-1A
|Reclaimed Water Option 2||B-2
|Reclaimed Water Option 3||B-3
The alternatives evaluation reviews each alternative’s capability to meet the water resources management objectives and guidance outlined by the Town:
- Meet the current and future water supply needs of the Town’s customers. Specifically, the Alternative’s potable water demand (average day demand, maximum day demand), reclaimed water demand (average day flow, maximum month average day flow, maximum day flow), and wastewater flow to each WRF (average day flow, maximum month average day flow) were assessed.
- Meet the requirements of the Town’s IBT certificate. If the IBT associated with this alternative is greater than allowed under the Towns’ current IBT Certificate, what facilities and costs would be required to return water to the Haw/Cape Fear River Basin to satisfy the terms of the current IBT certificate?
- Reduce overall per capita potable water consumption 20 percent by 2015. This goal was adopted by the Cary Town Council in 1996.
- Defer investments for capital projects for the expansion of water supply facilities or the development of new sources.
- Feasible financial impact on rates and debt, due to operations costs and capital costs. What are the direct costs to implement this alternative, in capital and operations budget terms? What are the impacts to customer rates from implementing this alternative?
CH2M HILL’s Voyage® Model was utilized to determine the cost profile and the water demand impact of the suite of conservation and reuse measures within each IWRMP alternative. Town of Cary staff utilized the Town’s rate model to evaluate the rate impacts associated with each alternative.
Alternative A-0 is the comparative “no-action” standard for comparison. Alternative A-0 incorporates the natural water savings from fixture replacement, continuation of existing conservation programs and existing commitments to the reclaimed water system. The average day demand (ADD) of Alternative A-0 reflects 1.3 mgd of potable water savings compared with the Section 4 baseline projections; maximum day demand (MDD) of Alternative A-0 reflects 2.6 mgd of potable water savings.
Exhibit ES-8 summarizes the potable water demand and savings at the end of the 2030 planning horizon (in both ADD and MDD terms) of each IWRMP alternative. Potable water savings are presented relative to the baseline projections documented in Section 4. Alternative D-3 saves the largest amount of water in both average day and maximum day terms. All the alternatives’ 2030 demands are within an approximate 10 percent range.
EXHIBIT ES-8 Summary of 2030 Potable Water Demand and Savings – Cary, Morrisville, RTP South; IWRMP Alternatives
||Alternative Potable Water ADD (mgd), 2030||Alternative Potable Water MDD (mgd), 2030||Alternative ADD Potable Water Savings, 2030 (mgd)*||Alternative MDD Potable Water Savings (mgd)*|
|ADD = average day demand
mgd = million gallons per day
MDD = maximum day demand
Exhibit ES-9 compares the potable water demand projections for the alternatives through the 2030 planning horizon. The combined Cary, Morrisville and RTP South water demand projections are compared with the Towns’ combined Jordan Lake Round 3 water supply storage allocations (when system process losses are excluded from the allocation, the allocation is equivalent to 28 mgd).
In any particular year, the effects of weather (e.g., temperature and rainfall) can have a substantial impact upon annual average potable water demand. Based on 1996 to 2005 data, weather can account for up to 4 percent effect on annual water demand in the Town’s service area. Only Alternative D-3 does not predict exceeding the allocation in a dry year, though within the limits of accuracy of this analysis, even this alternative cannot be said conclusively to maintain 2030 demands within the current Jordan Lake allocation.
EXHIBIT ES-9 Comparing Cary/Morrisville/RTP South Demand Projections with Jordan Lake Allocation
EXHIBIT ES-9, Chart Comparing Cary/Morrisville/RTP South Demand Projections with Jordan Lake Allocation
Exhibit ES-10 summarizes the reclaimed water demand at the end of the 2030 planning horizon (in both ADD and MDD terms) of each IWRMP alternative.
EXHIBIT ES-10 Summary of Reclaimed Water Demand, IWRMP Alternatives
||Total ADD (mgd), 2030||Total MDD (mgd), 2030|
|mgd = million gallons per day|
Exhibit ES-11 summarizes, by Alternative, the total maximum month average wastewater flow to Cary’s treatment facilities at the end of the 2030 planning horizon.
EXHIBIT ES-11 Summary of IWRMP Alternatives, 2030 Maximum Month Average Day Wastewater Flows, (in mgd)
||North Cary WRF||South Cary WRF||Western Wake Regional WRF* (without Apex)||Western Wake Regional WRF** (with Apex)||Total (from Cary)*|
*Does not include Apex wastewater flows.
Includes estimated Apex wastewater flows, including the flows resulting from the decommissioning of Apex’s Middle Creek WWTP by 2030. These flows also include approximately 2 mgd of process waste from the Cary/Apex WTP.
mgd = million gallons per day
The following observations from the alternatives analysis documented in this section will guide the recommendation:
- Aggressive conservation and reclaimed water programs would be needed to achieve the Town’s goals to (1) mitigate the need for interbasin transfer facilities to maintain compliance with its IBT certificate, and (2) achieve per-capita residential reduction.
- Alternatives A-0 and A-1 do not yield sufficient potable water savings to defer water supply or wastewater treatment capital facilities, or mitigate the need for interbasin transfer facilities.
- The highest level of reclaimed water system expansion, Reclaimed Water Option 3, has high debt load, and yields small water savings compared to Reclaimed Water Option 2. Both Reclaimed Water Options 2 and 3 have high unit costs ($/gpd water saved) compared with the construction of new water supply and treatment facilities.
- Conservation Scenario D includes a number of programs which would require intrusive regulatory enforcement, though these measures would have substantially more assurance of potable water savings than the “behavioral” measures implemented in Conservation Scenarios A, B, and C.
- Each of the IWRMP alternatives will require additional measures beyond conservation and reclaimed water system expansion in order to meet the requirements of the Town’s IBT certificate.
- The analysis of financial impacts does not show a comprehensive advantage to any of the alternatives.
Reclaimed Water Option 1A and the modified Conservation Scenario C were developed into Alternative C-1A during the alternatives analysis, in order to optimize cost and water savings.
The Recommended Alternative for the Town’s Integrated Water Resources Management Plan is Alternative C-1A. This alternative includes the following elements, estimated to reduce potable water demand by 2030 by a combined 1.6 mgd beyond the baseline Alternative A-0 (A-0 includes the continuation of the existing conservation program and current infrastructure commitments, such as reclaimed water system expansion commitments and AMI installations for Cary and Morrisville):
Expansion of the Town’s reclaimed water system for a projected average day demand of 1.33 mgd and a maximum day demand of 4.8 mgd, as described in Option 1A. Features of this expansion include:
- Recognition of expanded reclaimed water service areas in North Cary and West Cary, with requirement of reclaimed water use by new development within these areas, and construction of reclaimed water infrastructure by developers in accordance with the Reclaimed Water Master Plan.
- As demands in the reclaimed water system increase, restrictions on the use of this resource should be similar to those imposed on potable water. This may include Alternate Day Watering restrictions and/or time-of-day restrictions on reclaimed water customers in order to manage system pressures.
Continuation of many of the Town’s current water conservation program elements:
- Expansion of current public education/Beat the Peak programs to serve a greater percentage of Cary customers
- Expansion of school-based education programs for elementary, middle and high school students to serve a greater percentage of Cary students
- Block Leader program
- Residential and commercial water audits by Conservation staff
- Enforcement of water-related ordinances, including land development ordinance, alternate-day watering, rain sensors, water waste ordinance, and plan reviews for automatic irrigation systems. Watering restrictions enforcement is anticipated to be aided significantly by implementation of Automated Meter Infrastructure (AMI) technology.
- Tiered rate structure
Phased implementation of these additional water conservation programs by Fiscal Years 2009 to 2011:
- New Home Efficiency Point System. This conservation program will raise the profile of positive water-efficiency best practices, and will focus attention on irrigation issues, where the greatest opportunities lie for reducing peak day and residential per-capita demand. Implementation of this program will require detailed evaluation of rate and fee modifications associated with this new incentive program, and proactive involvement of the development community as stakeholders.
- Distribute plumbing fixture retrofit kits to customers in older, single-family homes.
- Distribute low-flow 1.6 gallons per minute (gpm) spray nozzles for restaurant operations
- Increase water audits for irrigation systems in large turf areas
Focused monitoring of the Town’s water consumption using the new AMI technology to be implemented over the next 2 years, including specifically these areas:
- Irrigation use for residential customers, particularly (1) high-use customers and (2) customers without separate irrigation meters
- Review peak day consumption data
- Reclaimed water demand
- Compliance with alternate day and other use-related restrictions
- Future viability of smart-controller irrigation systems
- With these data, the Town would have adequate information to design adjustments to Tier 2 and 4 water rate thresholds for Fiscal Years 2011 to 2012, to provide customers with an incentive to reduce their irrigation consumption.
The Town should give focused consideration to the future implementation of the following water conservation measures. A final decision on implementation of these measures would be made after collection of approximately 2 years of AMI data, or about 2011.
- Limitations on the amount of irrigated turf and landscaping. This measure is projected to yield significant savings, and strongly targets outdoor use.
- Toilet rebates, for installation of ultra-low-flow toilets and high-efficiency toilets. Toilets are the number one domestic user of water in a home, and its impact would not be contingent upon changing customer behaviors.
In order to assure adequate future supply, the Town should plan to pursue at least 4 mgd of additional water supply (on an annual average basis), either in a future round of Jordan Lake water supply storage allocations, or water purchases from another utility. This includes consideration of higher-than-normal demands that may occur during a drier-than-normal year. A water supply in the Neuse River Basin would help reduce the amount of interbasin transfer.
The Recommended Alternative’s water demand, wastewater and reclaimed water profile is summarized in Exhibit ES-12.
EXHIBIT ES-12 Summary of Recommended Alternative Estimated Potable Water Demand, Reclaimed Water Demand, and Wastewater Flow, mgd – Cary, Morrisville and RTP South
|Potable Water ADD||16.1||19.6||23.0||27.5|
|Potable Water MDD||25.3||30.5||36.1||42.4|
|Reclaimed Water ADD||0.4||0.9||1.0||1.3|
|Reclaimed Water MDD||1.7||3.3||3.8||4.8|
|Wastewater Flow, ADF*||16.4||19.6||23.5||26.9|
|Wastewater Flow, MMADF*||19.2||23.1||27.6||31.6|
|* These flows are the total wastewater flow to the treatment facilities.|
Required Water Resource Management Facilities
The analysis of this Plan shows that expansion of water supply, water treatment and wastewater treatment capacity will be deferred through the recommended alternative. Still, expansion of existing supply and treatment facilities will be required, as follows:
- Water Supply – the projected average day demand does not exceed the current allocation in Jordan Lake in a “normal weather” year, but in a dry year additional capacity will be required. To provide adequate reserve, at least an additional 4 mgd ADD water supply capacity is recommended, either at Jordan Lake through the existing intake, or possibly at another location.
- Water Treatment – the projected maximum day water production for the Cary/Apex WTP, including an estimate of Apex peak demand, is approximately 56 mgd in the Recommended Plan, in a normal weather year. Since the next planned expansion of the WTP is to 56 mgd, further expansion of treatment capacity is needed. This Plan estimates “dry year” peak demand exceeding 56 mgd requiring the expansion to be completed by 2028. Finished water purchases could be negotiated with other utilities in lieu of further expansion of the Cary/Apex WTP. Finished water purchases from the Neuse River Basin have an IBT benefit.
- Wastewater Treatment – It is understood that the Town does not plan to further expand the capacity of the North Cary WRF or South Cary WRF. While service area demands for South Cary WRF are consistent with this approach, beginning about 2022 a portion of Upper Crabtree Creek basin wastewater flows that exceed the North Cary WRF capacity would need to be transferred by pump station into the Western Wake Regional WRF service area. By 2030, this pump station would be estimated to pump less than 1 mgd MMADF.
The Town is currently designing the Western Wake WRF for an ultimate capacity of 30 mgd on a maximum month average day flow basis. Assuming Apex sends wastewater to the Western Wake WRF from only those areas of its service area currently identified, expansion of the Western Wake WRF could be needed as early as 2025. Depending on when the Apex Middle Creek WWTP is to be decommissioned and flows currently routed to that facility were routed to Western Wake WRF for treatment, the date of the 30-mgd expansion would be adjusted accordingly. The expansion to 30 mgd appears sufficient for currently-projected flows of about 23 mgd MMADF in 2030.
Interbasin Transfer Certificate Management
The Town should plan for future compliance with the IBT Certificate limit based on the projected amount of interbasin transfer from the Haw River Basin to the Neuse River Basin associated with the implementation of Reclaimed Water Option 1-A and Conservation Option C. Further, the Environmental Impact Statement (EIS) for the Western Wake Regional WRF, a vital element of the Town’s IBT management strategy, has been shifted from a State EIS to a Federal EIS. This change may delay approvals for this project and the facility may not be online as expected by January 1, 2011.
No facilities are recommended for IBT management as part of this recommended plan, though the projections presented in this plan will require the Town to address projected IBT amounts above the certificate limits as soon as possible. The Town has several IBT management alternatives and its selection may depend upon negotiation with other utility providers.
As discussed in Section 10.4.3.2, IBT management alternatives could involve:
- Construction of facilities to transfer about 6 mgd of raw wastewater or treated effluent from the Neuse River Basin to the Cape Fear River Basin on peak IBT days
- Apex’s decommissioning of Middle Creek WWTP and routing these flows for treatment at Western Wake WRF
- Additional water supply from the Neuse River Basin
- Additional wastewater treatment with discharge in the Cape Fear River Basin
- Petitioning NCDENR to modify the IBT certificate, pursuing an average day requirement and/or increasing the maximum-day IBT limit by 6 mgd
It is recommended that the Town investigate these alternatives and complete a policy decision selecting its IBT management strategy within the next 2 years. Maximum-day IBT is expected to be in excess of current IBT certificate conditions at times between 2007 and 2030, and without the Western Wake Regional WRF in place on January 1, 2011, additional near-term measures will be needed more quickly than transfer facilities can be constructed or modifications approved for the current IBT certificate. Additional water supply from the Neuse River Basin or wastewater treatment with discharge in the Cape Fear River Basin can be accomplished through contract with other utilities, such as City of Durham or Durham County, and are suggested as technically-viable near-term options.
Both the petition for a modified IBT certificate and construction of transfer facilities will require substantial capital funding, and significant advance planning. Both could be considered as long-term strategies for the Town’s IBT certificate compliance. Due to weather-related uncertainty, IBT should be expected to vary within a several mgd range, so that the long-range IBT management solution to account for 6 mgd of additional IBT management should be in place up to 5 years before projections would otherwise indicate. With this guideline, preparations for a petition to modify the Town’s IBT certificate should begin at least 8 years prior to when the modified certificate is estimated to be required; the timeline is similar for design of constructed transfer facilities.
Assuming a near-term non-capital solution, such as additional water supply or wastewater capacity with another utility, can manage up to 2-3 mgd of IBT-related transfers for certificate compliance, the Town should commence work on a petition to modify the IBT certificate, or to design facilities to transfer raw wastewater or treated effluent, by 2009.
Required Resources for the Recommended Alternative
The Recommended Alternative will require capital investment, operations budget and staff resources for implementation. Continuation of existing conservation programs was forecast by Town staff for Fiscal Year 2008; it is anticipated that the financial plan for the Recommended Alternative will be implemented beginning in Fiscal Year 2009.
By 2011, the Town will require an additional 3.25 full-time equivalent (FTE) staff in educational and enforcement positions, in addition to the existing 4.75 FTE for the conservation program staff and existing reclaimed water system coordinator. Additional staff are needed in public education, school-based education, AMI data monitoring, the New Home Efficiency Point System, and targeted fixture retrofit programs, in order to implement the proposed conservation program elements identified above and maintain the current level of service for existing conservation education programs and the reclaimed water system.
Exhibit ES-13 summarizes the implementation funding for the Recommended Alternative. Operations budgets for the conservation and reclaimed system programs are proposed to be increased from their current funding levels of $346,000 and $80,000 per year, respectively. A portion of the capital project funding totaling approximately $9 million, for the Northwest Area Reclaimed Water Project Phases II and III, had previously been included in the Town’s Capital Improvement Plan for FY2008/FY 2009. The Recommended Alternative is proposed to further define and enhance the current budget for reclaimed water system expansion.
EXHIBIT ES-13 Summary of Capital and Operating Costs of the Recommended IWRMP Alternative, 2008-2030 (2007 Dollars)
||Reclaimed Water Capital Cost||Conservation Program Cost||Reclaimed O&M Cost||Total Cost||Present Value Cost|
Participation in Regional Water Resources Issues
The IWRMP’s review of local, state, national, and international trends in water resources management prompts the following additional recommendations as the Town plans for its future water needs:
- Continue to be involved in regional water resources planning initiatives and involve stakeholders early in these planning processes.
- Continue to review interbasin transfer requirements. The General Assembly started revising the IBT legislation during its 2006 session, and further developments on this issue are likely in the next several years. The Town should also encourage the state to review IBTs on a watershed basis. For example, the City of Durham has an IBT from the Neuse River Basin to the Cape Fear River Basin which offsets the Town of Cary’s transfer.
- Continue to educate the Town Council on water resources planning issues and how the programs are related to the rates that are set.
- Track the progress of the State Climate Office on development of new tools to forecast weather and drought. While long-term climate forecasting will remain an art, the Town should follow adaptive management practices in its water resources planning and use the best data available to make decisions.