Water Shortage Response Plan

Prepared by: Leila Goodwin, Water Resources Manager

Supersedes: 4/12/01

Approved by Council: 5/10/07

Effective: 5/10/07

Purpose: To establish a Water Shortage Response Plan according to guidelines provided by the State Division of Water Resources

The Town of Cary has a Water Conservation Program that is designed to manage effectively Cary’s use of our natural resources over the long-term to fulfill long-term goals such as - reducing per capita use of potable water and deferring associated capital facilities’ needs. Accordingly, the Town has adopted year round water conservation ordinances and irrigation system requirements. In contrast, the purpose of this policy is to create a plan for dealing with short-term water shortage. The NC Division of Water Resources’ Water Shortage Response Handbook for North Carolina Water Supply Systems (2003) recommends that municipalities should develop a Water Shortage Response Program, and include the following components:

adoption of an ordinance to provide legal authority to enact system measures to reduce demand in the case of an emergency;
development of a method to evaluate ability to meet demand; and
development of procedures for implementing appropriate water shortage declarations.

Each of these components has been implemented by the Town of Cary, and is described below.

1. Adoption of Water Use Shortage Declaration Ordinance or Bylaw

The NC Division of Water Resources recommends that every municipality adopt an ordinance to

“provide for the declaration of a water shortage and specify voluntary and mandatory conservation measures to be imposed at each level of water shortage severity.”

Two sections of the Town code provide staff authority to implement measures to address potential water shortages, including Section 36-80, Water Service Provided by Town Includes only Alternate Day Outdoor Irrigation; and Section 36-81, Water Shortage Declaration.

2. Evaluation of Ability to Meet Demand

The ability to meet demand is dependent on several components of the Town’s water supply system: the water source (Jordan Lake and/or purchase from others), raw water intake and pipeline, treatment plant, storage tanks, and distribution system. Town staff and the Town Manager continually evaluate the status of all these components to determine if a water shortage condition exists or is approaching. There are several indicators used by staff to signal the potential for a water shortage condition, which are described below:

Jordan Lake Water Supply Storage Allocation

Cary and Apex have a joint allocation of water supply storage volume in the Jordan Lake Water Supply Pool. Cary/Apex holds a water supply storage allocation equal to 32 percent of the water supply pool or 14,656 acre-feet (4,778 million gallons). Morrisville holds a water supply storage allocation equal to 3.5 percent of the water supply pool or 1,603 acre-feet (523 million gallons). Wake County (on behalf of RTP South) holds a water supply storage allocation equal to 3.5 percent of the water supply pool or 1,603 acre-feet (523 million gallons).

Cary Public Works/Utilities staff tracks the amount of water in storage in each of these water supply allocation pools on a daily basis using daily and monthly water use estimates, and daily lake inflows obtained from the US Army Corps of Engineers. Cary staff use the storage estimates to monitor a worst case scenario for the number of days of water supply remaining. The number of days remaining is calculated by dividing the storage volume in individual water supply pools by the average water use for the last 30 days, which assumes no inflow into Jordan Lake.

The Division of Water Resources has recommended guidelines for monitoring the available raw water supply and, when necessary, implementing three phases of water shortage response: voluntary, mandatory, and emergency. Table 1 shows the storage thresholds developed by Town staff for considering implementation of each phase.

Table 1

Water Use Reduction Phases and Associated Storage Thresholds

Water Shortage	Description	Days of Storage Remaining	Example Of Volume Remaining If Demand Is 20 Million Gallons Per Day
Voluntary	Conditions indicate the potential for water supply shortages	90	1,800 million gallons (MG)
Mandatory	Visible or measurable signs indicate that supplies are significantly lower than the seasonal norm and are diminishing.	60	1,200 MG
Emergency	The system is experiencing a water shortage and the supply is clearly inadequate.	30	600 MG

The thresholds in Table 1 are only guidelines – the actual implementation of specific water shortage phases during periods of water shortage will be determined based on an assessment of all the factors influencing water supply. As an example, if demands are averaging 10 million gallons per day and storage falls below 930 million gallons, which represents 93 days of supply, voluntary measures - in addition to normal conservation program measures - would be considered.

In addition to the phases above, the town’s Water Use Reduction Ordinance (Sec. 36-81) allows for water rationing if necessary.

Jordan Lake Elevation

In addition to the Water Supply Storage Allocation, Town of Cary staff closely monitors the water elevation of B. Everett Jordan Lake. The lake elevation is influenced most by the amount of inflow to the lake from upstream and the amount of water released over the dam to the Cape Fear River.

Town staff monitors lake level in relationship to the Cary/Apex Water Treatment Facility raw water intake. The top of pipe of the primary raw water intake is located at a height of 208.3 feet mean sea level, while the top of pipe of the lower intake is located at 204.25 +/- feet mean sea level. Raw water quality decreases at lower lake elevations, which can require additional operational measures at the Cary/Apex Water Treatment Facility to maintain finished water quality. Extension devices have been fabricated to allow adjustment of either intake.

When tracking lake levels at B. Everett Jordan Dam, staff maintains contact with the Department of Water Quality and the US Army Corps of Engineers to stay up to date on the most current operating procedures. Under normal circumstances, the US Army Corps of Engineers approved 1992 Water Control Manual for B. Everett Jordan outlines the operation for Jordan Lake as follows:

7-02. Overall Plan for Water Control. The plan of operation for Jordan Lake provides for maintaining a normal pool elevation of 216.0 feet m.s.l. throughout the year. Flood control storage space is reserved between elevations 216.0 and 240.0 feet m.s.l., with surcharge storage provided above the crest of the free-overflow spillway between elevations 240.0 and 261.5 feet, m.s.l. Releases for flood control are outlined in detail in section 7-04. Conservation storage between elevations 202.0 and 216.0 feet, m.s.l., is reserved for water supply, low flow augmentation, and water quality control. Immediately below the dam, a minimum instantaneous flow of 40 c.f.s. shall be maintained. This flow quantity is the 7-day, 10-year low flow frequency amount at the Jordan damsite (7Q10 flow). In practice, however, the minimum gate setting is typically a single service gate opened 4 to 6 inches, which produces a flow of approximately 130 to 200 c.f.s.. Jordan Lake shall also be operated to maintain water quality flow requirement of approximately 600 c.f.s. in the Cape Fear River at the Lillington streamflow gage throughout the year. Discharges from the multilevel water quality gates shall be maintained as described in section 7-05d. Rate of release changes will be made within the guidelines described in section 7-11.

The US Army Corps of Engineers and the NC Division of Water Resources use a computer model to forecast lake elevations, and Cary staff participates in conference calls and meetings, sometimes weekly, to monitor predictions for lake elevation changes.

Other Factors

Other factors that will trigger evaluation of the potential for water shortage conditions include:

Sudden loss of supplemental water supplies during periods of high demand.
The occurrence of a major water transmission main break, fire, or any other emergency that would require high volumes of water, such that demand could exceed supply.
Indications of short or long-term water quality concerns regarding Jordan Lake or other sources.
Accidental or intentional contamination of the water system
Level of interbasin transfers relative to Cary and Apex’s interbasin transfer certificate amount.
Drought Advisory issued by the NC Drought Management Advisory Council
Mechanical failure in the water treatment plant or distribution system
Inability to distribute water through part of the system

3. Procedure for Implementing Water Shortage Phases

If the Jordan Lake allocation storage level, Jordan Lake elevation, or other factors indicate the potential for a water shortage, the steps below are taken. Mandatory measures will remain in effect until declared otherwise by the Town Manager, and updates will be provided in the sequence outlined below.

STEP 1. The PW/UT Director (or designee) notifies the Town Manager.

STEP 2. If appropriate, depending on the cause of the water shortage condition, the Apex Public Works Director and Town Manager and/or representatives of bulk users are also notified. The Town Manager then determines if implementation of water shortage phases is appropriate.

STEP 3. PW/UT Director (or designee) develops a water shortage action plan

STEP 4. Once water shortage phases are implemented, the following notifications are made:

The Town Manager (or designee) notifies the Mayor, Town Council, neighboring municipal contract water recipients, and town government departments.
The Public Information Officer (or designee) will contact the media. The media, including television, news, and radio, will inform the public. PWUT’s (919) 469-4090 number will be provided if additional information is needed by the public.
The PW/UT Director (or designee) will contact Finance Customer Service and the Water Distribution System Operator, and distribute a general e-mail so Town employees can help provide accurate information to the public.
Finance Customer Service will call major water customers (both irrigation and water accounts) and inform them of the implemented measures.
The Water Distribution System Operator will contact the police communications center, and coordinate with bulk users.
Public Works and Utilities will supply fliers for distribution by field employees to place on customers’ doors or provide to customers that need more information.

STEP 5. Public Works Operations will continue repairing water leaks on a high priority basis.

STEP 6. Staff will regularly evaluate the ability to meet demand and modify water shortage action plan if needed.

STEP 7. At such time that the PW/UT Director determines that the need for water shortage declarations are no longer needed, the PW/UT Director will notify the Town Manager. The Town Manager will then declare the water shortage declaration to be over.