WATER ISSUES RELATED TO THE USE OF LAKE TEXOMA

Excerpt from March 2, 2005 Dallas Long Range Water Supply Plan (LWRSP) briefing to City Council

LAKE TEXOMA ISSUES

Why does the Lake Texoma option include treatment costs?
Texoma water presents unique chemical characteristics compared with other water sources considered in LWRSP Update:

• Presents significant taste, treatment and cost challenges, especially related to desalination, which is the process of removing salt – sodium/sodium chloride from water. Salty water is commonly referred to as brackish water.
• Salt cannot be removed by chemical treatment, which is the common water treatment process, and requires forcing water through a membrane to remove the salt. This technology is known as Reverse Osmosis (RO). See page 35 for a list of jurisdictions that currently use this treatment method.
• Running brackish or salty water through a membrane requires that it be forced at very high pressures. This results in high electrical costs, much higher than required to clean non-brackish water using chemicals.
• As the brackish water is forced through the membrane the water remaining in the brackish side of the membrane increases in its concentration of salt. The remaining salty water, or reject water, must then be disposed of .
• Concerns related to long-term health impacts on a significant portion of the population suffering from hypertension have suggested reduced levels of sodium content in treated water.
  This is a potential concern with Lake Texoma water.
• Use of state-of-the art ozone disinfection presents another regulatory challenge with regards to disinfection by-products that are known carcinogens as defined by the US EPA Safe Drinking Water Act.
• Treatment method necessary for Texoma water is unlike treatment currently used by
  DWU and is not necessary for any of the other options studied. The LRWSP report included desalination costs for Lake Texoma water which provides treated water. In order to provide another basis for comparison, the tables included below have added conventional treatment costs to each of the other sources:

¹The Texoma Option B delivers potable water to the Elm Fork Water Treatment Plant. Other alternatives, except for conservation and direct reuse, provide raw water to the treatment plants. In an attempt to provide an equitable comparison, the unit cost for the remaining alternatives have been increased by the unit cost of water treatment ($0.37 and $0.25, for 30-yr and 50-yr, respectively) since the other options do not include conventional water treatment. The debt service is calculated at a rate of $0.97 per gallon of capacity amortized at a rate of 6% for 30 years. The annual O&M is $0.06 per 1000 gallons, a value that corresponds to the current treatment cost at the Elm Fork Water Treatment Plant less labor and high service pumping.

²The Texoma Option B alternative has a treatment capacity 1.2 times the annual supply (flow). All other alternatives, except conservation and direct reuse, have a treatment capacity of 1.6 times the average annual supply (flow).

Why does the North Texas Municipal Water District use Texoma as a source?
• NTMWD practices scalping, in which they use water from Lake Lavon and
Lake Ray Hubbard when in flood release, but are credited towards their permitted use of Lake Texoma – NTMWD’s permit specifically allows this practice at Lavon and Ray Hubbard. (Note: NTMWD is North Texas Municipal Water District)
• When Texoma water is used, the amount of Lake Texoma water is limited by the ability to blend it with Chapman Lake and Lake Lavon water.
• NTMWD does not currently use ozonation as a primary disinfectant.

 What steps need to be taken to obtain additional reallocation of water from Lake Texoma?

• Solicit and obtain support in Congress for reallocation of water in the lake.
  Support must be obtained from members of the Texas and Oklahoma delegations.
• After a bill is passed and is signed by the President, the US Army Corps of
  Engineers (Corps) must complete a reallocation study that addresses the hydrologic, economic and environmental impacts of the reallocation.
• Dallas will have to file water rights and inter-basin transfer permit applications with the Texas Commission on Environmental Quality (TCEQ).
• After the reallocation study is complete, and the water rights and inter-basin transfer permits are approved, Dallas can enter into a contract with the Corps for storage rights in Lake Texoma.
• Dallas will then have to apply to the TCEQ for a discharge permit for the brine (the desalination waste discharge).
• Dallas will also have to file an application to the Corps for a Section 404 permit to construct an intake and conveyance pipelines.
• Upon completion of those permits, the City could then implement the Texoma Water supply.