Reclaimed Water System

CobbFendley, serving as District Engineer, was responsible for the planning, design and construction management of a reclaimed water plant and multiple phases of a distribution system for SMCMUD. SMCMUD wanted to provide their customers with an alternate lower cost source of water, to promote water conservation, and extend the life of their water wells. The planning phase included a feasibility study analysis of the District’s overall water use, irrigation meter consumption, and identified high water users. The feasibility study determined a pay-back duration of 20 years for the revenues to exceed the capital expense.  SMCMUD was determined to pay for the system without incurring financing costs, so they utilized sales tax revenues and divided the projects into phases allowing them to pay with cash on hand.

An overall distribution line layout was developed and CobbFendley created a WaterCAD model of the reclaimed water system to determine proposed pipe diameters and associated water pressures. The model was also used to assist customers with design of their private fire suppression systems. Using results of the reclaimed water model, one customer was able to save $400,000 by not having to upgrade the potable water lines and build an onsite tank for their fire protection needs.

CobbFendley obtained a permit for Type I reuse water from the TCEQ, which included developing an operation and maintenance manual for the system. SMCMUD is currently using the Type I water to sell to property owners for irrigation and fire protection, using it as washdown water at the plant, and selling it for non-potable truck refilling.  TCEQ allows Type I water to also be used for golf course irrigation, amenity ponds, toilet flushing, and livestock pastures.

The reclaimed water plant is located at the District’s wastewater treatment plant and includes four booster pumps, a cloth disc filter, conversion of an abandoned clarifier into a ground storage tank, transfer pumps, two 8,000 gallon hydropneumatic tanks, piping, and electrical upgrades. Converting the abandoned clarifier basin into a reclaimed water storage tank saved the District $400,000 in capital expense. The basin holds 500,000 gallons of water and is an open-top style.  The cloth disc filter was manufactured by Ashbrook to fit in an existing dechlorination basin therefore saving another $100,000 by using an existing concrete structure. The cloth discs can be removed and replaced independently so that the system can stay online during maintenance.  Three booster pumps are sized for 300 gpm and one jockey pump provides 100 gpm.

SMCMUD had the system online before the state-mandated surface water conversion date of January 1, 2016. The Lonestar Groundwater Conservation District (LGCD) had mandated that all public water systems reduce their groundwater usage by 30 percent. CobbFendley prepared the application for early conversion credits to LGCD.  When the system was put online in 2014, the MUD started accruing credits from the conservation district because they converted early, creating a financial impact to the district. They were able to accrue 98 million gallons of credits before the January 1, 2016 deadline.

Reclaimed Spray Line Supply

The distribution system was constructed in commercial areas and 50+ year old neighborhoods with multiple existing utilities in the right of ways and easements. Existing sanitary sewer easements were utilized when possible to limit construction in the roadways. In general, the reclaimed water lines run parallel to the existing gravity sewers.  Several petroleum/gas pipeline company approvals were obtained to cross gas and petroleum mains. Level B SUE was performed to identify a potential gas line conflict during design that eliminated the cost of having the gas line relocated during construction. Residents along the reclaimed water lines had the option of connecting their existing sprinkler system or paying for a hose bib connection.  The distribution project began in 2014 and has consisted of four phases to date:

Phase 1 of the distribution system included approximately 21,250 linear feet of reuse water main ranging from 4-inch diameter to 16-inch diameter. The distribution line leaving the reclaimed plant is 16-inch which extends through a commercial area.  The reclaimed water system includes taps and meters for sale of the Type I reclaimed water to District residents and business owners.

Phase 2A and 2B of the distribution system included approximately 17,800 linear feet of reuse water main ranging from 4-inch diameter to 12-inch diameter.

Phase 3A, 3B and 3C of the distribution system included approximately 11,320 linear feet of reuse water main ranging from 4-inch diameter to 8-inch diameter.

Phase 4 of the distribution system included approximately 7,800 linear feet of reuse water main ranging from 4-inch diameter to 6-inch diameter.