Water treatment plant, storage tank and intake design in Texas

What it covers

We design and upgrade the treatment and storage side of a public water system: groundwater and surface water treatment, filters, disinfection, chemical feed and controls, clearwells, ground and elevated storage tanks, and raw water intakes. The work includes the buildings and site work around them. Utilities, towns, water supply corporations and districts bring us in for a plant or tank of their own. Developers bring us in when a new system needs one.

This page covers the plant, the tank and the intake. For wells, the Chapter 290 capacity tiers and the TCEQ approval package, see public water system design. For booster stations, see pump and lift stations. For mains and pressure, see water distribution.

When you need one

• The plant is short of capacity. TCEQ requires treatment capacity that always stays above the system's maximum daily demand.
• The plant keeps missing its turbidity goals after a performance evaluation and tuning, or its equipment has reached the end of its life.
• An existing plant or tank needs repair, and the owner needs a ranked list to budget and fund.
• Growth calls for more storage. Chapter 290 sets storage minimums per connection.
• The system is adding a surface water source, or changing over to one, which can change what it needs to treat and store.

What the Texas rules require

TCEQ's design rules for public water systems are in 30 TAC Chapter 290, Subchapter D. A Texas licensed professional engineer designs and seals the plans, and TCEQ approves them before construction.

Treatment plants. A plant sits on well-drained ground, not subject to flooding, at least 500 feet from a sewage treatment plant or land irrigated with sewage effluent, with an all-weather road. The site choice has to account for disposal of the plant's own liquid and solid wastes. All groundwater is disinfected. Surface water gets complete treatment: pretreatment disinfection, taste and odor control, continuous coagulation, sedimentation, filtration, covered clearwell storage and terminal disinfection. The process has to achieve at least 2-log removal of Cryptosporidium, 3-log removal or inactivation of Giardia and 4-log removal or inactivation of viruses before the water reaches a customer. A package plant meets the same design criteria. An innovative or alternate process needs pilot data, or data from a similar full-scale plant, showing it will meet the drinking water standards.

Storage tanks. Clearwells, standpipes, and ground and elevated tanks are covered, and are designed, fabricated, erected, tested and disinfected in strict accordance with current AWWA standards. They are painted and maintained to those standards too, and new coatings must meet ANSI/NSF Standard 61. No tank sits within 500 feet of a sewage treatment plant, land spray irrigated with its effluent, or land where sewage sludge or biosolids are applied. Each tank has a liquid level indicator at the site. Inlets and outlets are placed so water does not short-circuit or stagnate, and a clearwell used for disinfectant contact time is baffled. Tanks sit in a lockable building or behind an intruder-resistant fence, unless they are pedestal tanks with locked doors and no outside ladders. Every ground, elevated and pressure tank is inspected once a year.

Raw water intakes. We design intakes to these rules. The intake is placed to get the best raw water the source offers. It cannot sit in an area of heavy siltation, within 1,000 feet of a boat ramp, marina, dock or floating fishing pier open to the public, or within 500 feet of a sewage treatment plant or effluent-irrigated land. A 200-foot restricted zone around it is closed to recreation. It draws from a variety of depths so the system can take water when the reservoir is low, and it has screens or grates against debris. TCEQ staff evaluate a proposed intake location on site before final design. A new surface water source also needs source water quality data before TCEQ approves it.

For the Colorado rules, see water treatment in Colorado.

What we do

1. Start from the records and the water. We read the plant's operating records, the last state inspection and the water analysis, and sort what tuning can fix from what needs design.
2. Size the facility. Treatment capacity is set against maximum daily demand, and storage against the Chapter 290 minimums for the system's connection count. The minimums are a floor, not a design.
3. Pick the process. Iron and manganese call for oxidation and filtration, and the right process depends on pH, the other minerals in the water and how the plant will be run. Bench or pilot testing on the system's own water settles media life and vessel size where it matters.
4. Site and design the tank. We site and size the tank, check its effect on pressure in a hydraulic model, and specify it to the AWWA standards the rule requires. For an existing plant or tank, we start with an assessment and rank the repairs so the owner can budget and apply for funding.
5. Phase the work. We plan upgrades in phases so the plant keeps serving customers during construction.
6. Prepare the plans, the specifications and the funding report. We prepare the engineering reports and cost estimates that loan and grant programs ask for. The Texas Water Development Board's Drinking Water State Revolving Fund covers planning, design and construction.
7. Plan for construction. We can stay on through construction. For a tank, we plan the test water discharge around its own volume, drawdown rate and height.

What you get

• A capacity and process answer before design, checked against Chapter 290 and, for storage, a hydraulic model.
• An engineering report, plans and specifications for the plant, tank or intake in your scope, checked by an engineer who did not write them and sealed by a Texas licensed professional engineer.
• Cost estimates and the engineering report a funding program asks for, when the project needs funding.

What affects time and cost

• The source water. Surface water needs a full treatment train. Groundwater may need only disinfection, unless the water analysis calls for more.
• Testing. A new or alternate process needs pilot data, or data from a similar full-scale plant, before TCEQ approves it.
• The site. Floodplain, separation distances from sewage plants and effluent-irrigated land, and road access all limit where a plant or tank can go.
• An intake location. TCEQ's on-site evaluation comes before final design.
• Keeping the plant running. Phased construction protects service and adds sequencing.
• Funding. Programs want a defined scope, a cost estimate and an engineering report before they commit money.
• TCEQ's clock. TCEQ asks for detailed plans at least 30 days before you need comments, and it does not promise action in that time. TCEQ decides every submittal, so we never promise an approval date.