City outlines near‑term water supply gains, pilot desal testing and modeling for Inner Harbor site

City Manager Peter Zanoni and Corpus Christi Water staff gave the City Council a multi‑part update on the city’s short‑ and mid‑term water supplies and technical work on the proposed Inner Harbor water treatment campus. The presentation covered reservoir responses after June rains, new interruptible and groundwater supplies, progress on reuse and brackish projects, and the schedule and goals for the desalination demonstration pilot and near‑/far‑field mixing model.

The update matters because the city is pursuing multiple new sources to reduce reliance on Choke Canyon and Lake Corpus Christi (stage restrictions remain) and is moving from planning into pilot testing and detailed engineering at the Inner Harbor site. Staff said several decisions made in the next 3–6 months will affect project costs, permitting inputs to TCEQ and the timing of any full‑scale plant.

Combined watershed response and supply projects: Drew (Corpus Christi Water) reported that heavy rain June 13–16 raised combined western lake levels modestly (combined western supplies rose from about 14.7% to 15.4% in the week reported). Lake Corpus Christi saw the largest inflow; parts of Cho Canyon experienced a temporary “tailwater” effect that required closing gates for safety and operations. Drew said the rain did not end stage‑3 conservation but improved short‑term storage and re‑confirmed the need to develop multiple alternative supplies.

Interruptible and groundwater sources: Staff said Lake Texana is full after heavy east‑side rains and the river authority offered the city interruptible water (about 4,500 acre‑feet). The city’s negotiated memorandum of understanding with the South Texas Water Authority is still in progress, and the Nueces River groundwater well project has reached administrative completeness with TCEQ permitting processes. City staff said contractors are drilling wells and that the well‑drilling program aims to bring a partial supply online in the coming months; the well cluster program is expected to produce roughly 13–15 million gallons per day once all eight wells are completed (targeted by August in staff remarks).

Reuse and long‑term alternatives: Zanoni and staff described the Garver reuse/source‑water characterization study that will take about 12 months and will evaluate options including direct or indirect potable reuse. Staff emphasized they will present reuse options to council before selecting a path; El Paso remains an example of utilities directly reusing treated effluent into distribution, while other options include indirect potable reuse or conveyance to treatment works.

Inner Harbor demonstration and modeling: The city’s design‑build team and consultants reported that the Inner Harbor demonstration (pilot) plan is moving into construction of the pilot discharge infrastructure this month with equipment deliveries and commissioning to follow. The demonstration schedule includes site work, commissioning and then a continuous 30‑day run period required by TCEQ as the minimum demonstration period; staff noted the 30‑day period is the regulatory minimum and additional run time would increase cost. The consultant team (GHD/Kiewit) completed the hydrodynamic model domain in May and is now running near‑ and far‑field scenarios that will be presented to council on July 15. Staff said the hydrodynamic work will be used to design the pilot/full‑scale diffuser and evaluate mixing, salinity and dissolved‑oxygen responses under a range of flows and meteorologic conditions.

Costs, schedule and next steps: Staff summarized recent contract activity (phase‑1a work completed June 1; phase‑1b design work underway) and said the next major decision point will be a guaranteed maximum price (GMP) or the construction‑notice to proceed; staff said the GMP/phase‑2 amendment is anticipated later this summer. The pilot demonstration will be executed as a time‑and‑material amendment so the city will see actual invoices rather than a large single lump‑sum pilot payment; staff explained the change was deliberate after designers’ and constructors’ differing estimates. Council asked about the demonstration length (TCEQ minimum is continuous 30 days) and whether the pilot should be run longer to observe seasonal conditions; staff noted longer pilot operation is possible but will increase monthly costs substantially because equipment and generator rentals are expensive.

What’s next: • GHD will present near‑/far‑field modeling scenario results to City Council on July 15; those results will inform diffuser design. • The pilot discharge line work is scheduled to start next week and equipment delivery/installation will follow; a 30‑day continuous demonstration run will follow commissioning. • Staff will return with the phase‑1b GMP amendment for council consideration later this summer, and will provide periodic cost updates as the design‑to‑cost process proceeds.

Ending: Council members asked staff to provide more detail on the pilot costs and to present the modeling results publicly; staff said they will return with the GHD modeling presentation on July 15 and with the GMP amendment for consideration when the design and cost estimate are sufficiently mature.