City updates Inner Harbor desalination plans after modeling; public voices concern over Baffin Bay and Hillcrest impacts

City staff and the design-build team presented updated modeling results and a demonstration‑plant status report Wednesday as the City of Corpus Christi moves forward with technical work for a proposed Inner Harbor seawater desalination plant.

At a briefing before a packed council chamber, the City’s program management director Brett Van Hazel said the demonstration (pilot) plant is under construction and that the project team will return with a design‑amendment request this month to advance design from roughly 10% to 60% and to develop a guaranteed maximum price. Consultant firms Kiewit (prime), GHD and Freese & Nichols described the modeling work the team used to test diffuser options and to predict whether operations would change water quality at the proposed intake or in the broader Corpus Christi bay system.

The design‑build team showed a new diffuser design that it said increases initial dilution compared with the diffuser concept used for the state permit. GHD’s hydrodynamic modelers said their “near‑field” simulations show the optimized diffuser produces stronger mixing at the point of discharge and that “far‑field” simulations that extend out through the harbor to the intake indicate salinity changes of roughly 1–2.5 practical salinity units (parts per thousand) at the intake location in the worst simulations. Consultants said typical modeled changes farther into Corpus Christi Bay and at the Harbor Bridge were below 0.5 ppt and that the ranges produced by the modeling sit within the historical variability observed in the system.

Kiewit’s presentation said the modeling work used multiple data sources, from port and NOAA bathymetry to ADCP velocity records and long‑term meteorological inputs, and ran multi‑dimensional dispersal calculations on a flexible 3‑D mesh. The team said full report text and the design deliverable (the engineered diffuser and construction documents) will be shared with the council; the consultants noted that raw model code and some proprietary solver inputs are part of the consultant’s intellectual property and not normally published verbatim. Staff said it will produce a public technical summary of findings and that design deliverables and a cost update will be presented to council on July 22 and July 29.

Public comment filled the chamber for more than three hours, with dozens of residents, fishing guides, clergy and community groups urging caution or urging the council to reject discharging desalination brine into local bays. Speakers repeatedly warned that Baffin Bay is a shallow, poorly flushed, hypersaline system; they called it the region’s “speckled trout mecca.” Many residents described long histories of industrial encroachment on predominantly Black neighborhoods such as Hillcrest and Washington Coles and urged the city not to approve projects—whether desalination discharges or rezoning requests—that they say further concentrate industrial activity near homes, churches and parks.

Opponents pressed the council to require independent third‑party review of the modeling results and an environmental impact study specific to Baffin Bay, to provide the public with full access to modeling inputs and outputs, and to consider non‑discharge disposal options (deep‑well injection, offshore discharge after additional review, pipelines to the Gulf, or industrial re‑use) before committing to surface water discharge. Supporters who spoke said the city needs additional drought‑resilient supplies and that a publicly managed desalination project can provide reliable local water if built and run responsibly.

What the consultants presented GHD said the team used two complementary modeling approaches: the near‑field work used core‑mix calculations to test diffuser geometry quickly and to evaluate initial dilution; the far‑field work used a three‑dimensional flexible‑mesh hydrodynamic and transport model (Mike 3 FM) to simulate how plumes would move, stratify and dilute across the inner harbor under hourly forcing and a full year of meteorological and tidal/river conditions. Model runs included multiple intake scenarios, plant operations and seasonal forcing; simulated results were compared with local velocity and water‑level records for validation. The design‑build team said their optimized diffuser increased computed initial dilution compared with the diffuser concept registered in the state permit and that far‑field calculations showed no sustained salinity stratification or persistent salinity increases in the harbor outside the immediate mixing zone. The consultants told council the modeled salinity changes at the Harbor Bridge and into Corpus Christi Bay were generally below 0.5 ppt and within historical variability. They cautioned, however, that modeling is an ongoing exercise and simulations will be refined as the design develops and additional site data are collected.

City and consultant next steps Staff said the pilot plant is under construction and on site; several process modules have arrived and are being installed. The city will bring a design amendment on July 29 to advance to 60% design and to develop a guaranteed maximum price. Staff also said it will publish a technical summary of the modeling and provide council a cost update July 22. The team also said they will continue to refine the diffuser and treatment design using lessons from the pilot plant.

Why people are still concerned Speakers from fishing organizations, neighborhood associations and faith communities said they were not reassured. Their requests included: (1) an independent, third‑party peer review of the hydrodynamic modeling output; (2) public release of a readable technical report of the Mike 3 results and the assumptions used in the model; (3) additional targeted sampling for PFAS and other legacy contaminants at the proposed intake and discharge locations and a plan to treat contaminants if found; and (4) consideration of alternatives to surface discharge into Baffin Bay.

Nut graf: why this matters The Inner Harbor desalination project is intended to deliver a drought‑resilient source of local water, but its planned intake and discharge locations sit in shallow, industrialized waters that local residents and guides use for recreation and livelihoods. Consultants reported small modeled salinity changes beyond the immediate mixing area, and staff emphasized that a pilot plant and additional engineering are underway. Still, the public debate is focused on risk: residents and fishermen want stronger independent review and safeguards before any surface discharge is permitted; city staff and project engineers say the diffuser design and operational controls can meet permit conditions and that the pilot plant will inform the final design.

Ending: next steps for council and public Council will receive a project cost update on July 22 and a design‑amendment request July 29 that would authorize the team to advance to 60% design and develop a guaranteed maximum price. Staff said a readable technical report summarizing the model results and their limitations will be published. Residents asked for a formal third‑party peer review and for staff to publish model inputs and assumptions; staff said they will propose a public technical summary and that they would seek council direction on additional peer‑review options.

Speakers (attribution whitelist) - Brett Van Hazel — Director, Program Management Office (project lead, City of Corpus Christi). Present: July 15 status briefing. (first referenced item timecode: 18555–18632) - Eric Sprinkle — Design executive, Kiewit (design‑build). (first referenced: 19197–19243) - Chris Benjamin — GHD (far‑field model lead). (first referenced: 19580–19617) - Dave Buzan — Freese & Nichols, coastal ecologist (ecological interpretation). (first referenced: 20704–20742) - Jim Klein — resident / public commenter (first referenced: 2862–2872 public comment). - Jason Hale — public commenter / fishing guide (first referenced: 5992–5997) - Lamar Taylor — public commenter / American Council (first referenced: 6048–6074) - Multiple members of fishing and conservation groups (Corpus Christi, Rockport and region) — public comment (various timecodes).

Authorities referenced - Texas Commission on Environmental Quality (TCEQ) discharge permitting (referenced by staff and consultants). - U.S. Department of Justice (mentioned in separate agenda item about Oak View Group; not part of the desal modeling)

Actions (formal steps/project items) - Design amendment request (upcoming): staff will bring a contract amendment to advance design from ~10% to ~60% and to establish a guaranteed maximum price (GMP). Date to council: July 29, 2025. (motion anticipated: delegation of authority to execute amendment within limits; status: planned) - Cost update to council: July 22, 2025 (staff briefing).

Discussion vs. decision - Discussion: Project technical briefing and public comment. - Decision pending: whether to approve the design amendment and commit to spending for 60% design/GMP. No final construction authorization has been made.

Clarifying details (selected) - Pilot/demo plant status: on site; modular equipment arriving; erosion control and discharge line installation in progress (delivery to Broadway wastewater plant for test discharge). - Modeling: near‑field (core‑mix) for diffuser optimization; far‑field (Mike 3 FM flexible mesh, validated against NOAA and ADCP) for intake and harbor‑wide salinity predictions. - Modeling outputs (team summary): worst‑case modeled salinity rise at intake 1–2.5 ppt; Harbor Bridge / Corpus Christi Bay changes generally <0.5 ppt in scenarios presented.

Meeting context - Engagement level: very high public turnout at the July 15 briefing; more than three hours of public comment followed the technical presentations. - Implementation risk: medium — technical and permitting work proceeding; cost and final GMP remain uncertain.

Searchable tags: desalination, Inner Harbor, Baffin Bay, Bay water quality, pilot plant, diffuser design, Kiewit, GHD, Freese & Nichols, public comment

Salience (assistant editorial scoring) - overall: 0.86 — the project implicates long‑term water supply, environmental risk in local estuaries, and substantial public expenditures. - impact_scope: regional — 0.72 - attention_level: high — 0.80

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