Jacobs engineers presented a preliminary concept for a single concrete/steel wall with multiple removable gate panels and diffusers intended to give the state seasonal control over flow and salinity exchange through the railroad causeway.

"We need to be able to import North Arm water," Jacobs' project lead said, and the firm described a five‑bay structure with paired gates: a lower orifice gate to allow controlled north→south flows and an upper weir gate to regulate south→north overflow. Engineers emphasized the operational challenge posed by salt encrustation and crystallization and proposed removable steel gate frames, strategic leakage and a diffuser system that would channel south‑arm water along contact points to limit encrustation.

Modeling work included full computational fluid dynamics (CFD) calibration against USGS measurements and simplified cross‑section runs to explore density and head differentials. Jacobs reported that when south‑arm head exceeds a threshold the south arm will push toward the north and can constrict incoming north→south flow; conversely density differences can drive north→south flow even without a large head differential. The engineers used exceedance statistics for head differentials and lake elevations to identify operating ranges and the need for a flexible design.

The memo circulated to the committee described geotechnical uncertainties, wave and scour risks, and the possibility that piles required to support the structure could drive much of the cost. Jacobs' early cost estimate included a wide band because pile depth and quantity remain uncertain; preliminary numbers discussed in the meeting put an order‑of‑magnitude capital estimate near $40 million with roughly $15 million for the superstructure and the remainder driven by piling and site preparation.

Committee members asked that Jacobs and the state 1) compare lower‑cost alternatives (e.g., rock/concrete blocks, culverts, temporary pumping) against the adjustable wall in terms of capacity to move brine and operational flexibility, 2) complete geotechnical borings to narrow piling needs, and 3) validate the proposed diffuser flushing approach for salt encrustation. Jacobs noted shorter‑term, lower‑cost options could include seasonal pumping to move north arm water under the causeway while a longer‑term structure is developed.