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Harlingen details multi‑million dollar drainage plan after Sept. 15 '50‑year' storm
Summary
City Engineer Lis Vargas told the Harlingen City Commission the Sept. 15 storm was a '50‑year' event and outlined a series of district projects — including upsized pipelines, detention ponds and a 3.2‑mile conduit on Commerce — and funding bids to FEMA and TWDB to reduce recurring street flooding.
Harlingen city engineers presented a series of infrastructure projects and ordinance updates on Oct. 2 aimed at reducing street flooding after the Sept. 15 storm that dropped about 6 inches of rain in two hours.
"It was classified as a 50‑year storm," City Engineer Lis Vargas said, adding that citywide water receded in two to three hours and that cleaned storm inlets and underground pipes played a crucial role in performance. Vargas told commissioners the city’s drainage systems were in many places undersized — with 12‑, 15‑ and 18‑inch pipes on major collectors — and that topography and rapid urbanization compound the problem.
Vargas laid out ongoing and planned projects across five districts. District 1 work includes the Pickins/Davis pipeline upsizing (about 3,600 linear feet; estimated cost $1.96 million) and Adams Crossing improvements (adding 1,600 feet of 36‑inch pipe; ~$627,000). In District 2, the Loano regional detention pond — about 15 acres and capable of detaining more than 20 million gallons — is under construction and was credited with storing runoff from the recent storm. Vargas said the Loano pond is roughly 85% complete.
The presentation also described major corridor work: a proposed 10x10 box conduit on Commerce Street roughly 3.2 miles long, and a West Street 10x10 box about 1.5 miles long. Both projects are intended to handle high‑intensity storms and would discharge into the Arroyo Colorado; Vargas said the Commerce conduit is designed to address intersections that currently flood in 100‑year events. Multiple grant applications for FEMA BRIC and TWDB funding were discussed; Vargas said some earlier BRIC submittals were unsuccessful and staff will reapply next year with updated technical documentation.
Vargas described recent ordinance changes intended to make new development more resilient: since 2020 the city has required 50‑year detention ponds for new subdivisions and 25‑year storm sewer underground systems, and in 2023 adjusted freeboard and floodplain rules in chapter 105. "Harlingen is the only city in the valley that requires a 25‑year storm sewer system; others require 10‑year systems," she said.
Commissioners asked about property ownership and lower‑cost mitigation steps such as dredging private lake features used as informal detention. Vargas and other staff said dredging could help but would require grants or property‑owner agreements; city money on private parcels would present legal and policy constraints. Vargas also said the city will post the full presentation online after delivering it to the commission.
What’s next: Vargas said the city’s drainage master plan is due in May 2025 and will provide an inventory of infrastructure and conceptual projects; the city will continue pursuing BRIC/TWDB funding rounds and expects more grant decisions and design milestones over the next 12 months.
