Detention and retention basin repair in San Antonio. Capacity restored to the original design.

Every detention basin, retention pond, and infiltration basin on a Texas commercial site was built to a specific design volume: a number on a drawing the original civil engineer stamped, tied to a 25-year or 100-year storm calculation that the city accepted at platting. That number is the basin's job. Sediment accumulation, vegetative overgrowth, slope failure, and outlet damage all chip away at it, and nothing on the property is measuring the loss until an inspector or a flood does.

Most of the basins we get called to had something visible go wrong first. An HOA board notices the back pond looks half full of cattails. A property manager opens a Notice of Violation from the city after a routine MS4 audit. A buyer's due-diligence team flags the basin behind Building C during a sale. Whatever the trigger, the underlying problem is almost always the same: the basin has been quietly losing capacity for a decade and nobody owned the maintenance.

Landscaping crews can mow the slopes and pull the woody growth. They cannot tell you how much storage volume the basin has left, and they cannot restore it. That requires a bathymetric survey to measure current bottom elevation against the design drawing, a sediment-removal plan with legal off-site disposal, slope regrading back to the engineered cross-section, and a post-construction survey to prove the restored volume matches the original number. That documentation is what gets filed with the city and what closes the compliance loop.