Council tables $1.86M Garver amendment after engineering questions about treatment basins

Lago Vista City Council on Oct. 2 tabled consideration of a contract amendment with Garver Engineering that would add design and construction‑administration work for rebuilding process basins and TLAP irrigation work for the city’s wastewater expansion, citing newly raised structural concerns and uncertain permit requirements.

Council paused the amendment after Garver told the council that record drawings and subsequent structural review suggest two existing process basins (an aeration basin and an aerated sludge holding tank) and one clarifier likely fall short of current concrete design standards. Garver said that, rather than retrofitting uncertain concrete conditions, rebuilding those process basins would be the safer long‑term approach. The proposed amendment the council considered would have added engineering scope that Garver estimated at about $1,864,090 and increased the expected construction cost estimate from roughly $29 million to as much as $47 million if the basins are rebuilt.

Why council paused: Garver said its visual inspection initially suggested the basins could be reused, but a later review of original record drawings and concrete specifications flagged low PSI mixes, unclear water‑cement ratios and inadequate rebar sizing/spacing for water‑bearing structures under ACI 318/350 standards. Garver told the council that retrofit options (for example adding buttresses or plates) are not favored by its structural engineers and that a…