PROJECT OVERVIEW

The first phase of the New Braunfels Utilities’ (NBU) Sam C. McKenzie, Jr. Water Reclamation Facility (WRF) was constructed and commissioned in 2017. The facility discharges into the Guadalupe River just downstream of Lake Dunlap as well as the Guadalupe-Blanco River Authority’s (GBRA) canal. Due to the WRF’s discharge location in the river and its proximity to Lake McQueeney, the facility’s TPDES discharge permit includes stringent water quality limits, including a Total Phosphorus (TP) limit.

Rapid growth within the City of New Braunfels accelerated the need to begin design for the next phase of the facility to ensure additional treatment capacity would be available when needed. The wastewater influent organic loading was more concentrated than when the first phase of the WRF was designed in 2015. So, in addition to needing to build additional treatment units, improvements were necessary to the existing treatment units to maintain their original hydraulic treatment rating due to the increased organic loading.

During the preliminary design phase, the Lake Dunlap dam failed, significantly changing the river profile at the WRF outfall. NBU authorized Quiddity to perform a river survey to provide TCEQ the necessary information to maintain its stream model to properly assess water quality needs from this and other treatment facilities. For more on this unique river survey effort, check out our Guadalupe River Survey project highlight. This effort enabled TCEQ to verify the existing water quality limits in the TPDES permit were adequate and complete the ongoing permit renewal.

The dam failure also revealed bank erosion underneath the water surface at the outfall within the GBRA canal. A fast-tracked project to repair the bank erosion was initiated by NBU in coordination with GBRA. Design was completed in May 2022 and construction is awaiting the completion of an environmental survey in the canal to assess any mussel populations requiring relocation and/or protection.

SERVICE DETAILS

Quiddity provided design, survey, and construction management services to NBU for the expansion. The expansion design included 2 new 20 MGD peak flow influent screens to provide 100% mechanical redundancy; expansion of the existing lift station to 20 MGD firm pumping capacity including construction of a parallel wet well to house additional pumps and provide wet well redundancy; 3 MGD average daily flow biological treatment unit containing anaerobic, and aeration basins designed to biologically remove phosphorus via aerobic-oxic (AO) process with an anoxic selector for RAS conditioning; 10 MGD peak flow secondary clarifiers featuring the first Texas installation of submerged effluent launders instead of traditional weirs and baffles; 20 MGD peak flow dual-media automatic backwashing tertiary filters; 20 MGD peak flow ultraviolet disinfection basin; 20 MGD peak flow post-aeration and flow measurement basin upgrades; 3 MGD average daily flow aerobic digesters; submerged ceramic membrane thickeners for sludge thickening including 2mm fine screens for the membrane influent; addition of a new alum feed system for biological process support trimming on TP removal; replacement and expansion of the non-potable water (NPW) system with 2 vertical turbine pumps; expansion of the bleach feed system to provide chlorine residual for the NPW; addition of 3 new tri-lobe positive displacement blowers to the existing bifurcated blower bank serving both the liquid process and solids process; replacement and expansion of the existing 15 kV primary electrical service including constructing new service gear with redundant feeds and breakers for electrical reliability inside a new dedicated building; addition of a 12.47 kV 1.5 megawatt (MW) generator to run in parallel with the existing 1.5 MW generator; repurposing the existing primary 15KV electrical service building into a new low voltage electrical building with power distribution gear and MCC to serve the blower and lift station expansion; replacement of existing aged PLC and communication equipment and expansion of the plant wide SCADA monitoring and control system.

Due to the increase in organic loading, improvements made to the existing facilities included replacement of the existing coarse bubble aeration system to fine bubble aeration system; replacement of the 5 existing blowers; replacement of the existing dual media automatic backwash filter; replacement of the existing submerged membrane sludge thickeners. Additionally, all existing PLCs were replaced to upgrade to new security standards equipment.

Construction of the expansion was very complex in terms of sequencing, especially related to maintaining power to all existing MCCs for the various treatment areas while converting to a new primary service gear location with new duct banks. The sequencing plan included temporary power and/or generators at each of the 4 MCC locations at various phases of construction. This temporary power plan and switchover was coordinated with the various process areas that could be down at the given time for tying in new treatment units. Every existing treatment unit was taken out of service at various points in time to allow for the upgrades (4-independent areas without common flow split between each process). As a result of the necessary sequencing, construction will take up to 3-years to complete.