University of Texas at San Antonio
IN-36: Stormwater Modeling

UTSA hires our Job Order Contract Engineer to evaluate and calculate impervious cover in our Environmental Master PLan. Modeling is based on project specific boundaries dependent on location over the Edwards Aquifer. The Main Campus, located over the EA recharge zone is required to model utilizing the Texas Commission on Environmental Quality minimum standard according to the Edwards Aquifer Technical Guidance manual to meet compliance thresholds for treatment. Our Engineering report for the 2020 modification of the UTSA environmental master plan reports: Additional modifications since the 2015 WPAP Master Plan Reset include the March 28, 2018 (ID 13000609), for the East Campus Parking Lot & Office Building. This approval added a new parking lot and bus facilitates treated by two water quality basins and three VFS. On April 9, 2019 (ID 13000845)
TCEQ approved a net increase of impervious cover of 0.032 acres of impervious cover for installation of treatments systems to treat 9.557 acres of previously-untreated grandfathered impervious cover. The PBMPS for that project were rainwater harvesting, a grassy channel, two (2) new water quality basins.
The subsequent modification was approved on April 16, 2019 (ID#13000863) for a net increase of 1.86 acres of impervious cover for a parking lot located in the northwest portion of campus. This new impervious cover is treated by a Jellyfish® Filter System and an existing water quality basin 2. The most recent approval was for the UTSA RACE facility (ID#13000976) which increased the impervious cover by
2.9 acres and demolished three existing sand filter basins (5, 6, 7) which combined the treatment into one approved batch detention basin (#8). The currently-approved onsite impervious cover is 228.974 acres of which 137.05 acres is pre-existing and grandfathered. Please see treatment tables included in
the exhibits section of this application. An exhibit showing all approved and proposed Permanent Best Management Practices (PBMPs) is included in the exhibits section of this report.
Approximately 25.4 acres of additional impervious cover are proposed over the currently-approved 228.97 acres for a total of 254.37 acres of impervious cover upon approval of this plan.
Four (4) existing water quality basins (#1, #2, #3, & #5), three (3) existing bio-retention basins (#6, #9 & #10), one (1) existing jellyfish filter system, one (1) existing Vortech, two (2) proposed batch detention basins (#7, #8), and one (1) existing sand filter basin to be updated to a proposed batch detention basin (#4) are the Permanent Best Management Practices (PBMPs) for this site. All PBMPs have been designed in accordance with the TCEQ’s Technical Guidance Manual (TGM) RG-348 (1999 or 2005) to remove minimum 80% of the increase in TSS from the site. The existing Sand Filter Basin #4, which currently treats watershed “Midwest”, will be converted to a batch detention basin to be functioning prior to any proposed improvements within that watershed. Additionally, the proposed batch detention basins #7 and #8 will be constructed when impervious cover is constructed within the respective watershed.

The campus utilizes several stormwater practices to maximize our water budget and treat stormwater accordingly. Beyond required stormwater treatment in compliance with the Edwards Aquifer, the campus utilizes rooftop capture, vegetative filter strips and water quality controls to maximize water quality treatment to incorporate previously untreated impervious cover.

UTSA captures an treats stormwater at its main campus by means of 5 regional sand filtration basins, 4 bioswales located around the campus, along with various vegetative filter strips. These features capture rooftops, parking lots, sidewalks, and other impervious surfaces in compliance with Edwards Aquifer rules on water quality over the Edwards Recharge Zone. The Downtown campus captures and treats stormwater as a partner with the San Antonio River Authority and the City of San Antonio's efforts to capture and treat stormwater in the Downtown watershed around the San Antonio and San Pedro Rivers which are in non-attainment for e-coli. UTSA policy on water infrastructure is to capture condensate and utilize non-potable water for conservation methods in irrigation or tower make up water. The State Conservation Office also mandates that all state buildings will capture and reuse stormwater from rooftops on capital buildings. UTSA has recently developed target KPIs to reuse stormwater on capital projects on campuses off the aquifer recharge. Through 2 grants from the City of San Antonio, $1,057,407/ 2.7 million, UTSA has successfully implemented two new watershed treatments using bioswales and cisterns to capture over 18 acres of stormwater that was previously untreated.

https://www.utsa.edu/today/2018/05/story/StormWaterGrant.html
UTSA has a 4 new large bioretention facilities since 2019. We have a new bioretention at our downtown campus.