Plumbing Systems

Sources of Domestic Water

Domestic water is provided to the campus by the San Antonio Water System (SAWS). Generally, the SAWS service to the property is very good. The property is located within SAWS service level 8 and has a typical static pressure around 60 psi. Service is provided by large diameter (20-24 inch) border mains on Loop 1604, Babcock Road, UTSA Boulevard, and Valero Way.

SAWS is in the process of planning a main extension along UTSA Boulevard near Valero Way that will complete service loop around the campus. When completed, this will provide a higher level of reliability and improved quality of service to the campus.

Source 1: The 1604 Campus is served through a 12-inch service main fed from an 8-inch meter off of a 24-inch SAWS main located along Babcock Road. The 12-inch service main originates approximately adjacent to the proposed location for the baseball field and extends eastward towards the Thermal Energy Plant.

Source 2: The 1604 Campus is also served through a 16-inch service main fed from a SAWS line located along UTSA Boulevard. The 16-inch service main originates approximately adjacent to the center of the University Oaks Apartments and extends northeast toward the proposed University Center expansion.

Campus Distribution

The distribution of domestic water is generally accomplished through a loop extending from the two main sources, sized 10-inch to 14-inch, depending on location (Figure 17). The northern portion of the loop extends from the Thermal Energy Plant toward the proposed Academic Building (#6), then past the John Peace Library where it intersects the southern portion of the loop. The southern portion of the loop extends from Lot 6 towards the Science Building, passes to the north, and intersects the northern loop. Numerous distribution branches of various sizes feed into clusters of buildings from the service mains and distribution loop, the largest of which is a 14-inch branch extending toward the proposed Performing Arts Center from the intersection of the northern loop (10-inch pipe) and southern loop (12-inch pipe). In the past the on-site system has been extended on a project need basis. This has resulted in the sizing of mains that meet the needs of a specific project or building expansion, but do not correspond to the overall campus master plan. It is strongly recommended that a master utility plan be developed for the campus and that future expansions honor the direction of the master plan.

Existing Building Water Demand

Existing water demand for each of the existing buildings was determined using information included in the design analysis for the buildings. Refer to Figure 14.

Future Building Water Demand

Future water demand for each of the new buildings was determined by estimating the minimum number of plumbing fixtures required by the 2000 Universal Plumbing Code (UPC) for the estimated number of occupants. The UPC was also used to determine fixture unit loads assigned to fixtures. The number of occupants was estimated using the occupant density required by the 1997 Uniform Building Code to determine exiting requirements. The building's ratio of net area to gross area was assumed to be 0.80. Refer to Figure 15.

Current Capacity of Campus Domestic Water Supply (DWS) System

Based upon flow testing data of the existing system gathered by UTSA personnel, it has been determined that the system can be expected to deliver approximately 2480 GPM to building users at a delivery (residual) pressure of 42.0 PSIG.

Flow test information, gathered during normal campus hours of operation, occurred during a time when the existing buildings could be expected to consume approximately 1350 GPM. The flow test information showed a static system pressure of 55.0 PSIG. When a test flow of 1130 GPM was applied, the residual system pressure dropped to 42.0 PSIG. Combining the calculated consumption flow of 1350 with the observed additional flow of 1130 GPM yielded a total flow of 2480 GPM.

Future Construction Impacts to Campus DWS System

Based upon a future flow of 2800 GPM, unless modified, the future delivery (residual) pressure available in the campus water mains and loop will drop below 40.0 PSIG. Refer to Figure 16. Based upon an available system pressure of 40.0 PSIG, it is predicted that many buildings with plumbing fixtures located more than twenty feet above the ground will require the addition of domestic water pressure booster pumps.

Two alternatives to providing domestic water pressure booster pumps at each building are either to provide pressure booster pumps to the campus distribution system or to provide an additional water service connection to a SAWS main. The most likely location for providing an additional water service connection is at the 14-inch branch main located adjacent to the proposed Performing Arts Center. This branch main could be extended south to intersect the SAWS main at UTSA Boulevard. A detailed analysis should be completed to assess the costs and benefits of adding an additional connection to the SAWS main versus the addition of distribution system booster pumps.

New buildings in zones L and M should be served from a new distribution loop served from the 20-inch SAWS main located on Valero Way and the SAWS main located on the Loop 1604 access road.

Note: The preceding study of existing and proposed demand was completed in 1999 and was not modified as part of the 2004 update.

Fire Protection System Impacts

The site static water pressure as provided by SAWS is around 60 psi. Many of the existing facilities require the installation of fire pumps to ensure that adequate water pressure and flow is delivered under fire conditions to standpipes extending to the building roofs. It is anticipated that this approach will be applicable for future work. An alternate approach that could also be of value is to provide a centralized central fire pump facility and distribution system to serve a group of new buildings, thereby eliminating redundant pumping capability and reducing the need for on-site generator capacity.

Natural Gas System Impacts

Many of the buildings on the campus utilize natural gas for heat, water heating, and other uses. CPS currently provides natural gas to the campus. The CPS natural gas main runs parallel to the Loop 1604 access road and can be tapped to extend branch piping to serve any new development. Depending on the demand of the proposed thermal energy plant, the CPS main could be tapped to provide service. If the demand is very high, UTSA may need to negotiate service from a high pressure main also located in the Loop 1604 right-of-way. Final size and arrangement of the distribution lines should be coordinated at the time of actual project design to best accommodate the layout of adjacent academic buildings. Grey Forest Utilities also has gas installations on Loop 1604 and is capable of supplying gas to the campus.

Sanitary Sewer

Sanitary sewer service for the campus is provided by SAWS. There are three primary outfalls to the SAWS system that correspond to the three primary topographic lows on the property.

The existing sanitary sewer that connects Chisholm Hall and the center of the campus is inadequately sized for the new development that will eventually be built on the western side of the campus. The design team recommends building a new sewer system to connect the new buildings and athletic facilities as well as Chisholm Hall to the city sewer mains on the western edge of the campus, rather than replacing the existing sewers. This change would free up capacity in the existing UTSA sewers that serve the central campus.

The central portion of the campus as well as the new eastern academic buildings are connected to the existing sewer line located along the connector roadway. There are two options for sewers near BSE 1 – either reroute the existing sewer around the new building and connect to the existing lines east of the building, or build a new sewer to the south.

Sewer service to the easternmost parts of campus is problematic. This area can either be serviced by the existing main in the central tributary of Leon Creek or an offsite main can be extended to the main in Leon Creek just east of Valero Way. Use of the onsite main will restrict development of the southeast corner of the property or will require the installation of a lift station to address topographic drainage problems. The Leon Creek option will require an easement across property controlled by the Valero Energy Corporation. Two-inch sewer lines are shown at the recreation fields and the picnic pavilion at the eastern side of campus as well as at the picnic pavilions at Roadrunner Hill. These facilities will not have the amount of use required for larger piping. The two-inch lines, however, will require a small lift station. Eight-inch sewer lines could be installed in place of the two-inch lines, eliminating the need for the lift stations, but usage may not be heavy enough at these facilities for the eight-inch lines to work as effectively as the two-inch lines in conjunction with lift stations.