Pressure Maintenance and Capacity

Minimum Pressure Requirements

Section 290.44(d) in TCEQ’s current Rules and Regulations for Public Water Systems relates to the operational requirement that minimum pressures within a public water system (PWS) be maintained at 35 pounds per square inch (psi).  An exception to this requirement may be requested by a PWS and will be evaluated on a case-by-case basis.  To evaluate this type of exception request, the following definitions and guidance have been established:

Definitions

1. A potable water distribution line is a type of potable water main (defined per 30 TAC 290.38(65)) that directly conveys finished water (defined per 30 TAC 290.103(19)), which is under pressure from a pump station, clearwell, ground storage tank or elevated storage tank leading to a connection (defined per 30 TAC 290.38(16)). A potable water distribution line is subject to all applicable provisions of 30 TAC Chapter 290 Subchapter D.
2. A water transmission line can be classified as either a potable water transmission line or a raw water transmission line. A water transmission line cannot directly convey water to a connection or a potable water distribution line.
3. A potable water transmission line is a type of potable water main (defined per 30 TAC 290.38(65)) that directly conveys finished water (defined per 30 TAC 290.103(19)). These lines are under pressure from a pump station, standpipe or elevated storage tank located at a water production or water treatment facility under the control of a PWS to an off-site pump station, ground storage tank or elevated storage tank. A potable water transmission line is subject to all applicable provisions of 30 TAC Chapter 290 Subchapter D.
4. A raw water transmission line is a type of water main not defined by 30 TAC 290.38(65) but is owned or operated by a PWS which directly conveys raw water (defined per 30 TAC 290.103(33)) under pressure from a water source. Water sources may include a well, wellfield, surface water, or any tank or structure that is used to store raw water, to a location for treatment required so that the untreated water complies with drinking water standards as defined by 30 TAC 290.38(24).  A raw water transmission line is subject to the applicable provisions of 30 TAC 290.39.

Minimum Pressure Exception Review

To be considered for an exception under this guidance, the PWS is required to demonstrate to the TCEQ’s satisfaction that the water transmission line has been designed to maintain a minimum internal pressure of 5 pounds per square inch gauge (psig) above any external hydrostatic pressure.  This includes but is not limited to any combination of expected maximum seasonal groundwater elevation and ponded surface water elevation.

At the time of plan submittal, the design engineer must provide documentation, as outlined below, supporting operation of the water transmission line at a pressure that is less than 35 psi. 

1. Provide a map showing the route of the proposed transmission line. The map must show locations where the water line will cross, or be in proximity to:
   1. permanent water bodies that are known or suspected to influence the elevation of the groundwater at the pipe location;
   2. flood plains;
   3. natural or man-made wetlands;
   4. hydric soils;
   5. areas of short-term localized ponding resulting from either natural topography or area land development;
   6. street or railroad crossings; and,
   7. any locations where the groundwater is known, or suspected to be impacted, by subsurface releases of hazardous chemicals, petroleum products, or microbial contamination.
2. For each pipe segment as shown on the map, provide the:
   1. trench depth;
   2. pipe diameter;
   3. minimum operating pressure of transmission line; and,
   4. seasonal height of ground water and depth of ponded water. Provide sources of information for seasonal high groundwater depth, ponded water depth, and soil types.
3. Submit a pressure study to support the provided operating pressures. For segments that may be impacted by contaminated groundwater, include the type of contamination, contaminant source if known, and if the contaminated groundwater is or has been the subject of remediation activity.  Discuss the means by which pressure will be maintained in the line segment during periods of no flow. 
4. If the means to maintain the pressure in the transmission line requires the use of electrical powered equipment, discuss electrical reliability including length of power outages that would affect the ability of electrical powered equipment to operate reliably and means to address maintaining pressure in the transmission during power outages.
5. Discuss the standard operating procedure to be employed to ensure that the required minimum pressure is maintained in each pipe segment.  This standard operating procedure will be subject to review when requested by TCEQ staff.

Pressure Maintenance Facilities - Industrial Applications

In applying for an exception to the minimum pressure maintenance capacity requirements for a public water system (PWS), the system must provide equal or greater protection of public health than would be achieved by meeting the minimum requirements of 30 TAC 290.39(l). For the purposes of this guidance, “Industrial Applications” refers to those systems classified as nontransient, noncommunity systems as defined in 30 TAC 290.38(56). Per 30 TAC 290.45(d), all nontransient, noncommunity systems providing groundwater, surface water, or groundwater under the influence of surface water must have a minimum pressure tank capacity of 220 gallons. In the case of pressure maintenance capacity requirements, noncommunity systems are evaluated differently due to their unique characteristics and ability to discontinue service in the event of pressure maintenance problems.

Exception Review

The supporting documentation for this type of exception will require pressure monitoring at various locations in the PWS’s distribution system, computer analysis of the distribution network, or other equivalent methods of analysis (which are approved by the TCEQ on an individual basis).  This section only addresses the minimum requirements for distribution system monitoring to support the exception request. The supporting documentation must be sufficient to ensure that minimum operating requirements in 30 TAC 290.46(r) are met during normal and emergency conditions. Appropriate distribution sites must be selected to ensure that critical locations representing the lowest possible distribution system pressures are monitored. Requests for this type of exception have two steps: 

1. Monitoring Protocol
2. Pressure Testing and Monitoring Report 

The Monitoring Protocol is a written plan that defines the scope and duration of pressure monitoring. Once the Monitoring Protocol is reviewed and approved by the Technical Review and Oversight Team (TROT), a letter is sent to the PWS approving the Protocol as submitted, approving the Protocol with revisions, or rejecting the Protocol (and possibly offering an alternative). The PWS uses the Protocol to install pressure recorders and monitor pressure levels in accordance with the approved Monitoring Protocol.  Once the data is collected, the results of the pressure testing are submitted to the TCEQ in the Pressure Testing and Monitoring Report.  The submittal of this Report completes the exception request process.

If a computer analysis of the distribution network is proposed by the system in lieu of in-situ pressure monitoring, the analysis must be submitted by a licensed professional engineer.

Monitoring Protocol

The Monitoring Protocol details the characteristics of the industrial facility, and the PWS’s approach to selecting and monitoring pressure levels in critical areas of the distribution system. The following items must be addressed in the Protocol: 

1. Description of the industrial facility (i.e., type of industrial application that the PWS does, types of processes involved in day-to-day operation, etc.)
2. Identification of locations of suspected low pressure (critical points) in the distribution system, with respect to the distance and elevation from the source.
3. A distribution system map with the locations of the critical points must be provided.
4. Inventory of facilities, such as ground storage tanks, pressure tanks, service tanks, etc. These facilities must be identified in the distribution system map.
5. Proposed duration of pressure monitoring at the critical points identified in Item 2. The PWS will be required to install a pressure recorder at each critical point and monitor the pressure continuously. Typically, 90 days is acceptable to show changes in plant operation and water demand. The selected test duration should consider various scenarios that may result in pressure fluctuations, such as change over from one pump to another, addition of pumps, changeover to auxiliary power, or an additional power source, etc.
6. Documentation that the system has a proactive cross-connection control program with at least one person trained in a TCEQ-approved 16-hour customer service inspector course. This can be accomplished by providing the following:
   1. A copy of the policy or internal rules that require customer service inspections, backflow prevention, and testing of backflow prevention assemblies.
   2. A copy of the latest Customer Service Inspection Certificate filled out by the appropriately licensed individual documenting the presence or absence of cross-connections.
   3. If a backflow prevention assembly(s) is used, a copy of the Backflow Prevention Assembly Test and Maintenance Report showing that the assembly is functioning correctly.

Information on Cross-Connection Control and Backflow Prevention is available online or you may call (512) 239-1075 and ask to speak to a member of the TCEQ Cross-Connection Control Program.

6. If the pressure testing conducted shows a compromise in the integrity of the water distribution system, the PWS must have measures in place to address any adverse effects during the planning for the pressure test.
7. The system must have a licensed water operator for all activities related to the operation of a PWS. An approved Monitoring Protocol does not exempt the water system from maintaining minimum pressures and flows during the monitoring period. If it is found that minimum pressures are not maintained during the monitoring period, an exception to minimum pressure maintenance requirements will not be considered by the TCEQ until appropriate corrective action(s) are implemented by the PWS.

The Monitoring Protocol must be submitted to the Technical Review and Oversight Team for approval at the following address:

Technical Review and Oversight Team (MC 159)
Texas Commission on Environmental Quality
P.O. Box 13087
Austin, Texas 78711-3087

Pressure Testing and Monitoring Report

Once the Monitoring Protocol is approved by the TCEQ, the PWS must install pressure recorders at the approved critical points and continuously monitor and record the pressure levels for the duration specified in the approved Monitoring Protocol.

• Normal operating pressures must not be below 35 pounds per square inch (psi) at any time during the test. Operating pressures during a fire flow event must not be below 20 psi at any time during the test. All lag times during changeovers must be recorded and correlated with the pressure changes recorded in the distribution. 

Once the pressure testing and monitoring is completed, the PWS must summarize the results in a Pressure Testing and Monitoring Report and submit an exception request to 30 TAC 290.45 (Minimum Water System Capacity Requirements) in writing to the TCEQ TROT. The submittal should include the Pressure Testing and Monitoring Report and a copy of the approved Monitoring Protocol. Staff will review the request and develop a written response.

If an exception is granted, the approval will include a condition in the letter to state the following:

“The system must maintain a minimum pressure of at least 35 psi throughout the distribution system during normal operations, and a minimum of 20 psi during emergencies, as specified in 30 TAC 290.46(r). If the minimum pressure cannot be maintained, the water system must cease operations or must provide another source of potable water (i.e. bottled water) for industrial employees until sufficient pressure can be restored and maintained.”