Under Phase I of the TPDES Stormwater Program , operators of large and medium MS4s require a TPDES permit authorizing them to discharge pollutants . Medium and large MS4 operators must submit comprehensive permit applications and are issued individual permits . A proposed stormwater management program must be developed that would meet the standard of reducing pollutants to the maximum extent practicable . Stormwater management programs for medium and large MS4s include measures to :
• Identify major outfalls and pollutant loadings
• Detect and eliminate non-stormwater discharges to the system
• Reduce pollutants in runoff from industrial , commercial , and residential areas
• Control stormwater discharges from new development and redevelopment areas
Only a select subset of small MS4s , referred to as regulated small MS4s , are required to have Phase II TPDES stormwater permits ( No . TXR 040000 ). Regulated small MS4s are defined as ( 1 ) all small MS4s located in urbanized areas as defined by the Bureau of the Census and ( 2 ) small MS4s located outside of a UA but designated by TCEQ . An urbanized area comprises one or more central places plus the adjacent densely settled surrounding area ( urban fringe ), together having a residential population of at least 50,000 . Urbanized areas in Texas have ( 1 ) an overall population density of at least 1,000 people per square mile or ( 2 ) are so designated by a regulatory agency . Regulated small MS4 operators may choose to be covered by an individual permit , by a general permit , or by a modification of an existing Phase I MS4 ’ s individual permit . Some regulated small MS4s in UAs may be eligible for a waiver from TPDES stormwater permitting requirements .
Regulated small MS4s are required to design their programs : |
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To reduce their discharge of pollutants to the maximum extent practicable |
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To protect water quality |
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To satisfy the appropriate Clean Water Act water quality requirements |
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