California Water Boards' Annual Performance Report - Fiscal Year 2017-18
REGULATE: NPDES STORMWATER
MUNICIPAL STORMWATER PHASE I & II
MUNICIPAL SEPARATE STORM SEWER SYSTEMS REGULATED
In FY 17-18, 326 municipalities were enrolled under the statewide Phase I Storm Water Permit and 293 municipalities were enrolled under the Phase II Storm Water Permit.
| Key Statistics for FY 2017-18 | |
|---|---|
| Total Municipal Separate Storm Sewer Systems | 619 |
| Phase I Medium & Large Municipalities | 326 |
| Phase II Small Municipalities | 293 |
MEASUREMENTS - Data Last Updated on: 11-21-2018 (1:22 pm)
| Region | Total Municipal Separate Storm Sewer Systems | Phase I Medium and Large Municipalities | Phase II Small Municipalities |
|---|---|---|---|
| 1 | 32 | 10 | 22 |
| 2 | 119 | 74 | 45 |
| 3 | 56 | 1 | 55 |
| 4 | 114 | 99 | 15 |
| 5 | 141 | 23 | 118 |
| 6 | 11 | 3 | 8 |
| 7 | 18 | 13 | 5 |
| 8 | 77 | 63 | 14 |
| 9 | 51 | 40 | 11 |
| TOTAL | 619 | 326 | 293 |
WHAT THE MEASURE IS SHOWING
Although there is significant variation between the Regional Water Boards, the distribution of municipal separate storm sewer systems (MS4s) enrolled in either Phase I or II General Storm Water Permits (MS4 Permits) is consistent with the size of municipalities in each region, as the regions with the largest populations also have a larger number of medium and large facilities enrolled in the Phase I MS4 Permit. Fiscal Year (FY) 2014-15 was the first year that all regions have small municipalities enrolled under the statewide general permit.
WHY THIS MEASURE IS IMPORTANT
The Municipal Storm Water Permitting Program regulates storm water discharges from municipal separate storm sewer systems (MS4s). Storm water is runoff from rain or snow melt that runs off surfaces such as rooftops, paved streets, highways or parking lots and can carry with it pollutants such as: oil, pesticides, herbicides, sediment, trash, bacteria and metals. The runoff can then drain directly into a local stream, lake or bay. Often, the runoff drains into storm drains which eventually drain untreated into a local waterbody. The MS4 Permits require the discharger to develop and implement a Storm Water Management Plan/Program with the goal of reducing the discharge of pollutants to the Maximum Extent Practicable (MEP; the performance standard specified in Section 402(p) of the Clean Water Act [CWA]). The Municipal Storm Water Permitting Program management programs specify what best management practices (BMPs) will be used to address certain program areas. The program areas include public education and outreach; illicit discharge detection and elimination; construction and post-construction; and good housekeeping for municipal operations. In general, medium and large municipalities are required to conduct chemical monitoring, though small municipalities are not required to.
TECHNICAL CONSIDERATIONS
- Data Source: CIWQS. Period July 1, 2017 to June 30, 2018.
- Unit of Measure: Number of active MS4 facilities during FY 17-18.
- Data Definitions: Permits Active as of June 30, 2017.
- References: Information on the Water Boards’ NPDES Storm Water Program
Public Reports and Data
Enforcement and Compliance Assurance Information
GLOSSARY
- Municipal Storm Water Phase I Facilities
- The Municipal Storm Water Permits regulate storm water discharges from municipal separate storm sewer systems (MS4s). Under Phase I, which began in 1990, the Regional Water Boards have issued NPDES MS4 permits to permittees serving populations greater than 100,000 people. Many of these permits are issued to a group of co-permittees encompassing an entire metropolitan area. These permits are reissued as the permits expire.
- Municipal Storm Water Phase II Facilities
- Under Phase II, the State Water Board adopted a General Permit for the Discharge of Storm Water from Small MS4s (WQ Order No. 2013-0001-DWQ) to provide permit coverage for smaller municipalities (10,000 to 100,000 people), including non-traditional small MS4s which are governmental facilities such as military bases, public campuses, prisons and hospital complexes.
