Hello, and welcome to our new stormwater blog, “From Policy to Action.” With this blog, my colleagues and I at Tetra Tech will discuss with you some interesting and cutting-edge topics related to stormwater policy and implementation. We’ll cover topics related to permitting, stormwater management plan development, BMP design and selection, total maximum daily loads (TMDLs) as they relate to stormwater, and many other related topics. We’ll post our thoughts on these topics and we look forward to engaging in a lively debate with you!
Our first post is on National Pollutant Discharge Elimination System (NPDES) permits for municipal separate storm sewer systems (MS4s), generally municipalities. These MS4 permits, first issued to large and medium MS4s in the early 1990s, are now entering their third or even fourth permit terms. Some MS4 permits have been written to include the specific BMPs and actions that the permittee must take into the MS4 permit itself, while other MS4 permits include broader requirements and leave the details to the MS4s written stormwater management plan. Leaving the details in the stormwater management plan gives the MS4 more flexibility and places a greater burden on the state to review the stormwater management plan for adequacy.
An example of a specific MS4 permit is the recently issued draft MS4 permit for Ventura County, CA. This 122-page permit (excluding attachments) details the specific activities the MS4s must complete for each program area. For example, in the educational program area, the permittees are to develop a corporate outreach program to educate managers on stormwater targeting a minimum of “two home improvement center franchisers and six restaurant franchisers.” The illicit discharge program area requires the development of a GIS map showing the location and length of underground pipes 18 inches in diameter or greater within five years.
These specific MS4 permits are helpful in that the expectations are clearly stated in the permit. Municipalities do not need to “guess” at what the state intended. Specific permits also allow an MS4 to more easily budget resources because the expectations are more defined.
There are drawbacks to a very specific MS4 permit. When a permit specifies a certain BMP, it can be difficult for the MS4 to change that BMP if through the iterative approach the MS4 finds that BMP is not effective. Also, a single MS4 permit issued to a number of copermittees may set a bar that is not appropriate for all copermittees. For example, I did MS4 audits in a city with 20 copermittees under one MS4 permit. The MS4 permit stated that a high-priority construction site was one that disturbed at least 50 acres. Although this threshold was appropriate for a few of the larger MS4s, many of the smaller MS4s did not have construction sites over 5 acres, let alone 50 acres. For these smaller MS4s, most choose to strictly follow the permit language, meaning that they did not have any high-priority construction projects (with the increased inspection frequency that goes with a high-priority site). These small MS4s could have easily redefined a high-priority site to better fit their situation, but chose not to because the MS4 permit was so specific.
What are your thoughts about how specific MS4 permits should be? Should the requirements be placed in the MS4 permit, or should they be in the MS4’s written stormwater management plan? Please send your comments and thoughts.