Blog post by stormwater design expert Hannah Lancaster.
The permitting process for stormwater plans can be challenging. Reports are city- and project-specific with each county providing its own template with different requirements based on the local watershed. To get through it as efficiently as possible, CDR has become familiar with many California jurisdictions and their expectations for design, exhibits, and clear communication.
Introduction and General Summary
Typically, the permitting report begins with a title sheet and body of the report which includes a general summary of what the project is and what is going to be implemented. There is a checklist that explains why the report is required, ownership information, and a list of the pollutants based on the project being proposed. In the case of commercial development with a parking lot and perimeter landscaping, commonly found pollutants include nutrients, sediment, metals, trash and debris.
In theory, the next section of the permit application would allow for a claim that there isn’t room on the property to treat the water, but this exception is rarely allowed. In most cases, it’s best to select “not eligible” and continue on.
The Lifespan of a Water Droplet
The city will want to know exactly where a drop of water that falls onto the project site will travel in its “lifespan.” For example, the water droplet will sheetflow to an onsite inlet, be pre-treated, retained on-site, and if the system overflows, the water will discharge to the public storm system. This section has to be exceptionally specific and requires some background research to say, for example, it goes to this storm drain first, goes to that storm drain next, and then eventually it gets dumped out to this river and into the ocean.
The following section is on the selection of a treatment option, which clarifies what policies are being put in place to make sure pollutants are limited from the start. Restrictions include things like prohibiting the use of fertilizer where the water goes right to the storm drain system to keep fertilizer from going into the ocean. Thinking ahead and designing resolutions for as many potential issues as possible makes the water cleaner in the end and expedites the permitting process.
Site Erosion and Structural Support
Next, there is a checklist of what pollutant source control structures and strategies are being implemented. For example, depressing landscape planters a couple of inches below adjacent parking lot areas reduces the risk of stormwater runoff overflowing back onto the asphalt where it can pick up additional oil and contaminants. Another tactic could be protecting some of the side slopes in the landscaping or providing a separate car wash area with an inlet that does not convey water to the storm drain system. This section proves that there are applications being put in place to help prevent the production of additional pollutants and protect the project site’s water quality.
Then the city requires an explanation of what is being done to treat or filter water after the preliminary steps have been taken. If the intent is to build a parking area over a dirt lot, there will be a lot of stormwater runoff volume to mitigate since the water cannot percolate into the ground as it used to do. In that particular case, one solution could be to install an underground tank with a small hole in it to create a controlled outlet that won’t flood whatever system it flows into.
There will be recommended maintenance procedures and intervals for all treatment or detention systems, but the detail included in permitting reports can occasionally be overlooked or excessive, requiring more than what’s necessary. CDR takes a realistic approach about what the owner is going to be responsible for when writing the reports, which protects the client. Property owners are responsible for completing whatever actions are written in the application and can be fined by the city if they don’t have detailed reports that prove the required maintenance efforts have been followed.
Stormwater Site Plan
The stormwater site plan exhibit visually illustrates what is being proposed in the stormwater report for the project site. Each drainage management area, generally delineated with a thick, blue line, represents the area of stormwater runoff draining to an onsite treatment system. Storm drain lines flow directions, preventative erosion control measures, and the proposed treatment or underground storage systems with overflow locations are shown as well. Once approved, this report is public information and is usually found on the city’s website.
CDR has an excellent history of achieving timely permit approvals, understanding that if the overall plan is communicated well on the exhibit, the city will generally trust what is written in the report, expediting the process. To learn more about CDR’s cost effective design of stormwater management systems, read this article.
If you have a land development project, please contact us to see how we can help you save time and money with our civil engineering services.