Stormwater management has become a standard aspect to development projects in California. It is now a basic requirement to produce a stormwater drainage plan as part of a building permit application even for small developments or improvements. In order to gain a building permit, an applicant must develop a plan showing which stormwater protection best management practices will be implemented during the construction of the project to insure that stormwater will be protected from contaminates that may be introduced to stormwater from construction activities. In addition, a building permit applicant must prepare a drainage plan showing the stormwater drainage paths that will exist at the completion of the improvement project. As part of this post-construction stormwater management plan, an applicant must show all areas that will be considered impervious before and after an improvement project is complete. The amount of reporting and design detail required will depend on how large of an area will be disturbed during construction activities and how much area will be considered impervious upon project completion.
If an area over one acre is proposed to be disturbed during a construction project then a special stormwater management permit from the State of California must be obtained. This permit will require the production of a document called a Stormwater Pollution Prevention Plan (SWPPP) that must be completed by a certified consultant such as a Civil Engineer.
The amount of impervious surface that is being proposed by an improvement project will determine which types of stormwater best management practices will be required to be implemented for the project. Possible requirements will include capturing stormwater to promote onsite infiltration through biofiltration swales or rain gardens. Preliminary design for development projects should include areas where stormwater best management practices will be implemented.
Construction and post-construction stormwater management design and implementation is a significant expense for construction projects and should be considered very early in the design process.