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 Big Tree Nursery consulted with AE2S to assist them with the development of a site grading/drainage plan for their proposed 3-acre commercial business site and to assist with the site stormwater permitting. Under the current Minnesota Pollution Control Agency (MPCA) National Pollutant Discharge (NPDES)/ State Disposal System (SDS) permit, owners/operators of a construction site greater than or equal to one acre are required to obtain coverage under the permit. There are many steps required to be completed before an application can be submitted including the development of a Stormwater Pollution Prevention Plan (SWPPP.) The SWPPP required in Minnesota generally consists of two parts; a plan sheet indicating the site’s general layout including structural Best Management Practices (BMP’s) to be implemented as well as a narrative explaining the site existing/proposed conditions and all BMP’s to be implemented (including structural and nonstructural). In Minnesota, permanent structural BMP’s are required to be implemented if the proposed site is to include one or more acres of new impervious surface. This requirement includes the capture and slow release of a water quality rain event equal to 1/2-inch over all new impervious surface. In addition to this requirement the City of Moorhead also requires control of larger storm events such as the 2, 10 and 100-yr events back to the sites predevelopment state.
To tackle the site's drainage requirements AE2S proposed a permanent BMP in the form of a stormwater quality/detention pond. Stormwater ponds that are to control all of the above mentioned storm events require proper design and implementation of a special outlet device consisting of a series of orifices, weirs and culverts. For AE2S stormwater experts this was no problem. A computer model was set up to accurately analyze the existing and proposed drainage conditions for the site. The model also enabled the proper analysis of the proposed outlet device to ensure that it would perform properly to meet all the regulatory rate control requirements.
To meet the requirements of the MPCA permit, AE2S also drafted an 8-page SWPPP narrative to address and explain the following:
- Existing Site Conditions
- Proposed Site Conditions
- Best Management Practices for stormwater pollution prevention during land development construction
- Best Management Practices for stormwater pollution prevention during building construction
- Significant Materials Inventory
- Best Management Practices during post construction
- SWPPP inspection and maintenance procedures
After the fast, efficient and proper completion of all the permitting/drainage requirements, Big Tree Nursery had an approximate turn around time on their city drainage permit of less than an hour. AE2S stormwater experts have the regulatory knowledge and technical skills to ensure your project will be properly designed, on-time, and most importantly on-budget.
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