Determining the 10-year WSEL (water surface elevation) of a micro-bio with a weir

[ewizz__]

Hello, I am designing a micro-bioretention with a weir. How can I determine the 10-year water surface elevation of the micro-bio in order to install the weir at the correct elevation?

 

[bimr]

Please post a diagram.

Micro-Bioretention facilities shall not be located where the water table is within 2 feet of the bottom of the micro-bioretention
facility. If the 2 ft. clearance requirement cannot be met, an alternative stormwater practice must be proposed. An impervious liner may be used in some cases.

Bioretention areas are vegetated, shallow surface depressions that use the interaction of plants, soil, and microorganisms to store, treat, and reduce runoff volume, and to reduce the flow rate of stormwater runoff. Bioretention areas are generally
flat and include engineered or modified soils that allow drainage of stormwater through soils. During storms, runoff temporarily ponds 6 to 12 inches above the mulch layer and then rapidly filters through the bed.

Site Constraints:
• Depth: 2 feet to water table / bedrock
• Steep slopes: <20% or terraced to slow flow.
• Media permeability: ≤ 0.5in/h or needs underdrain