Public Works, Flood Control Engineering

Guidelines for Subdivisions and Development Companies

1. Developers of subdivisions and other developments are sometimes required to provide a signature block for Salt Lake County Flood Control on the mylar plat(s). All plats should be reviewed by the County Recorder's Plat Division before obtaining any signatures. If your plat drawings are not correctly formatted for recording, you will be required to correct the plat and get all those signatures again!
   1. If your subdivision or development is located within a City, and your property line or ANY work is NOT within twenty feet of the top of the bank of a County facility, you must obtain a letter from the appropriate City Engineer stating that he or she has reviewed your plans and found them to conform to the City's Master Plan.
   2. This letter must also state which County Facility (if any) is impacted by the Storm Water Discharge.
   3. This letter must accompany the Mylar Plat when you request the County's signature.
2. If your subdivision or development DOES affect, or discharge to, a County facility, you must first obtain an approved Flood Control Permit from Salt Lake County. Your plat (including the city engineer's letter as above) will be signed after the permit has been approved.
3. Discharging storm waters directly to any County facility is no longer permitted. Most flood control facilities are at capacity. Always plan to detain storm waters to either a City's allowable discharge rate or the pre-development (historical or natural) discharge rate, which ever is less.
4. You must provide three sets of hydrology calculations.
   1. Pre-development and post-development runoff calculations for your project using a 10-year storm event or the municipal jurisdiction design storm.
   2. You must also provide calculations and cross sections which describe detention or retention pond sizing AND show FEMA data which identifies the 100 year flood elevation for any natural stream.
   3. (Note: FEMA does not provide flood data for man-made facilities.)
5. New subdivisions will be required to provide a 20 foot (6.1 meters) setback and easement, as measured from the top of the bank, for flood control maintenance purposes. Smaller easements can be permitted given sufficient justification.
6. Culverts for new road crossings of open channels must pass the 100-year flood flows.
7. Structural details and plans for bridges must be stamped by a licensed Structural Engineer.
8. All other plans and calculations must be stamped by a licensed Professional Engineer or Land Surveyor.
9. Many cities will require new developments to install fences around streams and canals at the property lines. Salt Lake County must be able to drive heavy equipment along the banks to perform maintenance and does not allow fencing within twenty feet of the top of bank.