Stormwater Manual - Pima County Flood Control District

11.2.2 Non-Structural Practices
This section describes the planning and implementation of the required non-structural BMPs
to minimize erosion and off-site sedimentation.
These BMPs include:
floodplain avoidance
stream buffer zones
reduced exposure time
limits on maximum disturbed area
embankment slope minimization
Floodplain Avoidance
No construction or grading activities are permitted in the post-development floodplains, as
defined in Chapter 1 of this manual, except for road and utility crossings and permanent
stormwater management facilities. Therefore, only erosion and sediment control practices
related to allowable construction activities shall be permitted in the post-development
floodplain. Temporary sediment control in a permanent pond shall be allowed in the postdevelopment
floodplain but not in a stream.
Vegetative Buffer Strips
Buffer strips are required adjacent to all streams and wetlands in Fayette County. The buffer
strip width shall be 25 feet from the top of each bank and from the edge of a wetland. No
grading or land clearing is allowed within the buffer zone, and native vegetation must be
preserved.
Reduced Exposure Time
All on-site measures required by the Erosion and Sediment Control Plan shall be made
functional before other land disturbance takes place. Permanent or temporary soil
stabilization, as described under structural practices, shall be applied to disturbed or
constructed areas within 14 days after final grade is reached. Soil stabilization shall also be
applied to all disturbed areas not at final grade, including soil stockpiles, dams, dikes, and
diversions, which have been inactive for 14 days.
Limits on Maximum Disturbed Area
The maximum area that may be disturbed at any time during construction, without soil
stabilization, is 25 acres. For sites over 25 acres in size, additional land can be disturbed only
when an equal amount of land is stabilized. A construction site shall not be broken into
individual permits to avoid this requirement.
Embankment Slope Minimization
Steep embankment slopes present increased opportunities for erosion and sediment
production due to high runoff velocities. To minimize adverse effects of steep embankment
slopes, constructed fill slopes and cut slopes shall not be steeper than 3H:1V. For slopes of
4H:1V or steeper with slope lengths of greater than 100 feet, temporary diversion ditches shall
be constructed at the top of the slope and every 100 feet horizontally down the slope.
STORMWATER MANUAL 11-5 August 29, 2011
LEXINGTON-FAYETTE CO., KY.