Nlake WE P6/Re-CS 870319 (3)gradient at the culvert entrance, in excess of 13% and thus the
erosion will continue to mitigate in an upstream direction until
a state of equilibrium is reached regarding the entrance gradient
(ie., more gentle, non-erosive entrance grade is obtained).
The second area of concern observed was the culvert crossing
regarding public safety. The unsafe condition that exists is a
sharp dropoff. This is due to the headwall being approximately 3
feet below the top of the sidewalk.
PROPOSED SOLUTIONS
A) Ditch: The existing culvert and channel need to be cleaned
out and restored to its original design condition and sodded or
grassed for immediate erosion control.
Thereafter, normal periodic culvert maintenance that is n~>rmally
expected can be performed as needed.
Attached is exhibit C which shows sections A-A and B-B, the
downstream section and upstream section, respectively, as
originally designed by Don A. Tipton, Inc., Consulting Engineers.
Also attached are exhibits D & E, reflecting cross section and
profile details, respectively, which both show the drainage
easement that has been filled and encroached upon.
B) Headwall: In regards to the concern for public safety at the
culvert crossing, we recommend that a chain link fence,
decorative railing or wrought iron handrail system, minimum
height of 4'-0" (unless building code requires otherwise), should
be installed around the culvert headwall and wingwalls. The
minimum height should be measured from the 'top of the existing
sidewalk adjacent to the headwall. This will keep individuals
from inadvertantly falling into the channel. In addition, to
protect against erosion of the steep slope that exists between
the sidewalk and headwall, slope protection should be installed.
Available options would be placing sod and pinning it to the
subgrade (most economical), concrete rip-rap, brick pavers used
as rip-rap, raise height of headwall (most expensive). Whatever
above options are selected should be installed on both sides of
the street.
The above comments adequately address the pedestrian and
bicyclist safety needs. Regarding the motor vehicular traffic, a
guardrail could be installed adjacent to the street curb,
however, it would be discretionary for the city since a 12 foot
parkway exists between the curb and the headwall and the street
also has a 6" curb. These existing conditions probably provide
sufficient protection, however, there are always extremes that
can occur.
We believe that the above recommendations will adequately satisfy
the concerns of all parties involved.
Exhibit C
Exhibit D
N.