HomeMy WebLinkAboutPackets - Stormwater Utillity Commission (196)Summary of Stormwater Drainage project work completed 10-25-2023
We have a 50' to 70' wide channel that feeds stormwater from Pusch Ridge
Mountain from East to West through the South side of our property.
George Lindsay, our volunteer Stormwater Engineer sug gested the
following im provements to the current main channel:
•The narrowest point on the main channel bottom has been widened
from 4.00' to 7.75' to straighten it out.
•We removed existing channel obstructions including a large tree and
several small ones plus widening the channel to straighten it followed
by grading the sides on a 2: 1 slope on both sides.
•We then provided bank stability with on 20 year weed preventive
fabric, 4" to 8" rip rap sized to handle stormwater velocities using
lsbash equation, plus used mostly 12" rip rap embedded about 3"
at the bottom edge of embankment.
•We also added 24 LF of Gabions 30" high that one of our church
volunteers welded together and we placed on the South side where
most of the erosion had occurred and we filled with smaller stones.
•Using the Open Channel Flow Calculator, with trapezoidal flume, we
have slightly more than doubled the channel capacity from 249.68 cu.
ft/sec. to 541.01 Cu. ft./ sec. flow and velocity modestly increased by
10% from 11.89 to 13.12 ft.I sec., resulting in minimal erosion of the
stream bed.
•We also added a row of CMU blocks with stones concreted on top
an<:1 backfilled at the upper South side of the central portion of the
channel to minimize the chances of stormwater eroding the South
side of our channel near our lower campus which recently occurred.
•It was noted that if sand builds up at the concrete drainage structure
to the West under Oracle Road another 2 feet tha t we should contact
the highway department of the need to do maintenance related to
removing sand build up.
We then continued excavation and improvements On the East side of our
secondary access road from Calle Concordia Street
•We dug a reces s in the ground where we placed a row of large
boulders, 2,000 to 3,000 lb.+/ each. A second row of medium sized
stones were embedded16' apart and were concreted in place. Both
rows have 3' gaps every 10 feet, or so. Porous sand bags immersed
in water were placed in the gaps to help catch sand above the access
road during monsoon rains to slow stor mwater, but allow water to
flow through. We anticipate needing to remove sand build up on an
annual or bi-annual basis, as needed.
•A channel was dug 1 O' wide x 55' long perpendicular to the main
channel on the East side of the row of largest stones, followed by
about 22' on a 45-degree angle 4' wide and then 33'i •
widened it from 4' to 8' wide. Embankments 2' to 3' high on both sides
are covered with rip rap from North to South to the utility easement
line. I have added precast concrete curbs and placed them on
diagonal angle to the channel and toed in to the low side of the
channel.
•A 20' channel with rip rap 12" (+) long needs to be installed by Oro
Valley's Stormwater crew for energy dissipaters per "lsbash equation
in Manning Formula" for uniform pipe flow at given slope and depth"
to handle stormwater velocities from the 30" culvert to the utility
easement line. I have gathered over 120 of these stones and placed
adjacent to area East of secondary entrance road for use:
•There is a second culvert further East under Galle Concordia and
stormwater from the housing developments to the South and
Southeast flows into and through the South side of our property.
Since completing the above work, I have been observing the main channel
work and the erosion from mild rain showers and done the following
improvements:
•We added two signs at the upper side of the access road warning
'Danger, Flood Area, Park at own risk' and two signs, on each side of
side channel marking "Fiber Optic Buried Cable" location.
•Five 5' long x 5-1/2" diameter stormwater sand filter socks were
purchased for use at doorways of the adjacent storage room in case
of "significant" high stormwater flowing e.g., 100-year flood.
•The main recent July -August erosion was on the south side of the
main channel work. We dug out sand and buried rip rap after the
concrete beam 12" wide x 20'. We also added smaller rip rap stones
in grout over an 1 0' long x 1 '-6" wide x 18" deep layer of rip rap where
the East to West erosion occurred and grouted with medium size rip
rap an extra 1 '-0" on both sides along South rip rap embankment.
•We decided to add a grout curb at both the South and North end of
the rip rap on 2:1 embankment on main channel so the rip rap will be
contained and not wash down stream in a deep stormwater.
•I decided also to install rip rap on a number of areas on the south
side of the channel where erosion had occurred.
'
)
Summary of Stormwater Drainage project work completed 10-25-2023
We have a 50' to 70' wide channel that feeds stormwater from Pusch Ridge
Mountain from East to West through the South side of our property.
George Lindsay, our volunteer Stormwater Engineer suggested the
following improvements to the current main channel:
•The narrowest point on the main channel bo ttom has been widened
from 4.00' to 7.75' to straighten it out.
•We removed existing channel obstructions including a large tree and
several small ones plus widening the channel to strai ghten it followed
by grading the sides on a 2:1 slope on both sides.
•We then provided bank stability with on 20 year weed preventive
fabric, 4" to 8" rip rap sized to handle sto rmwater velocities using
lsbash equation, plus used mostly 12" rip rap embedded about 3"
at the bottom edge of embankment.
•We also added 24 LF of Gabions 30" high that one of our church
volunteers welded together and we placed on the South side where
most of the erosion had occurred and we filled with smaller stones.
•Using the Open Channel Flow Calculator, with trapezoidal flume, we
have slightly more than doubled the channel capacity from 249.68 cu.
ft./sec. to 541.01 Cu. ft./ sec. flow and velocity modestly increased by
10% from 11.89 to 13.12 ft./ sec., resulting in minimal erosion of the
stream bed.
•We also added a row of CMU blocks with stones concreted on top
and backfilled at the upper South side of the central portion of the
channel to minimize the chances of stormwater eroding the South
side of our channel near our lower campus which recently occurred.
•It was noted thatif sand builds up at the concrete drainage structure
to the West under Oracle Road another 2 feet that we should contact
the highway department of the need to do maintenance related to
removing sand build up.
We then continued excavation and improvements On the East side of our
secondary access road from Calle Concordia Street.
•We dug a recess in the ground where we placed a row of large
boulders, 2,000 to 3,000 lb.+/ each. A second row of medium sized
stones were embedded16' apart and were concreted in place. Both
rows have 3' gaps every 10 feet, or so. Porous sand bags immersed
in water were placed in the gaps to help catch sand above the access
road during monsoon rains to slow stor mwater, but allow water to
flow through. We anticipate needing to remove sand build up on an
annual or bi-annual basis, as needed.
•A channel was dug 1 O' wide x 55' long perpendicular to the main
channel on the East side of the row of larg est stones, followed by
about 22' on a 45-degree angle 4' wide and then 33'
widened it from 4' to 8' wide. Emban kments 2' to 3' high on both sides
are covered with rip rap from North to South to the utility easement
line. I have added precast concrete curbs and placed them on
diagonal angle to the channel and toed in to the low side of the
channel.•A20' channel with rip rap 12" (+) long needs to be installed by Oro
Valley's Stormwater crew for energy dissipators per "lsbash equation
in Manning Formula" for uniform pipe flow at given slope and depth"
to handle stormwater velocities from the 30" culvert to the utility
easeme nt line. I have gathered over 120 of these stones and placed
adjacent to area East of secondary entrance road for use.•There is a second culver t further East under Calle Concordia and
stormwater from the housing develop ments to the South and
Southeast flows into and through the South side of our property.
Since completing the above work, I have been obser vi ng the main channel
wor k and the erosion from mild rain showers and done the following
improvements:
•We added two si gns at the upper side of the access road warning
'Danger, Flood Area, Park at own risk' and two signs, on each side of
side channel marking "Fiber Optic Buried Cable" location.
•Five 5' long x 5-1/2" diameter stormwater sand filter socks were
purchased for use at doorways of the adjacent storage room in case
of "significant" high stormwater flowin g e.g., 100-year flood.
•The main re cent July -August erosion was on the south side of the
main channel work. We dug out sand and buried rip rap after the
concr�te beam 12" wide x20'. We also added smaller rip rap stones
in 'grout over an 10' long x 1'-6" wide x 18" deep layer of rip rap where
the East to West erosion occurred and grouted with medium size rip
rap an extra 1 '-0" on both sides along South rip rap emba nkment.•We decided to add a grout curb at both the South and North end of
the rip rap on �:1 embankment on main channel so the rip rap will be
contained and not wash dow n stream in a deep stormwater.•I decided also to install rip rap on a number of areas on the south
side of the channel where erosion had occurred.
·,
)