HomeMy WebLinkAbout190827_Barr_Potential Residential Stormwater Storage SummaryA rainwater garden
typically stores first
~1 inch of runoff
Image source: Barr Engineering
Example of underground storage
20 feet wide (4 inches of runoff)
10 feet wide (2 inches of runoff)
5 feet wide (1 inch of runoff)
All assume that the stormwater storage
feature spans the entire parcel (~60’ long per
parcel), and that the depth is about 3 feet of
storage below grade.
Residential Stormwater Storage Examples
15 feet wide (3 inches of runoff)
Can fit roughly two in the street width (or in
the right of way).
Again, this assumes using the entire length of
the block, and being able to store 3 feet.
Note: Interference with other utilities may
make this difficult.
Storm Event 24-hr Precip.5-year 3.59 in.
10-year 4.29 in.
25-year 5.41 in.
50-year 6.39 in.
100-year 7.49 in.
Storm Event 24-hr Precip.5-year 3.59 in.
10-year 4.29 in.
25-year 5.41 in.
50-year 6.39 in.
100-year 7.49 in.
Storm Event 24-hr Precip.5-year 3.59 in.
10-year 4.29 in.
25-year 5.41 in.
50-year 6.39 in.
100-year 7.49 in.
$0
$15,000
$30,000
$45,000
$60,000
$75,000
$90,000
0
5
10
15
20
25
30
0 1 2 3 4 5 6 Approximate Cost Per Parcel (+/- 33%)Width of Underground Storage Unit (feet)Inches of Runoff Stored
- Cost per cubic foot of underground storage = $10-$20
- For 1 inch of runoff, on one 0.25 acre parcel, storage volume is 900 ft3. This equates to about $15,000 +/- $5,000 per parcel per inch of runoff stored.
In the window to the left, there are 4 blocks, covering just over
50 acres.
This also means there are about 180 parcels in these 4 blocks.
To capture 2 inches of runoff from every parcel would cost
about $5,400,000
2 inches of runoff is what is generated typically (on the whole)
in this area from the 10 year storm (4.3 inches of rainfall).
This would remove nearly 400,000 cubic feet of water from the
system (just over 8.5 ac-ft).
There are about 570 residential parcels in the
Morningside neighborhood watershed in
Edina.
Inches of
Runoff Stored
Cost for All Parcels to
Store the Runoff
Flood Level Reduction Benefit (in feet) for Weber Pond
Subwatershed(MS_40)
5-yr Storm
(3.59" of
precip)
10-yr Storm
(4.29" of
precip)
50-yr Storm
(6.39" of
precip)
100-yr Storm
(7.49" of
precip)
1 inch $ 8,550,000 0.1 <0.1 <0.1 0
2 inches $ 17,100,000 0.6 0.3 0.5 0.3
3 inches $ 25,650,000 0.7 0.9 0.6 0.5
~$25M
~$8.5M
$~17M