AppendixA Western Shorewood Stormwater Management Plan: Preliminary Alternatives ReviewWestern Shorewood
Stormwater Management Plan:
Preliminary Alternatives Review
Jen Koehler, PE & Bob Obermeyer, PE
11/7/2019
■ ■ ■ ■ i!!
1
Scope
• Survey of key areas
• Review and revisions of existing XP -SWMM model
• Develop existing conditions P8 model
• Reevaluation of recommended alternatives
— Looking at alternatives feasibility
— Considering feedback from MCWD
• Further evaluation and development of preferred concept
• Did not include efforts that would be complete during final
design /permitting: wetland delineation, tree survey, design survey
2
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Background
■ Numerous areas with drainage issues in Western
Shorewood
— Area 1: Shorewood Oaks*
— Area 2: Strawberry Lane*
— Area 3: Freeman Park*
—Area 4: Beverly Drive
— Area 5: Grant Lorenz Channel*
— Area 6: Sleepy Hollow /Noble Road
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Existing
Conditions -
100 -year inundation
Area 6:
Sleepy Hollow/
A
938.1
M2 971.0
Noble Road � .
B
BEV
941.5
953.3
N 969.1
970.6
t
{�'
ti ��Q _
Area 5:
Grant Lorenz
c
938.0
P 975.0
S �• -�..
Channel
CAl
949.0
Qt 975.1
1
'
U
948.1
41'2 975.1
M'
E
952.0
Q2 970.9
_
Area 2:•
F
953.7
Q3 974.5
Strawberry Lane
H
953.8
Q4 974.5
R
956.6
969A
956.6
S 976A
r.
1
K
956.6
969.5
U 932.9
V 969.5
Area 3:
Freeman Park
0
Mt
970.5
971.9
Area 4:
WET 932.4
Drive /Cajed Lane
Shorewood Oaks -
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Existing Conditions - Wetlands (NWI)
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Area 3: Freeman Park
Issues
• Outlet structure flagged as critical during Hennepin
County Regional Railroad Authority Stormwater
Infrastructure Qualitative Failure Risk Assessment (Feb
2018)
— 48" Pipe with joint separation
• Flood elevation surcharges Shorewood Oaks system
and has caused flooding of sump systems /private
residences
• Debris and plugging ongoing maintenance issues
• Downstream erosion issues along Grant Lorenz
channel
Standing water in ball fields
Groundwater high in area (water table within a few
feet of ground surface)
• Forested area of the park is mapped as wetland
— NWI: Freshwater Forest /Shrub wetland
— MCWD: Manage 1 Wetland
11
SARK
Area 3: Freeman Park
Issues
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11/7/2019
Previous
Recommendation
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loll
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13
Area 3: Freeman Park
Potential Solutions
• Replace outlet structure at
existing /lower elevation (959.5 ft
MSL/957.5 ft MSL)
• Replace outlet structure and expand
storage at Freeman Park
— Peak discharges are relatively low due to
18" outlet but can lower peak discharge
and lower flood elevations in Freeman
Park
• Replace outlet structure and develop
storage for stormwater reuse at
Freeman Park
• Consider infiltration /filtration at
Freeman Park — not evaluated due to
high groundwater conditions & poorly
draining soils (C /D)
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Area 3: Freeman Park
Potential Solutions
■ FP1: Replace outlet structure at
existing elevation (959.5 ft MSL)
—18 "RCP
■ Replace outlet structure at lower
elevation (957.5 ft MSL)
— FP2: 18" RCP
— FP3: Extended Detention : 6" orf
w/ weir
15
Area 3: Freeman Park
Potential Solutions
■ FP4: Replace outlet structure
(18" RCP @ 959.5) and
expanded detention storage
(additional12.9 ac -ft)
■ FP5: Replace outlet structure
(18" RCP @ 957.5) and
expanded detention storage
(additional 17.9 ac -ft)
16
-- -- - - ----- 7
MULTI -Ehg MTLET $TRUMRE W EXWPLQ
NIS
Source: MN Stormwater Manual
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Area 3: Freeman Park
Potential Solutions
■ FP6: Replace outlet
structure and utilize
existing storage for
stormwater reuse at
Freeman Park ( -1.0 acre -ft)
■ —6 acres irrigated @
1 " /week May- September
■ Assumes filtration and UV
disinfection treatment prior
to irrigation
17
storage and
pumping for
irrigation /reuse
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Area 3: Freeman Park
Potential Solutions
1W
90
so Assume 1.0 ac -ft
]0
E
ov 60
d 50
40
3 30
20
10
0
0 2 3 4 5 6
Storage Volume (acre-ft)
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�Stormwater Reused ( %) Irrigation Demand Met( %)
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Area 3: Freeman Park
Impacts & Costs
Existing Conditions - 969.5
0/0
FP1: Replace Outlet to 959.5
969.5
0/0
N/A
FP2: Lower Outlet to 957.5'
969.4
0/0
_I N/A
FP3: Extended Detention at
970.5
0/0
N/A
Lower Elevation 957.5
FP4: Outlet at 959.5 with
968.0
0/0
N/A
Expanded Storage
FPS: Outlet at 957.5 with
967.1
0/0
N/A
Expanded Storage
FP6: Outlet at 959.5 &
0/0
3.1
Stormwater Reuse
*Costs include Engineering, Design, and Permitting (25 %)
Based on limited design, uncertainty in cost -30% to +50%
19
Area 5: Grant Lorenz Channel
Issues
•& r.p:'S: �'f -. - _ - _ -.tom
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$71,000
$71,000
$71,000
$1,430,000
$1,830,000
$680,000
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Area 5: Grant Lorenz Channel
Issues
• High flows /velocities
resulting in erosion and
sediment transport
• Overtopping driveways and
destroying culverts
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Area 5: Grant Lorenz Channe
Issues
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Area 5: Grant Lorenz Channe
Issues
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Area 5: Grant Lorenz Channe
Issues
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Area 5: Grant Lorenz Channel
Issues
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• Bankfull Depth /Connection to
Floodplain
:,, T.H
• Flowp ""
a�dr °d
Mmm,n, RICA
•m�wiiq
• Velocity °�° 2
• Shear
Shear Stress
Calculated
Erosion Intensity
Stabilization
(Ibs /sf)
Score
Practice
5 2.5
Low
Biological
Biological or
2.6 -5
Medium
Bioengineered
Biological,
Bioengineered, or
> 5
High
Structural
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MA
Channel
Section
Bankfull Depth
(ft)
Slope (ft /ft)
Parameter
1- r
2- r
10- r
100- r
G
1.7
0.0093
Flow (cfs)
24
31
77
207
Velocity (ft /s)
3.9
3.9
3.9
3.8
Max Depth (ft)
2.3
3.0
4.2
6.5
Shear (Ibs /ft3)
1.3
1.7
2.4
3.7
Flow (cfs)
Downstream of Grant Lorenz Velocity (ft /s)
Road, the Channel is incised and Max Depth (ft)
disconnected from the floodplain Shear (Ibs /ft3)
Grant a
31
41
88
237
1.8
1.9
1.9
2.0
2.0
2.3
3.9
7.1
0.6
0.7
1.2
2.2
2.9
8.3
10.1
Shear (Ibs /ft3)
1 1.7
2.1
5.4
0.0114
Flow (cfs)
33
44
96
252
Velocity (ft /s)
4.6
5.0
5.4
5.4
Max Depth (ft)
2.0
2.4
5.8
10.9
Shear (Ibs /ft3)
1.4
1.7
4.1
7.7
4.7
D
1 4.4
1 0.012
Flow (cfs)
34
46
96
257
Velocity (ft /s)
4.7
4.8
4.9
4.9
Max Depth (ft)
2.2
2.9
8.3
10.1
Shear (Ibs /ft3)
1.7
2.1
6.2
7.5
4.1
rbor Creek Lane
2.0
- -
5.0
0.0009
Flow (cfs)
34
46
96
272
Velocity (ft /s)
2.4
2.6
3.4
5.4
Max Depth (ft)
2.0
2.3
3.2
4.7
Shear (Ibs /ft3)
0.1
0.1
0.2
0.3
118
Flow (cfs)
35
47
99
275
Velocity (ft /s)
4.1
4.2
5.3
6.6
Max Depth (ft)
2.8
3.4
3.7
4.1
Shear I ft
2.0
2.5
2.7
3.0 1
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Channel
Section
Bankfull Depth
(ft)
Slope (ft /ft)
Parameter
1- r
2- r
10- r
100- r
G
0.0093
Flow (cfs)
24
31
77
207
Velocity (ft /s)
3.9
3.9
3.9
3.8
Max Depth (ft)
2.3
3.0
4.2
6.5
Shear (Ibs /ft3)
1.3
1.7
2.4
3.7
Flow (cfs) 31 41 88 237
Velocity (h (ft) 1.8 1.9 1.9 2.0
Velocities exceed 3 -4 fps in several
Max Depth (ft) 2.0 2.3 3.9 7.1
sections of the channel, likely/ Shear (Ibs /ft3) 0.6 0.7 1.2 2.2
rant L, contributing to erosion without
well established vegetation or Flow (cfs) 33 44 96 252
other stabilization Velocity (ft /s) 4.6 5.0 5.4 5.4
Max Depth (ft) 2.0 2.4 5.8 10.9
E 5.4 0.0114 Shear (Ibs /ft3) 1.4 1.7 4.1 7.7
D
4.4
0.012
Flow (cfs)
34
46
96
257
Velocity (ft /s)
4.7
4.8
4.9
4.9
Max Depth (ft)
2.2
2.9
8.3
10.1
Shear (Ibs /ft3)
1 1.7
2.1
6.2
1 7.5
rbor Creek Lane
5.0
0.0009
Flow (cfs)
34
46
96
272
Velocity (ft /s)
2.4
2.6
3.4
5.4
Max Depth (ft)
2.0
2.3
3.2
4.7
Shear (Ibs /ft3)
0.1
0.1
0.2
0.3
3.8
1 0.0118
Flow (cfs)
35
47
99
275
Velocity (ft /s)
1 4.1
1 4.2
1 5.3
1 6.6
Max Depth (ft)
2.8
3.4
3.7
4.1
Shear Ibs ft3
2.0
- -
2.7
3.0
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Wel
Previous
Channel
Section
Bankfull Depth
(ft)
Slope (ft /ft)
Parameter
1- r
2- r
10- r
100- r
G
1.7
0.0093
Flow (cfs)
24
31
77
207
Velocity (ft /s)
3.9
3.9
3.9
3.8
Max Depth (ft)
2.3
3.0
4.2
6.5
Shear (Ibs /ft3)
1.3
1.7
2.4
3.7
4�
Flow (cfs) 31 41 88 237
" !loci (ft /s) 1.8 1.9 1.9 2.0
Shear Stress typically exceeds Ix Depth (ft) 2.0 2.3 3.9 7.1
F vegetation thresholds during ear (Ibs /ft3) 0.6 0.7 1.2 2.2
Grant Loren larger events
Flow (cfs) 33 44 96 252
Velocity (ft /s) 4.6 5.0 5.4 5.4
Max Depth (ft) 2.0 2.4 5.8 10.9
5.4 0.0114 Shear (Ibs /ft3) 1.4 1.7 4.1 7.7
D
4.4
0.012
Flow (cfs)
34
46
96
257
Velocity (ft /s)
4.7
4.8
4.9
4.9
Max Depth (ft)
2.2
2.9
8.3
10.1
Shear (Ibs /ft3)
1.7
2.1
6.2
7.5
rbor Creek Lane
5.0
0.0009
Flow (cfs)
34
46
96
272
Velocity (ft /s)
2.4
2.6
3.4
5.4
Max Depth (ft)
2.0
2.3
3.2
4.7
Shear (Ibs /ft3)
0.1
0.1
0.2
0.3
3.8
0.0118
Flow (cfs)
35
47
99
275
Velocity (ft /s)
4.1
4.2
5.3
6.6
Max Depth (ft)
2.8
3.4
3.7
4.1
Shear (Ibs /ft3)
2.0
2.5
2.7
3.0
Wel
Previous
Recommendation
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Area 5: Grant Lorenz Channel
Potential Solutions
• GL1: Smithtown Pond (Maximized) with extended detention outlet & stabilization along Grant
Lorenz Channel
— Option could potentially incorporate iron - enhanced sand filtration (IESF) bench
— Biostabilization
• GL2: Smithtown Pond (Moderate) with modified outlet & Stabilization along Grant Lorenz Channel
— Option cannot incorporate IESF bench
— Hard Armoring /some biostablization
• Rate Control at Freeman Park — limited impact due to existing 18" RCP and issues with surcharging
Shorewood Oaks system
• Bypass of flows from Smithtown via storm sewer down Grant Lorenz — limited right of way, conflict
with existing utilities, conflict with Grant Lorenz culvert crossing
31
Area 5: Grant Lorenz Channel
Potential Solutions
• GL1: Smithtown Pond (Maximized) with
extended detention outlet
— 15" orifice @ 952.0 ft MSL
— 7' Weir @ 953.5 ft MSL
— Rate /Flood Control and WQ Treatment
• 4.4 acre -ft of additional WQ treatment volume
• 17.9 acre -ft of Additional Flood Control Volume
• Stabilization along Channel
• Small ditch area at Smithtown mapped as
wetland
— MCWD: No Classification
— NWI: Freshwater Emergent wetland
32
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33
Area 5: Grant Lorenz Channel
Potential Solutions
• Reconfiguration of culvert crossing on Grant
Lorenz Road
• Stabilization along channel
— Targeted rip rap /hard armor
— Biostabilization measures
— Grading side slopes/Widening of channel?
• Sections of Grant Lorenz mapped as wetland
• US of Grant Lorenz Road
— MCWD: Utilize
— NWI: Freshwater Emergent wetland
• Between Arbor Creek Lane and Noble Road
— MCWD: Manage 2
— NWI: Freshwater Emergent wetland
Area 5: Grant Lorenz Channel
Impacts - 100 -yr Flood Elevations
Grant Lorenz Channel
953.8
951.7 ( -2.1 ft) -2
Stabilization — G
Grant Lorenz Channel
953.7
951.2 ( -2.5 ft) 0
Stabilization — F
Grant Lorenz Channel
952.0
948.3 ( -3.7 ft) -1
Stabilization — E
Grant Lorenz Channel
948.1
947.3 ( -0.8 ft) 0
Stabilization — D
Grant Lorenz Channel
941.5
941.5 ( -0.0 ft) 0
Stabilization — B
Grant Lorenz Channel
938.1
937.8 ( -0.3 ft) -1
Stabilization —A
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Area 5: Grant Lorenz Channel
Impacts - Peak Flows
Grant Lorenz Channel
9.4; 60%
Stabilization — G
Grant Lorenz Channel
10.1; 67%
Stabilization — F
Grant Lorenz Channel
61%
Stabilization — E
`12.9;
A
Grant Lorenz Channel
14.4; 57%
Stabilization — D
Grant Lorenz Channel
15.3; 56%
Stabilization — B
rL
Grant Lorenz Channel
16.2; 54%
Stabilization —A
35
36
15.4; 51% 37.6; 51% 107.1; 48%
16.3; 60% 40.8; 53% 118.1; 50%
18.6; 58% M1.7; 56% 121.9; 52%
20.9; 54% 45.3; 53% 123.5; 52%
22.0; 52% �; 50% 132.1; 51%
23.0; 51 % 49.0; 50% 136.7; 50%
Area 5: Grant Lorenz Channel
Potential Solutions
• GL1: Smithtown Pond
(Moderate) with modified
outlet
— 2 x 3' RCP @ 952.0 ftMSL
— Rate /Flood Control and WQ
Treatment
• 1.7 acre -ft of additional WQ
treatment volume
• 7.7 acre -ft of Additional Flood
Control Volume
• Stabilization along Channel
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Area 5: Grant Lorenz Channel
Potential Solutions
■ Reconfiguration of culvert
crossing on Grant Lorenz
Road
■ Stabilization along channel
— More use of rip rap /hard armor
— Biostabilization measures
Area 5: Grant Lorenz Channel
Impacts - Peak Flows
Grant Lorenz Channel
19.6; 17% 24.8; 200/c
67.2; 12% 66.6; 20%
Stabilization — G
Grant Lorenz Channel
21.2; 31% 27.4; 33%
74.3; 15% 189.9; 20%
Stabilization — F
Grant Lorenz Channel
21.7; 34%
76.0; 21% 200.6; 20%
Stabilization — E
Grant Lorenz Channel
21.9; 35% 28.4; 38%
82.4; 14% 204.7; 21%
Stabilization — D
Grant Lorenz Channel
22.0; 36% 28.5; 38%
76.8; 20%
Stabilization — B
.
-
—
Grant Lorenz Channel
22.9; 35% 29.7; 37%
78.9; 20% 219.0; 20%
Stabilization —A
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Area 5: Grant Lorenz Channel
Impacts - 100 -yr Flood Elevations
Grant Lorenz Channel
953.8
953.4 ( -0.4 ft)
0
Stabilization — G
MW
Grant Lorenz Channel
953.7
953.3 ( -0.4 ft)
0
Stabilization — F
Grant Lorenz Channel
952.0
950.7 ( -1.3 ft)
Stabilization — E
�-
Grant Lorenz Channel
948.1
947.9 ( -0.3 ft)
0
Stabilization — D
Grant Lorenz Channel
941.
941.5 ( -0.0 ft)
—�
Stabilization — B
Grant Lorenz Channel
938.1
938.0 ( -0.1 ft)
0
Stabilization —A
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Area 5: Grant Lorenz Channel
Potential Solutions
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Stabilization Measures - Cross Vanes /Rock Vanes
•F � • -, '+. ; Y '•"` BSc' ' - � � -.y� c �' _
41
Area 5: Grant Lorenz Channel
Potential Solutions
Stabilization Measures - Root Wads /Toe Wood
la .
-.der - ..� �•: _ : ��. .A. - • `
r: 1
42
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Area 5: Grant Lorenz Channe
Potential Solutions
43
Area 5: Grant Lorenz Channe
Potential Solutions
44
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:F�l �a� r"
.. S " ^.° .`:Y:.: y�:�.155�: 72 T. •wli ..
-, wa ...: 'IC.'.;�.
43
Area 5: Grant Lorenz Channe
Potential Solutions
44
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Area 5: Grant Lorenz Channel
Impacts & Costs
Existing Conditions 956.6
GL1: Smithtown
956.6 1/0 9.0 $3,910,000
Pond (Maximized) w/
Extended Detention
& Channel
Stabilization
GL2: Smithtown
956.5 1 /0 6.9 $2,160,000
Pond (Moderate) w/
Extended Detention
& Channel
Stabilization
*Costs include Engineering, Design, and Permitting (25%)
BABAR
Based on limited design, uncertainty in cost -30% to +50%
45
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Area 2: Strawberry Lane — North of Trail
Issues
■ Flat topography /limited
drainage
■ Existing draintile system
along ditches that
connects to storm that
drains to Pebble Brook
— Rate of drainage limited by
infiltration through ditch
EA VA
Previous
Recommendation
t
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i 3■
48
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24
Pebble Brook - Existing Conditions
Channel
Section
Bani full Depth
00
Slope (ft /ft)
Parameter
1- r
2- r
10- r
100- r
Pebble Brook
Upstream
0.4
0.0122
Flow (cfs)
5.7
6.8
41.2
137.5
Velocity (ft /s)
2.0
2.1
4.1
6.0
Max Depth (ft)
05
0.6
1.4
3.0
Shear (Ibs /ft3)
0.4
0.4
1.1
23
Pebble Brook
Downstream
1.4
0.0198
Flow (cfs)
5.7
6.8
41.2
136.6
Velocity (ft /s)
2.0
2.1
3.9
4.4
Max Depth (ft)
1.5
1.7
2.9
5.9
Shear (Ibs /ft3)
1.9
2.1
3.5
7.3
•
•
•
The upper portion of the channel is connected to the floodplain (over bankfull
depth) during smaller events
Velocities exceed thresholds for erosion without well established vegetation or
other stabilization during the 10/100 year events
Shear Stress typically at or exceeds vegetation thresholds
BARR
49
Area 2: Strawberry Lane
Potential Solutions
■ SL1: Installation of storm sewer & stabilization of Pebble
Brook
■ SL2: Installation of storm sewer, expansion of downstream
stormwater pond (3 properties), & stabilization of Pebble
Brook
■ SL3: Installation of storm sewer, expansion of downstream
stormwater pond (3 properties), & expansion of storage to
west (1 property), & stabilization of Pebble Brook
■ Diversion of wetland (M1) west to Cathcart and Afton -
BARB
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25
Area 2: Strawberry Lane
Potential Solutions
■ SL1: Installation of
storm sewer &
stabilization of Pebble
Brook
51
Area 2: Strawberry Lane
Potential Solutions
■ SL2: Installation of storm
sewer, expansion of
downstream stormwater
pond, & stabilization of
Pebble Brook
— 26370 Peach Circle
— 26390 Peach Circle
— 5915 Strawberry Lane
52
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I =�
�r -1 _ �.v
t.
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BARRR
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BARR
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Area 2: Strawberry Lane
Potential Solutions
■ SL3: Installation of storm
sewer, expansion of
downstream stormwater
pond, expansion of storage
west of road, &
stabilization of Pebble
Brook
— 26370 Peach Circle
— 26390 Peach Circle
— 5915 Strawberry Lane
— 5970 Strawberry Lane
53
Area 2: Strawberry Lane
Potential Solutions
■ SL4: Diversion of
wetland M2 via
easement, Cathcart
Drive, Afton Road via
storm sewer & raise
natural overflows
54
=R
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Area 2: Strawberry Lane
Impacts & Costs
Existing Conditions 970.6
969.1
2/7
0.7
SL1: Storm sewer & 970.1
968.4
0/3
0.7
$650,000
Channel Stabilization
SL2: Storm sewer, Pond 970.2
968.5
0/4
1.1
$830,000
Expansion (east), &
Channel Stabilization
SL3: Storm sewer, Pond 970.1
968.4
0/3
1.1
$920,000
Expansion (east /west),
& Channel Stabilization
SL4: Wetland Diversion 9703-.
968.9.
0/4
1.1
$990,000
M
*Costs include Engineering, Design, and Permitting (25%)
BARRR
Based on limited design, uncertainty in cost -30% to +50%
55
Area 2: Pebble Brook Peak Flows
Potential Solution Atlas 14 1 -Year, 24- Atlas 14 2-Year, Atlas 14 10-Yea Atlas 14 "I Peak Flow (cfs)
00
Hour Peak Flow (cfs) 24-Hour Peak 24-Hour Peak Year, 24-Hour
Flow (cfs) Flow (cfs)
Existing Conditions 5.7 6.8 41.2 136.6
SL1: Storm sewer & Channel 24.4 31.4 48.5 132.8
Stabilization
SL2: Storm sewer, Pond 18.6 25.1 45.3 111.1
Expansion (east), & Channel
Stabilization
SL3: Storm sewer, Pond 19.6 27.0 46.8 106.1
Expansion (east /west), &
Channel Stabilization
SL4: Wetland Diversion 5.7 6.8 10.9 50.6
BARR
56
11/7/2019
28
57
Area 1: Shorewood Oaks Sump System
Issues
• Current system designed in1985
• Sumps on —50 homes connect to
sump drain system (6" PVC) that
connects at the storm sewer
manhole at the low point on
Shorewood Oaks
— invert 962.52 ft MSL
— System primarily below 964.0 ft MSL
■ Storm system to Freeman Park
surcharges during rain events and
results in flooding residences during
intense events
— No GW issues in between events
per comment from resident
58
Freeman Park
connection
low
point/sump
connection
1 —ago
BARR
11/7/2019
29
Area 1: Shorewood Oaks Sump System
Issues
964
Invert at Storm Manhole 962.52
963
1 -yr 962.4 / 964.1
963.3 / 964.4
10 -yr 966.5 / 966.5
969.5 / 970.9
59
1 Wed 2 Thu 3 Fri
BARR
Previous
Recommendation
^•-a`
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-
970
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969
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p - k . •�,
968
967
- -
-
966
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965
964
Invert at Storm Manhole 962.52
963
1 -yr 962.4 / 964.1
963.3 / 964.4
10 -yr 966.5 / 966.5
969.5 / 970.9
59
1 Wed 2 Thu 3 Fri
BARR
Previous
Recommendation
s W .. y■ 3 S w
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t
Fi�
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11/7/2019
30
Area 1: Shorewood Oaks Sump System
Potential Solutions
• S01: Abandon sump system and require private property
owners to daylight sump pump /foundation drain
discharges at surface
• S02: Separate the sump system from the primary storm
system, requiring additional piping and a lift station
discharging to surface and gravity draining to Freeman Park
• S03: Installation of inline backflow preventors on sump
lines into storm sewer
■ SO4: Lower flood elevation at Freeman Park
61
Area 1: Shorewood Oaks Sump System
Potential Solutions
■ S01: Abandon sump system and require private
property owners to daylight sump pump /foundation
drain discharges at surface
— Line /Fill sump system piping and bulkhead at storm manhole
• —4300 LF of 6" PVC
— Daylight —50 homes
• Make sure daylighted sumps can drain via gravity to storm
62
BARR
BARR
11/7/2019
31
Area 1: Shorewood Oaks Sump System
Potential Solutions
■ 502: Separate the sump system from the primary storm
system, requiring additional piping and a lift station
discharging to surface and gravity draining to Freeman
Park
— SO homes @ 40 gpm = 2000 gpm lift station (20 hp, 3
phase power)
— If lift station sized to half peak capacity (S hp, single
phase power)
■ Uncertainty that this will solve fully -solve issue
— Sump pumps typically have limited head they can
pump against
• Will Eliminate Surcharge: Much of the sump system is below the
storm system peak flood elevations (1, 2, 10, 100 -yr)
• Does not address Capacity: Potential gravity capacity issue of
single 6" line (5-10% of peak pumping rate) /two 6" lines (10 -20%
of peak pumping rate)
63
W
kV'0Aff*ALV—r_
Area 1: Shorewood Oaks Sump System
Potential Solutions
• 503: Installation of inline backflow preventors on
sump lines into storm sewer
— Two 6" PVC connections at storm sewer
— TideFlex Checkmate — 83 ft of backpressure rating
• Uncertainty that this will solve the surcharge issue,
may make worse
— 2014 - Pumps were running when back -up occurred
Pumps should have check valves /backflow preventors — so no back
up through the pump
More likely unable to pump against system head downstream,
sump overwhelmed by foundation drain
— Sump pumps typically have limited head they can pump
against
Surcharge: Much of the sump system is below the storm system
peak flood elevations (1, 2, 10, 100 -yr)
• Capacity: Potential gravity capacity issue of single 6" line (5 -10%
of peak pumping rate) /two 6" lines (10 -20% of peak pumping rate)
64
c
BARR
BARR
11/7/2019
32
Area 1: Shorewood Oaks Sump System
Potential Solutions
■ SO4: Lowering flood elevation at Freeman Park
— Limited opportunity to reduce flood elevations without
developing significant additional storage (17.9 ac -ft)
Proposed Existing Elevation ...
(Freeman) (Lowered • Outlet
Invert at Storm Manhole 962.52
1 -yr 962.4 961.2 ( -1.2 ft) 958.3 ( -4.1 ft)
2 -yr 963.3 962.3 ( -1.0 ft) 958.7 ( -4.6 ft)
10 -yr 966.5 966.1 ( -0.4 ft) 961.1 ( -5.4 ft)
100 -yr 969.5 969.4 ( -0.1 ft) 967.1 ( -2.4 ft)
BARR
65
Area 1: Shorewood Oaks Sump System
Costs
S01: Abandon and Daylight
S02: Separate Lift Station
S03: Backflow prevention
SO4: Lower Flood Elevation at Freeman Park
*Costs include Engineering, Design, and Permitting (25 %)
Based on limited design, uncertainty in cost -30% to +50%
••
$190,000
$290,000
$22,000
$1,830,000
BARR
11/7/2019
33
Area 6: Sleepy Hollow /Noble Road
Issues
67
Area 6: Sleepy Hollow /Noble Road
Issues
■ Road floods during some
rain events
■ Wetlands US /DS of Road
Crossing are mapped
— MCWD: Manage 2
— NWI: Freshwater Emergent
Wetland
•i
BARR
y.
BARR
11/7/2019
34
Area 6: Sleepy Hollow /Noble Road
Potential Solutions
■ NR1: Raise Road to 934 ft MSL
( -2 ft), no modifications to 4 x 30"
rise RCPA pipes
■ NR2: Raise Road to 934 ft MSL
and replace existing RCPA pipes
with a Tx 13'* box culvert
*3' x 12' box largest Forterra makes
.•
BARR
Area • Sleepy Road
Impacts
Potential Solution Atlas 14 100 -Year, Atlas 14 100 -Year, Potentially Impacted Preliminary Cost*
24 -Hour Peak Flood 24 -Hour Peak Flood Homes/ Homes Within
Elevation — US Elevation — DS 2 ft
Wetland Wetland
Existing Conditions
NR1: Raise '•.• to 91111
934.0
NR2: Raise '•.• to 1111
934.0 and :•
Culvert
*Based on limited design, uncertainty in cost 0% 0%
70
11/7/2019
35
71
Area 4: Beverly Drive Wetland
Issues
• High flood elevations on Beverly Drive wetland
• Potentially impacted homes
• Pipe is technically private except within right of way
along Cajed Lane
• Pi e is collapsed in low area north of Beverly and west
0 Cajed —flooding backyards and cemetery
• Beverly wetland is mapped as wetland
— NWI: Freshwater Emergent wetland
— MCWD: Manage 1 Wetland
• Cajed low area also mapped as wetland
— MCWD: No Classification
— NWI: Freshwater Emergent wetland
72
11/7/2019
36
Area 4: Beverly Drive Wetland
Potential Solutions
• B1 -B4: Replace drainage
system from Beverly Drive
and along Cajed Lane,
including installation of inlet
in low area north of Beverly
and west of Cajed
• Assume directional drilling
• Sanitary and watermain
along Cajed Lane — avoid
confrict
73
Area 4: Beverly Drive Wetland
Impacts
Potential Solution Atlas 14 100-Year, Atlas 14 100-Year, Atlas 14 100-Year, Potentially Preliminary Cost*
24-Hour Peak 24-Hour Peak 24-Hour Peak Impacted
Flood Elevation - Flood Elevation - Flood Elevation -
Beverly Cajed Edgewood Within 2 ft
Wetland
Existing Conditions 953.3 949.0 932.4 1/2
131: Replace 8 ", Add 8" at 953.2 946.9 932.4 1/0 $580,000
Cajed Low Area
132: Upsize to 15 ", Add 952.7 946.5 932.4 1/0 $640,000
12" at Cajed Low Area
133: Upsize to 24 ", Add 952.3 946.3 932.5 1/0 $750,000
12" at Cajed Low Area
134: Upsize to 24" & 952.0 946.3 932.5 1/0 $750,000
Lower to 948, Add 12" at
Cajed Low Area
*Costs include Engineering, Design, and Permitting (25%)
BARR
Based on limited design, uncertainty in cost -30% to +50%
74
11/7/2019
37
75
Western Shorewood - Preferred Concept
Area 1: Shorewood Oaks
Area 2:
Strawberry Lane
Area 3:
Freeman Park
Area 4:
Beverly Drive
Area 5:
Grant Lorenz
Channel
Area 6: Sleepy
Hollow /Noble Road
Total Cost
Next Steps
Call with agencies including MCWD, USACOE, MnDNR,
M PCA
Further development of the preferred concept
Meeting to review preferred alternative results
Council work session regarding preferred alternative
Public open house presenting preferred alternative
Draft plan and review with City and MCWD staff
Finalize plan
Present final plan to City Council
76
Mid November 2019
Early /Mid December 2019
Mid /Late December 2019
Early January (January 13, 2020)
Mid January 2020
Late January 2020
Mid February 2020
Late February (February 24, 2020)
BARR
BARR
11/7/2019