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AppendixB Western Shorewood Stormwater Management Plan: Preferred Alternatives ReviewWestern Shorewood Stormwater Management Plan: Preferred Alternatives Review Jen Koehler, PE 12/18/2019 BARR 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 ■ BARR 12/18/2019 1 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: Noble Road — No preferred alternative at this time 3 M BARB 12/18/2019 4 2 12/18/2019 to r ro f W .3 JA "i t I n ..a x � drtions tl� ��.r } 9C Area 1: Shorewood Oaks Sump System Issues • Current system designed in 1985 • 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 7 Freeman Park connection low point /sump connection BARR Area 1: Shorewood Oaks Sump System Preferred Solutions 1 L _ o rrY Etta` I • Collect for Reuse - option eliminated • S01: Abandon and Daylight • S02: Separate System and Gravity Drain to North of Regional Trail BARR 12/18/2019 M Area 1: Shorewood Oaks Sump System Preferred Solutions ■ SO1: Abandon sump system and require private property owners to daylight sump pump /foundation drain discharges at surface — Daylight —50 homes — Line /Fill sump system piping and bulkhead at storm manhole? — Some concern by city in oversaturating soils in right of way and under roads with sump discharge X Area 1: Shorewood Oaks Sump System Preferred Solutions ■ SO2: Separate the sump system from the primary storm system and drain to north of regional trail (Smithtown Pond) — Required directional drilling 1600 ft of 8" HDPE to north of regional trail — US invert: 962.5, DS invert: 956.6 (0.35% slope) 10 M BARB M BARR 12/18/2019 5 Area 1: Shorewood Oaks Sump System Costs S01: Abandon and Daylight S02: Separate system and gravity drain to north of regional trail *Costs include Engineering, Design, and Permitting (25 %) Based on limited design, uncertainty in cost -30% to +50% 11 $190,000 $580,000 M BARB 12/18/2019 12 0 Area 2: Strawberry Lane - North of Trail Issues • Flat topography /limited drainage — No issues with flooded structures • Existing draintile system along ditches that connects to storm that drains to Pebble Brook — Rate of drainage limited by infiltration through ditch • Existing erosion in Pebble Brook Creek channel 13 Area 2: Strawberry Lane Preferred Solutions y l 4' 14 3ARR Installation of linear box culvert under proposed trail & stabilization of Pebble Brook — option eliminated SL -1: Storm sewer along Strawberry Lane north to Smithtown, eliminate Strawberry Lane discharge to Pebble Brook Creek SL -2: Storm sewer along Strawberry Lane north to Smithtown, split flows from Storm sewer to the north and Pebble Brook Creek e- 12/18/2019 7 Area 2: Strawberry Lane Preferred Solutions ■ SL -1: Installation of storm sewer under proposed trail routed north to Smithtown Road to the proposed Smithtown Pond — Diversions of all Strawberry Lane runoff away from Pebble Brook Creek — SL -1a: Reduce 100 -year = 48" RCP — SL -1 b: Maintain 100 -year = 18 "RCP 15 Area 2: Strawberry Lane Preferred Solutions ■ SL -2: Installation of storm sewer under proposed trail routed north to Smithtown Road to the proposed Smithtown Pond — Split Strawberry Lane runoff between storm sewer and Pebble Brook Creek, Stabilization along Pebble Brook Creek — SL -2a: Reduce 100 -year = 48" RCP — SL -2b: Maintain 100 -year — 18 "RCP 16 BARR BARR 12/18/2019 17 Area 2: Strawberry Lane Preferred Solutions ■ Directional Drilling Considerations — Any obstructions (gravel, till, cobbles etc.) can be challenging — We have experience directional drilling 42" pipe, typically smaller is easier /cheaper — Need at least 10 feet of separation from edge of existing utility and edge of hole (hole is 1.5x diameter of pipe) — Experienced contractors (especially as you move up in size /complexity) are more expensive but likely worth the cost — Unit costs are all over the board Area 2: Strawberry Lane Preferred Solutions IN MATrM _ ST K TRIPE C-ROS 4' TH ICX INSULATION 096 _ I gI - OA 3rl 04 "r - y (; PVC BEND C o 1 IN STALL SALVAG ED S IGN \ J I FI A` CONSTRUCTION LIAR TS a� I 'S _ 1. SEE SHEETS CROSS SECTIONS FOR DRIVEWAI REPLACe NE 2. SAWCHT EXISTING DITUMINEUS PAV EMENT ( Pl1LL DEPTH) 3- MAIL0OX TO BE RELOCATED. 9. SIGNS TO BE RELOCATEO, r 5. INSTALL 9° TOPSOIL A SEED. &. CATCH BASIN TOP OF CASTINGS ARE DEPRESSED (NEENAH R- 3G67 -V OR APPROVED EOUAL]. 1. THE CONTRACTOR SHALL SALVAGE AND STOCK PILE TUP 18 CIS x 0 0 a N M BARB .SNTOX �MSV�pS,oN JOp 'e. SNNO� `N LOT S, BLOCK 1 PEBBLE BROOK ADDN I BARR 12/18/2019 a Area 2: Strawberry Lane Impacts & Costs Existing Conditio 970.6 SL1a:Storm Sewer & 970.2 Diversion (No Channel Stabilization) — Reduce 100 - year (48 ") SL1b: Storm Sewer & 970.6 Diversion (No Channel Stabilization) — MaintaA'N year (18 ") SL2a: Storm Sewer, Split Flows 970.1 & Channel Stabilization — Reduce 100-year (48") 969.1 2/7 �- 968.9 0/3 0.7 $2,110,000 969.1 1 /3 0.7 $1,080,000 968.8 0/3 0.7 $2,180,000 Storm Sewer, Split 1 /3 $1,150,000 Flows &Channel Stabilization — Maintain 100 -year (18 ") =ME T� *Costs include Engineering, Design, and Permitting (25 %) Based on limited design, uncertainty in cost -30% to +50% 19 BARR Area 2: Pebble Brook Peak Flows Potential Solution Atlas 14 1 -Year, 24- Atlas 14 2 -Year, Atlas 14 10 -Year, Atlas 14 100 - Hour Peak Flow (cfs) 24 -Hour Peak 24 -Hour Peak Year, 24 -Hour Flow (cfs) Flow (cfs) Peak Flow (cfs) Existing Conditions 5.7 • : 26.4 135.0 Storm : Diversion • Channel Stabilization) Storm • Flows, & Channel Stabilization BARR 20 12/18/2019 10 12/18/2019 21 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) 22 M BARR 11 Area 3: Freeman Park Issues Icy^ � SfP cwl rn P1K tKmc -mvsue or � -i. 3 a FP1 R pl and low 1111W IM Fl------ N . n �. .. P"nnWA ,J ", SS of �a \STi tt� \ cyFF'➢ wV.9S95 y0 �� I �� QO 57UCTLU 2E w BARB 23 Area 3: Freeman Park Preferred Alternative 24 12/18/2019 12 3 a FP1 R pl and low 1111W IM Fl------ N . n �. .. I �� QO - ���� « °,� � �: �. .. i'-\: � �� •r, �'1 ':r�r BAR 24 12/18/2019 12 25 Area 3: Freeman Park Preferred Alternative • FP1: Lower outlet elevation to 957.5 — Will require a small amount of grading/ excavation at inlet • Conceptual design that minimizes maintenance — Bollards to prevent movement of large debris to trash rack — Oversized inlet with trash rack — Overflow at 10 -year event Area 3: Freeman Park Impacts & Costs Monditio� A� FP1: Lower Outlet to 957.5 969.5 0/0 N/A More significant peak elevation reductions during more frequent events (1 -yr, 2 -year) *Costs include Engineering, Design, and Permitting (25 %) Based on limited design, uncertainty in cost -30% to +50% 26 $86,000 BARR BARR 12/18/2019 13 12/18/2019 PAN Area 5: Grant Lorenz Channe Issues ■ High flows /velocities resulting in erosion and sediment transport — Velocities exceed 3 -4 fps in several sections of the channel, likely contributing to erosion without well established vegetation or other stabilization — Downstream of Grant Lorenz Road, the Channel is incised and disconnected from the floodplain — Shear Stress typically exceeds vegetation thresholds during larger events ■ Overtopping driveways and destroying culverts 28 14 Area 5: Grant Lorenz Channe Issues PAS] Area 5: Grant Lorenz Channe Issues 30 m BARB m BARR 12/18/2019 15 Area 5: Grant Lorenz Channe Preferred Solution ■ GL1: Smithtown Pond (Maximized) with — extended detention outlet 1. — 15" x 18" notch weir @ 952.0 ft MSL C — 6' Weir @ 953.5 ft MSL — Rate /Flood Control and WQ Treatment • 1.5 acre -ft of additional WQ treatment volume • 13.7 acre -ft of Additional Flood Control Volume- � — Possible IESF along Pond (-10'x250') I J ■ Stabilization along Channel 31 Area 5: Grant Lorenz Channe Preferred Solutions ■ Reconfiguration of culvert crossing on Grant Lorenz Road ■ Stabilization along channel —Constructed Riffles —Targeted rip rap /hard armor —Targeted grading and vegetation reestablishment 32 BARR 12/18/2019 16 33 Area 5: Grant Lorenz Channe Potential Solutions Assumptions: City can obtain drainage and construction access aagreements Access from east side of channel – limit impacts on home side of channel - Limited tree removal – remains shady, shade tolerant vegetation B =R 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 qwx� 948.6 ( -3.3 ft) -1 Stabilization – E Grant Lorenz Channel 948.1 947.4 ( -0.7 ft) 0 Stabilization – D Grant Lorenz Channel 941.5 ( -0.0 ft) Stabilization – B AM& ML Grant Lorenz Channel 938.1 937.9 ( -0.2 ft) -1 Stabilization –A 34 r 1 BARR 12/18/2019 17 Area 5: Grant Lorenz Channe Impacts - Peak Flows Grant Lorenz Channel Stabilization — G Grant Lorenz Channel Stabilization — F 18.7; 21% 20.1; 34% 24.5; 21% 39.1; 40% 102.1; 50% 25.8; 37% 43.1; 51% 113.1; 51% Grant z Channel F9; Stabilization 20.5; 38% 26.2; 41° 49% Grant Lorenz Channel Stabilization — D 20.7; 39% 26.4; 42% 52.8; 45% 130.8; 48% Grant Lorenz Channel Stabilization — B 20.7; 40% 26.5; 43% 54.9; 43% 146.5; 45% Grant Lorenz Channel Stabilization —A 21.6; 39% 27.7; 41% 56.5; 43% 151.0; 44% 35 Area 5: Grant Lorenz Channe Impacts & Costs Existing Conditions 956.6 1 /0 GL1a: Smithtown 956.6 1 /0 Pond (Maximized) w/ Extended Detention & Channel Stabilization GL1 b: Smithtown 956.6 Pond (Maximized) w/ Extended Detention, IESF, li Channel Stabilization *Costs include Engineering, Design, and Permitting (25 %) Based on limited design, uncertainty in cost -30% to +50% 36 0.5 9.2 UNI $3,580,000 BARR 12/18/2019 im 12/18/2019 [ell 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 • Pipe is collapsed in low area north of Beverly and west of Cajed — flooding back yards 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 38 19 Area 4: Beverly Drive Wetland Issues ■ Survey of low opening at 951.56 NGVD29 — close to LiDAR estimate of 951.5 100 -yr WSE: 953.3 10 -yr WSE: 951.8 2 -yr WSE: 950.9 1 -yr WSE: 950.6 39 12/18/2019 Area 4: Beverly Drive Wetland Impacts Potential Solution Atlas 14 100-Year, Atlas 14100-Year, Atlas 14 100-Year, Potentially Planning Level Cost* 24-Hour Peak 24-Hour Peak 24-Hour Peak Impacted Flood Elevation - Flood Elevation - Flood Elevation - Wetland Existing Conditions J� 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 ", Ad 952.7 946.5 I 1/0 $640,000 12" at Cajed Low Are 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 MINE- ` *Costs include Engineering, Design, and Permitting (25 %) B =R Based on limited design, uncertainty in cost -30% to +50% 40 20 41 Area 4: Beverly Drive Wetland Preferred Solution ■ 131: 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 (8 ") — Sanitary and watermain along Cajed Lane — avoid conflict Area 4: Beverly Drive Wetland Impacts 12/18/2019 Existing Conditions 953.3 949.0 932.4 1 / 2 B1: Replace 8" at Beverly, 953.2 946.9 932.4 1/0 $580,000 Add 8" at Cajed Low Area *Costs include Engineering, Design, and Permitting (25 %) BARRR Based on limited design, uncertainty in cost -30% to +50% 42 21 Western Shorewood - Preferred Concept Summary Area 1: Shorewood S01: Daylight and Abandon S01: $190,000 S01: Independent of other Oaks S02: Separate and Discharge North of S02: $580,000 projects Regional Trail S02: After Smithtown Pond (due _ 111 to discharge elevation) Area 2: Strawberry SL1: Storm Sewer North to Smithtown SL1: $1,080,000 SL1: After Smithtown Pond Lane Road SL2: $1,150,000 SL2: After Smithtown Pond SL2: Storm Sewer North to Smithtown Road, Split Flows & Channel Stabilization Area 3: Freeman FP1: Lower outlet FP1: $86,000 FP1: After Smithtown Pond (due Park i i i fro discharge elevation) M Area 4: Beverly BW1: Replace 8" at Beverly, Add 8" at Drive Cajed Low Area Area 5: Grant Lorenz GL1a: Smithtown Pond and Channel Channel Stabilization i GL1b: Smithtown Pond, IESF and Channel Stabilization Area 6: Noble Road N/A *Costs include Engineering, Design, and Permitting (25 %) Based on limited design, uncertainty in cost -30% to +50% 43 Next Steps Total Cost BW1: $580,000 Independent of other projects GL1a: $3,580,000 Smithtown Pond (& IESF) should G L 1 b: $3,640,000 be constructed prior to channel ab'lization N/A N/A Finalize preferred alternative based on today's meeting Late December /Ear&aanuary 2020 Council work session regarding preferred alternative Mid January (January 13, 2020) Pullen house presentingferred alternativ�muary 2020 Draft plan and review with City and MCWD staff Late January 2020 Finalize pl Vd February 2020 Present final plan to City Council Late February (February 24, 2020) • Council work session - Format /length? Time? City will schedule? • Public open house — week of January 20 -24? Format /length? Time? City will schedule /advertise? 44 BARR 12/18/2019 22