Project Summary Existing Conditions Lane Culvert Analysis.pdfthis analysis. There is currently only...

18-22627 256th Lane Crossing 1

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Figure 1: Existing Culvert Condition Figure 2: Roadway Over Crossing

July 9, 2019

Aaron Goemann

County Ditch Inspector

Sibley County

P.O. Box 51

Gaylord, Minnesota 55334-0051

RE: Sibley County JD No. 18 Culvert Analysis

Project Summary

I+S Group (ISG) has completed a hydraulic analysis and culvert design of the Judicial Ditch No. 18 (JD

18) 256th Lane crossing located in Section 20 of Dryden Township. JD 18 begins in Section 22 of Bismarck

Township and runs north to Section 35 of Round Grove Township, it then runs east to Section 2 Transit

Township, and then finally southeast where it outlets into Titlow Lake in Section 29 of Dryden Township.

Existing Conditions

ISG performed topographic survey of the crossing in January 2019 including full cross sections of the

roadway and ditch for 1,000 feet. Three road crossings upstream were also observed for culvert sizes and

conditions. There are currently 10x10 dual box culverts located at two of the upstream crossings on

Highway 22, and 481st Avenue. JD 18 has a bottom width of 20 feet and side slopes of 3:1. The 256th

Lane crossing currently consists of a 126-inch rise by 198-inch span CMP with an upstream invert elevation

of 981.40 (MSL) and a downstream invert elevation of 981.32. The total length of the culvert is 36-feet

and it runs southeast across 256th Lane.


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The existing 256th Lane is a 12-foot wide roadway with no shoulders. The road centerline includes a

defined low area about 300 feet east of the crossing for roughly 1,000 feet at an elevation of 988.00. The

roadway has little to no crown and is flat across throughout most of its length. The side slopes of the

roadway are not consistent but are most commonly 5:1 slopes. At the existing crossing the roadway has

been built up on top of the culvert to provide more cover creating a bump in the road. This can be seen

in Figure 2 above. 256th Lane provides access for one resident.

There are a variety of concerns with this crossing that were taken into consideration for the purposes of

this analysis. There is currently only 0.39 feet of cover on the culvert. The existing road is a 12-foot gravel

road with no shoulders. There is currently several low spots located east of the crossing that cause the

road to be overtopped in the event of heavy rain storms including a 5-year storm event or higher.

Hydraulic Model

A hydraulic model was created utilizing HEC-RAS software to analyze different culvert alternatives to

replace the existing culvert crossing. The watershed was delineated utilizing USGS StreamStats and ESRI

ArcMap and is approximately 20,186 acres. Maps showing the watershed and project location are included

in the attachments. Peak flow rates were generated utilizing StreamStats and compared to typical values

for watersheds of similar size to the JD 18 crossing. The model utilized the 2, 5, 10, 25, 50, 100, and

500-year rainfall frequencies for design of the proposed culvert as shown below in Table 1.

Table 1: Peak Flow Rates Utilized

Three different improvement scenarios were analyzed along with the existing conditions. These three

scenarios were: replacing the existing 126-inch rise by 198-inch spam CMP arch culvert with a 10x10 dual

box culvert, replacing the existing with a 10x8 box culvert, and raising the low spot in the road along with

installing a 10x8 box culvert.

The capacity of culverts is expressed as a drainage coefficient, in inches per day (in/day), and is defined

as the depth of water over the entire area of the upstream watershed that a tile or culvert can drain in a

24-hour period. For a system like JD 18 the Natural Resources Conservation Service (NRCS) recommends

a drainage coefficient of 1.0 in/day for open ditches. The existing and proposed culvert capacities for

256th Lane are shown below in Table 2.

Rainfall

Frequency

Peak

Flow

(cfs)

2-Year 176

5-Year 378

10-year 559

25-Year 842

50-Year 1090

100-Year 1380

500-Year 2170


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Table 2: Existing and Proposed Drainage Capacities

All of the proposed and existing culvert crossing options are above the recommended drainage coefficient.

Although the drainage coefficient for the 10x8 culvert is lower than the existing arch culvert, the water

base of a dual box culvert allows for more capacity at a lower elevation. This provides more flow at a

lower elevation through the roadway, which decreases the potential of the road overtopping. The peak

flood elevations (MSL) from the HEC-RAS model can be seen in Tables 3-8.

After analyzing the existing conditions, it was determined that the existing culvert across 256th Lane does

not have adequate capacity to drain the existing watershed and keep the road from overtopping. As seen

in Table 6, the road will overtop on 5-year flood events under the existing conditions. Knowing that the

upstream crossings consist of 10x10 dual concrete box culverts, this option was analyzed first to replace

the existing arch culvert. It was found that this increase in capacity decreases the peak water elevations

so that the road will overtop on 25-year flood events. However, it provides a minimal cover to the

proposed box culverts of 0.95-feet. Therefore, a 10x8 dual box culvert was analyzed. This option has

similar peak elevation results to the 10x10 proposed box culvert, but allows for an additional 2-feet of

cover for the proposed culvert. Both the proposed 10x8 and 10x10 reduce the upstream water elevations

by over 3 inches on the higher flood events. Knowing that the road still overtopped on 25-year flood

events due to the low spot in the roadway, a third option of raising the roadway elevation 2 feet in the

low area to 990.00 MSL and installing a 10x8 dual box culvert was analyzed. In this scenario, the road

would overtop on 50-year flood events.

Despite upsizing the road culvert, water will continue to flow through the culvert and back across the road

300 feet east of the crossing over the low spot in the road. This can be seen in the downstream HEC-RAS

results in Tables 6 and 7. The existing road at an elevation of 988.00 MSL in the low area will be

overtopped in the 25-year storm by 1.3 feet for both the 10x8 and 10x10 culverts without raising the

roadway.

Culvert

TypeSize (feet) Slope (%)

Drainage

Area

(acres)

Capacity

(cfs)

Total

Capacity

(cfs)

Drainage

Coefficient

(in/day)

Total

Drainage

Coefficient

(in/day)

Existing Arch 16.5 x 10.5 0.22% 20186 2000 2000 2.36 2.36

8 x 10 0.22% 20186 910 1.07

8 x 10 0.22% 20186 910 1.07

10 x 10 0.22% 20186 1200 1.41

10 x 10 0.22% 20186 1200 1.41

2.15

2.83

1820

2399

Proposed

Proposed

Dual Box

Dual Box


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Table 3: HEC-RAS Results 1,320 Linear Feet

Upstream of Crossing

Table 4: HEC-RAS Results 900 Linear Feet

Upstream of Crossing


Downstream of Crossing

Table 8: HEC-RAS Results 1,000 Linear Feet

Downstream of Crossing


Upstream of Crossing Table 6: HEC-RAS Results at Crossing

Flood

Event

(Year)

Existing

Arch

Proposed

10x10

Proposed

10x8

Proposed

10x8 Raised

Road

2 987.87 986.56 986.56 986.56

5 989.60 987.98 987.98 987.98

10 990.13 988.90 988.90 988.90

25 990.78 990.04 990.04 990.04

50 991.28 990.67 990.67 990.83

100 991.82 991.23 991.25 991.49

500 993.41 992.38 992.39 992.52

Flood

Event

(Year)

Existing

Arch

Proposed

10x10

Proposed

10x8

Proposed 10x8

Raised Road

2 987.81 986.31 986.31 986.31

5 989.53 987.69 987.69 987.69

10 990.02 988.59 988.59 988.59

25 990.63 989.76 989.76 989.77

50 991.11 990.40 990.40 990.61

100 991.65 990.97 990.99 991.31

500 993.46 992.31 992.32 992.52

Flood

Event

(Year)

Existing

Arch

Proposed

10x10

Proposed

10x8

Proposed 10x8

Raised Road

2 987.48 985.47 985.47 985.47

5 989.39 986.83 986.83 986.83

10 989.80 987.70 987.70 987.70

25 990.24 989.29 989.29 988.74

50 990.55 989.87 989.87 990.17

100 990.90 990.35 990.39 990.85

500 992.45 991.55 991.56 991.87

Flood

Event

(Year)

Existing

Arch

Proposed

10x10

Proposed

10x8

Proposed

10x8 Raised

Road

2 985.39 985.28 985.28 985.28

5 986.69 986.51 986.51 986.51

10 987.48 987.27 987.27 987.27

25 988.26 988.07 988.07 988.07

50 988.82 988.67 988.67 988.67

100 989.39 989.29 989.29 989.29

500 990.59 990.75 990.75 990.75

Flood

Event

(Year)

Existing

Arch

Proposed

10x10

Proposed

10x8

Proposed

10x8 Raised

Road

2 982.47 982.47 982.47 982.47

5 983.09 983.09 983.09 983.09

10 983.47 983.47 983.47 983.47

25 983.93 983.92 983.92 983.92

50 984.27 984.23 984.23 984.23

100 984.60 984.53 984.53 984.53

500 985.30 985.06 985.06 985.06

Flood

Event

(Year)

Existing

Arch

Proposed

10x10

Proposed

10x8

Proposed 10x8

Raised Road

2 987.98 986.82 986.82 986.82

5 989.81 988.44 988.44 988.44

10 990.51 989.52 989.52 989.52

25 991.46 990.94 990.94 990.94

50 992.24 991.89 991.89 992.00

100 993.12 992.86 992.87 993.03

500 995.60 995.31 995.31 995.37


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Proposed Alternatives

Option 1

Option 1 for this crossing is to install a 10-foot by 8-foot dual box culvert. This will maintain close to the

same capacity and lower the peak flood elevations upstream of the crossing by up to 2 feet in higher flood

events. It will provide adequate cover of 2.56 feet on the culvert, much more protection than the existing

0.39 feet. The 10-foot by 8-foot dual box culvert will be placed at the existing invert elevations of 981.40

upstream and 981.32 downstream. The total width of the dual culvert will be 22.5 feet which will be

slightly wider than the existing channel width of 20 feet.

This option is proposed over the 10x10 dual box culvert analyzed as it still reduces the occurrence of the

road overtopping to the 25-year flood event and while also providing an appropriate amount of cover over

the culvert. The additional capacity in the 10x10 does not help with the overtopping frequency as the

roadway to the east will still over top with a larger culvert. The extra 2-feet in height of the 10x10 is at

an elevation that is higher than the low spot in the roadway to the east.

Option 2

Option 2 is to leave the existing crossing as is until more funding is available. The culvert appears to be

in good condition and currently only supplies access to one resident. With the existing road geometry,

overtopping is inevitable due to the low elevation of the road running parallel to the ditch as described

above. Without raising the road, a new culvert will continue to flood this crossing with relative frequency.

Option 3

Option 3 is to raise the road 2 feet in the low area from an elevation of 988.00 to 990.00. The roadway

would be constructed to its existing 12 foot wide conditions with a 5:1 side slope. This would require

about 1,500 CY of fill over a length of roadway about 1,000 feet long. A 10x8 dual box culvert would be

installed to increase the capacity of the crossing and the raised road would prevent the water from flowing

over the road in the low area east of the crossing. This would prevent overtopping of the road up to the

50-year storm event. It also provides the 2.56 feet of cover on the culvert and decreases upstream flood

elevations. In the event of a 100-year storm the road would be overtopped in the same area 300 feet

east of the crossing.

Cost Estimate

For all proposed options, the culvert should be armored with Class III riprap a minimum of 10-feet out

on the upstream end and 20-feet out from the outlet end to protect from scour and erosion. Additional

riprap will be required to protect the bend on the downstream side. Table 9 shows a cost summary for

Options 1 and 3.

Table 9: Proposed Option Cost Summaries

Item No. Item Unit Quantity Unit Price Amount

101 MOBILIZATION LS 1 20,000.00$ 20,000$

102 10x8 DUAL BOX CULVERT LF 40 2,300.00$ 92,000$

103 10x8 DUAL BOX CULVERT END SECTION EA 2 14,950.00$ 29,900$

104 BACKFILL CY 20 12.00$ 240$

105 CLASS III RIPRAP WITH GEOTEXTILE FABRIC CY 100 75.00$ 7,500$

106 REMOVE METAL CULVERT LS 1 1,500.00$ 1,500$

107 OPEN CUT & RESTORE GRAVEL ROAD OR DRIVEWAY EA 1 1,700.00$ 1,700$

152,840$ Total

OPTION 1


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Please feel free to contact me at 507-387-6651 or at [email protected] with any questions

regarding the design of culvert.

Sincerely,

Mark Origer, PE

Civil Engineer Enclosures: Watershed Map Location Map Cross Section Location Map Cost Estimate


101 MOBILIZATION LS 1 20,000.00$ 20,000$



104 COMMON BORROW CY 1,500 12.00$ 18,000$


106 AGGREGATE BASE (CV) (P), CLASS V CY 225 27.00$ 6,075$



176,675$ TOTAL

OPTION 3

Section 36Penn Township



















Section 17Penn Township Section 16

Penn Township Section 15Penn Township



Section 9Dryden Township







Section 6Sibley Township



Section 9Transit Township





Section 4Transit Township Section 3

Transit TownshipSection 2Transit Township







Section 28Dryden Township Section 27

Dryden Township










Section 6Cornish Township






Section 9Bismarck Township




































Section 32Gaylord Township

Section 6Winthrop Township

Section 5Alfsborg Township































Section 34New Auburn Township




Section 30New Auburn Township Section 29

New Auburn TownshipSection 28New Auburn Township





Section 18New Auburn Township Section 17

New Auburn TownshipSection 16New Auburn Township

Section 36Round Grove Township






















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SibleyCounty

McLeodCounty

S:\Projects\22000 PROJ\22600-22699\22627 Sibley CO JD No 18 Culvert Analysis-Sibley CO MN\22627 GIS\22627 MapDocs\22627 Watershed Map.mxd

1 inch = 5,500 feet

LegendJD18Watershed

0 2,750 5,5001,375Feet

µ

Orthophotograph (MnGeo WMS, 2015)Tile/Ditch (Renville County, 2016)

Parcels (Renville/Sibley County, 2017/2018)Lakes (MN DNR, July, 2008)

Major Stream (MN DNR, July 2008)Counties (MN DNR, July 2013)

PLSS (MnGeo/USGS)

PN: 18-22627Source:

ExistingWatershed Map

Hydraulic AnalysisSibley County,

MinnesotaMonday, May 20, 2019

HennepinCounty

WasecaCounty

WrightCountyMeeker

County

McLeodCounty

CarverCounty

RenvilleCounty

ScottCounty

SibleyCounty

Le SueurCounty

BrownCounty

NicolletCounty

BlueEarth

CountyWatonwanCounty

256th Lane Crossing WatershedTotal Area = 20,186 Acres

Section 21Dryden TownshipSection 20

Dryden Township


Section 17Dryden Township Section 16

Dryden Township

WARREN W WENTZLAFF

LARRY L & DEBRA J PODRATZDARLENE A KRANZ

JOAN E & VIRGIL W ROEPKE

WOESTEHOFF FAMILY FARM PROPERT

THOMAS JACOBSON &


PATRICIA FREDRICKSON ET AL

DARLENE A KRANZ

DARLENE A KRANZ

DARLENE A KRANZ

STEVEN J & JOAN T HEINZ

LARRY L & DEBRA J PODRATZ


JONATHAN SUEDBECK &

ALFRED R & JUDITH M HOLMBECK

TYLER M & JULIE K KRANZ

JAMES SCHULTE ET AL


JONATHAN SUEDBECK &

ROBERT S UTENDORFER REVOC TRST


JONATHAN SUEDBECK &

STEVEN E & AUDREY L HARTERLARRY L & DEBRA J PODRATZ



250th St

MNTH

22

481s

t Ave

256th La

471s

t Ave

ßß

ªATOSENNIM

22SibleyCounty

S:\Projects\22000 PROJ\22600-22699\22627 Sibley CO JD No 18 Culvert Analysis-Sibley CO MN\22627 GIS\22627 MapDocs\22627 Location Map.mxd

1 inch = 500 feet

LegendJD 18Watershed

0 250 500125Feet

µ




PLSS (MnGeo/USGS)

PN: 18-22627Source:

Location MapHydraulic Analysis

Sibley County, Minnesota

Friday, February 1, 2019

MeekerCounty

RenvilleCounty

McLeodCounty

SibleyCounty

Nicollet County

Project Location






WARREN W WENTZLAFF


LARRY L & DEBRA J PODRATZLARRY L & DEBRA J PODRATZ


WOESTEHOFF FAMILY FARM PROPERT JONATHAN SUEDBECK &

ROBERT S UTENDORFER REVOC TRST

JAMES SCHULTE ET ALALFRED R & JUDITH M HOLMBECK



STEVEN E & AUDREY L HARTERLARRY L & DEBRA J PODRATZ

256th La

MNTH

22

ßß

ªATOSENNIM

22

SibleyCounty

S:\Projects\22000 PROJ\22600-22699\22627 Sibley CO JD No 18 Culvert Analysis-Sibley CO MN\22627 GIS\22627 MapDocs\22627 Cross Section Map.mxd

1 inch = 300 feet

LegendJD 18Cross SectionsWatershed

0 150 30075Feet

µ




PLSS (MnGeo/USGS)

PN: 18-22627Source:

Cross Section Map

Hydraulic AnalysisSibley County,

MinnesotaTuesday, June 18, 2019

CarverCounty

BrownCounty

McLeodCounty

SibleyCounty

NicolletCounty


Project Location


101 MOBILIZATION LS 1 20,000.00$ 20,000$



104 BACKFILL CY 20 12.00$ 240$




152,840$


101 MOBILIZATION LS 1 20,000.00$ 20,000$



104 COMMON BORROW CY 1,500 12.00$ 18,000$


106 AGGREGATE BASE (CV) (P), CLASS V CY 225 27.00$ 6,075$



176,675$ TOTAL

OPTION 1

SIBLEY COUNTYJUDICIAL DITCH No. 18

Total

OPTION 3

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