SD_FLAP CR23A(1)_FinalHydraulicsMemo.pdf

CFLHD | SD FLAP CS23(1)

Final Hydraulics Recommendations Memo hdrinc.com 1670 BroadwaySuite 3400Denver, CO 80202-4824

(303) 764-1520

Memo Date: Thursday, February 02, 2023

Project: SD FLAP CS23A(1) Delta-01 Access Road

To: Aaron Estep, CFLHD; Nate Mascarenas, CFLHD

From: Amy Finseth, HDR

Subject: Final Hydraulics Recommendations Memo

Introduction Jackson County Road CS-23(A) provides the sole access to the Delta-1 Launch Control Facility, which is a part of the Minuteman Missile National Historic Site. The existing gravel roadway is deteriorated with washboards and potholes and cannot support continued or increased vehicular traffic by heavy recreational vehicles, campers, tour buses, and local heavy agricultural equipment.

The proposed project includes clearing and grubbing, rehabilitation, widening, and asphalt paving of the existing aggregate section of approximately 0.5 miles of Jackson County CS-

23(A). The project limits are from the existing asphalt limits, approximately 900 feet north of the westbound (WB) Interstate 90 (I-90) ramp intersections, to the intersection just north of the

Delta-01 visitor parking access. The proposed roadway will be 24-foot width with 11-foot lanes and 1-foot shoulders. MUTCD signing and striping will be installed, and drainage and erosion control improvements will be needed at select culverts to maintain the integrity of the proposed roadway and provide for positive flow.

The scope of the drainage for this Project includes analysis of existing culverts and roadside ditches and recommendations for culvert replacement, ditch sections for capacity and temporary or permanent channel lining. Best management practices (BMPs) will be recommended in the memo for sediment and erosion control. The scope of work does not include developing erosion control plans. The Stormwater Pollution Prevention Plans (SWPPP) and Notice of Intent (NOI) will be completed by the contractor.

The Project is located just north of I-90 between Wall and Kadoka at the interchange of I-90 and

CS23(A). The location maps were obtained from the SDDOT Geographic Information Systems

(GIS) maps for state highway data.

CFLHD | SD FLAP CS23(1) Delta01 Final Hydraulics Recommendations

Figure 1 Location Maps

Criteria A drainage design criteria memo was developed for the project and provided to CFL prior to the

30% submittal. Hydrologic and hydraulic components of the project include developing hydrology, culvert, and ditch analysis. Erosion and sediment control measures will also be recommended.

The drainage criteria developed for this Project is based on the U.S. Department of

Transportation Federal Highway Administration (FHWA) Project Development and Design

Manual (PDDM) and local criteria from South Dakota Department of Transportation (SDDOT)

Drainage Manual (DM). Jackson County does not have design criteria. Therefore, SDDOT was referenced for local criteria.

The roadway classification is designated as low-standard road based on 48 ADT (<1500) and non-critical road designation.

Table 1 summarizes drainage design criteria for the drainage components included in the

Project.

Table 1 H&H Criteria

Design Feature PDDM Criteria

Peak Flow Methods Rational Method – up to 200 acres

Rural Regression Equations for areas > 200 acres Culverts

Capacity Design and Stability

Design: 25-yr (cross culverts)

10-yr (parallel culverts)

Check: 100-yr

Headwater Elevation

HW/D

New culverts: less than the bottom of the roadway aggregate base layer

Existing: less than the shoulder hinge point

Headwater depth to culvert diameter ratio, HW/D: 48” or smaller 1.5

WSEL limited by unacceptable hazards to human life or property

Minimum Size Cross-road culvert : 24” or equivalent

Parallel culvert : 18" or equivalent

Pipe Material

Minimum pipe classification

RCP: Class II, Metal 0.064"

50-year service life

Minimum and

Maximum Outlet Velocity

Minimum : 3 fps

Maximum : as determined by HEC22; matching existing channel velocities.

Outlet Protection

* Vo>6 fps consider erosion protection

Vo > 10 fps, consider gabion protection

Vo > 15 fps, consider energy dissipation

Roadside Ditches

Capacity Design 10-yr storm event

New: WSEL less than bottom of roadway aggregate base layer

Existing: WSEL less than shoulder hinge point

Stability Design

Permanent Lining: 10-year flood

Temporary lining: 2-year flood

Determined by permissible shear stress

*Slope Minimum: 0.5%

Slopes at absolute minimum of 0.2% should use a paved section

*Side Slopes 4:1 inslope – 3:1 maximum backslope

*Depth 3.5 ft below elevation of the subgrade shoulder

*SDDOT Typical Channel Lining

(Listed in order of preference)

HEC-15

*Temporary: crimped straw (mulch), erosion control blanket, wood fiber mulch, bonded fiber matrix

*Permanent: vegetation (retardance Class B – see Figure 9.4-A of SDDOT

DM (Chapter 9, page 9-17)

*Indicates local preference/criteria in addition to the PDDM.

The criteria memo developed for the Project is included in Appendix A.

Hydrology Hydrology was developed for local basins, up to 200 acres, using the rational method. Basins exceeding 200 acres used rural regression equations from USGS and included in the DM, Chapter 7 Hydrology. South Dakota (SD) has seven hydrologic subregions. The project is located in sub-region C. The regression equations for sub-region C were developed for basins between 0.06 and 904 square miles (38-578,560 acres). The 25-year regression equation standard error of estimate is 50%.

The DM provides intensity duration curves for each region of the state. The project falls between

Rapid City, Pierre and Winner. The National Oceanic and Atmospheric Administration (NOAA)

Precipitation Frequency Data Server was used to compare the data found for the site with the three locations and was within the range of the three regions. NOAA Atlas 14 point precipitation depths for the project are listed in Table 1 for the frequencies developed for the hydrologic and hydraulic analysis.

Table 2 NOAA Atlas 14, Point Precipitation Frequency Estimates, Rainfall Depth

Duration (minutes)

2-Year (inches)

10-Year (inches)

25-Year (inches)

100-Year (inches)

5 0.34 0.55 0.69 0.91

10 0.50 0.80 1.00 1.33

15 0.61 0.98 1.22 1.62

30 0.82 1.32 1.66 2.19

60 1.00 1.68 2.13 2.86

Soil information was determined using the Natural Resources Conservation Service (NRCS)

Web Soil Survey for Jackson County Area, South Dakota, Northern Part. Information was collected on 5/26/22. The hydrologic soil for the surrounding area is all C and D soils. The larger components include Arvada loam, Nunn loam, Pierre clay and smaller percentages of other loams, complex or clays. The full soil report is included in Appendix B

The DM, Figure 7.9-C includes the rural regression equations for each region. Subregion C equations for the frequencies used on the project are listed in Table 3.

Table 3 USGS Rural Regression Equations for South Dakota, Subregion C

Recurrence Interval (years)

Equation

2 Q = 25 CA 0.569

10 Q = 125 CA 0.579

25 Q = 207 CA 0.573

100 Q = 379 CA 0.566

Runoff drains from southeast to northwest across the site. But also drains from west to east across the site crossing CR23(A) multiple times. Additional contours were needed to determine offsite contributing areas. Data was acquired from Geo Spatial Data Gateway, 10-meter digital elevation model (DEM), to produce two-foot contours to delineate basins initially using ArcMap.

Basin boundary shape files that were then brought into ORD to check with project survey and to delineate smaller basins along the roadway. An overall basin map developed in ArcMap shows the larger offsite basins and local basins along the roadway alignment are shown on the following three maps developed using ORD. Basin Maps are included in Appendix B. Areas on the south and north limits of the project drain along the west side of CR23(A), drain across

CR23(A) through culverts and then merge with the main basin (Basin 1) draining to the low point which then drains across the project from east to west near station 112. Basins are primarily large undeveloped offsite basins with landcover consistent of meadow grass with shallow to steeper drainages. Smaller basins drain along CR23(A) contributing to roadside diches and driveway culverts. The roadside ditches also wind from draining at the toe of slope then away from CR23(A). Table 4 provides a list of each basin contributing to the Site. Basin 1 exceeds

200 acres therefore flows were developed using the rural regression equation for subregions C.

All other basins followed rational method to determine peak flows. Basins were evaluated during the 95% design and some refinements were made. Results are shown in the table below. Full calculations are included in Appendix B.

Table 4 Hydrologic Calculations

Basin ID Area

(acres) C10

Q10

(cfs) C25

Q25

(cfs) C100

Q100

(cfs) 1 744 N/A 136 N/A 226 N/A 413

2 0.66 1.32 1.32 0.44 2.1 0.52 3.4

3 11.70 7.88 8.01 0.31 14.1 0.42 22.2

Sub3 1.70 0.24 1.58 0.34 2.8 0.49 5.3

4 5.00 0.32 4.73 0.47 7.5 0.41 8.7

5 1.40 0.35 1.38 0.45 2.2 0.44 2.8

6 0.18 0.43 0.43 0.47 0.5 0.55 1.1

7 0.35 0.37 0.83 0.47 1.3 0.54 2.0

8 0.31 0.37 0.70 0.47 1.1 0.60 1.9

Basin ID Area

(acres) C10

Q10

(cfs) C25

Q25

(cfs) C100

Q100

(cfs) 9 9.50 0.21 5.97 0.31 11.06 0.49 23.15

0.23 0.14

0.22 0.52 0.72 0.57 1.42

11 0.46 0.36 1.03 0.46 1.64 0.60 2.82

12 0.11 0.21 0.15 0.31 0.27 0.55 0.64

Additional information is included in Appendix B including basin maps, rational calculations, regression calculations, soil data and rainfall data.

Floodplain Impacts

The project is not located in an area of Federal Emergency Management Agency (FEMA) mapping therefore, there are no floodplains identified within the project.

Hydraulics

Existing Conditions

There are three locations where existing culverts cross CR23(A). There is one culvert near station 104+75, three at the low point near station 113+27 and one more located near station

119+12. There are three driveway culverts and one additional location at a field access where a

6-inch PVC has been installed. There are a combination of V and trapezoidal roadway ditches that run along the project. Ditches along the west side of CR23(A) drain along the road to the low point where it joins a main drainageway that flows to the west. Ditches along the east drain along and then away from the road into the main drainage that crosses at the low point of

CR23(A). West and east ditches drain from the south to the low point as well as from the north end of the Project to the low point. On the east two of the parallel culverts, 125 & 127, were recently constructed with the new parking lot. The third culvert, 101, drains under a field access near the beginning of the project on the east. The 6-inch PVC is located on the west near station 110+45. The low point is located near station 113+27. At this location there are three existing culverts.

Photos from the site visit show some of the existing culverts have crushed ends. All cross culverts are corrugated metal pipes (CMP) with projecting ends. All culverts are shallow with minimal cover. Appendix A includes photos of the existing conditions.

Table 5 summarizes the existing culverts and the hydraulic results. The scoping visit noted that roadway overtopping does occur. HW/D should be 1.5 or less and headwater elevation (HWEl) should be below the shoulder hinge point. Cross culverts should convey the 25-year peak flow.

Roadside ditch culverts will convey the 10-year peak flow. Culverts were analyzed using FHWA

HY8 software. Existing condition results are included in Appendix C. Driveway or cross culverts list the appropriate design storm based on criteria and the other column is blank.

Table 5 Existing Culverts

Culvert

ID

Approximate Roadway Station

Diameter (inches)

Material Q10

(cfs) Q25

(cfs)

Edge of Gravel

Elevation (feet)

Headwater Elevation

(feet)

HW/D

Outlet Velocity

(fps)

101 101+50R 18 RCP 1.3 - 2549.42 2547.42 0.4 3.2

105 104+75 24 CMP - 22.3 2548.08 2548.05 1.3 6.6

110 110+45L 6 PVC 1.4 - 2546.04 2546.03 2.4 4.1

112+45 112+76 113+27

CMP

CMP

CMP

- 226 2543.28 2543.38 2.7 7.6

119 119+12 12 CMP - 11.1 2550.59 2550.08 0.4 0.8

125 125+00R 18 RCP 1.2 - 2566.38 2564.82 0.3 7.5

127 127+00R 18 RCP 0.15 - 2575.73 2573.52 0.1 2.0

Roadside ditches are trapezoidal and follow the profile of the road to low points and ultimately drain to the west. Some locations have sedimentation and there is an area of a significant scour hole on the east side just off the edge of pavement near roadway station 103+50 Rt. A photo is included in the site visit photos in Appendix A.

Proposed Design

Culverts were analyzed for proposed conditions and compliance with new culvert design standards. The three cross culvert locations do not meet current criteria and will be replaced at the same location with a new configuration that complies with current standards. Due to site conditions, limited vertical profile and right of way (ROW) constraints variances to criteria are still required. In addition, multiple barrels will be required to meet HWEl and HW/D design standards and provide the minimum cover requirements. For new culverts the PDDM requires the HWEl shall be below the bottom of the aggregate base layer, HW/D of 1.5 or less and a minimum diameter of 24-inches. FHWA concrete pipe culvert installation standard detail 602-7 specifies a minimum cover of 12-inches and is defined from top of pipe to the subgrade for flexible pavements. The pavement section is 8-inches roadbed reconditioning, 7-inches of roadway aggregate and 4.5-inches of asphalt concrete pavement.

Culvert profiles have been lowered as much as possible to minimize ROW impacts. To fit a 24-inch minimum diameter pipe significant ditch grading would be required or vertical adjustment of the roadway profile. Vertical adjustment of that degree did not align with the scope, budget or

ROW for the project. Culverts were optimized as much a possible with the given constraints to meet criteria.

Table 6 lists the hydraulic analysis of the proposed cross culverts. The following variances are needed for proposed conditions. Proposed culverts 105 and 119 are 18-inch equivalent to meet cover requirements and minimize grading. This is less than the minimum diameter and will require a variance. Culvert 113+27 does exceed HW/D criteria but does meet the headwater elevation criteria. The road profile was adjusted but does not allow for a larger diameter culvert at this location. This is at the low point of the road. A variance for HW/D would be required for this culvert.

The DM recommends outlet velocity over 6 fps should consider outlet protection. All cross culverts will add flared end sections (FES) or headwalls (HW) and FHWA standard riprap aprons.

The parallel culverts that were recently installed, meet design criteria and will remain.

Table 6 Proposed Culvert Replacements

Culvert

ID

Roadway Station

Diameter (inches)

Material Q25

(cfs)

Bottom of Aggregate base layer Elevation

(feet)

Headwater Elevation

(feet)

HW/D

Outlet Velocity

(fps)

105 104+77 3- 23x14

(18 equiv)

HERCP 20.8 2547.4 2547.6 1.2 6.3

112+42 112+74 113+27

2-36 2-36

RCP

RCP

RCP

2544.9 2544.6 2544.4

2543.8 1.3 1.4 1.8

8.3 8.9 8.7

119 119+12 2 – 23x14 (18 equiv)

HERCP 11.5 2549.9 2550.7 1.0 7.1

Roadside ditches will be narrowed due to the roadway widening. Ditches at minimum should be reconditioned to ensure positive drainage and revegetated with adequate lining to prevent erosion. Roadside ditch capacity and permanent lining was evaluated for the 10-year peak flows using FHWA Hydraulic Toolbox. Ditches meeting design standards and do not require additional lining. Ditches were found to be stable with vegetation.

Tall grass is found in the existing ditches, 0.03 was used for manning’s n for capacity calculations. Sides slopes varied but were typically 4:1 or 3:1. Trapezoidal bottom width varies to a minimum of approximately three feet.

The following table lists the ditch sections that were evaluated along the project.

Ditch Section

Q10

(cfs)

Depth of Flow (feet)

Lining

Allow Shear Stress (lb/ft2)

Max Shear Stress (lb/ft2)

100-105 Lt 1.4 0.2 Vegetation 4.6 0.1

107-105 Lt 4.7 0.3 Vegetation 1.9 0.3

107-110 Lt 16.9 1.3 Vegetation 1.4 0.8

117-113 Rt 0.4 0.1 Vegetation 6.9 0.06

125-122 Rt 1.6 0.2 Vegetation 1.5 0.5

127-125 Rt 1.1 0.3 Vegetation 1.1 1.1

128-127 Rt 0.2 0.2 Vegetation 3.5 0.2

125-119 Lt 6.3 0.7 Vegetation 1.1 1.1

Channel stability was evaluated with hydraulic toolbox based on soil type, surface cover, longitudinal slope and 10-year flows. The project consists of loams and clays. The plasticity index was determined from NRCS Web Soil Survey to be 24 for Nunn-Beckton loams, 2 to 6 percent slopes. Based on the site parameters ditches were found to be stable and no additional lining is required. Vegetation will be re-established after construction. Interim conditions should include native seeding, soil retention blanket and fiber rolls for ditch check dams to protect from erosion during revegetation. Calculations are included in Appendix C.

Stormwater Control Measures

The limits of disturbance for the project are approximately 3.1 acres. The project’s construction stormwater discharges must include a general stormwater construction permit number

SDR100000 effective on April 1, 2018 from South Dakota Department of Agriculture and Natural

Resources (DANR) in conformance with the National Pollutant Discharge Elimination System

(NPDES). The contractor will be responsible for acquiring the permit.

No permanent water quality is required since the Project is located outside of either a Phase I or

II Municipal Separate Storm Sewer System (MS4) permit area. Phase I MS4s are entities with populations over 100,000. Phase II MS4s are areas of at least 50,000 or designated by the

Secretary as needing coverage.

Wetland impacts were not anticipated at project scoping. However, it was determined there are wetlands at the culvert outlets. Disturbance of wetlands does not require mitigation.

FHWA standard erosion and sediment control measures will be used. Velocity was evaluated at each culvert outlet and standard riprap aprons are included. Areas that are disturbed during construction will be re-established. Fiber rolls will be used as perimeter control, culvert inlet and outlet protection and in ditches.

Summary

The proposed drainage improvements for the project include culvert replacement and ditch reconditioning to meet CFLHD and local SDDOT criteria. Roadway widening and installation of larger diameter culverts were designed not to impact right-of-way (ROW). Two variances are required to accommodate the limitations of the site without adding work and cost to the project.

The minimum pipe diameter at culverts 105 and 119 and HW/D criteria for culvert 112 at station

113+27.

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References

• Design of Roadside Channels with Flexible Linings, Federal Highway Administration

(FLH), Hydraulic Engineering Circular (HEC) No. 15, Third Edition. September 2005.

• Detail Drawings: FP-14, Central Federal Lands Highway Division (CFLHD).

• Drainage Manual, South Dakota Department of Transportation (SDDOT). May 2022.

• GIS Web Map Gallery, State Highway Data, SDDOT. June 1, 2022.

• Highway Hydrology, Federal Highway Administration, Hydraulic Design Series No. 2

(HDS2), FHWA-NHI-02-001. 2002.

• NOAA Atlas 14 Point Precipitation Frequency Estimates, NOAA. May 24, 2022.

• Project Development and Design Manual (PDDM), Federal Lands Highway (FLH).

December 2012.

• Road Design Manual, South Dakota Department of Transportation (SDDOT). May 2022.

• Standard Drawings, Federal Lands Highway (FLH).

• Stormwater Permit for Construction Activities, South Dakota Department of Agriculture &

Natural Resources. April 1, 2018. Stormwater Construction (sd.gov)

• Web Soil Survey Hydrologic Soil Group – Jackson County Area, South Dakota, Northern

Part, NRCS. May 26, 2022.

Appendix A

Criteria Memo

Site Photos

CFLHD | SD FLAP CS23A(1)

Drainage Design Criteria Memo

Date: Monday, June 13, 2022

Project: SD FLAP CS23A(1) Delta-01 Access Road

To: Aaron Estep, CFLHD

From: Amy Finseth, HDR

Subject: Drainage Design Criteria Memo

Project Description Jackson County Road CS-23A provides the sole access to the Delta-1 Launch Control Facility, which is a part of the Minuteman Missile National Historic Site. The existing gravel roadway is deteriorated with washboards and potholes and cannot support or sustain continued or increased vehicular traffic by heavy recreational vehicles, campers, tour buses, and local heavy agricultural equipment.

The proposed project includes clearing and grubbing, rehabilitation, widening, and asphalt paving of the existing aggregate section of approximately 0.5 miles of Jackson County CS-23A.

The project limits are from the existing asphalt limits, approximately 900 feet north of the WB I-

90 ramp intersections, to the intersection just north of the Delta 1 visitor parking access. The proposed roadway will be 24-foot width with 11-foot lanes with 1-foot shoulders. MUTCD signing and striping will be installed, and drainage and erosion control improvements will be needed at select culverts to maintain the integrity of the proposed roadway and provide for positive flow.

This memo outlines the criteria for hydrologic and hydraulic (H&H) design based on the U.S.

Department of Transportation Federal Highway Administration (FHWA) Project Development and Design Manual (PDDM) and local criteria from South Dakota Department of Transportation

(SDDOT) Drainage Manual (DM). Jackson County does not have design criteria. Therefore, SDDOT was referenced for local criteria.

The scope of H&H includes preliminary analysis of existing conditions. Calculate peak discharges based on appropriate methods and evaluate six existing culverts. Evaluate proposed conditions and recommend rehabilitation, replacements and extensions as appropriate. Design proposed structures to meet the outlined criteria. Analyze roadside ditches for capacity and temporary /permanent linings.

The roadway classification is designated as low-standard road based on 48 ADT (<1500) and non-critical road designation.

Design Criteria Drainage design will include developing hydrology, culvert and roadside ditch analysis. Erosion and sediment control measures will also be recommended. The Stormwater Management Plan

(SWMP) will be developed by the contractor.

Drainage Criteria is outlined in Table 3 following the PDDM and DM for applicable design components of the project based on low-standard road. Tables 1 & 2 provide hydrologic information for the region to develop peak flow.

Hydrology Hydrology will be developed for local basins, up to 200 acres, using the rational method. Basins exceeding 200 acres will use rural regression equations from USGS and included in the DM, Chapter 7 Hydrology. South Dakota (SD) has seven hydrologic subregions. The project is located in sub-region C. The regression equations for sub-region C were developed for basins between 0.06 and 904 square miles (38-578,560 acres). Basins that fall within 38 and 200 acres will be evaluate by both methods. The 25-year regression equation standard error of estimate is

50%. Values will be provided in the drainage memo.

The DM provides intensity duration curves for each region of the state. The project falls between

Rapid City, Pierre and Winner. The National Oceanic and Atmospheric Administration (NOAA)

Precipitation Frequency Data Server was used to compare the data found for the site with the three locations and was within the range of the three regions. NOAA Atlas 14 point precipitation depths for the project are listed in Table 1 for the frequencies developed for the hydrologic and hydraulic analysis.

Table 1 NOAA Atlas 14, Point Precipitation Frequency Estimates, Rainfall Depth

Duration (minutes)

2-Year (inches)

10-Year (inches)

25-Year (inches)

100-Year (inches)

5 0.34 0.55 0.69 0.91

10 0.50 0.80 1.00 1.33

15 0.61 0.98 1.22 1.62

30 0.82 1.32 1.66 2.19

60 1.00 1.68 2.13 2.86

The DM, Figure 7.9-C includes the rural regression equations for each region. Subregion C equations for the frequencies used on the project are listed in Table 2.

Table 2 USGS Rural regression Equations for South Dakota, Subregion C

Recurrence Interval (years)

Equation

2 Q = 25 CA 0.569

10 Q = 125 CA 0.579

25 Q = 207 CA 0.573

100 Q = 379 CA 0.566

The project is in Jackson County between Wall and Kadoka just north of I-90 at CS-23A interchange. The project is not located in an area of Federal Emergency Management Agency

(FEMA) mapping therefore, there are no floodplains identified within the project.

Hydraulics Hydraulic criteria is summarized below for the specific design elements included in the scope of the project. The table was developed primarily based on the PDDM but compared with local criteria. Where specific local preferences or criteria was found in the DM that has been listed and is indicated by an asterisk in the table.

Table 3 H&H Criteria Summary

Design Feature PDDM Criteria

Peak Flow Methods Rational Method – up to 200 acres

Rural Regression Equations for areas > 200 acres Culverts

Capacity Design and Stability

Design: 25-yr (cross culverts)

10-yr (parallel culverts)

Check: 100-yr

Headwater

New culverts: less than the bottom of the roadway aggregate base layer

Existing: less than the shoulder hinge point

HW/D: 48” or smaller 1.5

WSEL limited by unacceptable hazards to human life or property

Minimum Size Cross-road culvert : 24” or equivalent

Parallel culvert : 18" or equivalent

Pipe Material

Minimum pipe classification

RCP: Class II, Metal 0.064"

50-year service life

Minimum and

Maximum Outlet Velocity

Minimum : 3 fps

Maximum : as determined by HEC22; matching existing channel velocities.

Outlet Protection

* Vo>6 fps consider erosion protection

Vo > 10 fps, consider gabion protection

Vo > 15 fps, consider energy dissipation

Roadside Ditches

Capacity Design

10-yr storm event

New: WSEL less than bottom of roadway aggregate base layer

Existing: WSEL less than shoulder hinge point

Stability Design

Permanent Lining: 10-year flood

Temporary lining: 2-year flood

Determined by permissible shear stress

*Slope Minimum: 0.5%

Slopes at absolute minimum of 0.2% should use a paved section

*Side Slopes 4:1 inslope – 3:1 maximum backslope

See Figure 1 for typical county road ditch section

*Depth 3.5 ft below elevation of the subgrade shoulder

*SDDOT Typical Channel Lining

(Listed in order of preference)

HEC-15

*Temporary: crimped straw (mulch), erosion control blanket, wood fiber mulch, bonded fiber matrix

*Permanent: vegetation (retardance Class B – see Figure 9.4-A of SDDOT

DM (Chapter 9, page 9-17)

*Indicates local preference/criteria in addition to the PDDM.

SDDOT Road Design Manal Chapter 7, Figure 7-3 provides typical ditch sections. Figure 1 is the typical county road ditch section included in that figure. Along the site there are both V and trapezoidal ditch sections. The project will attempt to maintain the existing ditch geometry or aim to attain a similar section shown in Figure 1 where feasible. But due to widening and right-of-way the section with a 10-foot bottom will not fit within the project limits and a V ditch will be proposed as the typical dich section.

Figure 1 Typical Ditch Section (SDDOT)

The following software or references will be used for the culvert and ditch hydraulics. FHWA software will be used for hydraulic analysis. Hydraulic Toolbox will be used to determine ditch capacity and temporary or permanent lining. HY8 will be used to determine culvert capacity.

Erosion Control Erosion and sediment control will use standard best management practices (BMPs) used by

FHWA. Anticipated BMPs include culvert inlet and outlet protection, check dams, fiber roll and rolled erosion control product.

References

• Drainage Manual, South Dakota Department of Transportation (SDDOT). May 2022.

• Highway Hydrology, Federal Highway Administration, Hydraulic Design Series No. 2

(HDS2), FHWA-NHI-02-001. 2002.

• NOAA Atlas 14 Point Precipitation Frequency Estimates, NOAA. May 24, 2022.

• Project Development and Design Manual (PDDM), Federal Lands Highway (FLH).

December 2012.

• Road Design Manual, South Dakota Department of Transportation (SDDOT). May 2022.

• Techniques for Estimating Peak-Flow Magnitude and Frequency Relations for South

Dakota Streams, Water-Resources Investigations Report 98-4055, U.S. Department of the Interior U.S. Geological Survey. 1998.

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APPENDIX A – SITE PHOTOS

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Appendix B

Hydrology

Hydrologic Soil Group—Jackson County Area, South Dakota, Northern Part (Delta1)

Natural Resources Conservation Service

Web Soil Survey National Cooperative Soil Survey

5/26/2022

260800 261400 262000 262600 263200 263800

260200 260800 261400 262000 262600 263200 263800

43° 54' 18'' N

1°

9'

'' W 43° 54' 18'' N

1°

6'

0'

' W

43° 50' 57'' N

1°

9'

'' W

43° 50' 57'' N

1°

6'

0'

' W

N

Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 14N WGS84 0 500 1000 2000 3000

Feet 0 250 500 1000 1500

Meters Map Scale: 1:17,300 if printed on B portrait (11" x 17") sheet.

AFINSETH

Rectangle

AFINSETH

Callout Project Location

MAP LEGEND MAP INFORMATION

Area of Interest (AOI) Area of Interest (AOI)

Soils Soil Rating Polygons

A

A/D

B

B/D

C

C/D

D

Not rated or not available

Soil Rating Lines A

A/D

B

B/D

C

C/D

D

Not rated or not available

Soil Rating Points A

A/D

B

B/D

C

C/D

D

Not rated or not available

Water Features Streams and Canals

Transportation Rails

Interstate Highways

US Routes

Major Roads

Local Roads

Background Aerial Photography

The soil surveys that comprise your AOI were mapped at 1:24,000.

Please rely on the bar scale on each map sheet for map measurements.

Source of Map: Natural Resources Conservation Service Web Soil Survey URL:

Coordinate System: Web Mercator (EPSG:3857)

Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required.

This product is generated from the USDA-NRCS certified data as of the version date(s) listed below.

Soil Survey Area: Jackson County Area, South Dakota, Northern Part Survey Area Data: Version 11, Sep 14, 2021

Soil map units are labeled (as space allows) for map scales 1:50,000 or larger.

Date(s) aerial images were photographed: Mar 29, 2021—Sep 22, 2021

The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident.

Hydrologic Soil Group—Jackson County Area, South Dakota, Northern Part (Delta1)

Natural Resources Conservation Service

Web Soil Survey National Cooperative Soil Survey

5/26/2022

Hydrologic Soil Group

Map unit symbol Map unit name Rating Acres in AOI Percent of AOI

Ar Arvada loam D 248.0 11.9%

As Arvada-Slickspots complex

D 24.6 1.2%

BcB Beckton loam, 2 to 6 percent slopes

C 48.1 2.3%

CbB Cactusflat-Weta complex, 1 to 6 percent slopes

C 143.3 6.9%

HsC Hisle-Slickspots complex, 0 to 9 percent slopes

D 13.8 0.7%

Ko Kolls clay D 53.5 2.6%

KyC Kyle clay, 6 to 9 percent slopes

D 13.6 0.7%

LcD Larvie-Conata clays, 6 to 15 percent slopes

D 11.0 0.5%

MoB Metre-Larvie clays, 2 to 6 percent slopes

D 0.8 0.0%

NuA Nunn loam, 0 to 3 percent slopes

C 78.7 3.8%

NuB Nunn loam, 3 to 6 percent slopes

C 566.5 27.3%

NuC Nunn loam, 6 to 9 percent slopes

C 255.9 12.3%

NwB Nunn-Beckton loams, 2 to 6 percent slopes

C 245.6 11.8%

PcB Pierre clay, 3 to 6 percent slopes

D 28.1 1.4%

PeC Pierre clay, 6 to 9 percent slopes

D 249.5 12.0%

PhB Pierre-Hisle complex, 1 to 6 percent slopes

D 43.2 2.1%

PsD Pierre-Samsil clays, 6 to 15 percent slopes

D 18.9 0.9%

W Water 10.5 0.5%

WeA Weta silt loam, 0 to 3 percent slopes

C 23.0 1.1%

Totals for Area of Interest 2,076.7 100.0%

Hydrologic Soil Group—Jackson County Area, South Dakota, Northern Part Delta1

Natural Resources Conservation Service

Web Soil Survey National Cooperative Soil Survey

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Description

Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms.

The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (A/D, B/D, and C/D). The groups are defined as follows:

Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission.

Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture.

These soils have a moderate rate of water transmission.

Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission.

Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission.

If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes.

Rating Options

Aggregation Method: Dominant Condition

Component Percent Cutoff: None Specified

Tie-break Rule: Higher

Hydrologic Soil Group—Jackson County Area, South Dakota, Northern Part Delta1

Natural Resources Conservation Service

Web Soil Survey National Cooperative Soil Survey

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Source: Esri, Maxar, Earthstar Geographics, and the GIS User Community

PATH: \\DEN-GISSRV1\GISDATA\DATA\SOUTH DAKOTA\JACKSONCOUNTY\SD FLAP TO15 DELTA\SD-FLAPDELTA.MXD - USER: AFINSETH - DATE: 10/2/2022

CFLHD SD FLAP TO15 DELTA01

OVERALL BASIN MAP

0 340 680 1,020 1,360 Feet

I

Basin ID

Area (acres)

Basin Label

11.7

5.0

1.4

9.5

LEGEND

ID

Area (acres)

Basin Label

Basin Boundary

Flow Arrows

Contour Note:

This map covers major offsite basins. Minor basins are shown on Basin Maps 1-3.

Begin Project

End Project

N00°44'50"E

.0

P O

B

N

0.7 ac

B2

101+18

Begin Project

CL CS-23AI-90

1.7 ac subB3

Legend

Basin Boundary

Existing Contours

Direction of Flow

Design Point

(square miles)

Area (acres) or

Basin ID

DP1

DP2

744 ac

B1

11.7 ac

B3 xx AC

B1

:2

P

M c to b e r

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DRAINAGE BASIN MAPS

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STATE PROJECT

NUMBER

SHEET

SD

SD FLAP CS23A(1)

DELTA-01 ACCESS ROAD

.1

P I

N

CL CS-23A

1.4 ac

B5

Culverts Sta 104+77

Culverts Sta 112+42

Culverts Sta 112+74

Culverts Sta 113+27

0.3 ac

B8

0.4 ac

B70.2 ac

B6

Legend

Basin Boundary

Existing Contours

Direction of Flow

Design Point

(square miles)

Area (acres) or

Basin ID

DP1

DP1

DP8DP3

DP7

DP5

744 ac

B1

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B1

5.0 ac

B4

:5

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DRAINAGE BASIN MAPS

DELTA-01 ACCESS ROAD

STATE PROJECT

NUMBER

SHEET

SD

J B

N

0.5 ac

B11

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B12

CL CS-23A

End Project 127+45

Culverts Sta 119+12

Legend

Basin Boundary

Existing Contours

Direction of Flow

Design Point

(square miles)

Area (acres) or

Basin ID

DP1

DP9

DP10

DP11

DP12

0.2 ac

B10

744 ac

B1

9.5 ac

B9 xx AC

B1

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DRAINAGE BASIN MAPS

DELTA-01 ACCESS ROAD

STATE PROJECT

NUMBER

SHEET

SD

Rational Method

Runoff Coefficients Project: SD FLAP 23A(1) Delta01 Computed: CB Date: 9/20/2022

Existing Hydrology Checked: AF Date: 9/22/2022

Sub-Basin Data

Basin ID Description

Total Area

(ac)

2 D/W Culvert STA 101+45R 0.66 0.24 0.29 0.34 0.44 0.52 C 22.7% 0.15 0.51

3 Cross Culvert STA 104+77 11.70 0.90 0.19 0.24 0.34 0.41 C 1.2% 0.14 11.56 sub3 Roadside Ditch STA 100-105L 1.70 0.25 0.19 0.24 0.34 0.49 C 17.1% 0.29 1.41

Roadside Ditch STA 107-105L/

Cross Culvert STA 104+77 5.00 3.04 0.32 0.37 0.47 0.41 C 1.6% 0.08 4.92

Roadside Ditch STA 107-110L/

6" PVC at field access 1.40 0.57 0.30 0.35 0.45 0.44 C 7.1% 0.10 1.30

6 Roadside Ditch STA 110-112R 0.18 0.27 0.32 0.37 0.47 0.55 C 27.8% 0.05 0.13

7 Roadside Ditch STA 117-113R 0.35 0.49 0.32 0.37 0.47 0.54 C 25.7% 0.09 0.26

8 Roadside Ditch STA 117-113L 0.31 0.54 0.32 0.37 0.47 0.60 C 35.5% 0.11 0.20

Roadside Ditch STA 128-119L/

Cross Culvert STA 119+12 9.50 0.16 0.16 0.21 0.31 0.49 C 15.6% 1.48 8.02

10 Roadside ditch 125-123R 0.23 0.14 0.37 0.14 0.52 0.57 C 30.4% 0.07 0.16

11 swale 127-125R to d/w culvert STA 125R 0.46 1.35 0.31 0.36 0.46 0.60 C 37.0% 0.17 0.29

Roadside ditch STA 128-127R/

Parking Lot d/w culvert 127R 0.11 0.01 0.16 0.21 0.31 0.55 C 27.3% 0.03 0.08

Type of Drainage Area

Streets:

Pavement

Meadows

Composite

C100

*C values determined from DM, Chapter 7 Hydrology, Table 7.13-A Runoff Coefficients for the Rational Equation

Composite

C25

Composite

C2

Composite

C5 Hydrologic Soils Group

Percent

Impervious

Area

Impervious (ac)

Area Pervious

(ac)

0.7-0.95

0.10-0.40

Composite

C10

Runoff Coefficient

SDDOT 7.13-A

Runoff Coefficients for the Rational Equation

Standard Form SF-1 . Time of Concentration

Project: SD FLAP 23A(1) Delta01 Computed: CB Date: 9/20/2022

Checked: AF Date: 9/22/2022

SUB-BASIN DATA INITIAL/OVERLAND FLOW TRAVEL TIME

(ti) (tt)

*see Tabl 3-3

Basin ID Description

Intercept

Coefficient (k)

2 D/W Culvert STA 101+45R 0.29 23 0.66 35 2558 2556 0.057 3 341 2556 2547 0.026 0.3 1.7 3.34 7 6.8

3 Cross Culvert STA 104+77 0.19 1 11.70 39 2562 2561 0.026 5 1456 2561 2546 0.010 0.3 1.1 22.83 28 28.0 sub3 Roadside Ditch STA 100-105L 0.19 17 1.70 61 2563 2562 0.016 9 828 2562 2546 0.019 0.4 1.9 7.37 16 16.2

Roadside Ditch STA 107-105L/

Cross Culvert STA 104+77 0.32 2 5.00 100 2556 2554 0.020 12 1084 2554 2546 0.007 0.3 0.9 20.08 32 32.2

Roadside Ditch STA 107-110L/

6" PVC at field access 0.30 7 1.40 100 2551 2550.5 0.005 21 488 2551 2545 0.011 0.3 1.1 7.32 28 28.5

6 Roadside Ditch STA 110-112R 0.32 28 0.18 18 2547 2546 0.056 2 220 2546 2540 0.027 0.3 1.7 2.12 4 5.0

7 Roadside Ditch STA 117-113R 0.32 26 0.35 19 2553.5 2553 0.026 3 319 2553 2540 0.041 0.3 2.1 2.51 5 5.4

8 Roadside Ditch STA 117-113L 0.32 35 0.31 18 2553.5 2553 0.028 3 382 2553 2541 0.031 0.3 1.8 3.63 6 6.3

Roadside Ditch STA 128-119L/

Cross Culvert STA 119+12 0.16 16 9.50 100 2582 2580 0.020 12 1246 2580 2549 0.025 0.3 1.6 13.30 25 25.5

10 Roadside ditch 125-123R 0.37 30 0.23 27 2565 2563 0.074 3 266 2563 2553 0.038 0.3 1.9 2.31 5 5.0

11 swale 127-125R to d/w culvert STA 125R 0.31 37 0.46 30 2576 2575.5 0.017 5 186 2576 2564 0.062 0.3 2.5 1.26 6 6.2

Roadside ditch STA 128-127R/

Parking Lot d/w culvert 127R 0.16 27 0.11 19 2575 2574.5 0.026 3 105 2575 2574 0.005 0.3 0.7 2.56 5 5.4

Notes: HEC-22 Table 3-3. Intercept Coefficients for Velocity vs Slope English Unit Conversion

1. Overland Flow, T = 0.42 / P2^0.5 (nL/√s)^0.8 (HEC2 (Section 2.5 / SDDOT, Equation 7.8) Land Cover/Flow Regime k

2. Travel Time, Tt = L/60V (SDDOT, Equation 7.8) Forest with heavy ground litter; hay meadow (overland flow) 0.076 0.11324

3. Velocity, V = 33kS^0.5 (SDDOT, Equation 7.8) Trash fallow or minimum tillage cultivation; contour or strip cropped; woodland (overland flow) 0.152 0.22648

4. Shallow Concentrated Flow Velocity, Vt = HEC22, Eqaution 3-4 V=KukSp^0.5 Short grass pasture (overland flow) 0.213 0.31737

5. k HEC22 Table 3-3 Cultivated straight row (overland flow) 0.274 0.40826

6. Minimum Tc = 10 minutes Nearly bare and untilled (overland flow); alluvial fans in western mountain regions 0.305 0.45445

Grassed waterway (shallow concentrated flow) 0.457 0.68093

Unpaved (shallow concentrated flow) 0.491 0.73159

Paved area (shallow concentrated flow); small upland gullies 0.619 0.92231

C5

Length

(ft)

Elevation

Start

Elevation

End

Slope

(ft/ft)

Percent

Impervious

FINAL Tc

(min)

Total

Area

(ac) ti

(min)

Length

(ft)

Elevation

Start

Elevation

End

So

(ft/ft) Velocity

Travel

Time Tt

(min) tc = ti + tt

(min)

Rational Analysis

Standard Form SF-2 . Storm Drainage System Design (Rational Method Procedure) Corridor / Design Package: SD FLAP 23A(1) Delta01 Computed: CB Date: 9/20/2022

Checked: AF Date: 9/22/2022

Design Storm: 10-yr

B A

S

IN

I D

A R

E A

A

C

R U

N O

F F

C O

E F

F t c

(M

IN

C .A

(A C

I

IN

H R

Q

(C

S

S U

M

C *A

(A C

I

(I N

H

R

Q

(C F

S

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13)

D/W Culvert STA 101+45R 2 2 0.66 0.34 6.79 0.22 5.96 1.32 roadside ditch to existing d/w culvert

Cross Culvert STA 104+77 3 3 11.70 0.24 28.01 2.84 2.82 8.01 ofsite to roadside ditch to Culvert Sta 104+77

Roadside Ditch STA 100-105L 3 sub3 1.70 0.24 16.23 0.41 3.82 1.58 sub area ditch flows

Roadside Ditch STA 107-105L/

Cross Culvert STA 104+77 3 4 5.00 0.37 32.23 1.83 2.58 4.73 32.23 5.09 2.58 13.13 offsite to roadside ditch to Culvert Sta 104+77

Roadside Ditch STA 107-110L/

6" PVC at field access 5 5 1.40 0.35 28.47 0.50 2.78 1.38 offsite from west to roadside ditch to existing d/w pvc

Roadside Ditch STA 110-112R 6 6 0.18 0.37 5.00 0.07 6.59 0.43 roadside ditch drains into B1

Roadside Ditch STA 117-113R 7 7 0.35 0.37 5.40 0.13 6.45 0.83 roadside ditch drains into B1

Roadside Ditch STA 117-113L 8 8 0.31 0.37 6.33 0.11 6.12 0.70 roadside ditch drains offsite to west

Roadside Ditch STA 128-119L/

Cross Culvert STA 119+12 9 9 9.50 0.21 25.45 1.97 3.03 5.97 offsite to roadside ditch to Culvert 119+12 to B1

Roadside ditch 125-123R 10 10 0.23 0.14 5.00 0.03 6.59 0.22 6.25 0.22 6.15 1.37 roadside ditch drains into B1 swale 127-125R to d/w culvert STA 125R 11 11 0.46 0.36 6.25 0.17 6.15 1.03 6.25 0.19 6.15 1.17 existing d/w culvert to B10

Roadside ditch STA 128-127R/

Parking Lot d/w culvert 127R 12 12 0.11 0.21 5.45 0.02 6.43 0.15 existing d/w culvert to B11

(1) Basin Description linked to C-Value Sheet (7) =Column 4 x Column 5

(2) Basin Design Point (8) Intensity from Noah 14 Atlas

(3) Enter the Basin Name from C Value Sheet (9) =Column 7 x Column 8

(4) Basin Area linked to C-Value Sheet (10) =Column 6 + Column 21

(5) Composite C linked to C-Value Sheet (11) Add the Basin Areas (7) to get the combined basin AC

(6) Time of Concentration linked to C-Value Sheet (12) =28.5*P/(10+Column 10)^0.786

(13) Sum of Qs

REMARKSLOCATION

D E

S

IG

N P

O

IN

T DIRECT RUNOFF TOTAL RUNOFF

Rational Analysis

Corridor / Design Package: SD FLAP 23A(1) Delta01 Computed: CB Date: 9/20/2022

Checked: AF Date: 9/22/2022

Design Storm: 25-yr

A R

E A

D

S

IG

(n a m e

A R

E A

A

C

R U

N O

F F

C O

E F

C .A

(A C

I

IN

H

S

S U

M

C *A

(A C

I

(I N

H

R

Q

(C F

S

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13)

D/W Culvert STA 101+45R 2 2 0.66 0.44 6.8 0.29 7.44 2.14 roadside ditch to existing d/w culvert

Cross Culvert STA 104+77 3 3 11.70 0.34 28.0 4.01 3.52 14.12 ofsite to roadside ditch to Culvert Sta

104+77

Roadside Ditch STA 100-105L 3 sub3 1.70 0.34 16.2 0.58 4.77 2.78 sub area ditch flows

Roadside Ditch STA 107-105L/

Cross Culvert STA 104+77 3 4 5.00 0.47 32.2 2.33 3.22 7.51 32.23 6.93 3.22 22.31 offsite to roadside ditch to Culvert Sta

104+77

Roadside Ditch STA 107-110L/

6" PVC at field access 5 5 1.40 0.45 28.5 0.64 3.47 2.21 offsite from west to roadside ditch to existing d/w pvc

Roadside Ditch STA 110-112R 6 6 0.18 0.47 5.0 0.08 6.02 0.51 roadside ditch drains into B1

Roadside Ditch STA 117-113R 7 7 0.35 0.47 5.4 0.16 8.05 1.32 roadside ditch drains into B1

Roadside Ditch STA 117-113L 8 8 0.31 0.47 6.3 0.14 7.64 1.11 roadside ditch drains offsite to west

Roadside Ditch STA 128-119L/

Cross Culvert STA 119+12 9 9 9.50 0.31 25.5 2.92 3.79 11.06 offsite to roadside ditch to Culvert 119+12 to B1

Roadside ditch 125-123R 10 10 0.23 0.52 5.0 0.12 6.02 0.72 6.25 0.37 7.68 2.82 roadside ditch drains into B1 swale 127-125R to d/w culvert STA 125R 11 11 0.46 0.46 6.2 0.21 7.68 1.64 6.25 0.25 7.68 1.90 existing d/w culvert to B10

Roadside ditch STA 128-127R/

Parking Lot d/w culvert 127R 12 12 0.11 0.31 5.4 0.03 8.03 0.27 existing d/w culvert to B11

(1) Basin Description linked to C-Value Sheet (7) =Column 4 x Column 5

(2) Basin Design Point (8) Intensity from Noah 14 Atlas

(3) Enter the Basin Name from C Value Sheet (9) =Column 7 x Column 8

(4) Basin Area linked to C-Value Sheet (10) =Column 6 + Column 21

(5) Composite C linked to C-Value Sheet (11) Add the Basin Areas (7) to get the combined basin AC

(6) Time of Concentration linked to C-Value Sheet (12) =28.5*P/(10+Column 10)^0.786

(13) Sum of Qs

REMARKSLOCATION

D E

S

IG

N P

O

IN

Corridor / Design Package: SD FLAP 23A(1) Delta01 Computed: CB Date: 9/20/2022

Checked: AF Date: 9/22/2022

Design Storm: 100-yr

A R

A

D

S

IG

(n a m e

A R

E A

A

C

R U

N O

F F

C O

E F

C .A

(A C

I

IN

H

S

S U

M

C *A

(A C

I

(I N

H

R

Q

(C F

S

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13)

D/W Culvert STA 101+45R 2 2 0.66 0.52 6.79 0.35 9.8 3.41 roadside ditch to existing d/w culvert

Cross Culvert STA 104+77 3 3 11.70 0.41 28.01 4.76 4.7 22.21 ofsite to roadside ditch to Culvert Sta 104+77

Roadside Ditch STA 100-105L 3 sub3 1.70 0.49 16.23 0.84 6.3 5.29 sub area ditch flows

Roadside Ditch STA 107-105L/

Cross Culvert STA 104+77 3 4 5.00 0.41 32.23 2.04 4.3 8.74 32.23 7.64 4.3 32.69 offsite to roadside ditch to Culvert Sta 104+77

Roadside Ditch STA 107-110L/

6" PVC at field access 5 5 1.40 0.44 28.47 0.62 4.6 2.83 offsite from west to roadside ditch to existing d/w pvc

Roadside Ditch STA 110-112R 6 6 0.18 0.55 5.00 0.10 10.9 1.08 roadside ditch drains into B1

Roadside Ditch STA 117-113R 7 7 0.35 0.54 5.40 0.19 10.7 2.02 roadside ditch drains into B1

Roadside Ditch STA 117-113L 8 8 0.31 0.60 6.33 0.18 10.1 1.87 roadside ditch drains offsite to west

Roadside Ditch STA 128-119L/

Cross Culvert STA 119+12 9 9 9.50 0.49 25.45 4.61 5.0 23.15 offsite to roadside ditch to Culvert 119+12 to B1

Roadside ditch 125-123R 10 10 0.23 0.57 5.00 0.13 10.9 1.42 6.25…