9 - CAR853313A Design Report 10-29-2024.pdf

Iowa Department of Agriculture and Land Stewardship RE: Carroll County Breakpoint Nutrient Reduction Wetland JEO Project No. 210779.18 JEO Consulting Group, Inc. Page 1 of 7

Breakpoint Nutrient Reduction Wetland

Carroll County, Iowa

Design Report

Project No. 210779.18

Prepared For:

Iowa Department of Agriculture and Land Stewardship (IDALS)

Project Design Team:

PM: Jake T. Miriovsky, PE

Project Engineer: Juan A. Arellanes, EI

Project Engineer: Nathan J. Blankman, EI

Prepared: October 29, 2024

JEO Project No. 210779.18 JEO Consulting Group, Inc. Page 2 of 7

PROJECT SUMMARY

The purpose of this project is to construct a traditional breakpoint nutrient reduction wetland located several miles East of Lanesboro in Carroll County, Iowa. The construction of this dam will result in the establishment of a water quality wetland that treats water prior to entrance to Purgatory Creek.

Target criteria and design guidelines used for the wetland establishment are in accordance with Iowa NRCS Construction Practice Standard Pond (CPS 378), Grade Stabilization Structure (CPS 410), and Constructed Wetland (CPS 656).

Pond is accomplished by the following:

• Storing water for erosion control and flow detention.

• Improving water quality.

Grade Stabilization Structure is accomplished by the following.

• Reducing erosion.

• Improving water quality.

Constructed Wetland is accomplished by the following:

• Improving water quality of storm water runoff, tile drainage outflow and other waterflows.

The intent is to collect water from the watershed in a nutrient reduction wetland with the purpose of improving water quality. The wetland (located in the E ½ of the NE1/4 Section 13, T85, R33W) will include construction of an earth dam. A steel sheet pile outlet will serve to control the depth of the normal pool within the resulting wetland and discharge downstream to Purgatory Creek to the West.

A water control structure/CMP drawdown structure with a filter diaphragm is proposed to allow draining of the wetland for maintenance. A wave bench and stilling basin are to be constructed on the earth dam. The proposed pool fill borrow is intended to expand the normal pool area and decrease the overall depth of the wetland.

EXISTING CONDITIONS

The wetland has a surface and subsurface drainage watershed of 317 acres. The drainage area was delineated using statewide LiDAR. Delineated drainage areas for the wetland are generally undeveloped aside from use as farm ground. Adjacent homes and other infrastructure are built on higher elevation than the wetland area. Typically, around the 1175’ elevation for nearby homes.

The wetland is located at a pinch point of two natural drainage paths draining from the north and from the east. The bottom elevation of the proposed wetland is at approximately 1100’. The normal pool area of the wetland is 1107’ which provides a maximum depth of 7’ in the wetland.

The wetland area consists primarily of Coland clay loam and Wadena loam which are poorly drained hydric soils and well drained non hydric soils respectively.

DESIGN ASSUMPTIONS & PROCEDURES

Wetland Sizing To achieve targets for water quality, a permanent pool elevation was identified to provide a pool area between 0.5% and 2% of the total contributing watershed area. The pool area is graded so less than 50% of the pool area will be three (3) feet in depth. An easement area containing the

JEO Project No. 210779.18 JEO Consulting Group, Inc. Page 3 of 7

100-year storm bounce is proposed based on hydraulic routings for a 100yr-24hr design storm.

Several principal spillway outlet configurations were evaluated to decrease drop height. Due to site restriction, no separate auxiliary spillway is proposed, in consideration with CPS 378-Pond requirements, the capacity of the principal spillway has been sized to pass the 50 yr-24hr design storm with at least 2 feet of freeboard.

Utilizing the watershed boundary, a composite hydrologic soil group classification as established for the watershed. The longest flow path and grade(s) were established utilizing LiDAR elevations and AutoCAD software. Initial peak flows (Qn) and time of concentration (Tc) values were assessed using NOAA’s Atlas-14, NRCS MSE3 rainfall distributions, and TR-55 methodology.

HydroCAD was the software used to provide peak flows inflows and routings. A summary of the flow comparison is provided in the following table:

Qn RECURRENCE INTERVAL

25yr 50yr 100yr

StreamStats (317 AC) 323 CFS 423 CFS 535 CFS

TR-55 Analysis (HydroCAD) 388 CFS 599 CFS 820 CFS

Basin Flow/Storm Characteristics:

DRAINAGE AREA: 317 Acres TC: 1.17 Hours Longest Flow Path: 1.09 Miles

10yr-24hr: 4.47 Inches 25yr-24hr: 5.59 Inches 50yr-24hr: 6.56 Inches 100yr-24hr: 7.63 Inches

Hydrologic Soil Group & RCN HSG: “B” – RCN = - 69 – 104 Acres HSG: “C” – RCN = - 83 - 91 Acres HSG: “D” – RCN = - 86 – 122 Acres

Weighted Average RCN=80

Hydraulic Design & Routings Stage Storage for the project is evaluated at elevations above the proposed permanent pool area (1107.0). The design includes grading to expand the pool area and provide fill material for the deep pool. This grading is planned to expand the permanent pool and is tentatively planned based on soils, but is subjective to change based on soil suitability. Fill material from the earthen dam is planned to be taken from a borrow site near Purgatory Creek.

A steel sheet pile trapezoidal weir was selected as the principal spillway. The bottom width was iteratively adjusted until the 50-year storm could be passed with 2 feet of freeboard. The 100-year event was modelled to evaluate the outlet structure and easement area. The location and placement of the weir was selected to reduce the weir drop height to less than 10 feet and minimize impacts to farming operations, subsequently no auxiliary spillway is proposed.

Flow Statistics 25yr Peak Outflow: 379 CFS 25yr Peak Water Elevation: 1108.88 25yr Time to Peak: 13.06 HR

50yr Peak Outflow: 563 CFS 50yr Peak Water Elevation: 1109.41 50yr Time to Peak: 13.34 HR

JEO Project No. 210779.18 JEO Consulting Group, Inc. Page 4 of 7

100yr Peak Outflow: 778 CFS 100yr Peak Water Elevation: 1109.93 100yr Time to Peak: 13.20 HR

Principal Spillway Bottom Width: 40 FT Bottom (Crest) Elevation: 1107.0 Sideslopes: 3H:1V Top Elevation: 1111.5

Stilling Basin Length: 47 FT Width: 37 FT

Sideslopes: 3H:1V Floor Elevation: 1098.0 Crest Elevation: 1099.0

Auxiliary Spillway

NONE

Earthen Dam Dam Length: 307 FT Dam Height: 13.5 FT Top Width: 12 FT Sideslopes: 4H:1V Wavebench Width: 20 FT Wavebench Slope: 10H:1V

Wetland Stage Storage*

Wetland Storage (Post Construction)

Elevation (FEET) Cumulative Storage Volume (AC-FT)

1100 0.00

1101 0.09

1102 0.25

1103 0.49

1104 0.81

1105 1.46

1106 2.80

1107 (Normal Pool) 4.70

1108 6.96

1109 9.59

1110 12.62

1111 16.081

1111.5 (Top of Dam) 17.98 *Stage storage information was calculated using topographic data supplemented with USGS 2020 LiDAR.

The earthen dam is proposed to be overbuilt to an elevation of 1112.25 with a twelve (12) foot top width to account for any potential soil settlement. In consideration of soil information, the earthen dam is proposed with a larger wave berm and 4:1 slopes to provide additional seepage and slope protection.

The wetland will be equipped with a drawdown structure to allow vegetation to be established and as a way to provide dry access for future maintenance activities. The drawdown structure is proposed as a 24 inch diameter slotted riser with a 15 inch diameter corrugated metal pipe (CMP) conduit through the embankment. The conduit will be fitted with a sand filter diaphragm to protect against piping and seepage along the conduit.

The stilling basin was designed using guidance from the Iowa NRCS Standard Drawing 1411 (IA- 1411) “Steel Sheet Pile Drop Structure.” The standard drawing stilling basin dimensions are listed for weir drop heights of 2 feet to 6 feet. The design of the stilling basin for this project was based on a weir drop height of 9 feet. The dimensioning for the stilling basin on this project was

JEO Project No. 210779.18 JEO Consulting Group, Inc. Page 5 of 7 extrapolated for the weir drop height of 9 feet. The dimensioning of the stilling basin on this project is 47 feet long by 37 feet wide. The normal stilling basin pool is 50 feet long by 43 feet wide and 1 foot deep.

Sediment Storage Sediment storage was evaluated using spreadsheet forms developed by the NRCS, available soil information on the USGS Web Soil Survey, aerial photography, and field survey information.

Below the normal pool elevation, there is 4.70 acre-feet of storage available. Included in the appendices is the prepared sediment life analysis. Consideration is given to tile infrastructure, depressional areas, highly erodible areas, and land slope for determining areas subject to sheet and rill erosion.

SURVEY

Survey was performed by JEO Consulting Group, Inc. on March 21st and 22nd of 2023. The weather was 30°F and sunny on March 21st and 30°F and partly cloudy on March 22nd. A Utility One Call Design Locate was completed on March 10th, 2023. The source of property information on the project is from surveyed pins, Carroll County Recorder plats, deeds, and easements. A final easement plat was recorded with Carroll and Greene counties for portions of the easement in the respective counties.

SOILS & GEOTECHNICAL INFORMATION

A site review was done in tandem with a desktop review of the USGS Web Soil Survey to identify and avoid potential sources of granular materials for the structure borrow and wetland suitability.

Borrow areas identified for dam fill are designated based on topography that lends itself to the project and soil series. Geotechnical exploration was completed by Certified Testing Services, Inc.

(CTS) on August 23rd, 2023 and November 8, 2023. Soils around the proposed pool area were generally clayey sands depth of 10’. A borrow site was identified adjacent to Purgatory Creek which consisted primarily of lean clay with sand. The reports determined that material available at the borrow site would be suitable for use as embankment fill. The design intends on all embankment and core trench fill materials to be sourced from the borrow site and any other material excavated from the dam footprint or pool areas to be used as fill in the borrow site to replace the material removed for use as embankment fill.

DOWNSTREAM IMPACTS

The proposed wetland is directly downstream from a confluence of two subdivisions of a larger watershed. Directly downstream of the proposed wetland is farm ground and Purgatory Creek.

The drainage path to Purgatory Creek is approximately 800’. From visual investigation there are no dwellings immediately downstream of the proposed wetland. Downstream of Purgatory Creek, there is one dwelling located on 130th Street, approximately one mile. There is also a bridge located over Purgatory Creek on 130th Street. There are no expected impacts to any dwellings or structures due to the construction of the wetland.

PERMITTING

Environmental impacts review and permitting are to be completed by IDALS. There are currently no anticipated impacts with the construction of the dam and wetland. Mitigation measures are currently not anticipated with the construction of the dam and wetland.

JEO Project No. 210779.18 JEO Consulting Group, Inc. Page 6 of 7

DESIGN DRAWINGS & APPENDICES

Included in the plans are stage storage and discharge tables for the wetland and summary tables for spillways. Included in the appendices is the Opinion of Probably Construction Cost, Atlas 14 tabular rainfall information, Civil 3D cut/fill report, structure discharge summary files, and HydroCAD routing summaries.

REFERENCES, SOFTWARES & CALCULATORS

Multiple references, softwares, and calculators were used for the design and development of these wetlands. Listed below is a list of these that were used for key design components.

Hydrology & Hydraulics NOAA Atlas 14 .................................................................. Precipitation Frequency

Web Soil Survey ................................................................. Soil Properties & Elevations

Esri ArcGIS ArcPro .............................................................. Tc and Curve Numbers

HydroCAD 10.20-3a 2023 ................................................. Outflow Discharge Curves

............................................................................................ Inflows and Outflows

............................................................................................ Reservoir Routing

Autodesk AutoCAD 2023 .............................................. Stage Storage

USGS National Map .......................................................... 2020 Iowa LiDAR Data

Sincerely, Juan A. Arellanes, PE

Water Resources Engineer

Enc: Appendices

JEO Project No. 210779.18 JEO Consulting Group, Inc. Page 7 of 7

APPENDICES

1. Drainage Area Delineations 1 page(s)

2. NOAA Atlas 14 Precipitation Data 2 page(s)

3. Carroll Wetland H&H Modeling Report 13 page(s)

4. Stage Storage Data 1 Page(s)

5. Curve Number Calculations 1 Page(s)

6. Historical Imagery of Area 4 page(s)

7. AutoCAD Cut/Fill Report 2 Page(s)

8. Hydrologic Soil groups 5 Page(s)

9. Color Shaded Elevation Map 1 Page(s)

Drainage Area Delineation

Point precipitation frequency estimates (inches)

NOAA Atlas 14 Volume 8 Version 2

Data type: Precipitation depth

Time series type: Partial duration

Project area: Midwestern States

Location name (ESRI Maps): Churdan Iowa USA

Station Name: -

Latitude: 42.1780°

Longitude: -94.6260°

Elevation (USGS): None None

PRECIPITATION FREQUENCY ESTIMATES

by duration for ARI (years):1 2 5 10 25 50 100 200 500 1000

5-min: 0.381 0.446 0.561 0.665 0.82 0.949 1.09 1.24 1.45 1.62

10-min: 0.558 0.653 0.821 0.973 1.2 1.39 1.59 1.81 2.12 2.37

15-min: 0.681 0.797 1 1.19 1.46 1.7 1.94 2.21 2.58 2.89

30-min: 0.981 1.15 1.45 1.72 2.13 2.48 2.84 3.24 3.8 4.26

60-min: 1.26 1.5 1.93 2.33 2.94 3.44 3.99 4.58 5.42 6.1

2-hr: 1.53 1.85 2.42 2.94 3.74 4.41 5.13 5.92 7.04 7.95

3-hr: 1.68 2.05 2.71 3.32 4.25 5.04 5.9 6.83 8.16 9.25

6-hr: 1.97 2.38 3.13 3.84 4.93 5.87 6.89 8.01 9.62 10.9

12-hr: 2.3 2.7 3.45 4.16 5.26 6.21 7.25 8.4 10 11.4

24-hr: 2.66 3.04 3.77 4.47 5.59 6.56 7.63 8.83 10.6 12

2-day: 3 3.44 4.26 5.02 6.19 7.19 8.28 9.48 11.2 12.6

3-day: 3.26 3.75 4.63 5.44 6.66 7.69 8.8 10 11.7 13.1

4-day: 3.5 4.02 4.95 5.79 7.05 8.1 9.22 10.4 12.1 13.5

7-day: 4.15 4.75 5.78 6.69 8.03 9.13 10.3 11.5 13.2 14.6

10-day: 4.74 5.4 6.52 7.49 8.9 10 11.2 12.5 14.2 15.6

20-day: 6.46 7.29 8.68 9.84 11.5 12.8 14 15.4 17.2 18.5

30-day: 7.92 8.92 10.5 11.9 13.7 15.1 16.4 17.8 19.6 20.9

45-day: 9.82 11 13 14.5 16.5 18 19.5 20.9 22.6 23.9

60-day: 11.5 12.9 15.1 16.8 19 20.6 22.1 23.5 25.2 26.3

PRECIPITATION FREQUENCY ESTIMATES AT UPPER BOUND OF 90% CONFIDENCE INTERVAL

by duration for ARI (years):1 2 5 10 25 50 100 200 500 1000

5-min: 0.472 0.552 0.696 0.826 1.06 1.23 1.43 1.66 1.97 2.21

10-min: 0.691 0.809 1.02 1.21 1.55 1.8 2.1 2.43 2.89 3.24

15-min: 0.843 0.986 1.24 1.48 1.89 2.2 2.56 2.96 3.52 3.95

30-min: 1.21 1.42 1.8 2.14 2.75 3.21 3.75 4.35 5.19 5.83

60-min: 1.55 1.86 2.4 2.9 3.8 4.47 5.26 6.15 7.41 8.36

2-hr: 1.87 2.26 2.97 3.62 4.79 5.67 6.71 7.87 9.53 10.8

3-hr: 2.04 2.49 3.3 4.05 5.42 6.46 7.67 9.04 11 12.5

6-hr: 2.37 2.86 3.77 4.63 6.23 7.44 8.88 10.5 12.8 14.6

12-hr: 2.73 3.21 4.11 4.96 6.57 7.79 9.25 10.9 13.3 15.1

24-hr: 3.12 3.57 4.43 5.27 6.91 8.14 9.64 11.4 13.8 15.7

2-day: 3.47 3.99 4.94 5.84 7.52 8.79 10.3 12 14.5 16.4

3-day: 3.75 4.31 5.34 6.29 8.01 9.32 10.9 12.6 15 16.9

4-day: 4 4.61 5.68 6.67 8.42 9.75 11.3 13.1 15.5 17.4

7-day: 4.7 5.38 6.56 7.62 9.46 10.9 12.5 14.3 16.7 18.6

NOAA Atlas 14 Precipitation Data

10-day: 5.34 6.08 7.35 8.48 10.4 11.9 13.5 15.4 17.9 19.8

20-day: 7.17 8.1 9.66 11 13.2 14.8 16.6 18.6 21.3 23.3

30-day: 8.73 9.84 11.7 13.2 15.5 17.3 19.3 21.4 24.1 26.1

45-day: 10.7 12.1 14.2 16 18.6 20.5 22.6 24.8 27.5 29.6

60-day: 12.5 14 16.5 18.4 21.2 23.3 25.5 27.7 30.4 32.5

PRECIPITATION FREQUENCY ESTIMATES AT LOWER BOUND OF 90% CONFIDENCE INTERVAL

by duration for ARI (years):1 2 5 10 25 50 100 200 500 1000

5-min: 0.317 0.371 0.464 0.546 0.654 0.736 0.811 0.879 0.985 1.07

10-min: 0.464 0.543 0.68 0.8 0.958 1.08 1.19 1.29 1.44 1.56

15-min: 0.566 0.662 0.829 0.976 1.17 1.31 1.45 1.57 1.76 1.9

30-min: 0.816 0.955 1.2 1.42 1.7 1.92 2.12 2.31 2.59 2.81

60-min: 1.05 1.25 1.6 1.92 2.35 2.67 2.98 3.26 3.7 4.02

2-hr: 1.29 1.55 2.02 2.44 3.02 3.46 3.87 4.26 4.85 5.3

3-hr: 1.42 1.72 2.27 2.77 3.46 3.98 4.48 4.95 5.67 6.21

6-hr: 1.68 2.02 2.65 3.23 4.06 4.68 5.29 5.88 6.76 7.43

12-hr: 1.98 2.32 2.95 3.54 4.38 5.01 5.63 6.23 7.15 7.84

24-hr: 2.31 2.64 3.25 3.84 4.7 5.35 6 6.64 7.61 8.35

2-day: 2.62 3.01 3.71 4.34 5.24 5.92 6.57 7.2 8.16 8.89

3-day: 2.87 3.3 4.06 4.74 5.66 6.36 7.01 7.64 8.58 9.3

4-day: 3.09 3.55 4.36 5.07 6.01 6.72 7.38 8 8.94 9.65

7-day: 3.7 4.22 5.12 5.9 6.88 7.63 8.3 8.91 9.84 10.5

10-day: 4.25 4.83 5.81 6.64 7.66 8.43 9.11 9.72 10.6 11.3

20-day: 5.84 6.58 7.81 8.81 9.94 10.8 11.5 12.1 13 13.7

30-day: 7.2 8.1 9.54 10.7 11.9 12.8 13.5 14.1 14.9 15.5

45-day: 8.98 10.1 11.8 13.1 14.4 15.4 16.1 16.6 17.3 17.8

60-day: 10.5 11.8 13.8 15.3 16.6 17.7 18.3 18.7 19.3 19.8

Date/time (GMT): Mon Apr 3 18:53:30 2023 pyRunTime: 0.0378217697144

Carroll Breakpoint Wetland Printed 8/2/2024Prepared by JEO Consulting Group

Page 1HydroCAD® 10.20-2b s/n 05639 © 2021 HydroCAD Software Solutions LLC

Rainfall Events Listing (selected events)

Event# Event

Name

Storm Type Curve Mode Duration

(hours)

B/B Depth

(inches)

AMC

1 2yr MSE 24-hr 3 Default 24.00 1 3.04 2

2 10yr MSE 24-hr 3 Default 24.00 1 4.47 2

3 25yr MSE 24-hr 3 Default 24.00 1 5.59 2

4 50yr MSE 24-hr 3 Default 24.00 1 6.56 2

5 100yr MSE 24-hr 3 Default 24.00 1 7.63 2

Carroll Wetland H & H Modelling Report

Carroll Breakpoint Wetland

Page 2HydroCAD® 10.20-2b s/n 05639 © 2021 HydroCAD Software Solutions LLC

Pipe Listing (selected nodes)

Line# Node

Number

In-Invert

(feet)

Out-Invert

(feet)

Length

(feet)

Slope

(ft/ft) n Width

(inches)

Diam/Height

(inches)

Inside-Fill

(inches)

1 5P 1,101.00 1,100.00 90.0 0.0111 0.025 0.0 15.0 0.0

2 5P 1,102.00 1,101.00 110.0 0.0091 0.025 0.0 15.0 0.0

MSE 24-hr 3 2yr Rainfall=3.04"Carroll Breakpoint Wetland

Page 3HydroCAD® 10.20-2b s/n 05639 © 2021 HydroCAD Software Solutions LLC

Summary for Pond 5P: Proposed Breakpoint Wetland

Inflow Area = 317.588 ac, 0.00% Impervious, Inflow Depth = 1.28" for 2yr event Inflow = 157.07 cfs @ 13.12 hrs, Volume= 33.878 af Outflow = 144.46 cfs @ 13.38 hrs, Volume= 29.173 af, Atten= 8%, Lag= 15.6 min Primary = 144.36 cfs @ 13.38 hrs, Volume= 29.172 af Secondary = 0.10 cfs @ 13.38 hrs, Volume= 0.002 af

Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.05 hrs Peak Elev= 1,108.02' @ 13.38 hrs Storage= 7.028 af

Plug-Flow detention time= 99.5 min calculated for 29.173 af (86% of inflow) Center-of-Mass det. time= 41.5 min ( 943.4 - 901.9 )

Volume Invert Avail.Storage Storage Description

#1 1,100.00' 17.983 af Custom Stage Data Listed below

Elevation Cum.Store (feet) (acre-feet)

1,100.00 0.000 1,101.00 0.086 1,102.00 0.248 1,103.00 0.488 1,104.00 0.805 1,105.00 1.463 1,106.00 2.801 1,107.00 4.705 1,108.00 6.963 1,109.00 9.586 1,110.00 12.615 1,111.00 16.081 1,111.50 17.983

Device Routing Invert Outlet Devices

#1 Primary 1,107.00' Custom Weir/Orifice, Cv= 2.62 (C= 3.28) Head (feet) 0.00 1.00 2.00 3.00 4.00 5.00 5.50 Width (feet) 40.00 46.00 52.00 58.00 64.00 70.00 73.00

#2 Secondary 1,101.00' 15.0" Round CMP_Round 15" L= 90.0' CMP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 1,101.00' / 1,100.00' S= 0.0111 '/' Cc= 0.900 n= 0.025 Corrugated metal, Flow Area= 1.23 sf

#3 Device 2 1,108.00' Custom Weir/Orifice, Cv= 2.62 (C= 3.28) Head (feet) 0.00 7.00 Width (feet) 4.00 4.00

#4 Device 3 1,102.00' 15.0" Round CMP_Round 15" L= 110.0' CMP, projecting, no headwall, Ke= 0.900 Inlet / Outlet Invert= 1,102.00' / 1,101.00' S= 0.0091 '/' Cc= 0.900 n= 0.025 Corrugated metal, Flow Area= 1.23 sf

MSE 24-hr 3 2yr Rainfall=3.04"Carroll Breakpoint Wetland

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Primary OutFlow Max=144.10 cfs @ 13.38 hrs HW=1,108.02' (Free Discharge) 1=Custom Weir/Orifice (Weir Controls 144.10 cfs @ 3.27 fps)

Secondary OutFlow Max=0.05 cfs @ 13.38 hrs HW=1,108.02' (Free Discharge) 2=CMP_Round 15" (Passes 0.05 cfs of 8.42 cfs potential flow)

3=Custom Weir/Orifice (Weir Controls 0.05 cfs @ 0.51 fps) 4=CMP_Round 15" (Passes 0.05 cfs of 0.45 cfs potential flow)

Pond 5P: Proposed Breakpoint Wetland

Inflow Outflow Primary Secondary

Hydrograph

Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420

F lo w

(c fs

Inflow Area=317.588 ac

Peak Elev=1,108.02'

Storage=7.028 af

157.07 cfs

144.46 cfs144.36 cfs

0.10 cfs

MSE 24-hr 3 10yr Rainfall=4.47"Carroll Breakpoint Wetland

Page 5HydroCAD® 10.20-2b s/n 05639 © 2021 HydroCAD Software Solutions LLC

Summary for Pond 5P: Proposed Breakpoint Wetland

Inflow Area = 317.588 ac, 0.00% Impervious, Inflow Depth = 2.44" for 10yr event Inflow = 292.01 cfs @ 12.98 hrs, Volume= 64.470 af Outflow = 280.91 cfs @ 13.13 hrs, Volume= 59.765 af, Atten= 4%, Lag= 8.7 min Primary = 278.73 cfs @ 13.13 hrs, Volume= 59.589 af Secondary = 2.18 cfs @ 13.13 hrs, Volume= 0.176 af

Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.05 hrs Peak Elev= 1,108.56' @ 13.13 hrs Storage= 8.428 af

Plug-Flow detention time= 61.7 min calculated for 59.724 af (93% of inflow) Center-of-Mass det. time= 27.3 min ( 924.3 - 897.0 )

Volume Invert Avail.Storage Storage Description

#1 1,100.00' 17.983 af Custom Stage Data Listed below

Elevation Cum.Store (feet) (acre-feet)

1,100.00 0.000 1,101.00 0.086 1,102.00 0.248 1,103.00 0.488 1,104.00 0.805 1,105.00 1.463 1,106.00 2.801 1,107.00 4.705 1,108.00 6.963 1,109.00 9.586 1,110.00 12.615 1,111.00 16.081 1,111.50 17.983

Device Routing Invert Outlet Devices

#1 Primary 1,107.00' Custom Weir/Orifice, Cv= 2.62 (C= 3.28) Head (feet) 0.00 1.00 2.00 3.00 4.00 5.00 5.50 Width (feet) 40.00 46.00 52.00 58.00 64.00 70.00 73.00

#2 Secondary 1,101.00' 15.0" Round CMP_Round 15" L= 90.0' CMP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 1,101.00' / 1,100.00' S= 0.0111 '/' Cc= 0.900 n= 0.025 Corrugated metal, Flow Area= 1.23 sf

#3 Device 2 1,108.00' Custom Weir/Orifice, Cv= 2.62 (C= 3.28) Head (feet) 0.00 7.00 Width (feet) 4.00 4.00

#4 Device 3 1,102.00' 15.0" Round CMP_Round 15" L= 110.0' CMP, projecting, no headwall, Ke= 0.900

MSE 24-hr 3 10yr Rainfall=4.47"Carroll Breakpoint Wetland

Page 6HydroCAD® 10.20-2b s/n 05639 © 2021 HydroCAD Software Solutions LLC

Primary OutFlow Max=278.35 cfs @ 13.13 hrs HW=1,108.56' (Free Discharge) 1=Custom Weir/Orifice (Weir Controls 278.35 cfs @ 4.00 fps)

Secondary OutFlow Max=2.18 cfs @ 13.13 hrs HW=1,108.56' (Free Discharge) 2=CMP_Round 15" (Passes 2.18 cfs of 8.75 cfs potential flow)

3=Custom Weir/Orifice (Passes 2.18 cfs of 5.45 cfs potential flow) 4=CMP_Round 15" (Outlet Controls 2.18 cfs @ 1.78 fps)

Pond 5P: Proposed Breakpoint Wetland

Inflow Outflow Primary Secondary

Hydrograph

Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420

F

Inflow Area=317.588 ac

Peak Elev=1,108.56'

Storage=8.428 af

292.01 cfs

280.91 cfs278.73 cfs

2.18 cfs

MSE 24-hr 3 25yr Rainfall=5.59"Carroll Breakpoint Wetland

Page 7HydroCAD® 10.20-2b s/n 05639 © 2021 HydroCAD Software Solutions LLC

Summary for Pond 5P: Proposed Breakpoint Wetland

Inflow Area = 317.588 ac, 0.00% Impervious, Inflow Depth = 3.41" for 25yr event Inflow = 387.74 cfs @ 12.95 hrs, Volume= 90.339 af Outflow = 379.15 cfs @ 13.06 hrs, Volume= 85.634 af, Atten= 2%, Lag= 6.7 min Primary = 376.42 cfs @ 13.06 hrs, Volume= 85.306 af Secondary = 2.74 cfs @ 13.06 hrs, Volume= 0.328 af

Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.05 hrs Peak Elev= 1,108.88' @ 13.06 hrs Storage= 9.275 af

Plug-Flow detention time= 49.0 min calculated for 85.575 af (95% of inflow) Center-of-Mass det. time= 23.1 min ( 917.6 - 894.6 )

Volume Invert Avail.Storage Storage Description

#1 1,100.00' 17.983 af Custom Stage Data Listed below

Elevation Cum.Store (feet) (acre-feet)

1,100.00 0.000 1,101.00 0.086 1,102.00 0.248 1,103.00 0.488 1,104.00 0.805 1,105.00 1.463 1,106.00 2.801 1,107.00 4.705 1,108.00 6.963 1,109.00 9.586 1,110.00 12.615 1,111.00 16.081 1,111.50 17.983

Device Routing Invert Outlet Devices

#1 Primary 1,107.00' Custom Weir/Orifice, Cv= 2.62 (C= 3.28) Head (feet) 0.00 1.00 2.00 3.00 4.00 5.00 5.50 Width (feet) 40.00 46.00 52.00 58.00 64.00 70.00 73.00

#2 Secondary 1,101.00' 15.0" Round CMP_Round 15" L= 90.0' CMP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 1,101.00' / 1,100.00' S= 0.0111 '/' Cc= 0.900 n= 0.025 Corrugated metal, Flow Area= 1.23 sf

#3 Device 2 1,108.00' Custom Weir/Orifice, Cv= 2.62 (C= 3.28) Head (feet) 0.00 7.00 Width (feet) 4.00 4.00

#4 Device 3 1,102.00' 15.0" Round CMP_Round 15" L= 110.0' CMP, projecting, no headwall, Ke= 0.900

MSE 24-hr 3 25yr Rainfall=5.59"Carroll Breakpoint Wetland

Page 8HydroCAD® 10.20-2b s/n 05639 © 2021 HydroCAD Software Solutions LLC

Primary OutFlow Max=375.95 cfs @ 13.06 hrs HW=1,108.88' (Free Discharge) 1=Custom Weir/Orifice (Weir Controls 375.95 cfs @ 4.38 fps)

Secondary OutFlow Max=2.74 cfs @ 13.06 hrs HW=1,108.88' (Free Discharge) 2=CMP_Round 15" (Passes 2.74 cfs of 8.94 cfs potential flow)

3=Custom Weir/Orifice (Passes 2.74 cfs of 10.82 cfs potential flow) 4=CMP_Round 15" (Outlet Controls 2.74 cfs @ 2.23 fps)

Pond 5P: Proposed Breakpoint Wetland

Inflow Outflow Primary Secondary

Hydrograph

Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420

F

Inflow Area=317.588 ac

Peak Elev=1,108.88'

Storage=9.275 af

387.74 cfs

379.15 cfs376.42 cfs

2.74 cfs

MSE 24-hr 3 50yr Rainfall=6.56"Carroll Breakpoint Wetland

Page 9HydroCAD® 10.20-2b s/n 05639 © 2021 HydroCAD Software Solutions LLC

Summary for Pond 5P: Proposed Breakpoint Wetland

Inflow Area = 317.588 ac, 0.00% Impervious, Inflow Depth = 4.29" for 50yr event Inflow = 598.92 cfs @ 13.24 hrs, Volume= 113.541 af Outflow = 562.98 cfs @ 13.34 hrs, Volume= 108.836 af, Atten= 6%, Lag= 5.7 min Primary = 559.52 cfs @ 13.34 hrs, Volume= 108.392 af Secondary = 3.46 cfs @ 13.34 hrs, Volume= 0.444 af

Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.05 hrs Peak Elev= 1,109.41' @ 13.34 hrs Storage= 10.814 af

Plug-Flow detention time= 42.2 min calculated for 108.761 af (96% of inflow) Center-of-Mass det. time= 20.5 min ( 906.6 - 886.1 )

Volume Invert Avail.Storage Storage Description

#1 1,100.00' 17.983 af Custom Stage Data Listed below

Elevation Cum.Store (feet) (acre-feet)

1,100.00 0.000 1,101.00 0.086 1,102.00 0.248 1,103.00 0.488 1,104.00 0.805 1,105.00 1.463 1,106.00 2.801 1,107.00 4.705 1,108.00 6.963 1,109.00 9.586 1,110.00 12.615 1,111.00 16.081 1,111.50 17.983

Device Routing Invert Outlet Devices

#1 Primary 1,107.00' Custom Weir/Orifice, Cv= 2.62 (C= 3.28) Head (feet) 0.00 1.00 2.00 3.00 4.00 5.00 5.50 Width (feet) 40.00 46.00 52.00 58.00 64.00 70.00 73.00

#2 Secondary 1,101.00' 15.0" Round CMP_Round 15" L= 90.0' CMP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 1,101.00' / 1,100.00' S= 0.0111 '/' Cc= 0.900 n= 0.025 Corrugated metal, Flow Area= 1.23 sf

#3 Device 2 1,108.00' Custom Weir/Orifice, Cv= 2.62 (C= 3.28) Head (feet) 0.00 7.00 Width (feet) 4.00 4.00

#4 Device 3 1,102.00' 15.0" Round CMP_Round 15" L= 110.0' CMP, projecting, no headwall, Ke= 0.900

MSE 24-hr 3 50yr Rainfall=6.56"Carroll Breakpoint Wetland

Page 10HydroCAD® 10.20-2b s/n 05639 © 2021 HydroCAD Software Solutions LLC

Primary OutFlow Max=557.92 cfs @ 13.34 hrs HW=1,109.40' (Free Discharge) 1=Custom Weir/Orifice (Weir Controls 557.92 cfs @ 4.92 fps)

Secondary OutFlow Max=3.46 cfs @ 13.34 hrs HW=1,109.40' (Free Discharge) 2=CMP_Round 15" (Passes 3.46 cfs of 9.24 cfs potential flow)

3=Custom Weir/Orifice (Passes 3.46 cfs of 21.74 cfs potential flow) 4=CMP_Round 15" (Outlet Controls 3.46 cfs @ 2.82 fps)

Pond 5P: Proposed Breakpoint Wetland

Inflow Outflow Primary Secondary

Hydrograph

Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420

F

Inflow Area=317.588 ac

Peak Elev=1,109.41'

Storage=10.814 af

598.92 cfs

562.98 cfs559.52 cfs

3.46 cfs

MSE 24-hr 3 100yr Rainfall=7.63"Carroll Breakpoint Wetland

Page 11HydroCAD® 10.20-2b s/n 05639 © 2021 HydroCAD Software Solutions LLC

Summary for Pond 5P: Proposed Breakpoint Wetland

Inflow Area = 317.588 ac, 0.00% Impervious, Inflow Depth = 5.28" for 100yr event Inflow = 819.64 cfs @ 13.09 hrs, Volume= 139.713 af Outflow = 777.52 cfs @ 13.20 hrs, Volume= 135.008 af, Atten= 5%, Lag= 6.6 min Primary = 773.47 cfs @ 13.20 hrs, Volume= 134.456 af Secondary = 4.06 cfs @ 13.20 hrs, Volume= 0.552 af

Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.05 hrs Peak Elev= 1,109.93' @ 13.20 hrs Storage= 12.409 af

Plug-Flow detention time= 37.0 min calculated for 134.914 af (97% of inflow) Center-of-Mass det. time= 18.8 min ( 897.3 - 878.5 )

Volume Invert Avail.Storage Storage Description

#1 1,100.00' 17.983 af Custom Stage Data Listed below

Elevation Cum.Store (feet) (acre-feet)

1,100.00 0.000 1,101.00 0.086 1,102.00 0.248 1,103.00 0.488 1,104.00 0.805 1,105.00 1.463 1,106.00 2.801 1,107.00 4.705 1,108.00 6.963 1,109.00 9.586 1,110.00 12.615 1,111.00 16.081 1,111.50 17.983

Device Routing Invert Outlet Devices

#1 Primary 1,107.00' Custom Weir/Orifice, Cv= 2.62 (C= 3.28) Head (feet) 0.00 1.00 2.00 3.00 4.00 5.00 5.50 Width (feet) 40.00 46.00 52.00 58.00 64.00 70.00 73.00

#2 Secondary 1,101.00' 15.0" Round CMP_Round 15" L= 90.0' CMP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 1,101.00' / 1,100.00' S= 0.0111 '/' Cc= 0.900 n= 0.025 Corrugated metal, Flow Area= 1.23 sf

#3 Device 2 1,108.00' Custom Weir/Orifice, Cv= 2.62 (C= 3.28) Head (feet) 0.00 7.00 Width (feet) 4.00 4.00

#4 Device 3 1,102.00' 15.0" Round CMP_Round 15" L= 110.0' CMP, projecting, no headwall, Ke= 0.900

MSE 24-hr 3 100yr Rainfall=7.63"Carroll Breakpoint Wetland

Page 12HydroCAD® 10.20-2b s/n 05639 © 2021 HydroCAD Software Solutions LLC

Primary OutFlow Max=772.81 cfs @ 13.20 hrs HW=1,109.93' (Free Discharge) 1=Custom Weir/Orifice (Weir Controls 772.81 cfs @ 5.40 fps)

Secondary OutFlow Max=4.06 cfs @ 13.20 hrs HW=1,109.93' (Free Discharge) 2=CMP_Round 15" (Passes 4.06 cfs of 9.53 cfs potential flow)

3=Custom Weir/Orifice (Passes 4.06 cfs of 35.14 cfs potential flow) 4=CMP_Round 15" (Outlet Controls 4.06 cfs @ 3.30 fps)

Pond 5P: Proposed Breakpoint Wetland

Inflow Outflow Primary Secondary

Hydrograph

Time (hours) 727068666462605856545250484644424038363432302826242220181614121086420

F

Inflow Area=317.588 ac

Peak Elev=1,109.93'

Storage=12.409 af

819.64 cfs

777.52 cfs773.47 cfs

4.06 cfs

Multi-Event TablesCarroll Breakpoint Wetland

Page 13HydroCAD® 10.20-2b s/n 05639 © 2021 HydroCAD Software Solutions LLC

Events for Pond 5P: Proposed Breakpoint Wetland

Event Inflow

(cfs)

Outflow

(cfs)

Primary

(cfs)

Secondary

(cfs)

Elevation

(feet)

Storage

(acre-feet)

2yr 157.07 144.46 144.36 0.10 1,108.02 7.028

10yr 292.01 280.91 278.73 2.18 1,108.56 8.428

25yr 387.74 379.15 376.42 2.74 1,108.88 9.275

50yr 598.92 562.98 559.52 3.46 1,109.41 10.814

100yr 819.64 777.52 773.47 4.06 1,109.93 12.409

Stage Storage Calculations

Elevation Depth Incremental Area (sf) Area (sf) Area (AC) Volume (cf) Volume (acre feet) Cum. Volume (cf) Cum. Volume (acre feet)

1100.00 0.00 2326.02 2326.02 0.05 0.00 0.00 0.00 0.00

1101.00 1.00 2867.97 5193.99 0.12 3760.01 0.09 3760.01 0.09

1102.00 2.00 3729.55 8923.54 0.20 7058.77 0.16 10818.77 0.25

1103.00 3.00 3009.10 11932.64 0.27 10428.09 0.24 21246.86 0.49

1104.00 4.00 3789.35 15721.99 0.36 13827.32 0.32 35074.18 0.81

1105.00 5.00 25835.70 41557.69 0.95 28639.84 0.66 63714.02 1.46

1106.00 6.00 33473.17 75030.86 1.72 58294.28 1.34 122008.29 2.80

1107.00 7.00 15793.75 90824.61 2.09 82927.74 1.90 204936.03 4.70 NWL

1108.00 8.00 15105.34 105929.95 2.43 98377.28 2.26 303313.31 6.96

1109.00 9.00 16668.77 122598.72 2.81 114264.34 2.62 417577.64 9.59

1110.00 10.00 18664.06 141262.78 3.24 131930.75 3.03 549508.39 12.61

1111.00 11.00 19439.28 160702.06 3.69 150982.42 3.47 700490.81 16.08

1111.50 11.50 9903.62 170605.68 3.76 82826.94 1.90 783317.75 17.98 T.O.D.

CONTOUR ELEVATION

(FT)

CONTOUR AREA (AC)

CUMULATIVE

VOLUME, AVG.

END (AC-FT)

1100 0.05 0.00

1101 0.12 0.09

1102 0.20 0.25

1103 0.27 0.49

1104 0.36 0.81

1105 0.95 1.46

1106 1.72 2.80

1107 2.09 4.70

1108 2.43 6.96

1109 2.81 9.59

1110 3.24 12.61

1111 3.69 16.08

1111.5 3.76 17.98

Stage Storage Calculations jarellanes Snapshot

Cover Description Map Unit Hydrologic Soil Group Area CN Area*CN

Straight Row Crop 55 C/D 42.39591 89 3773.236

Straight Row Crop 108 B 12.81188 78 999.3263

Straight Row Crop 108C2 B 2.03618 78 158.822

Brush - brush-weed-grass mixture with brush the major element - Fair Condition

108 B 3.255257 56 182.2944

Brush - brush-weed-grass mixture with brush the major element - Fair Condition

108C2 B 5.180647 56 290.1163

Meadow 135 C/D 6.436455 71 456.9883

Straight Row Crop 138B C 41.76601 85 3550.111

Meadow 138B C 1.067355 71 75.78223

Straight Row Crop Contoured & Terraced 203 B/D 3.886283 81 314.7889

Straight Row Crop 203 B/D 5.083678 89 452.4473

Straight Row Crop L62G B 0.301791 78 23.53967

Straight Row Crop 107 C/D 30.81387 89 2742.434

Meadow 107 C/D 3.814096 78 297.4994

Straight Row Crop 138B2 C 26.77585 85 2275.947

Straight Row Crop 138C B 1.621947 78 126.5118

Meadow 138C B 1.789922 58 103.8155

Farmsteads - buildings, lanes, driveways, and surrounding lots

138C B 1.492792 74 110.4666

Straight Row Crop 138C2 B 18.39553 78 1434.852

Meadow 138C2 B 2.505326 58 145.3089

Farmsteads - buildings, lanes, driveways, and surrounding lots

138C2 B 2.04736 74 151.5046

Meadow 138D2 B 9.894812 58 573.8991

Straight Row Crop 507 C/D 14.90721 89 1326.742

Meadow 585B C/D 1.650402 78 128.7313

Straight Row Crop Contoured & Terraced 638C2 B 11.88923 70 832.2463

Straight Row Crop Contoured & Terraced 638D2 B 5.562649 70 389.3854

Straight Row Crop L62E2 B 1.645902 78 128.3804

Straight Row Crop L138B B 4.929006 78 384.4625

Straight Row Crop L138C2 B 2.057564 78 160.49

Meadow L138B B 2.030073 58 117.7443

Meadow L138C2 B 10.29731 58 597.2442

Straight Row Crop Contoured & Terraced 55 C/D 28.75675 81 2329.297

Straight Row Crop Contoured & Terraced 138B C 4.756141 78 370.979

Straight Row Crop Contoured & Terraced 138B2 C 17.05794 78 1330.52

Straight Row Crop Contoured & Terraced 138C2 B 4.138659 70 289.7062

Water W 1.112133

Totals 334.1639

CN Weighted Average HSG B HSG C HSG D

79.67831592 CN 69.3093 83.16631 85.82666

Acre 103.8838 91.4233 137.7447

Curve Number Calculations

1960s Orthophotos

1990s Orthophotos

2007-2010 Spring Orthophotos

2016-2018 Spring Orthophotos

Hydrologic Soil Group—Carroll County, Iowa, and Greene County, Iowa (210779)

Natural Resources Conservation Service

Web Soil Survey National Cooperative Soil Survey

4/3/2023

364900 365100 365300 365500 365700 365900 366100 366300 366500 366700 366900 367100 367300

364700 364900 365100 365300 365500 365700 365900 366100 366300 366500 366700 366900 367100 367300

42° 11' 24'' N

8'

8' ' W

42° 11' 24'' N

6'

1' ' W

42° 10' 28'' N

8'

8' ' W

42° 10' 28'' N

6'

1' ' W

N

Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 15N WGS84 0 500 1000 2000 3000

Feet 0 150 300 600 900

Meters Map Scale: 1:12,200 if printed on A landscape (11" x 8.5") sheet.

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 1:15,800.

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: Carroll County, Iowa Survey Area Data: Version 27, Sep 2, 2022

Soil Survey Area: Greene County, Iowa Survey Area Data: Version 28, Sep 2, 2022

Your area of interest (AOI) includes more than one soil survey area. These survey areas may have been mapped at different scales, with a different land use in mind, at different times, or at different levels of detail. This may result in map unit symbols, soil properties, and interpretations that do not completely agree across soil survey area boundaries.

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

Date(s) aerial images were photographed: Sep 5, 2021—Oct 14, 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—Carroll County, Iowa, and Greene County, Iowa (210779)

Natural Resources Conservation Service

Web Soil Survey National Cooperative Soil Survey

4/3/2023

Hydrologic Soil Group

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

55 Nicollet clay loam, 1 to 3 percent slopes

C/D 0.1 0.0%

108 Wadena loam, 0 to 2 percent slopes

B 12.8 3.8%

108C2 Wadena loam, 6 to 12 percent slopes, moderately eroded

B 7.2 2.1%

135 Coland clay loam, 0 to 2 percent slopes, occasionally flooded

C/D 1.6 0.5%

138B Clarion loam, 2 to 6 percent slopes

C 0.0 0.0%

203 Cylinder loam, 0 to 2 percent slopes

B/D 0.4 0.1%

L62E2 Storden loam, Bemis moraine, 10 to 22 percent slopes, moderately eroded

B 1.4 0.4%

L62G Belview loam, Bemis moraine, 22 to 40 percent slopes

B 0.3 0.1%

Subtotals for Soil Survey Area 23.9 7.1%

Totals for Area of Interest 338.9 100.0%

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

55 Nicollet clay loam, 1 to 3 percent slopes

C/D 71.6 21.1%

107 Webster clay loam, 0 to 2 percent slopes

C/D 34.8 10.3%

108 Wadena loam, 0 to 2 percent slopes

B 4.0 1.2%

135 Coland clay loam, 0 to 2 percent slopes, occasionally flooded

C/D 4.9 1.5%

138B Clarion loam, 2 to 6 percent slopes

C 50.6 14.9%

138B2 Clarion loam, 2 to 6 percent slopes, moderately eroded

C 45.0 13.3%

138C Clarion loam, 6 to 10 percent slopes

B 5.0 1.5%

138C2 Clarion loam, 6 to 10 percent slopes, moderately eroded

B 35.8 10.6%

Hydrologic Soil Group—Carroll County, Iowa, and Greene County, Iowa 210779

Natural Resources Conservation Service

Web Soil Survey National Cooperative Soil Survey

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

138D2 Clarion loam, 9 to 14 percent slopes, moderately eroded

B 9.4 2.8%

203 Cylinder loam, 0 to 2 percent slopes

B/D 8.8 2.6%

507 Canisteo clay loam, 0 to 2 percent slopes

C/D 14.9 4.4%

585B Coland-Spillville complex, 1 to 5 percent slopes

C/D 1.7 0.5%

638C2 Clarion-Storden complex, 6 to 10 percent slopes, moderately eroded

B 12.1 3.6%

638D2 Omsrud-Storden complex, 10 to 16 percent slopes, moderately eroded

B 5.6 1.7%

L62E2 Storden loam, Bemis moraine, 10 to 22 percent slopes, moderately eroded

B 0.2 0.1%

L138B Clarion loam, Bemis moraine, 2 to 6 percent slopes

B 7.0 2.1%

L138C2 Clarion loam, Bemis moraine, 6 to 10 percent slopes, moderately eroded

B 2.4 0.7%

W Water 1.2 0.3%

Subtotals for Soil Survey Area 315.0 92.9%

Totals for Area of Interest 338.9 100.0%

Hydrologic Soil Group—Carroll County, Iowa, and Greene County, Iowa 210779

Natural Resources Conservation Service

Web Soil Survey National Cooperative Soil Survey

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—Carroll County, Iowa, and Greene County, Iowa 210779

Natural Resources Conservation Service

Web Soil Survey National Cooperative Soil Survey

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