03_Exhibit B_30% Stormwater Report_Granite Street.pdf

GRANITE STREET 30%

DESIGN

Prepared for: Town of Frisco, CO.

Prepared by: Janine White, PE Anthony Lamping, EIT

Toole Design Group 1801 Broadway Suite 1204 Denver, CO

Stormwater Memo

October 2023

Frisco, CO

GRANITE STREET 30% DESIGN STORMWATER MEMO | F INAL

TOOLE DESIGN | 1

CONTENTS

1. Introduction 2

2. Project Overview 2

3. Project Area Delineation and Analysis 3

4. Criteria for Calculations 4

Runoff Coefficient 4 Rainfall Intensity 5 Calculations 5

Conclusions 6 Appendix A: Graphics for Existing and Proposed Surface Cover 7 Appendix B: Rational Method Calculations for Drainage Basins 8 Appendix C: NRCS Soil Report 9 Appendix D: Frisco Drainage Study 10

Tables

Table 1: 1-Hour and 6-Hour Storm Rainfall Depth in inches 5 Table 2: Comparison of 5-year peak flows between existing and post-construction condition 6 Table 3: Comparison of 100-year peak flows between existing and post-construction condition 6

Figures

Figure 1: Project Area Map 2 Figure 2: Values from Table 7.5 from CDDM 4 Figure 3: Table 7.6 from CDDM for calculating Runoff coefficients 4 Figure 4: Equation 5-1 from USDCM for calculating rainfall intensity 5

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1. INTRODUCTION

This purpose of this stormwater memo is to document and demonstrate the drainage impacts resulting from the Granite Street 30% Design project in the town of Frisco, CO. This memo quantifies the difference in peak runoff flow rate resulting from changes proposed by the project. The results of this analysis will help influence infrastructure design for this project in future design phases.

2. PROJECT OVERVIEW

The Granite Street 30% Design Project (Project) is located along Granite Street between S Madison Ave to the west and Summit Blvd to the east. The project is entirely within town of Frisco right-of-way.

Figure 1: Project Area Map

The project proposes the installation of sidewalk and a two-way separated bicycle path along the north and south sides of Granite Street respectively, to eliminate existing infrastructure gaps and improve pedestrian and bicycle connectivity through one of the major east-west corridors within the town of Frisco. In addition, curb extensions are proposed at each intersection to reduce crossing distance for all directions of pedestrian/bicycle travel and to provide a protected space for formalized on-street parking on Granite Street. To accompany these hardscape features, the vehicular travel way will be fully repaved and formally delineated via striping, while pedestrian/bicycle crossings are added to reinforce intersection visibility and crossing priority at intersections within the project area. The proposed surface design is described below, but a graphical representation can also be found in Appendix A.

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From S Madison Ave to 3rd Ave and from 6th Ave to Summit Blvd, the project proposes a 6’ sidewalk with 4’ amenity zone, curb, and gutter and 20’ curb extensions at each intersection, extending into Granite Street to accommodate NW facing angled parking on the north side of the street. A valley gutter extends between the gutter pans of the curb extensions, and will carry surface runoff directly within this channel. The vehicular travel section of Granite Street is divided into 12’ eastbound and westbound travel lanes. The south side of Granite Street is comprised of curb and gutter, an 8’ amenity zone, and a 10’ two-way separated bicycle path.

From 3rd Ave to 4th Ave, the project proposes a 6’ sidewalk, 4’ amenity zone, and curb and gutter on the north side directly abutting the westbound travel lane. The vehicle travel section remains consistent with 12’ eastbound and westbound travel lanes. The south side of Granite Street includes a 10’ two-way separated bicycle path, 8’ amenity zone, and 20’ curb extensions to accommodate SE facing angled parking, along with a valley gutter between curb extensions like the previous section.

From 4th to 6th Ave, the project proposes a 6’ sidewalk, 4’ amenity zone, and curb and gutter on the north side, directly abutting the westbound travel lane, like the previous section. The 12’ eastbound and westbound travel lanes also remain consistent. The south side of Granite Street consists of the same 10’ two-way, separated bicycle path, 8’ amenity zone, along with curb and gutter. However, this section includes 9’ curb extensions to accommodate protected parallel parking along the south curb line, along with associated valley gutters.

This project includes a preliminary horizontal layout of a stormwater drainage system for Granite Street.

Stormwater inlets are placed near the eastern end of each block, on both the north and south curb lines due to the crowning of Granite Street at the centerline. These structures pick up drainage from their respective basins and flow into a proposed stormwater main, which conveys the stormwater east. The proposed stormwater main then ties into the existing stormwater system on the north side of Granite Street, between 7th Ave and Summit Blvd.

The existing downstream pipe is a 48-inch HDPE and outfalls east of Summit Blvd. The Town previously performed a drainage study for the existing stormwater system in Main Street and the Granite Street Alley, which is provided in Appendix D. Sizing and analysis of the proposed system is not included during this phase of the project but will be required during a future phase of design to confirm proposed pipe sizes and capacity of existing downstream pipes. The preliminary horizontal layout also includes an underground water quality structure which will need to be sized appropriately during future design phases.

3. PROJECT AREA DELINEATION AND

ANALYSIS

For this analysis, we set the project area to be consistent between existing and proposed conditions to tabulate difference in runoff flow rate on a block-by-block basis. The project area is defined by the right-of-way boundaries north/south of Granite Street and east/west of the side streets, as well as the limits of work for project work not adjacent to a right of way line. The entirety of the project area is further divided by block at the mid-point between the right-of-way of the side streets. For the purposes of this analysis, each block is its own basin, and all runoff is assumed to flow to the same location. A graphic of the project area breakdown and existing and proposed surface cover can be found in Appendix A. The tabulation of the existing/proposed surface area by surface type and runoff calculations can be found in Appendix B.

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4. CRITERIA FOR CALCULATIONS

The following resources were used to determine appropriate guidance for calculating impacts to drainage within the project area. The calculations derived from these manuals are meant to compare the change in peak flows between the existing and post-construction condition.

• CDOT Drainage Design Manual (CDDM)

• Mile High Flood District Urban Storm Drainage Criteria Manual, Volume 1 (USDCM)

The calculation to determine the peak flow for each basin is the Rational Method

𝑸𝑸 = 𝑪𝑪𝑪𝑪𝑪𝑪

Where Q is peak flow in cubic feet per second, C is a runoff coefficient, I is rainfall intensity in inches per hour, and A is area in acres.

RUNOFF COEFFICIENT

The runoff coefficient for the project area is determined using Tables 7.5 and 7.6 on page 7-18 of the CDDM.

Table 7.5 shows the percent impervious for each type of ground cover, and is used to compile a composite C value based on the percentage of each type of ground cover within a given drainage basin. Table 7.6 shows the runoff coefficient equations used to determine the composite runoff coefficient based on the NRCS soil group of the project area. The relevant values from Table 7.5, and the entirety of Table 7.6 of the CDDM are provided in Figures 2 and 3 shown below. The NRCS soil group data for the project area was obtained from this link, and the results are provided in Appendix C.

Land Use or Surface Characteristics Percentage Imperviousness Paved 100% Drive and walks 90% Gravel (Packed) 40% Lawns, Sandy Soil 2%

Figure 2: Values from Table 7.5 from CDDM

Figure 3: Table 7.6 from CDDM for calculating runoff coefficients https://www.codot.gov/business/hydraulics/drainage-design-manual/chapter7_hydrology.pdf https://mhfd.org/wp-content/uploads/2019/12/USDCM_Volume_1_August_2018.pdf https://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx

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RAINFALL INTENSITY

Rainfall Intensity is determined via Equation 5-1 on page 5-9 of the USDCM. This equation is also provided below.

Figure 4: Equation 5-1 from USDCM for calculating rainfall intensity

The 1-hour point rainfall depth is obtained from NOAA Atlas 14 for Frisco, CO, and is shown in the table below.

Storm Event 1-Hour Storm 6-Hour Storm 2-Year 0.505 0.799 5-Year 0.658 0.968 10-Year 0.802 1.13 25-Year 1.02 1.39 50-Year 1.22 1.61 100-Year 1.42 1.85

Table 1: 1-Hour and 6-Hour Storm Rainfall Depth in inches

CALCULATIONS

Using the figures above to determine the runoff coefficient and rainfall intensity, and the assumptions shown below, the peak flow for each drainage basin can be computed using the rational for both the existing and post-construction condition. The results are shown in Appendix B.

Assumptions NCRS Soil Group: B (Determined from NRCS Soil Map) Storm duration: 1 hour or 60 minutes (Conservative Assumption for Duration) Storm Event: 100-year (Value for Major Storm Drain System from Table 7.2 of CDOT Drainage Design Manual) Roadway Surface: Paved, 100% (From Table 7.5 above) Driveway/Pedestrian: Drive and Walks, 90% (From Table 7.5 above) Gravel: Gravel (Packed), 40% (From Table 7.5 above) Pervious Surface: Lawns, Sandy Soil, 2% (From Table 7.5 above) https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_map_cont.html

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CONCLUSIONS

The following table shows the change in flow for each drainage basin between the existing and post construction condition for both the 5-year and 100-year storm events.

5-Year

Drainage Basin Existing 5-Year Peak Flow (cfs)

Post-Construction 5- Year Peak Flow (cfs)

Difference in 5-Year Peak Flow (cfs)

Difference in 5-Year Peak Flow (%)

Madison to 1st 0.29 0.38 0.08 28.4% 1st to 2nd 0.31 0.38 0.07 22.0% 2nd to 3rd 0.32 0.38 0.06 17.4% 3rd to 4th 0.39 0.40 0.01 2.3% 4th to 5th 0.35 0.36 0.01 2.8% 5th to 6th 0.32 0.36 0.04 12.0% 6th to 7th 0.33 0.38 0.05 14.9% 7th to Summit 0.36 0.31 -0.05 -12.7%

Table 2: Comparison of 5-year peak flows between existing and post-construction condition

100-Year

Drainage Basin Existing 100-Year

Peak Flow (cfs) Post-Construction 100-

Year Peak Flow (cfs) Difference in 100-

Year Peak Flow (cfs) Difference in 100-

Year Peak Flow (%) Madison to 1st 0.81 0.91 0.09 11.7% 1st to 2nd 0.82 0.90 0.08 9.4% 2nd to 3rd 0.85 0.92 0.06 7.4% 3rd to 4th 0.94 0.95 0.01 1.1% 4th to 5th 0.89 0.90 0.01 1.3% 5th to 6th 0.85 0.89 0.04 5.2% 6th to 7th 0.84 0.90 0.06 6.6% 7th to Summit 0.80 0.75 -0.05 -6.4%

Table 3: Comparison of 100-year peak flows between existing and post-construction condition

As shown in Tables 2 and 3, the post-construction surface cover generally, but marginally, increases the peak runoff flowrate in each delineated basin, except for the basin from 7th St to Summit Blvd. The greatest increases in runoff occur at the western end of the project, where existing conditions within the right of way are typically less paved and developed than at the eastern end. The easternmost basin sees a decrease in peak runoff flow rate due to the addition of lawn features within the amenity zone where impervious surface currently exists.

The general increase in peak runoff flow rate and the proposed improvements with curb and gutter lends to a formalized stormwater infrastructure system. This will help to remove surface runoff from the roadway and improve flooding and icing. To determine the rough construction cost to install a storm system as part of the project, a preliminary horizontal stormwater system layout is included as part of the 30% Design submittal. Further detailed design of the system, including pipe and inlet sizing, will be required in the next design phase.

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APPENDIX A: GRAPHICS FOR

EXISTING AND PROPOSED SURFACE

COVER

1s t A ve

M ad is on

A ve

2n d

Av e

3r d

Av e

4t h

Av e

Project Area Limits (TYP.)

PAVED (ROADWAY)

DRIVES AND WALKS

GRAVEL (PACKED)

LAWNS, SANDY SOIL

Granite St

0.73 42%

0.72 52%

0.75 50%

0.77 71%

Basin ID (TYP.)

Percent Impervious Cover (TYP.)

Basin Area in Acres (TYP.)

4t h

Av e

5t h

Av e

6t h

Av e

7t h

Av e

Su m m it

Bl vd

Project Area Limits (TYP.)

PAVED (ROADWAY)

DRIVES AND WALKS

GRAVEL (PACKED)

LAWNS, SANDY SOIL

Granite St

0.76 61%

0.74 57%

0.72 59%

0.60 96%

SCALE: 1" = 50'

EXISTING GROUND COVER WITHIN PROJECT AREA

M

AT

C H

LI

N

E- S

EE

B

O

TT

O M

L

EF

T

M

AT

C H

LI

N

E- S

EE

T

O P

R

IG

H T

1s t A ve

M ad is on

A ve

2n d

Av e

3r d

Av e

4t h

Av e

Project Area Limits (TYP.)

PAVED (ROADWAY)

DRIVES AND WALKS

GRAVEL (PACKED)

LAWNS, SANDY SOIL

Granite St

0.73 82%

0.72 84%

0.75 81%

0.77 82%

Basin ID (TYP.)

Percent Impervious Cover (TYP.)

Basin Area in Acres (TYP.)

4t h

Av e

5t h

Av e

6t h

Av e

7t h

Av e

Su m m it

Bl vd

Project Area Limits (TYP.)

PAVED (ROADWAY)

DRIVES AND WALKS

GRAVEL (PACKED)

LAWNS, SANDY SOIL

Granite St

0.76 74%

0.74 75%

0.72 85%

0.60 84%

X X

SCALE: 1" = 50'

PROPOSED GROUND COVER WITHIN PROJECT AREA

M

AT

C H

LI

N

E- S

EE

B

O

TT

O M

L

EF

T

M

AT

C H

LI

N

E- S

EE

T

O P

R

IG

H T

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APPENDIX B: RATIONAL METHOD

CALCULATIONS FOR DRAINAGE

BASINS

Date: 9/28/2023 Project Number: 00DEN.00265.00 Calculated By: A. Lamping Checked By: J. White

5 Year Drainage Basin Total Area (SF) Total Area (AC) Paved Cover (SF) Drive/Walk Cover (SF) Gravel Cover (SF) Lawns Cover (SF) Impervious Cover (%) C Return Period C for Soil Group B Rainfall intensity (in/hr) 5-Year Peak Flow (cfs)

Madison to 1st 31,915 0.73 11,738 1,772 18,405 - 42.33% 0.648 5-year 0.603 0.665 0.29 1st to 2nd 31,549 0.72 13,711 2,671 14,174 993 51.93% 0.691 5-year 0.643 0.665 0.31 2nd to 3rd 32,756 0.75 13,682 2,602 16,472 - 49.71% 0.690 5-year 0.642 0.665 0.32 3rd to 4th 33,365 0.77 21,745 1,776 9,844 - 70.50% 0.818 5-year 0.760 0.665 0.39 4th to 5th 32,966 0.76 15,315 4,881 12,770 61.26% 0.753 5-year 0.700 0.665 0.35 5th to 6th 32,264 0.74 13,458 4,868 12,269 1,669 56.80% 0.706 5-year 0.657 0.665 0.32 6th to 7th 31,489 0.72 13,467 4,980 13,042 - 58.58% 0.736 5-year 0.684 0.665 0.33 7th to Summit 26,330 0.60 21,108 4,149 1,073 - 95.92% 0.960 5-year 0.893 0.665 0.36 Total 252,634 5.80 124,224 27,699 98,049 2,662

100 Year Drainage Basin Total Area (SF) Total Area (AC) Paved Cover (SF) Drive/Walk Cover (SF) Gravel Cover (SF) Lawns Cover (SF) Impervious Cover (%) C Return Period C for Soil Group B Rainfall intensity (in/hr) 100-Year Peak Flow (cfs)

Madison to 1st 31,915 0.73 11,738 1,772 18,405 - 42.33% 0.648 100-year 0.772 1.435 0.81 1st to 2nd 31,549 0.72 13,711 2,671 14,174 993 51.93% 0.691 100-year 0.793 1.435 0.82 2nd to 3rd 32,756 0.75 13,682 2,602 16,472 - 49.71% 0.690 100-year 0.792 1.435 0.85 3rd to 4th 33,365 0.77 21,745 1,776 9,844 - 70.50% 0.818 100-year 0.855 1.435 0.94 4th to 5th 32,966 0.76 15,315 4,881 12,770 61.26% 0.753 100-year 0.823 1.435 0.89 5th to 6th 32,264 0.74 13,458 4,868 12,269 1,669 56.80% 0.706 100-year 0.800 1.435 0.85 6th to 7th 31,489 0.72 13,467 4,980 13,042 - 58.58% 0.736 100-year 0.814 1.435 0.84 7th to Summit 26,330 0.60 21,108 4,149 1,073 - 95.92% 0.960 100-year 0.924 1.435 0.80 Total 252,634 5.80 124,224 27,699 98,049 2,662

Paved % 1 Drive and Walks % 0.9 Gravel (Packed) % 0.4 Lawns, sandy soil % 0.02 Storm Duration (min) 60 Rainfall Depth for 100-year Storm (in) 1.42 Rainfall Depth for 5-year Storm (in) 0.658

Stormwater Analysis: Granite Street 30% Design Town of Frisco, Colorado Existing 5-Year and 100-Year Peak Flows

Calculated By: A. Lamping Checked By: J. White

5 Year Drainage Basin Total Area (SF) Total Area (AC) Paved Cover (SF) Drive/Walk Cover (SF) Gravel Cover (SF) Lawns Cover (SF) Impervious Cover (%) C Return Period C for Soil Group B Rainfall intensity (in/hr) 5-Year Peak Flow (cfs)

Madison to 1st 31,915 0.73 16,764 9,423 3,181 2,547 82.05% 0.832 5-year 0.774 0.665 0.38 1st to 2nd 31,549 0.72 17,252 9,123 2,737 2,437 83.60% 0.843 5-year 0.784 0.665 0.38 2nd to 3rd 32,756 0.75 16,075 10,514 2,312 3,855 81.17% 0.810 5-year 0.754 0.665 0.38 3rd to 4th 33,365 0.77 18,139 9,278 3,455 2,493 82.17% 0.837 5-year 0.778 0.665 0.40 4th to 5th 32,966 0.76 15,405 9,111 4,583 3,867 74.37% 0.774 5-year 0.720 0.665 0.36 5th to 6th 32,264 0.74 15,191 9,143 5,121 2,809 75.42% 0.791 5-year 0.736 0.665 0.36 6th to 7th 31,489 0.72 17,165 9,616 1,853 2,855 85.05% 0.845 5-year 0.786 0.665 0.38 7th to Summit 26,330 0.60 14,999 7,183 1,384 2,764 84.25% 0.838 5-year 0.780 0.665 0.31 Total 252,634 5.80 130,990 73,391 24,626 23,627

100 Year Drainage Basin Total Area (SF) Total Area (AC) Paved Cover (SF) Drive/Walk Cover (SF) Gravel Cover (SF) Lawns Cover (SF) Impervious Cover (%) C Return Period C for Soil Group B Rainfall intensity (in/hr) 100-Year Peak Flow (cfs)

Madison to 1st 31,915 0.73 16,764 9,423 3,181 2,547 82.05% 0.832 100-year 0.862 1.435 0.91 1st to 2nd 31,549 0.72 17,252 9,123 2,737 2,437 83.60% 0.843 100-year 0.867 1.435 0.90 2nd to 3rd 32,756 0.75 16,075 10,514 2,312 3,855 81.17% 0.810 100-year 0.851 1.435 0.92 3rd to 4th 33,365 0.77 18,139 9,278 3,455 2,493 82.17% 0.837 100-year 0.864 1.435 0.95 4th to 5th 32,966 0.76 15,405 9,111 4,583 3,867 74.37% 0.774 100-year 0.833 1.435 0.90 5th to 6th 32,264 0.74 15,191 9,143 5,121 2,809 75.42% 0.791 100-year 0.842 1.435 0.89 6th to 7th 31,489 0.72 17,165 9,616 1,853 2,855 85.05% 0.845 100-year 0.868 1.435 0.90 7th to Summit 26,330 0.60 14,999 7,183 1,384 2,764 84.25% 0.838 100-year 0.865 1.435 0.75 Total 252,634 5.80 130,990 73,391 24,626 23,627

Paved % 1 Drive and Walks % 0.9 Gravel (Packed) % 0.4 Lawns, sandy soil % 0.02 Storm Duration (min) 60 Rainfall Depth for 100-year Storm (in) 1.42 Rainfall Depth for 5-year Storm (in) 0.658

Stormwater Analysis: Granite Street 30% Design

Post-Construction 5-Year and 100-Year Peak Flows

Calculated By: A. Lamping Checked By: J. White

5-Year Drainage Basin Existing 5-Year Peak Flow (cfs) Post-Construction 5-Year Peak Flow (cfs) Difference in 5-Year Peak Flow (cfs) Difference in 5-Year Peak Flow (%)

Madison to 1st 0.29 0.38 0.08 28.4% 1st to 2nd 0.31 0.38 0.07 22.0% 2nd to 3rd 0.32 0.38 0.06 17.4% 3rd to 4th 0.39 0.40 0.01 2.3% 4th to 5th 0.35 0.36 0.01 2.8% 5th to 6th 0.32 0.36 0.04 12.0% 6th to 7th 0.33 0.38 0.05 14.9% 7th to Summit 0.36 0.31 -0.05 -12.7%

100-Year Drainage Basin Existing 100-Year Peak Flow (cfs) Post-Construction 100-Year Peak Flow (cfs) Difference in 100-Year Peak Flow (cfs) Difference in 100-Year Peak Flow (%)

Madison to 1st 0.81 0.91 0.09 11.7% 1st to 2nd 0.82 0.90 0.08 9.4% 2nd to 3rd 0.85 0.92 0.06 7.4% 3rd to 4th 0.94 0.95 0.01 1.1% 4th to 5th 0.89 0.90 0.01 1.3% 5th to 6th 0.85 0.89 0.04 5.2% 6th to 7th 0.84 0.90 0.06 6.6% 7th to Summit 0.80 0.75 -0.05 -6.4%

Stormwater Analysis: Granite Street 30% Design

Change in 5-Year and 100-Year Peak Flows

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APPENDIX C: NRCS SOIL REPORT

Soil Map The soil map section includes the soil map for the defined area of interest, a list of soil map units on the map and extent of each map unit, and cartographic symbols displayed on the map. Also presented are various metadata about data used to produce the map, and a description of each soil map unit.

Custom Soil Resource Report Soil Map

405200 405300 405400 405500 405600 405700 405800 405900 406000 406100 406200 406300

405100 405200 405300 405400 405500 405600 405700 405800 405900 406000 406100 406200 406300

39° 34' 44'' N

6°

' 1 7'

' W 39° 34' 44'' N

6°

' 2

3' ' W

39° 34' 17'' N

6°

' 1

7' ' W

39° 34' 17'' N

6°

' 2

3' ' W

N

Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84 0 250 500 1000 1500

Feet 0 50 100 200 300

Meters Map Scale: 1:5,860 if printed on A landscape (11" x 8.5") sheet.

Soil Map may not be valid at this scale.

MAP LEGEND MAP INFORMATION

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

Soils Soil Map Unit Polygons

Soil Map Unit Lines

Soil Map Unit Points

Special Point Features Blowout

Borrow Pit

Clay Spot

Closed Depression

Gravel Pit

Gravelly Spot

Landfill

Lava Flow

Marsh or swamp

Mine or Quarry

Miscellaneous Water

Perennial Water

Rock Outcrop

Saline Spot

Sandy Spot

Severely Eroded Spot

Sinkhole

Slide or Slip

Sodic Spot

Spoil Area

Stony Spot

Very Stony Spot

Wet Spot

Other

Special Line Features

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.

Warning: Soil Map may not be valid at this scale.

Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale.

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: Summit County Area, Colorado Survey Area Data: Version 14, Sep 6, 2022

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—Sep 7, 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.

Map Unit Legend

Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI

7C Grenadier gravelly loam, 0 to 6 percent slopes

39.2 98.2%

10 Histic Cryaquolls, nearly level 0.7 1.8%

Totals for Area of Interest 39.9 100.0%

Map Unit Descriptions The map units delineated on the detailed soil maps in a soil survey represent the soils or miscellaneous areas in the survey area. The map unit descriptions, along with the maps, can be used to determine the composition and properties of a unit.

A map unit delineation on a soil map represents an area dominated by one or more major kinds of soil or miscellaneous areas. A map unit is identified and named according to the taxonomic classification of the dominant soils. Within a taxonomic class there are precisely defined limits for the properties of the soils. On the landscape, however, the soils are natural phenomena, and they have the characteristic variability of all natural phenomena. Thus, the range of some observed properties may extend beyond the limits defined for a taxonomic class.

Areas of soils of a single taxonomic class rarely, if ever, can be mapped without including areas of other taxonomic classes. Consequently, every map unit is made up of the soils or miscellaneous areas for which it is named and some minor components that belong to taxonomic classes other than those of the major soils.

Most minor soils have properties similar to those of the dominant soil or soils in the map unit, and thus they do not affect use and management. These are called noncontrasting, or similar, components. They may or may not be mentioned in a particular map unit description. Other minor components, however, have properties and behavioral characteristics divergent enough to affect use or to require different management. These are called contrasting, or dissimilar, components. They generally are in small areas and could not be mapped separately because of the scale used. Some small areas of strongly contrasting soils or miscellaneous areas are identified by a special symbol on the maps. If included in the database for a given area, the contrasting minor components are identified in the map unit descriptions along with some characteristics of each. A few areas of minor components may not have been observed, and consequently they are not mentioned in the descriptions, especially where the pattern was so complex that it was impractical to make enough observations to identify all the soils and miscellaneous areas on the landscape.

The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The objective of mapping is not to delineate pure taxonomic classes but rather to separate the landscape into landforms or landform segments that have similar use and management requirements. The delineation of such segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, however, onsite investigation is needed to define and locate the soils and miscellaneous areas.

An identifying symbol precedes the map unit name in the map unit descriptions.

Each description includes general facts about the unit and gives important soil properties and qualities.

Soils that have profiles that are almost alike make up a soil series. Except for differences in texture of the surface layer, all the soils of a series have major horizons that are similar in composition, thickness, and arrangement.

Soils of one series can differ in texture of the surface layer, slope, stoniness, salinity, degree of erosion, and other characteristics that affect their use. On the basis of such differences, a soil series is divided into soil phases. Most of the areas shown on the detailed soil maps are phases of soil series. The name of a soil phase commonly indicates a feature that affects use or management. For example, Alpha silt loam, 0 to 2 percent slopes, is a phase of the Alpha series.

Some map units are made up of two or more major soils or miscellaneous areas.

These map units are complexes, associations, or undifferentiated groups.

A complex consists of two or more soils or miscellaneous areas in such an intricate pattern or in such small areas that they cannot be shown separately on the maps.

The pattern and proportion of the soils or miscellaneous areas are somewhat similar in all areas. Alpha-Beta complex, 0 to 6 percent slopes, is an example.

An association is made up of two or more geographically associated soils or miscellaneous areas that are shown as one unit on the maps. Because of present or anticipated uses of the map units in the survey area, it was not considered practical or necessary to map the soils or miscellaneous areas separately. The pattern and relative proportion of the soils or miscellaneous areas are somewhat similar. Alpha-Beta association, 0 to 2 percent slopes, is an example.

An undifferentiated group is made up of two or more soils or miscellaneous areas that could be mapped individually but are mapped as one unit because similar interpretations can be made for use and management. The pattern and proportion of the soils or miscellaneous areas in a mapped area are not uniform. An area can be made up of only one of the major soils or miscellaneous areas, or it can be made up of all of them. Alpha and Beta soils, 0 to 2 percent slopes, is an example.

Some surveys include miscellaneous areas. Such areas have little or no soil material and support little or no vegetation. Rock outcrop is an example.

Summit County Area, Colorado

7C—Grenadier gravelly loam, 0 to 6 percent slopes

Map Unit Setting National map unit symbol: jphc Elevation: 9,000 to 13,000 feet Mean annual precipitation: 20 to 30 inches Mean annual air temperature: 30 to 34 degrees F Frost-free period: 30 to 50 days Farmland classification: Not prime farmland

Map Unit Composition Grenadier and similar soils: 80 percent Minor components: 10 percent Estimates are based on observations, descriptions, and transects of the mapunit.

Description of Grenadier

Typical profile H1 - 0 to 3 inches: gravelly loam H2 - 3 to 16 inches: gravelly sandy clay loam H3 - 16 to 60 inches: very cobbly sandy loam

Properties and qualities Slope: 2 to 6 percent Depth to restrictive feature: More than 80 inches Drainage class: Well drained Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high

(0.20 to 2.00 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Available water supply, 0 to 60 inches: Low (about 4.6 inches)

Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 6e Hydrologic Soil Group: B Ecological site: F048AY918CO - Spruce-Fir Woodland Hydric soil rating: No

Minor Components

Cumulic cryaquolls Percent of map unit: 5 percent Landform: Swales Hydric soil rating: Yes

Histic cryaquolls Percent of map unit: 5 percent Landform: Swales Hydric soil rating: Yes

10—Histic Cryaquolls, nearly level

Map Unit Setting National map unit symbol: jpgc Elevation: 7,950 to 10,870 feet Mean annual precipitation: 20 to 30 inches Mean annual air temperature: 36 to 43 degrees F Frost-free period: 20 to 70 days Farmland classification: Not prime farmland

Map Unit Composition Histic cryaquolls and similar soils: 90 percent Minor components: 10 percent Estimates are based on observations, descriptions, and transects of the mapunit.

Description of Histic Cryaquolls

Setting Landform: Alluvial fans, flood plains Landform position (three-dimensional): Mountainbase, tread Down-slope shape: Linear Across-slope shape: Linear Parent material: Organic material over stratified, sandy loam to clayey alluvium over sand and gravel

Typical profile O - 0 to 8 inches: mucky peat H1 - 8 to 28 inches: stratified sandy loam to clay H2 - 28 to 60 inches: sand and gravel

Properties and qualities Slope: 0 to 5 percent Depth to restrictive feature: More than 80 inches Drainage class: Poorly drained Runoff class: Very low Capacity of the most limiting layer to transmit water (Ksat): Moderately low to high

(0.06 to 6.00 in/hr) Depth to water table: About 0 to 24 inches Frequency of flooding: NoneFrequent Frequency of ponding: None Available water supply, 0 to 60 inches: Moderate (about 7.0 inches)

Interpretive groups Land capability classification (irrigated): 7w Land capability classification (nonirrigated): 7w Hydrologic Soil Group: A/D Ecological site: R048AY241CO - Mountain Meadow Hydric soil rating: Yes

Minor Components

Cumulic cryaquolls Percent of map unit: 10 percent Landform: Flood plains Hydric soil rating: Yes

TOOLE DESIGN | 10

APPENDIX D: FRISCO DRAINAGE

STUDY