Attachment_7_Drainage_Report.pdf

FINAL DRAINAGE REPORT

SLOAN CANYON NATIONAL

CONSERVATION AREA VISITOR

CENTER CONTACT STATION

2 9 9 8 N A W G H A W P O A R O A D

H E N D E R S O N , N E V A D A 8 9 044

P R E P A R E D F O R U N I T E D S T A T E S D E P A R T M E N T O F

T H E I N T E R I O R B U R E A U O F L A N D M A N A G E M E N T

P R E P A R E D B Y S H O R T E L L I O T T H E N D R I C K S O N , I N C .

( S E H , I N C . ) S E H P r o j e c t N u m b e r : 1 4 8 0 4

August 16, 2021

A P P L I C A N T I N F O R M A T I O N

Owner: U.S. Bureau of Land Management

Prepared by: Short Elliott Hendrickson, Inc. (SEH) 2000 South Colorado Boulevard, Suite 6000 Denver, CO 80222-7938

E N G I N E E R I N G S T A T E M E N T S

ENG IN E ER ’S STAT EM E N T

This report for the drainage design for the Sloan Canyon National Conservation Area Visitor Center Contact Station was prepared by me (or under my supervision) in accordance with the provisions of Clark County Region Flood Control District Hydrologic Criteria and Drainage Design Manual and was designed to comply with the provisions therein.

By: James D. Hayson

Licensed Professional Engineer

State of Nevada No. 019781

Table of Contents

Sloan Canyon Visitor Center – Final Drainage Report

E X E C U T I V E S U M M A R Y

Table of Contents

Introduction

A. Site Location

Figure 1 – Project Location Map

B. Site Description

C. Proposed Project Description

D. Flood Hazard

Historic Drainage

A. Existing Basins

Proposed Drainage

A. Proposed Basins

B. Basin Hydraulic Analysis

Table 1 – 1-hr Rainfall Depths Based on CCRFCD Criteria and included NOAA

Atlas 2 figure

Table 2 – Proposed Peak Flow Results

C. Water Quality and Detention

Conclusion

References

List of Tables

Table 1 – 1-hr Rainfall Depths Based on CCRFCD Criteria and included NOAA Atlas 2 figure

Table 2 – Proposed Peak Flow Results

List of Figures

Figure 1 – Project Location Map 4

List of Appendices

Appendix A – Soil Map

Appendix B – Flood Hazard Map

Appendix C – Existing Drainage Basin Map

Appendix D – Proposed Drainage Basin Map

Appendix E – Hydrologic and Hydraulic Calculations

Sloan Canyon Visitor Center – Conceptual Drainage Study Page 4 of 12

INTR O DU CT IO N

The purpose of this Final Drainage Report is to present the design methodology and results for a drainage study and improvements associated with the construction of a new Visitor Center Contact Station at Sloan Canyon National Conservation Area. As feasible, the improvement design meets the drainage requirements outlined in the Clark County Region Flood Control District Hydrologic Criteria and Drainage Design Manual (Clark County Reginal Flood Control District, 2014).

The project is also subject to the criteria in Section 438 of the Energy Independence and Security Act (EISA 438).

The document, Technical Guidance on Implementing the Stormwater Runoff Requirements for Federal Projects under Section 438 (December 2009) has two options to address storm water. The first is to retain the 95th percentile (20-year) Storm and allow it to infiltrate. The second is to use a site specific hydrologic analysis to limit release rates to historic values. Option two was chosen as it is more in line with the Clark County Region Flood Control District Hydrologic Criteria (CCRFCD) and Drainage Design Manual and soil type and depth to bedrock do not lend the site to infiltration. The CCRFCD criteria was used to carry out the site specific analysis.

A. Site L oc ation

The project is located in Henderson, Clark County, Nevada. Nawghaw Poa Road up to the parking lot is in within the City of Henderson Limits. The Visitor Center is located within unincorporated Clark County, approximately 0.7 miles south of Democracy Drive. The site is located within the southwest ¼ of Section 26, Township 23 South, Range 61 West. The general project location is shown in Figure 1.

Figure 1 – Project Location Map

B. Site Desc ription

The Visitor Center Contact Station at Sloan Canyon National Conservation Area currently consists of approximately 19 parking spaces supporting a mobile trailer as the visitor center. The facility sits on a ridge near the top of the drainage basin. The existing two lane paved Nawghaw Poa Road (the access road) with adjacent 10-12 foot paved trail provides access to the facility. The access road runs from the building along

Project Location

Democracy Drive

Sloan Canyon Visitor Center – Conceptual Drainage Study Page 5 of 12 the same ridge to the north and connects to Democracy Drive. The facility sits on the edge of the Sloan Canyon National Conservation Area. The surrounding terrain is generally undeveloped desert typically with hydrologic group D soil. Soil Map can be found in Appendix A.

C. Prop osed P rojec t D escrip tion

A permanent Visitor Center and Amphitheater is proposed to be constructed along with a paved surface parking lot to support the facility. The parking improvements will tie in to the existing access road. A water line will be installed along the road to supply the facility with water for domestic and fire. A pump station will be needed near Democracy Drive to provide pressure necessary at the facility. A septic system will be installed to the north of the facility. A sanitary line for future use will be installed along the access road to be stubbed out near Democracy Drive. A detention pond will be constructed in the available space with in the parking lot to provide flood attenuation and water quality.

D. Flood H az ard

The project site is located in a FEMA flood Zone X. Zone X is defined as the 500-year flood zone, areas in the 100 year flood zone with average depth less than one foot, or with drainage areas of less than one square mile.

The project area is split between Firm Map 32003C2925D and 32003C2950D. These maps have not been printed by FEMA, therefore Firmette maps have been created from FEMA’s National Flood Hazard Layer Viewer and have been included in Appendix B.

HIS T OR IC DR A IN AG E

The site is currently surrounded by undeveloped naturally draining land. The site in located on a ridge and the access road generally runs down the same ridge to Democracy Drive. Drainage is divided at the facility due to the ridge with approximately 70% of the study area headed to the northeast and the 30% to the northwest. The flow along the road generally spits at the road centerline and continues east or west to the natural drainage ways. The access road intersects Democracy Drive at a high point and all flows on the east head east along Democracy Drive in a roadside swale. All flows west of the intersection continue along Democracy Drive west and turn north to join the main drainage path.

A. Existing Basins

Existing basins were delineated within the same overall footprint as the proposed basins to examine the affect the proposed site will have on existing drainage. This basin was then subdivided into two sub-basins along the ridge. The overall existing site is 13.2% impervious. The Existing Drainage Basin Map can be found in Appendix C.

Basin EX1 is a 1.42-acre area on the east half of the existing site. It consists of undeveloped desert and the majority of the existing paved parking lot and road. The basin is 38.2% impervious.

Basin EX2 is a 3.62-acre area on the west half of the existing site. It consists mostly of undeveloped desert with a small portion of the existing paved parking lot and road. The basin is 3.4% impervious.

PR OPOS E D DR AIN AG E

The major affect the project will have on existing drainage is an increase in imperviousness. Proposed conditions will have an impervious value of 38.4% which is a considerable increase from the existing 13.2%. The majority of flows will be conveyed to a constructed pond on the north end of the parking lot. Flows will then be discharged to the east and west from an outlet structure with dual pipes to preserve the existing historic flow split. The Proposed Drainage Basin Map can be found in Appendix D.

A. Prop osed Basins

Basin A1 is a 0.89-acre basin on the eastern half of the site. It contains offsite undeveloped desert to the south, the proposed building, and the eastern half of the parking lot. The basin has an impervious value of 67.7%.

Runoff from the offsite portion flow onsite and is joined by onsite flows and continue north to the proposed pond.

Sloan Canyon Visitor Center – Conceptual Drainage Study Page 6 of 12

Basin A2 is a 0.70-acre basin on the western half of the site. It contains offsite undeveloped desert to the south and western half of the parking lot. The basin has an impervious value of 91.5%. Runoff from the offsite portion flow onsite and is joined by onsite flows and continue north to the proposed pond.

Basin A3 is the 0.86-acre encompassing the proposed detention pond. It contains a portion of the parking lot, the sidewalk adjacent to the pond and the pond. It has an impervious value of 44.7%. Flow are collected in the pond where flood attenuation and water quality will be provided

Basin A4 is a 0.31-acre basin consisting of the majority of the roof of the visitor center, the surrounding walks, and desert area. The basin has an impervious value of 50.5%. Runoff is collected by proposed roof drains and area inlets and directed to the proposed pond via 8” HDPE landscaping drain. Pipe capacity calculations can be found in Appendix E.

Basin B1 is a 0.23-acre basin consisting of the asphalt roadway to the north of the pond. The basin has an impervious value of 100%. This portion cannot be captured due to the topography and will flow down the road.

Flows will spread off the road to the east and west and into the adjacent drainages on either side of the roadway as flows do in the existing condition.

Basin C1 is a 0.79-acre basin consisting of the area that drains to the amphitheater. The majority of the basin is undeveloped desert and the concrete amphitheater. The basin has an impervious value of 9.6%. This portion cannot be directed due to the topography and will flow down the road. Runoff will be collected in the low spot of the amphitheater by an area drain and will be carried east via a proposed storm pipe that will be conveyed to a proposed riprapped settling basin that will help trap sediment and spread flows to prevent erosion at the outlet of the proposed storm pipe.

Basin OS1 is the 1.96-acre basin to the south and west of the site. The basin is entirely undeveloped desert land that drains to the south side of the site parking lot and will be diverted around the site to the west via a proposed diversion channel. The channel will discharge to a level spreader allowing runoff to continue to the existing drainage. The flow from this basin will be diverted around the site to historic drainage paths and will have no adverse effects on the downstream system. The proposed diversion swale has been sized to carry the 100-year flow from the basin of 3.94 cfs.

Basin OS2 is the basin that drains to and around the building as well as the slopes grading back to existing along the east edge of the facility. These flows will be released undetained to follow historic drainage paths.

Due to topography these flows could not be kept on site but are not anticipated to cause any detrimental effects.

B. Basin H yd raul ic Analysis

Maximum discharge for each basin was calculated using the Rational Method as directed by Clark County Region Flood Control District (CCRFCD) Hydrologic Criteria and Drainage Design Manual (HCDDM) section

500. Rainfall depths are based on the NOAA Atlas 2 maps provided in the HCDDM figures 501-512. These figures are used in conjunction with CCRFCD Standard From 3 and the methodology laid out in section 502 of the HCDDM to compute the design storm depths. CCRFCD uses 10-year and 100-year as the minor and major respective storms for design. Runoff coefficients and Peak flows for these storms can be found in Table 2 below.

Table 1 – 1-hr Rainfall Depths Based on CCRFCD Criteria and included NOAA Atlas 2 figure

Design Storm

Rainfall Depth (in)

10-yr 1.39

100-yr 2.35

Sloan Canyon Visitor Center – Conceptual Drainage Study Page 7 of 12

Table 2 – Proposed Peak Flow Results

Basin Summary

Basin

ID

Contributing Area (AC)

Runoff Coefficient Peak Runoff Flow (cfs)

Design Point

% Impv C10 C100 Q10 Q100

A1 1 0.89 67.7 0.69 0.79 1.12 2.16

A2 2 0.70 91.5 0.85 0.89 1.33 2.36

A3 3 0.86 44.7 0.54 0.69 1.12 2.42

A4 4 0.31 50.5 0.59 0.71 0.44 0.89

B1 5 0.23 100.0 0.90 0.93 0.50 0.88

C1 6 0.79 9.6 0.31 0.54 0.38 1.11

OS1 7 1.96 0.0 0.25 0.50 1.17 3.94

OS2 0.48 0.0 0.25 0.50 0.29 0.97

Hydrologic and Hydraulic calculations used to find these values can be found in Appendix E.

C. Water Q u ality and Detention

Water quality and detention have been provided for Basin A1, A2, A3 and A4. The HCDDM requires a 24-hour minimum drain time for the water quality event and the 100-year storm event. The 100-year storm is to be released at historic rates. The methods for water quality and detention calculations from the HCDDM sections

1203.1.2 and 1207.1 were used. It was calculated that a volume of 0.049 acre-ft is needed for water quality and 0.180 acre-ft for 100-year detention to meet the required drain times and release rates. Section 1207 of the HCDDM suggests Denver Urban Drainage Flood Control District as a location for water quality and detention basin outlet structure sizing. The pond outlet structure was sized using Mile High Flood District (formerly Denver Urban Drain Flood Control District) MHFD-Detenion_v4.03 spreadsheet. Mile High Flood District suggests a 40-hour drain time for the water quality and 100-year events. The 40-hour drain time was selected for this design. The outlet structure will have dual outlet 18” HDPE pipes such that the flows can be directed to both sides of the ridge as they are under existing conditions. The outlet pipes from the pond will each release to a level spreader and 12” D50 riprap to mitigate erosion at discharge points. Pond sizing calculations can be found in Appendix E.

CONC LU S I ON

The proposed improvements to Sloan Canyon National Conservation Area Visitor Center Contact Station increase the imperviousness of the study area from 10.7% to 33.5%. A proposed detention pond will meet the EISA 438 and CCRFCD HCDDM drain time and release rate criteria for improvements and will provide adequate flood protection and water quality during the design events. The proposed site will not have adverse drainage effects on adjacent or downstream properties.

Sloan Canyon Visitor Center – Conceptual Drainage Study Page 8 of 12

REF ER ENC ES

Clark County Regional Flood Control District. (August 1999). Hydrologic Criteria and Drainage Design

Manual, Volume 2, Structures, Storage, and Recreation. Las Vegas, Nevada: Clark County Regional Flood

Control District (with September 2014 updates).

United States Environmental Protection Agency. (December 2009). Technical Guidance on Implementing the Stormwater Runoff Requirements for Federal Projects under Section 438. Washington, DC: Office of

Water (4503T)

Sloan Canyon Visitor Center – Conceptual Drainage Study

Appendix A – Soil Map

Soil Map—Las Vegas Valley Area, Nevada, Part of Clark County

Natural Resources Conservation Service

Web Soil Survey National Cooperative Soil Survey

5/15/2019

668600 668700 668800 668900 669000 669100 669200 669300 669400 669500 669600 669700

668700 668800 668900 669000 669100 669200 669300 669400 669500 669600 669700

35° 55' 37'' N

5°

' 5 3'

' W 35° 55' 37'' N

5°

' 7

'' W

35° 54' 48'' N

5°

' 5

3' ' W

35° 54' 48'' N

5°

' 7

'' W

N

Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 11N WGS84 0 350 700 1400 2100

Feet 0 100 200 400 600

Meters Map Scale: 1:7,360 if printed on A portrait (8.5" x 11") 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: Las Vegas Valley Area, Nevada, Part of Clark County Survey Area Data: Version 13, Sep 14, 2018

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

Date(s) aerial images were photographed: May 7, 2011—Oct 1, 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.

Soil Map—Las Vegas Valley Area, Nevada, Part of Clark County

Natural Resources Conservation Service

Web Soil Survey National Cooperative Soil Survey

5/15/2019

Map Unit Legend

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

150 Cave very stony sandy loam, 0 to 4 percent slopes

12.8 8.0%

152 Cave gravelly fine sandy loam, 0 to 4 percent slopes

146.7 92.0%

Totals for Area of Interest 159.5 100.0%

Soil Map—Las Vegas Valley Area, Nevada, Part of Clark County

Natural Resources Conservation Service

Web Soil Survey National Cooperative Soil Survey

5/15/2019

Appendix B– Flood Hazard Map

USGS The National Map: Orthoimagery. Data refreshed April, 2019.

National Flood Hazard Layer FIRMette

0 500 1,000 1,500 2,000250 Feet

Ü

5°

7'5 2.6

6"W 35°55'13.27"N

115°7'15.20"W

35°54'44.13"N

SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT

SPECIAL FLOOD

HAZARD AREAS

Without Base Flood Elevation (BFE) Zone A, V, A99

With BFE or Depth Zone AE, AO, AH, VE, AR Regulatory Floodway

0.2% Annual Chance Flood Hazard, Areas of 1% annual chance flood with average depth less than one foot or with drainage areas of less than one square mile Zone X Future Conditions 1% Annual Chance Flood Hazard Zone X Area with Reduced Flood Risk due to Levee. See Notes. Zone X Area with Flood Risk due to Levee Zone D

NO SCREEN Area of Minimal Flood Hazard Zone X

Area of Undetermined Flood Hazard Zone D

Channel, Culvert, or Storm Sewer Levee, Dike, or Floodwall

Cross Sections with 1% Annual Chance

17.5 Water Surface Elevation

Coastal Transect

Coastal Transect Baseline Profile Baseline Hydrographic Feature

Base Flood Elevation Line (BFE)

Effective LOMRs

Limit of Study Jurisdiction Boundary

Digital Data Available No Digital Data Available Unmapped

This map complies with FEMA's standards for the use of digital flood maps if it is not void as described below.

The basemap shown complies with FEMA's basemap accuracy standards The flood hazard information is derived directly from the authoritative NFHL web services provided by FEMA. This map was exported on 5/15/2019 at 8:39:17 AM and does not reflect changes or amendments subsequent to this date and time. The NFHL and effective information may change or become superseded by new data over time.

This map image is void if the one or more of the following map elements do not appear: basemap imagery, flood zone labels, legend, scale bar, map creation date, community identifiers, FIRM panel number, and FIRM effective date. Map images for unmapped and unmodernized areas cannot be used for regulatory purposes.

Legend

OTHER AREAS OF

FLOOD HAZARD

OTHER AREAS

GENERAL

STRUCTURES

OTHER

FEATURES

MAP PANELS

1:6,000

B 20.2

The pin displayed on the map is an approximate point selected by the user and does not represent an authoritative property location.

0 500 1,000 1,500 2,000250 Feet

Ü

5°

7'4 7.4

2"W 35°55'31.38"N

115°7'9.96"W

35°55'2.24"N

SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT

SPECIAL FLOOD

HAZARD AREAS

Without Base Flood Elevation (BFE) Zone A, V, A99

With BFE or Depth Zone AE, AO, AH, VE, AR Regulatory Floodway

0.2% Annual Chance Flood Hazard, Areas of 1% annual chance flood with average depth less than one foot or with drainage areas of less than one square mile Zone X Future Conditions 1% Annual Chance Flood Hazard Zone X Area with Reduced Flood Risk due to Levee. See Notes. Zone X Area with Flood Risk due to Levee Zone D

NO SCREEN Area of Minimal Flood Hazard Zone X

Area of Undetermined Flood Hazard Zone D

Channel, Culvert, or Storm Sewer Levee, Dike, or Floodwall

Cross Sections with 1% Annual Chance

17.5 Water Surface Elevation

Coastal Transect

Coastal Transect Baseline Profile Baseline Hydrographic Feature

Base Flood Elevation Line (BFE)

Effective LOMRs

Limit of Study Jurisdiction Boundary

Digital Data Available No Digital Data Available Unmapped

This map complies with FEMA's standards for the use of digital flood maps if it is not void as described below.

The basemap shown complies with FEMA's basemap accuracy standards The flood hazard information is derived directly from the authoritative NFHL web services provided by FEMA. This map was exported on 5/15/2019 at 8:43:40 AM and does not reflect changes or amendments subsequent to this date and time. The NFHL and effective information may change or become superseded by new data over time.

This map image is void if the one or more of the following map elements do not appear: basemap imagery, flood zone labels, legend, scale bar, map creation date, community identifiers, FIRM panel number, and FIRM effective date. Map images for unmapped and unmodernized areas cannot be used for regulatory purposes.

Legend

OTHER AREAS OF

FLOOD HAZARD

OTHER AREAS

GENERAL

STRUCTURES

OTHER

FEATURES

MAP PANELS

1:6,000

B 20.2

The pin displayed on the map is an approximate

0 500 1,000 1,500 2,000250 Feet

Ü

5°

7'4 3.8

6"W 35°55'47.27"N

115°7'6.41"W

35°55'18.13"N

SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT

SPECIAL FLOOD

HAZARD AREAS

Without Base Flood Elevation (BFE) Zone A, V, A99

With BFE or Depth Zone AE, AO, AH, VE, AR Regulatory Floodway

0.2% Annual Chance Flood Hazard, Areas of 1% annual chance flood with average depth less than one foot or with drainage areas of less than one square mile Zone X Future Conditions 1% Annual Chance Flood Hazard Zone X Area with Reduced Flood Risk due to Levee. See Notes. Zone X Area with Flood Risk due to Levee Zone D

NO SCREEN Area of Minimal Flood Hazard Zone X

Area of Undetermined Flood Hazard Zone D

Channel, Culvert, or Storm Sewer Levee, Dike, or Floodwall

Cross Sections with 1% Annual Chance

17.5 Water Surface Elevation

Coastal Transect

Coastal Transect Baseline Profile Baseline Hydrographic Feature

Base Flood Elevation Line (BFE)

Effective LOMRs

Limit of Study Jurisdiction Boundary

Digital Data Available No Digital Data Available Unmapped

This map complies with FEMA's standards for the use of digital flood maps if it is not void as described below.

The basemap shown complies with FEMA's basemap accuracy standards The flood hazard information is derived directly from the authoritative NFHL web services provided by FEMA. This map was exported on 5/15/2019 at 8:42:52 AM and does not reflect changes or amendments subsequent to this date and time. The NFHL and effective information may change or become superseded by new data over time.

This map image is void if the one or more of the following map elements do not appear: basemap imagery, flood zone labels, legend, scale bar, map creation date, community identifiers, FIRM panel number, and FIRM effective date. Map images for unmapped and unmodernized areas cannot be used for regulatory purposes.

Legend

OTHER AREAS OF

FLOOD HAZARD

OTHER AREAS

GENERAL

STRUCTURES

OTHER

FEATURES

MAP PANELS

1:6,000

B 20.2

The pin displayed on the map is an approximate

Appendix C– Existing Drainage Basin Map

Appendix D– Proposed Drainage Basin Map

Appendix E– Hydrologic and Hydraulic Calculations

From CCRFCD Criteria Manual Section 502.2

X1 = 1.00

X2 = 1.20

X3 = 2.20

X4 = 3.10

Y2 = 0.774

Y100 = 1.672774194

2-year 0.76 1 0.76

5-year 0.98 1.16 1.1368

10-year 1.12 1.24 1.3888

25-year 1.31 1.33 1.7423

50-year 1.48 1.39 2.0572

100-year 1.64 1.43 2.3452

Duration Ratio 2-year 5-year 10-year 25-year 50-year 100-year

(min) Inc Depth Intensity Inc Depth Intensity Inc Depth Intensity Inc Depth Intensity Inc Depth Intensity Inc Depth Intensity

5 0.29 0.22 2.64 0.33 3.96 0.40 4.83 0.51 6.06 0.60 7.16 0.68 8.16

10 0.45 0.34 2.05 0.51 3.07 0.62 3.75 0.78 4.70 0.93 5.55 1.06 6.33

15 0.57 0.43 1.73 0.65 2.59 0.79 3.17 0.99 3.97 1.17 4.69 1.34 5.35

30 0.79 0.60 1.20 0.90 1.80 1.10 2.19 1.38 2.75 1.63 3.25 1.85 3.71

60 1 0.76 0.76 1.14 1.14 1.39 1.39 1.74 1.74 2.06 2.06 2.35 2.35

Adj Factor

Adj 1-Hr

Depth 3Depth

1Y2 and Y100 are plotted and connected on Standard Form 3 from CCRFCS Criteria manual to find intermediate depths

2 Depths from Standard Form 3 are multiplied by Adjustment factor from from CCRFCS Criteria manual

Table 501

Where:

Y2 = 2-yr 1-hr estimated value

Y100 = 100-yr 1-hr estimated value

X1 = 2-yr 24-hr value from Figure 501

X2 = 2-yr 24-hr value from Figure 506

X3 = 100-yr 24-hr value from Figure 507

Adjusted 1-Hour Depths are multiplied by the ratios in CCRFCS Criteria manual Table 504 to obtain rainfall depth durations less than 1-hour.

The depths are converted to intensities (in/hr) by dividing by the duration

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

0 10 20 30 40 50 60 70

In te n si ty in /h r)

Time (min)

Time-Intensity Frequency Cruve

2-year 5-year 10-year 25-year 50-year 100-year

Site Location - 0.99"

Site Location - 1.35"

Site Location - 1.49"

Site Location - 1.80"

Site Location - 1.90"

Site Location - 2.20"

Site Location - 1.19"

Site Location - 1.65"

Site Location - 1.96"

Site Location -2.45"

Site Location - 2.79"

Site Location - 3.20"

1.5

2.5

1.5

0.5

0.98 1.31

1.12

1.48

0.76

1.64

Sloan Canyon Visitor Center

Intensity

Time

(min)

I2

(in/hr)

I5

(in/hr)

I10

(in/hr)

I50

(in/hr)

I100

(in/hr) Basin ID

Tc

(min)

I2

(in/hr)

I5

(in/hr)

I10

(in/hr)

I50

(in/hr)

I100

(in/hr)

* 5 2.645 3.956 4.833 7.159 8.161

6 2.526 3.779 4.616 6.838 7.795 EX1 18.16 1.62 2.42 2.96 4.39 5.00

7 2.408 3.601 4.400 6.517 7.430 EX2 18.88 1.60 2.39 2.92 4.32 4.92

8 2.289 3.424 4.183 6.196 7.064

9 2.171 3.247 3.966 5.875 6.698

* 10 2.052 3.069 3.750 5.554 6.332

11 1.988 2.974 3.633 5.382 6.135

12 1.924 2.878 3.516 5.209 5.938

13 1.860 2.783 3.400 5.036 5.741

14 1.797 2.687 3.283 4.863 5.544

* 15 1.733 2.592 3.166 4.690 5.347

16 1.697 2.539 3.102 4.594 5.238

17 1.662 2.486 3.037 4.498 5.128

18 1.626 2.433 2.972 4.402 5.019

19 1.591 2.380 2.907 4.306 4.909 2 1 0.76 0.76

20 1.555 2.327 2.842 4.210 4.800 5 1.16 0.98 1.14

21 1.520 2.274 2.778 4.114 4.690 10 1.24 1.12 1.39

22 1.485 2.221 2.713 4.018 4.581 25 1.33 1.31 1.74

23 1.449 2.167 2.648 3.922 4.472 50 1.39 1.48 2.06

24 1.414 2.114 2.583 3.826 4.362 100 1.43 1.64 2.35

25 1.378 2.061 2.518 3.730 4.253 Notes:

26 1.343 2.008 2.454 3.634 4.143 1 - CCRFCD Precipitation Adjustment Ratios Table 501

27 1.307 1.955 2.389 3.538 4.034 2 - Calculated depth from CCRFCD Standard Form 3

28 1.272 1.902 2.324 3.442 3.924 3 - Adjusted Depths = Precip Ratio x Depth

29 1.236 1.849 2.259 3.346 3.815

* 30 1.201 1.796 2.194 3.250 3.705

31 1.186 1.774 2.167 3.211 3.660

32 1.171 1.752 2.141 3.171 3.615

33 1.157 1.730 2.114 3.131 3.569

34 1.142 1.708 2.087 3.091 3.524

35 1.127 1.686 2.060 3.052 3.479

36 1.113 1.664 2.033 3.012 3.433

37 1.098 1.642 2.006 2.972 3.388

38 1.083 1.620 1.980 2.932 3.343

39 1.069 1.598 1.953 2.892 3.297

40 1.054 1.576 1.926 2.853 3.252

41 1.039 1.554 1.899 2.813 3.207

42 1.024 1.532 1.872 2.773 3.161

43 1.010 1.510 1.845 2.733 3.116

44 0.995 1.488 1.818 2.694 3.071

45 0.980 1.466 1.792 2.654 3.025

46 0.966 1.444 1.765 2.614 2.980

47 0.951 1.423 1.738 2.574 2.935

48 0.936 1.401 1.711 2.534 2.889

49 0.922 1.379 1.684 2.495 2.844

50 0.907 1.357 1.657 2.455 2.799

51 0.892 1.335 1.630 2.415 2.753

52 0.878 1.313 1.604 2.375 2.708

53 0.863 1.291 1.577 2.336 2.663

54 0.848 1.269 1.550 2.296 2.617

55 0.833 1.247 1.523 2.256 2.572

56 0.819 1.225 1.496 2.216 2.527

57 0.804 1.203 1.469 2.177 2.481

58 0.789 1.181 1.443 2.137 2.436

59 0.775 1.159 1.416 2.097 2.391

60 0.760 1.137 1.389 2.057 2.345

Notes:

Intensities calculated per CCRFCD Section 500

Return

Period

Precip

Ratios 1 Depth

Adj

Depths

Sloan Canyon Visitor Center BY: DH

Proposed Composite C and Imperviousness DATE: 5/22/2019

CHECKED BY: SJ

DATE: 5/22/2019

Sub-Basin Data

Basin ID Description

Total

Area (ac) C10 C100 I(%) C10 C100

I(%)

Area

(ac) C10 C100 I(%)

Area

(ac) C10 C100 I(%)

Area

(ac) C10 C100 I(%)

Area

(ac)

0.90 0.93 100.00 0.88 0.89 95.00 0.85 0.87 90.00 0.25 0.50 0.00

EX1 2.62 0.39 0.59 20.8 0.90 0.93 100.00 0.54 0.88 0.89 95.00 0.85 0.87 90.00 0.25 0.50 0.00 2.07

EX2 3.62 0.27 0.51 3.4 0.90 0.93 100.00 0.12 0.88 0.89 95.00 0.85 0.87 90.00 0.25 0.50 0.00 3.50

Total Project Total 6.23 0.32 0.55 10.7 0.90 0.93 100.00 0.67 0.88 0.89 95.00 0.00 0.85 0.87 90.00 0.00 0.25 0.50 0.00 5.57

Notes:

Percent Imperviousness, I(%) is from CCRFCD Table 601

C5 is from CCRFCD Table 601

C10 is from CCRFCD Table 601

Composite C & I Paved Roads Drives and Walks Roofs Undeveloped Areas

BY: DH

Sloan Canyon Visitor Center DATE: 5/22/2019

Time of Concentration SJ

5/22/2019

Tc

C10

L1

(ft)

S

Ti

(min)

LTotal

(ft)

L2

(ft)

Sw

(ft/ft)

V

(ft/s)

Tt

(min)

Ti+Tt

(min)

EX1 2.62 0.39 440 4.0 17.0 640 200 0.020 2.8 1.2 18.2

EX2 3.62 0.27 350 4.0 17.7 550 200 0.020 2.8 1.2 18.9

Average basin slope calculated from site topographic mapping

CCRFCD Hydrologic Criteria and Drainage Design Manual (Eq 602)

CCRFCD Hydrologic Criteria and Drainage Design Manual (Fig 602)

Length / Velocity

Summation of Initial Overland Time and Travel Time (minimum 5 min)

CHECKED BY:

DATE:

INITIAL / OVERLAND TIME (Ti) OVERLAND TRAVEL TIME (Tt)

BASIN ID

AREA

(acre)

P:\AE\B\BLMNS\148049\99 Civil and Survey\5-final-dsgn\50-final-dsgn\10-Civil\Drainage\Sloan Rational EX.xlsx 3 of 4

Sloan Canyon Visitor Center DATE: 5/22/2019

Flow Rates for the 10-Year and 100-Year Storm Events CHECKED BY: SJ

DATE: 5/22/2019

BASIN ID

AREA

(acre) C10 C100

I10

(in/hr)

I100

(in/hr)

Q10

(cfs)

Q100

(cfs)

EX1 2.62 0.390 0.590 2.96 5.00 1.51 3.9

EX2 3.62 0.270 0.510 2.92 4.92 1.42 4.5

Q=KCIA where K is a local adjustment factor. K = 0.5 for the CCRFCD area per CCRFCD Criteria Manual Section 604 Time-Intensity-Frequency Cuver with Tc used to determine Intensities

P:\AE\B\BLMNS\148049\99 Civil and Survey\5-final-dsgn\50-final-dsgn\10-Civil\Drainage\Sloan Rational EX.xlsx 4 of 4

Sloan Canyon Visitor Center

Intensity

Time

(min)

I2

(in/hr)

I5

(in/hr)

I10

(in/hr)

I50

(in/hr)

I100

(in/hr) Basin ID

Tc

(min)

I2

(in/hr)

I5

(in/hr)

I10

(in/hr)

I50

(in/hr)

I100

(in/hr)

* 5 2.645 3.956 4.833 7.159 8.161

6 2.526 3.779 4.616 6.838 7.795 A1 10.99 1.99 2.98 3.63 5.38 6.14

7 2.408 3.601 4.400 6.517 7.430 A2 6.52 2.46 3.69 4.50 6.67 7.61

8 2.289 3.424 4.183 6.196 7.064 A3 5.00 2.64 3.96 4.83 7.16 8.16

9 2.171 3.247 3.966 5.875 6.698 A4 5.00 2.64 3.96 4.83 7.16 8.16

* 10 2.052 3.069 3.750 5.554 6.332 B1 5.00 2.64 3.96 4.83 7.16 8.16

11 1.988 2.974 3.633 5.382 6.135 C1 16.11 1.69 2.53 3.09 4.58 5.23

12 1.924 2.878 3.516 5.209 5.938 OS1 5.36 2.60 3.89 4.76 7.04 8.03

13 1.860 2.783 3.400 5.036 5.741 OS2 5.36 2.60 3.89 4.76 7.04 8.03

14 1.797 2.687 3.283 4.863 5.544

* 15 1.733 2.592 3.166 4.690 5.347

16 1.697 2.539 3.102 4.594 5.238

17 1.662 2.486 3.037 4.498 5.128

18 1.626 2.433 2.972 4.402 5.019

19 1.591 2.380 2.907 4.306 4.909 2 1 0.76 0.76

20 1.555 2.327 2.842 4.210 4.800 5 1.16 0.98 1.14

21 1.520 2.274 2.778 4.114 4.690 10 1.24 1.12 1.39

22 1.485 2.221 2.713 4.018 4.581 25 1.33 1.31 1.74

23 1.449 2.167 2.648 3.922 4.472 50 1.39 1.48 2.06

24 1.414 2.114 2.583 3.826 4.362 100 1.43 1.64 2.35

25 1.378 2.061 2.518 3.730 4.253 Notes:

26 1.343 2.008 2.454 3.634 4.143 See Hydrology Sheet for Detailed calculations

27 1.307 1.955 2.389 3.538 4.034 1 - CCRFCD Precipitation Adjustment Ratios Table 501

28 1.272 1.902 2.324 3.442 3.924 2 - Calculated depth from CCRFCD Standard Form 3

29 1.236 1.849 2.259 3.346 3.815 3 - Adjusted Depths = Precip Ratio x Depth

* 30 1.201 1.796 2.194 3.250 3.705

31 1.186 1.774 2.167 3.211 3.660

32 1.171 1.752 2.141 3.171 3.615

33 1.157 1.730 2.114 3.131 3.569

34 1.142 1.708 2.087 3.091 3.524

35 1.127 1.686 2.060 3.052 3.479

36 1.113 1.664 2.033 3.012 3.433

37 1.098 1.642 2.006 2.972 3.388

38 1.083 1.620 1.980 2.932 3.343

39 1.069 1.598 1.953 2.892 3.297

40 1.054 1.576 1.926 2.853 3.252

41 1.039 1.554 1.899 2.813 3.207

42 1.024 1.532 1.872 2.773 3.161

43 1.010 1.510 1.845 2.733 3.116

44 0.995 1.488 1.818 2.694 3.071

45 0.980 1.466 1.792 2.654 3.025

46 0.966 1.444 1.765 2.614 2.980

47 0.951 1.423 1.738 2.574 2.935

48 0.936 1.401 1.711 2.534 2.889

49 0.922 1.379 1.684 2.495 2.844

50 0.907 1.357 1.657 2.455 2.799

51 0.892 1.335 1.630 2.415 2.753

52 0.878 1.313 1.604 2.375 2.708

53 0.863 1.291 1.577 2.336 2.663

54 0.848 1.269 1.550 2.296 2.617

55 0.833 1.247 1.523 2.256 2.572

56 0.819 1.225 1.496 2.216 2.527

57 0.804 1.203 1.469 2.177 2.481

58 0.789 1.181 1.443 2.137 2.436

59 0.775 1.159 1.416 2.097 2.391

60 0.760 1.137 1.389 2.057 2.345

Notes:

Intensities calculated per CCRFCD Section 500

Return

Period

Precip

Ratios 1 Depth

Adj

Depths

Sloan Canyon Visitor Center BY: DH

Proposed Composite C and Imperviousness DATE: 6/22/2021

CHECKED BY: JH

DATE: 6/22/2021

Sub-Basin Data

Basin ID Description

Total

Area (ac) C10 C100 I(%) C10 C100

I(%)

Area

(ac) C10 C100 I(%)

Area

(ac) C10 C100 I(%)

Area

(ac) C10 C100 I(%)

Area

(ac)

0.90 0.93 100.00 0.88 0.89 95.00 0.85 0.87 90.00 0.25 0.50 0.00

A1 Design Point 1 0.89 0.69 0.79 67.7 0.90 0.93 100.00 0.46 0.88 0.89 95.00 0.13 0.85 0.87 90.00 0.03 0.25 0.50 0.00 0.28

A2 Design Point 2 0.70 0.85 0.89 91.5 0.90 0.93 100.00 0.47 0.88 0.89 95.00 0.17 0.85 0.87 90.00 0.25 0.50 0.00 0.05

A3 Design Point 3 0.86 0.54 0.69 44.7 0.90 0.93 100.00 0.32 0.88 0.89 95.00 0.07 0.85 0.87 90.00 0.25 0.50 0.00 0.47

A4 Design Point 4 0.31 0.59 0.71 50.5 0.90 0.93 100.00 0.88 0.89 95.00 0.12 0.85 0.87 90.00 0.04 0.25 0.50 0.00 0.14

B1 Design Point 5 0.23 0.90 0.93 100.0 0.90 0.93 100.00 0.23 0.88 0.89 95.00 0.85 0.87 90.00 0.25 0.50 0.00

C1 Design Point 6 0.79 0.31 0.54 9.6 0.90 0.93 100.00 0.88 0.89 95.00 0.08 0.85 0.87 90.00 0.25 0.50 0.00 0.71

OS1 Design Point 7 1.96 0.25 0.50 0.0 0.90 0.93 100.00 0.88 0.89 95.00 0.85 0.87 90.00 0.25 0.50 0.00 1.96

OS2 0.48 0.25 0.50 0.0 0.90 0.93 100.00 0.88 0.89 95.00 0.85 0.87 90.00 0.25 0.50 0.00 0.48

Pond Project Total 2.76 0.67 0.77 64.6 0.90 0.93 100.00 1.25 0.88 0.89 95.00 0.50 0.85 0.87 90.00 0.07 0.25 0.50 0.00 0.94

Total Project Total 6.23 0.47 0.64 33.5 0.90 0.93 100.00 1.48 0.88 0.89 95.00 0.57 0.85 0.87 90.00 0.07 0.25 0.50 0.00 4.10

Notes:

Percent Imperviousness, I(%) is from CCRFCD Table 601

C5 is from CCRFCD Table 601

C10 is from CCRFCD Table 601

Composite C & I Paved Roads Drives and Walks Roofs Undeveloped Areas

Sloan Canyon Visitor Center DATE: 6/22/2021

Time of Concentration JH

6/22/2021

Tc

C10

L1

(ft)

S

Ti

(min)

LTotal

(ft)

L2

(ft)

Sw

(ft/ft)

V

(ft/s)

Tt

(min)

Ti+Tt

(min)

A1 0.89 0.69 440 4.0 9.8 640 200 0.020 2.8 1.2 11.0

A2 0.70 0.85 350 4.0 5.3 550 200 0.020 2.8 1.2 6.5

A3 0.86 0.54 10 2.0 2.5 45 35 0.020 2.8 0.2 5.0

A4 0.31 0.90 25 2.0 1.4 100 75 0.030 3.5 0.4 5.0

B1 0.23 0.90 5 4.0 0.5 225 220 0.020 2.8 1.3 5.0

C1 0.79 0.31 275 4.0 14.9 475 200 0.020 2.8 1.2 16.1

OS1 1.96 0.25 50 10.0 5.1 100 50 0.020 2.8 0.3 5.4

OS2 0.48 0.25 50 10.0 5.1 100 50 0.020 2.8 0.3 5.4

Average basin slope calculated from site topographic mapping

CCRFCD Hydrologic Criteria and Drainage Design Manual (Eq 602)

CCRFCD Hydrologic Criteria and Drainage Design Manual (Fig 602)

Length / Velocity

Summation of Initial Overland Time and Travel Time (minimum 5 min)

CHECKED BY:

DATE:

INITIAL / OVERLAND TIME (Ti) OVERLAND TRAVEL TIME (Tt)

BASIN ID

AREA

(acre)

P:\AE\B\BLMNS\148049\99 Civil and Survey\5-final-dsgn\50-final-dsgn\10-Civil\Drainage\Sloan RationalPR.xlsx 3 of 4

Sloan Canyon Visitor Center DATE: 6/22/2021

Flow Rates for the 10-Year and 100-Year Storm Events CHECKED BY: JH

DATE: 6/22/2021

BASIN ID

AREA

(acre) C10 C100

I10

(in/hr)

I100

(in/hr)

Q10

(cfs)

Q100

(cfs)

A1 0.89 0.69 0.79 3.63 6.14 1.12 2.16

A2 0.70 0.85 0.89 4.50 7.61 1.33 2.36

A3 0.86 0.54 0.69 4.83 8.16 1.12 2.42

A4 0.31 0.59 0.71 4.83 8.16 0.44 0.89

B1 0.23 0.90 0.93 4.83 8.16 0.50 0.88

C1 0.79 0.31 0.54 3.09 5.23 0.38 1.11

OS1 1.96 0.25 0.50 4.76 8.03 1.17 3.94

OS2 0.48 0.25 0.50 4.76 8.03 0.29 0.97

Q=KCIA where K is a local adjustment factor. K = 0.5 for the CCRFCD area per CCRFCD Criteria Manual Section 604 Time-Intensity-Frequency Curve with Tc used to determine Intensities

P:\AE\B\BLMNS\148049\99 Civil and Survey\5-final-dsgn\50-final-dsgn\10-Civil\Drainage\Sloan RationalPR.xlsx 4 of 4

SLOAN CANYON POND CALCULATIONS BY: DH

DATE: 5/22/2019

WQCV CALCULATIONS CHECKED BY: SJ

DATE: 5/22/2019

i A a C P6 Po V

(%/100) (acres) unitless (in.) (in.) (in.) (acre-ft)

Total (A1+A2+A3+A4) 0.646 2.76 1.299 0.446 0.370 0.214 0.049

WQCV Volume = 0.049 acre-ft

100-YEAR DETENTION CALCULATIONS

tc Q V V

(min) (cfs) (ft ) (acre-ft)

Total (A1+A2+A3+A4) 16.7 7.84 7855.680 0.180

100-Year Detention Volume = 0.180 acre-ft

Basin

Basin

From CCRFCD Criteria Maunal Section 1207.1

C= 0.858i3-0.78i2+0.774i +0.04

Po=(a x C)*P6

WQCV: Water quality capture volume (watershed in.)

i: Impervious (%/100) a: constant, for event maximization, drain times 24 hours

C= runoff cofficient

From CCRFCD Criteria Maunal Section 1203.1.2

V=60(tc*Q)

V: Detention Volume ft2 tc: Time of concentration in minutes

P:\AE\B\BLMNS\148049\99 Civil and Survey\5-final-dsgn\50-final-dsgn\10-Civil\Drainage\Sloan Pond Volumes 20201002.xlsx

Project:

Basin ID:

Depth Increment = 0.50 ft

Watershed Information Top of Micropool -- 0.00 -- -- -- 0 0.000

Selected BMP Type = EDB 0 -- 0.50 -- -- -- 1,645 0.038 411 0.009

Watershed Area = 2.76 acres 0 -- 1.00 -- -- -- 2,923 0.067 1,553 0.036

Watershed Length = 640 ft 0 -- 1.50 -- -- -- 3,361 0.077 3,124 0.072

Watershed Length to Centroid = 280 ft 0 -- 2.00 -- -- -- 3,799 0.087 4,914 0.113

Watershed Slope = 0.035 ft/ft 0 -- 2.50 -- -- -- 4,390 0.101 6,961 0.160

Watershed Imperviousness = 33.50% percent 0 -- 3.00 -- -- -- 4,981 0.114 9,304 0.214

Percentage Hydrologic Soil Group A = 0.0% percent 0 -- 3.50 -- -- -- 5,643 0.130 11,960 0.275

Percentage Hydrologic Soil Group B = 0.0% percent 0 -- 4.00 -- -- -- 6,304 0.145 14,947 0.343

Percentage Hydrologic Soil Groups C/D = 100.0% percent 0 -- 4.50 -- -- -- 7,033 0.161 18,281 0.420

Target WQCV Drain Time = 40.0 hours 0 -- 5.00 -- -- -- 7,761 0.178 21,980 0.505

Location for 1-hr Rainfall Depths = User Input 0 -- 5.50 -- -- -- 9,872 0.227 26,388 0.606

0 -- 7.00 -- -- -- 14,332 0.329 44,541 1.023

Optional User Overrides -- -- -- --

Water Quality Capture Volume (WQCV) = 0.049 acre-feet 0.049 acre-feet -- -- -- --

Excess Urban Runoff Volume (EURV) = 0.085 acre-feet acre-feet -- -- -- --

2-yr Runoff Volume (P1 = 0.76 in.) = 0.046 acre-feet 0.76 inches -- -- -- --

5-yr Runoff Volume (P1 = 1.14 in.) = 0.096 acre-feet 1.14 inches -- -- -- --

10-yr Runoff Volume (P1 = 1.39 in.) = 0.143 acre-feet 1.39 inches -- -- -- --

25-yr Runoff Volume (P1 = 1.74 in.) = 0.232 acre-feet 1.74 inches -- -- -- --

50-yr Runoff Volume (P1 = 2.06 in.) = 0.304 acre-feet 2.06 inches -- -- -- --

100-yr Runoff Volume (P1 = 2.35 in.) = 0.381 acre-feet 2.35 inches -- -- -- --

500-yr Runoff Volume (P1 = 3.14 in.) = 0.566 acre-feet inches -- -- -- --

Approximate 2-yr Detention Volume = 0.047 acre-feet -- -- -- --

Approximate 5-yr Detention Volume = 0.091 acre-feet -- -- -- --

Approximate 10-yr Detention Volume = 0.109 acre-feet -- -- -- --

Approximate 25-yr Detention Volume = 0.133 acre-feet -- -- -- --

Approximate 50-yr Detention Volume = 0.146 acre-feet -- -- -- --

Approximate 100-yr Detention Volume = 0.180 acre-feet -- -- -- --

Define Zones and Basin Geometry -- -- -- --

Zone 1 Volume (WQCV) = 0.049 acre-feet -- -- -- --

Zone 2 Volume (10-year - Zone 1) = 0.060 acre-feet -- -- -- --

Zone 3 Volume (100-year - Zones 1 & 2) = 0.071 acre-feet -- -- -- --

Total Detention Basin Volume = 0.180 acre-feet -- -- -- --

Initial Surcharge Volume (ISV) = user ft 3 -- -- -- --

Initial Surcharge Depth (ISD) = user ft -- -- -- --

Total Available Detention Depth (Htotal) = user ft -- -- -- --

Depth of Trickle Channel (HTC) = user ft -- -- -- --

Slope of Trickle Channel (STC) = user ft/ft -- -- -- --

Slopes of Main Basin Sides (Smain) = user H:V -- -- -- --

Basin Length-to-Width Ratio (RL/W) = user -- -- -- --

Initial Surcharge Area (AISV) = user ft 2 -- -- -- --

Surcharge Volume Length (LISV) = user ft -- -- -- --

Surcharge Volume Width (WISV) = user ft -- -- -- --

Depth of Basin Floor (HFLOOR) = user ft -- -- -- --

Length of Basin Floor (LFLOOR) = user ft -- -- -- --

Width of Basin Floor (WFLOOR) = user ft -- -- -- --

Area of Basin Floor (AFLOOR) = user ft 2 -- -- -- --

Volume of Basin Floor (VFLOOR) = user ft 3 -- -- -- --

Depth of Main Basin (HMAIN) = user ft -- -- -- --

Length of Main Basin (LMAIN) = user ft -- -- -- --

Width of Main Basin (WMAIN) = user ft -- -- -- --

Area of Main Basin (AMAIN) = user ft 2 -- -- -- --

Volume of Main Basin (VMAIN) = user ft 3 -- -- -- --

Calculated Total Basin Volume (Vtotal) = user acre-feet -- -- -- --

DETENTION BASIN STAGE-STORAGE TABLE BUILDER

Optional

Override

Area (ft 2)

Length

(ft)

Optional

Override

Stage (ft)

Stage

(ft)

Stage - Storage

Description

Area

(ft 2)

Width

(ft)

Sloan Canyon Visitor Center Detention Pond

MHFD-Detention, Version 4.03 (May 2020)

Volume

(ft 3)

Volume

(ac-ft)

Area

(acre)

After providing required inputs above including 1-hour rainfall depths, click 'Run CUHP' to generate runoff hydrographs using the embedded Colorado Urban Hydrograph Procedure.

Example Zone Configuration (Retention Pond)

MHFD-Detention_v4 03.xlsm, Basin 6/23/2021, 10:28 AM

1 User Defined Stage-Area Booleans for Message

1 Equal Stage-Area Inputs Watershed L:W

1 CountA Watershed Lc:L

Watershed Slope

0 Calc_S_TC Booleans for CUHP

1 CUHP Inputs Complete

H_FLOOR 1 CUHP Results Calculated

L_FLOOR_OTHER

0.00 ISV 0.00 ISV

0.00 Floor 0.00 Floor

1.20 Zone 1 (WQCV) 1.20 Zone 1 (WQCV)

1.96 Zone 2 (10-year) 1.96 Zone 2 (10-year)

2.70 Zone 3 (100-year) 2.70 Zone 3 (100-year)

DETENTION BASIN STAGE-STORAGE TABLE BUILDER

MHFD-Detention, Version 4.03 (May 2020)

0.000

0.260

0.520

0.780

1.040

0.000

0.085

0.170

0.255

0.340

0.00 2.00 4.00 6.00 8.00

V o lu m e a c-ft

A re a a cr e s)

Stage (ft.)

Area (acres) Volume (ac-ft)

10800

14400

0.00 2.00 4.00 6.00 8.00

A re a sq .f t.

Le n g th

, W id th ft

Stage (ft)

Length (ft) Width (ft) Area (sq.ft.)

MHFD-Detention_v4 03.xlsm, Basin 6/23/2021, 10:28 AM

Project:

Basin ID:

Estimated Estimated

Stage (ft) Volume (ac-ft) Outlet Type

Zone 1 (WQCV) 1.20 0.049 Orifice Plate

Zone 2 (10-year) 1.96 0.060 Rectangular Orifice

Zone 3 (100-year) 2.70 0.071 Weir&Pipe (Restrict)

Total (all zones) 0.180

User Input: Orifice at Underdrain Outlet (typically used to drain WQCV in a Filtration BMP) Calculated Parameters for Underdrain

Underdrain Orifice Invert Depth = N/A ft (distance below the filtration media surface) Underdrain Orifice Area = N/A ft

Underdrain Orifice Diameter = N/A inches Underdrain Orifice Centroid = N/A feet

User Input: Orifice Plate with one or more orifices or Elliptical Slot Weir (typically used to drain WQCV and/or EURV in a sedimentation BMP) Calculated Parameters for Plate

Invert of Lowest Orifice = 0.00 ft (relative to basin bottom at Stage = 0 ft) WQ Orifice Area per Row = 2.292E-03 ft

Depth at top of Zone using Orifice Plate = 1.20 ft (relative to basin bottom at Stage = 0 ft) Elliptical Half-Width = N/A feet

Orifice Plate: Orifice Vertical Spacing = N/A inches Elliptical Slot Centroid = N/A feet

Orifice Plate: Orifice Area per Row = 0.33 sq. inches (diameter = 5/8 inch) Elliptical Slot Area = N/A ft

User Input: Stage and Total Area of Each Orifice Row (numbered from lowest to highest)

Row 1 (required) Row 2 (optional) Row 3 (optional) Row 4 (optional) Row 5 (optional) Row 6 (optional) Row 7 (optional) Row 8 (optional)

Stage of Orifice Centroid (ft) 0.00 0.40 0.80

Orifice Area (sq. inches) 0.33 0.33 0.33

Row 9 (optional) Row 10 (optional) Row 11 (optional) Row 12 (optional) Row 13 (optional) Row 14 (optional) Row 15 (optional) Row 16 (optional)

Stage of Orifice Centroid (ft)

Orifice Area (sq. inches)

User Input: Vertical Orifice (Circular or Rectangular) Calculated Parameters for Vertical Orifice

Zone 2 Rectangular Not Selected Zone 2 Rectangular Not Selected

Invert of Vertical Orifice = 1.20 N/A ft (relative to basin bottom at Stage = 0 ft) Vertical Orifice Area = 0.17 N/A

Depth at top of Zone using Vertical Orifice = 1.96 N/A ft (relative to basin bottom at Stage = 0 ft) Vertical Orifice Centroid = 0.08 N/A

Vertical Orifice Height = 2.00 N/A inches

Vertical Orifice Width = 12.00 inches

User Input: Overflow Weir (Dropbox with Flat or Sloped Grate and Outlet Pipe OR Rectangular/Trapezoidal Weir (and No Outlet Pipe) Calculated Parameters for Overflow Weir grate Zone 3 Weir Not Selected Zone 3 Weir Not Selected

Overflow Weir Front Edge Height, Ho = 1.96 N/A ft (relative to basin bottom at Stage = 0 ft) Height of Grate Upper Edge, Ht = 2.71 N/A

Overflow Weir Front Edge Length = 3.00 N/A feet Overflow Weir Slope Length = 3.09 N/A

Overflow Weir Grate Slope = 4.00 N/A H:V Grate Open Area / 100-yr Orifice Area = 33.54 N/A

Horiz. Length of Weir Sides = 3.00 N/A feet Overflow Grate Open Area w/o Debris = 6.49 N/A

Overflow Grate Open Area % = 70% N/A %, grate open area/total area Overflow Grate Open Area w/ Debris = 3.25 N/A

Debris Clogging % = 50% N/A %

User Input: Outlet Pipe w/ Flow Restriction Plate (Circular Orifice, Restrictor Plate, or Rectangular Orifice) Calculated Parameters for Outlet Pipe w/ Flow Restriction Plate

Zone 3 Restrictor Not Selected Zone 3 Restrictor Not Selected

Depth to Invert of Outlet Pipe = 0.37 N/A ft (distance below basin bottom at Stage = 0 ft) Outlet Orifice Area = 0.19 N/A

Outlet Pipe Diameter = 18.00 N/A inches Outlet Orifice Centroid = 0.15 N/A

Restrictor Plate Height Above Pipe Invert = 3.00 inches Half-Central Angle of Restrictor Plate on Pipe = 0.84 N/A

User Input: Emergency Spillway (Rectangular or Trapezoidal) Calculated Parameters for Spillway

Spillway Invert Stage= 2905.50 ft (relative to basin bottom at Stage = 0 ft) Spillway Design Flow Depth= 0.17 feet

Spillway Crest Length = 20.00 feet Stage at Top of Freeboard = 2906.67 feet

Spillway End Slopes = 15.00 H:V Basin Area at Top of Freeboard = 0.33 acres

Freeboard above Max Water Surface = 1.00 feet Basin Volume at Top of Freeboard = 1.02 acre-ft

Max Ponding Depth of Target Storage Volume = 3.07 feet Discharge at Top of Freeboard = 2.50 cfs

Routed Hydrograph Results

Design Storm Return Period = WQCV EURV 2 Year 5 Year 10 Year 25 Year 50 Year 100 Year

One-Hour Rainfall Depth (in) = N/A N/A 0.76 1.14 1.39 1.74 2.06 2.35

CUHP Runoff Volume (acre-ft) = 0.049 0.085 0.046 0.096 0.143 0.232 0.304 0.381

Inflow Hydrograph Volume (acre-ft) = N/A N/A 0.046 0.096 0.143 0.232 0.304 0.381

CUHP Predevelopment Peak Q (cfs) = N/A N/A 0.0 0.4 0.8 1.9 2.6 3.4 OPTIONAL Override Predevelopment Peak Q (cfs) = N/A N/A

Predevelopment Unit Peak Flow, q (cfs/acre) = N/A N/A 0.01 0.13 0.30 0.69 0.96 1.24

Peak Inflow Q (cfs) = N/A N/A 0.6 1.2 1.8 3.2 4.1 5.0

Peak Outflow Q (cfs) = 0.0 0.5 0.0 0.3 0.6 1.4 1.6 1.7

Ratio Peak Outflow to Predevelopment Q = N/A N/A N/A 1.0 0.7 0.8 0.6 0.5

Structure Controlling Flow = Vertical Orifice 1 Vertical Orifice 1 Plate Vertical Orifice 1 Vertical Orifice 1 Outlet Plate 1 Outlet Plate 1 Outlet Plate 1

Max Velocity through Grate 1 (fps) = N/A N/A N/A N/A N/A 0.1 0.1 0.1

Max Velocity through Grate 2 (fps) = N/A N/A N/A N/A N/A N/A N/A N/A Time to Drain 97% of Inflow Volume (hours) = 38 39 38 40 37 33 31 29

Time to Drain 99% of Inflow Volume (hours) = 41 43 40 44 43 42 41 39

Maximum Ponding Depth (ft) = 1.20 1.67 1.08 1.44 1.72 2.19 2.56 3.07

Area at Maximum Ponding Depth (acres) = 0.07 0.08 0.07 0.08 0.08 0.09 0.10 0.12 Maximum Volume Stored (acre-ft) = 0.049 0.085 0.041 0.066 0.089 0.129 0.166 0.221

The user can override the default CUHP hydrographs and runoff volumes by entering new values in the Inflow Hydrographs table (Columns W through AF).

DETENTION BASIN OUTLET STRUCTURE DESIGN

MHFD-Detention, Version 4.03 (May 2020)

Sloan Canyon Visitor Center Detention Pond

Example Zone Configuration (Retention Pond)

MHFD-Detention_v4 03.xlsm, Outlet Structure 6/23/2021, 10:30 AM

COUNTA for Basin Tab = 1 Ao Dia WQ Plate Type Vert Orifice 1Vert Orifice 2

Count_Underdrain = 0 0.11(diameter = 3/8 inch) 2 3 1

Count_WQPlate = 1 0.14(diameter = 7/16 inch)

Count_VertOrifice1 = 1 0.18(diameter = 1/2 inch) Outlet Plate 1 Outlet Plate 2 Drain Time Message Boolean

Count_VertOrifice2 = 0 0.24(diameter = 9/16 inch) 4 1 5yr, <72hr 0

Count_Weir1 = 1 0.29(diameter = 5/8 inch) >5yr, <120hr 0

Count_Weir2 = 0 0.36(diameter = 11/16 inch) Max Depth Row

Count_OutletPipe1 = 1 0.42(diameter = 3/4 inch) WQCV 121 Watershed Constraint Check

Count_OutletPipe2 = 0 0.50(diameter = 13/16 inch) 2 Year 109 Slope 0.035

COUNTA_2 (Standard FSD Setup)= 1 0.58(diameter = 7/8 inch) EURV 168 Shape 3.41

Hidden Parameters & Calculations 0.67(diameter = 15/16 inch) 5 Year 145

MaxPondDepth_Error? FALSE 0.76 (diameter = 1 inch) 10 Year 173 Spillway Depth

Cd_Broad-Crested Weir 3.00 0.86(diameter = 1-1/16 inches) 25 Year 220 0.17

WQ Plate Flow at 100yr depth = 0.05 0.97(diameter = 1-1/8 inches) 50 Year 257

CLOG #1= 35% 1.08(diameter = 1-3/16 inches) 100 Year 308 1 Z1_Boolean

Cdw #1 = 0.89 1.20(diameter = 1-1/4 inches) 500 Year 410 1 Z2_Boolean

Cdo #1 = 0.69 1.32(diameter = 1-5/16 inches) Zone3_Pulldown Message 1 Z3_Boolean

Overflow Weir #1 Angle = 0.245 1.45(diameter = 1-3/8 inches) 1 Opening Message

CLOG #2= 0% 1.59(diameter = 1-7/16 inches) Draintime Running

Cdw #2 = #VALUE! 1.73(diameter = 1-1/2 inches) Outlet Boolean Outlet Rank Total (1 to 4)

Cdo #2 = #VALUE! 1.88(diameter = 1-9/16 inches) Vertical Orifice 1 1 1 2

Overflow Weir #2 Angle = #VALUE! 2.03(diameter = 1-5/8 inches) Vertical Orifice 2 0 0 Boolean

Underdrain Q at 100yr depth = 0.00…