3539 Drainage Report_2023.12.22.pdf

PREPARED FOR:

The City of Black Hawk

201 SELAK ST., P.O. BOX 68

BLACK HAWK, CO 80422

PRELIMINARY

DRAINAGE REPORT

Gregory Hill Detention Pond Conversion

SECTION 18, TOWNSHIP 3 SOUTH,

RANGE 72 WEST OF THE 6th PRINCIPAL MERIDIAN

CITY BLACK HAWK AND COUNTY OF GILPIN, COLORADO

PREPARED BY:

BASELINE ENGINEERING CORPORATION

112 N. RUBEY DRIVE, SUITE 210

GOLDEN, CO 80403

Revised: September 25, 2023

JOB # CO3539

ENGINEER CERTIFICATION

“This report (plan) for the drainage and water quality design for the “Gregory Hill Detention Pond Conversion,” was prepared by me (or under my direct supervision) in accordance with the provisions of City of Black Hawk and County of Gilpin’s Standards and Specifications and was designed to comply with the provisions thereof.”

Jordan Piaskowy Date:

Registered Professional Engineer

State of Colorado No. 53301

OWNER CERTIFICATION

“The City of Black Hawk hereby certifies that the drainage facilities for the “Gregory Hill Detention Pond Conversion,” will be constructed according to the design presented in this report.”

(Owner/Applicant): _______

By: __________________________________________

Date:

Table of Contents

A. Introduction:

B. Existing Drainage System:

C. Proposed (Developed) Drainage System:

D. Right-of-way Requirements:

E. Maintenance:

F. Analysis of Upstream and Downstream Effect:

G. Conclusions:

H. References:

I. APPENDIX

VICINITY & FEMA FIRM MAP

HYDROLOGICAL COMPUTATIONS

HYDRAULIC COMPUTATIONS

DRAINAGE DETAILS & PLANS

A. Introduction:

1. Site Location

a) Township, Range, Section, ¼ Section: The subject property is located in Section 18, Township 3 South, Range 72 West of the 6th Principal Meridian, City of Black Hawk and County of Gilpin, State of Colorado.

b) Major drainageways, facilities and easements within and adjacent to the site:

The detention pond outlet eventually outfalls to Lake Gulch in the existing condition and will continue to in the proposed condition.

c) Description of surroundings: The site is surrounded by a sand shed facility and Transportation Avenue to the west, the parking lot for the City of Black Hawk Public Works Department to the north, the parking lot for the City of Black Hawk Police Annex to the north and east and an undeveloped, steep slope terminating in woodlands to the south.

2. Site Description

a) Acreage: The limits of construction for this project will encompass 3.93 acres; the limits of disturbance for this project will be 2.96 acres.

b) Ground Cover: Existing ground cover consists of native vegetation of grasses, weeds, and trees. There are also existing drainage structures that will be removed during the demolition phase of this project.

c) Discussion of how site characteristics (soil, vegetation, erodibility) shall influence both wind and water erosion: The current site conditions prevent wind and water erosion since there is native grasses across the site. In the proposed development the wind and water erosion will be prevented through the use of established vegetation, slopes 3:1 or flatter and the placement of pavement over the majority of the site.

3. Existing drainage facilities, major channels, flood hazard zones, irrigation ditches, location of wetlands

In the existing condition the site acts as an above ground detention pond with water quality treatment. The site detains and treats water from the various impervious areas as described in section A.1.c.

Approximately 250 feet downstream of the site is Lake Gulch. Lake Gulch has a floodplain associated with it. However, this project is well outside of the floodplain limits.

4. Proposed project description

The proposed Gregory Hill Detention Pond Conversion development will consist of approximately 2.96 acres of disturbed area. The site is located within the NW quarter of

Section 18, Township 3 South, Range 72 West, in the City of Black Hawk and County of

Gilpin, Colorado. The development includes the creation of an underground detention facility that will detain and treat the storm water from the same areas as the existing above ground detention facility, along with the storm drain system necessary to capture those flows.

5. Drainage study relevant to site

The Miner’s Mesa Maintenance Facility Final Drainage Report (Reference 1) was referenced in the proposed design of this site. This is the study that was performed to design the existing, above ground detention pond.

6. Required and existing rights-of-way for drainage easements and detention areas

The proposed underground detention facility and drainage system will be located within the footprint of the existing detention facility and drainage system. For this reason, no additional right of way or easements will be required for this project.

B. Existing Drainage System:

1. Major Basin

Relationship to major basin channel: The proposed Gregory Hill Detention Pond Conversion eventually outfalls to Lake Gulch (Illinois Gulch on FIRM panel 0800750136D).

Lake Gulch consists of a tree-lined drainageway that eventually outfalls to Russel Gulch.

The proposed project will not increase the major or minor storm peak flows leaving the site, therefore this project will not negatively impact Lake Gulch.

2. Sub-Basin Description and Site Drainage

The existing and proposed basins are shown listed in Table 1. These basins drain to the existing pond and will drain to proposed underground pond. In the existing conditions the area of the pond itself is lined with natural grasses.

The delineation for the Police Annex in the existing conditions ends at the edge of the parking lot. This basin is increased to include the grassy area between the parking lot and the proposed storage area in order to properly design the FES that will drain the swale that empties the parking lot and the grassy area.

C. Proposed (Developed) Drainage System:

1. Sub-Basins

a) Size of basin and subbasin: The proposed conditions have been delineated into 9 basins that are shown in Figure 1. The first 5 basins are existing basins.

i. Basin Bus Barn: This basin is located on the west side of Transportation Avenue. This basin includes the storage garage and its parking lot. This basin drains to a detention pond along its eastern edge before being conveyed through an 18” RCP to the existing pond. In the proposed condition this 18” RCP will be cut and connected to the Type R inlet that will collect runoff from the Transportation Avenue basin and convey it via storm sewer to the underground detention facility. This basin drains to design point BB.

ii. Basin Police Annex: This basin is located on the northeastern aspect of the site and consists of the Police Annex building, its parking lot and the grassy area with swale between the parking lot and the proposed storage area. The Police Annex basin was increased in order to properly design the flared end section that will drain that area. This basin drains to design point PA.

iii. Basin Public Works: This basin is located on the northern aspect of the site and consists of the Public Works building and its parking lot. This basin is drained by a storm sewer system that outfalls to the above ground pond in the existing condition. This existing storm sewer will outfall to the underground detention pond by removing the existing flared end section and connecting the remaining storm pipe directly to the pond inlet. This basin drains to design point PW.

iv. Basin Sand Shed: This basin is located on the southwestern aspect of the site and consists of the sand shed, the paved areas around the sand shed, the grassy areas around the paved areas, the storage area west of the sand shed and the gravel road connecting the storage area to Transportation Avenue.

The Sand Shed basin, in the existing condition, sheet flows to the end of Transportation Avenue and then down Gregory Hill. This basin drains to design point SS.

v. Basin Transportation Avenue: This basin is located on the western aspect of the site and consists of the north and east portions of Transportation Avenue.

In the proposed condition this basin will continue to drain through a curb cut on the east side of Transportation Avenue, down a riprap rundown and the flows will be captured in an existing grate inlet. This basin drains to design point TA.

vi. Basins New Storage 1-3: These basins are the paved areas that will be constructed on top of the proposed underground detention pond. The flows from these basins will be collected in grate inlets. These basins drain to design points NS1, NS2, and NS3.

vii. Basin Roadway: This basin includes the newly built roundabout and future link roadway that drains to the newly constructed storm sewer system that connects to the existing swale in the bus barn basin. This runoff will make its way into the underground detention pond.

Table 1 Drainage Basins

RUNOFF SUMMARY

BASIN

LABEL

DESIGN

POINT

AREA Imp. C10 C100

LOCAL

(CFS) Notes

Q10 Q100

BB BB 2.78 0.64 0.61 0.75 4.7 8.7 Bus Barn

PA PA 1.53 0.92 0.8 0.9 3.0 4.9 Police Annex

PW PW 3.01 0.87 0.8 0.8 5.5 9.0 Public Works

SS SS 3.20 0.67 0.6 0.8 5.3 9.8 Sand Shed

TA TA 1.00 0.63 0.6 0.7 1.5 2.8 Transportation Ave

NS1 NS1 0.38 0.54 0.5 0.7 0.7 1.4 New Storage 1

NS2 NS2 0.58 0.83 0.7 0.8 1.3 2.2 New Storage 2

NS3 NS3 0.43 0.84 0.8 0.8 1.1 1.9 New Storage 3

RD RD 7.01 0.19 0.3 0.6 5.8 18.1 Roadway

Figure 1 Drainage Basins

b) Hydrologic Method: The Rational Method was utilized for calculating the runoff.

This method is valid for basins up to 90 acres in size per the MHFD Criteria Manual (Reference 2).

c) Design Storm Frequencies: The major storm event is the 100-year storm while the minor year event is the 10-year storm per the Gilpin County Standards and Specifications for Design and Construction, Reference 3.

2. Stormwater Detention and Quality

a) Volumes required and provided for major and minor storm events: The required minor and major volumes were calculated per the MHFD Criteria. The minor volume will be the 10-year volume and the major volume will be the 100-year volume. The aforementioned design volumes follow the full spectrum detention design per the MHFD Criteria. The Table 2 below summarizes the required and provided volumes for the detention ponds. More detailed calculations are included in Appendix 3.

Table 2 Detention Volumes

Detention Classification Volume [ac-ft]

Water Quality Capture Volume (WQCV) 0.366

Minor Storm (10-year) 0.552

Major Storm (100-year) 0.290

Total Detention Volume 1.207

b) Release rates and method of release for detention classification: Per the MHFD Criteria the release rate of 0.2 cfs for the water quality capture volume will result in a 51-hour drain time and the release rate of 16.3 cfs for the 100-year storm will be 90% of the pre-development flows. The minor storm volume will be discharged within a 72-hour drain time. The proposed outlet structures will be within the underground detention facility.

c) Maintenance access for the pond (design and location): Maintenance access will be provided through manholes. The locations and details of the access manholes can be found on the Pond Plans in Appendix 4.

D. Right-of-way Requirements:

1. Boundary All drainage improvements will be contained within the property boundaries.

2. Present and Future Ownership The properties are currently owned by the City of Black Hawk.

E. Maintenance:

1. Post Construction Stormwater Quality Features

The underground detention will serve as the post-construction BMP for the site.

2. Maintenance Schedule & Responsibility

Maintenance during construction will be performed by the General Contractor or his designee. Inspections on construction BMPs should be performed every 14 days and immediately following storm events. An inspection report shall be prepared for each inspection. Maintenance shall be performed as identified in the inspection report.

Once construction is complete, the owner or private entity will be responsible for maintenance of the Post Construction BMP. The underground detention pond should be inspected at least twice annually to observe the amount of sediment in the isolator rows and debris at the outlet and inlet structures.

• Debris and litter should be removed from the detention area to minimize clogging of the outlet.

• Remove sediment via pump truck.

• Remove sediment from the bottom of pond when it has accumulated about

20% of the water quality design volume.

F. Analysis of Upstream and Downstream Effect:

No negative effects will occur because of this development. Changes in flow depth and erosion rates shall be minimal for all downstream parcels and/or drainageways.

The detention pond has been designed per the MHFD criteria and will release below historic rates and within the required time periods for specific storm events. The detention pond will drain the WQCV within 52 hours, the 10-year volume within the required 72 hours per State law, and will release the 100-year volume at 90% of the pre-development flow. This design ensures the peak discharges to downstream areas for all storm events will be below the pre-development conditions. There will be no effect on the upstream properties due to the development of this site.

G. Conclusions:

The proposed development will ensure runoff from the site is comparable to the pre-development runoff using the proposed underground detention pond.

H. References:

1. Miner’s Mesa Maintenance Facility Final Drainage Report; Anderson & Hastings Consultants, Inc., November 28, 2011.

2. Urban Storm Drainage Criteria Manual, Volumes 1-3; Mile High Flood District, Denver, CO, June 2001 (Updated January 2021).

3. Gilpin County Standards and Specifications for Design and Construction, First Edition, Gilpin County, October 2020.

4. FIRM 08047C0136D – Federal Emergency Management Agency, April 6, 2022.

I. APPENDIX

1. VICINITY & FEMA FIRM MAP

Source: Esri, Maxar, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AeroGRID, IGN, and the GIS User Community, Esri, HERE, Garmin, (c) OpenStreetMap contributors, and the GIS user community

Gregory Hill Underground Detention Facility

Vicinity Map

0 0.065 0.130.0325

Miles

Project Location

Sources: Esri, HERE, Garmin, USGS, Intermap, INCREMENT P, NRCan, Esri Japan, METI, Esri China (Hong Kong), Esri Korea, Esri

Project Location matt.jones Oval matt.jones Callout Project Location

2. HYDROLOGICAL COMPUTATIONS

matt.jones Rectangle

Know what's below.

before you dig.CallR

= FORMULA CELLS

= USER INPUT CELLS

PROJECT:

JOB NO.:

CALC. BY: �▼

DATE:

Minutes

Equation 5-1 I=(28.5*P1)/(10+Td) ^0.786

I = rainfall intensity (inches per hour)

P1 = 1-hour point rainfall depth (inches)

Td = storm duration (minutes)

Reference:

1) Urban Drainage and Flood Control District - Urban Storm Drainage Criteria Manual Volume 1, 2017

2) NOAA Atlas 14, Volume 8, Version 2 http://hdsc.nws.noaa.gov/hdsc/pfds/pfds_map_cont.html?bkmrk=co

1.04 1.58

5.36

4.27

3.11

2.48

2.08

1.80

3.53

2.81

2.05

1.63

1.37

1.19

1.05

User Input

Project Location

P1: 1-hour Rainfall Depths (inches)

BH Detention Conversion

MNJ

9/25/2023

IDF Rainfall Data

10-Year

Minor Storm Major Storm Td 100-Year

0.980.65

1.60

Baseline Engineering, Planning and Surveying

9/25/2023

CO3539-Drainage Calcs.xlsx http://hdsc.nws.noaa.gov/hdsc/pfds/pfds_map_cont.html?bkmrk=co

PROJECT:

JOB NO.:

CALC. BY:

DATE:

Impervious Percentages - from Urban Drainage Table 6-3

Paved 100% 0

Roofs 90% 0

Greenbelts, agricultural 2% 0

Gravel

(packed) 40% 0

SOIL TYPE: C or D q (use equation from Table 6-4) = FORMULA CELLS

= USER INPUT CELLS

Basin Area (ac) Imp. C2 C5 C10 C100 Paved Roofs Greenbelts, agricultural

Gravel

(packed) Land Use Land Use Land Use Land Use

BB 2.78 64% 0.51 0.56 0.61 0.75 1.49 0.31 0.98

PA 1.53 92% 0.75 0.79 0.81 0.86 1.29 0.12 0.12

PW 3.01 87% 0.71 0.75 0.78 0.84 2.07 0.60 0.34

SS 3.20 67% 0.53 0.58 0.62 0.76 1.37 0.19 0.18 1.46

TA 1.00 63% 0.49 0.55 0.60 0.74 0.62 0.38

NS1 0.38 54% 0.41 0.47 0.53 0.70 0.20 0.18

NS2 0.58 83% 0.67 0.72 0.75 0.82 0.48 0.10

NS3 0.43 84% 0.68 0.72 0.75 0.83 0.36 0.07

RD 7.01 19% 0.13 0.19 0.28 0.56 1.23 5.75 0.03

Total 19.92 55% 0.42 0.49 0.54 0.71 9.11 1.22 8.10 1.49

Weighted Impervious and C Values Areas (ac)

Land Use

Land Use

Land Use

Land Use

PROPOSED COMPOSITE IMPERVIOUSNESS

BH Detention Conversion

MNJ

9/25/2023

Baseline Engineering, Planning and Surveying COMPOSITE C VALUES - PROP 9/25/2023

Project: BH Detention Conversion

Job No.: 3539

Calculated By: Checked By: LRM

Date:

FINAL REMARKS

tc

Basin i C5 AREA LENGTH SLOPE ti LENGTH SLOPE VEL. tt COMP. TOT. LENGTH So

Ac Ft % Min Ft % FPS Min tc Ft % Min Min

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16)

BB 0.64 0.56 2.78 300 5.6 9.52 289 20 5.6 4.73 1.02 10.5 589 5.60 17.4 10.54

PA 0.92 0.79 1.53 300 0.8 10.59 356 20 0.8 1.8 3.3 13.9 656 0.80 16.0 13.9

PW 0.87 0.75 3.01 300 0.7 12.39 293 20 0.7 1.7 2.9 15.3 593 0.70 16.8 15.3

SS 0.67 0.58 3.20 300 4.0 10.28 310 20 4.0 4.0 1.3 11.6 610 4.00 17.5 11.6

TA 0.63 0.55 1.00 300 2.2 13.27 19 20 2.2 3.0 0.1 13.4 319 2.20 17.3 13.4

NS1 0.54 0.47 0.38 33 16.2 2.59 96 20 1.0 2.0 0.8 3.4 129 4.89 17.5 5.0

NS2 0.83 0.72 0.58 131 0.8 8.53 131 0.80 13.1 8.5

NS3 0.84 0.72 0.43 60 11.6 2.34 58 20 5.2 4.6 0.2 2.6 118 8.45 12.0 5.0

RD 0.19 0.19 7.01 60 15.0 5.18 914 15 11.0 5.0 3.1 8.2 974 11.25 26.8 8.2

Equation 6-3 ti=((0.395(1.1-C5)SQRT(L))/(So^0.33))

Equation 6-5 tc=(26-17i)+(Lt/(60(14i+9)SQRT(So))) = FORMULA CELLS

= USER INPUT CELLS

NRCS Conveyance Factor K Table - Cv Value

20Paved Areas and Shallow Paved Swales

Short Pasture and Lawns

Nearly Bare Ground

Grassed Waterway

Heavy Meadow 2.5

Tillage/Field 5

STANDARD FORM SF-2

INITIAL/OVERLAND

TIME (ti)

MNJ

DATA

SUB-BASIN

9/25/2023 tc (Equation 6-5)

TIME OF CONCENTRATION SUMMARY

tc CHECK

(URBANIZED BASINS)

TRAVEL TIME

(tt)

Cv

Baseline Engineering, Planning and Surveying TOC

Calculated By: Project: BH Detention Conversion

Date: Job No.: 3539

Checked By: Design Storm: 10-Year

= FORMULA CELLS

= USER INPUT CELLS

D E

S

IG

N

P O

IN

T

A R

E A

(A C

R U

N O

F

E F

F t c

(M

IN

C

I

(I

/H R

Q

(C

S t c

S

C

/H R

S

(2) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (19) (20) (21) (22)

BB BB 2.78 0.61 10.5 1.69 2.76 4.7

PA PA 1.53 0.81 13.9 1.24 2.45 3.0

PW PW 3.01 0.78 15.3 2.33 2.34 5.5

SS SS 3.20 0.62 11.6 2.00 2.65 5.3

TA TA 1.00 0.60 13.4 0.60 2.49 1.5

NS1 NS1 0.38 0.53 5.0 0.20 3.53 0.7

NS2 NS2 0.58 0.75 8.5 0.43 2.99 1.3

NS3 NS3 0.43 0.75 5.0 0.32 3.53 1.1

RD RD 7.01 0.28 8.2 1.93 3.02 5.8

STANDARD FORM SF-3

STORM DRAINAGE SYSTEM DESIGN

(RATIONAL METHOD PROCEDURE)

MNJ

9/25/2023

LRM

1.04 10-Year

1-hour rainfall=

V E

L O

C

IT

Y

(F

S t t

REMARKSBASIN

DIRECT RUNOFF TOTAL RUNOFF

L E

N G

T H

Baseline Engineering, Planning and Surveying Minor SF-3

Calculated By: Project: BH Detention Conversion

Date: Job No.: 3539

Checked By: Design Storm: 100-Year

= FORMULA CELLS

= USER INPUT CELLS

D E

S

IG

IN

T

A R

D

S

IG

N

A R

R U

N O

E F

F t c

C

/H R

S t c

S

C

/H R

S

(2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (19) (20) (21) (22)

BB BB 2.78 0.75 10.5 2.08 4.19 8.7

PA PA 1.53 0.86 13.9 1.31 3.72 4.9

PW PW 3.01 0.84 15.3 2.53 3.55 9.0

SS SS 3.20 0.76 11.6 2.42 4.03 9.8

TA TA 1.00 0.74 13.4 0.74 3.78 2.8

NS1 NS1 0.38 0.70 5.0 0.27 5.36 1.4

NS2 NS2 0.58 0.82 8.5 0.48 4.54 2.2

NS3 NS3 0.43 0.83 5.0 0.36 5.36 1.9

RD RD 7.01 0.56 8.2 3.95 4.59 18.1

MNJ STANDARD FORM SF-3

STORM DRAINAGE SYSTEM DESIGN

(RATIONAL METHOD PROCEDURE)

BASIN

9/25/2023

LRM

1.58 100-Year

1-hour rainfall=

L E

N G

H

V E

L O

C

IT

Y

S t t

REMARKS

DIRECT RUNOFF TOTAL RUNOFF

Baseline Engineering, Planning and Surveying Major SF-3

CALC. BY:

DATE:

Q10 Q100

BB BB 2.78 0.64 0.61 0.75 4.7 8.7 Bus Barn

PA PA 1.53 0.92 0.8 0.9 3.0 4.9 Police Annex

PW PW 3.01 0.87 0.8 0.8 5.5 9.0 Public Works

SS SS 3.20 0.67 0.6 0.8 5.3 9.8 Sand Shed

TA TA 1.00 0.63 0.6 0.7 1.5 2.8 Transportation Ave

NS1 NS1 0.38 0.54 0.5 0.7 0.7 1.4 New Storage 1

NS2 NS2 0.58 0.83 0.7 0.8 1.3 2.2 New Storage 2

NS3 NS3 0.43 0.84 0.8 0.8 1.1 1.9 New Storage 3

RD RD 7.01 0.19 0.3 0.6 5.8 18.1 Roadway

BH Detention Conversion

MNJ

9/25/2023

Notes

RUNOFF SUMMARY

BASIN

LABEL

AREA

LOCAL

(CFS)DESIGN

POINT

Imp. C10 C100

Baseline Engineering, Planning and Surveying Runoff Summary

3. HYDRAULIC COMPUTATIONS

CALC. BY: = FORMULA CELLS

DATE: = USER INPUT CELLS

Q10 Q100

(cfs) (cfs) Inlet

Capacity

Inlet

Interception

Inlet

Bypass

Inlet

Capacity

Inlet

Interception

Inlet

Bypass

TA EX1 TA 1.5 2.8 Type C 3.8 1.5 0.0 5.4 2.8 0.0

PA C-1 PA 3.0 4.9 FES 5.2 3.0 0.0 5.2 4.9 0.0

NS1 B-1 NS1 0.7 1.4 Type C 7.6 0.7 0.0 7.6 1.4 0.0

NS2 C-2 NS2 1.3 2.2 Type C 7.6 1.3 0.0 7.6 2.2 0.0

NS3 D-1 NS3 1.1 1.9 Type C 7.6 1.1 0.0 7.6 1.9 0.0

Description

10-Year 100-Year

DESCRIPTION

Inlet

No.

DESIGN

POINT

Inlet Type

BH Detention Conversion

MNJ

PROJECT NAME: BH Detention Conversion DATE: 6/8/2022

PROJECT NUMBER: 3539

CALCULATED BY: MNJ

CHECKED BY: LRM

C O = 0.67 g= 32.2

BASIN ID INLET TYPE

UNCLOGGED

OPEN AREA

100‐YR FLOW CLOGGING

CLOGGED

OPEN AREA

PONDING HEAD

REQUIRED

PROVIDED

PONDING DEPTH

PROVIDED INLET

CAPACITY

(SQFT) (CFS) (%) (SQFT) (FT) (FT) (CFS)

NS1 CDOT TYPE C 6.3 1.4 50 3.15 0.01 0.1 5.4

NS2 CDOT TYPE C 6.3 2.2 50 3.15 0.02 0.1 5.4

NS3 CDOT TYPE C 6.3 1.9 50 3.15 0.01 0.1 5.4

PER UDFCD CHAPTER 7 SECTION 3.2.7 VOLUME 1

INLET CAPACITY

PROJECT NAME: BH Detention Conversion DATE: 6/8/2022

PROJECT NUMBER: 3539

CALCULATED BY: MNJ

CHECKED BY: LRM

C O = 0.67 g= 32.2

BASIN ID INLET TYPE

UNCLOGGED

OPEN AREA

100‐YR FLOW CLOGGING

CLOGGED

OPEN AREA

PONDING HEAD

REQUIRED

PROVIDED

PONDING DEPTH

PROVIDED INLET

CAPACITY

(SQFT) (CFS) (%) (SQFT) (FT) (FT) (CFS)

TA CDOT TYPE C 6.3 2.8 50 3.15 0.03 0.1 5.4

PER UDFCD CHAPTER 7 SECTION 3.2.7 VOLUME 1

INLET CAPACITY

Project:

Basin ID:

Depth Increment = ft

Watershed Information Top of Micropool -- 0.00 -- -- -- 6,710 0.154

Selected BMP Type = EDB -- 0.17 -- -- -- 5,555 0.128 1,043 0.024

Watershed Area = 19.92 acres -- 0.33 -- -- -- 6,710 0.154 2,024 0.046

Watershed Length = 990 ft -- 0.50 -- -- -- 5,555 0.128 3,066 0.070

Watershed Length to Centroid = 340 ft -- 0.67 -- -- -- 6,711 0.154 4,109 0.094

Watershed Slope = 0.025 ft/ft -- 0.83 -- -- -- 13,209 0.303 5,702 0.131

Watershed Imperviousness = 55.00% percent -- 1.00 -- -- -- 13,485 0.310 7,971 0.183

Percentage Hydrologic Soil Group A = 0.0% percent -- 1.17 -- -- -- 12,979 0.298 10,221 0.235

Percentage Hydrologic Soil Group B = 0.0% percent -- 1.33 -- -- -- 13,247 0.304 12,319 0.283

Percentage Hydrologic Soil Groups C/D = 100.0% percent -- 1.50 -- -- -- 12,748 0.293 14,528 0.334

Target WQCV Drain Time = 40.0 hours -- 1.67 -- -- -- 13,002 0.298 16,717 0.384

Location for 1-hr Rainfall Depths = User Input -- 1.83 -- -- -- 12,500 0.287 18,757 0.431

-- 2.00 -- -- -- 12,738 0.292 20,903 0.480

-- 2.17 -- -- -- 12,221 0.281 23,024 0.529

Optional User Overrides -- 2.33 -- -- -- 12,439 0.286 24,997 0.574

Water Quality Capture Volume (WQCV) = 0.366 acre-feet acre-feet -- 2.50 -- -- -- 11,902 0.273 27,066 0.621

Excess Urban Runoff Volume (EURV) = 1.044 acre-feet acre-feet -- 2.67 -- -- -- 12,047 0.277 29,102 0.668

2-yr Runoff Volume (P1 = 0.69 in.) = 0.519 acre-feet 0.69 inches -- 2.83 -- -- -- 11,483 0.264 30,984 0.711

5-yr Runoff Volume (P1 = 0.88 in.) = 0.707 acre-feet 0.88 inches -- 3.00 -- -- -- 11,576 0.266 32,944 0.756

10-yr Runoff Volume (P1 = 1.04 in.) = 0.885 acre-feet 1.04 inches -- 3.17 -- -- -- 10,963 0.252 34,860 0.800

25-yr Runoff Volume (P1 = 1.25 in.) = 1.261 acre-feet 1.25 inches -- 3.33 -- -- -- 10,995 0.252 36,616 0.841

50-yr Runoff Volume (P1 = 1.42 in.) = 1.522 acre-feet 1.42 inches -- 3.50 -- -- -- 10,326 0.237 38,429 0.882

100-yr Runoff Volume (P1 = 1.58 in.) = 1.825 acre-feet 1.58 inches -- 3.67 -- -- -- 10,253 0.235 40,178 0.922

500-yr Runoff Volume (P1 = 1.74 in.) = 2.081 acre-feet 1.74 inches -- 3.83 -- -- -- 9,437 0.217 41,753 0.959

Approximate 2-yr Detention Volume = 0.537 acre-feet -- 4.00 -- -- -- 9,108 0.209 43,329 0.995

Approximate 5-yr Detention Volume = 0.794 acre-feet -- 4.17 -- -- -- 7,845 0.180 44,770 1.028

Approximate 10-yr Detention Volume = 0.918 acre-feet -- 4.33 -- -- -- 6,605 0.152 45,926 1.054

Approximate 25-yr Detention Volume = 1.038 acre-feet -- 4.50 -- -- -- 6,653 0.153 47,053 1.080

Approximate 50-yr Detention Volume = 1.084 acre-feet -- 4.67 -- -- -- 5,610 0.129 48,096 1.104

Approximate 100-yr Detention Volume = 1.207 acre-feet -- 4.83 -- -- -- 6,653 0.153 49,077 1.127

-- 5.00 -- -- -- 5,609 0.129 50,119 1.151

Define Zones and Basin Geometry -- 5.17 -- -- -- 6,653 0.153 51,161 1.175

Zone 1 Volume (WQCV) = 0.366 acre-feet -- 5.33 -- -- -- 5,609 0.129 52,142 1.197

Zone 2 Volume (10-year - Zone 1) = 0.552 acre-feet -- 5.50 -- -- -- 6,653 0.153 53,184 1.221

Zone 3 Volume (100-year - Zones 1 & 2) = 0.290 acre-feet -- 5.51 -- -- -- 25 0.001 53,208 1.221

Total Detention Basin Volume = 1.207 acre-feet -- 8.00 -- -- -- 25 0.001 53,270 1.223

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

Length

(ft)

Optional

Override

Stage (ft)

Stage

(ft)

Stage - Storage

Description

Area

(ft

Width

(ft)

Black Hawk PW Underground Detention

HS180

MHFD-Detention, Version 4.06 (July 2022)

Volume

(ft

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_v4-06.xlsm, Basin 9/25/2023, 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

1.61 Zone 1 (WQCV) 1.61 Zone 1 (WQCV)

3.66 Zone 2 (10-year) 3.66 Zone 2 (10-year)

5.41 Zone 3 (100-year) 5.41 Zone 3 (100-year)

DETENTION BASIN STAGE-STORAGE TABLE BUILDER

MHFD-Detention, Version 4.06 (July 2022)

0.000

0.310

0.620

0.930

1.240

0.000

0.080

0.160

0.240

0.320

0.00 2.00 4.00 6.00 8.00

V o lu m e ac -f t)

A re a (a cr e s)

Stage (ft.)

Area (acres) Volume (ac-ft)

10200

13600

0.00 2.00 4.00 6.00 8.00

A re a (s q .f t.

Le n gt h

, W id th ft

Stage (ft)

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

MHFD-Detention_v4-06.xlsm, Basin 9/25/2023, 10:28 AM

Project:

Basin ID:

Estimated Estimated

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

Zone 1 (WQCV) 1.61 0.366 Orifice Plate

Zone 2 (10-year) 3.66 0.552 Circular Orifice

Zone 3 (100-year) 5.41 0.290 Weir&Pipe (Restrict)

Total (all zones) 1.207

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

Centroid of Lowest Orifice = 0.00 ft (relative to basin bottom at Stage = 0 ft) WQ Orifice Area per Row = 2.181E-02 ft

Depth at top of Zone using Orifice Plate = 2.75 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 = 3.14 sq. inches (diameter = 2 inches) 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 1.50

Orifice Area (sq. inches) 3.14 3.14

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 Circular Not Selected Zone 2 Circular Not Selected

Invert of Vertical Orifice = 2.75 N/A ft (relative to basin bottom at Stage = 0 ft) Vertical Orifice Area = 0.44 N/A ft

Depth at top of Zone using Vertical Orifice = 3.66 N/A ft (relative to basin bottom at Stage = 0 ft) Vertical Orifice Centroid = 0.38 N/A feet

Vertical Orifice Diameter = 9.00 N/A 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 = 3.75 N/A ft (relative to basin bottom at Stage = 0 ft) Height of Grate Upper Edge, Ht = 3.75 N/A feet

Overflow Weir Front Edge Length = 4.00 N/A feet Overflow Weir Slope Length = 0.00 N/A feet

Overflow Weir Grate Slope = 0.00 N/A H:V Grate Open Area / 100-yr Orifice Area = N/A N/A

Horiz. Length of Weir Sides = 0.00 N/A feet Overflow Grate Open Area w/o Debris = N/A N/A ft

Overflow Grate Type = N/A N/A Overflow Grate Open Area w/ Debris = N/A N/A ft

Debris Clogging % = 0% 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 = 0.00 N/A ft (distance below basin bottom at Stage = 0 ft) Outlet Orifice Area = 1.65 N/A ft

Outlet Pipe Diameter = 18.00 N/A inches Outlet Orifice Centroid = 0.70 N/A feet

Restrictor Plate Height Above Pipe Invert = 15.90 inches Half-Central Angle of Restrictor Plate on Pipe = 2.44 N/A radians

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

Spillway Invert Stage= 5.50 ft (relative to basin bottom at Stage = 0 ft) Spillway Design Flow Depth= 2.24 feet

Spillway Crest Length = 4.00 feet Stage at Top of Freeboard = 7.74 feet

Spillway End Slopes = 0.00 H:V Basin Area at Top of Freeboard = 0.00 acres

Freeboard above Max Water Surface = 0.00 feet Basin Volume at Top of Freeboard = 1.22 acre-ft

Max Ponding Depth of Target Storage Volume = 4.91 feet Discharge at Top of Freeboard = 61.33 cfs

Routed Hydrograph Results

Design Storm Return Period = WQCV EURV 2 Year 5 Year 10 Year 25 Year 50 Year 100 Year 500 Year

One-Hour Rainfall Depth (in) = N/A N/A 0.69 0.88 1.04 1.25 1.42 1.58 1.74

CUHP Runoff Volume (acre-ft) = 0.366 1.044 0.519 0.707 0.885 1.261 1.522 1.825 2.081

Inflow Hydrograph Volume (acre-ft) = N/A N/A 0.519 0.707 0.885 1.261 1.522 1.825 2.081

CUHP Predevelopment Peak Q (cfs) = N/A N/A 0.2 0.3 1.0 8.8 12.7 17.2 21.0

OPTIONAL Override Predevelopment Peak Q (cfs) = N/A N/A

Predevelopment Unit Peak Flow, q (cfs/acre) = N/A N/A 0.01 0.02 0.05 0.44 0.64 0.86 1.06

Peak Inflow Q (cfs) = N/A N/A 10.8 14.6 17.5 27.2 33.0 40.5 46.2

Peak Outflow Q (cfs) = 0.2 5.6 0.2 0.3 0.9 3.9 9.4 16.3 19.9

Ratio Peak Outflow to Predevelopment Q = N/A N/A N/A 0.9 0.9 0.4 0.7 0.9 0.9

Structure Controlling Flow = Plate Overflow Weir 1 Plate Plate Vertical Orifice 1 Overflow Weir 1 Overflow Weir 1 Outlet Plate 1 Spillway

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

Max Velocity through Grate 2 (fps) = N/A N/A N/A N/A N/A N/A N/A N/A N/A

Time to Drain 97% of Inflow Volume (hours) = 47 62 55 62 64 63 61 59 58

Time to Drain 99% of Inflow Volume (hours) = 51 69 60 67 70 70 69 68 67

Maximum Ponding Depth (ft) = 1.62 4.27 2.03 2.67 3.23 4.00 4.42 4.91 5.80

Area at Maximum Ponding Depth (acres) = 0.30 0.16 0.29 0.28 0.25 0.21 0.15 0.14 0.00

Maximum Volume Stored (acre-ft) = 0.369 1.045 0.489 0.668 0.813 0.995 1.068 1.138 1.222

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 4.06 (July 2022)

Black Hawk PW Underground Detention

HS180

Example Zone Configuration (Retention Pond)

MHFD-Detention_v4-06.xlsm, Outlet Structure 9/25/2023, 10:28 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 2 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 163

Count_OutletPipe2 = 0 0.50(diameter = 13/16 inch) 2 Year 204

COUNTA_2 (Standard FSD Setup)= 1 0.58(diameter = 7/8 inch) EURV 428

Hidden Parameters & Calculations 0.67(diameter = 15/16 inch) 5 Year 268

MaxPondDepth_Error? FALSE 0.76 (diameter = 1 inch) 10 Year 324 Spillway Depth

Cd_Broad-Crested Weir 3.00 0.86(diameter = 1-1/16 inches) 25 Year 401 2.24

WQ Plate Flow at 100yr depth = 0.43 0.97(diameter = 1-1/8 inches) 50 Year 443

CLOG #1= 100% 1.08(diameter = 1-3/16 inches) 100 Year 492 1 Z1_Boolean n*Cdw #1 = #VALUE! 1.20(diameter = 1-1/4 inches) 500 Year 581 1 Z2_Boolean n*Cdo #1 = #VALUE! 1.32(diameter = 1-5/16 inches) Zone3_Pulldown Message 1 Z3_Boolean

Overflow Weir #1 Angle = 0.000 1.45(diameter = 1-3/8 inches) 1 Opening Message

CLOG #2= N/A 1.59(diameter = 1-7/16 inches) Draintime Running n*Cdw #2 = N/A 1.73(diameter = 1-1/2 inches) Outlet Boolean Outlet Rank Total (1 to 4) n*Cdo #2 = N/A 1.88(diameter = 1-9/16 inches) Vertical Orifice 1 1 1 2

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

Underdrain Q at 100yr depth = 0.00 2.20(diameter = 1-11/16 inches) Overflow Weir 1 1 2 0 Max Depth

VertOrifice1 Q at 100yr depth = 2.84 2.36(diameter = 1-3/4 inches) Overflow Weir 2 0 0 0 500yr Depth

VertOrifice2 Q at 100yr depth = 0.00 2.54(diameter = 1-13/16 inches) Outlet Pipe 1 1 2 0 Freeboard

2.72(diameter = 1-7/8 inches) Outlet Pipe 2 0 0 1 Spillway

Count_User_Hydrographs 0 2.90(diameter = 1-15/16 inches) 0 Spillway Length

CountA_3 (EURV & 100yr) = 1 3.09(diameter = 2 inches) FALSE Time Interval

CountA_4 (100yr Only) = 1 3.29(use rectangular openings) Button Visibility Boolean

COUNTA_5 (FSD Weir Only)= 0 0 WQCV Underdrain

COUNTA_6 (EURV Weir Only)= 1 1 WQCV Plate

0 EURV-WQCV Plate

Outlet1_Pulldown_Boolean 0 EURV-WQCV VertOriice

Outlet2_Pulldown_Boolean 0 Outlet 90% Qpeak

Outlet3_Pulldown_Boolean 0 Outlet Undetained

0 Weir Only 90% Qpeak

0 Five Year Ratio Plate

0 Five Year Ratio VertOrifice

EURV_draintime_user

Spillway Options

Offset

Overlapping

S-A-V-D Chart Axis Default X-axis Left Y-Axis Right Y-Axis minimum bound 0.00 0 0 maximum bound 8.00 60,000 70

S-A-V-D Chart Axis Override X-axis Left Y-Axis Right Y-Axis minimum bound maximum bound

MHFD-Detention, Version 4.06 (July 2022)

DETENTION BASIN OUTLET STRUCTURE DESIGN

0.1 1 10

FL

O

W cf s]

TIME [hr]

500YR IN

500YR OUT

100YR IN

100YR OUT

50YR IN

50YR OUT

25YR IN

25YR OUT

10YR IN

10YR OUT

5YR IN

5YR OUT

2YR IN

2YR OUT

EURV IN

EURV OUT

WQCV IN

WQCV OUT

0.1 1 10 100

P O

N D

IN

G

D

EP

TH

ft

DRAIN TIME [hr]

500YR

100YR

50YR

25YR

10YR

5YR

2YR

EURV

WQCV

10,000

20,000

30,000

40,000

50,000

60,000

0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00

O U

TF

LO

W cf s]

A R

EA

ft ^2

V

O

LU

M E

[f t^

PONDING DEPTH [ft]

User Area [ft^2]

Interpolated Area [ft^2]

Summary Area [ft^2]

Volume [ft^3]

Summary Volume [ft^3]

Outflow [cfs]

Summary Outflow [cfs]

Outflow Hydrograph Workbook Filename:

Inflow Hydrographs

The user can override the calculated inflow hydrographs from this workbook with inflow hydrographs developed in a separate program.

SOURCE CUHP CUHP CUHP CUHP CUHP CUHP CUHP CUHP CUHP

Time Interval TIME WQCV [cfs] EURV [cfs] 2 Year [cfs] 5 Year [cfs] 10 Year [cfs] 25 Year [cfs] 50 Year [cfs] 100 Year [cfs] 500 Year [cfs]

5.00 min 0:00:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

0:05:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

0:10:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

0:15:00 0.00 0.00 0.00 1.11 1.85 0.94 1.64 1.50 2.08

0:20:00 0.00 0.00 4.51 6.26 7.62 4.74 5.75 6.21 7.10

0:25:00 0.00 0.00 9.89 13.75 17.42 10.74 12.76 13.74 15.93

0:30:00 0.00 0.00 10.79 14.58 17.52 25.79 32.35 37.19 43.21

0:35:00 0.00 0.00 8.71 11.50 14.06 27.18 33.02 40.49 46.18

0:40:00 0.00 0.00 6.90 8.83 10.70 23.89 28.74 34.50 39.16

0:45:00 0.00 0.00 5.17 6.86 8.49 18.27 21.89 27.80 31.45

0:50:00 0.00 0.00 4.03 5.55 6.60 15.06 18.07 22.37 25.34

0:55:00 0.00 0.00 3.11 4.21 5.16 10.95 13.17 17.43 19.78

1:00:00 0.00 0.00 2.53 3.35 4.26 8.11 9.74 13.79 15.65

1:05:00 0.00 0.00 2.27 2.98 3.91 6.21 7.49 11.41 12.99

1:10:00 0.00 0.00 1.91 2.85 3.80 4.77 5.74 7.88 8.97

1:15:00 0.00 0.00 1.70 2.61 3.76 4.03 4.82 5.92 6.74

1:20:00 0.00 0.00 1.59 2.36 3.34 3.26 3.83 4.16 4.70

1:25:00 0.00 0.00 1.52 2.21 2.82 2.84 3.30 3.20 3.59

1:30:00 0.00 0.00 1.48 2.13 2.50 2.40 2.76 2.59 2.88

1:35:00 0.00 0.00 1.45 2.08 2.31 2.13 2.44 2.23 2.47

1:40:00 0.00 0.00 1.44 1.79 2.19 1.98 2.25 2.05 2.27

1:45:00 0.00 0.00 1.44 1.61 2.11 1.90 2.16 2.00 2.20

1:50:00 0.00 0.00 1.44 1.51 2.07 1.85 2.10 1.98 2.18

1:55:00 0.00 0.00 1.16 1.45 1.98 1.83 2.08 1.98 2.18

2:00:00 0.00 0.00 0.98 1.34 1.75 1.83 2.07 1.98 2.18

2:05:00 0.00 0.00 0.59 0.80 1.05 1.10 1.24 1.18 1.30

2:10:00 0.00 0.00 0.34 0.47 0.62 0.65 0.74 0.70 0.77

2:15:00 0.00 0.00 0.19 0.26 0.34 0.36 0.41 0.39 0.43

2:20:00 0.00 0.00 0.09 0.15 0.18 0.20 0.23 0.22 0.24

2:25:00 0.00 0.00 0.04 0.07 0.08 0.09 0.10 0.10 0.11

2:30:00 0.00 0.00 0.01 0.02 0.02 0.03 0.03 0.03 0.03

2:35:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

2:40:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

2:45:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

2:50:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

2:55:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

3:00:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

3:05:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

3:10:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

3:15:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

3:20:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

3:25:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

3:30:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

3:35:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

3:40:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

3:45:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

3:50:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

3:55:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

4:00:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

4:05:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

4:10:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

4:15:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

4:20:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

4:25:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

4:30:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

4:35:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

4:40:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

4:45:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

4:50:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

4:55:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

5:00:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

5:05:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

5:10:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

5:15:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

5:20:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

5:25:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

5:30:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

5:35:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

5:40:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

5:45:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

5:50:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

5:55:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

6:00:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

DETENTION BASIN OUTLET STRUCTURE DESIGN

Summary Stage-Area-Volume-Discharge Relationships

The user can create a summary S-A-V-D by entering the desired stage increments and the remainder of the table will populate automatically.

The user should graphically compare the summary S-A-V-D table to the full S-A-V-D table in the chart to confirm it captures all key transition points.

Stage Area Area Volume Volume Total

Outflow

[ft] [ft

] [acres] [ft

] [ac-ft] [cfs]

0.00 6,710 0.154 0 0.000 0.00

1.61 12,912 0.296 15,940 0.366 0.17

3.15 11,035 0.253 34,640 0.795 0.74

3.66 10,257 0.235 40,075 0.920 1.91

4.24 7,303 0.168 45,301 1.040 6.75

5.41 6,100 0.140 52,611 1.208 17.25

5.50 6,653 0.153 53,184 1.221 17.42

MHFD-Detention, Version 4.06 (July 2022)

Top

100YR

DETENTION BASIN OUTLET STRUCTURE DESIGN

Stage - Storage

Description

Bottom

WQCV

5YR

10YR

25YR

For best results, include the stages of all grade slope changes (e.g. ISV and Floor) from the S-A-V table on

Sheet 'Basin'.

Also include the inverts of all outlets (e.g. vertical orifice, overflow grate, and spillway, where applicable).

4. DRAINAGE DETAILS & PLANS

04.02-HS180 Details