preliminary STORMWATER CONTROL PLAN and hydrology ...

PRELIMINARY STORMWATER CONTROL PLAN

AND HYDROLOGY CALCULATIONS FOR DEIKEL MADRONA AVE RESIDENCE

CAB CONSULTING ENGINEERS CARL BUTTS

[email protected]

APRIL 6, 2018

September 1, 2017 Page 1 of 7 BASMAA

Stormwater Control Plan

for Small Projects/Single-Family Homes

Deikel Residence 1545 Madrona Ave. Introduction

The California State Water Resources Control Board reissued the Phase II NPDES Permit for Small Municipal Storm Sewer Systems (MS4s) in February 2013. As of June 30, 2015, development projects that create or replace 2,500 square feet* or more of impervious surface (roofs or pavement) must incorporate specified measures to reduce runoff. This requirement is part of municipalities’ comprehensive effort to reduce runoff pollution.

This purpose of this plan is to address St. Helena City Public Works anticipated comments whereby:

• Drainage needs to be routed to prevent inundation of neighboring properties. Grading and/or site improvement plans shall show how 2-year and 10-year storm flows shall be infiltrated on site and/or diverted at the property lines to prevent inundation of neighboring properties, and

• Prepare and implement a Stormwater Control Plan as required by the Bay Area Stormwater Management Agencies Association (BASMAA) Post-Construction Manual, dated July 14, 2014.

The following design strategies have been incorporated into this project:

• Limit disturbance of creeks and natural drainage features

• Minimize compaction of highly permeable soils

• Limit clearing and grading of native vegetation at the site to the minimum area needed to build the project, allow access, and provide fire protection

• Minimize impervious surfaces by concentrating development on the least-sensitive portions of the site, while leaving the remaining land in a natural undisturbed state

*Projects that create or replace 5,000 square feet or more of impervious surface, except for detached single-family homes, require a comprehensive Stormwater Control Plan for Regulated Projects.

Step-by-Step Instructions

The steps are:

1. Fill out the Project Data Form (below) and select one or more runoff reduction measures. 2. Prepare a site plan or sketch. Specify and design the runoff reduction measures you will use to meet

the stated minimum requirements. 3. Complete your submittal, which will include:

• Project Data Form

• Site Plan or Sketch


• Completed checklist for each Runoff Reduction Measure selected Step 1: Project Data Form and Runoff Reduction Measure Selection

Complete all fields.

Project Name/Number Deikel Residence

Application Submittal Date

[to be verified by municipal staff] TBD

Project Location

[Street Address if available, or intersection and/or APN] 1545 Madrona Ave.

Name of Owner or Developer Ted and Pamala Deikel

Project Type and Description

[Examples: “Single Family Residence,” “Parking Lot Addition,” “Retail and Parking”]

Single Family Residence with Garage.

Total Project Site Area (sf) 6,965 (sf)

Total New or Replaced Impervious Surface Area (square feet) [Sum of impervious area that will be constructed as part of the project]

2,200 (sf)

Total Pre-Project Impervious Surface Area 2,654 (sf)

Total Post-Project Impervious Surface Area 2,200 (sf)

Runoff Reduction Measures Selected

(Check one or more)

X - 1. Disperse runoff to vegetated area

2. Pervious pavement

3. Cisterns or Rain Barrels

X - 4. Subsurface Infiltration Units

Step 2: Delineate impervious areas and locations of runoff reduction measures

The pre-project conditions and shed are shown in Exhibit A – Pre Project Conditions.


The post-project conditions and sheds with designated impervious areas are shown in Exhibit B - Deikel Residence Storm Water Control Plan.

The location and options for runoff reduction are annotated on Exhibit B.

Option 4 has been selected as the primary runoff reduction option for this project for the following reasons:

1. Provides an efficient and compact collection system for infiltration into native soils given the very compact space the project is afforded.

2. Rain Cisterns are not desired due to the architectural character of the residence.

Rainwater leaders tied to a small on-site storm drain system will collect impervious surface and roof runoff. This runoff will be directed to several subsurface NDS Flo Well infiltration units for reduction in runoff.

Option 1, modified to field conditions, has also been selected as an additional runoff reduction measure. This option is targeted to landscape and vegetated areas that will eventually drain to the northeastern corner of the property.

The site is mapped by the National Resources Conservation Service as Cortina very gravelly loam which has a Hydrologic Soils classification of “A”. The NRCS data is provided in Appendix C.

A percolation test was is proposed following design review. A percolation rate of 15” per hour is assumed based on previous soils infiltration testing on nearby sites for this soils complex.

The hydrologic methodology used to substantiate the city’s requirements is TR-20 using Soils Conservation Service (SCS) rainfall data for the 2 and 10-year storm events. SCS rainfall data is provided by the National Oceanic and Atmospheric Administration (NOAA) Precipitation Data Frequency Server for the project site. Values of 3.88 in/day and 5.66 in/day for the 2 and 10-year events are used in calculating runoff rates in TR-20. NOAA precipitation data is provided in Appendix C.

Pre and Post Developed curve numbers (CN) are calculated as 56 and 63, respectively, for the 0.16-acre site. A time of concentration of 10-minutes is assumed for the pre and post developed condition. The storm distribution for St. Helena is Type 1A taken from Figure B-2 of the NRCS “Urban Hydrology for Small Watersheds – Technical Release 55.” Composite CN values are provided on each hydrograph report in Appendix C.

Autodesk Autocad Civil 3D Hydraflow Hydragraphs Extension is used in calculating TR-20 runoff data for the pre and post-developed condition. The pre-developed condition shows a runoff rate for the 2 and 10-year storm as 0.006 and 0.035 cfs.

The post-developed condition shows a runoff rate for the 2 and 10-year storm as 0.000 and 0.013 cfs. The 2-year runoff is completely captured on-site. The 10-year post developed condition lessens the rate of runoff by roughly 8%. The proposed NDS Flo Well dry cisterns therefore meet runoff requirements for the 2-year storm. An infiltration sump and pump system


using a 15 gallon per minute submersible pump and discharge to the street is proposed for excess flow (0.013 cfs, or 6.24 gallons per minute) of the 10-year event. Pre and post-developed calculations are provided in Appendix C.


Appendix A – Pre Developed Conditions

CAB

CON

SULT

ING

ENGI

NEE

RS

851

NAP

A VA

LLEY

CORP

ORA

TE W

AYSU

ITE

DN

APA,

CA

9455

8V

707.

252.

2011

C 70

7.69

4.64

7920

18.0

4.06

DEIK

EL M

ARDO

NA

RESI

DEN

CEEX

ISTI

NG

SHED

CO

NDI

TIO

NS

1" =

20'

ST. H

ELEN

ACA

LIFO

RNIA

2018

.04

2017

.09.

01 E

X SH

ED

AutoCAD SHX Text

IMPERVIOUS AREAS HATCHED SINGLE DRAINAGE AREA

AutoCAD SHX Text

TOTAL IMPERVIOUS = 2654 SF (0.06 AC) = 2654 SF (0.06 AC) TOTAL PERVIOUS = 4311 SF (0.10 AC)= 4311 SF (0.10 AC)

AutoCAD SHX Text

FLOW, TYP

AutoCAD SHX Text

(E) POINT OF CONCENTRATION


Appendix B – Post Developed Storm Water Control

Plan

CAB

CON

SULT

ING

ENGI

NEE

RS

851

NAP

A VA

LLEY

CORP

ORA

TE W

AYSU

ITE

DN

APA,

CA

9455

8V

707.

252.

2011

C 70

7.69

4.64

7920

18.0

4.06

DEIK

EL M

ADRO

NA

RESI

DEN

CEST

ORM

WAT

ER C

ON

TRO

L PL

AN

1" =

20'

ST. H

ELEN

ACA

LIFO

RNIA

2018

.04

2018

.04.

06 S

CP

AutoCAD SHX Text

4 X NDS FLOW WELL

AutoCAD SHX Text

IMPERVIOUS AREAS HATCHED SINGLE DRAINAGE AREA

AutoCAD SHX Text

TOTAL IMPERVIOUS = 2200 SF (0.05 AC) = 2200 SF (0.05 AC) TOTAL PERVIOUS = 4765 SF (0.11 AC)= 4765 SF (0.11 AC)

AutoCAD SHX Text

FLOW, TYP

AutoCAD SHX Text

INFILTRATION SUMP


Appendix C – Hydrology Supporting Data and

Calculations

Soil Map—Napa County, California

Natural ResourcesConservation Service

Web Soil SurveyNational Cooperative Soil Survey

4/6/2018Page 1 of 3

4261

740

4261

770

4261

800

4261

830

4261

860

4261

890

4261

920

4261

740

4261

770

4261

800

4261

830

4261

860

4261

890

4261

920

545620 545650 545680 545710 545740 545770 545800 545830 545860 545890 545920

545650 545680 545710 545740 545770 545800 545830 545860 545890 545920

38° 30' 16'' N12

2° 2

8' 3

6'' W

38° 30' 16'' N

122°

28'

23'

' W

38° 30' 9'' N

122°

28'

36'

' W

38° 30' 9'' N

122°

28'

23'

' W

N

Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 10N WGS840 50 100 200 300

Feet0 20 40 80 120

MetersMap Scale: 1:1,410 if printed on A landscape (11" x 8.5") sheet.

Soil Map may not be valid at this scale.

Carl Butts

Callout

Site

MAP LEGEND MAP INFORMATION

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

SoilsSoil Map Unit Polygons

Soil Map Unit Lines

Soil Map Unit Points

Special Point FeaturesBlowout

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 FeaturesStreams and Canals

TransportationRails

Interstate Highways

US Routes

Major Roads

Local Roads

BackgroundAerial 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 ServiceWeb 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: Napa County, CaliforniaSurvey Area Data: Version 10, Sep 25, 2017

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

Date(s) aerial images were photographed: Dec 31, 2009—Nov 22, 2016

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.




4/6/2018Page 2 of 3

Map Unit Legend

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

124 Cortina very gravelly loam, 0 to 5 percent slopes, moist, MLRA 14

9.1 100.0%

Totals for Area of Interest 9.1 100.0%




4/6/2018Page 3 of 3

9/9/2016 Precipitation Frequency Data Server

http://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=38.5023&lon=122.4667&data=depth&units=english&series=pds 1/4

NOAA Atlas 14, Volume 6, Version 2 Location name: Saint Helena, California, US* Latitude: 38.5023°, Longitude: 122.4667°

Elevation: 237 ft** source: Google Maps

POINT PRECIPITATION FREQUENCY ESTIMATES

Sanja Perica, Sarah Dietz, Sarah Heim, Lillian Hiner, Kazungu Maitaria, Deborah Martin, SandraPavlovic, Ishani Roy, Carl Trypaluk, Dale Unruh, Fenglin Yan, Michael Yekta, Tan Zhao, Geoffrey

Bonnin, Daniel Brewer, LiChuan Chen, Tye Parzybok, John Yarchoan

NOAA, National Weather Service, Silver Spring, Maryland

PF_tabular | PF_graphical | Maps_&_aerials

PF tabularPDSbased point precipitation frequency estimates with 90% confidence intervals (in inches)1

DurationAverage recurrence interval (years)

1 2 5 10 25 50 100 200 500 1000

5min 0.133(0.119‑0.151)

0.163(0.145‑0.186)

0.203(0.180‑0.231)

0.235(0.206‑0.271)

0.280(0.236‑0.335)

0.314(0.259‑0.385)

0.350(0.280‑0.441)

0.386(0.300‑0.503)

0.436(0.323‑0.595)

0.476(0.339‑0.675)

10min 0.191(0.170‑0.217)

0.234(0.208‑0.266)

0.291(0.257‑0.331)

0.337(0.296‑0.388)

0.401(0.338‑0.480)

0.450(0.371‑0.552)

0.501(0.401‑0.632)

0.554(0.430‑0.720)

0.626(0.463‑0.853)

0.682(0.486‑0.967)

15min 0.231(0.206‑0.263)

0.283(0.251‑0.322)

0.351(0.311‑0.401)

0.408(0.358‑0.469)

0.485(0.409‑0.580)

0.545(0.449‑0.667)

0.606(0.486‑0.764)

0.670(0.520‑0.871)

0.757(0.560‑1.03)

0.825(0.587‑1.17)

30min 0.349(0.311‑0.396)

0.427(0.380‑0.486)

0.531(0.470‑0.605)

0.616(0.540‑0.709)

0.732(0.618‑0.876)

0.822(0.678‑1.01)

0.915(0.733‑1.15)

1.01(0.785‑1.32)

1.14(0.846‑1.56)

1.25(0.887‑1.77)

60min 0.517(0.460‑0.587)

0.633(0.562‑0.720)

0.786(0.696‑0.896)

0.912(0.800‑1.05)

1.08(0.915‑1.30)

1.22(1.00‑1.49)

1.35(1.09‑1.71)

1.50(1.16‑1.95)

1.69(1.25‑2.31)

1.84(1.31‑2.62)

2hr 0.793(0.705‑0.900)

0.962(0.855‑1.09)

1.18(1.04‑1.35)

1.35(1.19‑1.56)

1.58(1.34‑1.90)

1.76(1.45‑2.16)

1.93(1.55‑2.44)

2.11(1.64‑2.74)

2.34(1.73‑3.19)

2.52(1.79‑3.57)

3hr 1.02(0.908‑1.16)

1.23(1.10‑1.40)

1.51(1.33‑1.72)

1.72(1.51‑1.98)

2.00(1.69‑2.40)

2.21(1.83‑2.71)

2.42(1.94‑3.06)

2.63(2.04‑3.43)

2.91(2.15‑3.96)

3.11(2.22‑4.41)

6hr 1.55(1.38‑1.76)

1.87(1.66‑2.13)

2.28(2.02‑2.60)

2.60(2.28‑2.99)

3.02(2.55‑3.61)

3.32(2.74‑4.07)

3.62(2.90‑4.57)

3.92(3.04‑5.10)

4.31(3.19‑5.87)

4.59(3.27‑6.51)

12hr 2.21(1.97‑2.51)

2.71(2.41‑3.08)

3.34(2.96‑3.81)

3.84(3.37‑4.42)

4.49(3.79‑5.37)

4.97(4.10‑6.09)

5.45(4.36‑6.86)

5.92(4.59‑7.70)

6.54(4.84‑8.91)

7.00(4.98‑9.92)

24hr 3.11(2.79‑3.53)

3.88(3.48‑4.41)

4.87(4.36‑5.54)

5.66(5.04‑6.48)

6.70(5.80‑7.89)

7.47(6.36‑8.96)

8.25(6.88‑10.1)

9.03(7.36‑11.3)

10.1(7.92‑13.0)

10.8(8.29‑14.5)

2day 4.08(3.66‑4.63)

5.22(4.69‑5.93)

6.67(5.98‑7.60)

7.82(6.96‑8.97)

9.33(8.08‑11.0)

10.4(8.90‑12.5)

11.6(9.64‑14.1)

12.7(10.3‑15.9)

14.1(11.1‑18.3)

15.2(11.6‑20.3)

3day 4.69(4.21‑5.32)

6.08(5.46‑6.91)

7.84(7.03‑8.93)

9.23(8.22‑10.6)

11.0(9.57‑13.0)

12.4(10.5‑14.8)

13.7(11.4‑16.8)

15.0(12.2‑18.8)

16.7(13.2‑21.7)

18.0(13.8‑24.1)

4day 5.19(4.67‑5.89)

6.76(6.07‑7.68)

8.73(7.83‑9.95)

10.3(9.16‑11.8)

12.3(10.7‑14.5)

13.8(11.8‑16.6)

15.3(12.8‑18.7)

16.8(13.7‑21.0)

18.7(14.8‑24.3)

20.2(15.4‑26.9)

7day 6.49(5.84‑7.37)

8.34(7.49‑9.48)

10.7(9.59‑12.2)

12.6(11.2‑14.4)

15.0(13.0‑17.7)

16.9(14.4‑20.3)

18.7(15.6‑22.9)

20.6(16.8‑25.8)

23.0(18.1‑29.9)

24.9(19.0‑33.2)

10day 7.42(6.67‑8.43)

9.46(8.50‑10.7)

12.1(10.8‑13.7)

14.1(12.6‑16.2)

16.9(14.6‑19.9)

19.0(16.2‑22.7)

21.0(17.5‑25.7)

23.1(18.8‑28.9)

25.9(20.4‑33.5)

28.0(21.4‑37.3)

20day 9.84(8.84‑11.2)

12.5(11.2‑14.2)

15.9(14.2‑18.1)

18.6(16.5‑21.3)

22.1(19.1‑26.0)

24.7(21.0‑29.6)

27.2(22.7‑33.3)

29.8(24.3‑37.3)

33.2(26.1‑43.0)

35.7(27.3‑47.6)

30day 11.7(10.5‑13.2)

14.8(13.3‑16.9)

18.8(16.8‑21.4)

21.9(19.5‑25.1)

25.9(22.4‑30.5)

28.8(24.5‑34.6)

31.7(26.4‑38.8)

34.5(28.1‑43.2)

38.2(30.1‑49.5)

40.9(31.3‑54.6)

45day 14.2(12.7‑16.1)

18.0(16.2‑20.4)

22.7(20.3‑25.8)

26.3(23.4‑30.2)

30.9(26.8‑36.4)

34.2(29.1‑41.0)

37.4(31.2‑45.8)

40.5(33.0‑50.7)

44.5(35.0‑57.6)

47.4(36.2‑63.2)

60day 16.7(15.0‑19.0)

21.2(19.1‑24.1)

26.6(23.9‑30.3)

30.7(27.4‑35.2)

35.9(31.1‑42.3)

39.6(33.7‑47.4)

43.0(35.9‑52.6)

46.4(37.8‑58.1)

50.6(39.8‑65.5)

53.6(41.0‑71.5)

1 Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS).Numbers in parenthesis are PF estimates at lower and upper bounds of the 90% confidence interval. The probability that precipitation frequency estimates (for agiven duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5%. Estimates at upper bounds are notchecked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values.Please refer to NOAA Atlas 14 document for more information.

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Hydraflow Table of ContentsC:\Users\Carl Butts\Dropbox\CAB Consulting\2018\2018.04 Deikel Madrona\Reports & Calcs\SCP\Appendix C - Hydrology\Deikel Madrona.gpw

Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2016 by Autodesk, Inc. v11 Friday, 04 / 6 / 2018

Watershed Model Schematic...................................................................................... 1

Hydrograph Return Period Recap............................................................................. 2

2 - YearSummary Report......................................................................................................................... 3Hydrograph Reports................................................................................................................... 4

Hydrograph No. 1, SCS Runoff, Pre-Developed...................................................................... 4Hydrograph No. 2, SCS Runoff, Post Developed..................................................................... 5Hydrograph No. 3, Reservoir, Routed Post Developed............................................................ 6

Pond Report - Flo Well........................................................................................................ 7

10 - YearSummary Report......................................................................................................................... 9Hydrograph Reports................................................................................................................. 10

Hydrograph No. 1, SCS Runoff, Pre-Developed.................................................................... 10Hydrograph No. 2, SCS Runoff, Post Developed................................................................... 11Hydrograph No. 3, Reservoir, Routed Post Developed.......................................................... 12

IDF Report.................................................................................................................. 13

1

2

3

1

Watershed Model SchematicHydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2016 by Autodesk, Inc. v11

Project: C:\Users\Carl Butts\Dropbox\CAB Consulting\2018\2018.04 Deikel Madrona\Reports & Calcs\SCP\Appendix C - Hydrology\DFriday, 04 / 6 / 2018

Hyd. Origin Description

Legend

1 SCS Runoff Pre-Developed

2 SCS Runoff Post Developed

3 Reservoir Routed Post Developed

Hydrograph Return Period Recap2

Hyd. Hydrograph Inflow Peak Outflow (cfs) Hydrograph

No. type hyd(s) Description

(origin) 1-yr 2-yr 3-yr 5-yr 10-yr 25-yr 50-yr 100-yr

1 SCS Runoff ------ ------- 0.012 ------- ------- 0.053 ------- ------- ------- Pre-Developed

2 SCS Runoff ------ ------- 0.008 ------- ------- 0.045 ------- ------- ------- Post Developed

3 Reservoir 2 ------- 0.000 ------- ------- 0.013 ------- ------- ------- Routed Post Developed

Proj. file: C:\Users\Carl Butts\Dropbox\CAB Consulting\2018\2018.04 Deikel Madrona\Reports & Calcs\SCP\Appendix C - Hydrology\Friday, 04 / 6 / 2018

Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2016 by Autodesk, Inc. v11

Hydrograph Summary Report3

Hyd. Hydrograph Peak Time Time to Hyd. Inflow Maximum Total Hydrograph

No. type flow interval Peak volume hyd(s) elevation strge used Description

(origin) (cfs) (min) (min) (cuft) (ft) (cuft)

1 SCS Runoff 0.012 1 484 437 ------ ------ ------ Pre-Developed

2 SCS Runoff 0.008 1 485 382 ------ ------ ------ Post Developed

3 Reservoir 0.000 1 n/a 0 2 251.54 0.419 Routed Post Developed

C:\Users\Carl Butts\Dropbox\CAB Consulting\2018\2018.04 Deikel Madrona\Reports & Calcs\SCP\Appendix C - Hydrology\Deikel MaReturn Period: 2 Year Friday, 04 / 6 / 2018


Hydrograph ReportHydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2016 by Autodesk, Inc. v11 Friday, 04 / 6 / 2018

Hyd. No. 1

Pre-Developed

Hydrograph type = SCS Runoff Peak discharge = 0.012 cfsStorm frequency = 2 yrs Time to peak = 8.07 hrsTime interval = 1 min Hyd. volume = 437 cuftDrainage area = 0.160 ac Curve number = 61*Basin Slope = 0.0 % Hydraulic length = 0 ftTc method = User Time of conc. (Tc) = 10.00 minTotal precip. = 3.88 in Distribution = Type IAStorm duration = 24 hrs Shape factor = 484

* Composite (Area/CN) = [(0.060 x 98) + (0.100 x 39)] / 0.160

4

0 2 4 6 8 10 12 14 16 18 20 22 24 26

Q (cfs)

0.00 0.00

0.01 0.01

0.02 0.02

0.03 0.03

0.04 0.04

0.05 0.05

0.06 0.06

0.07 0.07

0.08 0.08

0.09 0.09

0.10 0.10

Q (cfs)

Time (hrs)

Pre-DevelopedHyd. No. 1 -- 2 Year

Hyd No. 1


Hyd. No. 2

Post Developed



5

0 2 4 6 8 10 12 14 16 18 20 22 24 26

Q (cfs)

0.00 0.00

0.01 0.01

0.02 0.02

0.03 0.03

0.04 0.04

0.05 0.05

0.06 0.06

0.07 0.07

0.08 0.08

0.09 0.09

0.10 0.10

Q (cfs)

Time (hrs)

Post DevelopedHyd. No. 2 -- 2 Year

Hyd No. 2


Hyd. No. 3

Routed Post Developed

Hydrograph type = Reservoir Peak discharge = 0.000 cfsStorm frequency = 2 yrs Time to peak = n/aTime interval = 1 min Hyd. volume = 0 cuftInflow hyd. No. = 2 - Post Developed Max. Elevation = 251.54 ftReservoir name = Flo Well Max. Storage = 0 cuft

Storage Indication method used. Exfiltration extracted from Outflow.

6

0 2 4 6 8 10 12 14 16 18 20 22 24 26

Q (cfs)

0.00 0.00

0.01 0.01

0.02 0.02

0.03 0.03

0.04 0.04

0.05 0.05

0.06 0.06

0.07 0.07

0.08 0.08

0.09 0.09

0.10 0.10

Q (cfs)

Time (hrs)

Routed Post DevelopedHyd. No. 3 -- 2 Year

Hyd No. 3 Hyd No. 2 Total storage used = 0 cuft

Pond Report 7


Pond No. 1 - Flo Well

Pond DataUG Chambers -Invert elev. = 252.00 ft, Rise x Span = 2.33 x 1.58 ft, Barrel Len = 1.58 ft, No. Barrels = 5, Slope = 0.00%, Headers = NoEncasement -Invert elev. = 251.50 ft, Width = 2.58 ft, Height = 2.83 ft, Voids = 50.00%

Stage / Storage TableStage (ft) Elevation (ft) Contour area (sqft) Incr. Storage (cuft) Total storage (cuft)

0.00 251.50 n/a 0 00.28 251.78 n/a 3 30.57 252.07 n/a 3 60.85 252.35 n/a 5 111.13 252.63 n/a 5 151.42 252.92 n/a 5 201.70 253.20 n/a 5 251.98 253.48 n/a 5 292.26 253.76 n/a 5 342.55 254.05 n/a 5 392.83 254.33 n/a 5 43

Culvert / Orifice Structures Weir Structures

[A] [B] [C] [PrfRsr] [A] [B] [C] [D]

Rise (in) = 2.00 0.00 0.00 0.00

Span (in) = 2.00 0.00 0.00 0.00

No. Barrels = 1 0 0 0

Invert El. (ft) = 254.00 0.00 0.00 0.00

Length (ft) = 10.00 0.00 0.00 0.00

Slope (%) = 0.50 0.00 0.00 n/a

N-Value = .013 .013 .013 n/a

Orifice Coeff. = 0.60 0.60 0.60 0.60

Multi-Stage = n/a No No No

Crest Len (ft) = 0.00 0.00 0.00 0.00

Crest El. (ft) = 0.00 0.00 0.00 0.00

Weir Coeff. = 3.33 3.33 3.33 3.33

Weir Type = --- --- --- ---

Multi-Stage = No No No No

Exfil.(in/hr) = 15.000 (by Wet area)

TW Elev. (ft) = 0.00

Note: Culvert/Orifice outflows are analyzed under inlet (ic) and outlet (oc) control. Weir risers checked for orifice conditions (ic) and submergence (s).

Stage / Storage / Discharge TableStage Storage Elevation Clv A Clv B Clv C PrfRsr Wr A Wr B Wr C Wr D Exfil User Totalft cuft ft cfs cfs cfs cfs cfs cfs cfs cfs cfs cfs cfs

0.00 0 251.50 0.00 --- --- --- --- --- --- --- 0.000 --- 0.0000.03 0 251.53 0.00 --- --- --- --- --- --- --- 0.007 --- 0.0070.06 1 251.56 0.00 --- --- --- --- --- --- --- 0.007 --- 0.0070.08 1 251.58 0.00 --- --- --- --- --- --- --- 0.008 --- 0.0080.11 1 251.61 0.00 --- --- --- --- --- --- --- 0.008 --- 0.0080.14 1 251.64 0.00 --- --- --- --- --- --- --- 0.008 --- 0.0080.17 2 251.67 0.00 --- --- --- --- --- --- --- 0.008 --- 0.0080.20 2 251.70 0.00 --- --- --- --- --- --- --- 0.008 --- 0.0080.23 2 251.73 0.00 --- --- --- --- --- --- --- 0.008 --- 0.0080.25 3 251.75 0.00 --- --- --- --- --- --- --- 0.008 --- 0.0080.28 3 251.78 0.00 --- --- --- --- --- --- --- 0.009 --- 0.0090.31 3 251.81 0.00 --- --- --- --- --- --- --- 0.009 --- 0.0090.34 4 251.84 0.00 --- --- --- --- --- --- --- 0.009 --- 0.0090.37 4 251.87 0.00 --- --- --- --- --- --- --- 0.009 --- 0.0090.40 4 251.90 0.00 --- --- --- --- --- --- --- 0.009 --- 0.0090.42 5 251.92 0.00 --- --- --- --- --- --- --- 0.009 --- 0.0090.45 5 251.95 0.00 --- --- --- --- --- --- --- 0.010 --- 0.0100.48 5 251.98 0.00 --- --- --- --- --- --- --- 0.010 --- 0.0100.51 6 252.01 0.00 --- --- --- --- --- --- --- 0.010 --- 0.0100.54 6 252.04 0.00 --- --- --- --- --- --- --- 0.010 --- 0.0100.57 6 252.07 0.00 --- --- --- --- --- --- --- 0.010 --- 0.0100.59 7 252.09 0.00 --- --- --- --- --- --- --- 0.010 --- 0.0100.62 7 252.12 0.00 --- --- --- --- --- --- --- 0.010 --- 0.0100.65 8 252.15 0.00 --- --- --- --- --- --- --- 0.011 --- 0.0110.68 8 252.18 0.00 --- --- --- --- --- --- --- 0.011 --- 0.0110.71 9 252.21 0.00 --- --- --- --- --- --- --- 0.011 --- 0.0110.74 9 252.24 0.00 --- --- --- --- --- --- --- 0.011 --- 0.0110.76 9 252.26 0.00 --- --- --- --- --- --- --- 0.011 --- 0.0110.79 10 252.29 0.00 --- --- --- --- --- --- --- 0.011 --- 0.0110.82 10 252.32 0.00 --- --- --- --- --- --- --- 0.012 --- 0.0120.85 11 252.35 0.00 --- --- --- --- --- --- --- 0.012 --- 0.0120.88 11 252.38 0.00 --- --- --- --- --- --- --- 0.012 --- 0.012

Continues on next page...

8

Flo Well

Stage / Storage / Discharge TableStage Storage Elevation Clv A Clv B Clv C PrfRsr Wr A Wr B Wr C Wr D Exfil User Totalft cuft ft cfs cfs cfs cfs cfs cfs cfs cfs cfs cfs cfs

0.91 12 252.41 0.00 --- --- --- --- --- --- --- 0.012 --- 0.0120.93 12 252.43 0.00 --- --- --- --- --- --- --- 0.012 --- 0.0120.96 13 252.46 0.00 --- --- --- --- --- --- --- 0.012 --- 0.0120.99 13 252.49 0.00 --- --- --- --- --- --- --- 0.013 --- 0.0131.02 14 252.52 0.00 --- --- --- --- --- --- --- 0.013 --- 0.0131.05 14 252.55 0.00 --- --- --- --- --- --- --- 0.013 --- 0.0131.08 15 252.58 0.00 --- --- --- --- --- --- --- 0.013 --- 0.0131.10 15 252.60 0.00 --- --- --- --- --- --- --- 0.013 --- 0.0131.13 15 252.63 0.00 --- --- --- --- --- --- --- 0.013 --- 0.0131.16 16 252.66 0.00 --- --- --- --- --- --- --- 0.013 --- 0.0131.19 16 252.69 0.00 --- --- --- --- --- --- --- 0.014 --- 0.0141.22 17 252.72 0.00 --- --- --- --- --- --- --- 0.014 --- 0.0141.25 17 252.75 0.00 --- --- --- --- --- --- --- 0.014 --- 0.0141.27 18 252.77 0.00 --- --- --- --- --- --- --- 0.014 --- 0.0141.30 18 252.80 0.00 --- --- --- --- --- --- --- 0.014 --- 0.0141.33 19 252.83 0.00 --- --- --- --- --- --- --- 0.014 --- 0.0141.36 19 252.86 0.00 --- --- --- --- --- --- --- 0.015 --- 0.0151.39 20 252.89 0.00 --- --- --- --- --- --- --- 0.015 --- 0.0151.42 20 252.92 0.00 --- --- --- --- --- --- --- 0.015 --- 0.0151.44 21 252.94 0.00 --- --- --- --- --- --- --- 0.015 --- 0.0151.47 21 252.97 0.00 --- --- --- --- --- --- --- 0.015 --- 0.0151.50 22 253.00 0.00 --- --- --- --- --- --- --- 0.015 --- 0.0151.53 22 253.03 0.00 --- --- --- --- --- --- --- 0.015 --- 0.0151.56 22 253.06 0.00 --- --- --- --- --- --- --- 0.016 --- 0.0161.58 23 253.08 0.00 --- --- --- --- --- --- --- 0.016 --- 0.0161.61 23 253.11 0.00 --- --- --- --- --- --- --- 0.016 --- 0.0161.64 24 253.14 0.00 --- --- --- --- --- --- --- 0.016 --- 0.0161.67 24 253.17 0.00 --- --- --- --- --- --- --- 0.016 --- 0.0161.70 25 253.20 0.00 --- --- --- --- --- --- --- 0.016 --- 0.0161.73 25 253.23 0.00 --- --- --- --- --- --- --- 0.017 --- 0.0171.75 26 253.25 0.00 --- --- --- --- --- --- --- 0.017 --- 0.0171.78 26 253.28 0.00 --- --- --- --- --- --- --- 0.017 --- 0.0171.81 27 253.31 0.00 --- --- --- --- --- --- --- 0.017 --- 0.0171.84 27 253.34 0.00 --- --- --- --- --- --- --- 0.017 --- 0.0171.87 28 253.37 0.00 --- --- --- --- --- --- --- 0.017 --- 0.0171.90 28 253.40 0.00 --- --- --- --- --- --- --- 0.017 --- 0.0171.92 29 253.42 0.00 --- --- --- --- --- --- --- 0.018 --- 0.0181.95 29 253.45 0.00 --- --- --- --- --- --- --- 0.018 --- 0.0181.98 29 253.48 0.00 --- --- --- --- --- --- --- 0.018 --- 0.0182.01 30 253.51 0.00 --- --- --- --- --- --- --- 0.018 --- 0.0182.04 30 253.54 0.00 --- --- --- --- --- --- --- 0.018 --- 0.0182.07 31 253.57 0.00 --- --- --- --- --- --- --- 0.018 --- 0.0182.09 31 253.59 0.00 --- --- --- --- --- --- --- 0.019 --- 0.0192.12 32 253.62 0.00 --- --- --- --- --- --- --- 0.019 --- 0.0192.15 32 253.65 0.00 --- --- --- --- --- --- --- 0.019 --- 0.0192.18 33 253.68 0.00 --- --- --- --- --- --- --- 0.019 --- 0.0192.21 33 253.71 0.00 --- --- --- --- --- --- --- 0.019 --- 0.0192.24 34 253.74 0.00 --- --- --- --- --- --- --- 0.019 --- 0.0192.26 34 253.76 0.00 --- --- --- --- --- --- --- 0.019 --- 0.0192.29 35 253.79 0.00 --- --- --- --- --- --- --- 0.020 --- 0.0202.32 35 253.82 0.00 --- --- --- --- --- --- --- 0.020 --- 0.0202.35 35 253.85 0.00 --- --- --- --- --- --- --- 0.020 --- 0.0202.38 36 253.88 0.00 --- --- --- --- --- --- --- 0.020 --- 0.0202.41 36 253.91 0.00 --- --- --- --- --- --- --- 0.020 --- 0.0202.43 37 253.93 0.00 --- --- --- --- --- --- --- 0.020 --- 0.0202.46 37 253.96 0.00 --- --- --- --- --- --- --- 0.021 --- 0.0212.49 38 253.99 0.00 --- --- --- --- --- --- --- 0.021 --- 0.0212.52 38 254.02 0.00 oc --- --- --- --- --- --- --- 0.021 --- 0.0212.55 39 254.05 0.00 oc --- --- --- --- --- --- --- 0.021 --- 0.0242.58 39 254.08 0.01 oc --- --- --- --- --- --- --- 0.021 --- 0.0292.60 40 254.10 0.01 oc --- --- --- --- --- --- --- 0.021 --- 0.0342.63 40 254.13 0.02 oc --- --- --- --- --- --- --- 0.022 --- 0.0382.66 41 254.16 0.02 oc --- --- --- --- --- --- --- 0.022 --- 0.0402.69 41 254.19 0.02 oc --- --- --- --- --- --- --- 0.022 --- 0.0432.72 42 254.22 0.03 oc --- --- --- --- --- --- --- 0.022 --- 0.0472.75 42 254.25 0.03 oc --- --- --- --- --- --- --- 0.022 --- 0.0512.77 42 254.27 0.03 oc --- --- --- --- --- --- --- 0.022 --- 0.0542.80 43 254.30 0.03 oc --- --- --- --- --- --- --- 0.022 --- 0.0572.83 43 254.33 0.04 oc --- --- --- --- --- --- --- 0.023 --- 0.059

...End

Hydrograph Summary Report9

Hyd. Hydrograph Peak Time Time to Hyd. Inflow Maximum Total Hydrograph

No. type flow interval Peak volume hyd(s) elevation strge used Description

(origin) (cfs) (min) (min) (cuft) (ft) (cuft)

1 SCS Runoff 0.053 1 481 1,035 ------ ------ ------ Pre-Developed

2 SCS Runoff 0.045 1 481 944 ------ ------ ------ Post Developed

3 Reservoir 0.013 1 490 16 2 254.11 39.7 Routed Post Developed

C:\Users\Carl Butts\Dropbox\CAB Consulting\2018\2018.04 Deikel Madrona\Reports & Calcs\SCP\Appendix C - Hydrology\Deikel MaReturn Period: 10 Year Friday, 04 / 6 / 2018



Hyd. No. 1

Pre-Developed

Hydrograph type = SCS Runoff Peak discharge = 0.053 cfsStorm frequency = 10 yrs Time to peak = 8.02 hrsTime interval = 1 min Hyd. volume = 1,035 cuftDrainage area = 0.160 ac Curve number = 61*Basin Slope = 0.0 % Hydraulic length = 0 ftTc method = User Time of conc. (Tc) = 10.00 minTotal precip. = 5.66 in Distribution = Type IAStorm duration = 24 hrs Shape factor = 484


10

0 2 4 6 8 10 12 14 16 18 20 22 24 26

Q (cfs)

0.00 0.00

0.01 0.01

0.02 0.02

0.03 0.03

0.04 0.04

0.05 0.05

0.06 0.06

0.07 0.07

0.08 0.08

0.09 0.09

0.10 0.10

Q (cfs)

Time (hrs)

Pre-DevelopedHyd. No. 1 -- 10 Year

Hyd No. 1


Hyd. No. 2

Post Developed



11

0 2 4 6 8 10 12 14 16 18 20 22 24 26

Q (cfs)

0.00 0.00

0.01 0.01

0.02 0.02

0.03 0.03

0.04 0.04

0.05 0.05

0.06 0.06

0.07 0.07

0.08 0.08

0.09 0.09

0.10 0.10

Q (cfs)

Time (hrs)

Post DevelopedHyd. No. 2 -- 10 Year

Hyd No. 2


Hyd. No. 3

Routed Post Developed

Hydrograph type = Reservoir Peak discharge = 0.013 cfsStorm frequency = 10 yrs Time to peak = 8.17 hrsTime interval = 1 min Hyd. volume = 16 cuftInflow hyd. No. = 2 - Post Developed Max. Elevation = 254.11 ftReservoir name = Flo Well Max. Storage = 40 cuft

Storage Indication method used. Exfiltration extracted from Outflow.

12

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0

Q (cfs)

0.00 0.00

0.01 0.01

0.02 0.02

0.03 0.03

0.04 0.04

0.05 0.05

0.06 0.06

0.07 0.07

0.08 0.08

0.09 0.09

0.10 0.10

Q (cfs)

Time (hrs)

Routed Post DevelopedHyd. No. 3 -- 10 Year

Hyd No. 3 Hyd No. 2 Total storage used = 40 cuft

Hydraflow Rainfall Report13


Return Intensity-Duration-Frequency Equation Coefficients (FHA)Period

(Yrs) B D E (N/A)

1 0.0000 0.0000 0.0000 --------

2 0.0000 0.0000 0.0000 --------

3 0.0000 0.0000 0.0000 --------

5 0.0000 0.0000 0.0000 --------

10 13.4094 0.1000 0.5679 --------

25 0.0000 0.0000 0.0000 --------

50 0.0000 0.0000 0.0000 --------

100 0.0000 0.0000 0.0000 --------

File name: RHR.IDF

Intensity = B / (Tc + D)^E

Return Intensity Values (in/hr)Period

(Yrs) 5 min 10 15 20 25 30 35 40 45 50 55 60

1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

5 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10 5.32 3.61 2.87 2.44 2.15 1.94 1.78 1.65 1.54 1.45 1.38 1.31

25 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

50 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

100 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Tc = time in minutes. Values may exceed 60.

Rainfall Precipitation Table (in)

Butts\Dropbox\CAB Consulting\2016\2016.05 Deikel Allyn\Reports & Calcs\SCP\Appendix C - Hydrology\St Helena.pcp

StormDistribution 1-yr 2-yr 3-yr 5-yr 10-yr 25-yr 50-yr 100-yr

SCS 24-hour 0.00 3.88 0.00 0.00 5.66 0.00 0.00 0.00

SCS 6-Hr 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Huff-1st 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Huff-2nd 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Huff-3rd 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Huff-4th 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Huff-Indy 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Custom 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

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