HomeMy WebLinkAbout02 Trout Meadows Ph3 Water Sewer Storm Design Report
JOB NO. B14-008
MONTANA | WASHINGTON | IDAHO | NORTH DAKOTA | PENNSYLVANIA
FEBRUARY 2022
406.586.0277
tdhengineering.com
234 East Babcock Street
Suite 3
Bozeman, MT 59715
CLIENT ENGINEER
Scott Hacker
Montana Crestview
4200 Expressway
Missoula, MT 59808
TD&H Engineering
234 East Babcock Street, Suite 3
Bozeman, MT 59715
Engineer: Cody Croskey, PE
TROUT MEADOWS PHASE 3
BOZEMAN, MONTANA
BASIS OF DESIGN REPORT
2/17/22
B14-008 Trout Meadows Phase 3 Page 1 of 3
TROUT MEADOWS PHASE 3
DESIGN REPORT
February 2022
Purpose and Introduction
The purpose of this report is to explain how water, sanitary sewer, and storm drainage
improvements will be designed or have been previously designed to meet the City of
Bozeman requirements and Montana Public Works Standard Specifications (MPWSS) to
provide service to the Trout Meadows Phase 3 apartment project proposed within the
Cattail Lake Subdivision in Bozeman, Montana. The report will provide information on
the detailed design of the above-mentioned infrastructure.
Trout Meadows Phase 3 is a continuation of the overall Trout Meadows apartment
development and is located on 4 existing multi-family lots with the Cattail Lake
Subdivision. The north lots are located south of Trout Meadows Road and west of Davis
Lane. The south lots are located north of Catamount Street between Fen Way and
Blackbird Drive. The 4 lots were originally platted as 21 single-family lots (10 detached
homes and 11 attached townhomes). A change in the development plan from 21 single-
family lots to 4 multi-family lots was approved in 2014 with Amended Plat J-471-A. Each
lot will contain one multi-family building with the following dwelling units:
• Lot 1A, Block 5: 1-bedroom apartments (6), 2-bedroom apartments (12)
• Lot 6A, Block 5: 1-bedroom apartments (6), 2-bedroom apartments (12)
• Lot 1A, Block 6: 1-bedroom apartments (8), 2-bedroom apartments (4)
• Lot 7A, Block 6: 1-bedroom apartments (8), 2-bedroom apartments (4)
The lots are currently vacant. Proposed site improvements include the construction of
apartment buildings with associated parking, landscape, hardscape, utility services, and
on-site stormwater management systems.
Off-site infrastructure improvements are not proposed with this project. The water,
sewer, streets, and storm drain infrastructure for this development was installed with the
original Cattail Lake Subdivision. Installation of new, or extension of existing, water,
sewer, or storm drain mains is not required for Trout Meadows Phase 3.
Design Report
Water
As mentioned above, existing water mains have already been extended to each lot
during construction of the Cattail Lake Subdivision. Existing water improvements were
reviewed and approved by the City of Bozeman and the Montana Department of
Environmental Quality (DEQ) and were installed in accordance with the approved plans
and specifications. Several existing 3/4" water service lines were originally stubbed to
the single family lots prior to the plat amendment. These services were properly
abandoned and new 1.5” domestic and 4” fire service lines were stubbed into each of
the 4 multi-family lots in 2017. These services will be extended to each multi-family
structure with the building improvements in accordance with the City of Bozeman Design
Standards and Modifications to Montana Public Works Standard Specifications
B14-008 Trout Meadows Phase 3 Page 2 of 3
(MPWSS). The estimated domestic water demands for the project are provided in
Appendix A as calculated in accordance with C.O.B. DSSP Section V.A.4.
Sewer
As mentioned above, existing sewer mains have already been extended to each lot
during construction of the Cattail Lake Subdivision. Existing sewer improvements were
reviewed and approved by the City of Bozeman and the Montana Department of
Environmental Quality (DEQ) and were installed in accordance with the approved plans
and specifications. Several existing 4" sewer service lines were originally stubbed to the
single family lots prior to the plat amendment. One existing 4” sewer service line will be
extended to each multi-family structure in accordance with the City of Bozeman Design
Standards and Modifications to Montana Public Works Standard Specifications
(MPWSS).
The estimated sewer demands for each building are provided in Appendix B as
calculated in accordance with C.O.B. DSSP Section V.B. and using information from the
City’s 2015 Wastewater Facilities Plan.
Storm Drainage
An engineering design report discussing storm water conveyance, retention/detention,
and infrastructure was completed in July of 2006 under the title “Design Report, Cattail
Lake Subdivision, Bozeman, Montana.” This report provides details on design storms,
stormwater pond sizing, and storm drain sizing for the entire Cattail Lake development.
The Trout Meadows Phase 3 project areas were included within the stormwater design
for the subdivision using an assumed post-development runoff coefficient “C-Value” of
0.5. Therefore, an analysis was required to compare the assumed values with actual
designed conditions and verify adequate storage volume and conveyance capacity
exists within the subdivision stormwater system to accommodate this development.
Copies of the relevant pages from the 2006 Cattail Lake Subdivision design report are
included in Appendix C with annotation clarifying the values used in this evaluation.
Additionally, some on-site stormwater retention facilities or existing pond modifications
have been designed to address the current standards with respect to capturing the first
1/2" of rainfall from these sites.
Both the north and south project sites consist of vacant land that slopes generally to the
north that were included within the West Pond drainage basin in the original 2006 design
report. Using measurements of the actual designed impervious areas for these sites, it
was determined that they will have a slightly higher composite “C-Value” than the
assumed 0.5. Therefore, higher runoff flow rates and volumes would be expected from
these sites than what was originally planned for with the subdivision stormwater
infrastructure design.
However, in order to address the first 1/2" of rainfall requirement, stormwater retention
chambers at the south site and additional pond retention volume at the north site have
been designed that also result in a reduction of runoff volumes and flow rates from these
sites before entering the subdivision storm system. The following table summarizes the
assumed vs. actual runoff volumes and flow rates from the Trout Meadows Phase 3
B14-008 Trout Meadows Phase 3 Page 3 of 3
project areas, and demonstrates how the addition of on-site retention facilities to address
the first 1/2" of rainfall also reduce the off-site 10-yr runoff storage volumes and 25-yr
flow rates. This comparison demonstrates that the subdivision storm drain and pond
system is adequate to support this development in combination with the new or
improved on-site retention facilities.
(See also the drainage basin map in Appendix C).
Table 1 – Assumed vs. Actual Site Runoff Comparison
Drainage
Basin
RRV
First 0.5”
(CF)
RRV Storage Facility
South 1,471 New Subsurface Infiltration Chambers
North (a) 612 Over-excavate existing (Pond 13) to 6” below outfall
North (b) 379 Surplus storage in existing (West Pond) 9” below outfall
Drainage
Basin
C-Value
10-Yr Runoff 1
Volume V10
(CF)
25-Yr Runoff 1
Flow Rate Q25
(CFS)
Assumed Actual Assumed Actual Assumed Actual
South 0.50 0.60 1,864 756 1.10 0.81
North (a) 0.50 0.68 673 303 0.34 0.21
North (b) 0.50 0.48 618 588 0.31 0.29
1. Off-site runoff volumes and flow rates after initial on-site RRV (First 0.5”) capture.
Stormwater design calculations for the “C-Value” determinations, RRV (First 0.5”)
retention volumes, existing pond volume analysis, off-site runoff flow rates, and new
storm pipe conveyance capacities are provided in Appendix C.
Groundwater
Geotechnical drilling investigations were conducted for the Cattail Lake Subdivision that
also included seasonal high groundwater monitoring at several locations in 2004 and
2006. The monitoring locations and highest recorded groundwater elevations are shown
on the boring location map provided in Appendix C. A groundwater surface was
interpolated between these monitoring locations to estimate groundwater levels at the
proposed stormwater facility locations. The estimated seasonal high groundwater
elevations are shown on the drainage basin map as they relate to the subsurface
infiltration chambers and the proposed over-excavation of Pond 13, and they are
expected to be sufficiently below these features to allow for a successful
retention/infiltration strategy at the site.
APPENDIX A
Water Calculations
Trout Meadows Phase 3
Stormwater Design Calculations
Date: 12.16.2022
Water Demand Calculation
Domestic Water Demand - North Buildings:
Residential Use:
Residential Units =24 units
People =50.6 people (2.11 people/unit per COB Design Standards)
Residential Flow =8,609 GPD (170 gpcd per COB Design Standards)
Peak Hour Demand:
Average Day Demand =8,609 GPD (All Uses)
Average Day Demand =6.0 gpm (GPD / 1,440 minutes)
Maximum Day Demand =13.8 gpm (Ave. Day x Peaking Factor = 2.3)
Peak Hour Demand =17.9 gpm (Ave. Day x Peaking Factor = 3)
Domestic Water Demand - South Buildings:
Residential Use:
Residential Units =36 units
People =76.0 people (2.11 people/unit per COB Design Standards)
Residential Flow =12,913 GPD (170 gpcd)
Peak Hour Demand:
Average Day Demand =12,913 GPD (All Uses)
Average Day Demand =9.0 gpm (GPD / 1,440 minutes)
Maximum Day Demand =20.6 gpm (Ave. Day x Peaking Factor = 2.3)
Peak Hour Demand =26.9 gpm (Ave. Day x Peaking Factor = 3)
APPENDIX B
Sewer Calculations
Trout Meadows Phase 3
Stormwater Design Calculations
Date: 12.16.2022
Sewer Demand Calculation
Average Day Sewer Demand - NW Building Block 6, Lot 6A:
Residential Use:
Residential Units =12 units
People =26.0 people (2.17 people/unit)
Residential Flow =1,677 GPD (64.4 gpcd)
Average Day Sewer Demand - NE Building Block 6, Lot 7A:
Residential Use:
Residential Units =12 units
People =26.0 people (2.17 people/unit)
Residential Flow =1,677 GPD (64.4 gpcd)
Average Day Sewer Demand - SW Building Block 5, Lot 1A:
Residential Use:
Residential Units =18 units
People =39.1 people (2.17 people/unit)
Residential Flow =2,515 GPD (64.4 gpcd)
Average Day Sewer Demand - SE Building Block 5, Lot 6A:
Residential Use:
Residential Units =18 units
People =39.1 people (2.17 people/unit)
Residential Flow =2,515 GPD (64.4 gpcd)
Total Development Average Day Demostic Demand:
Total Domestic =8,385 GPD
Total Development Infiltration Flow:
Property Size =2.11 acres (All lots)
Infiltration Flow =317 GPD (150 gpd/acre per COB Design Standards)
Total Development Peak Sewer Flow:
Average Day Demand =8,385 GPD (residential + commercial)
P =0.130 (population/1,000)
Peaking Factor =4.21
Peak Sewer Demand =35,304 GPD (avg. day demand)*(peaking factor)
+ Infiltration Flow =317 GPD (not peaked)
Total Peak Flow =35,620 GPD (residential + commercial + infiltration)
Peak Sewer Flow =24.74 GPM (peak flow)/(24 hrs/day)/(60 min/hr)
Values per C.O.B.
2015 Wastewater Facilities Plan
Values per C.O.B.
2015 Wastewater Facilities Plan
Values per C.O.B.
2015 Wastewater Facilities Plan
Values per C.O.B.
2015 Wastewater Facilities Plan
𝑄𝑚𝑎𝑥
𝑄𝑎𝑣𝑔
=18 +𝑠ℎ𝑛𝑠𝑠𝑎𝑛𝑑𝑠𝑛𝑑𝑛𝑑𝑛𝑛𝑙𝑑1/2
4 +𝑠ℎ𝑛𝑠𝑠𝑎𝑛𝑑𝑠𝑛𝑑𝑛𝑑𝑛𝑛𝑙𝑑1/2
Trout Meadows Phase 3
Stormwater Design Calculations
Date: 12.16.2022
4" Sewer Service Pipe Capacity
Input Values
d =0.33 ft =4"
y =0.250 ft =75%
Calculated Values (Equations from Fluid Mechanics by Chow)
Theta (Θ)4.19 rad 2*arccos(1-y/(d/2))
Area (A)0.07 ft2 (1/8)*(Θ-sinΘ)d2
Wetted Perimeter (P)0.70 ft 0.5Θd
Hydraulic Radius (R )0.10 ft (.25)*(1-(sinΘ)/Θ)d
Top Width (T)0.29 ft (sin 0.5Θ)d
Mannings Equation (Equation from Fundamentals of Mechanics by Munson)
n =0.013 (per COB Design Standards)
S0 =0.0208 ft/ft (1/4" per foot for 4" services)
Q =0.25 cfs Q = 1.49/n*A*R2/3*S00.5
Q =112.42 gpm Q gpm = (Q cfs)(7.48 gal/ft3)(60 sec/min)
V =3.58 ft/s V = Q/A
Results A 4" diameter sewer sewervce at the min. 1/4" per foot slope flowing
75% full has the capacity for 112 gpm.
J:\2014\B14-008 Trout Meadows Phase 3\DOCUMENTS\DESIGN REPORT\B14-008 Water & Sewer Calcs.xls1 OF 1
Appendix C
Storm Water Calculations
• Pages from 2006 Cattail Lake Subdivision Design Report
• Trout Meadows Phase 3 Stormwater Calculations
• Groundwater Monitoring Results
Pages from 2006 Cattail Lake Subdivision Design Report
The bottom 9"volume of the West SW Pond
is retained and infiltrated through he bottom
of the wetland feature.
1234567811121314109a9b9cPOND13WESTPONDEASTPONDDAVISPOND1b1aBASIN AREA (SF) AREA (ACRE)11a1b23456789a9b9c101112131420089.409326.9729452.1489801.7923595.9331758.56148856.1572690.5829093.1022123.8326647.9427156.39224774.2920905.09103586.7117733.20170573.3623955.360.4610.2140.6762.0620.5420.7293.4171.6690.6680.5080.6120.6235.1600.4792.3780.4073.9160.550SHEET OF CAD NO.DESIGNED BY:QUALITY CHECK:JOB NO.FIELDBOOKDRAWN BY:DATE:THOMAS, DEAN & HOSKINS, INC.
ENGINEERING CONSULTANTS
REVISIONS
BY
BY
BY
DATE
DATE
DATE
DESCR
DESCR
DESCR
.DWGCRESTVIEW LAKE SUBDIVISION
BOZEMAN, MONTANA
DRAINAGE BASIN MAP1
1557drainB05-0577.25.06JLNDJCSouth Site Ph3NorthSite Ph3WestSW PondBasinsaccountedforinWest SWPond:
Assumed post-development
C-Values for the Phase 3 Lots.
Assumed 25-yr Peak Flow Tc
values for the Phase 3 Lots.
Iteratedstormdurationresultinginmax.requiredstoragevolumeintheWest SWPond
Trout Meadows Phase 3 Stormwater Calculations
CATAMOUNT STREETBLACKBIRD DRIVE
FEN WAYBLOCK 5LOT 1ABLOCK 5LOT 6AOSPA 2BLOCK 6LOT 6ABLOCK 6LOT 7AOSPA 1AFEN WAYDAVIS LANETROUT MEADOWS ROADCATTAIL LAKEREVISIONSHEETDESIGNED BY:QUALITY CHECK:JOB NO.FIELDBOOKDRAWN BY:DATE:B14-008 SW BASIN MAPREV DATE NOT FORCONSTRUCTION
TROUT MEADOWS PHASE 3
BOZEMAN, MONTANA
DRAINAGE BASIN MAP
SOUTH SITES (BLOCK 5, LOTS 1A & 6A)B14-0082.16.22.DWGEX-1CJCCJCEngineering
234 E. BABCOCK ST., SUITE 3 • BOZEMAN, MONTANA 59715
406.586.0277 • tdhengineering.com BASIN - SOUTH:CAVE = 0.60A = 1.33 AC.RRV = 1,471 CFV10 = 756 CF*Q25 = 0.81 CFS**(RELEASED OFF-SITEAFTER RRV CAPTURE)BASIN - NORTH (A):CAVE = 0.68A = 0.48 AC.RRV = 612 CFV10 = 303 CF*Q25 = 0.21 CFS**(RELEASED OFF-SITEAFTER RRV CAPTURE)BASIN - NORTH (B):CAVE = 0.48A = 0.44 AC.RRV = 379 CFV10 = 588 CFQ25 = 0.29 CFSSOUTH SITE DRAINAGE BASINNORTH SITE DRAINAGE BASINS
Trout Meadows Phase 3
Stormwater Design Calculations
Date: 12.16.2022
Basin Runnoff Coeff. (C-Value) Determinations
Rational Formula "C" Values Per MTDEQ 8 "C"
Impervious Area/Pond Surface 0.9
Gravel Area 0.8
Unimproved Area 0.3
Lawn/landscape 0.1
Assumed Post-Development Basin C Values (per 2006 Subdivision Design Report):
Basin ID Basin Description Total Area
(SF)
Total Area
(Acres)
Impervious
Area (SF)
Gravel
Area (SF)
Unimproved
Area (SF)
Landscape
Area (SF)
Composite
Cave
South Block 5 - Lots 1A, 6A, OSPA 2 57,937 1.33 0.50
North (a)Block 6 - Lots 6A, 7A, OSPA 1A (south half)20,915 0.48 0.50
North (b)Block 6 - Lots 6A, 7A, OSPA 1A (north half)19,207 0.44 0.50
Actual Post-Development Basin C Values:
Basin ID Basin Description Total Area
(SF)
Total Area
(Acres)
Impervious
Area (SF)
Gravel
Area (SF)
Unimproved
Area (SF)
Landscape
Area (SF)
Composite
Cave
South Block 5 - Lots 1A, 6A, OSPA 2 57,937 1.33 36,014 0 0 21,923 0.60
North (a)Block 6 - Lots 6A, 7A, OSPA 1A (south half)20,915 0.48 15,165 0 0 5,750 0.68
North (b)Block 6 - Lots 6A, 7A, OSPA 1A (north half)19,207 0.44 9,030 0 0 10,177 0.48
Trout Meadows Phase 3
Stormwater Design Calculations
Date: 12.16.2022
Basin RRV (First 0.5") Calculations
Post-Development Condition:
Basin #Description Total
Area (SF)
Total
Area (AC)
Impervious
Area (SF)
Gravel
Area (SF)
Unimproved
Area (SF)
Landscape
Area (SF)
South Block 5 - Lots 1A, 6A, OSPA 2 57,937 1.33 36,014 0 0 21,923
Runoff Reduction Volume (First 0.5" of Rainfall):
P =0.5 Inches (Water Quality Rainfall Depth)
Rv =0.61 (Dimensionless Runoff Coefficient, Rv=0.05+0.9(I)
I =62.2%(Percent Impervious Area Draining to Facility)
A =1.33 AC (Total Drainage Area)
RRV =0.034 AC-FT (Runoff Reduction Volume)*
1,471 CF
Post-Development Condition:
Basin #Description Total
Area (SF)
Total
Area (AC)
Impervious
Area (SF)
Gravel
Area (SF)
Unimproved
Area (SF)
Landscape
Area (SF)
North (a)South 1/2 of Block 6 - Lots 6A, 7A, OSPA 1A 20,915 0.48 15,165 0 0 5,750
Runoff Reduction Volume (First 0.5" of Rainfall):
P =0.5 Inches (Water Quality Rainfall Depth)
Rv =0.70 (Dimensionless Runoff Coefficient, Rv=0.05+0.9(I)
I =72.5%(Percent Impervious Area Draining to Facility)
A =0.48 AC (Total Drainage Area)
RRV =0.014 AC-FT (Runoff Reduction Volume)*
612 CF
Post-Development Condition:
Basin #Description Total
Area (SF)
Total
Area (AC)
Impervious
Area (SF)
Gravel
Area (SF)
Unimproved
Area (SF)
Landscape
Area (SF)
North (b)North 1/2 of Block 6 - Lots 6A, 7A, OSPA 1A 19,207 0.44 9,030 0 0 10,177
Runoff Reduction Volume (First 0.5" of Rainfall):
P =0.5 Inches (Water Quality Rainfall Depth)
Rv =0.47 (Dimensionless Runoff Coefficient, Rv=0.05+0.9(I)
I =47.0%(Percent Impervious Area Draining to Facility)
A =0.44 AC (Total Drainage Area)
RRV =0.009 AC-FT (Runoff Reduction Volume)*
379 CF
*RRV = PRvA/12 per Montana Post-Construction Storm Water BMP Design Guidance Manual Eq. 3-1
Trout Meadows Phase 3
Stormwater Design Calculations
Date: 12.16.2022
Subdivision Pond Storage Volume Comparison
Assumed 10-yr Runoff Volume Provided in the West Pond for each site (per 2006 Subdivision Design Report):
Basin #Basin Description Total Area
(SF)
Total Area
(Acres)
(Assumed)
Cave
Tc1
(min)
10-yr
i
(in/hr)
Flow
Q10
(cfs)
Volume
V10
(cf)
South Block 5 - Lots 1A, 6A, OSPA 2 57,937 1.33 0.50 105.06 0.445 0.30 1,864
North (a)Block 6 - Lots 6A, 7A, OSPA 1A (south half)20,915 0.48 0.50 105.06 0.445 0.11 673
North (b)Block 6 - Lots 6A, 7A, OSPA 1A (north half)19,207 0.44 0.50 105.06 0.445 0.10 618
Total Storage Provided in West Pond =3,155
Actual 10-yr Runoff Volume Needed in the West Pond:
Basin #Basin Description Total Area
(SF)
Total Area
(Acres)
(Actual)
Cave
Tc1
(min)
10-yr
i
(in/hr)
Flow
Q10
(cfs)
Volume
V10
(cf)
South Block 5 - Lots 1A, 6A, OSPA 2 57,937 1.33 0.60 105.06 0.445 0.35 2,227
Less RRV (First 0.5") Captured On-Site =1,471
Storage Volume Needed in West Pond =756
North (a)Block 6 - Lots 6A, 7A, OSPA 1A (south half)20,915 0.48 0.68 105.06 0.445 0.15 915
Less RRV (First 0.5") Captured On-Site =612
Storage Volume Needed in West Pond =303
North (b)Block 6 - Lots 6A, 7A, OSPA 1A (north half)19,207 0.44 0.48 105.06 0.445 0.09 588
Less RRV (First 0.5") Captured On-Site =0
Storage Volume Needed in West Pond =588
Total Storage Needed in West Pond =1,647
Total Surplus Storage Provided in West Pond =1,508
1. Tc is the interpolated storm duration resulting in the maximum required pond storage from the 2006 Subdivision Design Report.
𝑖10 =0.64 ⋅𝑇𝑐−.65
Trout Meadows Phase 3
Stormwater Design Calculations
Date: 12.16.2022
Subdivision Design 25-yr Flow Comparison
Assumed 25-yr Runoff Flow Rate for each site (per the 2006 Subdivision Design Report):
Basin #Basin Description Total Area
(SF)
Total Area
(Acres)
(Assumed)
Cave
CCf
(Cf = 1.1)
Tc1
(min)
25 yr
i
(in/hr)
Flow
Q25
(cfs)
South Block 5 - Lots 1A, 6A, OSPA 2 57,937 1.33 0.50 0.55 21.59 1.50 1.10
North (a)Block 6 - Lots 6A, 7A, OSPA 1A (south half)20,915 0.48 0.50 0.55 28.05 1.27 0.34
North (b)Block 6 - Lots 6A, 7A, OSPA 1A (north half)19,207 0.44 0.50 0.55 28.05 1.27 0.31
Actual 25-yr Runoff Flow Rate for each site:
Basin #Basin Description Total Area
(SF)
Total Area
(Acres)
(Actual)
Cave
CCf
(Cf = 1.1)
Tc1
(min)
25 yr
i
(in/hr)
Flow
Q25
(cfs)
South Block 5 - Lots 1A, 6A, OSPA 2 57,937 1.33 0.60 0.66 21.59 1.50 1.31
Q25 after RRV (First 0.5") Capture (see hydrograph) =0.81
North (a)Block 6 - Lots 6A, 7A, OSPA 1A (south half)20,915 0.48 0.68 0.75 28.05 1.27 0.46
Q25 after RRV (First 0.5") Capture (see hydrograph) =0.21
North (b)Block 6 - Lots 6A, 7A, OSPA 1A (north half)19,207 0.44 0.48 0.52 28.05 1.27 0.29
1. Tc is the reported value for 25-yr Drainage Basin Runoff Calculations in the 2006 Subdivision Design Report.
𝑖25 =0.78 ⋅𝑇𝑐
−.64
Hydrology Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc.Wednesday, Feb 16 2022
South Basin 25-yr Flow Rate after RRV Capture
Hydrograph type = Rational Peak discharge (cfs) = 1.365
Storm frequency (yrs) = 25 Time interval (min) = 1
Drainage area (ac) = 1.330 Runoff coeff. (C) = 0.66
Rainfall Inten (in/hr) = 1.555 Tc by User (min) = 22
IDF Curve = BZN IDF.IDF Rec limb factor = 1.00
Hydrograph Volume = 1,801 (cuft); 0.041 (acft)
0 5 10 15 20 25 30 35 40 45
Q (cfs)
0.00 0.00
1.00 1.00
2.00 2.00
Q (cfs)
Time (min)
Runoff Hydrograph
25-yr frequency
Runoff Hyd - Qp = 1.36 (cfs)
Q25 = 0.81 after
RRV capture
= 1,471 CF
Hydraflow Express - South Basin 25-yr Flow Rate after RRV Capture - 02/16/22 1
Runoff Hydrograph Outflow Hydrograph
Time Q Volume Q
(min)(cfs)(cuft)(cfs)
0 0.000 0.00 0.000
1 0.062 1.86 0.000
2 0.124 7.44 0.000
3 0.186 16.75 0.000
4 0.248 29.77 0.000
5 0.310 46.52 0.000
6 0.372 66.99 0.000
7 0.434 91.18 0.000
8 0.496 119.09 0.000
9 0.558 150.73 0.000
10 0.620 186.08 0.000
11 0.682 225.16 0.000
12 0.744 267.96 0.000
13 0.806 314.48 0.000
14 0.868 364.72 0.000
15 0.930 418.69 0.000
16 0.992 476.37 0.000
17 1.054 537.78 0.000
18 1.116 602.91 0.000
19 1.179 671.76 0.000
20 1.241 744.33 0.000
21 1.303 820.62 0.000
22 1.365 900.64 0.000
23 1.303 980.65 0.000
24 1.241 1,057 0.000
25 1.179 1,130 0.000
Hydraflow Express - South Basin 25-yr Flow Rate after RRV Capture - 02/16/22 2
Runoff Hydrograph Outflow Hydrograph
Time Q Volume Q
(min)(cfs)(cuft)(cfs)
26 1.116 1,198 0.000
27 1.054 1,263 0.000
28 0.992 1,325 0.000
29 0.930 1,383 0.000
30 0.868 1,437 0.000
31 0.806 1,487 0.000
32 0.744 1,533 0.000
33 0.682 1,576 0.000
34 0.620 1,615 0.000
35 0.558 1,651 0.000
36 0.496 1,682 0.000
37 0.434 1,710 0.000
38 0.372 1,734 0.000
39 0.310 1,755 0.000
40 0.248 1,772 0.000
41 0.186 1,785 0.000
42 0.124 1,794 0.000
43 0.062 1,799 0.000
44 0.000 1,801 0.000
Hydrology Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc.Wednesday, Feb 16 2022
North (a) Basin 25-yr Flow Rate after RRV Capture
Hydrograph type = Rational Peak discharge (cfs) = 0.415
Storm frequency (yrs) = 25 Time interval (min) = 1
Drainage area (ac) = 0.460 Runoff coeff. (C) = 0.7
Rainfall Inten (in/hr) = 1.289 Tc by User (min) = 28
IDF Curve = BZN IDF.IDF Rec limb factor = 1.00
Hydrograph Volume = 697 (cuft); 0.016 (acft)
0 10 20 30 40 50 60
Q (cfs)
0.00 0.00
0.05 0.05
0.10 0.10
0.15 0.15
0.20 0.20
0.25 0.25
0.30 0.30
0.35 0.35
0.40 0.40
0.45 0.45
0.50 0.50
Q (cfs)
Time (min)
Runoff Hydrograph
25-yr frequency
Runoff Hyd - Qp = 0.42 (cfs)
Q25 = 0.21 after
RRV capture
= 612 CF
Hydraflow Express - North (a) Basin 25-yr Flow Rate after RRV Capture - 02/16/22 1
Runoff Hydrograph Outflow Hydrograph
Time Q Volume Q
(min)(cfs)(cuft)(cfs)
0 0.000 0.00 0.000
1 0.015 0.44 0.000
2 0.030 1.78 0.000
3 0.044 4.00 0.000
4 0.059 7.12 0.000
5 0.074 11.12 0.000
6 0.089 16.01 0.000
7 0.104 21.79 0.000
8 0.119 28.46 0.000
9 0.133 36.02 0.000
10 0.148 44.48 0.000
11 0.163 53.81 0.000
12 0.178 64.04 0.000
13 0.193 75.16 0.000
14 0.208 87.17 0.000
15 0.222 100.07 0.000
16 0.237 113.86 0.000
17 0.252 128.53 0.000
18 0.267 144.10 0.000
19 0.282 160.56 0.000
20 0.297 177.90 0.000
21 0.311 196.14 0.000
22 0.326 215.26 0.000
23 0.341 235.27 0.000
24 0.356 256.18 0.000
25 0.371 277.97 0.000
Hydraflow Express - North (a) Basin 25-yr Flow Rate after RRV Capture - 02/16/22 2
Runoff Hydrograph Outflow Hydrograph
Time Q Volume Q
(min)(cfs)(cuft)(cfs)
26 0.385 300.65 0.000
27 0.400 324.22 0.000
28 0.415 348.68 0.000
29 0.400 373.15 0.000
30 0.385 396.72 0.000
31 0.371 419.40 0.000
32 0.356 441.19 0.000
33 0.341 462.10 0.000
34 0.326 482.11 0.000
35 0.311 501.23 0.000
36 0.297 519.47 0.000
37 0.282 536.81 0.000
38 0.267 553.27 0.000
39 0.252 568.84 0.000
40 0.237 583.51 0.000
41 0.222 597.30 0.000
42 0.208 610.20 0.000
43 0.193 622.21 0.000
44 0.178 633.33 0.000
45 0.163 643.55 0.000
46 0.148 652.89 0.000
47 0.133 661.34 0.000
48 0.119 668.91 0.000
49 0.104 675.58 0.000
50 0.089 681.36 0.000
51 0.074 686.25 0.000
Hydraflow Express - North (a) Basin 25-yr Flow Rate after RRV Capture - 02/16/22 3
Runoff Hydrograph Outflow Hydrograph
Time Q Volume Q
(min)(cfs)(cuft)(cfs)
52 0.059 690.25 0.000
53 0.044 693.37 0.000
54 0.030 695.59 0.000
55 0.015 696.92 0.000
56 0.000 697.37 0.000
Trout Meadows Phase 3
Stormwater Design Calculations
Date: 12.16.2022
25-yr Pipe Conveyance Flows
25-Year Flow Calcs:
Location Basin Size
(Acres)Cave CCf
Tc
(min)
25 yr
i
(in/hr)
Flow
Q25
(cfs)
SD Inlet Pipe Valley (12")0.42 0.60 0.66 5 3.83 1.06
SD Inlet Pipe West (12")0.46 0.60 0.66 5 3.83 1.16
SD Pipe to Chambers West (12")2.22
SD Inlet Pipe East (12")0.46 0.60 0.66 5 3.83 1.16
Combined Inlet Flows (Above) =
IDF curve equation for 25-yr storm
Tc = time to concentration in hours
Rational Method
Cf = 1.1 for 25-yr eventAiCCQf=
64.
25 78.0 −=cTi
Trout Meadows Phase 3
Stormwater Design Calculations
Date: 12.16.2022
12" Storm Pipe Capacity
Input Values
d =1.00 ft =12"
y =0.940 ft =94%
Calculated Values (Equations from Fluid Mechanics by Chow)
Theta (Θ)5.29 rad 2*arccos(1-y/(d/2))
Area (A)0.77 ft2 (1/8)*(Θ-sinΘ)d2
Wetted Perimeter (P)2.65 ft 0.5Θd
Hydraulic Radius (R )0.29 ft (.25)*(1-(sinΘ)/Θ)d
Top Width (T)0.47 ft (sin 0.5Θ)d
Mannings Equation (Equation from Fundamentals of Mechanics by Munson)
n =0.013 (per COB Design Standards)
S0 =0.0050 ft/ft (0.5% Min. Slope)
Q =2.72 cfs Q = 1.49/n*A*R2/3*S00.5
Q =1219.5 gpm Q gpm = (Q cfs)(7.48 gal/ft3)(60 sec/min)
V =3.55 ft/s V = Q/A
Results A 12" diameter storm pipe flowing 94% full at a min. slope of 0.5%
has a carrying capacity of 2.72 cfs.
J:\2014\B14-008 Trout Meadows Phase 3\DOCUMENTS\DESIGN REPORT\B14-008 Storm Water Calcs.xls 1 OF 1
Groundwater Monitoring Results
South Site Ph3NorthSite Ph3High GWMeasurements:2004: -4.58 (4635.29)2006:-4.11 (4635.76)High GWMeasurements:2004: -2.48 (4637.10)2006: -2.66 (4636.92)High GWMeasurement:2006: -4.43 (4631.79)High GWMeasurements:2004: -5.26 (4627.39)2006: -5.25 (4627.40)TopofCattailLakeDesign = 4621.50
2004 GW Monitoring Data (Morrison Maierle)
TABLE 1
Cattail Lake Subdivision
Groundwater Monitoring
Survey Information TD&H
Monitor Well
Elevation
Top of
Pipe
Distance
to Ground
Ground
Elevation
Old MW#1 4634.13 1.25 4632.88
Old MW#2 4637.65 1.33 4636.32
Old MW#3 4641.37 1.50 4639.87
Old MW#4 4634.85 2.20 4632.65
Old MW#5 4641.37 1.79 4639.58
TP-101 4641.27 2.05 4639.22
TP-102 4637.39 1.69 4635.70
TP-106 4629.95 1.01 4628.94
TP-111 4637.89 1.67 4636.22
Initials MAE JJC MAE MAE
Date 6/15/2006 6/26/2006 7/20/2006 8/10/2006
Monitor Well
Old MW#1 9.73 Dry Dry Dry
GW Elevation 4624.40 n/a n/a n/a
bgs 8.48 Dry Dry Dry
Old MW#2 8.82 9 9.32 9.71
GW Elevation 4628.83 4628.65 4628.33 4627.94
bgs 7.49 7.67 7.99 8.38
Old MW#3 5.61 5.8 6.07 6.44
GW Elevation 4635.76 4635.57 4635.30 4634.93
bgs 4.11 4.30 4.57 4.94
Old MW#4 7.45 7.7 8.13 8.46
GW Elevation 4627.40 4627.15 4626.72 4626.39
bgs 5.25 5.50 5.93 6.26
Old MW#5 4.45 4.45 4.97 5.35
GW Elevation 4636.92 4636.92 4636.40 4636.02
bgs 2.66 2.66 3.18 3.56
TP-101 6.89 7.2 7.43 7.71
GW Elevation 4634.38 4634.07 4633.84 4633.56
bgs 4.84 5.15 5.38 5.66
TP-102 7.66 7.95 8.46 9
GW Elevation 4629.73 4629.44 4628.93 4628.39
bgs 5.97 6.26 6.77 7.31
TP-106 9 9.7 Dry Dry
GW Elevation 4620.95 4620.25 n/a n/a
bgs 7.99 8.69 Dry Dry
TP-111 6.1 6.2 6.52 6.96
GW Elevation 4631.79 4631.69 4631.37 4630.93
bgs 4.43 4.53 4.85 5.29
File: 502GWData.xls
2006 GW Monitoring Data (TD&H)