HomeMy WebLinkAboutStormwaterDesignReport_082521 STORMWATER MANAGEMENT
DESIGN REPORT
FOR:
TIDAL WAVE AUTO SPA
CAR WASH
BOZEMAN, MT
Prepared By:
M
MADISON
ENGINEERING
Madison Engineering
895 Technology Drive, Suite 203
Bozeman, MT 59718
(406) 586-0262
CHRIS '
AUGUST 2021 BISD:SM\
x No. 10 •�5 PIE:5
Project No. 21-105 "0NA1 ���
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TIDAL WAVE AUTO SPA CAR WASH
STORMWATER DESIGN REPORT
A. Introduction
This design report will give an overview of the proposed stormwater system for the proposed
1.05 acre site plan for `The Tidal Wave Car Wash' located on West Babcock. on Lot IA, Block
3 of the Kirk 41h Subdivision, Section 11, T02 S., R05E., Bozeman, Montana.
The proposed Bozeman Tidal Wave Auto Spa will be located at 2102 W. Babcock St. and
includes the construction of a +/-4,936 square foot express car wash with canopy covered
exterior vacuum spaces. The vacuum spaces will be located in a paved area east of the car wash.
Solid waste disposal will be stored in a roofed enclosure on the northeast portion of the property.
Landscaping will be provided at a minimum per the City of Bozeman standards.
The proposed storm water management system consists of overland sheet flow and roof drains
that will direct stormwater to on-site ADS Stormtech SC-740 retention/infiltration basin and
surface retention/infiltration basins located at the northwest and northeast corner of the site that
will consist of oversize cobbles. The infiltration basins will be excavated to native gravels to
permit maximum infiltration.
The following references were used in the preparation of this report:
a. COB Design Standards and Specifications Policy, 2004. Addendum#7
b. COB Modifications to Montana Public Works Standard Specifications (MPWSS)
The delineated basins, drainage plan, and grading plan are displayed on Exhibit A of this report.
B. Runoff and Basin Estimates
A 25-year, 2-hour design rainfall frequencies were used for calculating the pertinent basins
utilizing the rational method in accordance with the COB design standards. A runoff coefficient
C of 0.90 was used for impervious areas and a C value of 0.20 was used for landscaped areas.
The stormwater run-off calculations and basin volumes are shown on the calculations sheets
include in Appendix A of this report.
C. Conveyance Capacity
The proposed infrastructure improvements were designed to convey runoff per the City of
Bozeman standards. The conveyance structures includes roof drains that direct runoff to the
infiltration basins located throughout the site. Runoff from Basin C is surface flow to area drains
and the underground Stormtech SC-740 infiltration chambers. Runoff from Basin A & C will
sheet flow to the surface infiltration basins located at the northwest & northeast corner of the
site.
D. Native Gravel Infiltration Rates
A Geotechnical Report was prepared for this site by Allied Engineering in August of 2018. The
investigation found soils on the subject property to be typical for the area, including native sandy
gravels 3'-10' deep. The maximum depth of excavation was 10'. The proposed ADS Stormtech
SC-740 infiltration systems and the infiltration basins consisting of oversize cobbles will be
excavated to native gravels to permit maximum infiltration of stormwater. Backfill above the
ADS chambers to consist of clean, crushed angular stone and well-graded aggregate mixtures.
Refer to Details 1 & 2 on Sheet C2.0 for more information.
E. Stormwater Detention/Retention Volumes and Infiltration System Calculations
Ground water monitoring wells are being installed on the site and will be monitored to determine
groundwater depths. However, the Geotechnical Report indicates groundwater was at 8-9 feet
below existing ground at the time of the geotechnical site investigation.
All of the runoff is proposed to be conveyed to the retention basins and ultimately infiltrate into
native gravels. Two types of underground systems are proposed: ADS infiltration chambers and
a gravel infiltration basin.
It is estimated that the ground water will likely only rise 18"-24" from the August 2018
measured levels during peak groundwater in June. This is typical of groundwater fluctuation we
have observed over time. With the bottom of the proposed ADS basin at 4820.0 and the
estimated high ground water depth of 4818.0 it is anticipated groundwater will not infiltrate the
ADS basin. The surface infiltration basins are only a few feet deep.
The retention storage volumes were sized based on the 25-year 2-hour design rainfall frequency.
We felt a higher storm event was prudent as there is no viable off-site storm sewer to connect to
and no off-site discharge is proposed. The rational method was used to determine post-
development stormwater flows. The calculations for all stormwater storage facilities are included
in Appendix A. The proposed stormwater facilities reduce the post-development off-site runoff
rate to zero. All impervious surface runoff is conveyed to the infiltration retention and detention
systems and then infiltrates into the ground.
G. Stormwater Facility Maintenance
The proposed storm drainage facilities will be privately operated and maintained by the property
owner(s) of the on-site development. Included in Appendix B is a proposed maintenance
program for the ADS Stormtech infiltration systems.
Appendices
A. Retention System Calculations and ADS Stormtech SC-740 Chamber Design
B. Stormwater Maintenance Plan
APPENDICES
Appendix A — Retention System Calculations
and ADS Storm Chamber Design
Tidal Wave Car Wash 8/25/2021
Stormwater Calculations
Infiltration Basin A
Design Rainfall Freq. 25 year
OF coefficient a 0.78
OF coefficient b
OF coefficient n 0.64
Post-development Conditions
Contributing drainage area Square feet Acres C
Landscape 5867 0.13 0.20
Roof/walk 2075 0.05 0.90
Pavement 0.90
Total area 7942 0.18
Composite C 0.38
Retention Pond Calculations:
Q = CIA
C = 0.38 (post-development)
1 = 0.51 in/hr(10-yr, 2-hr storm)
A= 0.18 acres
Qpost- 0.04 cfs
Required retention storage(ft)= 256 ft3 (25-yr, 2-hr storm)
Propsoed Basin Volume held between contours
Contour Area(ft) Delta V(ft) Volume(ft)
4823.00 20
4823.50 180 50 50
4824.00 733 228 278
4824.50 1,576 577 856
Design storage at IS depth (ft)= 856
Proposed Basin Volume Provides Adequate Capacity
Tidal Wave Car Wash 8/25/2021
Stormwater Calculations
Infiltration Basin B
Design Rainfall Freq. 25 year
OF coefficient a 0.78
OF coefficient b
OF coefficient n 0.64
Post-development Conditions
Contributing drainage area Square feet Acres C
Landscape 7818 0.18 0.20
Roof/walk 0.90
Pavement 8504 0.20 0.90
Total area 16322 0.37
Composite C 0.56
Retention Pond Calculations:
Q = CIA
C = 0.56 (post-development)
1 = 0.51 in/hr(25-yr, 2-hr storm)
A= 0.37 acres
Qpost= 0.11 cfs
Required retention storage (ft)= 777 ft' (25-yr, 2-hr storm)
Propsoed Basin Volume held between contours
Contour Area (ft) Delta V(ft) Volume (ft)
4822.00 225
4822.50 495 180 180
4823.00 780 319 499
4823.50 1,422 551 1,049
Design storage at 1.5'depth (ft) = 1,049
Proposed Basin Volume Provides Adequate Capacity
Tidal Wave Car Wash 8/25/2021
Stormwater Calculations
Infiltration Basin C
Calculation of Required Volume for Storm Water Retention & Infitration System
Design Rainfall Freq. 25 year-2 Hour event
OF coefficient a 0.78
OF coefficient b
OF coefficient n 0.64
Post-development Calculations:
C
Areas(ft): Landscape 4,654 0.20
Roof/walk 3,980 0.90 Sidewalk
Pavement 13,982 0.90
Total: 22,616 0.76
Retention Basin Calculation:
Q=CIA
C= 0.76 (post-development)
I = 0.51 in/hr(25-yr,2-hr storm)
A= 0.52 acres
QpOst= 0.20 cfs
Required retention storage(U) = 1,441 ft3 (25-yr,2-hr storm)
Tidal Wave Basin-C.xls
Project: Tidal Wave Car Wash - Basin A �}
Chamber Model- v`ormTeeh.
SC-740 aeWflw.R.Wm -W&WQ nr
Units- Imperial p i t ions toy A 4rtn'sinrz of
uu ..
Number of chambers- •I2
Voids in the stone(porosity)- 40
Base of Stone Elevation- 5820 00 fl
Amount of Stone Above Chambers- 6 in El In
Perimeter Stone in Calculations
Amount of Stone Below Chambers- 6 in
Area of system- 10.14 sf Min.Area- 406 sf min.area
StormTech SC-740 Cumulative Storage Volumes
Height of Increme Single IncremeRW Inc. Incremental Cumulative
System Chamber Total Chamber Stone Ch &St Chamber Elevation
(inches) (cubic feet) (cubic feet) (cubic feet) (cubic feet) (cubic feet) (feet)
42 0.00 0.00 33.80 3380 1750.45 5823.50
41 0.00 0.00 33.80 33.80 1716.65 5823.42
40 0.00 0.00 33.80 33.80 1682.85 5823.33
39 0.00 0.00 33.80 33.80 1649.05 5823.25
38 0.00 0.00 33.80 33.80 1615.25 5823.17
37 0.00 0.00 33.80 33.80 1581.45 5823.08
36 0.05 0.66 33.54 34.20 1547.65 5823.00
35 0.16 1.96 33.02 34.97 1513.45 5822.92
34 0.28 3.38 32.45 35.83 1478.48 5822.83
33 0.60 7.25 30.90 38.15 1442.65 5822.75
32 0.80 9.62 29.95 39.57 1404.50 5822.67
31 0.95 11.41 29.24 40.64 1364.93 5822.58
30 1.07 12.89 28.64 41.54 1324.28 5822.50
29 1.18 14.17 28.13 42.30 1282.74 5822.42
28 1.27 15.19 27.72 42.91 1240.45 5822.33
27 1.36 16.26 27.30 43.56 1197.53 5822.25
26 1.45 17.45 26.82 44.27 1153.98 5822.17
25 1.52 18.30 26.48 44.78 1109.71 5822.08
24 1.58 18.99 26.20 45.19 1064.93 5822.00
23 1.64 19.71 25.92 45.62 1019.74 5821.92
22 1.70 20.39 25.64 46.04 974.11 5821.83
21 1.75 21.04 25.39 46.42 928.08 5821.75
20 1.80 21.63 25.15 46.78 881.65 5821.67
19 1.85 22.26 24.90 47.16 834.87 5821.58
18 1.89 22.72 24.71 47.43 787.72 5821.50
17 1.93 23.21 24.52 47.72 740.29 5821.42
16 1.97 23.70 24.32 48.02 692.56 5821.33
15 2.01 24.12 24.15 48.27 644.54 5821.25
14 2.04 24.54 23.98 48.52 596.27 5821.17
13 2.07 24.90 23.84 48.74 547.75 5821.08
12 2.10 25.26 23.70 48.96 499.01 5821.00
11 2.13 25.58 23.57 49.15 450.05 5820.92
10 2.15 25.85 23.46 49.31 400.90 5820.83
9 2.18 26.12 23.35 49.47 351.60 5820.75
8 2.20 26.38 23.25 49.63 302.12 5820.67
7 2.21 26.49 23.20 49.69 252.49 5820.58
6 0.00 0.00 33.80 33.80 202.80 5820.50
5 0.00 0.00 33.80 33.80 169.00 5820.42
4 0.00 0.00 33.80 33.80 135.20 5820.33
3 0.00 0.00 33.80 33.80 101.40 5820.25
2 0.00 0.00 33.80 33.80 67.60 5820.17
1 0.00 0.00 33.80 33.80 33.80 5820.08
WEST BABCOCK STREET
PROPOSED -
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ADJUSTMEENT
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TIDAL WAVE AUTO SPA EXHIBIT A
CAR WASH MADISON ENGINEERING DRAWN BY: CGB
895 TECHNOLOGY BLVD,SUITE 2W
STORM[WATER BASIN BOZEMAN,MT 59718 DATE: 8/25/21
EXHIBIT PHONE(406)586-0262 FAX(406)5S6-5740 PROJECT#21 -105
Appendix B — Stormwater Maintenance Plan
STORMWATER MAINTENANCE PLAN
Tidal Wave
The recommended stormwater facility maintenance is displayed below. It is the Property
Owner's responsibility for routine inspection and maintenance of the following items:
1. Keep roof drains and storm drain grates free of leaves,litter,and other debris.
2. Keep the inlets of the facilities free of leaves,rocks,and other debris.
3. Quarterly inspect and clean roof drains and infiltration systems.
4. Follow the O&M procedures for the Isolator Row Plus and ADS Stormtech SC-740
infiltration system.
Tidal Wave
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TUF KnT ALTOW" ROW PLUS
INTRODUCTION
An important component of any Stormwater Pollution Prevention Plan
is inspection and maintenance.The StormTech Isolator Row PLUS is
a technique to inexpensively enhance Total Suspended Solids(TSS)
and Total Phosphorus(TP)removal with easy access for inspection and
maintenance.
THE ISOLATOR ROW PLUS
The Isolator Row PLUS is a row of StormTech chambers,either SC-160,
SC-310,SC-310-3,SC-740,DC-780, MC-3500 or MC-4500 models,that is
surrounded with filter fabric and connected to a closely located manhole
for easy access.The fabric-wrapped chambers provide for settling and Looking down the Isolator Row PLUS from the
filtration of sediment as storm water rises in the Isolator Row PLUS and manhole opening,ADS PLUS Fabric is shown
ultimately passes through the filter fabric.The open bottom chambers between the chamber and stone base.
and perforated sidewalls(SC-310,SC-310-3 and SC-740 models)allow -- �
storm water to flow both vertically and horizontally out of the chambers.
Sediments are captured in the Isolator Row PLUS protecting the storage
areas of the adjacent stone and chambers from sediment accumulation.
ADS geotextile fabric is placed betweep the stone and the Isolator Row
PLUS chambers.The woven geotextile provides a media for stormwater
filtration,a durable surface for maintenance,prevents scour of the
underlying stone and remains intact during high pressure jetting.A non- i
woven fabric is placed over the chambers to provide a filter media for flows
passing through the perforations in the sidewall of the chamber.The non-
woven fabric is not required over the SC-160, DC-780,MC-3500 or MC-
4500 models as these chambers do not have perforated side walls.
The Isolator Row PLUS is designed to capture the"first flush"runoff and "
offers the versatility to be sized on a volume basis or a flow-rate basis.An
upstream manhole not only provides access to the Isolator Row PLUS but
includes a high/low concept such that stormwater flow rates or volumes
that exceed the capacity of the Isolator Row PLUS bypass through a
manifold to the other chambers.This is achieved with either an elevated
bypass manifold or a high-flow weir.This creates a differential between
the Isolator Row PLUS row of chambers and the manifold to the rest of the StormTech Isolator Row PLUS
system,thus allowing for settlement time in the Isolator Row PLUS. After with Overflow Spillway(not to
Stormwater flows through the Isolator Row PLUS and into the rest of the scale)
StormTech chamber system it is either exfiltrated into the soils below or
passed at a controlled rate through an outlet manifold and outlet control
structure.
The Isolator Row FLAMPTM(patent pending)is a flared end ramp apparatus
that is attached to the inlet pipe on the inside of the chamber end cap. The
FLAMP provides a smooth transition from pipe invert to fabric bottom. It
is configured to improve chamber function performance overtime by
enhancing outflow of solid debris that would otherwise collect at an end
of the chamber. It also serves to improve the fluid and solid flow into the
access pipe during maintenance and cleaning and to guide cleaning and
inspection equipment back into the inlet pipe when complete.
The Isolator Row PLUS may be part of a treatment train system.The design
of the treatment train and selection of pretreatment devices by the design
engineer is often driven by regulatory requirements.Whether pretreatment
is used or not,the Isolator Row PLUS is recommended by StormTech as an
effective means to minimize maintenance requirements and maintenance
costs.
Note:See the StormTech Design Manual for detailed information on designing
inlets for a StormTech system, including the Isolator Row PLUS.
ADVANCEDTHE MOST
ISOLATOR ROW PLUS
INSPECTION/MAINTENANCE
w1 INSPECTION
- 'k" ', The frequency of inspection and maintenance varies by location.A
routine inspection schedule needs to be established for each individual
location based upon site specific variables.The type of land use(i.e.
industrial,commercial,residential),anticipated pollutant load, percent
'®r imperviousness,climate,etc.all play a critical role in determining the
actual frequency of inspection and maintenance practices.
At a minimum,StormTech recommends annual inspections. Initially,the
Isolator Row PLUS should be inspected every 6 months for the first year
of operation. For subsequent years,the inspection should be adjusted
based upon previous observation of sediment deposition.
The Isolator Row PLUS incorporates a combination of standard manhole(s)and strategically located inspection
ports(as needed).The inspection ports allow for easy access to the system from the surface,eliminating the
need to perform a confined space entry for inspection purposes.
If upon visual inspection it is found that sediment has accumulated,a stadia rod should be inserted to determine
the depth of sediment.When the average depth of sediment exceeds 3 inches throughout the length of the
Isolator Row PLUS,clean-out should be performed.
MAINTENANCE
The Isolator Row PLUS was designed to reduce the cost of periodic maintenance.By"isolating"sediments to
just one row,costs are dramatically reduced by eliminating the need to clean out each row of the entire storage
bed. If inspection indicates the potential need for maintenance,access is provided via a manhole(s)located on
the end(s)of the row for cleanout. If entry into the manhole is required, please follow local and OSHA rules for a
confined space entries.
Maintenance is accomplished with the JetVac process.The JetVac process utilizes a high pressure water nozzle
to propel itself down the Isolator Row PLUS while scouring and suspending sediments.As the nozzle is retrieved,
the captured pollutants are flushed back into the manhole for vacuuming.Most sewer and pipe maintenance
companies have vacuum/JetVac combination vehicles.Selection of an appropriate JetVac nozzle will improve
maintenance efficiency. Fixed nozzles designed for culverts or large diameter pipe cleaning are preferable.Rear
facing jets with an effective spread of at least 45"are best.StormTech recommends a maximum nozzle pressure
of 2000 psi be utilized during cleaning. Most JetVac reels have 400 feet of hose allowing maintenance of an
Isolator Row PLUS up to 50 chambers long.The JetVac process shall only be performed on StormTech Isolator
Row PLUS that have ADS PLUS Fabric(as specified by StormTech)over their angular base stone.
StormTech Isolator Row PLUS(not to scale)
Note:Non-woven fabric is only required over the inlet pipe connection into the end cap for SC-160LP,DC-780,MC-3500 and MC-4500 chamber
models and is not required over the entire Isolator Row PLUS.
B11CIffILL MATERIAL
COVER ENTIRE ISOLATOR ROW WITH ADS OPTIONAL INSPECT ION PORT
GEOSTNTHV ICS 60IT NON.M0VEN GEOTEI(TILE SC-740 CHART.
B DA m)MIN WOE '
ELEVATED BYPASS MANIFOLD
'
1_15
t� SC-740 END CAP
\` V
t
NNW
SUMP DEPTH TBD SY CAir�eAsw _ _ _ _ _ ----------
SRE DESIGN ENGINEER OR IRAWIQE .
(N'LBW—1 YIN RECOMMENDED) 'I
24'(i USE FA TOR YPE ACCESS PIPE END CAD ONE LAYER OF ADS PLUS GEOTEXTILE BETWEEN
USE FACTORY PRECABRIGTED END CAP
WI7N FWP PoYLTR 1CTS39FE74ft FOUNDATION STONE AND C/OUS ERS
FABRIC
S'(13 m)YIN WIDE CONTINUOUS FABRIC WITHOUT BEAUS
Ikv
ISOLATOR ROW PLUS STEP BY STEP MAINTENANCE PROCEDURES
STEP 1
Inspect Isolator Row PLUS for sediment.
A)Inspection ports(if present)
i. Remove lid from floor box frame
ii. Remove cap from inspection riser
iii. Using a flashlight and stadia rod,measure depth of sediment and record results on maintenance log.
iv. If sediment is at or above 3 inch depth,proceed to Step 2. If not,proceed to Step 3.
13)All Isolator Row PLUS
I. Remove cover from manhole at upstream end of Isolator Row PLUS
ii. Using a flashlight,inspect down Isolator Row PLUS through outlet pipe
1. Mirrors on poles or cameras may be used to avoid a confined space entry
2. Follow OSHA regulations for confined space entry if entering manhole
iii. If sediment is at or above the lower row of sidewall holes(approximately 3 inches), proceed to Step 2.
If not,proceed to Step 3.
STEP 2
Clean out Isolator Row PLUS using the JetVac process.
A)A fixed floor cleaning nozzle with rear facing nozzle spread of 45 inches or more is preferable
B)Apply multiple passes of JetVac until backflush water is clean
C)Vacuum manhole sump as required
STEP 3
Replace all caps,lids and covers,record observations and actions.
STEP 4
Inspect&clean catch basins and manholes upstream of the StormTech system.
1)B) 2 11A)
14
4
SAMPLE MAINTENANCE LOG
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3/15/11 6.3 f E KOKe New U sI:o&LaELOK. FLxeet poLKE Ls C1 frame aE DOM
grade
9/24/11 6.2 0.1 f E Some 9KE f eLE SM
6/20/13 S.Ff 0.5 f E Muckyy f mL,debrCs vEjEke LM mwhtiole whet LK NV
lsolaEor Row PLUS, matKEflKOKce due
7/7/13 6.3 f E o S Aem,jeRed o.KA vacuumed D7M
Arl
StormTeobh
Advanced Drainage Syslerns,Inc.