HomeMy WebLinkAboutStormwater Report and Calculations 02-04-20 STORMWATER MANAGEMENT
DESIGN REPORT
FOR:
FLANDERS MILL APARTMENTS
LOT 1, BLOCK 25
FLANDERS MILL SUBDIVISION
BOZEMAN, MT
Prepared By:
MADISON
ENGINEERING
Madison Engineering
895 Technology Drive, Suite 203
Bozeman, MT 59718
(406) 586-0262
JANUARY 2020
STORMWATER MANAGEMENT
DESIGN REPORT
FOR:
FLANDERS MILL APARTMENTS
LOT I , BLOCK 25
FLANDERS MILL SUBDIVISION
BOZEMAN, MT
Madison Engineering
895 Technology Blvd Ste 203
Bozeman, MT 59718
(406) 586-0262
JANUARY 2020
FLANDERS MILL APARTMENTS MASTER SITE PLAN
LOT 1, BLOCK 25, FLANDERS MILL SUBDIVISION
STORMWATER DESIGN REPORT
This design report will give an overview of the proposed stormwater system for the Flanders
Mill Apartments Master Site Plan located in Lot 1, Block 25 of Flanders Mill Subdivision,
Bozeman, Montana.
The project site is broken into three phases of development. The water, storm and sanitary
infrastructure will be installed entirely during Phase 1 along with associated parking lot
improvements and buildings in Phase 1. Phases 2 and 3 will consist of associated parking lot
improvements and buildings in those areas. The first phase is located at the north end of the site,
which is the lowest in elevation. The stormwater collection system for the entire project consists
of two inlets that surface drain all three development phases to an underground R Tank retention
system. The two inlets and retention system are located in Phase 1. This simplifies the
stormwater design considerations for the phased development because new pavement and
buildings constructed during later phases will simply contribute to the existing system installed
during Phase 1 which has been sized for the entire three phases of development.
Two post development drainage areas were created within the project. Runoff from Drainage
Areas 1 and 2 will be contained on site in Retention Facility 1. This retention facility will be
comprised of 1,755 Single +Mini R Tank HD modules located under a portion of the parking lot
in the northwest corner of the site. The system will be equipped with an overflow manhole that
drains into an existing curb inlet in Harvest Parkway. In the event that the system is full it will-
backflow the incoming drainage pipe and fill the overflow manhole and be released into the
existing subdivision infrastructure.
The following references were used in the preparation of this report:
a. COB Design Standards and Specifications Policy, 2004. Addendum #6
b. COB Modifications to Montana Public Works Standard Specifications (MPWSS)
A. Stormwater Infrastructure Calculations
The project area was divided into drainage areas as shown on Sheet SD1.0 in Appendix A.
These drainage areas were used to determine the stormwater runoff flows, which in turn were
used to determine the required underground retention volume and storm drain pipe sizes.
Calculations are found in Appendix B. The underground system was designed to detain the
stormwater runoff from the 10-year storm event or the first 0.5 inch of rainfall over parking
impervious surfaces, whichever is greater. It was determined that the first half inch of runoff was
greater than the required detention volume, so the half inch runoff volume governed the design.
B. Storm Drain Piping
The proposed storm drains that carry runoff into the underground retention system were sized to
carry the 25-year storm event peak runoff flow. It was determined that an arch reinforced
Flanders Mill Apartments Master Site Plan Stonnwater Design Report
Page 1 of 2
concrete pipe (RCP) 22 inches wide x 13 inches tall would suffice for Drainage Area 1 and a 15-
inch diameter PVC storm drain pipe is sufficient to carry the flows from Drainage Area 2.
Calculations are found in Appendix B.
C. Area Drain grate sizing
The area drain that receives runoff from the majority of the site was checked for capacity.
Assuming a water depth above the grate of 0.6 feet, the capacity of the selected 33-inch diameter
grate is 10.4 cfs, which exceeds the 25-year storm runoff tributary to that point of 9.3 cfs. With a
depth of 0.6 feet above the grate, the water surface elevation at the adjacent curb is kept below
0.15 feet below top back of curb. See Appendix C for more information.
Appendices
A. Sheet SD1.0 (Drainage Area map)
B. Stormwater calculations
C. Area Drain grate sizing
D. Stormwater Maintenance Plan
Flanders Mill Apartments Master Site Plan Stonnwater Design Report
Page 2 of 2
Appendices
Appendix A — Sheet SD 1.0
Appendix B — Stormwater Calculations
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Flanders Mill Apartments
Lot 1 Block 25 Phase 7 Flanders Mill Sub.
Stormwater Detention/Retention Calculations
Calculation of Required Volume for Storm Detention Pond
(Reference: Bozeman Stormwater Master Plan-1982)
Design Rainfall Freq. ' , ear see page III-5 of master Ian
IDF coefficient a 0.64
IN coefficient b
IDF coefficient n 0.65
Pre-development Calculations Post-development Calculations
C C
Areas(ft): open space 397,970 0.20 Areas(ft): Landscaped 13 ,62i 020
med.res. 0.35 Impervious P33.604 090
dense res. _ 0.50 Building 100 539 0.90
Total: 397,970 Total: ,OT 70
total area: 9.14 acres total area: 9.14 acres
composite C: 0.20 composite C: 0.66
Overland 4 Overland tc
average slope: 1 25 percent average slope: 1 25 percent
travel distance: nrn feet travel distance: 900 feet
t�: 48 minutes te: 23 minutes
Total t�: 48 minutes Total tc: 23 minutes
intensity at t,(fig 23): 0.74 in/hr intensity at I.(fig 23): 1.21 in/hr
pre-devel peak runoff: 1.35 cfs post-devel peak runoff: 7.32 cfs
Storm Duration Intensity Future Runoff Runoff Release Required
_ (minutes) (in/hr) _ Rate(cfs) Volume(cf) Volume(cf)Storage c
23 1.21 7.32 9954 1834 8120
25 1.14 6.93 10253 1996 8257
27 1.08 6.59 10537 2158 8379
29 1.03 6.29 10807 2320 8488
31 0.99 6.02 11065 2482 8584
33 0.95 5.77 11313 2643 8670
35 0.91 5.55 11551 2805 8745
37 0.88 5.36 11780 2967 8813
39 0.85 5.17 12001 3129 8872
41 0.82 5.01 12215 3291 8924
43 0.80 4.85 12422 3453 8969
45 0.78 4.71 12623 3615 9008
47 0.75 4.58 12818 3777 9041
49 0.73 4.46 13007 3939 9069
51 0.71 4.34 13192 4101 9091
53 0.70 4.23 13372 4262 9110
55 0.68 4.13 13548 4424 9123
57 0.66 4.04 13719 4586 9133
59 0.65 3.95 13887 4748 9139
61 0.64 3.86 14051 4910 9141
63 0.62 3.78 14211 5072 9139
65 0.61 3.70 14368 5234 9134
required detention storage(ft)= 9,141
Detention pond.xIs
0.5"Rainfall Required Retention Calculations
Impervious Area
Pavement&Sidewalks 1G3.804 sf
Buildings 100.539 sf
Total impervious 264,343 sf
Rainfall 0.5 inches
0.042 ft
Volume to be Retained 11,014 cf
R-Tank HD Module Calculation
feet
Length 28.15 inches 2.35 feet 39 91.49
Width 15.75 inches 1.31 feet 45 59.06
Height-Single+Mini 25.98 inches 2.17 feet 5403.480469
Area
Basin Area Required 5,087.4 sf
Length 89.0 sf
Width 57.2 sf
R-Tank HD Module Reouired Actual
Length 37.9 units 39 units
Width 43.6 units 45 units
Final Volume Provided
R-Tank HD Module
Height 2.17 ft Single+Mini
Length 91.49 ft
Width 59.06 ft
Total Volume Provided 11,726 cf Exceeds both Required Detention and 0.6"rainfall Retention Volumes
0.95
11139.27499
4724.75
2.17
4726.92
Detention pond.xis
Flanders Mill Apartments,Lot 1,Block 25 Appendix B
Peak flow calculations
Curb Inlet Drainage Areas-Post Development
See-SDf.0 for vjsual rofkO6 a
Peak Flow Summary(cfs)
Drainage Area No. Area(Ac.) Weighted C 100 Yr 25 Yr 10 Yr
1 8.657 0.66 15.4 9.3 6.9
2 0.479 0.66 1.8 1.0 0.8
OF Equations from Bozeman Stormwater Master Plan for City of Bozeman,March 1982
General Equation: i=a/(b+D)"where D is duration in hours,i=intensity in inches/hour
Storm Information
Design Rainfall Freq. 100 25 10
OF coefficient a 1.01 0.78 0.64
OF coefficient b 0 0 0
IDF coefficient n 0.67 0.64 0.65
Adjustment Factor Cf. 1.25 1.1
Weighted C Value-Entire site
Landscaped 133,627 0.20
Impervious 163,804 0.90
Building 100,539 0.90
397,970
Composite C 0.66
Peak Q values
Drainage Area 1
Area 8.66 acres
Weighted C 0.66
Average slope 1.25 percent
Travel Distance 900 feet
Design Rainfall Freq. 100 25 10 years
C•Cf 0.83 0.73 0.66 (Shall not exceed 1.00)
Total t�: 14.00 19.19 22.66 minutes
intensity at tc 2.68 1.62 1.21 in/hr
peak runoff: 15.4 9.3 6.9 cfs
Drainage Area 2
Total 0.479 acres
Weighted C 0.66
Average slope 1.00 percent
Travel Distance 89 feet
Design Rainfall Freq. 100 25 10 years
C'Cf 0.83 0.73 0.66 (Shall not exceed 1.00)
Total t,: 4.74 6.50 7.67 minutes
intensity at tc 5.53 3.23 2.44 in/hr
peak runoff: 1.8 1.0 0.8 cfs
Page 1 of 1
18"PVC/concrete, Appendix B
Checked at slope 0.7%
CIRCULAR CHANNEL
T
Manning's Eqn. Q=1.486 A R'as1n
n
Dlameter,do(in)= 18 -+-Enter Value
Diameter,do(ft)= 1.6
THETA
Units= 1.486
n= 0.013
Slope,S(ft/ft) 0.007
Wetted Hydraulic ec ion nergy'
Area,A Perimeter,P Radius,R Top Width,T Hydraulic Factor,Z Q(gpd-8 =V2129
Depth.v(ft) Theta(red) (fte) (ft) (ft) (ft) Depth,D(ft). (few) Q(cfs) Q(gpm) hour day) V(ft/s) (ft)
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.0 0.0 0.0 0.0 0.00
0.08 0.90 0.03 0.68 0.05 0.66 0.06 0.01 0.0 18.9 9091.7 1.3 0.03
0.15 1.29 0.09 0.97 0.10 0.90 0.10 0.03 0,2 82.3 39527.3 2.0 0.06
0.23 1.59 0.17 1.19 0.14 1.07 0.16 0.07 0.4 191.7 92030.5 2.6 0.10
0.30 1.86 0.26 1.39 0.18 1.20 0.21 0.12 0.8 345.4 165795.9 3.1 0.16
0.38 2.09 0.35 1.67 0.22 1.30 0.27 0.18 1.2 540.3 259343.1 3.5 0.19
0.45 2.32 0.46 1.74 0.26 1.37 0.32 0.25 1.7 772.4 370760.7 3.9 0.23
0.63 2.63 0.55 1.90 0.29 1.43 0.39 0.34 2.3 1037.1 497815.3 4.2 0.27
0.60 2.74 0.66 2.05 0.32 1.47 OAS 0." 3.0 1329.2 638007.7 4.6 0.31
0.68 2.94 0.77 2.21 0.35 1.49 0.52 0.65 3.7 1642.9 788601.6 4.7 0.36
0.76 3.14 0.88 2.36 0.38 1.60 0.59 0.88 4.4 1972.2 946633.4 5.0 0.38
0.83 3.34 1.00 2.51 0.40 1 A9 0.67 0.01 6,t 2310.2 1108907.0 5.2 0.41
0.90 3.64 1.11 2.66 OA2 'I A7 0.75 0.96 69 2649.9 1271972.7 5.3 0."
0.98 3.75 1.22 2.81 OA3 1A3 0.85 1.12 6.6 2983.5 1432082.0 6.5 0.46
1.05 3.06 1.32 2.97 0." 1.37 0.96 1.30 7.4 3302.3 1585114.2 5.6 0.48
1.13 4.19 1.42 3.14 0.46 1.30 1.09 1.49 8.0 3596.7 1726427.7 6.6 OA9
1.20 4A3 1.52 3.32 0.46 1.20 1.26 1.70 8.6 3855.4 1850605.5 6.7 0.60
1.28 4.69 1.60 3.52 OAS 1.07 1.49 1.08 9.1 4064.4 1950898.6 5.7 0.60
1.35 6.00 1.68 3.76 0.46 0.90 1.86 2.29 9.a 4203.8 2017838.7 6.6 OA9
1 A3 5.38 1.73 4.04 0.43 0.66 2.65 2.82 9.4 4238.2 2034342.7 5.4 0.46
1.60 6.28 1.T7 4.71 0.30 0.00 8.8 3945 6 160906.9 6.0 0.38
10.0
9.0-
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Depth(ft)
151,PVC Appendix B
Checked at slope=0.36%
CIRCULAR CHANNEL
T
Manning's Eqn. Q=1.486 A RWSW
n
Diameter,do(In)= 15 f-Enter Value
Diameter,do(ft)= 1.25
THETA
Units= 1.468
n= 0.013
Slope,S(ft/ft) 0.0036
Wetted Hydraulic Hydraulic section =nrr9y.
Area,A Perimeter,P Radius,R Top Width,T Depth,D Factor,Z Q(gpd-8 =V-129
Depth,y(ft) Theta(rad) (ft') (ft) (ft) (ft) (ft) (h"') Q(cfs) Q(gpm) hour day) V(file) (Iry
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.0 o it 0 G 0.0 0.00
0.06 0:90 0.02 0.58 0." 0.54 0." 0:00 0.0 8.4 4009.5 0.8 0.01
0.13 1.29 0.06 0.80 0.08 0.75 0.09 0.02 0.1 36.3 17432.1 1.3 0.02
0.19 1.59 0.12 0.99 0.12 0.89 0.13 0.04 0.2 84.6 40586.7 1.6 0.04
0.25 1.85 0.17 1.16 0.15 1.00 0.17 0.07 0.3 152.3 73118.3 1.9 0.06
0.31 2.09 0.24 1.31 0.18 1.08 0.22 0.11 0.5 238.3 114373.9 2.2 0.06
0.38 2.32 0.31 1.45 0.21 1.15 0.27 0.16 0.8 340.6 163510.6 2.5 0.09
0." 2.53 0.38 1.58 0*24 1.19 0.32 0.22 1.0 457A 219543.4 2.7 0.11
0.50 2.74 0.46 1.71 0.27 1.22 0.37 0.28 1.3 586.2 281370.3 2.8 0.13
0.56 2.94 0." 1." 0.29 1.24 0.43 0.35 1.6 724.6 347784.3 3.0 0.14
0.63 3.14 0.61 1.98 0.31 1.26 0.49 0:43 1.9 869.7 417478.4 3.2 0.16
0.69 3.34 0.69 2.09 0.33 1.24 0.56 0:52 2.3 1018.8 489043.4 3.3 0.17
0.75 3.64 0.77 2.22 0.35 1.22 0.63 0.61 2.6 1168.7 560957.6 3.4 0.18
0.61 3.75 0.84 2.34 0.36 1.19 0.71 0.71 2.9 1315.8 631568.4 3.5 0.19
0.88 3.96 0.92 2.48 0.37 1.16 0.60 0.82 3.2 1456.4 699057.3 3.5 0.19
0." 4.19 0.99 2.62 0.38 1.08 0.91 0.94 3.5 1586.2 761378.5 3.6 0.20
1.00 4.43 1.06 2.77 0,38 1.00 1.05 1.08 3.8 1700.3 816142.7 3.6 0.20
1.06 4.69 1.11 2.93 0.38 0.89 1.26 1.24 4.0 1792.4 860373.3 3.6 0.20
1.13 5.00 1.16 3.12 0.37 0.75 1.55 1.45 4.1 1853.9 889894.8 3.6 0.20
1.19 9.38 1.20 3.36 0.36 0." 2.21 1.79 4.2 1889.1 897173.3 3.6 0.19
1,2S 6.26 1.23 3.93 0.31 DAo 3.9 17401 2 3.2 0.15
4.6
4.0
i
3.5 r _
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i f
3.0
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�vfrthl 100,1000,
i
-E(ro 12.0
1.5 Oe
1.0 �
i
0.5
0.0
000 026 0.40 0.60 0.80 1.00 1.20 1.40
Depth(it)
1/27/2020 concrete_pipe_sizes I SD&W
ARCH PIPES:
Pipe Size (in.) Round Equiv. Metric Equivalent (mm) Area(1'tQ)lI
Weight (lbs/ft) NVall Thickness (in.)
18x11 7F 15 460x280 1.1 188 3
22x 13 71 18 560x245 1.6 233 3 1/8
29x18 24 725x460 2.9 325 3'/z
36x23 30 920x570 4.4 392 3`/z
44x27 36 1110x675 6.5 537 4
51x31 42 1300095 8.7 696 4'/z
58x36 48 1485x915 11.4 885 5
65x40 54 1650x 1015 14.3 1,079 5`/z
73x45 60 1855x1145 17.7 1,333 6
88x54 72 2235xl370 25.6 1,856 7
www.sd-w.com/channel—flow/conerete_pipe—sizes/ 1/1
Appendix C — Area Drain Grate Sizing
■ Note:When specifying/ordering grates,refer to"Choosing the Proper Inlet Grate"on pages 125-126.
For a complete listing of FREE OPEN AREAS and WEIR PERIMETERS of all NEENAH grates,refer to pages 327-332.
R-4370 Series
Round Drainage Grate
Heavy Duty
A
WEIR
SO. PERIMETER m
CATALOG GRATE FT. LINEAL
NUMBER TYPE OPEN FEET
R-4370-1 c 0.1 1.7
R437o-2 G 0.2 2.5
R-4370-3 E 04 3.9
R-4370-4 G 0.6 3.9 a EA
R-4370-5 G e0 4.7
R-43766 G 0.6 5.1
R-4370-7 G fig sz Illustrating R-4370-72
R-437M E 1.9 5.5
R-4370-9 c 1.3 5.8
R-4370-10 A 1.1 59
R-4370-12 F 0.9 58
R-4370-13 G 1.3 5.8
R-4370-15 D 1.0 5.9
R-4370-17 D 1.0 6.0
R-4370-18 E 1.3 6D
R-4370-21 D 0.9 6D
R-4370-22 D 1 D 6
R-4370-23 H 0.9 6.3
fl-4370-25 G 1.-9 9 7.6
R-4370.26 G 2-8 BS
R-4310-27A G 2.4 99
Most grates listed can be furnished with cast iron angle frame when specified. - y��
Frame is of 1/2"metal.
Dimensions in inches
Catalog No. A a G H Type
R4370-1 63/8 1 1/4 1 x 1 1/2 C
R-4370-2 91/2 21/2 i 1/2 x 31/2 5/6 G
R-4370-3 15 1 1/4 1 x 121/4 1 E
R-4370-4 15 1 1/4 3/4 x 21/4 3/4 G
R-4370-5 18 1 1/2 1 x 41/2 1 1/4 G
R-4370-6" 19 112 1 1/2 3/4 x 51/4 3/4 G
R-4370-7 20 1 3/8 2 x 2 1 G TYr F wm
R-4370-8 21 1 114 3/4 x 19 1/2 3/4 E ai1�r�
R-4370-9 22 1 112 1 1/8 1 C dgmh
R-4370-10 22 1 1/2 1 1/4 1 §A
R-4370-12 22 1 1/2 1 3/8 x 5 1 F Type H
R-4370-13 22 1 1/2 2 x 6 1 1/4 G
R-4370-15 22 1/2 1 3/4 1 1/8_ 1 D
R-4370-17 22 3/4 1 3/4 1 1/2 1 D
R-4370-18 223/4 13/4 11/2 7/8 E
R-4370-21 23 1 1/2 1 1/4 1 D
R-4370-22 23 1 3/4 1 1 1/8 D
R-4370-23 24 1 1/2 2 1/4 x 21/4 1 112 H
R-4370-25 29 3 314 1 G
R-4370-26 33 2 1 1/2 1 G
R-4370-27A 38 1 1/2 1 1 G
Light Duty.
•'Frame not available.
§Alternate Type G or Type C grates available.
Alternate Type G grate available.
I NEENAH FOUNDRY
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Appendix D — Stormwater Maintenance
Plan
STORMWATER MAINTENANCE PLAN
Flanders Mill Apartments
Owner's responsibility for routine inspection and maintenance
1. Keep the inlets of the facilities free of leaves, rocks, and other debris.
2. Re-sod damaged or maintained areas immediately, or use grass plugs from the
adjacent up-slope area.
3 See that litter and other debris are removed Cl-om inlets, swales, and vegetated and
paved areas.
4. Maintenance of the underground systems are as follows;
• Minimum required maintenance includes a quarterly inspection during the
first year of operation and a yearly inspection thereafter, Utilize inspection
ports for inspections.
• The inspection ports can be used to pump water into the system and re-
suspend accumulated sediment so that is may be pumped out. Flush and
pump as inspections deem necessary.
• Utilize the adjacent upstream storm sewer manhole for removal (vacuuming)
of debris from the end of the storm drain at the connectirnl point with the
underground chamber.
5. Owner to maintain and fund Operation and Maintenance of stormwater facilities.
Jesse Chase, Owner
WMADISON ENGINEERING\PROJECTS\2017\17-128 Flanders Mill\Storm\STORMWATER MAINTENANCE PLAN.doc
i TECHNICALER MANAGEMENT
STORMW
RJANK OPERATION, INSPECTION
& MAINTENANCE
Operation
Your ACF R-Tank System has been designed to function in conjunction with the engineered drainage system on your
site, the existing municipal infrastructure,and/or the existing soils and geography of the receiving watershed. Unless
your site included certain unique and rare features, the operation of your R-Tank System will be driven by naturally
occurring systems and will function autonomously.However,upholding a proper schedule of Inspection&Maintenance
is critical to ensuring continued functionality and optimum performance of the system.
Inspection
Both the R-Tank and all stormwater pre-treatment features incorporated into your site must be inspected regularly.
Inspection frequency for your system must be determined based on the contributing drainage area,but should never
exceed one year between inspections(six months during the first year of operation).
Inspections may be required more frequently for pre-treatment systems. You should refer to the manufacturer
requirements for the proper inspection schedule.
With the right equipmentyour inspection and measurements can be accomplished from the surface without physically
entering any confined spaces.If your inspection does require confined space entry,you MUST follow all local/regional
requirements as well as OSHA standards.
R-Tank Systems may incorporate Inspection Ports, Maintenance Ports, and/or adjoining manholes. Each of these
features are easily accessed by removing the lid at the surface. With the cover removed, a visual inspection can be
performed to identify sediment deposits within the structure.Using a flashlight,ALL access points should be examined
to complete a thorough inspection.
Inspection Ports
Usually located centrally in the R-Tank System,these perforated columns are designed to give the user a base-line
sediment depth across the system floor.
Maintenance Ports
Usually located near the inlet and outlet connections,you'll likely find deeper deposits of heavier sediments when
compared to the Inspection Ports.
Manholes
Most systems will include at least two manholes-one at the inlet and another at the outlet. There may be more than
one location where stormwater enters the system,which would result in additional manholes to inspect.
Bear in mind that these manholes often include a sump below the invert of the pipe connecting to the R-Tank.
These sumps are designed to capture sediment before it reaches the R-Tank,and they should be kept clean to
ensure they function properly. However,existence of sediment in the sump does NOT necessarily mean sediment
has accumulated in the R-Tank.
After inspecting the bottom of the structure, use a mirror on a pole(or some other device)to check for sediment
or debris in the pipe connecting to the R-Tank.
For wore informationabOLAproducts, 800.448.3636
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If sediment or debris is observed in any of these structures,you should determine the depth of the
material.This is typically accomplished with a stadia rod, but you should determine the best way to
obtain the measurement.
All observations and measurements should be recorded on an Inspection Log kept on file. We've
included a form you can use at the end of this guideline.
Maintenance
The R-Tank System should be back-flushed once sediment accumulation has reached 6"or 15%of the
total system height. Use the chart below as a guideline to determine the point at which maintenance
is required on your system.
771liple
17" 3"34" 5"50" 6"
Quad 67" 69'
Pent 84" 69'
Before any maintenance is performed on your system, he sure to plug the outlet pipe to prevent
contamination of the adjacent systems.
To back-flush the R-Tank,water is pumped into the system through the Maintenance Ports as rapidly
as possible.Water should be pumped into ALL Maintenance Ports.The turbulent action of the water
moving through the R-Tank will suspend sediments which may then be pumped out.
If your system includes an Outlet Structure, this will be the ideal location to pump contaminated
water out of the system. However, removal of back-flush water may be accomplished through the
Maintenance Ports, as well.
For systems with large footprints that would require extensive volumes of water to properly flush
the system, you should consider performing your maintenance within 24 hours of a rain event.
Stormwater entering the system will aid in the suspension of sediments and reduce the volume of
water required to properly flush the system.
Once removed, sediment-laden water may be captured for disposal or pumped through a DirtbagTm
(if permitted by the locality).
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ENVIRONMENTAL
Step-By-Step Inspection&Maintenance Routine
1) Inspection
a. Inspection Port
i. Remove Cap
ii. Use flashlight to detect sediment deposits
iii. If present, measure sediment depth with stadia rod
iv. Record results on Maintenance Log
v. Replace Cap
b. Maintenance Port/s
i. Remove Cap
ii.Use flashlight to detect sediment deposits
iii. If present, measure sediment depth with stadia rod
iv. Record results on Maintenance Log
v. Replace Cap
vi. Repeat for ALL Maintenance Ports
c. Adjacent Manholes
i. Remove Cover
H. Use flashlight to detect sediment deposits
iii. If present, measure sediment depth with stadia rod, accounting for depth
of sump (if present)
iv. Inspect pipes connecting to R-Tank
v. Record results on Maintenance Log
vi. Replace Cover
vii. Repeat for ALL Manholes that connect to the R-Tank
2) Maintenance
a. Plug system outlet to prevent discharge of back-flush water
b. Determine best location to pump out back-flush water
c. Remove Cap from Maintenance Port
d. Pump water as rapidly as possible(without over-topping port) into system until at least
l„
of water covers system bottom
e. Replace Cap
f. Repeat at ALL Maintenance Ports
g. Pump out back-flush water to complete back-flushing
h. Vacuum all adjacent structures and any other structures or st&mwater pre-treatment
systems that require attention
i. Sediment-laden water may be captured for disposal or pumped through a DirtbagT"^
j. Replace any remaining Caps or Covers
k. Record the back-flushing event in your Maintenance Log with any relevant specifics
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