condition discharge

BDS Drainage Calculations For Planning and Flood Risk requirements

PROPERTY: RESIDENTIAL DEVELOPMENT MAIN STREET SHADWELL

CLIENT: JWT HOMES OUR REFERENCE: 2014-599-PL-02

REVISION STATUS DESCRIPTION RECIPIENT DATE

01 FOR PLANNING APPROVAL

FIRST ISSUE FOR JWT HOMES, THINK DESIGN AND PLANNING OFFICER.

16.05.2014

02 FOR PLANNING APPROVAL

MINOR AMMENDMENTS FOR DESIGN COORDINATION

FOR JWT HOMES, THINK DESIGN AND PLANNING OFFICER.

02.06.2014

BDS STRUCTURAL DESIGN SERVICES LTD

Calculations for JWT DEVELOPMENTS BDS structural calculation Notes

Scope of the calculations These calculations have been prepared at the request of the present owners of the above property and cover the design of the new build as a design concept.. No warranty is given by the issue of the calculations to the structural integrity of any other part of the proposed structure for which the calculations and structural advice has been given. Measurement and dimensions Dimensions and details are the purpose of the calculations has been taken from the Architects drawing. The person responsible for carrying out the works should ensure that the dimensions used in the calculations are checked onsite before ordering materials or fabrication. Any discrepancies or dimensions found to be significantly different from that assumed should be brought to the attention of BDS, so that such a discrepancy can be checked, and if necessary, the calculations amended. Building Regulations approval The owners of the property are advised that the approval of the local authority and the discharge consent from the adopting water company and utilities company should be obtained to the calculations prior to any ordering of materials or fabrication. No responsibility is accepted for any changes that may be required as a result of work having proceeded before such approvals have been obtained. Disclosure All calculations are the intelligent property of BDS and can only be sent to the intended recipients of BDS. The intended recipients are; the client, and Building control and any checking authorities for and on behalf of Building control. The administering, copying or revealing of these calculations to any other unauthorized third parties in any format whatsoever is strictly prohibited without the express permission of the Director of BDS structural design services namely James Robert Burgess BSc (Hons). Liability By checking and reading these calculations the reader accepts severable Liability of the design. BDS accepts no Liability for the installation of the design and the quality of workmanship, materials and construction operations implicated by the design. Nothing in the contract confers nor purports to confer on any third party neither any benefit nor any right to enforce any terms of this contract pursuant to the contracts (Rights to third parties) act 1999. Design references LCC PPS25 BS8305 Drainage code Building Regulations Part H URBAN DRAINAGE SPON DAVIS AND BUTLER WALLINGFORD REPORTS VOLUMES 1 AND 4 WALLINGFORD ANNUAL RAINFALL MAPS

BDS STRUCTURAL DESIGN SERVICES LTD

NOTES

• These calculation have been prepared in order to discharge the original planning conditions

16) Development shall not commence until a feasibility study into the use of infiltration drainage methods has been submitted to, and approved by the council. The analysis shall contain the results of soakaway tests and an appraisal of various infiltration drainage methods that could reasonably be employed on the site. If disposal of surface water via infiltration is not feasible, disposal to sewer may be acceptable. In order to assess the allowable discharge from the site, (ie 30% less than existing discharge), the developer shall provide details of the existing drainage layouts on the site, together with pipe sizes, gradients and connection points, as well as a plan showing the measured impermeable areas of the site. A surface water attenuation system shall be provided which ensures that the allowable discharge is not exceeded for the 1 in 100 year event including a 30% uplift for climate change. To ensure sustainable drainage and flood prevention in accordance with LCC’s Natural Resources and Waste LDF 2013 and the NPPF. 17) Development shall not commence until a scheme detailing surface water drainage works has been submitted to and approved in writing by the Local Planning Authority. The works shall be implemented in accordance with the approved scheme before the development is brought into use, or as set out in the approved phasing details. To ensure sustainable drainage and flood prevention in accordance with LCC’s Natural Resources and Waste LDF 2013 and the NPPF. 18) The site shall be developed with separate systems of drainage for foul and surface water on and off site. In the interest of satisfactory and sustainable drainage. 19) No development shall take place until details of the proposed means of disposal of foul and surface water drainage, including details of any balancing works and off -site works, have been submitted to and approved by the Local Planning Authority. To ensure that the development can be properly drained. 20) Unless otherwise approved in writing by the local planning authority, there shall be no piped discharge of surface water from the development prior to the completion of the approved surface water drainage works and no buildings shall be occupied or brought into use prior to completion of the approved foul drainage works.

• Many of the Surface attenuation calculations, brownfield and Greenfield calculations are shown in the Appendix of the Feasibility report the calculations in this document cover the proposed drainage network and components

SURFACE WATER CALCULATIONS

MANHOLE FLOOD VOLUME EXTRA VOLUME IN MANHOLES THE MANHOLES ARE DEEMED TO GIVE SOME ATTENUATION STORAGE WITH A MADD FACTOR OF 2.0 THE MANHOLES CAN FILLUP TO 50MM BELOW THE U/S OF THE MANHOLE COVER GIVING 700MM DEPTH OF WATER STORAGE.

CALCULATION OF SUBBASE THROUGH SOIL INFILTRATION

INFILTRATION RATE 5.5 RATEMM/MIN

AREA DRAINED 750 M2

CARPARK AREA 350 M2

CALCULATION OF SUBBASE THROUGH SOIL INFILTRATION

Factored infiltration rate 35

FACTOR

3

INFILTRATION RATE 106 RATEMM/MIN based on Av result 4 =80 mm /Hour

AREA DRAINED

1340 M2

PERMEABLE PAVING AREA 350 M2

Subbase

Depth

DURATION OF

RAINFALL

PORISTY

OF

SUBBASE

ratio of

Drained to

infiltration

area rainfall intensity

Infiltration

rate

H max D N R i f

mm hrs - - mm/H mm/H

116 M-100-5 0.08 0.4 3.83 0.15 0.0353333

168 M-100-10 0.17 0.4 3.83 0.11 0.0353333

200 M-100-15 0.25 0.4 3.83 0.09 0.0353333

234 M-100-30 0.5 0.4 3.83 0.06 0.0353333

300 M-100-60 1 0.4 3.83 0.04 0.0353333

247 M-100-120 2 0.4 3.83 0.02 0.0353333

174 M-100-180 3 0.4 3.83 0.02 0.0353333

108 M-100-240 4 0.4 3.83 0.01 0.0353333

163 M-100-360 6 0.4 3.83 0.01 0.0353333

ADOPT A 300 MM SUBASE BELOW THE CAR PAR PARK FOR ALL PERMEABLE PAVING UNDER 50 MM SAND BEDDING AND 65 MM THICK PERMEABLE BLOCKS WITH 5 MM GAPS BETWEEN.

PIPE

No

PIPE

LENGTH RISE

PIPE

FALL

IMPERVOUS

AREA DIAMETER VELOCITY

TIME

OF

FLOW

DISTANCE

TO START

OF PIPE

PIPE

CAPACITY

1in 100

Year

RAINFALL

INTENSITY

Qp

IMP

Qp

Total COMMENTS

M M M Ha MM M/S MINS M L/S mm/H L/s L/s STATUS

S1.001 2 0.1 17 0.0045 100 1.5 0.02 2 6.1 154.56 2.1 2.7 PIPE OK

S1.002 11.7 0.1 98 0.0045 100 0.81 0.24 13.7 6.8 154.56 2.1 2.7 PIPE OK

S1.003 11.8 0.1 148 0.009 150 0.764 0.26 25.5 14.5 154.56 4.2 5.5 PIPE OK

S1.004 7 0 149 0.0135 150 0.822 0.14 32.5 14.5 154.56 6.3 8.2 PIPE OK

S1.005 9.95 0.1 149 0.0135 150 0.843 0.20 42.45 14.5 154.56 6.3 8.2 PIPE OK

S1.006 15.8 0.1 198 0.018 225 0.768 0.34 58.25 34.3 154.56 8.4 11.0 PIPE OK

S1.007 3.8 0 190 0.018 225 0.94 0.07 62.05 34.3 154.56 8.4 11.0 PIPE OK

S1.008 2 0 200 0.0225 225 0.73 0.05 64.05 34.3 154.56 10.6 13.7 PIPE OK

SURFACE WATER DRAINAGE S.001 SURFACE WATER PIPE OK BY INSPECTION FOR 100 DIAMETER PIPE S.002 SURFACE WATER PIPE

DESIGN OF A SURFACE WATER DRAIN

Drain design details

Design flow rate; Qdesign = 2.70××××10-3

m3/s

Length of the drain; L = 11.7 m

Fall along length of drain; h = 0.1 m

Gradient of drain; i = h / L = 0.010; (1 in 98)

Minimum flow velocity; Vmin = 0.750 m/s

Minimum pipe diameter; Dmin = 100 mm

Surface roughness; ks = 0.6 mm

Mean hydraulic depth factor; m = 0.25

Kinematic viscosity of fluid; ν = 1.31××××10-6

m2/s

Using the Chezy equation

Constant; c = 56

Diameter of pipe required; D = ((Qdesign2 × 16) / (π2

× m × c2 × i × 1m/s

2))

0.2 = 68 mm

Nearest pipe diameter; Dchezy = 100 mm

Flow velocity using Chezy; Vchezy = c × √(m × Dchezy × i × 1m/s2) = 0.897 m/s

Using the Escritt equation

Diameter of pipe required; D = (Qdesign × 1000 × √(1 / i) / 0.00035 m3/s)

0.382 × 1mm = 73 mm

Nearest pipe diameter; Descritt = 100 mm

Flow velocity using Escritt; Vescritt = 26.738 × (Descritt / 1mm)0.62

×1 m/s / (√(1 / i) × 60) = 0.784 m/s

Using the Colebrook-White Equation for pipe running full and partially full

Design pipe diameter; Ddesign = max(Dchezy, Descritt, Dmin) = 100 mm

Constant; Z = √(2 × (gacc / 1m/s2) × (Ddesign /1000mm) × i) = 0.142

Flow velocity; Vfull = -2×Z×log((ks/(3.7× Ddesign))+((2.51×ν)/(Ddesign×Z×1m/s)))×1m/s

Vfull = 0.775 m/s

Flow rate running full; Qfull = Vfull × π × Ddesign2 / 4 = 6.09××××10

-3 m

3/s

PASS - Maximum flow rate is greater than design flow rate

From Hydraulics Research Tables 35 and 36

Depth as proportion of D; x = 0.466

Flow velocity at design flow rate; Vdesign = 0.751 m/s

PASS - Design velocity is greater than 0.750 m/s

L

h

S.003 SURFACE WATER PIPE




m3/s









m2/s


Constant; c = 56


× m × c2 × i × 1m/s

2))

0.2 = 98 mm





0.382 × 1mm = 104 mm



×1 m/s / (√(1 / i) × 60) = 0.820 m/s





Vfull = 0.821 m/s


-3 m

3/s






L

h





m3/s









m2/s


Constant; c = 56


× m × c2 × i × 1m/s

2))

0.2 = 116 mm





0.382 × 1mm = 121 mm



×1 m/s / (√(1 / i) × 60) = 0.816 m/s





Vfull = 0.817 m/s


-3 m

3/s






L

h





m3/s









m2/s


Constant; c = 56


× m × c2 × i × 1m/s

2))

0.2 = 116 mm





0.382 × 1mm = 121 mm



×1 m/s / (√(1 / i) × 60) = 0.817 m/s





Vfull = 0.819 m/s


-3 m

3/s






L

h





m3/s









m2/s


Constant; c = 56


× m × c2 × i × 1m/s

2))

0.2 = 138 mm





0.382 × 1mm = 143 mm



×1 m/s / (√(1 / i) × 60) = 0.911 m/s





Vfull = 0.923 m/s


-3 m

3/s






L

h





m3/s









m2/s


Constant; c = 56


× m × c2 × i × 1m/s

2))

0.2 = 184 mm





0.382 × 1mm = 189 mm



×1 m/s / (√(1 / i) × 60) = 0.905 m/s





Vfull = 0.917 m/s


-3 m

3/s






L

h

CALCULATION OF INFILTRATION TRENCHS

Factored infiltration rate 105 MM/H Factor = 1

INFILTRATION

RATE 105 MM/H

free volume agg.% 0.3

WIDTH 0.5 m

DEPTH 0.45 m

PERMEABLE PAVING AREA

130 M2

DURATION OF

RAINFALL

rainfall

intensity Volume

PROVIDED

Volume

required

status u/r

Length

DISCHARGE

TIME D i

H mm/H m3 m3 m HRS

M100-5 0.083 154.56 0.7 0.6625 trench ok 0.9814 10 5.0

M100-10 0.167 114.82 1.2 0.6686 trench ok 0.9905 18 5.1

M100-15 0.250 92.74 1.6 0.6573 trench ok 0.9738 23 5.2

M100-30 0.500 58.14 2.0 0.6490 trench ok 0.9616 29 5.2

M100-60 1.000 40.60 2.6 0.6239 trench ok 0.9243 39 5.2

M100-120 2.000 22.11 2.4 0.5984 trench ok 0.8864 36 5.2

M100-180 3.000 15.28 2.2 0.6184 trench ok 0.9161 32 5.2

M100-240 4.000 12.06 2.0 0.5539 trench ok 0.8207 30 5.2

M100-360 6.000 12.06 2.5 0.6183 trench ok 0.9160 37 5.2

FOUL WATER CALCULATIONS

F.003 FOUL WATER PIPE

DESIGN OF A FOUL SEWER

Design pipe flow limited to 0.75 times full depth

Sewer design details


m3/s

Length of the sewer; L = 12.0 m

Fall along length of sewer; h = 0.2 m

Gradient of sewer; i = h / L = 0.012; (1 in 80)






m2/s


Constant; c = 56


× m × c2 × i × 1m/s

2))

0.2 = 72 mm





0.382 × 1mm = 80 mm



×1 m/s / (√(1 / i) × 60) = 1.113 m/s





Vfull = 0.978 m/s


-3 m

3/s




PASS - Design pipe flow less than 0.75 times full depth



L

h

F1.004 FOUL WATER PIPE





m3/s









m2/s


Constant; c = 56


× m × c2 × i × 1m/s

2))

0.2 = 85 mm





0.382 × 1mm = 94 mm



×1 m/s / (√(1 / i) × 60) = 1.114 m/s





Vfull = 0.979 m/s


-3 m

3/s







L

h

F1.005 FOUL WATER PIPE –REV 02





m3/s









m2/s


Constant; c = 56


× m × c2 × i × 1m/s

2))

0.2 = 89 mm





0.382 × 1mm = 98 mm



×1 m/s / (√(1 / i) × 60) = 1.111 m/s





Vfull = 0.976 m/s


-3 m

3/s







F1.006 FOUL WATER PIPE REV 02


L

h




m3/s









m2/s


Constant; c = 56


× m × c2 × i × 1m/s

2))

0.2 = 85 mm





0.382 × 1mm = 94 mm



×1 m/s / (√(1 / i) × 60) = 1.111 m/s





Vfull = 0.976 m/s


-3 m

3/s








L

h





m3/s









m2/s


Constant; c = 56


× m × c2 × i × 1m/s

2))

0.2 = 108 mm





0.382 × 1mm = 118 mm



×1 m/s / (√(1 / i) × 60) = 1.131 m/s





Vfull = 0.994 m/s


-3 m

3/s







L

h






m3/s









m2/s


Constant; c = 56


× m × c2 × i × 1m/s

2))

0.2 = 50 mm





0.382 × 1mm = 56 mm



×1 m/s / (√(1 / i) × 60) = 1.224 m/s





Vfull = 1.052 m/s


-3 m

3/s







L

h

condition discharge

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