FLOOD RISK ASSESSMENT...FLOOD RISK ASSESSMENT for 23 VIKING WAY, WINCH WEN, SWANSEA _____ REF :...

INTRADO ROBBINS IS THE TRADING NAME OF ROBBINS CONSULTING ENGINEERS LTD.

REGISTERED IN ENGLAND AND WALES NO. 05785608

______________________________________________________________________________________________________

FLOOD RISK ASSESSMENT

for

23 VIKING WAY, WINCH WEN, SWANSEA

______________________________________________________________________________________________________

REF : IR17019-FCA1

JANUARY 2017

Prepared by :

Intrado Robbins (Cardiff Office)

Castle House, 63/69 Cardiff Road

Taffs Well, Cardiff. CF15 7RD

Tel: 02920 811097

Email : [email protected]

Status Prepared Checked Approved

Issue Rev Name Date Name Date Name Date

First - C. L. Cooke 3/2/17 A. Robbins 3/2/17 C. L. Cooke 3/2/17

Second

Third

.IR 17019 – 23 VIKING WAY, WINCH WEN, SWANSEA

CONTENTS

INTRODUCTION

1.0 DEVELOPMENT LOCATION AND DESCRIPTION

2.0 DEFINITION OF FLOOD HAZARD

3.0 EXISTING SURFACE WATER DRAINAGE REGIME

4.0 PROPOSED SURFACE WATER DRAINAGE

5.0 OFF SITE IMPACTS

6.0 RESIDUAL RISKS CONCLUSIONS

7.0 CONCLUSION

APPENDICIES

A TOPOGRAPHICAL & DRAINAGE SURVEY

B WELSH WATER RECORDS

C PROPOSED SITE LAYOUT


Introduction

Intrado Robbins has been commissioned by D P Architecture to undertake a flood risk assessment for the

construction of a new steel portal frame structures, as part of a new vehicle repair shop on behalf of RGM

Vehicle Body Repairs Ltd. The Flood Risk Assessment (FRA) has been undertaken in accordance with the

Planning Policy Wales Technical Advice Note 15: Development and Flood Risk (TAN 15) July 2004 sets out strict

tests to protect people and property from flooding.

The objectives of a site-specific flood risk assessment are to establish:

whether a proposed development is likely to be affected by current or future flooding from any source;

whether it will increase flood risk elsewhere;

whether the measures proposed to deal with these effects and risks are appropriate;

the evidence for the local planning authority to apply (if necessary) the Sequential Test, and;

whether the development will be safe and pass the Exception Test, if applicable.

The report has been prepared for RGM Vehicle Body Repairs Ltd to support their Planning Application.

http://gov.wales/docs/desh/publications/040701tan15en.pdf


1.0 Development Location and Description

The proposals consist of the construction of steel portal frame structures, as part of a new vehicle

repair shop with associated car parking and access road.

The existing site is currently undeveloped. The proposed development is located at 23 Viking Way,

Winch Wen, Swansea . The Ordnance Survey grid for the site is 268390 196680. The site is shown in

Figure 1.

Figure 1 – Site location

The proposed development will be accessed off the Viking Way which bounds the site to the North.

The eastern and western boundaries of the site are bounded by existing industrial developments. The

southern boundary of the site is undeveloped.

The topography of the site is such that it slopes from approximately 33.6m in the southeast to 44m

AOD at the northwest.

There is a ditch on the western boundary however there does not appear to be an outlet from the

ditch. The site is proposed for general industrial and is therefore classified as a ‘a less vulnerable’

development in accordance with Figure 2 of the Tan 15.

The proposed development is located in Flood Zone 1 with a low probability of flooding the proposed

development. Figure 2 shows the National Resources Wales Flood Map.

The Site


Figure 2 – National Resources Wales Flood Map

2.0 Definition of the flood Hazard

Fluvial Flooding

The closest watercourse is the Nant Bran, located approximately 700m to the west of the site. The

NRW flood maps confirm the site is at little to no risk of fluvial flooding.

Tidal Flooding

The NRW flood maps confirm the site is at little to no risk of fluvial flooding.

Groundwater Flooding

The geotechnical report by Geo Technology indicates from historical site plans and a site walkover that

some issues of water emanate from within the site, and historically a stream was shown to traverse the

site. A ditch was observed traversing NNE – SSW across the site, though no significant water was

observed in it. The extent of surface water entering the site from the site above (during periods of

heavy rainfall) is unknown. The location of the site on a shallow hillside would suggest that it is not at

risk from pluvial or alluvial flooding of any great extent.

Site sensitivity information from Envirocheck indicates that the site could be at risk from relict water

features (ditches or streams) which may now be infilled, and may well be related to the ditch observed

in the walkover

The NRW records do not identify the site as being in a Groundwater Source Protection Zone and

therefore the risk of flooding is assumed as low.


Overland Flow Flooding

Intense rainfall, often of short duration, that is unable to soak into the ground or enter drainage

systems can run quickly off land and result in local flooding.

The site is considered to be at a low risk from overland flow as recorded by NRW.

Flooding from Sewers

In urban areas, rainwater is frequently drained into surface water sewers or sewers containing both

surface and waste water known as “combined sewers”. Flooding can result when the sewer is

overwhelmed by heavy rainfall, becomes blocked or is of inadequate capacity.

There are foul and surface water sewers in Viking Way that flow away from the site. These sewers are

in the ownership of Welsh Water. Viking Way falls away from the site towards Jersey Road and

therefore failure of these sewers would not cause flooding to the site.

Flooding from Reservoirs, Canals and Other Artificial Sources

There are no artificial sources of water in the vicinity of the site, therefore no detailed assessment is

required.

3.0 Existing Surface Water drainage arrangements

The existing site is undeveloped as topographical survey has been undertaken and can be found in

Appendix A.

Sewer records have been obtained from Welsh Water to determine the existing public sewer network

in the area. Appendix B contains the plan of Welsh Water Sewer records. The records and drainage

survey indicate there are both foul and surface water public sewers in Viking Way.

As the site is undeveloped there are no current drainage systems on site. There is a ditch to the

western boundary of the site, however on investigation there are no inlets or outlets to this ditch.

4.0 Proposed Surface Water Drainage

Appendix C contains the proposed site layout plan, the site is 0.975ha. The proposed development is

for two workshops, 1400m2 and 850m2 in area together with a vehicle parking and hardstanding. The

post development impermeable area is 0.657 hectares based on the site layout by DP Architecture.

A site investigation report was carried out by Geo Technology and subsequent infiltration tests were

carried out by the client. We have been advised the

Due to the site being located in a Flood Zone 1 there are no restrictions on the layout with respect to

the flood risk.


The existing and proposed flow from the site are as follows:

It would be proposed to attenuate the to the existing 1 year flows from the site, prior to connection to

the public sewer.

Exceedance flow will follow the natural slope to the north of the site, over the open space to the north

collecting in the ditch running along the Motorway boundary.

5.0 Off Site Impacts

The proposed development is located within Flood Zone 1 and therefore will have no impact on the

flood plain. There will be no interference to any known flood paths for the 1 in 100 year flood event

(allowing for climate change) in the implementation of this development, as a result there is no impact

of flood risk to the existing local areas.

6.0 Residual Risks

There are no significant residual risks identified within the assessment. All drainage will require

periodic inspection and maintenance. The on-site drainage maintenance is to be the responsibility of

the operator.

7.0 Conclusion

This Flood Risk Assessment has been undertaken in accordance with TAN 15.

The application site is sequentially appropriate in accordance with the requirements of the Sequential

Tests, as the application site is located with Flood Zone 1 – little to no risk of fluvial or tidal flood risk.

All potential sources of flooding have been assessed and they have all been assessed as low risk.

The surface water drainage ensures that there will be no increase of surface water run off from the site

for storm return periods up to the 1 in 100 year event, allowing for the effects of climate change.

Return Period (years) Existing

Discharge rate l/s

Proposed

Discharge rate l/s

1 4.9 60.7

30 9.9 182.1

100 12.2 270.4 (inc 30% cc)


APPENDIX A

TOPOGRAPHICAL SURVEY



APPENDIX B

WELSH WATER SEWER RECORDS

1:1250

Reproduced from the Ordnance Survey 's maps w i th the

permiss ion of the Contro l ler o f Her Majes ty ' s S ta t ionary Of f i ce .

Crown Copyr ight . L i cence No: WU298565.

Scale:

EXACT LOCATION OF ALL APPARATUS TO BE DETERMINED ON

SITE

D w r C y m r u C y f y n g e d i g ( ' t h e C o m p a n y ' ) g i v e s t h i s i n f o r m a t i o n a s t o t h e p o s i t i o n o f i t s u n d e r g r o u n d a p p a r a t u s b y w a y o f g e n e r a l g u i d a n c e o n l y a n d o n t h e s t r i c t u n d e r s t a n d i n g t h a t i t i s b a s e d o n t h e b e s t i n f o r m a t i o n a v a i l a b l e a n d n o w a r r a n t y a s t o i t s c o r r e c t n e s s i s r e l i e d u p o n i n t h e e v e n t o f e x c a v a t i o n s o r o t h e r w o r k s m a d e i n t h e v i c i n i t y o f t h e C o m p a n y ' s a p p a r a t u s a n d a n y o n u s o f l o c a t i n g t h e a p p a r a t u s b e f o r e c a r r y i n g o u t a n y e x c a v a t i o n s r e s t s e n t i r e l y o n y o u . T h e i n f o r m a t i o n w h i c h i s s u p p l i e d h e r e b y b y t h e C o m p a n y , i s d o n e s o i n a c c o r d a n c e w i t h s t a t u t o r y r e q u i r e m e n t s o f s e c t i o n s 1 9 8 a n d 1 9 9 o f t h e W a t e r I n d u s t r y A c t 1 9 9 1 b a s e d u p o n t h e b e s t i n f o r m a t i o n a v a i l a b l e a n d i n p a r t i c u l a r , b u t w i t h o u t p r e j u d i c e t o t h e g e n e r a l i t y o f t h e f o r e g o i n g , i t s h o u l d b e n o t e d t h a t t h e r e c o r d s t h a t a r e a v a i l a b l e t o t h e C o m p a n y m a y n o t d i s c l o s e t h e e x i s t e n c e o f a d r a i n s e w e r o r d i s p o s a l m a i n l a i d b e f o r e 1 S e p t e m b e r 1 9 8 9 , o r i f t h e y d o , t h e p a r t i c u l a r s t h e r e o f i n c l u d i n g t h e i r p o s i t i o n u n d e r g r o u n d m a y n o t b e a c c u r a t e . I t m u s t b e u n d e r s t o o d t h a t t h e f u r n i s h i n g o f t h i s i n f o r m a t i o n i s e n t i r e l y w i t h o u t p r e j u d i c e t o t h e p r o v i s i o n o f t h e N e w R o a d s a n d S t r e e t W o r k s A c t 1 9 9 1 a n d t h e C o m p a n y ' s r i g h t t o b e c o m p e n s a t e d f o r a n y d a m a g e t o i t s a p p a r a t u s .

W h i l s t e v e r y r e a s o n a b l e e f f o r t h a s b e e n t a k e n t o c o r r e c t l y r e c o r d t h e p i p e m a t e r i a l o f D C W W a s s e t s , t h e r e i s a p o s s i b i l i t y t h a t i n s o m e c a s e s p i p e m a t e r i a l ( o t h e r t h a n A s b e s t o s C e m e n t o r P i t c h F i b r e ) m a y b e f o u n d t o b e a s b e s t o s c e m e n t ( A C ) o r P i t c h F i b r e ( P F ) . I t i s t h e r e f o r e a d v i s a b l e t h a t t h e p o s s i b l e p r e s e n c e o f A C o r P F p i p e s b e a n t i c i p a t e d a n d c o n s i d e r e d a s p a r t o f a n y r i s k a s s e s s m e n t p r i o r t o e x c a v a t i o n

11/01/2017

⇧

268369,196730



APPENDIX C

PROPOSED SITE LAYOUT

VIKING WAY

LPLP

SVSV

SV

MH

MH

MH

MH

MH

300

IL 33.97

IL 33.74 (to silt)

Blocked

UTL

UTL

UTL

Drain

G

G

G

G

BT

BT

G

G

G

1

21

El Sub Sta

Viking Court

JE

RS

EY

RO

AD

VIKING WAY

ICLPLP

SVSV

SV

MH

MH

MH

MH

MH

300

IL 33.97

IL 33.74 (to s ilt)

Blocked

UTL

UTL

UTL

Drain

Industrial EstateWinch Wen

G

G

G

G

BT

BT

G

G

G

15000sq ft1400 sq mworkshop

New Access to highway

Banked ground tosuit levels

9100sq ft850 sq mancillary workshops

Vehicle Parking

Re-instate and maintainthe existing culvert

Shrubbery and planting tothe road elevation to screenthe new structure

line of existing 600mm diatrunk water main crossingthe site

Hatching indicates theeasment area required byDwr Cymru Welsh Water

planting

planting

Vehicle Parking

15300

54614

Valeting Bay4.5m High

Barrier

Divert Culvert

New Fencewith electronic gate

New Fence

North

Contractor must check all dimensions on site.

Figured dimensions must be taken, not scaleddimensions. All discrepancies in this drawingmust be reported immediately to theContract Administrator

architectureJob

Dwg. No.Drawn By

56 Walter Road Swansea SA1 5PYtel: 01792 466554 fax: 01792 466553 mob: 0777 585 3754e-mail [email protected]

Description

Date

Scale

Job No.

Approved

pd Proposed car bodyrepair workshopViking Way, Swansea

Site and Location Plans

As Shown

Aug 2016 15 - 008

15-008/02

1 : 500

Site1

1 : 1250

Location2

A2

FLOOD RISK ASSESSMENT...FLOOD RISK ASSESSMENT for 23 VIKING WAY, WINCH WEN, SWANSEA _____ REF :...

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