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w10278-170518-FCA and Drainage Strategy
Llys Marl, Llandudno Junction
Flood Consequences Assessment & Drainage Strategy
May 2017
Llys Marl, Llandudno Junction FCA & Drainage Strategy
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DOCUMENT VERIFICATION RECORD
CLIENT: Beech Developments (NW) Ltd
SCHEME: Proposed residential development at Llys Marl, Llandudno Junction – Flood Consequences Assessment and Drainage Strategy.
INSTRUCTION: The instruction to carry out this Flood Consequences Assessment and Drainage Strategy was received from Mr John Gardiner of Beech Developments (NW) Ltd
DOCUMENT REVIEW & APPROVAL
AUTHOR: Sally Pettit
CHECKER: Jordan Jones BSc (Hons) MCIWEM
APPROVER: Aled Williams BSc (Hons) MCIWEM
ISSUE HISTORY
ISSUE DATE COMMENTS
18/05/2017 First issue
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Contents
Introduction .......................................................................................................................................... 1
Existing Conditions ................................................................................................................................ 1
Development Proposals ........................................................................................................................ 3
Flood Zone Category and Policy Context .............................................................................................. 3
Consultation .......................................................................................................................................... 6
Sources of Flooding and Probability ..................................................................................................... 7
Surface Water Management ............................................................................................................... 10
Water Quality ...................................................................................................................................... 13
Maintenance ....................................................................................................................................... 14
Foul Drainage ...................................................................................................................................... 15
Conclusions ......................................................................................................................................... 17
Recommendations .............................................................................................................................. 17
Appendices
Appendix A – Location Plan & Aerial Image
Appendix B – Topographical Survey
Appendix C – Drainage Survey, Sewer Plan, & DCWW Correspondence
Appendix D – Proposed Layout Plan
Appendix E – Flood Maps & NRW Correspondence
Appendix F – MicroDrainage Runoff and Volume Estimates
Appendix G – Maintenance Schedules
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Introduction
Waterco Consultants have been instructed to prepare a Flood Consequences Assessment (FCA) and
Drainage Strategy in respect of a proposed residential development at Llys Marl, Marl Lane,
Llandudno Junction, LL31 9HB.
The purpose of this report is to outline the potential flood risk to the site, the impact of the
proposed development on flood risk elsewhere, and the proposed measures which could be
incorporated to mitigate the identified flood risk. This report has been prepared in accordance with
the guidance contained in Planning Policy Wales (PPW) and Technical Advice Note 15 (TAN15):
Development and Flood Risk.
This report has been prepared in consultation with Natural Resources Wales (NRW) and Dŵr Cymru
Welsh Water (DCWW).
Existing Conditions
The site is located north of Llandudno Junction at National Grid reference: 279591E 378984N. The
site currently comprises undeveloped agricultural land and covers an area of approximately
1.91hectares. A location plan and an aerial image are included in Appendix A.
The site is bordered by agricultural land to the north, a small wooded strip with the A470 (road)
beyond to the east, Marl Lane and residential properties to the south and residential properties
(Woodlands housing estate) to the west. Access is provided from Marl Lane to the south.
Local Topography
A Topographical Survey has been undertaken by Angle Surveys Ltd in October 2016 and is included
in Appendix B. The Topographical Survey shows that the site generally slopes from north-west to
south-east. Site levels fall sharply towards the A470 east of the site. A topographical high point of
23.71metres Above Ordnance Datum (m AOD) is identified in the north-western corner of the site. A
topographical low point of 10.06m AOD is identified along the eastern boundary.
Ground Conditions
The British Geological Survey (BGS) online mapping (1:50,000 scale) indicates that the site is
underlain by superficial deposits of Devensian Till, generally comprising Diamicton. The superficial
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deposits are identified as being underlain by the Nantglyn Flags Formation comprising mudstone and
siltstone.
A Site Investigation (SI) was undertaken by Evans Wolfenden Partnership Ltd in March 2017 (project
reference EWP 6169). The fieldwork involved 17 machine excavated trial pits with depths varying
down to a maximum of 2.8m below ground level (bgl). The underlying strata comprised of stiff silty
clay from 0.3m bgl to 0.7m bgl with firm compact grey / green / brown clay below 0.7m bgl.
Groundwater seepage was encountered within the trial pits at the interface between the stiff silty
clay and the firm compact clay.
Soakaway tests were undertaken and given the impermeable nature of the strata, water levels did
not reduce.
Local Drainage
The DCWW sewer plan (Appendix C) shows that there are no public sewers crossing the site. The
sewer plan identifies a 225mm public combined sewer flowing east within Marl Lane. There is also a
300mm public surface water sewer and a 150mm private (subject to Section 104 adoption
agreement) surface water sewer in Marl Lane flowing east. The surface water sewers discharge to
the Afon Wydden approximately 55m east of the site. The Woodlands housing estate east of the site
is served by a separate foul and surface water drainage system. Surface water flows are discharged
to the 300mm public surface water sewer in Marl Lane. Foul flows are discharged to the 225mm
public combined sewer in Marl Lane.
The sewer plans also identify a 225mm public combined sewer flowing south adjacent to the A470
east of the site.
A drainage survey of the public sewer system south of the site has been undertaken by Invek Surveys
in March 2017 (see Appendix C). Invek Surveys also surveyed the connectivity of the highway
drainage system within Marl Lane adjacent to, and west of the site.
As shown by the Invek Survey, public surface water sewer manhole SH79786850 located
immediately south of the site has a cover level of 13.63m AOD and an invert level of 12.49m AOD.
There are no manholes associated with the 225mm public combined sewer in Marl Lane
immediately south of the site. However, a lamp-hole (SH79785805) on the public combined sewer in
Marl Lane south of the site has a cover level of 12.1m AOD an invert level of 9.66m AOD.
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A survey of the highway gullies along Marl Lane shows that highway gullies immediately south of the
site are drained to the 150mm private surface water sewer. All highway gullies upstream of the
Junction of Marl Lane and Victoria Drive (180m west of the site) up to the Junction of Marl Lane and
Pentywyn Road (580m west of the site) are drained to the public combined sewer in Marl Lane.
Development Proposals
The proposed development is for 52 dwellings with associated driveways, gardens, access roads and
public open space. The proposed development will introduce hardstanding in the form of buildings
and roads. Hardstanding will comprise approximately 7,750m2 or 40.6% of the total site area. The
remaining permeable areas will occupy 11,350m2 or 59.4% of the total site area. A proposed
development plan is included in Appendix D.
Flood Zone Category and Policy Context
Flood Zone Category
The Welsh Government Development Advice Map included in Appendix E shows that the
developable area of the site is located within Flood Zone A - an area considered to be at little or no
risk of fluvial or tidal flooding, with a less than 0.1% (1 in 1000) annual probability of flooding. The
eastern boundary of the site lies within Flood Zone C1 - an area at flood risk with a greater than 0.1%
annual probability of flooding, however is served by significant infrastructure including flood
defences.
The Natural Resources Wales (NRW) ‘Flood Map for Planning’ included in Appendix E, shows that the
developable area of the site is located outside of the extreme flood extent (Flood Zone 1), meaning it
has a less than 0.1% annual probability of flooding from rivers or the sea. The eastern boundary lies
within the defended Flood Zone 2 - an area considered to be at risk of fluvial flooding with between
a 1% (1 in 100) and 0.1% annual probability, however benefits from the protection offered by flood
defences.
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Development Vulnerability Classification
The proposed residential development is considered to be ‘highly vulnerable’ development in
accordance with Figure 2 of the Welsh Government’s Technical Advice Note 15 – Development and
Flood Risk (TAN15).
TAN15 states that highly vulnerable development is appropriate within Flood Zone A. No residential
dwellings, roads or gardens are proposed within the Flood Zone C1 extent.
Local Policy
The Conwy County Borough Council Local Development Plan 2007 – 2022 was adopted in October
2013 and is the current development plan for the County. The Local Development Plan contains the
following policies relating to flood risk and drainage:
Policy DP/3 – PROMOTING DESIGN QUALITY AND REDUCING CRIME
1. All new development will be of high quality, sustainable design which provides usable,
safe, durable and adaptable places, and protects local character and distinctiveness of the
Plan Area’s built historic and natural environment. The Council will require development
to:
….f) Provide sustainable urban drainage systems to limit waste water and water pollution and reduce
flood risk in line with national guidance and Policy NTE/8 – ‘Sustainable Drainage Systems’
POLICY NTE/6 – ENERGY EFFICIENCY AND RENEWABLE TECHNOLOGIES IN NEW DEVELOPMENT
The efficient use and conservation of natural resources are essential to the overall quality of life
within the Plan Area and to support wider social and economic sustainability objectives. The Council
will:
….c) Ensure that all new developments incorporate the principles of sustainable design such as:
….rain water harvesting, energy efficiency, sustainable drainage….
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POLICY NTE/8 – SUSTAINABLE DRAINAGE SYSTEMS
1. The use of Sustainable Drainage Systems will be required wherever reasonably practicable
with preference for on site disposal and where satisfactory arrangements can be put in
place for the long term maintenance of those systems. Where this is not proposed a
developer will need to justify that discharge is necessary and is adequately controlled.
2. Subsequent preference for surface water drainage will be for:
a) Drainage to a surface water (river, lake etc.) subject to appropriate treatment and
attenuation;
b) Drainage to surface water sewer;
c) Drainage to combined sewer.
3. The developer must demonstrate that higher preference drainage options are unfeasible
before proposing less sustainable options.
POLICY NTE/9 – FOUL DRAINAGE
1. Foul drainage to an adopted sewer should be provided wherever possible, in compliance
with Welsh Ministers Build Standards which are effective from October 2012. The
development of sites where drainage to a public sewer is not feasible will only be permitted if
proposed alternative facilities are considered adequate and would not pose an unacceptable
risk to the quality or quantity of ground or surface water or pollution of local watercourses or
sites of biodiversity importance.
2. Development proposals which include vehicle parking and other hard surface areas used by
vehicles must include measures such as trapped gullies and petrol / oil interceptors or other
suitable methods of pollution control to safeguard against pollution of the water
environment.
POLICY NTE/10 – WATER CONSERVATION
All development should incorporate water conservation measures where practicable and conform to
BREEAM standards promoting water conservation, efficiency measures and utilize SUDS techniques.
Development proposals greater than 1000m2 or 10 dwellings should be accompanied by a Water
Conservation Strategy.
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Consultation
A developer enquiry was submitted to DCWW by the developer prior to commencement of this
Drainage Strategy. The DCWW developer enquiry highlighted that the proposed development has
potential to overload the public foul / combined sewer system. As such, a Hydraulic Modelling
Assessment of the sewer system was undertaken by DCWW in August 2015 to establish the impact
of development foul flows on the public foul / combined sewer system and to identify any solutions
to resolve any potential detriment caused by the development.
The DCWW Hydraulic Modelling Assessment identifies two potential solutions to mitigate
development foul flows:
Solution 1: Construction of online storage in two locations within the sewer network
(upsizing of x2 manholes on the 225m public combined sewer adjacent to, and within the
A470 east of the site; and upsizing of storage at the Marl Drive Sewage Pumping Station
(SPS);
Solution 2: The removal of 0.084ha (840m²) of impermeable drainage area from the
combined sewer system upstream of Marl Drive SPS / Combined Sewer Overflow (CSO).
Following completion of the DCWW Hydraulic Modelling Assessment, further consultation was
undertaken with DCWW regarding an alternative surface water removal scheme. The alternative
surface water removal scheme, local to the site, is to remove connectivity of highway gullies within
Marl Lane from the public combined sewer. New connections from highway gullies within Marl Lane
will be made to the public surface water sewer (which discharges to watercourse). A new length of
surface water sewer within Marl Lane will be required.
Correspondence with DCWW dated 9th May 2017 (Appendix C) states that:
‘Your e-mail confirms a solution can be achieved, based on the principle of the surface water removal
scheme, and provided that surface water from a contributing drainage area of 0.084ha is removed,
the principle of connecting foul flows into the public combined sewer system would be considered
acceptable. Accordingly, in respect of any forthcoming planning application, it is recommended that
an accompanying proposed drainage strategy is formulated to address the proposed surface water
removal scheme including your calculations which equate to an area of 0.084ha and evidence from
your recent CCTV survey that confirms the connectivity of highway gullies’
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Further correspondence from DCWW dated 4th May 2017 (Appendix C) in relation to surface water
discharge from the proposed development states:
‘having had an opportunity to review our exchange of e-mails below and your accompanying Ground
Investigation Report (attached), namely Section 7.7 and Appendix C regarding soakaway tests, I am
satisfied that you’ve investigated and exhausted alternative drainage options under Part H of
Building Regulations and would therefore accept discharge into the public surface water sewer at an
attenuated rate. Accordingly, in respect of any future planning application submission, please accept
this e-mail as an agreement in principle to allow for communication of surface water into the said
public sewer through an attenuation device that discharges at a rate not exceeding 5 l/s.’
Pre-application advice was sought from NRW with a response included in Appendix E. NRW state
that:
‘As you may be aware the area suffered from a significant flood event in June 1993. Following the
event our predecessors carried out a flood alleviation scheme for the main river (Afon Wydden) in
Llandudno Junction. Although the scheme at the time was designed to provide a certain standard of
protection it is highly likely that the standard today would have been reduced.
We would expect Welsh Water to demonstrate that any new direct outfalls to the watercourse will
not increase flood risk from the river Wydden for a range of annual exceedance probability events.
We are at an early stage of developing a hydraulic model for the Wydden which will include various
input points; unfortunately we cannot provide a date as to when the model would be available’.
Sources of Flooding and Probability
Fluvial
The nearest watercourse is the Afon Wydden which is located approximately 50m east of the site
and beyond the A470. Afon Wydden flows south in this location. There is an unnamed tributary of
the Afon Wydden located approximately 180m north of the site. This watercourse flows east in this
location and discharges into the Afon Wydden approximately 185m north-east of the site. There are
no other watercourses in the immediate vicinity of the site.
As stated by NRW, the area (Llandudno Junction) suffered from a significant flood event in June
1993. However, there are no records of flooding affecting the site.
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A review of topographic levels shows that the Afon Wydden is situated at approximately 10m AOD.
The Flood Zone C1 extent reaches a level between 10m AOD and 12m AOD. The developable area of
the site is situated outside of the Flood Zone C1 extent (0.1% annual probability extent) and at a
minimum level of approximately 14m AOD. Any potential flooding from the Afon Wydden will
therefore not affect the site.
Site levels slope steeply at the eastern boundary. To form a development platform, an element of
ground levelling will be undertaken. To facilitate this, a retaining wall will be established near the
eastern boundary of the site. The proposed wall will be located outside of the Flood Zone C1 extent
and will not result in a loss of floodplain storage.
It can therefore be concluded that the developable area of the site is at very low risk of fluvial
flooding.
Tidal
The developable area of the site will be situated at a minimum of 14m AOD and is significantly above
sea level. Therefore the site is not at risk of tidal flooding.
Surface Water
Surface water flooding occurs when rainwater does not drain away through the normal drainage
system or soak into the ground. It is usually associated with high intensity rainfall events, but can
also occur with lower intensity rainfall or melting snow where the ground is saturated, frozen or
developed, resulting in overland flow and ponding in depressions in topography. Surface water
flooding can occur anywhere without warning. However, flow paths can be determined by
consideration of contours and relative levels.
The NRW ‘Flood Map for Surface Water’ map (Appendix E) shows that the developable area of the
site is at very low risk of surface water flooding, meaning it has a less than 0.1% annual probability of
flooding. Low land immediately east of the site is shown at high risk of surface water flooding,
meaning it has a greater than 3.3% annual probability of flooding.
Any potential surface water flooding arising at or near to the site would be directed south-east,
away from the site, following the local topography.
It can be concluded that the risk of surface water flooding is low.
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Sewer Flooding
Flooding from sewers can occur when a sewer is overwhelmed by heavy rainfall, becomes blocked, is
damaged, or is of inadequate capacity. Flooding is mostly applicable to combined and surface water
sewers.
There are no records of sewer flooding at or in the immediate vicinity of the site. However it is
acknowledged by DCWW that the downstream sewer network has capacity issues.
Any potential flooding arising from the sewers in Marl Lane to the south of the site would be
directed south-east, away from the site, following the local topography. As shown on the
Topographical Survey (Appendix B), site levels rise steeply above adjacent road levels. As such, any
potential sewer flooding would not reach the site.
It can be concluded that the risk of sewer flooding is low.
Groundwater Flooding
Groundwater flooding occurs when water levels underneath the ground rise above normal levels.
Prolonged heavy rainfall soaks into the ground and can cause the ground to become saturated. This
results in rising groundwater levels which leads to flooding above ground.
The PFRA contains no records of groundwater flooding at the site. Based on the elevations of the site
above any local watercourse, it can be concluded that the risk of groundwater flooding is low. This is
confirmed by the Site Investigation (Evans Wolfenden Partnership Ltd, March 2017) which did not
encounter any significant groundwater issues within the trial pits.
Artificial Sources of Flooding
There are no canals in the immediate vicinity of the site.
The NRW Reservoirs Flood Map (Appendix E) shows that the site is not at risk of flooding from
reservoirs. Land immediately east of the site is shown at risk of flooding associated with a failure of
the Afon Wydden flood alleviation scheme. The flood risk is derived from failure of a flood storage
area along the Afon Wydden approximately 50m east of the site. The Afon Wydden flood storage
area is maintained by NRW who are responsible for its maintenance.
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Summary of Potential Flooding
It can be concluded that the risk of flooding to the developable area of the site is very low. No flood
mitigation measures are considered necessary for the development. However, in accordance with
Building Regulations, finished floor levels should be set 150mm above surrounding ground levels.
Surface Water Management
The site is undeveloped and considered to be greenfield. The site is not currently served by a formal
drainage system.
In accordance with TAN15, new development should not create additional runoff when compared
with the undeveloped situation.
In order to ensure no increase in surface water runoff as a result of the development, the runoff rate
will be controlled and sustainable drainage systems used to accommodate the 1 in 100 year plus
30% Climate Change (CC) storm event.
Greenfield runoff rates have been estimated using the FEH (Flood Estimation Handbook) method
within MicroDrainage and are included within Appendix F. The existing QBAR (equivalent to the 1 in
2 year event) runoff rate is 3.9 l/s. It should be noted that the FEH data indicates a low soil
percentage runoff value for the sub-catchment which in turn results in a low runoff rate. Given the
underlying clay found during the Site Investigation, it is likely that the site specific soil percentage
runoff value would be higher.
DCWW have confirmed in correspondence (Appendix C) that they would accept a discharge rate of 5
l/s to the public surface water sewer system.
Attenuation Storage
In order to achieve a discharge rate of 5 l/s, attenuation storage will be required. A storage estimate
is included in Appendix F. An estimated storage volume of 468m³ will be required to accommodate
the 1 in 100 year plus 30% Climate Change (CC) event. An estimated storage volume of 223m³ will be
required to accommodate the 1 in 30 year event. The storage estimates are based on storage within
a tank or pond structure, an impermeable drainage area of 0.775ha, a design head of 1m and
hydro-brake flow control.
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The storage estimates are provided for indicative purposes and should be verified at the detailed
design stage.
Discharge Method
In accordance with Part H of the Building Regulations, the following hierarchy of surface water
disposal methods should be applied: infiltration (soakaways); watercourse; sewer.
Infiltration
The first consideration for the disposal of surface water is infiltration (soakaways and permeable
surfaces). As stated in the preceding sections, the underlying strata comprises of stiff silty clay from
0.3m bgl to 0.7m bgl with firm compact grey / green / brown clay below 0.7m bgl. Soakaway tests
were undertaken and given the impermeable nature of the strata, water levels did not reduce.
It can therefore be concluded that infiltration techniques (soakaways) will not be a feasible option.
Watercourse
The next consideration for surface water discharge is to watercourse. The nearest watercourse is
the Afon Wydden which is located 50m east of the site and beyond the A470.
A direct connection to Afon Wydden would require crossing third party land and laying a new pipe
beneath Marl Lane and the A470. To avoid forming a new outfall to the Afon Wydden and causing
significant disruption on the A470, a connection to Afon Wydden should be made via the existing
300mm public surface water sewer located within Marl Lane south of the site.
Sewer
As discussed above, a connection to watercourse via the 300mm public surface water sewer in Marl
Lane appears a feasible option. A connection to this sewer at a rate of 5 l/s has been agreed in
principle with DCWW.
Public surface water manhole SH79786850 located immediately south of the site has a cover level of
13.63m AOD and an invert level of 12.49m AOD. The minimum proposed site level is approximately
14m AOD. As such, a gravity connection can be achieved subject to utilising a shallow feature for
attenuation storage.
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Sustainable Drainage Systems
Attenuation storage should be provided in the form of Sustainable Drainage Systems (SuDS) where
practical. The following SuDS options have been considered:
Soakaways
As described above, soakaways are not feasible due to the impermeable strata. This has been
confirmed through infiltration testing.
Swales, detention basins and ponds
The development plans do not include provision for an above ground attenuation feature such as a
pond or basin. However, there is potential to utilise a pond or basin as an above ground attenuation
feature. A pond or basin could be located within the area of public open space in the topographically
lower south-eastern extent of the site.
However, an above open surface water attenuation feature such as a pond or basin presents a
significant safety risk; the hazards and appropriate mitigation should be considered at the detailed
design stage. Safety risks are particularly prudent in this instance given that a children’s play area is
proposed within the area of public open space.
Rainwater Harvesting
The attenuation benefits provided through the use of rainwater harvesting are considered to be
limited, and would only be realised when the tanks were not full. However, rainwater harvesting
techniques could be incorporated within the final design.
Green Roofs
Green roofs are not identified on the development plans. Given the nature of the proposed
development, the significant additional cost involved in installing and maintaining green roofs and
the additional works required to allow for the additional loading on the buildings, green roofs are
not considered a practical option. The benefits achieved through installing a green roof would be
disproportionate to the significant ongoing maintenance and construction costs involved.
Porous / Permeable Paving
Permeable paving could be incorporated within private roads and driveways. Private roads and
driveways occupy approximately 4,250m². Storage would be provided within a lined sub-grade
material prior to controlled release to the receiving sewer. The provision of storage within the sub-
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grade material would only be feasible in areas with a proposed gradient of <1 in 20 as detailed
within CIRIA RP992/28 (Design Assessment Checklists for Permeable/Porous Pavement). Site
gradients should be confirmed at the detailed design stage. The amount of storage provided within
permeable paving is subject to sub-grade depth and gradient. The use of permeable paving will be
considered at the detailed design stage.
Underground Attenuation Tanks
Storage could be provided within an underground attenuation tank or within oversized pipes.
Sufficient space for an underground tank is provided beneath the area of public open space in the
lower south-eastern extent of the site. Oversized pipes could be located beneath the access roads.
Concept Surface Water Drainage Scheme
Surface water will be discharged to the 300mm public surface water sewer located south of the site
within Marl Lane at a rate of 5 l/s. The connection has been agreed in principle by DCWW. Surface
water run off up to the 1 in 100 year plus 30% CC event will be attenuated on site through provision
of an attenuation tank (modular storage) located within the area of public open space. Oversized
pipes could also be provided beneath the access road.
The proposed surface water drainage scheme will ensure no increase in runoff over the lifetime of
the development. The proposed development will therefore not increase flood risk elsewhere.
Exceedance Event
The proposed drainage system will be sized to accommodate the 1 in 100 year plus 30% CC event
below ground. During an exceedance event, flows should be permitted to create temporary shallow
depth flooding within the area of public open space. Finished floor levels will be set at a minimum of
150mm above surrounding ground levels ensuring exceedance flooding will not affect the building.
Water Quality
In accordance with the CIRIA C753 publication ‘The SuDS Manual’ (2015), residential roofs have a
‘very low’ pollution hazard level. Individual property driveways and low traffic roads have a ‘low’
pollution hazard level. Table 1 overleaf shows the pollution hazard indices for each land use.
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Table 1 – Pollution Hazard Indices
Land Use Pollution
Hazard Level
Total Suspended
Solids (TSS) Metals Hydrocarbons
Residential roofs Very Low 0.2 0.2 0.05
Individual property
driveways,
residential car
parks and low
traffic roads
Low 0.5 0.4 0.4
Table extract taken from the CIRIA C753 publication ‘The SuDS Manual’ – Table 26.2
* Indices values range from 0-1.
There is potential for runoff to be directed to a pond, detention basin or permeable paving. Table 2
below shows the pollution mitigation offered by these features.
Table 2 – SuDS Mitigation Indices
Mitigation Indices
Type of SuDS Total Suspended
Solids (TSS) Metals Hydrocarbons
Permeable
Pavement 0.7 0.6 0.7
Detention Basin
0.5 0.5 0.6
Pond 0.7 0.7 0.5
Table extract taken from the CIRIA C753 publication ‘The SuDS Manual’ – Table 26.3
It can be concluded that a pond, detention basin and / or permeable paving provide sufficient
treatment. Where attenuation is provided in a below ground attenuation tank or within oversized
pipes, treatment could be provided by a suitably sized separator.
Maintenance
Maintenance of drainage features accommodating runoff up to and including the 1 in 100 year plus
30% CC event will be the responsibility of the site owner. Maintenance can be arranged through
appointment of a site management company.
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Maintenance of oversized pipes accommodating runoff up to and including the 1 in 30 year event
can be offered for adoption to Welsh Water who would then be responsible for their maintenance.
Maintenance schedules for a pond, detention basin, permeable paving and an attenuation tank are
included in Appendix G. The maintenance schedules detail the maintenance requirements and
frequency.
Foul Drainage
DCWW have confirmed through a Hydraulic Modelling Assessment that proposed development foul
flows have potential to cause detriment to the public foul / combined sewer network downstream of
the site.
The DCWW Hydraulic Modelling Assessment identifies two potential solutions to mitigate
development foul flows:
Solution 1: Construction of online storage in two locations within the sewer network
(upsizing of x2 manholes on the 225m public combined sewer adjacent to and within the
A470 east of the site; and upsizing of storage at the Marl Drive Sewage Pumping Station
(SPS)
Solution 2: The removal of 0.084ha (840m²) of impermeable drainage area from the public
combined sewer system upstream of Marl Drive SPS / Combined Sewer Overflow (CSO).
Further investigation has been undertaken by Waterco Consultants and the client to formulate a
viable surface water removal scheme local to the site to offset development foul flows.
Invek Surveys were instructed to undertake a survey to establish the connectivity of the highway
gullies along Marl Lane. As shown on the Invek Survey (Appendix C), highway gullies along a 310m
stretch of Marl Lane, from the junction of Marl Lane and Victoria Drive and the junction of Marl Lane
and Pentywyn Road are draining to the public combined sewer. Assuming a uniform road width of
6.5m, an approximate road surface area of 2,105m² is drained to the public combined sewer.
The foul mitigation proposal is to re-direct highway drainage from the public combined sewer and
into the public surface water sewer within Marl Lane. This will result in highway drainage being
directed to the Afon Wydden via an existing surface water sewer, rather than to the public combined
sewer. As agreed with DCWW, a contributing drainage area of 840m² (840m² of road surface) will
Llys Marl, Llandudno Junction FCA & Drainage Strategy
w10278-170518-FCA and Drainage Strategy 16
need to be removed from the public combined sewer network. To achieve the foul mitigation
proposal, the surface water sewer within Marl Lane will need to be extended west within Marl Lane
to facilitate connections from highway gullies.
Correspondence from DCWW (Appendix C) sets out an agreement in principle to the foul mitigation
scheme. DCWW state that:
‘Your e-mail confirms a solution can be achieved, based on the principle of the surface water removal
scheme, and provided that surface water from a contributing drainage area of 0.084ha is removed,
the principle of connecting foul flows into the public combined sewer system would be considered
acceptable.’
Once a contributing drainage area of 840m² has been removed from the public combined sewer, a
foul connection from the site should be made to the public combined sewer in Marl Lane. The Invek
Survey did not find any public combined sewer manholes within Marl Lane immediately south of the
site. However a lamp-hole with an invert level of 9.66m AOD was identified. A gravity connection to
the public combined sewer in Marl Lane therefore appears feasible. A new connection may require a
new manhole chamber within the highway.
Llys Marl, Llandudno Junction FCA & Drainage Strategy
w10278-170518-FCA and Drainage Strategy 17
Conclusions
The proposed development is for 52 dwellings with associated driveways, gardens, access roads and
public open space.
The developable area of the site is located within Flood Zone A on the Welsh Government
Development Advice Map – an area considered to be at little or no risk of fluvial or tidal flooding,
with a less than 0.1% (1 in 1000) annual probability of flooding.
The flood risk from all sources is considered to be low. The minimum level in the developable area of
the site is 14m AOD and at least 2m above the Flood Zone C1 extent (1 in 1000 annual probability
flood extent) associated with the Afon Wydden.
The proposed development will introduce impermeable area in the form of buildings and roads. The
increase in impermeable area will increase surface water runoff rates. In order to ensure the
increase in surface water runoff will not increase flood risk elsewhere, flow control will be used and
attenuation will be provided to accommodate the 1 in 100 year plus 30% climate change event.
Soakaway testing has confirmed that the site is not suitable for the use of soakaways. As such,
surface water runoff will be discharged to the Afon Wydden via the 300mm public surface water
sewer in Marl Lane. An agreement to connect to the surface water sewer in Marl Lane has been
established with Welsh Water. The required discharge rate is 5 l/s.
In order to achieve a discharge rate of 5 l/s, attenuation will be provided on site. Attenuation could
be provided in the form of a below ground attenuation tank beneath the area of public open space.
Welsh Water, through a Hydraulic Modelling Assessment, state that the proposed development foul
flows have potential to cause detriment to the public combined / foul sewer network. A foul
mitigation strategy has been agreed in principle with Welsh Water whereby:
Development foul flows will be permitted to drain to the public combined sewer in Marl Lane
provided that surface water runoff from a contributing area of 840m² will be removed from the
public combined sewer network. This will be achieved by re-routing highway gullies in Marl Lane
from the public combined sewer and into the public surface water sewer.
Recommendations
1) Submit this report to the Local Planning Authority in support of the planning application.
Llys Marl, Llandudno Junction FCA & Drainage Strategy
w10278-170518-FCA and Drainage Strategy
Appendix A – Location Plan & Aerial Image
DATE:31/01/2017
PLOT NAME:w10278-Location_Plan
REV:-
DRAWN:RCL
CHECKED:AW
APPROVED:VG
PLOT SCALE @ A3:
(UNLESS STATED OTHERWISE)1:5,000
PLOT STATUS:FINAL
PLOT TITLE:
LOCATION PLAN
SCHEME:
LLYS MARL,LLANDUDNO JUNCTION
CLIENT:
BEECH DEVELOPMENTS (NW) LTD
LEGENDSite BoundaryWatercourses / Water Bodies
0 100 200 300 400 50050m
NOTES:1) ALL DIMENSIONS ARE IN METRES AND ALL LEVELS IN METRESABOVE ORDNANCE DATUM UNLESS STATED OTHERWISE±
CONTAINS OS DATA © CROWN COPYRIGHT (2017)
Waterco LtdEden Court, Ruthin, LL15 1NJ
01824 702220www.waterco.co.uk
DATE:31/01/2017
PLOT NAME:w10278-Aerial_Plan
REV:-
DRAWN:RCL
CHECKED:AW
APPROVED:VG
PLOT SCALE @ A3:
(UNLESS STATED OTHERWISE)1:5,000
PLOT STATUS:FINAL
PLOT TITLE:
AERIAL PLAN
SCHEME:
LLYS MARL,LLANDUDNO JUNCTION
CLIENT:
BEECH DEVELOPMENTS (NW) LTD
LEGENDSite Boundary
0 100 200 300 400 50050m
NOTES:1) ALL DIMENSIONS ARE IN METRES AND ALL LEVELS IN METRESABOVE ORDNANCE DATUM UNLESS STATED OTHERWISE±
CONTAINS OS DATA © CROWN COPYRIGHT (2017)BASEMAP: WORLD IMAGERY. SOURCES: ESRI, DIGITALGLOBE, GEOEYE, I-CUBED, EARTHSTAR GEOGRAPHICS, CNES/AIRBUS DS, USDA, USGS, AEX, GETMAPPING, AEROGRID, IGN, IGP, SWISSTOPO, GIS USER COMMUNITY
Waterco LtdEden Court, Ruthin, LL15 1NJ
01824 702220www.waterco.co.uk
Llys Marl, Llandudno Junction FCA & Drainage Strategy
w10278-170518-FCA and Drainage Strategy
Appendix B – Topographical Survey
LP
LP
LP
LP
IC
A
Z
B
378850N 378850N
378900N 378900N
378950N 378950N
379000N 379000N
379050N 379050N
379100N 379100N
279500E
279500E
279550E
279550E
279600E
279600E
279650E
279650E
279700E
279700E
10.91
11.09
11.34
11.62
12.26
12.7012.81
13.1413.23
13.5013.60
13.99
14.1714.26
14.41
14.71
15.05
15.46
15.87
15.93
16.13
16.31
16.64
17.03
17 06
17.15
16.7516 69
16 35
16.44
16.08
15.69
15.80
15 73
15 27
15.18
14.78
14.88
14 85
14.3814.28
14.39
14.0513.97
13.89
13.41
13.51
14.08
13.73
13.89
13.02
13.13
12.49 12.6012.28
12.19
12.17
12.02
12.02
11.82
11.92
11.70
11.8211.58
11.46
11.26
11.39
11.11
11.23
10.81
11.04
11.76
12.14
12.14
11.83
12.19
12.78
13.45
14.04
14.36
14.71
15.04
15.51
16.17
16.42
16.69
17.07
17.32
16.97
16.54
16.02
15.99
15.33
15.09
14.62
14.11
13.01
13.45
15 00
14 63
14.28
13.54
13 00
11 84
11 42
11 2011 06
10 94
10 82
26.54
22.65
10.81
12.53
11.99
11.44
12.14 12
.0012
.11 11.
86
11.97
11.56
11.66
11.3911
.49
11.201
1.0510.92
10.83
10.74
10.84
10.24
10.63
11.53
12.06
12.69
12.80
12.90
12.75 12 76
10.95
11.1511.19
10.91
11 60
11 9511 77
11 95
11 91
12.85
12.28
11.70
11.43
11.07
10.90
11.27
10.83
10.87
10.92
10.87
10.59
10.43
10.25
10.13
10.09
10 71
10.06
10.88
10.91
10.26
10.22
10.95
11.00
10.66
10.45
11.23
11.24
10.97
10.93
11.23
11.41
11.42
11.53
11.36
11.07
11.21
11.37
11.69
11.72
10.04
10.01
9.92
9.88
9.81
9.81
9.97
9.97
10.12
14.6415.75
23.00
22.65
21.93
15.40
15.02
14.91
14.72
14.61
14.61
14.48
14.36
14.33
13.7011.96
11.49
11.28
11.06
10.94
10.71
10.57
10.38
10.37
10.45
10.30
10.45
10.23
10.21
10.06
9.98
10.27
10.56
23.77
26.53
26.28
26.93
28.87
29.11
29.97
30.49
31.02
31.89
27.46
26.92
23.36
27.64
12.59
13.09
11.45
11.39
12.99 10.76
21.71 20.06 17.56
23.71
21.55
20.86
19.90
19.07
18.48
17.88
17.19
16.21
15.83
15.76
15.77
FH
NP
NP
SV
RS
SIGN
BOX
BIN
RIDGE
EAVES
NP
RS/LP
RS
MKR
1.8
WPR 1.4MH2 x MKRS
RIDGE
RIDGE
RIDGE
RIDGE
RIDGE
RIDGE
RIDGE
RIDGE
RIDGE
RIDGE
EAVES
EAVES
EAVES
RIDGE
KTARMAC
FRENCH DRAIN
GRASS
TREES/ HEDGE
HEDGE/ BOTTOM OF BANK
GRASS
K
DK
K K
TARMAC
TREES/ HEDGE
GRASS
IC CL
UTLG
K
IC CL
UTL
GIC CL
UTL
MARL DRIVE
DK
TAR
TAR
LONG GRASS
O/H CANO
PY
O/H CANOPY
O/H CANOPY
WPR 1.4MH
GRASS
GRASS TAR
WOODLAND/ DENSE OVERGROWTH
WOODLAND/ DENSE OVERGROWTH
WOODLAND/ DENSE OVERGROWTH
WOODLAND/ DENSE OVERGROWTH
KERB LINE SHOWN FOR ILLUSTRATIVE PURPOSES ONLY
IC CL
UTL
DK
K
K
UTL
G
IC CL
IC CL
IC CL
IC CL
ICs UTL
IC CL UTL
K
FOOTPATH
FOOTPATH
FOOTPATH
KISSING GATE
KISSING GATE
WALL
SIGN
INACCESSIBLEFOOTPATH
FOOTPATH
INACCESSIBLE
TREE CANOPY/ OVERGROWTH
TOP OF GRASS BANK
WOODLAND
WPR 1.4MH
GRASS
G
A470
TO LLANDUDNO
TREE
O/H CANOPY
POST AND WIRE 1.
2MH
CHAIN LINK 1.4MH
GARDENS
LONG GRASS
FENCE DILAP.
FENCE DILAP.
11.00
11.00
11.00
15.00
15.00
15.00
17.00
17.00
17.00
16.00
16.00
16.00
22.00
12.00
12.00
12.00
14.00
14.00
14.00
13.00
13.00
13.00
18.00
18.00
21.00
20.00
19.00
19.00
10.00
DK
GIVE WAY
279450E
279450E
279750E
279750E
RS
LONG
Reproduction in whole or part is prohibited without the prior permission of Angle Surveys Limited.
Grid - Related to OSGB36 (National Grid) derived from GNSS
EAST NORTH HEIGHT DESCRIPTION
Angle Surveys LimitedPlasEirias Business Centre
Abergele RoadColwyn BayLL29 8BF
+44(0)1492 850050www.anglesurveys.co.uk
enquiries@anglesurveys.co.uk
Project
TOPOGRAPHICAL SURVEYThe Woodlands, Marl Drive
Llandudno JunctionClient
Reference No Drawing No Scale
96/BD/2971 001Survey Stations
Levels - Related to Ordnance Survey Datum derived from GNSS
STATIONS
Revision No: -\ Topographical Survey October 2016
Revisions/ Notes
BolBS
BollardsBus stop
BT British Telecom ICCPS Concrete paving slabsCATV Cable television IC
DR DrainElec Electric ICEP Electric poleER Earth rod
FP Fence postFB Flower BedG GullyGP Gate PostH/C Harcore
IC Inspection cover
KO Kerb outletLB Letter boxLP Lamp postMkr Utility marker
MP Mile postNP Name plate
PO PostPM Parking MeterRE Rodding EyeRS Road signRW Retaining WallSP Soil pipeST Stop tapStay Cable stayTCB Telephone call box
TL Threshold LevelTP Telephone poleTar Tarmacadam
FH Fire Hydrant
VP Vent pipe
WM Water meterWO Water outletUTL Unable to lift
W Water coverK Kerb
DK Drop kerb
O/H OverheadO/G Overgrown
FL 5.55 Floor Level
WL Water level
FENCE ANNOTATIONBW Barb wireWP Wooden panelCI Corrugated iron
CPWP Concrete post Wooden PanelHR Hand railIR Iron railing
CL Chain link
PR Post and railPW Post and wireSF Security fence
PC Post and chain
WPR Wooden Post and Rail
Fence/ Height
Gate
O/H Canopy
Foilage
Survey Control stationCoordinated point
Surveyed point
Spot Level
Legend
A12.28
WP 1.0MH
All critical dimension to be checked on site
Further investigation may be needed to show the full extent of the drainage on site
1:500Scale Factor
1.0000
HMP Hazard Marker Posts
Beech Developments (NW) Ltd,Warwick House,Riverside Business Park,Benarth Road,Conwy, LL32 8UB
Only trees with a bole diameter of 300mm or greater have been surveyed
Groups of trees are shown as a canopy symbol
Fences shown on the survey do not necessary represent legal boundaries
Pipe sizes are approximation only
A 279608.837 378877.218 13.553
B 279648.112 378841.168 11.247
Z 279600.458 379039.656 17.689
Road Nail
Road Nail
Wooden Peg
Llys Marl, Llandudno Junction FCA & Drainage Strategy
w10278-170518-FCA and Drainage Strategy
Appendix C – Drainage Survey, Sewer Plan, & DCWW Correspondence
VC 2
25 m
m.
VC 375 m
m.
VC 2
25 m
m.
VC 150 m
m.
MDPE 100 mm.
VC 225 mm.
VC 300 mm.
VC 2
25 m
m.VC
225
mm.
VC 2
25 m
m.
VC 2
25 m
m.
VC 225 mm.
VC 150 mm.
VC 150 mm.
VC 150 mm.
VC 150 mm.
VC 150 mm.
VC 1
50 m
m.
VC 2
25 m
m.
VC 225 mm.
VC 225 mm.
VC 1
50 m
m.
VC 150 mm.
VC 1
50 m
m.
VC 150 mm.
VC 150 mm.
VC 1
50 m
m.VC 150 mm.
VC 1
50 m
m.
VC 150 mm.
VC 225 mm.
VC 150 mm.
VC 225 mm.
VC 2
25 m
m.
VC 2
25 m
m.
VC 225 mm.
VC 225 mm.
VC 225 mm.
VC 2
25 m
m.
VC 225 mm.
VC 225 mm.
VC 150 mm.
VC 2
25 m
m.
VC 225 mm.
VC 225 mm.
VC 225 mm.
VC 225 mm.
VC 150 mm.
VC 150 mm.
VC 2
25 m
m.
VC 225 mm.
VC 225 mm.
VC 150 mm.
VC 150 mm.
VC 225 mm.
VC 2
25 m
m.
VC 225 mm.
VC 150
mm.
VC 225 mm.
VC 225 mm.
VC 150 mm.
VC 2
25 m
m.
VC 150 mm.
VC 225 mm.
CONC 600 mm.
VC 225 mm.
VC 150 m
m.
CONC 1050 mm.
VC 225 mm.
VC 150 mm.
VC 150 mm.
VC 150 mm.
VC 225 mm.
VC 2
25 m
m.
VC 225 mm.
VC 2
25 m
m.
VC 2
25 m
m.VC
225
mm.
VC 225 mm.
CONC 600 mm.
CONC 900 mm.
VC 150 mm.
VC 150 mm.
VC 225 mm.
VC 225 mm.
VC 225 mm.
VC 225 mm.
VC 225 mm.
VC 225 mm.
VC 225 mm.
VC 150 mm.
uPVC
150
mm.
VC 2
25 m
m.
VC 225 m
m.
VC 2
25 m
m.
VC 225 mm.
VC 375 mm.
VC 300 mm. VC 300 mm.
VC 150 mm.
VC 225 mm.
VC 225 mm.
VC 225 mm.
VC 2
25 m
m.
VC 1
50 m
m.
VC 1
50 m
m.VC 150 mm.
VC 225 m
m.
VC 150 mm.
VC 150 mm.
VC 150
mm.
VC 150 mm.
CONC 600 mm.
VC 375 mm.
VC 225 mm.
VC 150 mm.
VC 150 mm.
VC 150 mm.
VC 225 mm.
CONC 1200 mm.
VC 225 mm.
CONC 600 mm.
VC 150
mm.
VC 150 mm.
VC 150
mm.
VC 150 mm.
CONC 105
0 mm.
CONC 1
050 mm
.VC 300 mm.
VC 300 mm.
VC 300 mm.
VC 225 mm.
VC 225 mm.
VC 1
50 m
m.
VC 225 mm.
VC 225 mm.
VC 375 mm.
VC 225 mm.
VC 150 mm.
VC 150 mm.
VC 150 mm.
VC 900 mm.
CONC 1050 mm.
CONC 1050 mm.
CONC 1050 mm.
VC 150 mm.
VC 100 mm.
VC 150 mm.
VC 1
50 m
m.
VC 1
00 m
m.
CONC 750 mm.VC 150 mm.
VC 150 mm.
VC 100 mm.
VC 100 mm.
VC 150 mm.
VC 150 mm.
VC 150 mm.
VC 100 mm.
VC 100 mm.
VC 100 mm.
VC 100 mm.
VC 1
00 m
m.
VC 100 mm.
VC 100 mm.VC 1
00 m
m.VC
100
mm.
VC 1
00 m
m.VC
100
mm.
VC 100 mm.
VC 150 mm.
VC 150 mm.VC
150 mm
.
VC 150 mm.
CI 100 mm. uP
VC 150 mm.
VC 150 mm. VC 150 mm.
VC 150 mm.
VC 150 mm.VC 150 mm.
VC 150 mm.
CONC 450 mm.CONC 450 mm.
CONC 450 mm.
CONC 450 mm.
VC 225 mm.
CONC 450 mm.
CONC 450 mm.
CONC 450 mm.
CONC 450 mm.
CONC 450 mm.
CONC 450 mm.
VC 150 mm.
S 104 S 104S 104
S 104S 104
S 104S 104
S 10
4
S 104 S 104
S 104S 104
S 104S 104
S 10
4
S 104
S 104S 104
S 104
S 104
S 104
S 104S 104
S 104S 104
S 104
S 104S 104
S 104S 104
S 104
S 10
4
S 104
S 104 S 104S 104
S 104
S 104
S 104
S 104
S 104 S 104
S 104S 1
04
S 104
S 104S 104
B
A
A
A
B
B
B
B
B
B
BB
B
B
B
A
A
BB
B
B
BB
A
B
B
B
B
BB
B
B
B
B
B
B
B
B
BB
B
B
B
B
BB
BB
B
B
B
B
B
BB B
B
B
B
B
B
B
B
B
BB
BB
B
SH79782403
SH79783403
SH79784401
SH79794006
SH79785909
SH79784902
SH79794002
SH79794007
SH79794008
SH79784906
SH79784907SH79784908
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SH79794005
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SH79784507
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SH79782803
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SH79784912
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SH79784508
SH797902
05
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SH78799201
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SH79792001
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SH79785404 SH79786401
SH79786402
SH79787410SH79787411
SH79787415SH79787416 SH79787422
SH79787423
SH79787432SH79787433
SH79787435
SH79787421
SH79787420
SH79788407SH79787414
SH79786405 SH79789410SH79789409SH79789401
SH79795002
SH79787604
SH79787504 SH79787506SH79787507SH79787508SH79787505
SH79787503
SH79787502
SH79785901
SH79787509
SH79787605
SH79786703
SH79785902
SH79785908SH79785904
SH79785905
SH79785906
SH79786611
SH79787601
SH79787551
SH79788501
SH79785501
SH79785502 SH79785503
SH79785504
SH79795401
SH79795301
SH79795201
SH79787602
SH79786504
SH79786502
SH79786501
SH79786503
SH79796002
SH79786802
SH79786804
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SH79796101
SH79785803
SH79785804
SH79786801
SH79785801
SH79786901
SH79796001
SH79787501
SH79787603SH79786602
SH79786603
SH79786604
SH79786605
SH79785606
SH797865
05
SH79786607
SH79787510
SH79787511
SH79787512
SH79787513
SH79785505
SH79786507
SH79786618
SH79786702
SH79786613
SH79786614
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SH79786615
SH79786616
SH79786617
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SH79786619
SH79786620
SH79786621
SH79786622
SH79786623
SH79786705
SH79786704
SH79786612
SH79786701
SH79785601
SH79795001
SH79786609
SH79786608
SH79785602
SH79786610
SH79780901
SH79784602
SH79783802
SH79780703
SH79784901
SH79780801
SH79785903
SH79785805
SH78799205SH78799206
SH78799207
SH78799208SH78799209SH78799210
SH78799211 SH78799212SH78799213
SH79790210SH79790211 SH79790212
SH79790213 SH79790214
SH79790215
SH79790216
SH79790218SH79790219
SH79790220
SH79790221
SH79790222
SH78799223SH79790223
SH79790244 SH79790245
SH79790246SH79790250
SH79790251
SH79790252
SH79790253SH79790254
SH79790255
SH79790256
SH79790257SH79790258
SH79790259
SH79790261
SH79790262
SH79790263
SH79790264SH78799265SH78799266
SH78799267
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SH78799238 SH78799239
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SH79790260
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SH79790266
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SH7979
0268
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SH79790299
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SH79790273SH79790274
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SH79790276SH79790277
SH79790278
SH7979
0280
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SH7979
0284
SH78799202
SH78799230
SH79783426SH79783432
SH79783534SH79783535
SH79784805
SH79784806
SH79784915
SH79784914SH79784916
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SH79784918
SH79785918
SH79785818
SH79784807SH79784808
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SH79784927SH79784928
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SH79784830SH79784831
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SH79784836
SH79784837 SH79784838SH79784839
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SH79784710
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SH79785715
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SH79784842
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SH79784844
SH79784845
SH79784846
SH79784847SH79783848
SH79784849
SH79784850
SH79785851
SH79785852
SH79785953
SH79785854SH79784855SH79784856 SH79785857
SH79784858
SH79784959SH79785960
SH79782611SH79782612
SH79788502
SH78799105
SH78799109
SH78799113
SH78799115
SH78799116
SH78799117
SH78799119
SH78799120SH78799121
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SH79790110SH79790111
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SH79790115SH78799127
SH79790117
SH78799118
SH78799130
SH79790118
SH78799128
SH79790120 SH79790121
SH79790125
SH78799145
SH79782905
SH79782914SH79782915
SH79782704
SH79782705
SH79780750
SH79780751
SH79780752
SH79781850
SH79781851SH79781852SH79781853
SH79781854
SH78799280
SH79787751
SH79790270
SH79790050
SH79784752
SH79795060
SH79785940
SH79783751
SH79783750
SH78799365SH78799366
SH79790292
SH79782998
SH79783820SH79782819
SH79785603SH79785604
SH79785605
SH79784603
SH79784604
SH79784605SH79784606
SH79784607
SH79784608
SH79784609
SH79784715
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SH79785701
SH79785802
SH79785820
SH79784723SH79784724
SH79784725SH79784726
SH79784727
SH79784728
SH79784610
SH79784611
SH79784612
SH79784613
SH79784614SH79784615 SH79784616 SH79784617
SH79785608 SH79785609
SH79785610SH79785611
SH79784511
SH79784630
SH79785531
SH79785532
SH79785533
SH79785634SH79785635
SH79784729
SH79785716SH79785717
MHF2
6801
S4C3
S1 CONTROL
6703
FW7
MHS5
MHS4A
MHF1
S3
S2
S1
MHS7AMHS7
SW7A/1
S2
0102
S1
S3S4
F4
F6
4401
0202
0101
F6
FW5
FW4
SW?
C4
C2
C1
0201
S3
S2
MHS10
SW9SW8
S7
S7A
SW6S6.7SW6.4
22 MARL VI
19/20 SHAM
SHAMROCK C
JUNCTION TJUNC TIR E
28 LLWYN E1604 36 LLWYN E
1 LLWYN ES
13 LLWYN E13 LLWYN E
12 LLWYN E12 LLWYN E
21 LLWYN E
MHS6
MHS8
MHF3
4504
0103
2001
1002
1001
1 MARL MEW
32 TAN Y B32 TAN Y B
18 TAN Y B
JUNCTION A
71 ALBERT
48 TIR EST
3 TIR ESTY3 TIR ESTY
21 LLWYN E21 LLWYN E
25 TAN Y B
27/29 TAN34 TAN Y B
7/9 TAN Y7/9 TAN Y
18 TAN Y B
17 TIR EST17 TIR EST
19 TIR EST19 TIR EST
4 TAN Y BE4 TAN Y BE
23 TIR EST23 TIR EST
48 TIR EST
19 BRYN MA29 BRYN MA
19 BRYN MA19 BRYN MA
37/39 BRYN37/39 BRYN
23/35 BRYN23/35 BRYN
29062907
GARAGES 9
68/70 ALBE
66 ALBERTSIDE OF 68
43 ALBERT
39 ALBERT
34 ALBERT
7 MAES GLAGARAGES 9
7 MAES GLA3 MAES GLA
35023501
9 CWM ESTY9 CWM ESTY
9 DOL HUDO9 DOL HUDO
93 VICTORI93 VICTORI
99 VICTORI99 VICTORI
99 VICTORI
49 BRYN MA49 BRYN MA
BRYN MARL
91 VICTORA
4701
77 VICTORI
90 VICTORI
S4S5 C1
C2
S5
F7
F5F3
F2
F1
4501
JUNCTION M
8407
6405 94019402 9410
SUMPF13
9409
95 MARL LA
F16F15
5401
5404
5405
5 GLAS COE
2 GLAS COEF31
F30
F29F28
S2
S13AS13
MHS12
MHS11
SW4SW3FW2
SW10
S3
S2
S1
MH1002
S7
S5
S9
S8
S13
F10
F9
F8
F18S8 S7
S6
S5
S4
S12
S11
S10
S9
F17
F7
F6
F5
F4
F3
F2
SW5
SW5.1
F1
S15
S14
F25F24F23
S14
MH1003F14
F13
F12
F11
5301
5201
6101
5
5801
6901
6802
6804
6803SH79785802
8501
5501
5502 5503
5504
7602
7605
6504
6503
6502
6501
6001
6002
5
5401
5902
5901
MHS14
MHS13
F20F21F22
FW3
lamphole
lamphole
lamphole
lamphole
lamphole
lamphole
lamphole
S14
S2 S3
SPC
SPCSPC
SPC
SPC
SPC
SPC
SPC
c 215.15
c 14.02i 13.21
i 41.4
i 42.15
c 43.39i 40.74
c 43.73i 40.78
c 44.84i 40.94
c 43.01i 41.17
c 33.12
c 34.68
c 33.87
c 23.02
c 33
c 27.81
c 25.16
c 43.21i 40.71 c 42.99
i 40.66c 42.82i 40.59c 42.61
i 40.48
c 7.4i 5.7
c 7.51i 5.65
c 7.961i 5.91
c 8.243i 6.206
c 215.15i 0
c 8.12i 5.91
c 10.84
i 45 i 44.75
i 43.75
i 43.45i 43.08i 43.62
i 44.05 i 43.35i 43.6
i 42.7 i 42.21 i 42.06
i 41.9i 41.77
i 41.72i 41.58
i 41.58 i 40.7
i 40.83i 40.94
i 41
i 42i 42.45
i 42.15i 41.99
i 42.15i 42
i 41.6i 41.7 i 41.83
i 42.35
i 41.96
i 42.11i 42.4
i 42.1
i 42.1
i 42.3
i 42.3
i 42.44i 42.95i 43.3
i 43.4
i 43
i 43.75
i 43.88i 45.05
i 44.55
i 45.08
i 44.96
i 45.2i 45.6
i 45.85
i 44.64i 43.9 i 43.29i 45
i 45.75 i 43.5
i 43.47i 44.13
i 44.28 i 43.65
i 42.22
i 42.5
i 42.09
i 42.09
i 41.94 i 41.62
i 42.25i 41.95
i 42.41i 42.25
i 42.4
i 42.58i 42.53
i 41.96i 42.23i 42.6
i 42.4i 42.15
i 41.7
i 44.98
i 43.61
i 45.65
i 45.59
i 44.4
i 45.85
i 43.58
i 43.87
i 43.71
i 42.13
i 42.84i 42.95
i 43.87
i 42.33
i 42.9
i 42.32
i 41.56i 41.76
i 41.65
i 42.4i 41.38i 42.2
i 41.81
i 42.2
i 43.55i 41.45
i 43.28
i 41.3i 42.5i 42.5
SH79784502
SH79787606
SH79786902
SH79787750
outfall
6
259MARL LANE
366MEADOWS LLANDUDNO JUNC
71933WOODLANDS SPS
FW
CW
CF
ED Bdy
Track
Und
Path (
um)
Byre Cottage
PistyllCoed y
Sports Ground
Caravan Park
Hall
Bodysgallen Hall
BRON
THE
DOLGOED
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Overlea Court
LANE
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BRYN-Y-COED
A 470
SHAM
ROCK
TERR
ACE
MARL
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LLWYN ESTYN
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4
2
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6
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14
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10
11
21
40
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27
22
19
12
36
37
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72
94
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52
18
16
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25
29
33
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24
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68
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92
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66
82
67
86
13
31
57
78
63
99
54
83
80
95
32
73
51
62
56
61
53
90
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59
69
55
70
114
101
128
116
112
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108
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117
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107
126
113
119
Play Area
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North Wales
Shelter
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Sham
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Sinks
Grid
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17.5m
26.8m
29.6m
33.2m
35.3m
46.0m
38.3m
24.5m
39.0m
35.5m
Cattle Grid
9.3m
Tank
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Llys Aled
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Path
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Cobblestones
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w10278, Llys Marl, Marl Lane
Dwr Cymru Cyf gives this information as to the position of its underground apparatus by way of general guidance only on thestrict understanding that it is based on the best information available and no warranty as to its correctness is relied upon in the event of excavations or other works made in the vicinity of the Company’sapparatus and any onus of locating the apparatus before carrying out any excavations rests entirely on you. It must be understoodthat the furnishing of the information is entirely without prejudice to the provision of the New Roads and Streetworks Act 1991 and ofthe Company’s right to be compensated for any damage to its apparatus.Service pipes are not generally shown but their presence should be anticipated.
EXACT LOCATIONS OF ALL APPARATUS TO BE DETERMINED ON SITE.
Reproduced by permission of Ordnance Survey on behalf ofHMSO. © Crown copyright and database right 2008.
All rights reserved.Ordnance Survey License number 100019534.
Printed on:Printed by:
1:1,250Map scale:
Notes:
LEGEND(Representative of most common features)
Map Ref: 279591,378984
AM28/03/2017
Private Sewer Transfer
Inspection ChamberLateral Drain
Whilst every reasonable effort has been taken to correctly record the pipe material of DCWW assets, there is a possibility that in some cases, pipe material (other than Asbestos Cement or Pitch Fibre) may be found to be asbestos cement (AC) or Pitch Fibre (PF) . It is therefore advisable that the possible presence of AC or PF pipes be anticipated and considered as part of any risk assessment prior to excavation
1
Aled Williams
From: Jones Sion <Sion.Jones@dwrcymru.com>Sent: Tuesday, May 9, 2017 2:47 PMTo: Aled WilliamsCc: Jones-Hughes HenrySubject: RE: w10278 - Llys Marl, Marl Lane, Llandudno Junction
Hi Aled, Thanks for your response. Your e‐mail confirms a solution can be achieved, based on the principle of the surface water removal scheme, and provided that surface water from a contributing drainage area of 0.084ha is removed, the principle of connecting foul flows into the public combined sewer system would be considered acceptable. Accordingly, in respect of any forthcoming planning application, it is recommended that an accompanying proposed drainage strategy is formulated to address the proposed surface water removal scheme including your calculations which equate to an area of 0.084ha and evidence from your recent CCTV survey that confirms the connectivity of highway gullies. Prior to any planning application, however, I would also remind there is now a mandatory legislative requirement as of 1st August 2016 to undertake pre‐application consultation with all ‘Specialist Consultees’, including Welsh Water, in respect of any major developments as outlined in the Town & Country Planning (Development Management Procedure) (Wales) (Amendment) Order 2016. Please note this is separate to Welsh Water’s formal pre‐planning service – which is non‐statutory and was previously subject of PPA0000551 – and entails due process and submission of relevant forms i.e. Schedule 1C – Article 2D Notice; a substantive response would be required within 28 days from the date of the notice, as per the requirements of Article 2E. This statutory pre‐application consultation exercise would offer an opportunity for consultees to comment on the draft planning application submission and at this stage it would be useful to provide a copy of the draft drainage strategy. This is effectively a frontloading exercise that should ease the application process and on the proviso that the strategy includes the relevant evidence base, it should overcome any request for pre‐commencement conditions as part of our consultation response. On this subject, and from our previous correspondences below, I trust that pre‐planning consultation is or has also been undertaken with the Trunk Roads Agency and NRW in regards to discharging into the Afon Wydden. I hope this information is of assistance and look forward to hearing back from you in regards to the above. Regards, Siôn
Siôn Jones
Development Control Officer | Developer Services | Dwr Cymru Welsh Water
Linea | Cardiff | CF3 0LT | T: 0800 917 2652| www.dwrcymru.com
We will respond to your email as soon as possible but you should allow up to 10 working days to receive a response. For most of the services we offer we set out the timescales that we work to on our Developer Services section of our website. Just follow this link http://www.dwrcymru.com/en/Developer‐Services.aspx and select the service you require where you will find more information and guidance notes which should assist you. If you cannot find the information you are looking for then please call us on 0800 917 2652 as we can normally deal with any questions you have during the call. If we’ve gone the extra mile to provide you with excellent service, let us know. You can nominate an individual or team for a Diolch award through our website.
Before you print please think about the ENVIRONMENT
2
From: Aled Williams [mailto:Aled.Williams@waterco.co.uk] Sent: 04 May 2017 15:57 To: Jones Sion <Sion.Jones@dwrcymru.com> Cc: Jones‐Hughes Henry <Henry.Jones‐Hughes@dwrcymru.com> Subject: RE: w10278 ‐ Llys Marl, Marl Lane, Llandudno Junction
******** External Mail ******** Hi Sion, Many thanks for your reply and for confirming the discharge rate for surface water flows. Based on your email it appears that the principle of the surface water removal scheme to offset development foul flows is acceptable in principle subject to removing a contributing area of 0.084ha from the combined system. With reference to the impermeable area of 0.084 ha, we note that the modelling report suggests that this would equate to a road length of 130m (assuming a 6.5m wide road). A review of the attached gully connectivity survey shows that highway gullies are draining to the public combined sewer along a road length of approximately 380m. We will therefore be able to remove the required 0.084ha contributing area from the combined system. For confirmation and agreement in principle, please could you confirm that development foul flows can drain to the public combined sewer system provided that surface water from a contributing drainage area of 0.084ha is removed from the combined sewer. Surface water removal would be in the form of disconnecting highway gullies from the public combined sewer in Marl Lane and connecting them into the public surface water sewer (which discharges to a watercourse). Kind Regards,
Aled Williams BSc (Hons) MCIWEM Senior Environmental Consultant 01824 702220
Ruthin - Chester - Manchester - Hyderabad Assessment, Modelling, Design
For email confidentiality, limitations and company details please see our disclaimer webpage. Registered in Wales under company no. 3577754. Waterco Ltd, Eden Court, Ruthin LL15 1NJ
From: Jones Sion [mailto:Sion.Jones@dwrcymru.com] Sent: Thursday, May 4, 2017 3:07 PM To: Aled Williams Cc: Jones-Hughes Henry Subject: RE: w10278 - Llys Marl, Marl Lane, Llandudno Junction Good Afternoon Aled, Thanks for your previous e‐mails. Firstly, in respect of your e‐mail last Wednesday (26th), I apologise for any confusion caused as you rightly highlight that the off‐site surface water removal scheme would not be subject to the hierarchical approach set out under Part H of Building Regulations and therefore would not require infiltration testing to support a scheme for soakaways.
3
Notwithstanding this, having discussed the matter with our modelling team and referred back to the original Hydraulic Modelling Report, it was brought to my attention that the surface water removal scheme solution (Section 6.2) would require removal of 0.084 ha of impermeable area upstream of Marl Drive CSO; your previous e‐mail, dated 6th April, identified a scheme for the removal of approx. 213sqm. I communicated your calculations to the modelling team who reiterated that 0.084 ha of impermeable area would be required to mitigate the detriment predicted by the additional development flows and hence the scheme (equating to 0.0213ha) falls significantly short to satisfy the HMA requirement. I am happy to review any additional information should you wish to revert back to me on the matter, for example I note that the survey identified connectivity of a number of other highway gullies along Marl Lane. You mentioned scope for a meeting in your previous e‐mail but unfortunately, being based in our Linea office in Cardiff, this isn’t something I would be able to arrange and therefore would be grateful to continue the dialogue in e‐mail correspondences. In the meantime, having had an opportunity to review our exchange of e‐mails below and your accompanying Ground Investigation Report (attached), namely Section 7.7 and Appendix C regarding soakaway tests, I am satisfied that you’ve investigated and exhausted alternative drainage options under Part H of Building Regulations and would therefore accept discharge into the public surface water sewer at an attenuated rate. Accordingly, in respect of any future planning application submission, please accept this e‐mail as an agreement in principle to allow for communication of surface water into the said public sewer through an attenuation device that discharges at a rate not exceeding 5 l/s. I trust this information is of assistance. Regards, Siôn
Siôn Jones
Development Control Officer | Developer Services | Dwr Cymru Welsh Water
Linea | Cardiff | CF3 0LT | T: 0800 917 2652| www.dwrcymru.com
We will respond to your email as soon as possible but you should allow up to 10 working days to receive a response. For most of the services we offer we set out the timescales that we work to on our Developer Services section of our website. Just follow this link http://www.dwrcymru.com/en/Developer‐Services.aspx and select the service you require where you will find more information and guidance notes which should assist you. If you cannot find the information you are looking for then please call us on 0800 917 2652 as we can normally deal with any questions you have during the call. If we’ve gone the extra mile to provide you with excellent service, let us know. You can nominate an individual or team for a Diolch award through our website.
Before you print please think about the ENVIRONMENT
From: Aled Williams [mailto:Aled.Williams@waterco.co.uk] Sent: 27 April 2017 14:18 To: Jones Sion <Sion.Jones@dwrcymru.com> Cc: Jones‐Hughes Henry <Henry.Jones‐Hughes@dwrcymru.com> Subject: RE: w10278 ‐ Llys Marl, Marl Lane, Llandudno Junction
******** External Mail ******** Hi Sion, Further to my below email, I am now pleased to attach the requested ground investigation report for the Llys Marl / Woodlands site. See section 7.7 for conclusions regarding soakaway tests. With the attached evidence, please advise if you are now in a position to agree a surface water connection in principle to the public surface water sewer from the proposed development site. I also look forward to hearing back from you in regards to the proposed foul mitigation strategy.
4
Kind Regards,
Aled Williams BSc (Hons) MCIWEM Senior Environmental Consultant 01824 702220
Ruthin - Chester - Manchester - Hyderabad Assessment, Modelling, Design
For email confidentiality, limitations and company details please see our disclaimer webpage. Registered in Wales under company no. 3577754. Waterco Ltd, Eden Court, Ruthin LL15 1NJ
From: Aled Williams Sent: Wednesday, April 26, 2017 5:13 PM To: Jones Sion Cc: Jones-Hughes Henry Subject: RE: w10278 - Llys Marl, Marl Lane, Llandudno Junction Hi Sion, Many thanks for your reply. In regards to infiltration testing, I understand that this would be required prior to agreeing discharge to the public surface water sewer from the proposed development. The developer will arrange for these to be undertaken on site as part of the planning process. However, please could you explain why infiltration testing would be required to support a surface water removal scheme for flows currently entering the public combined sewer. Our proposal is for off‐site works within a public highway (diverting highway gullies from the public combined to a surface water sewer) approximately 180m from the site. This is not somewhere that we can realistically look at introducing soakaways. If necessary, I am happy to meet at your Bodelwyddan office to discuss the scheme further. Kind Regards,
Aled Williams BSc (Hons) MCIWEM Senior Environmental Consultant 01824 702220
Ruthin - Chester - Manchester - Hyderabad Assessment, Modelling, Design
For email confidentiality, limitations and company details please see our disclaimer webpage. Registered in Wales under company no. 3577754. Waterco Ltd, Eden Court, Ruthin LL15 1NJ
5
From: Jones Sion [mailto:Sion.Jones@dwrcymru.com] Sent: Wednesday, April 26, 2017 2:25 PM To: Aled Williams Cc: Jones-Hughes Henry Subject: RE: w10278 - Llys Marl, Marl Lane, Llandudno Junction Good Afternoon Aled, Apologies for the delay in my response, I only had an opportunity to issue the information contained in your proposed surface water removal scheme below to the modelling team on my return from leave last week, but will chase on the matter. Based on the information set out below I would envisage a positive outcome, particularly the scope for further SW removal options from the Junction of Marl Lane and Victoria Drive up to the Junction with Pentwyn Road, but will revert to feedback from the modelling team to confirm if the calculations and area identified would be sufficient. Apologies for the delay and I will report back at the earliest possible opportunity. In the meantime, however, I acknowledge that the proposed SW removal scheme seeks disposal into the public surface water sewer but there is still the matter of infiltration testing as part of your evidence base to establish any principle to agree a SW connection. Can you update me on the results of these tests please? Regards, Siôn
Siôn Jones
Development Control Officer | Developer Services | Dwr Cymru Welsh Water
Linea | Cardiff | CF3 0LT | T: 0800 917 2652| www.dwrcymru.com
We will respond to your email as soon as possible but you should allow up to 10 working days to receive a response. For most of the services we offer we set out the timescales that we work to on our Developer Services section of our website. Just follow this link http://www.dwrcymru.com/en/Developer‐Services.aspx and select the service you require where you will find more information and guidance notes which should assist you. If you cannot find the information you are looking for then please call us on 0800 917 2652 as we can normally deal with any questions you have during the call. If we’ve gone the extra mile to provide you with excellent service, let us know. You can nominate an individual or team for a Diolch award through our website.
Before you print please think about the ENVIRONMENT
From: Aled Williams [mailto:Aled.Williams@waterco.co.uk] Sent: 24 April 2017 13:44 To: Jones Sion <Sion.Jones@dwrcymru.com> Cc: Jones‐Hughes Henry <Henry.Jones‐Hughes@dwrcymru.com> Subject: RE: w10278 ‐ Llys Marl, Marl Lane, Llandudno Junction
******** External Mail ******** Hi Sion, Please could you let me know if you have had an opportunity to review my email below. We require a response as soon as possible. Kind Regards,
Aled Williams BSc (Hons) MCIWEM Senior Environmental Consultant 01824 702220
6
Ruthin - Chester - Manchester - Hyderabad Assessment, Modelling, Design
For email confidentiality, limitations and company details please see our disclaimer webpage. Registered in Wales under company no. 3577754. Waterco Ltd, Eden Court, Ruthin LL15 1NJ
From: Jones Sion [mailto:Sion.Jones@dwrcymru.com] Sent: Friday, April 7, 2017 5:27 PM To: Aled Williams Cc: Jones-Hughes Henry Subject: RE: w10278 - Llys Marl, Marl Lane, Llandudno Junction Hi Aled, Apologies, I haven’t had an opportunity to respond or review the information submitted in any great detail and I will be on annual leave next week, returning Tuesday 18th, but will endeavour to respond with feedback in the week following. This is a matter I will need to research in a bit more detail based on the attached and your e‐mail below. Please do not hesitate to call me in the week following Easter (WC 18th). Regards, Siôn
Siôn Jones
Development Control Officer | Developer Services | Dwr Cymru Welsh Water
Linea | Cardiff | CF3 0LT | T: 0800 917 2652| www.dwrcymru.com
We will respond to your email as soon as possible but you should allow up to 10 working days to receive a response. For most of the services we offer we set out the timescales that we work to on our Developer Services section of our website. Just follow this link http://www.dwrcymru.com/en/Developer‐Services.aspx and select the service you require where you will find more information and guidance notes which should assist you. If you cannot find the information you are looking for then please call us on 0800 917 2652 as we can normally deal with any questions you have during the call. If we’ve gone the extra mile to provide you with excellent service, let us know. You can nominate an individual or team for a Diolch award through our website.
Before you print please think about the ENVIRONMENT
Please note I will be on annual leave during the week commencing Monday 10th, returning on Tuesday 18th. If you require assistance in my absence I would kindly request that you e‐mail your enquiry to Developer Services at developer.services@dwrcymru.com or telephone 0800 917 2652.
From: Aled Williams [mailto:Aled.Williams@waterco.co.uk] Sent: 06 April 2017 10:05 To: Jones Sion <Sion.Jones@dwrcymru.com> Cc: Jones‐Hughes Henry <Henry.Jones‐Hughes@dwrcymru.com> Subject: RE: w10278 ‐ Llys Marl, Marl Lane, Llandudno Junction
******** External Mail ******** Hi Sion,
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Further to discussions regarding the Llys Marl site and following review of the Welsh Water Hydraulic Modelling Report we have looked into a scheme for surface water removal from the public combined sewer system to offset development foul flows. Solution 2 within the HMR details a scheme for surface water removal. However, we have identified a surface water removal scheme local to the site which will be more cost effective. Our proposal is based upon the removal of highway drainage from the public combined sewer system within Marl Lane. I attach an Invek survey showing the connectivity of the highway drainage (gullies) along the length of Marl Lane. The survey shows that highway gullies south of the site are drained to a private 150mm surface water sewer (assumed to be subject to S104 adoption agreement) which serves the recent Llys Onen development south of Marl Lane. This sewer discharges to watercourse. Highway gullies further north‐west along Marl Lane are shown to discharge to the public combined sewer system. Proposal Our proposal is to remove highway gullies from the combined system in Marl Lane and re‐direct them into the surface water sewer (which discharges to watercourse). The HMR indicates that the average foul flow to be generated from the development is 0.417 l/s. Applying a peaking factor (x6 +10%) gives a peak foul flow rate of 2.75 l/s (for a 70 dwelling scheme). 54 properties will likely be proposed in the final planning stage and as such the peak flow of 2.75 l/s is a conservative rate. The surface water removal scheme therefore needs to remove 2.75 l/s from the combined sewer to offset foul flows. Using the rational method to calculate rainfall runoff from the road, a drainage area of 210m² would need to be removed from the combined system to offset development peak foul flows (2.75 l/s). This is based on a rainfall intensity of 47.11mm over a 6 hour duration 1 in 30 year rainfall event. Removal of gullies G19 and G20 shown on the attached ‘Marl Lane Gully Connectivity – 2’ plot would remove a contributing drainage area of approximately 213m² and would offset development foul flows. A new length of sewer of approximately 50m would be required to connect the highway gullies to the 150mm surface water sewer in Marl Lane. Please could you advise on the acceptability of the above proposal to Welsh Water and also the acceptability of the use of 1 in 30 year rainfall data within our calculations. I trust the above provides a less intrusive and cost effective solution than suggested within the HMR and also identifies potential further surface water removal options to Welsh Water (highway drainage from the Junction of Marl Lane and Victoria Drive up to the Junction with Pentwyn Road is all drained to the public combined system). Kind Regards,
Aled Williams BSc (Hons) MCIWEM Senior Environmental Consultant 01824 702220
Ruthin - Chester - Manchester - Hyderabad Assessment, Modelling, Design
8
For email confidentiality, limitations and company details please see our disclaimer webpage. Registered in Wales under company no. 3577754. Waterco Ltd, Eden Court, Ruthin LL15 1NJ
From: Jones Sion [mailto:Sion.Jones@dwrcymru.com] Sent: Thursday, March 30, 2017 3:27 PM To: Aled Williams Subject: RE: w10278 - Llys Marl, Marl Lane, Llandudno Junction Good Afternoon Aled, Thanks for your e‐mail and apologies for the delay in my response, I haven’t had an opportunity to chase on the matter of point of connection with the preceding Development Control Officer or Modelling Team but will do so this afternoon. In the meantime, in respect of your e‐mail below, I appreciate that you have already undertaken extensive research into alternative options for disposal of surface water which is evidently comprehensive including the recent survey work undertaken by Invek. However as per my previous e‐mail, and in reference to the hierarchy set out under Part H of Building Regulations, I would reinforce that the results of infiltration testing will need to be provided upfront as an evidence base before the principle of a connection to the public surface water sewer can be agreed. I appreciate this is your intention regardless but only on receipt of this evidence would we be able to progress discussions regarding an acceptable discharge rate into the sewer. Notwithstanding this, the attached documents accompanying your e‐mail gives assurance that a low discharge rate can be achieved on this site and we would welcome the information that supports this calculation. I appreciate this doesn’t expand a great deal on my last e‐mail but will happily discuss and review any further information in future correspondences. Regards, Siôn
Siôn Jones
Development Control Officer | Developer Services | Dwr Cymru Welsh Water
Linea | Cardiff | CF3 0LT | T: 0800 917 2652| www.dwrcymru.com
We will respond to your email as soon as possible but you should allow up to 10 working days to receive a response. For most of the services we offer we set out the timescales that we work to on our Developer Services section of our website. Just follow this link http://www.dwrcymru.com/en/Developer‐Services.aspx and select the service you require where you will find more information and guidance notes which should assist you. If you cannot find the information you are looking for then please call us on 0800 917 2652 as we can normally deal with any questions you have during the call. If we’ve gone the extra mile to provide you with excellent service, let us know. You can nominate an individual or team for a Diolch award through our website.
Before you print please think about the ENVIRONMENT
From: Aled Williams [mailto:Aled.Williams@waterco.co.uk] Sent: 22 March 2017 09:49 To: Jones Sion <Sion.Jones@dwrcymru.com> Subject: RE: w10278 ‐ Llys Marl, Marl Lane, Llandudno Junction
******** External Mail ******** Hi Sion, Thank you for your email.
9
In regards to the surface water connection, whilst we don’t have infiltration test results, we have recently received a survey (undertaken by Invek) of the sewers and highway drainage in Marl Lane. Please find a drainage layout and chamber details attached. The survey shows that there is a 300mm public surface water sewer (serving the Woodlands estate) and a 150mm private surface water sewer (which serves the recent Bryn Marl estate) in Marl Lane. Both sewers drain to the Afon Wydden. The highway drainage along Marl Lane is connecting to the 150mm private surface water sewer which discharges to the Afon Wydden. There are no land drainage features in this area. Given that nearby residential developments are drained to the Afon Wydden it would appear quite conclusive that soakaway drainage is not feasible in the area. However we understand that you will require this. Based on the above evidence, and in order for us to inform our Drainage Strategy which will support the planning application, please could you advise on a suitable discharge rate for a connection to the public surface water sewer (on the provision that infiltration testing will be provided and show that soakaways are not feasible). I attach greenfield runoff calculations based on FEH data for information. I look forward to hearing back from you. Kind Regards,
Aled Williams BSc (Hons) MCIWEM Senior Environmental Consultant 01824 702220
Ruthin - Chester - Manchester - Hyderabad Assessment, Modelling, Design
For email confidentiality, limitations and company details please see our disclaimer webpage. Registered in Wales under company no. 3577754. Waterco Ltd, Eden Court, Ruthin LL15 1NJ
From: Jones Sion [mailto:Sion.Jones@dwrcymru.com] Sent: Tuesday, March 21, 2017 5:39 PM To: Aled Williams Subject: RE: w10278 - Llys Marl, Marl Lane, Llandudno Junction Hi Aled, Thank you for your e‐mail and apologies for the delay in my reply, I was out of the office in North Wales for a number of days last week and playing catch up on e‐mails. The Hydraulic Modelling Report associated with the Woodlands / Llys Marl site in Llandudno Junction was before my time but, in respect of your query on the point of connection, I will discuss the matter with the preceding Development Control Officer for this area and the Modelling Team and report back to you at the earliest opportunity thereafter. In the meantime, with regards to your query regarding surface water, I would highlight that the results of infiltration testing will need to be provided upfront as an evidence base before the principle of a connection to the public surface water sewer can be agreed. Also, have you explored alternative land drainage features and/or highway drainage systems? On this point, are you also liaising with the Trunk Roads Agency? If all avenues are exhausted and
10
you are minded to connect into the surface water sewer line there would also be a need to ascertain that the line is functional and its size which I would suggest entail a CCTV survey. On receipt of all this information, I will review and report back on the principle of a connection and a suitable discharge rate accordingly which of course would be informed by your interaction with NRW regarding discharging further flows into the Afon Wydden. I appreciate this is a wealth of information, and may not be the response sought for, but would welcome any further evidence which you may wish to submit my way for further review. Regards, Siôn
Siôn Jones
Development Control Officer | Developer Services | Dwr Cymru Welsh Water
Linea | Cardiff | CF3 0LT | T: 0800 917 2652| www.dwrcymru.com
We will respond to your email as soon as possible but you should allow up to 10 working days to receive a response. For most of the services we offer we set out the timescales that we work to on our Developer Services section of our website. Just follow this link http://www.dwrcymru.com/en/Developer‐Services.aspx and select the service you require where you will find more information and guidance notes which should assist you. If you cannot find the information you are looking for then please call us on 0800 917 2652 as we can normally deal with any questions you have during the call. If we’ve gone the extra mile to provide you with excellent service, let us know. You can nominate an individual or team for a Diolch award through our website.
Before you print please think about the ENVIRONMENT
From: Aled Williams [mailto:Aled.Williams@waterco.co.uk] Sent: 15 March 2017 13:52 To: Jones Sion <Sion.Jones@dwrcymru.com> Subject: RE: w10278 ‐ Llys Marl, Marl Lane, Llandudno Junction
******** External Mail ******** Hi Sion, In relation to the Woodlands / Llys Marl site in Llandudno Junction and the attached associated Hydraulic Modelling Report (HMR), is there any movement on the point of connection to the combined sewer system suggested within the HMR? The HMR suggests a point of connection south‐east of the site within a verge adjacent to the roundabout on the A470. The preferred point of connection would be to the sewer in Marl Lane immediately south of the site i.e. where the proposed site access will be. In terms of commissioning any modelling updates, the client is currently exploring the potential of a localised scheme for surface water removal from the combined sewer. Should these investigations be inconclusive we will be in touch regarding modelling updates. I also look forward to hearing back from you in regards to a connection to the public surface water sewer as discussed in the below email chain. Kind Regards,
Aled Williams BSc (Hons) MCIWEM Senior Environmental Consultant 01824 702220
11
Ruthin - Chester - Manchester - Hyderabad Assessment, Modelling, Design
For email confidentiality, limitations and company details please see our disclaimer webpage. Registered in Wales under company no. 3577754. Waterco Ltd, Eden Court, Ruthin LL15 1NJ
From: Jones Sion [mailto:Sion.Jones@dwrcymru.com] Sent: Tuesday, February 28, 2017 4:46 PM To: Aled Williams Cc: Jones-Hughes Henry Subject: RE: w10278 - Llys Marl, Marl Lane, Llandudno Junction Good Afternoon Aled, Thank you for your e‐mail and apologies for the delay in my response. If you could keep me posted as and when you have been given confirmation from your client that would be appreciated. In the meantime, I will liaise with Henry in regards to the attached and respond via this in a separate e‐mail. I’m sorry I haven’t had a chance to review this but will take the opportunity to also liaise with my colleagues from network operations regarding the existing public surface water sewer and its capacity to accommodate a connection. I’ll report back on this in due course; please do not hesitate to contact me on the number below in the meantime. Regards, Siôn
Siôn Jones
Development Control Officer | Developer Services | Dwr Cymru Welsh Water
Linea | Cardiff | CF3 0LT | T: 0800 917 2652| www.dwrcymru.com
Before you print please think about the ENVIRONMENT
Developer Services have an on‐line service at www.dwrcymru.com. Here you can find all the services available, complete application forms and also make payments. If you have a quotation you can pay for this on‐line or alternatively by telephoning 0800 917 2652 using a credit/debit card. If we’ve gone the extra mile to provide you with excellent service, let us know. You can nominate an individual or team for a Diolch award through our website.
From: Aled Williams [mailto:Aled.Williams@waterco.co.uk] Sent: 21 February 2017 16:32 To: Jones Sion <Sion.Jones@dwrcymru.com> Cc: Jones‐Hughes Henry <Henry.Jones‐Hughes@dwrcymru.com> Subject: RE: w10278 ‐ Llys Marl, Marl Lane, Llandudno Junction
******** External Mail ******** Hi Sion, Thank you for this. We are awaiting client confirmation in regards to obtaining the modelling quote. Please can you advise when we can expect a response to the attached email. I believe Henry has passed this onto you.
12
Kind Regards,
Aled Williams BSc (Hons) MCIWEM Senior Environmental Consultant 01824 702220
Ruthin - Chester - Manchester - Hyderabad Assessment, Modelling, Design
For email confidentiality, limitations and company details please see our disclaimer webpage. Registered in Wales under company no. 3577754. Waterco Ltd, Eden Court, Ruthin LL15 1NJ
From: Jones Sion [mailto:Sion.Jones@dwrcymru.com] Sent: Tuesday, February 7, 2017 3:27 PM To: Aled Williams Cc: Jones-Hughes Henry Subject: RE: w10278 - Llys Marl, Marl Lane, Llandudno Junction Good Afternoon Aled, Following on from my e‐mail last week, I’ve been informed by our modelling team that the model would need to be re‐run in respect of the 54 proposed units and I’m advised that a fee of £250+VAT (£300.00) is required in order to obtain a detailed quotation to re‐run the modelling and develop any subsequent solutions. A payment can be made by phone or online (Ref: 6999999995) or alternatively, should you wish to pay for this fee via BACS, please see attached our bank details accordingly. Regards, Siôn
Siôn Jones
Development Control Officer | Developer Services | Dwr Cymru Welsh Water
Linea | Cardiff | CF3 0LT | T: 0800 917 2652| www.dwrcymru.com
Before you print please think about the ENVIRONMENT
Developer Services have an on‐line service at www.dwrcymru.com. Here you can find all the services available, complete application forms and also make payments. If you have a quotation you can pay for this on‐line or alternatively by telephoning 0800 917 2652 using a credit/debit card. If we’ve gone the extra mile to provide you with excellent service, let us know. You can nominate an individual or team for a Diolch award through our website.
From: Jones Sion Sent: 01 February 2017 09:39 To: Aled Williams <Aled.Williams@waterco.co.uk> Cc: Jones‐Hughes Henry <Henry.Jones‐Hughes@dwrcymru.com> Subject: RE: w10278 ‐ Llys Marl, Marl Lane, Llandudno Junction Good Morning Aled,
13
Following on from Henry’s e‐mail yesterday, I have been in contact with our modelling team and will report back shortly to confirm if any associated costs are required in order to re‐run the model. Regards, Siôn
Siôn Jones
Development Control Officer | Developer Services | Dwr Cymru Welsh Water
Linea | Cardiff | CF3 0LT | T: 0800 917 2652| www.dwrcymru.com
Before you print please think about the ENVIRONMENT
Developer Services have an on‐line service at www.dwrcymru.com. Here you can find all the services available, complete application forms and also make payments. If you have a quotation you can pay for this on‐line or alternatively by telephoning 0800 917 2652 using a credit/debit card. If we’ve gone the extra mile to provide you with excellent service, let us know. You can nominate an individual or team for a Diolch award through our website.
From: Jones‐Hughes Henry Sent: 31 January 2017 16:14 To: Aled Williams <Aled.Williams@waterco.co.uk> Cc: Jones Sion <Sion.Jones@dwrcymru.com> Subject: RE: w10278 ‐ Llys Marl, Marl Lane, Llandudno Junction Hi Aled Ive passed your email onto the development control officer for the Conwy area, Sion Jones. He will contact you in due course. Just a few points to mention on this one.
The modelling team may require a fee to re‐run the model if property numbers have changed. Sion will check this for you.
In terms of the surface water drainage, before we can consider a connection into the surface water sewer, it would have to be demonstrated that it would not be feasible to connect directly to a watercourse. We would also want to see that infiltration doesn’t work on‐site. I believe that the source of the watercourse on the other side of the road to the A470 is on the development side of this road.
Regards Henry
Henry Jones‐Hughes
Development Control Officer | Developer Services | Dwr Cymru Welsh Water
PO Box 3146 | Cardiff | CF30 0EH | T: 0800 9172652| F: 02920 740472 | Ext. 65813 If we’ve gone the extra mile to provide you with excellent service, let us know. You can nominate an individual or team for a Diolch award through our website
From: Aled Williams [mailto:Aled.Williams@waterco.co.uk] Sent: 31 January 2017 15:54 To: Jones‐Hughes Henry <Henry.Jones‐Hughes@dwrcymru.com> Subject: w10278 ‐ Llys Marl, Marl Lane, Llandudno Junction
******** External Mail ******** Proposed residential development at Llys Marl, Marl Lane, Llandudno Junction.
14
Good afternoon Henry, DCWW have previously been contacted regarding the above site (also known as Woodlands) and a hydraulic modelling assessment was undertaken in August 2015. Foul flows The HMR gives solutions to resolve the detriment caused by the development. The favoured solution includes online storage by replacing two existing manholes with two 2.4m diameter manholes (providing 16m³ of storage) along with upsizing existing storage at the Marl Drive CSO by 11m³. Following the completion of the HMR the development proposals have changed with 54 dwellings proposed, rather than the 70 assessed in the HMA. Please find a layout plan attached. Based on the values given in the HMR (2.6 people per household and 180 litres per head per day) the reduction in dwellings could lead to a 7.49m³ reduction in foul flows over one day. Please advise if the reduction in foul flows has potential to reduce the required mitigating volumes, especially at the CSO (given the potential third party land issues identified with providing 11m³ at the CSO). We understand that this may need to be evidenced through additional modelling, therefore please advise on the associated costs if necessary. Surface water The site is separated from the nearest watercourse (the Afon Wydden) by the A470. In order to make a connection to this watercourse, and to avoid making a new connection crossing under the A470, please advise if we can make a connection to the public surface water sewer in Marl Lane, south of the site. Discharge would be at a greenfield rate of 5 l/s and only required should soakaways not be feasible. Please don’t hesitate to contact me if you have any questions. Kind Regards,
Aled Williams BSc (Hons) MCIWEM Senior Environmental Consultant 01824 702220
Ruthin - Chester - Manchester - Hyderabad Assessment, Modelling, Design
For email confidentiality, limitations and company details please see our disclaimer webpage. Registered in Wales under company no. 3577754. Waterco Ltd, Eden Court, Ruthin LL15 1NJ
Llys Marl, Llandudno Junction FCA & Drainage Strategy
w10278-170518-FCA and Drainage Strategy
Appendix D – Proposed Layout Plan
01
A4
ME
TER S
GSVP
rwp
rwp
SVP
G
SP
WP
rwp
rwp
MET ERS
GSVP
rwp
rwp
rwp
rwp
SVP
G
SP
P3
DQ3 DQ3
GA
RA
GE
GA
RA
GE
SELFCLOSING
GATEBOW TOP RAILINGS
LITTER BIN AND
SEATING
LITTER BIN AND
SEATING
CALG
AR
Y M
OD
ULA
R TO
WER
CITY JUNIOR SWING
ELE
PHA
NT
SPR
ING
ER
CH
ICKE
N
SPR
ING
ER
EQ
UIP
PE
D P
LAY
SPA
CE
SELFCLOSING
GATE
0402 03
METERS
G
SVP
rwp
rwp
rwp
rwp
SVP
G
SP
P3
GA
RA
GE
F2
ME
TERS
SVP
G
rwp
rwp
SVP
G
rwp
ME
TERS
rwp
G
G
rwp
EFEFF2
A4
MET ERS
G
SVP
rwp
rwp
SVP
G
SP
WP
rwp
rwp
G3
1212A 14
15 16 1718/19
GA
RA
GE
H3
SVP
G
METERS
rwp
SVPMETE
RS
SHOWER
SHOWER
rwp
rwp
rwp
G
EF
EF
32
48
45
50
46
44
4043
28
35
30
WO
OD
LAND
S
WO
OD
LAND
S
17
24
1412
27
35 to 43
34
MARL LANE
20
StaPpg
EXISTING RIG
HT OF W
AY SHOW
N
IN B
LACK
LP
LP
LP
LP
IC
A
Z
B
279550E
279600E
279650E
2279700E
10.91
11.09
11.34
11.62
12.26
12.7012.81
13.1413.23
13.5013.60
13.99
14.1714.26
14.41
14.71
15.05
15.46
15.87
15.93
16.13
16.31
16.64
17.03
17 06
17.15
16.7516 69
16 35
16.44
16.08
15.69
15.80
15 73
15 27
15.18
14.78
14.88
14 85
14.3814.28
14.39
14.0513.97
13.89
13.41
13.51
14.08
13.73
13.89
13.02
13.13
12.49 12.6012.28
12.19
12.17
12.02
12.02
11.82
11.92
11.70
11.8211.58
11.46
11.26
11.39
11.11
11.2311.04
11.76
12.14
12.14
11.83
12.19
12.78
13.45
14.04
14.36
14.71
15.04
15.51
16.17
16.42
16.69
17.07
17.32
16.97
16.54
16.02
15.99
15.33
15.09
14.62
14.11
13.01
13.45
15 00
14 63
14.28
13.54
13 00
11 84
11 42
11 2011 06
10 94
26.54
22.65
10
12.53
11.44
12.14 12
.0012
.11 11.
86
11.97
11.56
11.66
11.3911
.49
11.201
1.0510.92
10.83
10.74
10.84
10.24
10.63
11.53
12.06
12.69
12.80
12.90
12.75 12 76
10.95
11.1511.19
10.91
11 60
11 9511 77
11 95
11 91
12.85
12.28
11.70
11.43
11.07
10.90
11.27
10.83
10.87
10.92
10.87
10.59
10.43
10.25
10.13
10.09
10 71
10.06
10.88
10.91
10.26
10.22
10.95
11.00
10.66
10.45
11.23
11.24
10.97
10.93
11.23
11.41
11.42
11.53
11.36
11.07
11.21
11.37
11.69
11.72
10.04
10.01
9.92
9.88
9.81
9.81
9.97
9.97
10.12
14.6415.75
23.00
22.65
21.93
15.40
15.02
14.91
14.72
14.61
14.61
14.48
14.36
14.33
13.70
11.96
11.49
11.28
11.06
10.94
10.71
10.57
10.38
10.37
10.45
10.30
10.45
10.23
10.21
10.06
9.98
10.27
10.56
23.77
26.53
26.28
26.93
28.87
29.11
29.97
30.49
31.02
31.89
27.46
26.92
23.36
27.64
12.59
13.09
11.45
11.39
12.99 10.76
21.71 20.06 17.56
23.71
21.55
20.86
19.90
19.07
18.48
17.88
17.19
16.21
15.83
15.76
15.77
FH
NP
NP
SV
RS
SIGN
BOX
BIN
RIDGE
EAVES
NP
RS/LP
RS
MKR
1.8
WPR 1.4MH2 x MKRS
RIDGE
RIDGE
RIDGE
RIDGE
RIDGE
RIDGE
RIDGE
RIDGE
RIDGE
RIDGE
EAVES
EAVES
EAVES
RIDGE
KTA
FRENCHGRA
TREES
HEDGE/ BOTTOM OF BANK
GRASS
K
DK
K K
TARMAC
TREES/ HEDGE
GRASS
IC CL
UTLG
K
IC CL
UTL
GIC CL
UTL
MARL DRIVE
DK
TAR
TAR
LONG GRASS
O/H CANO
PY
O/H CANOPY
O/H CANOPY
WPR 1.4MH
GRASS
GRASS TAR
WOODLAND/ DENSE OVERGROWTH
WOODLAND/ DENSE OVERGROWTH
WOODLAND/ DENSE OVERGROWTH
WOODLAND/ DENSE OVERGROWTH
KERB LINE SHOWN FOR ILLUSTRATIVE PURPOSES ONLY
IC CL
UTL
DK
K
K
UTL
G
IC CL
IC CL
IC CL
IC CL
ICs UTL
IC CL UTL
K
FOOTPATH
FOOTPATH
FOOTPATH
KISSING GATE
KISSING GATE
WALL
SIGN
INACCESSIBLEFOOTPATH
FOOTPATH
INACCESSIBLE
TREE CANOPY/ OVERGROWTH
TOP OF GRASS BANK
WOODLAND
WPR 1.4MH
GRASS
G
A470
TO LLANDUDNO
TREE
O/H CANOPY
POST AND WIRE 1.
2MH
CHAIN LINK 1.4MH
GARDENS
LONG GRASS
FENCE DILAP.
FENCE DILAP.
11.00
11.00
11.00
15.00
15.00
15.00
17.00
17.00
17.00
16.00
16.00
16.00
22.00
12.00
12.00
12.00
14.00
14.00
14.00
13.00
13.00
13.00
18.00
18.00
21.00
20.00
19.00
19.00
10.00
DK
GIVE WAY
RS
LONG
Z
SECTION 1
SECTION 2
SECTION 3
SE
CT
ION
1
2.4 X 90m
2.4 X 90m
A4METERS
G
SVP
rwp
rwp
SVP
G
SP
WP
rwp
rwp
P3GARAGE
40
GARAGE
F3
A4METERS
G
SVP
rwp
rwp
SVP
G
SP
WP
rwp
rwp
36
GARAGE
GARAGE
A3 A3
D2H
F3
F3
rwp
rwp SV
P
G
METERS
rwp
SVP
G
METERS
rwp
rwp
EF
EF
N3
N3
46 47 48 49 51/52
H3
GA
RA
GE
GARAGE 35H3
GARAG
E
34
MET
ERS
G
SVP
rwp
rwp
SVP
G
SP
WP
rwp
rwp
DQ2*
ME
T ERS
ME
T ERS
METERS
SVP
rwp
SVP
G rwp G
rwp
rwp
ME
T ERS
rwp
METERS
rwp
A3 A3
N3N3
H3
GA
RA
GE
SVP
rwp
SVP
Grwp
ME
TERS
G
rwp
rwp
ME
TERS
rwp
rwp
A3A3
METERS
rwp
SVP
Grwp
rwp
rwp
EF
G
H3
GA
RA
GE
ME
TERS
rwp
SVP
G
rwp
rwp
rwp
EF
G
H3
GA
RA
GE
METERS
rwp
SVP
G
rwp
rwp
rwp
EF
G
TACTILEPAVING
2.4
X 2
4m V
ISIB
ILIT
Y S
PLA
Y
2.4
X 3
3m V
ISIB
ILIT
Y S
PLA
Y
TACTILEPAVING
TACTILEPAVING
TACTILEPAVING
TACTILEPAVING
TACTILEPAVING
PUBLIC OPENSPACE
F3 F3
rwp
rwp
SVP
G
ME
TERS
rwp
SVPG
ME
T ER S
rwp
rwp
EFEF
0506
0708091011
METERS
rwp
SVP
G rwp
rwprwp
EF
G
2.4
X 3
3m
VIS
IBIL
ITY
SP
LA
Y
2.4
X 3
3m V
ISIB
ILIT
Y SP
LAY
Aco
Dra
in
RE
MO
VA
BL
ER
EF
LE
CT
IVE
BO
LL
AR
DS
GA
RA
GE
**
*
*
*
*
METERS
rwp
SVP
Grwp
rwp
rwp
EF
G
rwp
rwp
SVP
G
METERS
rwp
SVPG
MET
ERS
rwp
rwp
EF
EF
METERS
rwp
SVP
G
rwp
rwp
rwp
EF
G
F3
METERS
rwp
SVP
G
rwp
rwp
rwp
EF
G
METERS
G
SVP
rwp
rwprw
p
rwp
SVP
G
SP
F2METERS
SVP
G
rwp
rwp
SVP
G
rwp
METERS
rwp
G
G
rwp
EF
EF
F2
G3
G3G3
N3 N3
A4
GA
RA
GE
SVPSVP
G
rwp
rwp
METERS
SVP
ME
TERS
ME
TERS
G
METERSrwp
rwp
rwp
WP
SVP
rwp
SVP
G rwp
G
rwp
rwp
ME
TERS
rwp
rwp
METERS
11
12
12A
16
17
11
08
09
2.4
X 2
5m
VIS
IBIL
ITY
SP
LA
Y
2.4
X 3
3m
VIS
IBIL
ITY
SP
LA
Y
19
19
A3
202122232425
50
METERS
rwp
S VP
Grw
p
rwp
rwp
EF
G
METERS
rwp
SVP
G
rwp
rwp
rwp
EF
G
H3
GARAGE
GARAGE
METERS
GSVP
rwp
rwp
rwp
rwp
SVP
G
SP
GARAGEMETERS
rwp
SVP
G
rwp
rwp
rwp
EF
G
H3
41
42
43
44
45
39
38
H3
P3
37
33
H3
32
31302928
2726
Aco Drain
RE
MO
VA
BL
ER
EF
LE
CT
IVE
BO
LL
AR
DS
Aco Drain
REMOVABLE
REFLECTIVE
BOLLARDS
35.200
110m
34.750
14.580
14.790
15.125
15.250
15.375
15.500
15.625
15.750
15.875
16.000
16.125
16.250
16.375
16.500
17.088
17.676
18.85218.264
19.440
20.028
20.420
15.000
14.00
16.28416:150
16.57016:150
16.344
14.00
16.630
16.50
1 IN 17
16.90
17.30
17.1
5
16.75
16.35
1 IN
48
1 IN
80
18.000
15.95516.45516.95517.21817.481
17.7441 IN 20
1 IN 38
18.20
17.90
17.55
17.05
17.05
16.90
17.00
16.60
15.90
15.312
15.562
15.700
15.062
16.00
15.8015.60
15.40
15.600
15.193
14.971
14.749
14.527 14.305 14.083
14.5015.10
1 IN 45
beechdevelopments
LLYS MARL
DQ 2 APARTMENT
D APARTMENTS
F2 HOUSEF3 HOUSE
A3 HOUSES
H3 HOUSES
2 No
2 No
4 No6 No
7 No
10 No
TOTAL 52 No
SITE CONCEPT PLAN
Scale : 1:500 @ A2MARCH 2016
DRAWING TITLE
DRAWING NO REVISIONBD/LM/ PL1
PLANNING LAYOUT
~
LLYS MARLLLANDUDNO JUNCTION
P3 HOUSEA4 HOUSES
4 No5 No
N3 HOUSE 6 No
DQR 3 BED HOUSE 2 No
G3 HOUSE 4 No
Llys Marl, Llandudno Junction FCA & Drainage Strategy
w10278-170518-FCA and Drainage Strategy
Appendix E – Flood Maps & NRW Correspondence
DATE:31/01/2017
PLOT NAME:w10278-TAN15_FloodMap
REV:-
DRAWN:RCL
CHECKED:AW
APPROVED:VG
PLOT SCALE @ A3:
(UNLESS STATED OTHERWISE)1:5,000
PLOT STATUS:FINAL
PLOT TITLE:
WELSH GOVERNMENTDEVELOPMENT ADVICE MAP
SCHEME:
LLYS MARL,LLANDUDNO JUNCTION
CLIENT:
BEECH DEVELOPMENTS (NW) LTD
LEGENDSite BoundaryZone BZone C1Zone C2
0 100 200 300 400 50050m
JANUARY 2017
NOTES:1) ALL DIMENSIONS ARE IN METRES AND ALL LEVELS IN METRESABOVE ORDNANCE DATUM UNLESS STATED OTHERWISE±
CONTAINS OS DATA © CROWN COPYRIGHT (2017)WG TAN 15 DEVELOPMENT AND FLOOD RISK DEVELOPMENT ADVICE MAP DOWNLOADED FROM THE LLE GEO-PORTAL
Waterco LtdEden Court, Ruthin, LL15 1NJ
01824 702220www.waterco.co.uk
DATE:23/03/2017
PLOT NAME:w10278-NRW_FloodMap
REV:-
DRAWN:RCL
CHECKED:AW
APPROVED:VG
PLOT SCALE @ A3:
(UNLESS STATED OTHERWISE)1:5,000
PLOT STATUS:FINAL
PLOT TITLE:
NRW FLOOD MAP FOR PLANNING
SCHEME:
LLYS MARL,LLANDUDNO JUNCTION
CLIENT:
BEECH DEVELOPMENTS (NW) LTD
LEGENDSite BoundaryNRW Flood DefencesAreas Benefitting from DefencesNRW Flood Zone 2NRW Flood Zone 3
0 100 200 300 400 50050m
JANUARY 2017
NOTES:1) ALL DIMENSIONS ARE IN METRES AND ALL LEVELS IN METRESABOVE ORDNANCE DATUM UNLESS STATED OTHERWISE±
CONTAINS NATURAL RESOURCES WALES INFORMATION © NATURAL RESOURCES WALES AND DATABASE RIGHT. ALL RIGHTS RESERVED. SOME FEATURES OF THIS INFORMATION ARE BASED ON DIGITAL SPATIAL DATA LICENCED FROM THE CENTRE FOR ECOLOGY AND HYDROLOGY © NERC (CEH). DEFRA, MET OFFICE AND DARDRIVERS AGENCY © CROWN COPYRIGHT. © CRANFIELD UNIVERSITY. © JAMES HUTTON INSTITUTE. CONTAINS OS DATA © CROWN COPYRIGHT AND DATABASE RIGHT 2015. LAND AND PROPERTY SERVICES © CROWN COPYRIGHT AND DATABASE RIGHT. CONTAINS OS DATA © CROWN COPYRIGHT (2017)
Waterco LtdEden Court, Ruthin, LL15 1NJ
01824 702220www.waterco.co.uk
18
1614
12
20
10
22
24
8
26
1010
10
12
8
0 50 10025m
PLOT SCALE @ A3: 1:1,500
DATE:17/05/2017
PLOT NAME:w10278-NRW_SW
REV:-
DRAWN:IJ
CHECKED:AW
APPROVED:VG
PLOT SCALE @ A3:
(UNLESS STATED OTHERWISE)1:5,000
PLOT STATUS:DRAFT / FINAL
PLOT TITLE:
SCHEME:
LLYS MARL,LLANDUDNO JUNCTION
CLIENT:
BEECH DEVELOPMENTS (NW) LTD
LEGENDSite BoundaryHigh Risk (3.33% AEP Event)Medium Risk (1.0% AEP Event)Low Risk (0.1% AEP Event)
0 100 200 300 400 50050m
NOTES:1) ALL DIMENSIONS ARE IN METRES AND ALL LEVELS IN METRESABOVE ORDNANCE DATUM UNLESS STATED OTHERWISE±
NRW FLOOD MAP FORSURFACE WATER
MAY 2017
www.waterco.co.uk
CONTAINS NATURAL RESOURCES WALES INFORMATION © NATURAL RESOURCES WALES AND DATABASE RIGHT. ALL RIGHTS RESERVED. SOME FEATURES OF THIS INFORMATION ARE BASED ON DIGITAL SPATIAL DATA LICENCED FROM THE CENTRE FOR ECOLOGY AND HYDROLOGY © NERC (CEH). DEFRA, MET OFFICE AND DARDRIVERS AGENCY © CROWN COPYRIGHT. © CRANFIELD UNIVERSITY. © JAMES HUTTON INSTITUTE. CONTAINS OS DATA © CROWN COPYRIGHT AND DATABASE RIGHT 2015. LAND AND PROPERTY SERVICES © CROWN COPYRIGHT AND DATABASE RIGHT. CONTAINS OS DATA © CROWN COPYRIGHT (2017)
Ceir rhestr lawn o delerau ac amondau yn https://naturalresources.wales/rhybuddsafonol neu drwy gysylltu ag ymholiada@cyfoethnaturiolcymru.gov.uk. A full list of terms and condiitions is available from the https://naturalresources.wales/StandardNotice or by contacting enquire@naturalresourceswales.gov.uk © Crown copyright and database rights 2017 Ordnance Survey 100019741. Geological Mapping: British Geological Survey ©NERC. Centre for Ecology & Hydrology © NERC (CEH). Defra and Met Office © Crown copyright. © Cranfield University. © James Hutton Institute. Land & Property Services © Crown copyright and database right.
1:
17/05/2017
Dyddiad / Date
Reservoirs
5,001
Map Perygl Llifogydd / Flood Risk Map
Graddfa / Scale
0.13
Kilometers
0.3
British_National_Grid
00.3
Allwedd / Map Key
Reservoir Depths
0 - 0.3m
0.3 - 2.0m
Greater than 2.0m
Tŷ Cambria 29 Heol Casnewydd Caerdydd CF24 0TP
Cambria House 29 Newport Road Cardiff CF24 0TP Croesewir gohebiaeth yn y Gymraeg a’r Saesneg Correspondence welcomed in Welsh and English
23/03/2017 Dear Aled Williams, PROPOSAL: Scheme for the removal of highway drainage (surface water runoff) from
the public combined sewer system LOCATION: Along Marl Lane, Llandudno Junction Thank you for consulting Natural Resources Wales about the above proposed development at pre-application stage. This response is to the enquiry regarding advice specifically on flood risk. Please note that our comments are without prejudice to any comments we may wish to make when consulted on any subsequent planning application or permit (either at pre-application or application stage) for the proposed development. At that time there may be new information available which we will need to take into account in making a formal response. Flood Risk As you may be aware the area suffered from a significant flood event in June 1993. Following the event our predecessors carried out a flood alleviation scheme for the main river (Afon Wydden) in Llandudno Junction. Although the scheme at the time was designed to provide a certain standard of protection it is highly likely that the standard today would have been reduced. We would expect Welsh Water to demonstrate that any new direct outfalls to the watercourse will not increase flood risk from the river Wydden for a range of annual exceedance probability events. We are at an early stage of developing a hydraulic model for the Wydden which will include various input points; unfortunately we cannot provide a date as to when the model would be available. Due to the status of the watercourse, any new structures/outfalls into the watercourse will be subject to Flood Risk Activity Permit as per the Environmental Permitting Regulations 2016. The existing outfall from the area discharges upstream of the Meadows estate and the BT flood storage area. Should you wish to discuss the above, please contact Iwan on 03000 653783/ iwan.huws@cyfoethnaturiol.cymru Please do not hesitate to contact us if we can be of any further assistance to you. Our comments above only relate specifically to matters related to your enquiry, i.e. the flood risk aspects of your proposal. We have not considered potential effects of other matters in relation to our remit that we may have concerns with, when providing our response to the local planning authority. “Natural Resources Wales and Planning Consultations” (March 2015) which is published
Ein cyf/Our ref: CAS-30433-W2Z9
Ebost/Email: northplanning@cyfoethnaturiolcymru.gov.uk Ffôn/Phone: 03000 65 4682
www.naturalresourceswales.gov.uk www.cyfoethnaturiolcymru.gov.uk Page 2 of 2
on our website: (https://naturalresources.wales/planning-and-development includes a checklist of areas where we will provide comment. You should also be advised that, in addition to planning permission, it is your responsibility to ensure that you secure all other permits/consents relevant to your development. Yn gywir / yours faithfully
Siôn M Williams Siôn M. Williams
Ymgynghorydd Cynllunio Datblygu / Development Planning Advisor
Cyfoeth Naturiol Cymru / Natural Resources Wales
Llys Marl, Llandudno Junction FCA & Drainage Strategy
w10278-170518-FCA and Drainage Strategy
Appendix F – MicroDrainage Runoff and Volume Estimates
Waterco Ltd Page 1Eden Court w10278 - Marl LaneLon Parcwr Business Park Llanduno JunctionDenbighshire LL15 1NJ Greenfield RunoffDate 31-01-2017 09:54 Designed by Johanne.WilliamsFile Checked by Aled WilliamsXP Solutions Source Control 2016.1
FEH Mean Annual Flood
©1982-2016 XP Solutions
Input
Site Location SAAR (mm) 782 SPRHOST 32.300 FARL 1.000Area (ha) 1.913 URBEXT (1990) 0.0000 BFIHOST 0.519
Results
QMED Rural (l/s) 3.9 QMED Urban (l/s) 3.9
Waterco Ltd Page 1
Eden Court w10278
Lon Parcwr Business Park LLys Marl
Denbighshire LL15 1NJ Llandudno Jct
Date 17/05/17 Designed by SJP
File 1 in 30 year.srcx Checked by AW
XP Solutions Source Control 2016.1
Summary of Results for 30 year Return Period
©1982-2016 XP Solutions
Storm
Event
Max
Level
(m)
Max
Depth
(m)
Max
Control
(l/s)
Max
Volume
(m³)
Status
15 min Summer 9.485 0.485 5.0 108.7 O K30 min Summer 9.580 0.580 5.0 129.9 O K60 min Summer 9.684 0.684 5.0 153.2 O K120 min Summer 9.782 0.782 5.0 175.3 Flood Risk180 min Summer 9.828 0.828 5.0 185.6 Flood Risk240 min Summer 9.850 0.850 5.0 190.5 Flood Risk360 min Summer 9.860 0.860 5.0 192.7 Flood Risk480 min Summer 9.858 0.858 5.0 192.2 Flood Risk600 min Summer 9.851 0.851 5.0 190.6 Flood Risk720 min Summer 9.841 0.841 5.0 188.4 Flood Risk960 min Summer 9.830 0.830 5.0 186.0 Flood Risk1440 min Summer 9.793 0.793 5.0 177.7 Flood Risk2160 min Summer 9.722 0.722 5.0 161.7 Flood Risk2880 min Summer 9.634 0.634 5.0 142.1 O K4320 min Summer 9.397 0.397 5.0 89.0 O K5760 min Summer 9.258 0.258 5.0 57.8 O K7200 min Summer 9.178 0.178 4.8 39.9 O K8640 min Summer 9.134 0.134 4.5 30.0 O K10080 min Summer 9.114 0.114 4.2 25.6 O K
15 min Winter 9.546 0.546 5.0 122.3 O K30 min Winter 9.655 0.655 5.0 146.6 O K
Storm
Event
Rain
(mm/hr)
Flooded
Volume
(m³)
Discharge
Volume
(m³)
Time-Peak
(mins)
15 min Summer 78.390 0.0 113.8 2630 min Summer 47.441 0.0 137.6 4060 min Summer 28.711 0.0 166.8 68120 min Summer 17.376 0.0 201.9 126180 min Summer 12.953 0.0 225.8 184240 min Summer 10.516 0.0 244.4 242360 min Summer 7.839 0.0 273.3 330480 min Summer 6.364 0.0 295.8 390600 min Summer 5.414 0.0 314.6 456720 min Summer 4.744 0.0 330.8 522960 min Summer 3.901 0.0 362.6 6621440 min Summer 2.960 0.0 412.8 9442160 min Summer 2.246 0.0 469.9 13642880 min Summer 1.847 0.0 515.2 17684320 min Summer 1.340 0.0 560.8 24645760 min Summer 1.068 0.0 595.7 31207200 min Summer 0.895 0.0 624.2 37608640 min Summer 0.775 0.0 648.5 441610080 min Summer 0.686 0.0 669.8 5144
15 min Winter 78.390 0.0 127.4 2630 min Winter 47.441 0.0 154.1 40
Waterco Ltd Page 2
Eden Court w10278
Lon Parcwr Business Park LLys Marl
Denbighshire LL15 1NJ Llandudno Jct
Date 17/05/17 Designed by SJP
File 1 in 30 year.srcx Checked by AW
XP Solutions Source Control 2016.1
Summary of Results for 30 year Return Period
©1982-2016 XP Solutions
Storm
Event
Max
Level
(m)
Max
Depth
(m)
Max
Control
(l/s)
Max
Volume
(m³)
Status
60 min Winter 9.772 0.772 5.0 172.9 Flood Risk120 min Winter 9.887 0.887 5.0 198.7 Flood Risk180 min Winter 9.944 0.944 5.0 211.5 Flood Risk240 min Winter 9.975 0.975 5.0 218.3 Flood Risk360 min Winter 9.995 0.995 5.0 222.8 Flood Risk480 min Winter 9.988 0.988 5.0 221.2 Flood Risk600 min Winter 9.977 0.977 5.0 219.0 Flood Risk720 min Winter 9.963 0.963 5.0 215.8 Flood Risk960 min Winter 9.942 0.942 5.0 211.0 Flood Risk1440 min Winter 9.874 0.874 5.0 195.8 Flood Risk2160 min Winter 9.750 0.750 5.0 167.9 Flood Risk2880 min Winter 9.587 0.587 5.0 131.4 O K4320 min Winter 9.273 0.273 5.0 61.3 O K5760 min Winter 9.145 0.145 4.6 32.4 O K7200 min Winter 9.108 0.108 4.0 24.3 O K8640 min Winter 9.094 0.094 3.5 21.0 O K10080 min Winter 9.084 0.084 3.1 18.8 O K
Storm
Event
Rain
(mm/hr)
Flooded
Volume
(m³)
Discharge
Volume
(m³)
Time-Peak
(mins)
60 min Winter 28.711 0.0 186.8 68120 min Winter 17.376 0.0 226.1 124180 min Winter 12.953 0.0 252.9 180240 min Winter 10.516 0.0 273.7 238360 min Winter 7.839 0.0 306.1 346480 min Winter 6.364 0.0 331.3 442600 min Winter 5.414 0.0 352.3 478720 min Winter 4.744 0.0 370.5 556960 min Winter 3.901 0.0 406.2 7121440 min Winter 2.960 0.0 462.2 10222160 min Winter 2.246 0.0 526.3 14722880 min Winter 1.847 0.0 577.0 18804320 min Winter 1.340 0.0 628.3 25085760 min Winter 1.068 0.0 667.2 31047200 min Winter 0.895 0.0 699.1 36808640 min Winter 0.775 0.0 726.3 440810080 min Winter 0.686 0.0 750.2 5136
Waterco Ltd Page 3
Eden Court w10278
Lon Parcwr Business Park LLys Marl
Denbighshire LL15 1NJ Llandudno Jct
Date 17/05/17 Designed by SJP
File 1 in 30 year.srcx Checked by AW
XP Solutions Source Control 2016.1
Rainfall Details
©1982-2016 XP Solutions
Rainfall Model FEH D3 (1km) 0.311 Cv (Winter) 0.840Return Period (years) 30 E (1km) 0.300 Shortest Storm (mins) 15
Site Location F (1km) 2.342 Longest Storm (mins) 10080C (1km) -0.030 Summer Storms Yes Climate Change % +0D1 (1km) 0.377 Winter Storms YesD2 (1km) 0.421 Cv (Summer) 0.750
Time Area Diagram
Total Area (ha) 0.775
Time
From:
(mins)
To:
Area
(ha)
Time
From:
(mins)
To:
Area
(ha)
Time
From:
(mins)
To:
Area
(ha)
0 4 0.258 4 8 0.258 8 12 0.258
Waterco Ltd Page 4
Eden Court w10278
Lon Parcwr Business Park LLys Marl
Denbighshire LL15 1NJ Llandudno Jct
Date 17/05/17 Designed by SJP
File 1 in 30 year.srcx Checked by AW
XP Solutions Source Control 2016.1
Model Details
©1982-2016 XP Solutions
Storage is Online Cover Level (m) 10.000
Tank or Pond Structure
Invert Level (m) 9.000
Depth (m) Area (m²) Depth (m) Area (m²)
0.000 224.0 1.000 224.0
Hydro-Brake Optimum® Outflow Control
Unit Reference MD-SHE-0105-5000-1000-5000Design Head (m) 1.000
Design Flow (l/s) 5.0Flush-Flo™ CalculatedObjective Minimise upstream storage
Application SurfaceSump Available YesDiameter (mm) 105
Invert Level (m) 8.995Minimum Outlet Pipe Diameter (mm) 150Suggested Manhole Diameter (mm) 1200
Control Points Head (m) Flow (l/s)
Design Point (Calculated) 1.000 5.0Flush-Flo™ 0.296 5.0Kick-Flo® 0.637 4.1
Mean Flow over Head Range - 4.3
The hydrological calculations have been based on the Head/Discharge relationship for theHydro-Brake Optimum® as specified. Should another type of control device other than aHydro-Brake Optimum® be utilised then these storage routing calculations will beinvalidated
Depth (m) Flow (l/s) Depth (m) Flow (l/s) Depth (m) Flow (l/s) Depth (m) Flow (l/s)
0.100 3.6 1.200 5.4 3.000 8.4 7.000 12.50.200 4.8 1.400 5.8 3.500 9.0 7.500 12.90.300 5.0 1.600 6.2 4.000 9.6 8.000 13.30.400 4.9 1.800 6.6 4.500 10.1 8.500 13.70.500 4.7 2.000 6.9 5.000 10.6 9.000 14.10.600 4.3 2.200 7.2 5.500 11.1 9.500 14.50.800 4.5 2.400 7.5 6.000 11.61.000 5.0 2.600 7.8 6.500 12.1
Waterco Ltd Page 5
Eden Court w10278
Lon Parcwr Business Park LLys Marl
Denbighshire LL15 1NJ Llandudno Jct
Date 17/05/17 Designed by SJP
File 1 in 30 year.srcx Checked by AW
XP Solutions Source Control 2016.1
Event: 240 min Winter
©1982-2016 XP Solutions
Waterco Ltd Page 6
Eden Court w10278
Lon Parcwr Business Park LLys Marl
Denbighshire LL15 1NJ Llandudno Jct
Date 17/05/17 Designed by SJP
File 1 in 30 year.srcx Checked by AW
XP Solutions Source Control 2016.1
Event: 360 min Winter
©1982-2016 XP Solutions
Waterco Ltd Page 7
Eden Court w10278
Lon Parcwr Business Park LLys Marl
Denbighshire LL15 1NJ Llandudno Jct
Date 17/05/17 Designed by SJP
File 1 in 30 year.srcx Checked by AW
XP Solutions Source Control 2016.1
Event: 480 min Winter
©1982-2016 XP Solutions
Waterco Ltd Page 1
Eden Court w10278
Lon Parcwr Business Park LLys Marl
Denbighshire LL15 1NJ Llandudno Jct
Date 17/05/17 Designed by SJP
File 1 in 100 year +30%CC.srcx Checked by AW
XP Solutions Source Control 2016.1
Summary of Results for 100 year Return Period (+30%)
©1982-2016 XP Solutions
Storm
Event
Max
Level
(m)
Max
Depth
(m)
Max
Control
(l/s)
Max
Volume
(m³)
Status
15 min Summer 9.467 0.467 5.0 219.0 O K30 min Summer 9.547 0.547 5.0 256.6 O K60 min Summer 9.637 0.637 5.0 298.6 O K120 min Summer 9.730 0.730 5.0 342.3 Flood Risk180 min Summer 9.782 0.782 5.0 366.6 Flood Risk240 min Summer 9.814 0.814 5.0 381.9 Flood Risk360 min Summer 9.850 0.850 5.0 398.7 Flood Risk480 min Summer 9.864 0.864 5.0 405.3 Flood Risk600 min Summer 9.866 0.866 5.0 406.1 Flood Risk720 min Summer 9.861 0.861 5.0 403.9 Flood Risk960 min Summer 9.862 0.862 5.0 404.4 Flood Risk1440 min Summer 9.851 0.851 5.0 399.0 Flood Risk2160 min Summer 9.819 0.819 5.0 383.9 Flood Risk2880 min Summer 9.780 0.780 5.0 365.6 Flood Risk4320 min Summer 9.635 0.635 5.0 298.0 O K5760 min Summer 9.489 0.489 5.0 229.1 O K7200 min Summer 9.379 0.379 5.0 178.0 O K8640 min Summer 9.296 0.296 5.0 138.8 O K10080 min Summer 9.235 0.235 4.9 110.1 O K
15 min Winter 9.524 0.524 5.0 245.9 O K30 min Winter 9.615 0.615 5.0 288.5 O K
Storm
Event
Rain
(mm/hr)
Flooded
Volume
(m³)
Discharge
Volume
(m³)
Time-Peak
(mins)
15 min Summer 154.375 0.0 219.4 2630 min Summer 91.094 0.0 258.4 4160 min Summer 53.754 0.0 311.6 70120 min Summer 31.719 0.0 367.5 128180 min Summer 23.298 0.0 404.6 188240 min Summer 18.717 0.0 433.2 246360 min Summer 13.748 0.0 476.9 364480 min Summer 11.045 0.0 510.4 482600 min Summer 9.320 0.0 537.9 600720 min Summer 8.112 0.0 561.3 674960 min Summer 6.600 0.0 607.2 7901440 min Summer 4.935 0.0 672.6 10482160 min Summer 3.690 0.0 771.9 14722880 min Summer 3.002 0.0 837.2 18844320 min Summer 2.147 0.0 896.8 27285760 min Summer 1.692 0.0 944.1 34087200 min Summer 1.407 0.0 981.3 41128640 min Summer 1.210 0.0 1012.8 476010080 min Summer 1.065 0.0 1039.3 5448
15 min Winter 154.375 0.0 245.5 2630 min Winter 91.094 0.0 288.5 41
Waterco Ltd Page 2
Eden Court w10278
Lon Parcwr Business Park LLys Marl
Denbighshire LL15 1NJ Llandudno Jct
Date 17/05/17 Designed by SJP
File 1 in 100 year +30%CC.srcx Checked by AW
XP Solutions Source Control 2016.1
Summary of Results for 100 year Return Period (+30%)
©1982-2016 XP Solutions
Storm
Event
Max
Level
(m)
Max
Depth
(m)
Max
Control
(l/s)
Max
Volume
(m³)
Status
60 min Winter 9.716 0.716 5.0 335.9 Flood Risk120 min Winter 9.823 0.823 5.0 385.9 Flood Risk180 min Winter 9.883 0.883 5.0 414.2 Flood Risk240 min Winter 9.922 0.922 5.0 432.6 Flood Risk360 min Winter 9.968 0.968 5.0 454.0 Flood Risk480 min Winter 9.989 0.989 5.0 463.9 Flood Risk600 min Winter 9.997 0.997 5.0 467.4 Flood Risk720 min Winter 9.996 0.996 5.0 466.9 Flood Risk960 min Winter 9.994 0.994 5.0 466.3 Flood Risk1440 min Winter 9.976 0.976 5.0 457.6 Flood Risk2160 min Winter 9.925 0.925 5.0 433.7 Flood Risk2880 min Winter 9.861 0.861 5.0 403.8 Flood Risk4320 min Winter 9.651 0.651 5.0 305.2 O K5760 min Winter 9.429 0.429 5.0 201.2 O K7200 min Winter 9.284 0.284 5.0 133.3 O K8640 min Winter 9.193 0.193 4.8 90.7 O K10080 min Winter 9.140 0.140 4.6 65.8 O K
Storm
Event
Rain
(mm/hr)
Flooded
Volume
(m³)
Discharge
Volume
(m³)
Time-Peak
(mins)
60 min Winter 53.754 0.0 348.8 70120 min Winter 31.719 0.0 411.3 126180 min Winter 23.298 0.0 452.9 184240 min Winter 18.717 0.0 484.9 242360 min Winter 13.748 0.0 533.6 358480 min Winter 11.045 0.0 570.9 470600 min Winter 9.320 0.0 601.4 582720 min Winter 8.112 0.0 627.3 690960 min Winter 6.600 0.0 677.2 8921440 min Winter 4.935 0.0 734.5 11142160 min Winter 3.690 0.0 864.6 15842880 min Winter 3.002 0.0 937.4 20484320 min Winter 2.147 0.0 1004.0 29445760 min Winter 1.692 0.0 1057.5 35847200 min Winter 1.407 0.0 1099.3 42488640 min Winter 1.210 0.0 1134.3 484010080 min Winter 1.065 0.0 1164.4 5440
Waterco Ltd Page 3
Eden Court w10278
Lon Parcwr Business Park LLys Marl
Denbighshire LL15 1NJ Llandudno Jct
Date 17/05/17 Designed by SJP
File 1 in 100 year +30%CC.srcx Checked by AW
XP Solutions Source Control 2016.1
Rainfall Details
©1982-2016 XP Solutions
Rainfall Model FEH D3 (1km) 0.311 Cv (Winter) 0.840Return Period (years) 100 E (1km) 0.300 Shortest Storm (mins) 15
Site Location F (1km) 2.342 Longest Storm (mins) 10080C (1km) -0.030 Summer Storms Yes Climate Change % +30D1 (1km) 0.377 Winter Storms YesD2 (1km) 0.421 Cv (Summer) 0.750
Time Area Diagram
Total Area (ha) 0.775
Time
From:
(mins)
To:
Area
(ha)
Time
From:
(mins)
To:
Area
(ha)
Time
From:
(mins)
To:
Area
(ha)
0 4 0.258 4 8 0.258 8 12 0.258
Waterco Ltd Page 4
Eden Court w10278
Lon Parcwr Business Park LLys Marl
Denbighshire LL15 1NJ Llandudno Jct
Date 17/05/17 Designed by SJP
File 1 in 100 year +30%CC.srcx Checked by AW
XP Solutions Source Control 2016.1
Model Details
©1982-2016 XP Solutions
Storage is Online Cover Level (m) 10.000
Tank or Pond Structure
Invert Level (m) 9.000
Depth (m) Area (m²) Depth (m) Area (m²)
0.000 469.0 1.000 469.0
Hydro-Brake Optimum® Outflow Control
Unit Reference MD-SHE-0105-5000-1000-5000Design Head (m) 1.000
Design Flow (l/s) 5.0Flush-Flo™ CalculatedObjective Minimise upstream storage
Application SurfaceSump Available YesDiameter (mm) 105
Invert Level (m) 8.995Minimum Outlet Pipe Diameter (mm) 150Suggested Manhole Diameter (mm) 1200
Control Points Head (m) Flow (l/s)
Design Point (Calculated) 1.000 5.0Flush-Flo™ 0.296 5.0Kick-Flo® 0.637 4.1
Mean Flow over Head Range - 4.3
The hydrological calculations have been based on the Head/Discharge relationship for theHydro-Brake Optimum® as specified. Should another type of control device other than aHydro-Brake Optimum® be utilised then these storage routing calculations will beinvalidated
Depth (m) Flow (l/s) Depth (m) Flow (l/s) Depth (m) Flow (l/s) Depth (m) Flow (l/s)
0.100 3.6 1.200 5.4 3.000 8.4 7.000 12.50.200 4.8 1.400 5.8 3.500 9.0 7.500 12.90.300 5.0 1.600 6.2 4.000 9.6 8.000 13.30.400 4.9 1.800 6.6 4.500 10.1 8.500 13.70.500 4.7 2.000 6.9 5.000 10.6 9.000 14.10.600 4.3 2.200 7.2 5.500 11.1 9.500 14.50.800 4.5 2.400 7.5 6.000 11.61.000 5.0 2.600 7.8 6.500 12.1
Waterco Ltd Page 5
Eden Court w10278
Lon Parcwr Business Park LLys Marl
Denbighshire LL15 1NJ Llandudno Jct
Date 17/05/17 Designed by SJP
File 1 in 100 year +30%CC.srcx Checked by AW
XP Solutions Source Control 2016.1
Event: 480 min Winter
©1982-2016 XP Solutions
Waterco Ltd Page 6
Eden Court w10278
Lon Parcwr Business Park LLys Marl
Denbighshire LL15 1NJ Llandudno Jct
Date 17/05/17 Designed by SJP
File 1 in 100 year +30%CC.srcx Checked by AW
XP Solutions Source Control 2016.1
Event: 600 min Winter
©1982-2016 XP Solutions
Waterco Ltd Page 7
Eden Court w10278
Lon Parcwr Business Park LLys Marl
Denbighshire LL15 1NJ Llandudno Jct
Date 17/05/17 Designed by SJP
File 1 in 100 year +30%CC.srcx Checked by AW
XP Solutions Source Control 2016.1
Event: 720 min Winter
©1982-2016 XP Solutions
Llys Marl, Llandudno Junction FCA & Drainage Strategy
w10278-170518-FCA and Drainage Strategy
Appendix G – Maintenance Schedules
SuDS Maintenance Schedule
File Ref: G - Detention Basin -SuDS Maintenance
Operation and Maintenance Requirements for Detention Basins
Ref. Table 22.1 CIRIA C753 ‘The SuDS Manual’
Maintenance Schedule Required Action
Typical Frequency
Regular maintenance
Remove litter and debris Monthly
Cut grass-for spillways and access routes Monthly (during growing season), or as required
Cut grass - meadow grass in and around basin
Half yearly (spring - before nesting season, and autumn)
Manage other vegetation and remove nuisance plants
Monthly (at start, then as required)
Inspect inlets, outlets and overflows for blockages, and clear if required. Monthly
Inspect banksides. structures. pipework etc. for evidence of physical damage Monthly
Inspect inlets and facility surface for silt accumulation. Establish appropriate silt removal frequencies.
Monthly (for first year), then annually or as required
Check any penstocks and other mechanical devices Annually
Tidy all dead growth before start of growing season Annually
Remove sediment from inlets, outlet and forebays Annually (or as required)
Manage wetland plants in outlet pool – where provided
Annually (as set out in Chapter 23)
Occasional maintenance
Reseed- areas of poor vegetation growth As required Prune and trim any trees and remove cuttings Every 2 years. or as required
Remove sediment from inlets, outlets. forebays and main basin when required
Every 5 years. or as required (likely to be minimal requirements where effective upstream source control is provided)
Remedial actions
Repair erosion or other damage by reseeding or re-turfing As required
Realignment of rip-rap As required Repair/rehabilitation of inlets, outlets and overflows As required
Relevel uneven surfaces and reinstate design levels As required
SuDS Maintenance Schedule
File Ref: G - Detention Basin -SuDS Maintenance
The maintenance requirements detailed above are to be undertaken by the site owner
Name: ……………………………………………….
Position: ……………………………………………….
Date: ………………………………………………. Signed on behalf of site owner ……………………………………………….
SuDS Maintenance Schedule
File Ref: G - Permeable Paving - SuDS Maintenance
Ref. Table 20.15, CIRIA C753 ‘The SuDS Manual
Maintenance Schedule
Required Action Typical Frequency
Regular maintenance
Brushing and vacuuming (standard cosmetic sweep over whole surface)
Once a year, after autumn leaf fall, or reduced frequency as required, based on site-specific observations of clogging or manufacturer’s recommendations – pay particular attention to areas where water runs onto pervious surface from adjacent impermeable areas as this area is most likely to collect the most sediment
Occasional maintenance
Stabilise and move contributing and adjacent areas As required
Removal of weeds or management using glyphospate applied directly into the weeds by an applicator rather than spraying
As required – once per year on less frequently used pavements
Remedial actions
Remediate any landscaping which, through vegetation maintenance or soil slip, has been raised to within 50mm of the level or the paving
As required
Rehabilitation of surface and upper substructure by remedial sweeping
Every 10 to 15 years or as required (if infiltration performance is reduced due to significant clogging)
Monitoring
Inspect for evidence of poor operation and / or weed growth – if required, take remedial action
Three-monthly, 48hr after large storms in first six months
Inspect silt accumulation rates and establish appropriate brushing frequencies
Annually
Monitor inspection chambers Annually
Operation and Maintenance Requirements for Permeable Paving
SuDS Maintenance Schedule
File Ref: G - Permeable Paving - SuDS Maintenance
The maintenance requirements detailed above are to be undertaken by the site owner.
Name: ……………………………………………….
Position: ……………………………………………….
Date: ………………………………………………. Signed on behalf Of the site owner ……………………………………………….
SuDS Maintenance Schedule
File Ref: G - Ponds and Wetlands -SuDS Maintenance
Operation and Maintenance Requirements for Ponds and Wetlands
Ref. Table 23.1 CIRIA C753 ‘The SuDS Manual’
Maintenance Schedule Required Action
Typical Frequency
Regular maintenance
Remove litter and debris Monthly (or as required)
Cut the grass – public areas Monthly (during growing season), or as required
Inspect marginal and bankside vegetation and remove nuisance plants (for first 3 years)
Monthly (at start, then as required)
Inspect inlets, outlets, banksides, structures, pipework etc for evidence of blockage, and / or physical damage.
Monthly
Inspect water body for signs of poor water quality Monthly (May – October)
Inspect silt accumulation rates in any forebay and in main body of the pond and establish appropriate removal frequencies; undertake contamination testing once some build-up has occurred, to inform management and disposal options.
Half yearly
Check any mechanical devices e.g. penstocks Half yearly
Hand cut submerged and emergent aquatic plants (at minimum of 0.1m above pond base; include max 25% of pond surface)
Annually
Remove 25% of bank vegetation from water’s edge to a minimum of 1m above water level
Annually
Remove sediment from any forebay Every 1 – 5 years, or as required
Remove sediment and planting from one quadrant of the main body of ponds without sediment forebays
Every 5 years, or as required
Occasional maintenance Remove sediment from the main body of big ponds when pool volume is reduced by 20%
With effective pre-treatment, this will only be required rarely, e.g. 25-50 years
Remedial actions
Repair erosion or other damage As required Replant where necessary As required Aerate pond when signs of eutrophication are detected As required
Realign rip-rap or repair other damage As required Repair/rehabilitate of Inlets, outlets and overflows As required
SuDS Maintenance Schedule
File Ref: G - Ponds and Wetlands -SuDS Maintenance
The maintenance requirements detailed above are to be undertaken by the site owner
Name: ……………………………………………….
Position: ……………………………………………….
Date: ………………………………………………. Signed on behalf of site owner ……………………………………………….
SuDS Maintenance Schedule
File Ref: Tank - SuDS Maintenance
Operation and Maintenance Requirements for Attenuation Storage
Tanks
Ref. Table 21.3, CIRIA C753 ‘The SuDS Manual’
The maintenance requirements detailed above are to be undertaken by the site owner.
Name: ……………………………………………….
Position: ……………………………………………….
Date: ………………………………………………. Signed on behalf Of the site owner ……………………………………………….
Maintenance Schedule
Required Action Typical Frequency
Regular maintenance
Inspect and identify any areas that are not operating correctly. If required, take remedial action
Monthly for 3 months, then annually
Remove debris from the catchment surface (where it may cause risks to performance) Monthly
For systems where rainfall infiltrates into the tank from above, check surface of filter for blockage by sediment, algae or other matter; remove and replace surface infiltration medium as necessary
Annually
Remove sediment from pre-treatment structures and/ or internal forebays Annually, or as required
Remedial actions Repair/rehabilitate inlets, outlet, overflows and vents As required
Monitoring
Inspect/check all inlets, outlets, vents and overflows to ensure that they are in good condition and operating as designed
Annually
Survey inside of tank for sediment build-up and remove If necessary
Every 5 years or as required