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Msport race car factory and race track creates 10.9 hectares (27 acres = 109,000m2) of concrete and tarmac in addition to the existing buildings (about 3 hectares/7 acres). Flood risk from surface water is the primary source of flood risk.
(MM Flood risk assessment P19)
(Curtins Drainage Strategy p4 1.3)
Rain is not absorbed into the ground here and heavy rain would run straight into Dovenby Beck and Brides Beck and cause flooding. Flood attenuation ponds store storm water and discharge it at a green field runoff rate. The storage capacity of the ponds is calculated from as a probability of storm event.
The November application uses 1 in 30 years rainfall plus 30% to calculate a required pond sizes of 1350m3 & 2200m3 and a “storm cell” 1250 cubic metres under the car park, total 5800m3 . (See Drainage Rev C 1.6 & plan on last page)
Planning Condition 17 December 2014 requires “rainfall events up to 1 in 100 years plus Climate Change are dealt with via on site storage.” NOT the 1 in 30 year calculation. Surely the same or more storage volume is required for a more rare rainfall event?
We have just seen December 2015 have a rainfall event that was bigger than the 1 in 100 year event that we suffered in 2009 AND 2005, which had been called a 1 in 100 year event.
The Approved Flood Condition 17 plan on page 7 removes the “storm cell” 1250m3 storage and replaced it with a new pond that is obviously half the size of the 1350m3 pond, so obviously cannot deal with the missing 1250m3 nor hold the extra rainfall for an event nearly three times more significant than originally calculated.
Until otherwise explained, it seems that
Allerdale and Cumbria County Council Drainage advisor have approved a 1 in 100 year rainfall with LESS storage than was calculated for the 1 in 30 year event!
Flood Risk Assessment in the application states:
A Flood Risk Assessment (FRA) being produced by Mott MacDonald to accompany the planning application. The site is within Flood Risk Zone 1 (low risk).
But this seems contradicted by Land Registry Deeds Flood Risk Indicator Title number CU134916 Dovenby Hall,
The land registered under the above title number is Affected by a floodplain. The land is in an area that has a significant chance of Flooding which means that the chance of flooding each Year is greater than 1.3 percent (1 in 75).
Dovenby Beck and Brides Beck, are Classified as Flood Zone 3 (High Probability) and hence are defined as ‘land assessed as having a greater Than 1 in 100 annual probability of fluvial or tidal flooding’
The December 2015 floods greatly disrupted our rural areas in a significant way. The Environment Agency recently handed responsibility for Local Flood Risk Management (LFRM) to Cumbria County Council who may not be aware of the changes to the drainage calculations. This may be why the LFRM state that the extra discharge of 45 litres/second into Brides Beck which is already a Flood Zone 3 “There is no flooding danger to properties from the test track part of the site as the watercourses flow to the river in a very rural location.”
There is an urgent need to re-appraise the potential of extra flood risk that could be caused downstream of this development. Surely at the least, there should be the storage volume of rainfall that was calculated for the 1 in 30 year event, ie 5,800m3 with an extra storage capacity of 30% ie 1,740m3 which is a total storage capacity of 7540 cubic metres.
Allerdale Strategic Flood Risk Assessment page 13 states
planning policy is now heavily weighted against development which will cause or worsen flooding in any areas. The financial consequences of flooding are also more severe for most properties now than historically because of the greater value of the buildings and their contents. The average insurance claim for domestic flooding is now between £15,000 and £30,000 (Association of British Insurers).
2014 09 23 Environment Agency require 1 in 100 year calculation
2014 11 13 Allerdale Drainage Officer asks if enough space for ponds and pipe falls
Environment Agency gives warning.
2015 02 24 Cumbria Highways Response conditions 5 8 17
2015 02 19 Condition 17 Environment Agency no objection
Cumbria CC Lead Local Flood Authority agree to discharge condition 17 “as the proposal would improve the surface run off to Brides Beck”
2015 03 31 CCC Drainage Officer tries to explain but inaccuracies are in [italics]
Subject: M Sport Dovenby
From Claire Chambers Senior Planner Allerdale to Cumbria Drainage OfficersAndrew Harrison / Doug Coyle
Thank you for the comments you made on the Discharge of Conditions Application for M Sport.
Our reference CON1/2014/0350. Your reference AH/2014/0350..
You advised that the Lead Local Flood Authority agree to the discharge of condition 17 as the
proposals would improve surface run off to Brides Beck. However, a letter of objection has been
submitted by a local resident about the discharge of this condition.
The objector makes the following comments :
- The calculations should take account of a 1 in 100 year event, but the calculations are
based on a 24 hour storm and in a 100 year event the storm is likely to last for more
than 24 hours with correspondingly more rain to be stored in the attenuation ponds.
The calculations used are for a 1 in 100 year return plus 20% for climate change as set out in
Curtins drainage strategy.
[See comments above; there is less storage capacity from in 100 year calculations than in the 1 in 30 year rainfall calculations]
- The calculations in the application resulted in a 1250m3 volume of water to be stored in
the ‘’storm cell’’ under the car park. This is now not shown but a third pond is shown
with no capacity.
More details will be required as a condition for the hotel part of the development, this part of
the application is at outline.
[The storm cell and car park are part of the detailed planning permission for the MEC and race testing track, now approved. If the absence of 1250 cubic metres of storage had been realised then would this affect the potential for flood water not being stored and affect the advice about approval? Should an advisory letter be sent to the developer now to suggest that a storage pond of 1250m3 should be put on the site to replace the 1250m3 missing storm cell?]
- The volume of the ponds cannot be verified until the slope of the sides of the ponds is
given which is missing on the drawings and calculations.
These are included in Curtins drainage strategy.
[The heights are given but not capacity nor the slope of sides (shallow sides have low capacity, steep sides will erode, silt and reduce capacity.]
- The plans approved were for two ponds. There are now three ponds.
I believe the third pond may be the hotel attenuation that will be addressed and details
requested further down the planning process
[The third pond is inside the track and drainage to it from the track is on the plan]
- The application and the approval based on the application plans show flood attenuation
capacity that requires two ponds and a 1250m3 storm cell. Those capacities were based
on a 1 in 30 year storm event. Condition 17 requires :
‘’No development approved by this planning permission shall take place until such time
as a detailed drainage design which demonstrates how rainfall events up to 1 in 100 plus
Climate Change are dealt with via on site storage.’’
However, the application to discharge this condition shows the same, or smaller capacity
to store rainfall even though the rainfall event for 1 in 100 is likely to be much greater
than the 1 in 30 year event that was shown on the original application and which is
repeated in the Condition application. The volume of the extra pond is not shown and
does not negate this criticism.
The pond capacities are based on a 1 in 100 year plus 20% climate change, normally climate
change is 30% but the fact that the developer has used the whole area of the site and not just
the test track in its calculations means that the actual flow rates will be even less than the
[The storage capacity is lower for a 1 in 100 year event than for a 1 in 30 year event]
There is no flooding danger to properties from the test track part of the site as the watercourses
flow to the river in a very rural location.
[[Two properties and the rural road are at risk of flooding. Accumulated flood water caused Dec 2015 floods]
I am hoping that you can answer these queries for me – As I will need to address all the
objectors comments in my report.
Allerdale Borough Council, Allerdale House, Workington, Cumbria, CA14 3YJ
To: Chambers, Claire
Cc: Coyle, Doug
Subject: FW: M Sport Dovenby
There is no flooding danger to properties from the test track
part of the site as the watercourses
flow to the river in a very rural location.
[WRONG: Station House and the house by the road that already floods are shown here]
From Andrew Harrison
Drainage & Surface Water Officer | LFRM | Environment | Cumbria County Council | Parkhouse Building | Kingmoor Business Park | Carlisle | CA6 4SJ Tel: 07825340786
Are Allerdale & Cumbria Drainage Officer aware that two houses may be flooded if Msport drainage calculations are incorrect?
I am aware of past flooding of the highway at Priest's Bridge/Bride's Beck to the south of the site.
Any intention to discharge surface water to this watercourse should be limited to a flow rate equal to the
present greenfield runoff rate so that development will not increase flood risk to others. Thanks,
Sent: 16 September 2014 16:46
To: Brook, Sara
Subject: RE: 2/2014/0350
Did Allerdale Planning and Cumbria LFRM Drainage Officers weigh disruption to “very rural location” roads when there is known flooding of the rural road at this point?
Allerdale & Cumbria Councils decided “There is no flooding danger to properties [from the development] as the watercourses
flow to the river in a very rural location..” (See below)
Oops!! It seems development outweighs the risk of increased rural flooding that affects downstream businesses roads, houses, and farming.
Explanation: Allerdale BC approved Msport’s development of a car factory and testing track at Dovenby Hall that will cover 10.9 hectares (109,000square metres) of parkland in concrete and tarmac . Dovenby Hall parkland drains into the highest risk zone 3 watercourses which contribute to the River Derwent flood risk and requires storage ponds to attenuate flood water from big storms.
5,800 cubic metres of flood ponds were calculated for 1 in 30 year storm but Allerdale & Cumbria planners approved the removal of 1250 cubic metres of storage for a 1 in 100 year storm, so surely the flood risk has been increased?! (See evidence below)
Allerdale and Cumbria CC Drainage have ignored an inconvenient requirement for flood defence which will mean that the community suffer flooding as a result. Allerdale are getting their planning priorities unbalanced towards developers and against the environmental concerns of their community.
Cumbria CC need a policy that understands rural locations need protection from development that may increase flood risk downstream. Retrospective remedial planning conditions are surely required.
ALLERDALE & CUMBRIA REDUCE THE CAPACITY OF FLOOD STORAGE PONDS
How much rain falls on Msport’s race track and factory?
The race track, factory and car parking is 10.9 hectares is 109,000 square metres (m2)
1 mm rain = 109 cubic metres of rain water
10mm rain = 1,090 cubic metres of rain
50mm rain (2 inches) - 5,450 cubic metres of rain
Storage capacity for 1 in 30 year rainfall event
40mm rain = 4,360 cubic metres of flood water
The approximate storage approved for 1 in 100 year rainfall event accepted by Allerdale Planning & Cumbria Drainage Officer
100mm rain = 10,900 cubic metres of rain water that would need to be stored and released slowly so that flooding risk is not increased. The approved development at Dovenby Hall Estate does not have enough space to accommodate this volume of storage, it has not been required by Allerdale nor Cumbria CC.