John A. Boynton
Judith G. Boynton
42 St. Leonard's Terrace
London SW3 4QH
1 September 2015
Mr. Graham Stallwood
Executive Director
Planning and Borough Development
Royal Borough of Kensington and Chelsea
Town Hall
Hornton Street
London W8 7NX
Dear Mr. Stallwood
Reference: PP/15/04516
Proposed Basement Development at: 5-6 Durham Place, London, SW3 4ET
1.1
We write further to our objection letter of 12 August 2015 regarding the above planning
application. In that letter, we raised very serious concerns about the risks of excavating a
basement to a depth of 7 metres or more, through the groundwater table, beneath a
terrace which was built in 1790.
1.2
We have now had the opportunity to review the Council Planning Officer's report to the
Planning Applications Committee as well as the 19 other objection letters submitted by
many concerned neighbours. Despite the Officer's recommendation to grant planning
permission, we remain strongly of the view that the proposed development poses very
significant, unacceptable risks to our neighbourhood in terms of tree protection, flooding,
structural stability, amenity impacts, and construction impacts. Therefore, we request that
the Planning Applications Committee refuse this planning application.
1.3
We set out below our specific concerns arising from the Officer's report. This letter should
be read in conjunction with our objection letter dated 12 August 2015 which explains our
concerns in further detail.
2.
The proposed basement development is not policy compliant
2.1
Paragraph 6.1 of the Officer's report states that the proposal involves the extension of an
existing single storey basement.
2.2
It is evident from the application plans that the property already has a basement and that
the proposal is for a second basement. This is reflected in the reference to the "existing
basement" at paragraph 6.1 of the Officer's report. The proposal is therefore clearly
contrary to policy CL7 which provides that basements shall not comprise more than one
storey except in a few limited situations which do not apply in this case. Therefore, the
proposed second basement is not policy compliant and should be refused.
2.3
Furthermore, the proposal carries all of the risks of the development of a second
basement. The depth of the existing basement, which the applicant seeks to lower even
further, means that the second basement will need to be constructed through one metre
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of ground water at 7 metres or more below ground level. This greatly increases the
complexity and risk associated with the project and is clearly inconsistent with the intent
of the one-storey basement policy.
3.
The proposed basement development will result in harm to trees
3.1
Paragraph 6.1 of the Officer’s report concludes from the application documents that “no
trees will be harmed” as a result of the development.
3.2
It is incorrect to conclude that there will be no harm to trees. A 22 metre high mature
healthy sycamore tree in the property’s rear garden is directly threatened by this
basement excavation proposal. This tree is protected by virtue of its location in a
Conservation Area. Calculations provided in the applicant’s tree survey indicate that the
basement excavation would impact 13% of the sycamore tree’s root protection area,
which itself is of great concern. However, Dr. Jon Heuch, an experienced Arboricultural
Specialist whom we engaged, assessed the tree risks associated with the planning
application to be much greater. In particular, Dr. Heuch advised that:
(a)
The natural root growing area of the tree is within the garden boundary walls of
the property, including where the basement excavation will occur.
(b)
The basement excavation will require piling to 7 metres below ground level in the
rear garden which will sever all of the tree roots in that area.
(c)
As a consequence the development will reduce the rooting area for the tree
within the property’s rear garden from 134 square metres by 36 square metres, a
reduction of 27%.
3.3
Dr. Heuch concluded that the impact of the basement excavation on the sycamore tree is
likely to be more significant than assessed and is likely to harm the tree. The condition
recommended in the Planning Officer’s report will not prevent this harm as the tree’s
roots will be severed during excavation.
3.4
The applicant has undertaken no testing within the basement footprint in the rear garden
to establish the extent of the sycamore tree roots that will be severed. In accordance with
the policy, the Council is entitled to request this information and, in our view, it would be
taking an unnecessary and inappropriate risk to grant planning permission for the
proposal without full information about the risks to the health and stability of trees. Such
a decision would also be contrary to the Council's planning policies which state that
basement developments shall not cause loss, damage or long term threat to trees of
townscape or amenity value.
3.5
We also are very concerned that the harm to the sycamore tree will cause the tree’s
health to decline and its natural life to be shortened. A damaged tree poses safety risks to
the neighbours and our properties. This risk is increased as we regularly get very high
winds in this area. A weakened or destabilised tree could fall onto neighbours or our
properties at any time. Without definitive knowledge that the tree roots will not be
harmed, the planning application should be refused.
4.
Critical information about the structural and flooding risks is missing
4.1
Paragraph 6.2 of the Officer's report concludes from the application documents that the
proposed works would not affect the integrity or stability of the host or surrounding
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properties. There is no information in the report as to how this conclusion was reached
and no information addressing the flood risks to surrounding properties. Instead, the
Officer's recommendation to grant planning permission appears to rely on the future
supervision of the construction works by a chartered engineer.
4.2
As explained in our letter of 12 August, excavating to 7 metres or more below ground
level, through the water table, beneath a 225 year old terrace is an inherently high risk
proposal. The applicant's own Ground Investigation Report identifies a number of risks
and areas where further information is required. This proposal involves significant water
management challenges, and poses risks to surrounding buildings and their foundations.
4.3
While the 1-7 Durham Place terrace is not listed, it is of exceptional historical significance
given its 225 year age dating back to the 18th century. It is our understanding that certain
current and former owners of properties within the 1-7 Durham Place terrace have
encountered structural issues associated with non-basement renovation projects. No
basement proposal excavated through over one metre of ground water and reaching a
depth of 7 metres below ground level within this historic terrace has ever been approved
by the Council.
4.4
Based on information in the application documents and the Officer's report, it is not
possible to make an informed decision about whether the proposed excavation can be
undertaken without posing an unacceptable risk to the structure and fabric of the historic
terrace or the stability of surrounding properties. Accordingly, we would urge the Council
to seek further information, such as detailed method statements and construction plans,
and to take its own engineering advice. Without definitive information that the terrace
will not incur structural harm from the proposed basement excavation, this planning
application should be refused.
5.
There is a lack of transparency about the depth of the basement
5.1
Paragraph 7 of the Officer's report states that the main part of the basement is 3.15m
deep with a further 1.85m of depth for the swimming pool.
5.2
It is unclear how this depth has been calculated as the application drawings do not show
measurements (or in the case of the proposed elevations the additional depth for the
swimming pool) and the application documents variously refer to the basement as being
approximately 6 or 7 metres below ground level. Other objectors and their advisors have
calculated the basement to be up to 8.35 metres below ground level.
5.3
These differences may depend on whether the internal or external depth is measured and
whether the additional excavation to lower the existing basement is included. The Council
is entitled to request greater certainty, including accurate planning drawings. Regardless
of which measurements are taken, it is clear that the basement will need to be
constructed below the groundwater table which will greatly exacerbate the stability and
flooding risks noted above.
6.
The amenity impacts have been incorrectly assessed
6.1
Paragraph 6.5 of the Officer's report states that the proposed glass doors will not be
visible outside the site.
6.2
This conclusion is incorrect, which has led to the impacts on the character and appearance
of the Conservation Area being significantly underestimated. The new wall to wall glass
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doors will, in fact, be directly visible from the living areas on the upper floors of some
residential properties on Tedworth Square and St. Leonard’s Terrace. In addition, the
extent of the proposed glazing will increase light and noise pollution and impact on the
sense of privacy for us and many other properties that overlook the garden of 5-6 Durham
Place. It is also insensitive to the historical terrace which was built in 1790 and fails to
preserve or enhance the character or appearance of the Conservation Area.
7.
Conclusion
7.1
As we explained in our letter of 12 August, we consider that the risks of excavating to
7 metres or more below ground level on a constrained site, beneath a historic terrace, and
adjacent to several large and beautiful trees, far outweigh the private benefits of the
proposal.
7.2
Our concerns have not been adequately considered and addressed in the Officer's report
for all of the reasons set out above. Accordingly, we strongly object to the planning
application and continue to request that planning permission be refused. We intend to
make representations before the Planning Applications Committee on 8 September and
would welcome the opportunity to answer any questions that the Committee may have
about the concerns set out in this letter.
Sincerely,
John A. Boynton
Judith G. Boynton
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