No-dig, no compaction!

Recent experience has suggested clients are getting used to the concept of ‘no-dig’ construction, but still failing to realise that in those areas designated as ‘no-dig’, as well as Tree Protection Zones, there should be no compaction either – that means no machines…

‘It is very important to realise that a major contribution to soil compaction , probably 80%, occurs in the first passage of vehicles over the ground’ (Smith 1987), a major fraction of the compaction occurs when only two wheels have passed over the ground. (Tree Roots in the Built Environment).

That means that a demo-lorry or 360 can cause major damage just accessing a site.

For healthy tree growth, soil has to be 50% solid matter (mineral and organic), 25% water, and 25% air. The compaction caused by works traffic will virtually eradicate the air content.

In simple terms trees have two types of roots. Woody structural roots that hold the tree up; and tiny hair like feeder roots (which absorb water and nutrients). The tiny hair like feeder roots only grow by cell division through pores in the soil. If compaction causes these pores to collapse, root growth becomes restricted, and eventually impossible. The supply of water and nutrients is effectively cut off, and this is what causes eventual dieback or death of trees in the long term.

To avoid breaching conditions, the ground behind the Tree Protection Fence must be protected from digging and compaction from the word go, and the correct sequence of events followed when installing ‘no-dig’ construction.

Soil compaction cannot be easily rectified, and coupled with stop notices, remediation can be an expensive business. So please let us explain the principles of the Arboricultural Method Statement for your own protection!

 

Planning Consent for Driveways

The Government’s joint guidance publication from the Communities and Local Government Department and the Environment Agency last year raised hardly a ripple (excuse the pun) and yet has a major implication for house builders and home owners.

The Guidance now requires that you will need planning permission if a new or replacement driveway of more than five square metres of traditional, impermeable paving that does not allow for the water to run to a permeable area. You will not planning permission if permeable or porous paving is used or if the surface water is directed to a lawn or border.The detail is important though, as a hardcore or Type 1 sub-base will be deemed to impervious due to the fines and Type 3 or 4/20 should be used instead. Interestingly, the Guidance notes that surface water returned to the soil assists the cooling affect around houses and its loss can cause local temperatures to rise, often referred to as the urban heat island effect.

 

Trees and shade

Designers seek guidance from Arborists on what is a sustainable and justifiable relationship between buildings, open spaces and trees. In our experience Councils often cite ‘pressure to prune or fell’ as a justifiable reason for refusal of planning permission. This ‘pressure’ tends to arise from three main causes:

1) Debris – Tree debris can be caught in gutter traps, or car ports provided

2) Perceived fear of part or whole tree failure – This can often be overcome by education and tree inspections.

3) Shade – This is somewhat more elusive, with contrary views and opinions around every corner.

Arboricultural consultants look to published documents for guidance, including: BS5837:2005, BRE 209, BRE Digest 350, BRE 380, and DETR 245.

This guidance can be difficult to action. For example BRE 209 quotes “trees and shrubs need not be included [in shade calculations], partly because their shapes are impossible to predict, and partly because the dappled shade of a tree is more pleasant than the deep shadow of a building.” However, it goes on to say that their growth and final size should be allowed for.

British Standard 5837:2005 guides us to consider where trees could cause unreasonable obstructions to sunlight or daylight and references to BRE 350 & 209.

These documents propose that tree retention and planting close to buildings can be warranted and of value, specifically in reducing solar gain and energy costs.

In the USA large trees are planted in urban environments specifically to provide shade. It is appreciated that the UK’s climate is not that of America but, one can only assume that the issues that plague our Tree Officers, such as debris and perceived fear, are overcome in America, to provide some outstanding examples of trees, flourishing within the urban jungle.

It is acknowledged that there is such a thing as a poor relationship between a tree and a building, and it is the Arboriculturist job to bring these to the attention of layout designers, and instigate change when possible. With good layout design and liaison between the design team and Planning Officers, the demons of ‘pressure to prune’ can be avoided.

With ACD extensive experience in the planning arena, we can provide sound, robust client advice on scheme design, and yes, we will tell you if it doesn’t work! Coming up in the end with a viable solution to which all parties can sign up.

 

Recent Changes to NHBC Chapter 4.2

The NHBC Standard 2008 came into force in September 2008. Chapter 4.2 of this document is the industry standard for calculation foundation design in relation to existing and proposed trees. The revised standard has some significant consequences for Engineers, Architects, Arboriculturists and Landscape Architects.

1. There is a section included, on how to calculate soil heave following the removal of a tree. A pre-strip survey of all vegetation is required, otherwise an engineer has calculate the worse conditions – i.e. all trees are high water demand and therefore bigger foundations are required.
2. Foundations of garages, porches and free standing walls must be taken into account – previously these tended to be ignored in relation to trees. Now an engineer will have to build bigger foundations.
3. Root barriers – ‘are not a reliable means of reducing the effects of trees on foundations’. This weakens the argument for placing larger trees close to buildings and compensating with root barriers.
4. Foundations now have to take into account shrubs and climbers:
   • shrubs/climbers under 1.8m mature height – no affect
   • Pyracantha and Cotoneaster with mature height over 1.8m, plant 1X mature height away from foundation to avoid any affect – closer bigger foundation
   • All other shrubs/climbers over 1.8m – plant 0.75x mature height away from foundation to avoid affect.

Conclusions –

Early site survey work could reduce the depth of foundations by identifying tree species prior to their removal.

Sufficient space within a development will need to be provided by layout designers.

Conflicts for structural landscaping and the cost of additional foundations will be common as developers strive to achieve higher densities and site viability.

 

Play Area Guidelines

Recently research and guidance has been produced regarding children’s play with two main sources of information: Fields in Trust (FIT), formally NPFA, and Play England. Play England provides advice on the quality of the play space and the philosophy of children’s play, whilst FIT continues to provide quantitative advice on the type and number of provision. New FIT guidelines were introduced in August 2008 to update ‘The Six Acre Standard’. These new guidelines are entitled Planning and Design for Outdoor Sport and Play’ (PAD). The following points are of particular relevance for residential developments:

• Play areas no longer have to provide a set number of pieces of equipment, but rather play experiences, for example, a LEAP has to provide a minimum of six experiences and a NEAP has to provide a minimum of nine play experiences. Therefore a scheme could theoretically be achieved without equipment.
• For higher density developments, particularly ‘brownfield’ sites, the play area buffer zone may be reduced around LEAPs which could result in a reduction from 3600m2 to 1600m2 and a consequently larger developable area.
• You no longer need to enclose a play area within a fence, only if the play area abuts a road, water course or other hazard.
• Local Landscaped Area for Play is a new designation that sits between a LEAP and a NEAP. Fundamentally this is an unequipped space that is specifically laid out to encourage imaginative play for all ages.
• The methodology of assessing existing play spaces has changed and is now based on a points system which will conclude if the local provision is of a high quality and experience.

For more information please read on…

 

Important Changes to Natural England Licencing

Natural England is streamlining the EPS licensing process, removing the LPA questionnaire requirement, and in certain exceptional circumstances, replacing the current requirement for full planning permission (or other relevant consents in non-planning situations) prior to the issue of a European Protected Species (EPS) licence. The changes, now in force, speed the process by omitting the need to have the Planning Authority prepare an element of the licence application, coming as a result of applicants complaining that LPAs were unable to process the work quickly enough.

Below is an extract from a Q&A document produced by NE, outlining the principle changes:

Natural England also adds that ‘there is a risk in applying for a licence on an exceptional basis since it will increase the risk of the applicant failing to meet the licensing tests’. Natural England also adds that exception cases will be rare.

In summary,it allows some exclusions, but is mainly a reversion to the older system that did not include LPA involvement and, as such, has taken 6-8 weeks off the process.

For information: Notice of change to Licensing Process for EPS Mitigation Licences

Summary of Change: Natural England is streamlining the EPS licensing process. The requirement for the LPA questionnaire is being removed, and in certain exceptional circumstances, we are replacing the current requirement for full planning (or other relevant consents in non-planning situations) prior to the issue of a European Protected Species (EPS) licence.

This will be a more flexible approach that recognises that full consent may not always be needed before Natural England processes the licence application. This will be balanced by adding a licence condition (where appropriate) that makes the derogation contained in the licence conditional on necessary permissions being obtained before the licensed activities commence.

 

Don’t let nature run wild!

In the downturn, few sites are moving ahead with any speed, if at all. Sites left ‘fallow’ will quickly revert to nature and become attractive to aspects of wildlife that can become potential constraints in the future. ACD strongly recommends that house-builders plan for long term closures by manipulating habitats wherever they can:

• It is illegal to destroy bird-nesting sites and suitable scrub and hedgerow vegetation can limit development during the nesting season from March-August. Any sites for development this year should have areas of vegetation cleared by the end of February or an acceptance that it may remain insitu until the autumn.
• Reptile habitats can vary, but whilst a cleared demolition site has little interest for reptiles, the increase of vegetative cover will increase its interest and a site that this year required no reptile survey or translocation could become next years destination of lizard choice. Whilst not a European protected species, it is again illegal to wilfully harm reptiles – better to ensure that the site is reptile fenced to limit access, or that the ground is manipulated to limit vegetation ie ploughing or strimming.
• Badgers are constantly on the move and surveys are best left until development is imminent, as a sett closure or disturbance licence will require current survey data – but be warned, badgers love derelict sites where they can be left in peace and quiet, the grassier the better. Scrub regeneration, grass left unmaintained and general lack of use will be an attraction for foraging badgers and an outlier sett that one may dig for temporary cover, may become a more permanent maternal sett if the ground conditions are right, food plentiful and humans absent. Keep it clear – it is the same habitat that birds will use for nesting and can develop very quickly.
• Bats are a European Protected Species and are also constantly changing roosting sites. Buildings left intact on sites will therefore be of interest if they have enclosed and draught-free loft spaces, tile hanging or other suitable roost areas. The answer is simple if demolition is for whatever reason not permitted – render the spaces unsuitable by opening them where possible.
• Japanese Knotweed is an invasive Notifiable weed that can blight a development site and pose an expensive problem if eradication is required swiftly. Standard chemical eradication is achieved cost-effectively over a three year period, but an instant fix is only achieved through physical removal of the soil containing the root rhizomes (up to 3m deep and 7m from the clump centre) to a registered tip for contaminated soil, or the use of a ‘quick-fix’ contractor who uses increased chemical dosing and cane-injection at a seriously inflated cost to cover their guarantee. Check sites in April/May for signs of the weed and deal with it with Glyphosate chemical application whilst it is still affordable.

You will know all about great crested newts and water-bodies left on site, you will know a little less about stag-beetles and their favourite places, you will probably be unaware of chalkland ground-nesting birds and you probably shudder at the thought of water-voles taking a fancy to your stream – plan for it, allow for it in your revised programming and take the necessary measures to ensure it doesnt come back to bite you in a years time!

 

Changes to play guidelines

‘The Six Acre Standard’ has been updated by Fields in Trust (formerly NPFA), the new guidelines entitled ‘Planning and Design for Outdoor Sport and Play’ were published on 1st August 2008, and continue to offer quantitative guidelines for play provision throughout the UK. The new guidelines link in with the design guidance from ‘Play England’ entitled ‘Design for Play: A guide to Creating Successful Play Spaces’ , which offers qualitative recommendations for play. The two provide a holistic approach to play area design with the play design horizons broadening.

To access the new guidelines refer to the weblink:

http://www.npfa.co.uk/get_involved/publication_planning.php
http://www.playengland.org.uk/resources/design-for-play.pdf

 

Japanese Knotweed Control

Story in the Press this week. – JAPANESE KNOTWEED CONTROL

Defra have applied to the Advisory Committee on Release to the Environment (ACRE) for a Licence to introduce a Japanese insect, Aphalara itadori, to aid in the control off Japanese Knotweed (JN).
ACRE have, for the moment, suspended a decision due to insufficient information to support the licence.

Extensive tests by CABI, have shown this insect only attacks JN, it basically sucks the sap out from the plant significantly weakening the plant. They are also carrying out tests on a leaf spot fungus found to attack the plant in its native habitat, which may also be released in the future, following testing. In its native country JN is not so widespread, the scientists at CABI believe this is down to the natural predators it has evolved with, hence this study.

From our point of view there are several issues:

1. Both are not available yet and will only potentially be licensed by DEFRA.

2. The insect and leaf fungus only weaken the plant, they do not actually kill the plant – both would have to be used in conjunction with other treatments.

3. The industry needs to be convinced that importing non-natives has no affect on other species.

4. No guarantee of how long it would take to weaken the plant, or if it will even work.

5. Its not the ‘Silver bullet’ – we should carry on advising Glyphosate spraying as the most economic/realistic treatment.

John Constable CMLI
Senior Associate

Link to original BBC News story: http://news.bbc.co.uk/2/hi/science/nature/7531221.stm

 

Changes to TPO application procedure and appeals process

Since October 1st Local Authorities can only accept applications for tree work to for trees subject to a TPO on the new standard application form. Guidance for filling it in can be found here.

An important element of the new procedures is the requirement to provide specific information in support of applications for work relating to trees which is required because of their condition or the damage they are causing to property.

The Regulations also introduce, from 1 October 2008, a new fast-track appeal system. Inspectors will only be able to consider the information provided with the original application; there will be no written representations procedure available.

An addendum to Tree Preservation Orders: a Guide to the Law and Good Practice (commonly known as ‘The Blue Book’), which provides detailed guidance and information has been produced. This can be downloaded here: http://www.communities.gov.uk/documents/planningandbuilding/pdf/tposguideaddendum.pdf