Worksop STW Sludge Digestion - Nottinghamshire

Worksop STW SludgeDigestion

Arboricultural Report

September 2011Severn Trent Water

245212 EVT BNI 001 P1

P:\Leeds\EVT\Admin\Southampton Projects\Projects\01 Current\245212 BA02 Worksop STW (J686) (35)\06 Report\Worksop Arboricultural

09 September 2011

Worksop STW Sludge Digestion

Arboricultural Report

September 2011

Severn Trent Water

Mott MacDonald, 2nd Floor, 2 Brewery Wharf, Kendell Street, Leeds LS10 1JR, United Kingdom T +44(0) 113 394 6700 F +44(0) 113 394 6701, W www.mottmac.com

Severn Trent Centre, 2 St. John's Street, Coventry, CV1 2LZ


Mott MacDonald, 2nd Floor, 2 Brewery Wharf, Kendell Street, Leeds LS10 1JR, United Kingdom T +44(0) 113 394 6700 F +44(0) 113 394 6701, W www.mottmac.com

Revision Date Originator Checker Approver Description A

9th September 2011

Rhys Lennon

Claire Uden

Kevin Leather

First Issue

B

9th September 2011

Rhys Lennon

Claire Uden

Giles Hewson

Second Issue

Issue and revision record

This document is issued for the party which commissioned it and for specific purposes connected with the above-captioned project only. It should not be relied upon by any other party or used for any other purpose.

We accept no responsibility for the consequences of this document being relied upon by any other party, or being used for any other purpose, or containing any error or omission which is due to an error or omission in data supplied to us by other parties

This document contains confidential information and proprietary intellectual property. It should not be shown to other parties without consent from us and from the party which commissioned it.

redacted for data protection redacted for data protection

redacted for data protectionredacted for data protectionredacted for data protection

redacted for data protection

245212/EVT/BNI/001/P1 09 September 2011 P:\Leeds\EVT\Admin\Southampton Projects\Projects\01 Current\245212 BA02 Worksop STW (J686) (35)\06 Report\Worksop Arboricultural Report_P2.doc


Chapter Title Page

Executive Summary 1

1. Introduction 21.1 Terms of Reference___________________________________________________________________21.2 Scope of Work and Tree Assessment Methodology __________________________________________21.3 Limitations of Survey __________________________________________________________________3

2. Tree Summary 52.1 Description of Trees __________________________________________________________________52.2 Overview of tree quality and value _______________________________________________________6

3. Implications for Proposal 73.1 Scheme Design ______________________________________________________________________73.2 Protection of Root Protection Area (RPA) __________________________________________________73.3 Tree Preservation Orders (TPO) and Conservation Areas (CA)_________________________________73.4 Proposed actions for the trees associated with this scheme ___________________________________8

4. Recommendations – preventing damage to retained trees 94.1 Risk to trees from general construction activities ____________________________________________94.2 Recommended Tree Protection during Construction _________________________________________94.3 Tree Works _________________________________________________________________________94.4 Root Protection _____________________________________________________________________104.5 Contactors Compliance _______________________________________________________________10

5. Conclusions 11

Appendices 12Appendix A. Drawings __________________________________________________________________________13A.1. Tree Constraints and Tree Protection Plan________________________________________________14Appendix B. Key to Tree Survey Schedule __________________________________________________________15Appendix C. Tree Survey Schedule________________________________________________________________16Appendix D. Root Protection Area Calculations ______________________________________________________17Appendix E. Temporary Protective Fencing _________________________________________________________18Appendix F. Glossary __________________________________________________________________________19Appendix G. References ________________________________________________________________________20

Content


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Mott MacDonald Bentley has been commissioned by Severn Trent Water to conduct an arboricultural survey to support the planning application for a proposed new sludge digestion scheme at Worksop Sewage Treatment works (STW), located east of Worksop, Nottinghamshire.

The survey and associated report has been undertaken in accordance with BS 5837:2005 Trees in Relation to Construction-Recommendations, which is designed to give ‘recommendations and guidance on the principles to be applied to achieve a satisfactory juxtaposition of trees, including shrubs, hedges and hedgerows, with structures’.

This survey is not, nor should be taken to be, a full or thorough assessment of the health and safety of trees on or adjacent to the site, and therefore it is recommended that detailed tree inspections are undertaken/commissioned on a regular basis by the land owner with the express purpose of complying with his/her duty of care and satisfying health and safety requirements.

Of the trees surveyed (one individual tree and three tree groups), one tree (T1) is to be removed to facilitate construction of the Scheme. Although visible from the B6079 and surrounding landscape, the removal of T1 will not have a significant arboricultural or landscape impact.

At the time of this report Bassettlaw District Council (BDC) confirmed no trees associated with this Scheme are subject to a TPO, however it is recommended that a final check (for TPO and Conservation Area status) is undertaken by the Contractors prior to any tree works being carried out.

Executive Summary


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1.1 Terms of Reference

Mott MacDonald Bentley has been commissioned by Severn Trent Water to conduct an arboricultural survey to assess the impact to existing trees onsite from the proposed new sludge digestion scheme at Worksop Sewage Treatment Works, located east of Worksop, Nottinghamshire.

The proposed scheme is to include the installation of various items of process plant, housed-in tanks and buildings and a sludge cake storage pad. The facility will receive indigenous sludge from Worksop STW and also imported sludge from other sewage treatment works in the region. The facility will be accessed via a new single lane access road from the B6079 Retford Road.

1.2 Scope of Work and Tree Assessment Methodology

The tree survey was carried out by a Mott MacDonald qualified Arboriculturalist on 15th July 2011 to assess the quality and value of the principal trees in or adjacent to the site footprint. The survey was undertaken in accordance with current national standards, in particular the guidelines set out in ‘BS 5837:2005 Trees in Relation to Construction-Recommendations’. The tree data contained within the Tree Survey Schedule was recorded by a visual survey from ground level and no invasive tree inspection measures were employed.

The objective of this report is to provide a balanced judgement of the site to allow the development to be integrated with the trees in this location. The assessment process categorises the trees onsite to select the trees appropriate for retention, reviews the options for incorporating these trees within the developed landscape and provides a methodology for tree protection during construction.

The recommended actions for the existing trees have been stated in Section 3, with the full Tree Survey Schedule and categorisation of the trees in their existing context stated in Appendix C. The Root Protection Area (RPA) calculations are provided in Appendix D.

The following information was recorded for each tree in accordance with BS 5837:2005: Common and botanical name, and height with a clinometer where possible. “(Est)” is stated against all

estimated figures; Stem diameter shown in millimetres in accordance with paragraph 4.2.6 (d) of BS 5837: 2005 (Trees in

Relation to Construction - Recommendations). The stem diameters of single stemmed trees were measured at 1.5 metres above ground level and multi-stemmed trees measured immediately above the root flare unless otherwise stated in the tree schedule;

Crown radii, measured approximately at each of the four cardinal points, to the closest 0.5 metres. Where it was not possible to measure a dimension, due to the proximity of site boundaries or physical obstructions, an estimated figure has been included and this is denoted as “(Est)”. For trees in groups, only mean crown diameters have been recorded;

The approximate height of the crown clearance above the adjacent ground level in metres. The origin (O) relates to the join between the main trunk and the lowest branch and part (P) relates to the lowest part of the crown (e.g. branch tips);

Physiological (P) and Structural (S) condition labelled as either ‘Good’, ‘Fair’, ‘Poor’ or ‘Dead’, to provide an indication of the general health and vitality of each tree or tree group. Where the condition has been stated as ‘Good’ no further qualification has been added. Where condition has been identified as ‘Fair’

1. Introduction


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or ‘Poor’, additional information has been added to qualify this classification. All other observations and supplementary information regarding the trees (i.e. not directly linked to condition assessment) have been entered within the ‘Comments and/or Recommendations’ column;

Retention category labelled as А, В, C or R in accordance with paragraph 4.3.1 and Table 1 of BS 5837. This gives an indication as to each tree's arboricultural, landscape and cultural value and significance, and also its suitability for retention in the context of the proposed redevelopment of the site. The sub-categories (1 - Arboricultural values; 2 - Landscape values and 3 - Cultural values, including conservation) are only included where considered necessary to clarify why a tree has been assigned to a particular retention category. These categorisation criteria are summarised below:

Category Description

Category A Trees of high quality and value whose retention is most desirable (suggested minimum contribution 40 years

Category B Trees of moderate quality and value whose retention is desirable if practicable (suggested minimum contribution 20 years

Category C Trees of low quality and value or limited long-term potential, which could be retained if not in conflict with development proposals or young trees with a stem diameter of less than 150 mm (suggested minimum contribution 10 years)

Category R Trees requiring removal irrespective of any development proposals due to significant structural defects, irreversible decline or with a very short-term life expectancy of less than 10 years

Age Class recorded as:

Abbreviation Age Class Description

Y Young Trees aged less than 1st third of their life expectancy

MA Middle Aged Trees within 2nd third of their life expectancy

M Mature Trees aged within final third of their life expectancy

OM Over Mature Trees declining or moribund trees of low vigour

V Veteran Specimens exhibiting features of biological, cultural or aesthetic value that are characteristic of, but not exclusive to, individuals surviving beyond the typical age range for the species concerned

Preliminary management recommendations relating to the surveyor’s observations, and/or in

anticipation of the site becoming a working area and a proposed development site, within the ‘Comments and/or Recommendations’ column.

1.3 Limitations of Survey

The survey only encompassed the trees likely to be affected by the proposed development (refer to Appendix A for extent of site).

This report is not, nor should be taken to be, a full or thorough assessment of the health and safety of trees on or adjacent to the site. It is recommended that a full tree survey should be undertaken on a regular basis to satisfy health and safety requirements. Previous management and/or surveys in relation to the health and safety of trees on this site have not been taken into account as part of this report.

The conclusions detailed in this report relate to the conditions found at the time of the survey. Any significant alteration to the site that may affect the trees present or have a bearing on the planning


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implications (including level changes, hydrological changes, extreme climatic conditions or other site works) will necessitate a re-assessment of the trees and the site.


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2.1 Description of Trees

The trees associated with this Scheme are of mixed species and include Ash (Fraxinus excelsior), Hawthorn (Crataegus monogyna), Lime (Tilia spp.), Oak (Quercus spp.) and Sycamore (Acer pseudoplatnus). Only one individual tree (T1 – refer to photo 2.2) has been surveyed in relation to the proposals and the remaining trees have been assessed as three groups (Groups A, B and C – refer to photos 2.1, 2.4 and 2.5).

The trees associated with this Scheme are predominately young and middle aged i.e. within the first and second third of their life expectancy, and are clustered into small groups in and adjacent to the site.

The majority of the trees associated with this Scheme have been assessed as Category B trees i.e. trees of moderate arboricultural quality and value. A sub-category of ‘2’ has been assigned in number of cases which identifies that the trees are visible within the surrounding landscape and have landscape value.

A number of the trees have been assessed as being of ‘fair‘ condition in relation to their physiological and/or structural properties, as the trees are predominately ‘open grown’ and may have received little or no management.

Photo 2.1:View of Existing Main Entrance (Group C) Photo 2.2:View of T1

2. Tree Summary


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Photo 2.3:View of across to railway viaduct Photo 2.4:View of Group A (located on railway embankment)

Photo 2.5: View of Group B Photo 2.6: View across to existing STW site

2.2 Overview of tree quality and value

Of the one individual tree and three tree groups surveyed, the following categories were assigned in accordance with BS 5837:2005 (Table 1 – Cascade chart for tree quality assessment):

Table 2.1: Summary of BS 5837:2005 tree categories assigned to the surveyed trees Tree Category Description Number surveyed

Category A Trees of high quality and value 0

Category B Trees of moderate quality and value T1, Group A and Group C

Category C Trees of low quality and value Group B

Category R Trees for removal 0


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3.1 Scheme Design

The proposed site layout for the Scheme is shown in Appendix A, and includes construction of a new access road to provide access across existing farmland into the site from the south. The proposed access track will result in the widening of the existing junction with the B6079. The initial section of track will be widened to 7.3m carriageway to accommodate two-way traffic which then tapers to a width of 4m providing single track access with passing places. The track will be bridged over the Chesterfield Canal (adjacent to the railway viaduct) to access the southern side of the existing site.

Minor infrastructure changes are also planned within the site, however these will be made within the confines of the existing footprint, and no trees are present in this location.

3.2 Protection of Root Protection Area (RPA)

Working anywhere in the vicinity to trees is likely to cause some root damage due to the fact that in the order of 80% of the roots of any tree will occur within the upper 600mm of the soil. Roots will spread out for a considerable distance from a tree, and may be encountered at a distance beyond the canopy spread of a tree. Where construction activities are proposed within the rooting zone of trees, the potential for significant damage exists.

Table 2 of BS 5837:2005 prescribes a methodology for the calculation of a Root Protection Area (RPA). The RPA represents the minimum area that should be retained undisturbed around a tree or trees for the avoidance of an unacceptable degree of root disturbance. The required RPA of a tree is calculated, and typically plotted as a circle (or where appropriate as a square of equivalent area) to determine constraints or the location of protective fencing. The actual shape of this area may then be adjusted to take account of local topography or any existing site features that may serve as restrictions to ‘normal’ root development.

No works shall be necessary within the Root Protection Areas of the existing trees, however all construction activity must be undertaken in accordance with the guidance stated in Section 4.4.

3.3 Tree Preservation Orders (TPO) and Conservation Areas (CA)

The primary measures which provide statutory protection to trees are Tree Preservation Orders (TPOs) and Conservation Area (CA) status. Where present, these measures determine that either, notification to the LPA (CA designations) or consent from the LPA (TPO designations) is required for any works that may affect trees or tree groups.

At the time of this report, Bassettlaw District Council (BDC) confirmed that no trees associated with this Scheme are subject to a TPO. No confirmation has been received in relation to the Conservation Area status of this site, however the recommendations stated within this report have been made with this potential designation in mind.

It is recommended that the Contractors undertake a final check (for TPO and Conservation Area status) immediately prior to any tree works being undertaken.

3. Implications for Proposal


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3.4 Proposed actions for the trees associated with this scheme

In considering the current detailed design for the Scheme, the following provides specific recommendations to ensure effective integration between this Scheme and the surrounding landscape.

Tree Ref Species Recommended Action

T1 Lime Fell – direct conflict with Scheme footprint (widening of existing junction with B6079). This tree is an individual mature specimen and is visible from the B6079 and surrounding landscape. However, removal of this tree will not create a significant impact from an arboricultural and/or landscape perspective, due to the surrounding topography, existing vegetation and the assessed value of the tree i.e. Grade B.

Group A Mixed: Ash and Sycamore Retain trees. The footprint of the earthworks (supporting access track) fall immediately adjacent to the fence line demarking the boundary with the railway embankment. Due to the location and size of the trees on the embankment (Group A) no arboricultural impact will occur.

Group B Mixed: Hawthorn and Sycamore Retain trees. The footprint of the earthworks (supporting access track) fall immediately adjacent to the fence line demarking the boundary with the land associated with the viaduct upon which these trees (Group B) are located. The average RPA for this group is a 3m radius. The closest point of the embankment supporting the access track occurs at the eastern end of this group and then tapers away from the line of these trees as the alignment approaches the bridge leading to the southern boundary of the site. Due to the location and size of the trees present in this location no arboricultural impact will occur.

Group C Mixed: Lime and Oak Retain trees. These trees fall within the ‘red line’ boundary of the planning application however are located a distance from the proposed infrastructure changes to be implemented within the main site and therefore will not be impacted by this Scheme.


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4.1 Risk to trees from general construction activities

Trees can be easily damaged by construction processes, with both the tree roots and the main structure of a tree susceptible to a range of impacts. Root damage can affect the anchorage and stability of the tree, as well as preventing or inhibiting the absorption of water and nutrients. Damage to the trunk and branches leaves the tree more exposed to disease and decay.

Activities that can cause damage to tree roots include: trenches alterations in soil level non-porous surfaces compaction of soil changes in soil hydrology root exposure soil pollution (i.e. oil spill, incorrect application of herbicide and/or other chemicals) fires

Activities that can cause damage to tree trunks and branches include: pressure from materials stored against trunks physical impact from plant and equipment incorrect pruning exposure of bark or leaves to chemicals damage to bark from mowers and strimmers

Any works associated with this Scheme that could affect the trees for retention, as described above, must be discussed with, and be approved by a qualified Arboriculturalist prior to commencement.

4.2 Recommended Tree Protection during Construction

No recommendations to install temporary protective fencing have been made due to the fact that the trees for retention in close proximity to the Scheme footprint (Group A and B) are currently separated from the works area by existing boundary fencing (post and rail/wire). Should these fence lines be removed or altered in any way during the works then installation of temporary protective fencing will be required in accordance with BS 5837:2005 (refer to Appendix E) and be approved by a qualified Arboriculturalist.

4.3 Tree Works

All tree works must comply with any restrictions imposed by the Local Planning Authority and any covenants or by-laws relevant to this site.

All tree works must be carried out in accordance with BS 3998:1989 Recommendations for Tree Work and current Arboricultural best practice.

It should be noted that the Contractor will be responsible under the Wildlife and Countryside Act 1981, the Conservation of Habitat and Species Regulations 2010, and the Countryside Rights of Way Act 2000, to

4. Recommendations – preventing damage to retained trees


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take all reasonable action to identify the presence of protected species including nesting birds, bats, dormice and reptiles in the works area/surroundings, and comply fully with the law in relation to impacts associated with any instructed works.

4.4 Root Protection

No works will be necessary within the Root Protection Areas of trees to be retained. However, due to the nature of the typical rooting zone it is likely that finer roots beyond the RPAs of some trees may be affected by construction processes. The following guidance must be followed to reduce the impact of the scheme: Soil levels around the base of retained trees are to be retained as existing; Approval from an Arboriculturalist must be sought for any works (excavation etc.) within the RPAs of the

existing trees; No dumping, storage of materials or access within the RPA of existing trees is to be permitted; and, No fires are to be permitted within 15m of any tree to be retained.

4.5 Contactors Compliance

The Contractor’s strict compliance and co-operation with all aspects of the recommended tree protection measures and arboricultural methodology is essential to ensure satisfactory co-existence of the existing trees (on and adjacent to the site) and the proposed Scheme.


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Of the one individual tree (T1) and three tree groups (Groups A, B and C) surveyed only one tree (T1) has been identified for removal to facilitate construction of this Scheme.

Of the three groups of trees, two groups (Groups A and B) are in close proximity to the works footprint, however both are set back from the Scheme footprint behind existing post and rail fences, and therefore no works will be undertaken within the RPAs of the existing trees.

The remaining tree group (Group C) is located to the north of the site immediately adjacent the existing site entrance. This location falls within the ‘red line’ boundary for the planning application however all planned works under this Scheme are located away from this area and no arboricultural impact will occur.

At the time of this report Bassettlaw District Council (BDC) confirmed no trees associated with this Scheme are subject to a TPO.

5. Conclusions


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Appendix A. Drawings _________________________________________________________________________ 13 Appendix B. Key to Tree Survey Schedule _________________________________________________________ 15 Appendix C. Tree Survey Schedule _______________________________________________________________ 16 Appendix D. Root Protection Area Calculations ______________________________________________________ 17 Appendix E. Temporary Protective Fencing_________________________________________________________ 18 Appendix F. Glossary__________________________________________________________________________ 19 Appendix G. References________________________________________________________________________ 20

Appendices


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Appendix A. Drawings


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A.1. Tree Constraints and Tree Protection Plan


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Appendix B. Key to Tree Survey Schedule


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N E S W

T1 Single N/a Lime Tilia spp. 14.5 928 6 9 6 7 Epic: Ground LevelWest side: 1.2m MA Good Fair

Prolific epicormic growth at the base, significant bark loss and dead section within branch (originating at 3m on NW) at location of previously split out limb; overhead lines run through the crown; hard standing associated with existing access present on east and north of tree approx. 1.5 to 2m from trunk base.

40+ B 2

Group A Group 6 Ash ( x3)Sycamore (x3)

Fraxinus excelsiorAcer pseudoplatanus 10 to 12 250 av NR NR NR NR Ground Level Y (late) Good Fair

Trees sided up on west for clearance to railway track; trees located towards the middle of embankment (ranges from 3 to 4m at the east end to 8m from the post and rail fence at the west end.

20 to 40 B 2

Group B Group 7 Hawthorn (x4)Sycamore (x3)

Crataegus monogynaAcer pseudoplatanus

3 to 46 to 8 250 av NR NR NR NR Ground Level MA Fair Fair Trees are located approx. 1m to the west of post and wire fence. 20 to 40 C 1

Group C Group East side gate: <10West side gate: 10-12

OakLime

Quercus spp.Tilia spp. 7 to 10 300 av NR NR NR NR <1 Y Good Good Located on both sides of the existing entrance gate located north of the site; set within

mown grassland. 40+ B 2

NR - Not recorded

CategoryLife Expectancy

Worksop STW Tree Survey Schedule

Branch Spread (Radius - m)Stem Diameter

(mm)Height (m)SpeciesNo. in groupSingle tree

orGroup

Crown Clearance (m)Tag Number / Tree Ref Comments / Management RecommendationsAge ClassScientific Name Physiological

ConditionStructural Condition

Appendix C. Tree Survey Schedule


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Root Protection Areas calculated in accordance with Table 2 of BS 5837:2005 Tree Species Stem Diameter

(mm) *RPA Circle Radius (m)

*RPA (m2) **20% offset value (linear m)

T1 Lime 928 11.1 125 2.23

Group A Mixed: Ash and Sycamore 250 av. 3 29 0.6

Group B Mixed: Hawthorn and Sycamore 250 av. 3 29 0.6

Group C Mixed: Lime and Oak 300 av. 3.6 41 0.7

* figure rounded up to next 1/10 ** 20% offset value is only applicable in certain circumstances as determined by an Arboriculturalist.

Appendix D. Root Protection Area Calculations


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Figure F.1: Excerpt from BS5837:2005 - Details of required scaffold framework for Temporary Protective Fencing

Permission to reproduce extracts from British Standard BS 5837:2005 Trees in relation to Construction -Recommendations is granted by BSI. British Standards can be obtained in PDF or hard copy formats from the BSI online shop: www.bsigroup.com/Shop or by contacting BSI. Tel: +44 (0)20 8996 9001, Email: [email protected].

Appendix E. Temporary Protective Fencing


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Adventitious Bud

Adventitious buds develop from places other than a shoot at the tip of a stem e.g. along a branch, often formed as a result of stress e.g. after the stem is wounded or pruned.

AGL (Above Ground Level)

Terminology (prefixed by a measurement) stated within the Tree Survey Schedule to reference the location/height of a particular tree feature or tree part

Co-dominant stem A stem that has grown in direct competition to the main stem and which has formed a substantial size influencing the appearance of the tree

Crown Lift The removal of the lowest branches, usually to a specified height. It can be used to allow more residual light and greater clearance underneath the canopy for vehicles etc.

Dieback Where branches are beginning to show signs of death usually at the tips of the crown

Epicormic growth Small branches that grow in uncharacteristic clusters around the base of a tree, usually as a result of bad pruning or other stress factor

Etiolated Tall, thin tree which has extended vertically without substantial lateral development. Usually as a result of competition for light from other species

'Hung up' branch A branch which has become detached from the tree but is prevented from falling to the ground by the presence of other branches within the crown

Included bark Where the bark on two adjoining branches or stems is growing tight together, forming a joint with limited physical strength

ms A multi-stemmed tree

Pollarding A method of tree management in which the main trunk of the tree is cut at a particular height, and the resulting branches are then cropped on a regular basis

Occluded Wound The overgrowth of a wound with (callus) tissue produced subsequently. RPA (Root Protection Area)

The theoretical rooting area of a tree defined by BS5837:2005 Trees in Relation to Construction - Recommendations

Topping Topping is a form of pruning that removes terminal growth leaving a 'stub' cut end. Topping causes serious health problems to a tree

Appendix F. Glossary


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British Standard BS 5837:2005 Trees in Relation to Construction – Recommendations; Amd. No. 15988; Corrigendum No 1; September 2005; ISBN 0 580 46418 0

British Standard BS 3998:1989 Recommendations for Tree Work; Amd.No 6549; December 1990; ISBN 0 580 17170 1

The National Joint Utilities Group, Issue 1 – 8th October 2007, Volume 4 - Guidelines for the Planning, Installation and Maintenance of Utility Apparatus in Proximity to Trees

Arboricultural Association, 1991, Leaflet 4 - Tree Management

Appendix G. References

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