Office of Public Works Arterial Drainage Maintenance Works - …€¦ · - Nenagh Arterial Drainage...

Office of Public Works Arterial Drainage Maintenance Works - Nenagh Arterial Drainage Scheme 2018 - 2022

Stage 2: Natura Impact Statement

December 2017

Office of Public Works

Main Street

Headford

Co Galway

Ireland

2017s6456 - Office of Public Works - NIS Nenagh V1.0 .docx i

JBA Project Manager Tom Sampson 24 Grove Island Corbally Limerick Ireland

Revision History

Revision Ref / Date Issued Amendments Issued to

Draft Report / December 2017

Tony Brew

Contract This report describes work commissioned by the Office of Public Works by a letter dated 31/08/17. The Office of Public Work’s representative for the contract was Tony Brew. Tanya Slattery, Jon Harrison, Catalina Herrera and Laura Thomas of JBA Consulting carried out this work.

Prepared by .................................................. Tanya Slattery BSc MSc MSc (Res)

Ecologist

Reviewed by ................................................. Laura Thomas BA MRes PGCert CEcol MCIEEM

Chartered Senior Ecologist

Purpose This document has been prepared as a Draft Report for the OPW. JBA Consulting accepts no responsibility or liability for any use that is made of this document other than by the Client for the purposes for which it was originally commissioned and prepared.

JBA Consulting has no liability regarding the use of this report except to the OPW.

2017s6456 - Office of Public Works - NIS Nenagh V1.0 .docx ii

Copyright © Jeremy Benn Associates Limited 2017

Carbon Footprint A printed copy of the main text in this document will result in a carbon footprint of 247g if 100% post-consumer recycled paper is used and 315g if primary-source paper is used. These figures assume the report is printed in black and white on A4 paper and in duplex.

JBA is aiming to reduce its per capita carbon emissions.

Contents

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1 Introduction ............................................................................................................ 1

1.1 Background ........................................................................................................................ 1 1.2 Legislative context .............................................................................................................. 1 1.3 Appropriate Assessment Process ...................................................................................... 1 1.4 Methodology....................................................................................................................... 3

2 Project Description ................................................................................................. 6

2.1 Arterial Drainage Maintenance ........................................................................................... 6 2.2 Drainage Maintenance Activities ........................................................................................ 6 2.3 The Nenagh Arterial Drainage Maintenance Scheme and Proposed Works ...................... 11

3 Screening Assessment Results ............................................................................. 15

4 Existing Environment ............................................................................................. 21

4.1 General ecology of the site ................................................................................................ 21 4.2 Description of habitats present ........................................................................................... 21

5 Natura 2000 sites within the Zone of Influence of the works/scheme ................... 24

5.1 Introduction ........................................................................................................................ 24 5.2 Lough Derg Shannon SPA (004058) .................................................................................. 24

6 Appropriate Assessment........................................................................................ 26

6.1 Introduction ........................................................................................................................ 26 6.2 Identification of Potential Sources of Impact ...................................................................... 26 6.3 Impact Assessment ............................................................................................................ 29 6.4 Impact Evaluation ............................................................................................................... 32

7 Avoidance and Mitigation Measures ...................................................................... 37

8 Conclusions ........................................................................................................... 39

References.......................................................................................................................... I

A Appendices ............................................................................................................ III

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List of Figures Figure 1-1: The Appropriate Assessment Process (from: Appropriate Assessment of Plans

and Projects in Ireland - Guidance for Planning Authorities, DoEHLG, 2009).. 2

Figure 1-2: Screening assessment process ...................................................................... 4

Figure 2-1 Extent of Nenagh Arterial Drainage Scheme .................................................... 12

Figure 3-1 Channels and embankments with potential impacts via surface water pathways ........................................................................................................................... 15

Figure 3-2 Channels and embankments with potential impacts via land and air pathways ........................................................................................................................... 17

Table 3-2 Summary results of QIs / FOIs with potential land and air connectivity, resulting in a potential for impact from the proposed works through land and air pathways ........................................................................................................................... 17

Figure 3-3 Channels and embankments with potential impacts via groundwater pathways ........................................................................................................................... 18

Figure 4-1 Reedbeds on bank of Lough Derg .................................................................... 22

Figure 4-2 Nenagh River .................................................................................................... 23

List of Tables Table 2-1: OPW Drainage Maintenance Subcategories ................................................... 6

Table 2-2: OPW Drainage Maintenance Types ................................................................. 6

Table 2-3 Channels at Nenagh, planned works and frequency of maintenance ................ 12

Table 3-1 Summary results of SWD QIs / FOIs with potential surface water pathways, potential Annex I habitats present and potential for significant impact ............. 16

Table 3-3 Summary of Natura 2000 habitats potentially present in the zone of influence of the works that may potentially be significantly impacted by the proposed works ........................................................................................................................... 19

Table 3-4 Summary of screening results for Nenagh scheme ........................................... 19

Table 4-1 Main habitats present at Nenagh Scheme ......................................................... 21

Table 5-1 Qualifying interests and their attributes for Lough Derg SPA ............................ 24

Table 5-2 List of pressures and threats to Lough Derg SPA .............................................. 25

Table 6-1 Potential pathways of impact to the attributes of the designated features of Lough Derg SPA .......................................................................................................... 26

Table 6-2 Impact evaluation table ...................................................................................... 32

Table 7-1 Specific mitigation measures for Nenagh Arterial Drainage Scheme ................ 37

Table 8-1 Integrity of Natura 2000 site checklist (DoEHLG 2009) ..................................... 39

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Abbreviations AA ................................... Appropriate Assessment

CA ................................... Competent Authority

COs ................................. Conservation Objectives

DoEHLG .......................... Department of Environment, Heritage and Local Government

EDM ................................ Environmental Drainage Maintenance

EPA ................................. Environmental Protection Agency

EREP .............................. Environmental River Enhancement Programme

FOI .................................. Features of Interest

GIS .................................. Geographical Information Services

GWD ............................... Ground Water Dependant

HDPE .............................. High-density polyethylene

IFI .................................... Inland Fisheries Ireland

IRB .................................. International River Basin

IROPI .............................. Imperative Reasons of Over-riding Public Interest

I-WeBS ............................ Irish Wetland Bird Survey

MAC ................................ Machine Access Channel

NIS .................................. Natura Impact Statement

NBDC .............................. National Biodiversity Date Centre

NPWS ............................. National Parks and Wildlife Service

OPW ............................... Office of Public Works

PVC ................................. Polyvinyl chloride

RBMP .............................. River Basin Management Plan

SAC ................................. Special Area of Conservation

SOP ................................ Standard Operating Procedure

SPA ................................. Special Protection Area

SWD ................................ Surface Water Dependant

QI .................................... Qualifying Interests

WFD ................................ Water Framework Directive

WMU ............................... Water Management Unit

ZOI .................................. Zone of Influence

2017s6456 - Office of Public Works - NIS Nenagh V1.0 .docx 1

1 Introduction

1.1 Background

JBA has been appointed by the Office of Public Works (OPW) to provide environmental consultancy services in relation to statutory arterial drainage maintenance activities for 2018 - 2022 at Nenagh in County Tipperary. This includes preparing a Natura Impact Statement (NIS) report to present required information to the relevant Competent Authority (CA) to undertake Appropriate Assessment. Appropriate Assessment is required at this location due to the presence of Lough Derg Special Protection Area (SPA) in County Tipperary within the Nenagh Arterial Drainage Maintenance Scheme.

An initial screening assessment was undertaken at this location for the purposes of Appropriate Assessment by JBA in 2014 (JBA 2014a). This screening report defined the zone of influence of the works, screened Natura 2000 sites within this zone of influence for potential to be significantly impacted by the proposed works and identified the potential for the proposed works to have significant impact upon Lough Derg SPA in accordance with Article 6(3) of the Habitats Directive (Council Directive 92/43/EEC on the conservation of natural habitats and of wild fauna and flora). Due to the identification of potentially significant effects in relation to the proposed works at this location, this NIS has been prepared to further assess the impacts on the integrity of the relevant Natura 2000 site and devise appropriate avoidance and mitigation measures where necessary.

1.2 Legislative context

The Habitats Directive (Council Directive 92/43/EEC on the conservation of natural habitats and of wild fauna and flora) aims to maintain or restore the favourable conservation status of habitats and species of community interest across Europe. The requirements of these directives are transposed into Irish law through the European Communities (Birds and Natural Habitats) Regulations) 2011 (S.I. No. 477 of 2011).

Under the Directive a network of sites of nature conservation importance have been identified by each Member State as containing specified habitats or species requiring to be maintained or returned to favourable conservation status. In Ireland the network consists of Special Areas of Conservation (SACs) and SPAs, and also candidate sites, which form the Natura 2000 network.

Article 6(3) of the Habitats Directive requires that, in relation to European designated sites (i.e. SACs and SPAs that form the Natura 2000 network), "any plan or project not directly connected with or necessary to the management of the site but likely to have a significant effect thereon, either individually or in combination with other plans or projects, shall be subject to appropriate assessment of its implications for the site in view of the site's conservation objectives".

A competent authority (e.g. the OPW or Local Authority) can only agree to a plan or project after having determined that it will not adversely affect the integrity of the site concerned.

Under article 6(4) of the Directive, if adverse impacts are likely, and in the absence of alternative options, a plan or project must nevertheless proceed for imperative reasons of overriding public interest (IROPI), including social or economic reasons, a Member State is required to take all compensatory measures necessary to ensure the overall integrity of the Natura 2000 site. The European Commission have to be informed of any compensatory measures adopted, unless a priority habitat type or species is present and in which case an opinion from the European Commission is required beforehand (unless for human health or public safety reasons, or of benefit to the environment).

1.3 Appropriate Assessment Process

Guidance on the Appropriate Assessment (AA) process was produced by the European Commission in 2002, which was subsequently developed into guidance specifically for Ireland by the Department of Environment, Heritage and Local Government (DoEHLG) (2009). These guidance documents identify a staged approach to conducting an AA, as shown Figure 1-1.


Figure 1-1: The Appropriate Assessment Process (from: Appropriate Assessment of Plans and

Projects in Ireland - Guidance for Planning Authorities, DoEHLG, 2009)

1.3.1 Stage 1 - Screening for AA

The initial, screening stage of the Appropriate Assessment is to determine:

a. whether the proposed plan or project is directly connected with or necessary for the management of the European designated site for nature conservation

b. if it is likely to have a significant adverse effect on the European designated site, either individually or in combination with other plans or projects

For those sites where potential adverse impacts are identified, either alone or in combination with other plans or projects, further assessment is necessary to determine if the proposals will have an adverse impact on the integrity of a European designated site, in view of the sites conservation objectives (i.e. the process proceeds to Stage 2).

1.3.2 Stage 2 - AA

This stage requires a more in-depth evaluation of the plan or project, and the potential direct and indirect impacts of them on the integrity and interest features of the European designated site(s), alone and in-combination with other plans and projects, taking into account the site's structure, function and conservation objectives. Where required, mitigation or avoidance measures will be suggested.

The competent authority can only agree to the plan or project after having ascertained that it will not adversely affect the integrity of the site(s) concerned. If this cannot be determined, and where mitigation cannot be achieved, then alternative solutions will need to be considered (i.e. the process proceeds to Stage 3).

1.3.3 Stage 3 - Alternative Solutions

Where adverse impacts on the integrity of Natura 2000 sites are identified, and mitigation cannot be satisfactorily implemented, alternative ways of achieving the objectives of the plan or project that avoid adverse impacts need to be considered. If none can be found, the process proceeds to Stage 4.

1.3.4 Stage 4 - IROPI

Where adverse impacts of a plan or project on the integrity of Natura 2000 sites are identified and no alternative solutions exist, the plan will only be allowed to progress if imperative reasons of overriding public interest (IROPI) can be demonstrated. In this case compensatory measures will be required.

The process only proceeds through each of the four stages for certain plans or projects. For example, for a plan or project, not connected with management of a site, but where no likely significant impacts are identified, the process stops at stage 1. Throughout the process, the precautionary principle must be applied, so that any uncertainties do not result in adverse impacts on a site.

Stage 1

Screening for AA

Stage 2

AA

Stage 4

IROPI

Stage 3

Alternative Solutions


1.4 Methodology

Data to be used in this assessment has been collected in a range of formats, from a range of sources, including:

• A comprehensive desktop survey (Section 1.4.1)

• The 2014 Nenagh Arterial Drainage Maintenance Screening Assessment (JBA 2014a) (Section 1.4.2)

• A number of ecological surveys (Section 1.4.3)

• National Parks and Wildlife Service (NPWS) website (http://www.npws.ie/) where site synopses, Natura 2000 data forms, GIS data and conservation objectives were obtained.

• The Irish Wetland Bird Survey (BirdWatch Ireland 2017)

• National Biodiversity Data Centre (NBDC 2017)

1.4.1 Desktop

This NIS has been prepared with regard to the following documents:

• DoEHLG (2009 rev 2010) Appropriate Assessment of Plans and Projects in Ireland Guidance for Planning Authorities. Department of the Environment, Heritage and Local Government (DoEHLG 2009).

• European Communities (EC) (2000) Managing Natura 2000 Sites: the provisions of Article 6 of the ‘Habitats’ Directive 92/43/EEC, Office for Official Publications of the European Communities, Luxembourg. European Commission (European Commission and Office for Official Publications of the European Communities 2000).

• EC (2002) Assessment of Plans and Projects Significantly Affecting Natura 2000 Sites: Methodological guidance on the provisions of Article 6(3) and (4) of the Habitats Directive 92/43/EEC, Office for Official Publications of the European Communities, Luxembourg. European Commission (EC 2002).

• EC (2007) Guidance document on Article 6(4) of the 'Habitats Directive' 92/43/EEC – Clarification of the concepts of: alternative solutions, imperative reasons of overriding public interest, compensatory measures, overall coherence, opinion of the commission. European Commission (EC 2007).

• EC (2013) Interpretation Manual of European Union Habitats. Version EUR 28. European Commission (EC 2013).

• Fossitt, J., (2000). A Guide to Habitats in Ireland. The Heritage Council, Kilkenny (Fossitt 2000).

• NPWS (2008). The Status of EU Protected Habitats and Species in Ireland. National Parks and Wildlife Service, Department of the Environment, Heritage and Local Government, Dublin, Ireland (NPWS 2008).

• NPWS (2014). The Status of EU Protected Habitats and Species in Ireland. Habitats Assessment Volume 2. National Parks and Wildlife Service, Department of the Environment, Heritage and Local Government, Dublin, Ireland (NPWS 2013a).

• NPWS (2014). The Status of EU Protected Habitats and Species in Ireland. Species Assessment Volume 3. Habitats Assessment Volume 2. National Parks and Wildlife Service, Department of the Environment, Heritage and Local Government, Dublin, Ireland (NPWS 2013b).

This report has been produced on currently available information, with the most up-to-date versions used.

1.4.2 Screening

The screening assessment conducted for these works has been undertaken in line with recommended guidance including that specifically produced for the OPW in 2014 (Ryan Hanley 2014b, 2014a). This methodology is based on source > pathway > receptor chain principles and involves assessing likely significant effects on Natura 2000 sites within the zone of influence of the proposed drainage maintenance in relation to three pathways:

http://www.npws.ie/


1. Surface water

2. Land & air

3. Groundwater

The screening assessment involves assessing the impacts of drainage maintenance operations within the arterial drainage scheme, and its zone of influence, in relation to each of the three pathways individually. The results of each pathway are then combined in a concluding section to identify if/where likely significant effects may arise.

Figure 1-2: Screening assessment process

The screening process uses a combination of GIS analysis and qualitative assessment to identify which drainage maintenance activities, on which specific watercourses, are likely to have significant effects on the integrity of Natura 2000 sites.

The screening report, conducted by JBA ecologists in 2014, has been reviewed and updated as necessary for the production of this NIS.

1.4.3 Ecological surveys

To inform the Appropriate Assessment process, a number of assessments and ecological surveys have been conducted, including:

• An ecological desk-based assessment to collate information on designated sites and protected and notable species, including bird survey data from the waterbird survey programme and the Irish Wetland Bird Survey (I-WeBS).

• An ecological walkover survey, including habitat survey, conducted on 25th and 26th of September 2017.

The ecological walkover survey was carried out in general accordance with the methods outlined in the following documents;

• Heritage Council (2011). Best Practice Guidance for Habitat Survey and Mapping (Smith et al. 2011).

• Phase 1 Habitat Survey methodology (Joint Nature Conservation Committee (JNCC), 1990, revised 2003).

• Ecological Surveying Techniques for Protected Flora and Fauna during the Planning of National Road Schemes (NRA 2009).

Further assessment

required

So

urc

e >

Path

way >

Recep

tor

Ch

ain

Surface water

Pathway present connecting

potential impacts to relevant Natura

2000 sites

Land & Air

Pathway present connecting

potential impacts to relevant Natura

2000 sites

Groundwater

Pathway present connecting potential impacts to relevant Natura 2000 sites


• Fossitt, J. (2000). A Guide to Habitats in Ireland. The Heritage Council, Kilkenny (Fossitt 2000).

Aerial photographs and site maps assisted the habitat survey. Protected species, including mammals (e.g. Otter, Badger) and birds, were surveyed based upon sightings and signs of activity during the habitat survey and also by the identification of potentially suitable habitats. This included a preliminary assessment of features with suitability for roosting bats and recording of any non-native invasive species found. All evidence of protected habitats and species was recorded on a tablet using the bespoke JBA GISmapp application where relevant, and all information gathered was provided to the OPW on a separate GIS database.

The results of these surveys have informed this NIS where relevant.

1.4.4 Consultation (if relevant)

The findings of this assessment will be subject to consultation with the NPWS.

This report has been produced on currently available information, with the most up-to-date versions used. Where new, or updated, information becomes available the OPW will consider and review the findings of this assessment, if necessary.


2 Project Description

2.1 Arterial Drainage Maintenance

Between 1945 and 1995, under the Arterial Drainage Act (1945), the OPW completed 34 Arterial Drainage Schemes on river catchments, along with five estuarine embankment schemes (over 11,500km of channel and 730km of embankments). The OPW is statutorily obligated to maintain arterial drainage channels under the 1945 Arterial Drainage Act, and since their completion, maintenance of these Arterial Drainage Schemes has been ongoing, with the majority of channels maintained every five years. However, larger channels tend to be only maintained every ten years, on average.

2.2 Drainage Maintenance Activities

Arterial Drainage Maintenance includes a range of operations such as silt and vegetation management, mowing and structure maintenance, as detailed in Table 2-1, and listed as channel, embankment or structure maintenance in Table 2-2 below. It is required to retain the arterial drainage scheme design capacity.

Table 2-1: OPW Drainage Maintenance Subcategories

Drainage Maintenance Subcategories

A Silt and vegetation management

B Aquatic vegetation cutting

C Bank protection

D Bush cutting/Branch trimming

E Tree cutting

F Mulching

G Mowing

H Gate installation

I Sluice maintenance

J Bridge maintenance

K Other

Table 2-2: OPW Drainage Maintenance Types

Category Maintenance Type Code

Channel Maintenance

Silt and vegetation management A

Aquatic vegetation cutting B

Bank protection C

Bush cutting/Branch trimming D

Tree cutting E

Other K

Embankment Maintenance


Tree cutting E

Mulching F

Mowing G

Gate installation H

Structural Maintenance

Sluice maintenance I

Bridge maintenance J

Bank protection C


Tree cutting E


The following sections, taken from Ryan Hanley (2014a) and OPW (2011a), provide further details on the types and nature of arterial drainage maintenance operations undertaken by the OPW.

2.2.1 Channel Maintenance Activities

The majority of drainage maintenance activities are focused on channel maintenance. While the frequency of maintenance on an individual channel may vary, with some channels requiring maintenance annually and others only requiring maintenance every twenty years, the average channel requires maintenance every four to six years. In this regard, approximately 2,000km of channels are maintained annually and nearly all of the 11,500km of channels across Irelands Arterial Drainage Schemes will have been maintained at least once over a period of five years. Channel maintenance is organised on a regional basis, with OPW Arterial Drainage Maintenance Regional Offices in Limerick, Headford, Co. Galway and Trim, Co. Meath.

Scheme Design Standards

Arterial Drainage Schemes constructed under the Arterial Drainage Act, 1945 were designed to provide an outfall for drainage of agricultural lands, and generally provided protection for a 3-year flood event. Where the creation of an outfall dictated the design bed levels, greater protection than the 3-year flood event was achieved as a consequence. In the case of modern flood relief schemes, flood protection for a 100-year flood event would be the design objective.

The original Scheme designs, including the outfall datum for each of the Arterial Drainage Schemes, are available in the relevant OPW Arterial Drainage Maintenance Regional Office. This includes the mapped Scheme design, and the associated long sections and cross sections. These designs are used to inform channel maintenance.

Types of Channel Requiring Maintenance

In the years following the construction of a drainage scheme there is a tendency for the channel capacity to be progressively reduced due mainly to the transportation and deposition of bed materials, the accumulation of silt and the growth of in-channel vegetation. The resultant channel maintenance consists of repetitive works of a cyclical nature, to restore the Schemes design levels i.e. outfall datum in order to maintain the channel's designed capacity to convey water.

Channels are prioritised for maintenance based on the rate of deterioration and the risk arising. The selection takes account of requests from the general public and potential flooding risk to roads, properties, urban areas and sewage works (OPW 2011a).

Plane Bed to Low Gradient Channels

Some 60 – 70% of maintained channels are of gentle longitudinal gradient and subject to relatively rapid deposition of silt, especially those that are subject to prolific growth of in-channel vegetation. The majority of maintenance works are therefore located on smaller lower-lying channels, with 90% of works in channels with a base width of


the banksides via bush cutting/branch trimming, tree cutting or mulching. This is undertaken between the 1st September and 28th February to avoid the residential bird nesting season (from the 1st March to 31st August as per the Wildlife Act (1976).

In contrast, in-stream works for silt and vegetation management are carried out outside of the salmonid spawning season (May to September) and the times that early life stages of salmonid fish will be present as per Section 173 of the Fisheries (Consolidation) Act (1959) on channels with salmonid spawning habitat. Any works required during this period are carried out in consultation with IFI. As a result, there may be a two stage approach to the works, with silt and in-stream vegetation management carried out during the open season (i.e. summer months), while woody vegetation removal is carried out in the winter months.

Other restrictions on works may also apply in relation to the presence/absence of other protected species such as White-clawed Crayfish and Sea, River and Brook Lamprey which will influence the timing of works.

2.2.2 Embankment Maintenance Activities

A total of 5 No. Estuarine Embankment Schemes were constructed under the 1945 Act. In addition, a number of the Arterial Drainage Schemes have embanked sections. Embankments are present within the Nenagh Arterial Drainage Scheme.

Scheme Design Standards

As above for the Arterial Drainage Schemes, Estuarine Embankment Schemes constructed under the Arterial Drainage Act 1945 were designed to provide an outfall for drainage of agricultural lands, and generally provided protection for a 3-year flood event. Where the creation of an outfall dictated the design bed levels, greater protection than the 3-year flood event was achieved as a consequence. In the case of modern flood relief schemes, flood protection for a 100-year flood event would be the design objective.

The original Scheme designs are available in the relevant OPW Arterial Drainage Maintenance Regional Office. This includes the mapped Scheme design, and the associated long sections and cross sections.

Types of Embankments Requiring Maintenance

All embankments and associated sluice structures (see section 2.2.3) are inspected annually for signs of disrepair.

Regular inspections are carried out on sections of embankments, which are known from experience to be at risk, together with additional inspections after a storm surge at sea or a high tidal/flood event. Maintenance of embankments includes removal of vegetation to allow for inspection of the embankment, and in some cases the replacement of existing fencing with gates to allow for future access during maintenance.

2.2.3 Structural Maintenance Activities

Structural Design Standards

During the construction of the Arterial Drainage Schemes under the 1945 Act, some 18,500 No. accommodation bridges were identified and modified, or replaced as required. These bridges provide farmers owning land on both sides of a channels with farm vehicular and/or foot access from one side to the other. The type of bridge provided depended on the width, depth and required flow capacity of the channel, and ranged from concrete piped culverts to relatively large structures formed on concrete or masonry abutments spanned by structural steel beams, or lattice girders together with concrete or timber decking.

During the Estuarine Embankment Schemes under the 1945 Act, existing sluice structures were identified and modified, or replaced as required. Additional sluice structures were constructed as required bringing the total number to approximately 750. The function of these sluice structures is to allow water from the floodplain behind the embankments to discharge to the main river or estuary.

Types of Structures Requiring Maintenance

In general, as channel maintenance proceeds, the bridges are examined by the supervisory industrial staff and if required, repairs/replacements are scheduled. The type of bridge structures, which are most likely to have fallen into a critical state of disrepair, are those with timber decking supported on steel beams, and those in which abutment foundations are being undercut. There is


a standard type of design for the replacement of these structures, which consists essentially of mass concrete abutments with reinforced cast in-situ decking. This type of structure is simple to construct and under normal circumstances, it will last for many years with little or no maintenance.

On many occasions, it is not necessary to totally replace a bridge, and repairs such as underpinning the foundation or replacement of wing-walls, parapets or sections of the deck may be all that is required to extend the useful life of the structure.

All embankments and associated structures are inspected annually for disrepair. Due to the time elapsed since scheme completion, some of these sluice structures have reached their design life and have started to fail. In this instance, full replacement is required. Typically, this involves the installation of pre-cast headwalls and back walls, and the replacement of existing corrugated galvanised steel pipes with PVC plastic pipes.

Sluice doors are the most frequent part of the sluice structure that are required to be repaired or replaced. Repairs to a sluice door consist of replacing the arms/hinges on the existing cast iron door. On occasion, the existing cast iron door would be replaced with a high-density polyethylene (HDPE) door. Blockages often occur at the doors of the sluices due to silt build up. These blockages are removed using along reach excavator working from the bank of the channel.

There is no maintenance planned on structures, including bridges and sluice doors, as part of the Nenagh Scheme. Further details on this are provided in Section 2.3.

2.2.4 Plant and Machinery

The types of machinery typically utilised during maintenance works would include 3600 hydraulic excavators (from 15-20 tonne excavators), mini-diggers, tractors and trailers, tipper lorries, hydraulic shears, hydraulic secateurs, chainsaws, mulchers and mowers; the machinery used is dependent on the maintenance activity being conducted.

The removal of dense in-stream silt and vegetation requires the use of a hydraulic excavator with a 1.5m wide (approximate) bucket (capacity approximate 500ltrs). For standard excavators, works progress at a rate of 700m to 900m per week. In relation to long-reach excavators, works progress at a slower rate of between 200m and 350m per week. Rates may change due to channel width or ground conditions.

2.2.5 Maintenance Access Corridors (MAC) and Working Zone

Maintenance sites are generally accessed via the public road and through farmland. A maintenance access corridor is utilised along one side of a channel for maintenance purposes. These established routes are used to track the hydraulic excavators for maintenance and for the disposal of spoil (see section 2.2.7). The same route is generally followed every maintenance cycle. This approach avoids disturbance of habitats on the opposite bank during works.

Where grasslands are present within the maintenance access corridor, the impact is predominantly temporary as the grasslands are trampled by machinery and can recolonise following completion of the maintenance activities. Within woodland and scrub habitats a linear path more typical of disturbed vegetation i.e. scrub/transitional woodland (WS1) will be evident along the maintenance access corridor due to regular machine access. In this regard, the disturbance regime associated with the tracking of plant machinery along the maintenance access corridors on the channel bank arrests succession to mature woodland such that scrub/transitional woodland (WS1) dominates. Where mature trees are present these are generally avoided by plant machinery.

Structures are generally accessed through farmland from the public road above. Plant machinery will utilise the same maintenance access corridor used for channel maintenance to gain access to the structure. Where individual trees, woodland and scrub habitats are present at the location of the structure, these may be removed to facilitate bridge inspection and works. Where mature trees are present these are generally avoided by plant machinery.

The location of drainage maintenance works is generally accessed via public roads and through farmland, with the siting of mobile short-term staff welfare facilities, plant storage and car parking agreed with local landowners. There is no requirement for temporary site lighting.

There is a requirement for water supply and disposal of wastewater from the welfare facilities (see section 2.2.7 in relation to waste disposal).


2.2.6 Site Compounds (Welfare Facilities), Access Routes and Haul Roads

Haul roads are generally not required to facilitate drainage maintenance activities. Where access is required in soft ground conditions, plant equipment will be brought in on tracks or temporary matting will be laid to provide a corridor for machinery access. Where matting is utilised, it will be completely removed post completion of works to allow vegetation to recolonise. All plant and machinery is confined to one defined access route to minimise disturbance.

All plant and machinery are regularly maintained and serviced to minimise release of hydrocarbons. All hydraulic excavators and other plant machinery use long life engine oil and biodegradable hydraulic oil. Fuelling and lubrication are conducted a minimum of 50m away from all channels. Spill kits are present in all plant used in maintenance activities. Integrated submersible pumps are also deployed in the event of structural maintenance and the requirement for dewatering of excavations.

2.2.7 Waste Output/Disposal

The material removed from a channel during silt and vegetation management is normally spread thinly along the bank or on top of existing spoil heaps where present within the access corridor. All dead wood material is left on site to decompose or is removed off site and utilised as firewood under local landowner agreements. Where mulchers or mowers are deployed, the arisings are left on site to decompose or the mulched material is buried.

Construction and demolition waste from structures includes broken concrete and stone. Steel railings are returned to the depot for recycling. Used engine oil and hydraulic oil is disposed of by a licensed waste handler. Toilet facilities are maintained by a licensed waste handler. Any waste generated on site is returned to the depot for segregation and disposal by a licensed waste handler.

2.2.8 Working Hours

All maintenance activities are undertaken during daylight hours. Standard working hours are 8.00am to 4.30pm, with lunch and tea breaks, Monday to Friday. There is no requirement for temporary site lighting to facilitate works. Machines are powered down when not in use.

2.2.9 Environmental Training

Environmental training of all staff involved in drainage maintenance is an ongoing process. Technical and Operational Staff have completed formal training in Environmental Drainage Maintenance (EDM) in 2004. This training course was revised and expanded under the OPW’s Environmental River Enhancement Programme (EREP) and was delivered to all staff in 2010. The training programme delivered included presentations in river corridor ecology, the Environmental Drainage Maintenance Guidance Notes (Ten Steps to Environmentally Friendly Maintenance), maintenance strategies involving both ‘enhanced maintenance’ and ‘capital enhancement’, and OPW’s Environmental Management Protocols and Standard Operating Procedures (SOPs) (see section 2.2.11 for more details). Both sets of training were developed and delivered by Inland Fisheries Ireland (IFI).

The formal approach to EDM Training is complimented with on-site training. Regular site visits from IFI and OPW’s Environment Section provide further guidance and advice to operational staff. Auditing of operational staff on the implementation of the Environmental Drainage Maintenance Guidance Notes (Ten Steps to Environmentally Friendly Maintenance (OPW 2011b) is also carried out by both IFI and OPW’s Environment Section.

In addition, other environmental training takes place as deemed beneficial, e.g. in 2008, the majority of the technical and operational staff were trained in Otter Awareness. This course, provided by the Department of Zoology, Trinity College Dublin, included presentations on Otter ecology, and on-site identification of Otter signs and suitable habitat.

In 2017 an environmental training course was designed and provided by JBA to all OPW staff. It was given in three different stages. Management were given a more detailed 2 day course in Environmental and Ecological training. Ground staff were given 1.5 days of training in the environment and ecology. Modules were designed to assist staff in understanding the relevant legislation, recognising ecologically sensitive habitats and species, non-native invasive species identification and general environmental and ecological training relevant to their work. This included a half day practical session where ecologists demonstrated the identification of the elements taught in the classroom, in the field.


2.2.10 Environmental Audits

A portion of operational crews are audited annually by the OPW Environment Section and IFI for the implementation of the Environmental Drainage Maintenance Guidance Notes (Ten Steps to Environmentally Friendly Maintenance) and the OPW’s Environmental Management Protocol and SOPs (Appendix A.5). Auditing is carried out separately by both IFI and OPW Environment Section on a rotational basis to ensure all operational crews are audited at least once every three years. All audit results are forwarded to the relevant Engineer for that Scheme within two working weeks. In the event of an audit showing elements of unreasonable non-compliance with procedures, the relevant Engineer will be notified within one working day. Audit results are also forwarded to OPW Systems Manager for inclusion in monthly regional benchmarking reports.

2.2.11 Environmental Management Protocol and Standard Operating Procedures (SOPs)

The OPW’s Environmental Management Protocols set out how regional management staff manage a range of environmental aspects, including programming of works to accommodate certain environmental windows or restrictions on timing of works, and recording of data. A total of 7 No. Standard Operating Procedures (SOPs) are applied during operational works. These SOPs set out actions designed to eliminate, or substantially reduce likely impacts to identified species and their associated habitats. These include:

• Environmental Drainage Maintenance Guidance Notes (10 Steps to Environmentally Friendly Maintenance)

• Lamprey SOP

• Crayfish SOP

• Otter SOP

• Mussel SOP

• Invasive Species SOP

• Zebra Mussel SOP

Appendix A.5 contains the OPWs Environmental Management Protocols and Standard Operating Procedures (OPW 2011b). This document can also be downloaded from http://www.opw.ie/en/media/OPW%20Environmental%20Management%20Protocols%20&%20SOPs%20April%202011.pdf

A draft Environmental Risk Assessment process has been developed by the OPW which will be filled in by the program producer for >3m base width main channels where maintenance has not occurred for 15 years and embankment works where maintenance has not occurred for 15 years. The Environmental Risk Assessment form for this process is in Appendix A.3.

2.3 The Nenagh Arterial Drainage Maintenance Scheme and Proposed Works

The Nenagh Arterial Drainage Scheme is located in County Tipperary. It includes 223.7km of watercourse and 6.2km of embankment (Figure 2-1), including the Nenagh River. The location and OPW channel name of the relevant channels are provided in Appendix A.1.

http://www.opw.ie/en/media/OPW%20Environmental%20Management%20Protocols%20&%20SOPs%20April%202011.pdfhttp://www.opw.ie/en/media/OPW%20Environmental%20Management%20Protocols%20&%20SOPs%20April%202011.pdf


Figure 2-1 Extent of Nenagh Arterial Drainage Scheme

Within the Nenagh Arterial Drainage Scheme the exact location and type of required maintenance activity varies over time. For the purposes of this NIS not all activities will occur on all Scheme channels, structures and embankments and only the following are planned for the Nenagh Scheme:

• A - Silt and vegetation management

• C - Bank Protection

• D - Bush cutting/branch trimming

• E - Tree cutting

Channels subject to planned works within the Nenagh scheme, are shown in Table 2-3. The location of each of these OPW channels are in Appendix A.1.

Table 2-3 Channels at Nenagh, planned works and frequency of maintenance

Channel Ref

Frequency of Maintenance

Year of Last Maintenance

A C D E

C1 10 26/07/2017

X

C1 10 26/07/2017

X

C1 4 26/07/2017

X

C1 10 26/07/2017

X

C1/1 4 15/02/2012 X

X

C1/10 4 30/11/2011 X

X

C1/11 4 28/03/2012 X

X

C1/11 4 28/03/2012 X

X


Channel Ref



A C D E

C1/12 4 16/07/2014 X

X

C1/13 4 17/07/2013 X

X

C1/14 4 20/05/2015 X

X

C1/14/1 4 12/05/2010 X

X

C1/14/1 4 12/05/2010 X

X

C1/14/1/A 4 19/05/2010 X

X

C1/14/2 4 17/04/2013 X

X

C1/15 4 10/04/2013 X

X

C1/16 4 13/03/2013 X

X

C1/16 4 13/03/2013 X

X

C1/16/1 4 06/03/2013 X

X

C1/16/2 4 13/03/2013 X

X

C1/17 4 30/05/2012 X

X

C1/17/1 4 02/05/2012 X

X

C1/17/2 4 09/05/2012 X

X

C1/17/2/1 4 02/05/2012 X

X

C1/17/3 4 16/05/2012 X

X

C1/17/4 4 23/05/2012 X

X

C1/18 4 01/05/2013 X

X

C1/2 4 12/12/2006 X

X

C1/3 4 15/07/2015 X

X

C1/4 4 01/07/2015 X

X

C1/4/1 4 08/07/2015 X

X

C1/4/A 4 24/06/2015 X

X

C1/5 4 17/06/2015 X

X

C1/6 4 12/08/2015 X

X

C1/7 4 29/07/2015 X

X

C1/8 4 22/07/2015 X

X X

C1/8 4 02/07/2015 X

X X

C1/8/1 4 29/07/2015 X

X

C1/8/2 4 19/11/2014 X

X

C1/8/2/1 4 19/11/2014 X

X

C1/8/5 4 17/12/2014 X

X

C1/8/6 4 20/04/2016 X

X

C1/8/6/1 4 26/05/2010 X

X

C1/9 10 19/07/2017 X X X X

C1/9 10 19/07/2017 X X X X

C1/9 10 19/07/2017 X X X X

C1/9 10 19/07/2017 X X X X

C1/9/1 4 11/02/2015 X

X

C1/9/10 4 07/09/2016 X

X

C1/9/11 4 29/06/2016 X

X

C1/9/12 4 05/10/2016 X

X

C1/9/2 4 05/07/2017 X

X

C1/9/2/1 4 22/02/2017 X

X


Channel Ref



A C D E

C1/9/2/2 4 08/03/2017 X

X

C1/9/2/3 4 29/03/2017 X

X

C1/9/2/4 4 03/05/2017 X

X

C1/9/2/5 4 10/05/2017 X

X

C1/9/2/6 4 17/05/2017 X

X

C1/9/2/7 4 24/05/2017 X

X

C1/9/2/8A 4 05/04/2006 X

X

C1/9/2/9 4 12/04/2006 X

X

C1/9/5 4 29/04/2015 X

X

C1/9/5/1 4 06/05/2015 X

X

C1/9/5/1/1 4 13/05/2015 X

X

C1/9/5/A 4 22/08/2012 X

X

C1/9/6 4 13/08/2014 X

X

C1/9/6/1 4 16/04/2014 X

X

C1/9/6/1/1 4 26/01/2011 X

X

C1/9/6/1/1 4 15/01/2014 X

X

C1/9/7 4 01/02/2017 X

X

C1/9/7/1 4

X

X

C1/9/8 4

X

X

C1/9/9 4 15/02/2017 X

X

C2 4 27/04/2016 X

X

C2/1 4 19/05/2010 X

X

C2/2 4 26/05/2010 X

X

C3 4 18/05/2016 X

X

C3/1 4 06/08/2014 X

X

C3/1/1 4 03/08/2011 X

X

C4 4 25/05/2016 X

X

C4/1 4 10/08/2005 X

X

C4/2 4 10/07/2002 X

X

C4/3 4 24/06/1994 X

X

D1 4 21/11/2007 X

X

D2 4 03/10/2007 X

X

D3 4

X

X

D4 4 07/09/2011 X

X

In terms of structural maintenance, no operations are planned as part of these works in 2018 - 2022. Therefore, any structural maintenance works on bridges and associated structures on those watercourses screened into the assessment (JBA 2014a) via each of the pathways are not included in this assessment.


3 Screening Assessment Results An Appropriate Assessment screening assessment, addressing Stage 1 of the AA process, has already been completed for the Nenagh Arterial Drainage Scheme (JBA 2014a). This identified that likely significant effects on a Natura 2000 site may occur as a result of the proposed maintenance activities and therefore a Stage 2 Appropriate Assessment is necessary.

The Stage 1 Screening Assessment was conducted in line with guidance produced for the OPW in 2014 (Ryan Hanley 2014b, 2014a). This methodology is based on source > pathway > receptor chain principles and involves assessing likely significant effects on Natura 2000 sites within the zone of influence of the proposed drainage maintenance in relation to three pathways:

4. Surface water

5. Land & air

6. Groundwater

The screening assessment involved assessing the impacts of drainage maintenance operations within the arterial drainage scheme, and its zone of influence, in relation to each of the three pathways individually. Conclusions were then drawn to identify which channels within the scheme that could impact upon the Natura 2000 site - Lough Derg Shannon SPA (site code: 004058).

3.1.1 Surface Water Pathways

As a result of the screening assessment (JBA 2014a) maintenance activities on those watercourses shown in Figure 3-1 including the Nenagh River, were identified as potentially resulting in significant adverse impacts on Lough Derg Shannon SPA via surface water pathways.

Figure 3-1 Channels and embankments with potential impacts via surface water pathways

This assessment was determined based on presence of surface water connectivity between the Natura 2000 site and the Nenagh Arterial Drainage Scheme, and considering a variety of factors. Relevant factors considered in the assessment included the "At Risk" status (Under the Water Framework Directive (WFD)) of all surface waterbodies within the area of works, the potential for impact, the significance of potential impacts and the relevance of any threats and pressures within the Natura 2000 site. Significance was determined based on the nature of the surface water


dependant (SWD) qualifying interests that may be present and the nature of the scheme based on the hydrological setting within the catchment. Pre-determined distances and typologies (Ryan Hanley 2014b) were used to define the zone of influence of the works and determine potential and significance of impacts.

Using the precautionary principle, during the screening assessment, SWD habitats and species that may be present were assessed as if present, based on information available in the Conservation Objectives, Natura 2000 Data Form and the Site Synopsis. These potentially present Qualifying Interests / Features of Interest were then assessed for the potential to be significantly impacted by the proposed works if present. The results of this assessment are in Table 3-1.

Table 3-1 Summary results of SWD QIs / FOIs with potential surface water pathways, potential Annex I habitats present and potential for significant impact

SWD habitats present

Annex I Habitat

Special Conservation Interest likely to occur

Desktop Study Comment

Conclusion

Lough Derg (Shannon) SPA (004058)

Mesotrophic standing waterbody (FL4) / Eutrophic Standing waterbody (FL5)

Natural Eutrophic lakes with Magnopotamion or Hydrocharition type vegetation (3150)

Tufted Duck Aythya fuligula [A061]

Goldeneye Bucephala clangula [A067]

Cormorant Phalacrocorax carbo [A017]

Common Tern Sterna hirundo [A193]

Wetlands and Waterbirds [A999]

No detailed information on location available, but species are likely to be present throughout Natura 2000 site.

Most of drainage maintenance activity is greater than 5km upstream of Natura 2000 site.


Figure 3-2 Channels and embankments with potential impacts via land and air pathways

This assessment was determined based on the location of the relevant Natura 2000 site and the Nenagh Arterial Drainage Scheme, and considering a variety of factors. Factors considered include the nature of the relevant site, the location of the pathways and any other site specific factors such as topographic features that might influence the magnitude of potential impacts from each potential pathway. Each qualifying interest of the SPA were then assessed individually for potential to be impacted and the overall assessment included a review of the potential for cumulative and/or in-combination impacts as a result of the identified pressures and threats identified in the Natura 2000 form (NPWS 2015). Pre-determined distances and typologies (Ryan Hanley 2014b) were used to define the zone of influence of the works and determine potential and significance of impacts.

As no detailed information was available on the location of qualifying interests, the precautionary principle was used during the screening assessment. Species that may be present were assessed as if present throughout based on information available in the Conservation Objectives, Natura 2000 Data Form and the Site Synopsis. These potentially present QIs / FOIs were then assessed for potential to be significantly impacted by the proposed works if present. The results of this assessment are in Table 3-2.

Table 3-2 Summary results of QIs / FOIs with potential land and air connectivity, resulting in a

potential for impact from the proposed works through land and air pathways

EU Code

Species/Habitats Maintenance activity location relative to Natura 2000 site boundary

Location of Impact

Result


A061 Tufted Duck Aythya fuligula

0km / Overlap MAC + 100m Potential Significant Effect

A067 Goldeneye Bucephala clangula



EU Code

Species/Habitats Maintenance activity location relative to Natura 2000 site boundary

Location of Impact

Result

A017 Cormorant Phalacrocorax carbo


A193 Common Tern Sterna hirundo


A999 Wetlands and Waterbirds


3.1.3 Groundwater Pathways

As a result of the screening assessment (JBA, 2014) maintenance activities on those watercourses, including the Nenagh River, shown in Figure 3-3 were identified as potentially resulting in significant adverse impacts on Lough Derg Shannon SPA via groundwater pathways.

Figure 3-3 Channels and embankments with potential impacts via groundwater pathways

This assessment was determined based on the location of the relevant Natura 2000 site within the same groundwater body as the Nenagh Arterial Drainage Scheme (Nenagh (IE_SH_G_178), and considering a variety of factors. Relevant factors considered in assessing the potential for the Natura 2000 site to be impacted through groundwater pathways also included the presence of Groundwater Dependant (GWD) QIs / FOIs, the risk status under the WFD of each site and the potential and significance of impact, should one occur. Each qualifying interest of the screened in Natura 2000 site, at this stage Lough Derg SPA, was then assessed individually for potential to be impacted and the overall assessment included a review of the potential for cumulative and/or in-combination impacts as a result of the identified pressures and threats identified in the Natura 2000 form (NPWS 2015). The location of the drainage maintenance activity works relative to the Natura 2000 site and features of interest were considered to determine relevance at this stage, along with GWD habitat typology. The Nenagh GWB is considered to be poorly productive bedrock and is of medium risk


(WFD /EPA 2016). Pre-determined distances and typologies (Ryan Hanley 2014b) were used to define the zone of influence of the works and determine potential and significance of impacts.

As no detailed information was available on the location of qualifying interests, the precautionary principle was used during the screening assessment. Species that may be present were assessed as if present throughout based on information available in the Conservation Objectives, Natura 2000 Data Form and the Site Synopsis. These potentially present QIs / FOIs were then assessed for potential to be significantly impacted by the proposed works if present. The results of this assessment are in Table 3-3.

Table 3-3 Summary of Natura 2000 habitats potentially present in the zone of influence of the works that may potentially be significantly impacted by the proposed works

Habitats as per Natura 2000 Standard Data Form, Site Synopsis or COSD

Potential GWB Habitats supporting SCIs Fossitt 2000 (Annex I)

Result


Mesotrophic standing waterbody (FL4) / Eutrophic Standing waterbody (FL5)

Natural Eutrophic lakes with Magnopotamion or Hydrocharition type vegetation (3150)

Potential for significant effect

Marginal swamp vegetation fringing lough [FS2]

Hydrophilous tall herb fringe communities of plains and of the montane alpine levels (6430)


Running Water [FW1, FW2] Watercourses of plain to montane water levels with the Ranunculion fluitantis and Callitricho-Batrachion vegetation (3260)


3.1.4 Summary of screening results

The screening of the proposed Arterial Drainage Works at the Nenagh Scheme assessed the Natura 2000 sites as shown in Table 3-4, to determine their potential to be significantly impacted by the proposed works due to the presence of Surface Water, Land and Air or Groundwater pathways using the methodology described in the Screening Methodology Report (Ryan Hanley, 2014a). The results of the screening assessment concluded that drainage maintenance activities proposed for the Nenagh Scheme have the potential to significantly impact upon Lough Derg SPA and further assessment, provided in the form of an NIS (this report) is required.

Table 3-4 Summary of screening results for Nenagh scheme

Site Pathway of Impact Comment

Surface Water

Land and Air

Ground water

All Saints Bog and Esker SAC (000566)

N N N No significant impacts, via any of the three pathways, have been identified as part of this assessment.

Bolingbrook Hill SAC (002124) N N N

Kilcarren-Firville Bog SAC (000647) N N N

Kilduff, Devilsbit Mountain SAC (000934)

N N N

Lough Derg, North-East Shore SAC (002241)

N N N

Lower River Shannon SAC (002165) N N N

Ridge Road, SW of Rapemills SAC (000919)

N N N

River Shannon Callows SAC

(000216)

N N N

Silvermine Mountains SAC (000939) N N N

Silvermines Mountains West SAC (002258)

N N N


Site Pathway of Impact Comment

Surface Water

Land and Air

Ground water

All Saints Bog SPA (004103) N N N

Dovegrove Callows SPA (004137) N N N


Y Y Y Drainage maintenance activities are proposed for within the Natura 2000 site, and upstream/ upgradient of it and have the potential to impact on features via all pathways.

Middle Shannon Callows SPA

(004096)

N N N No significant impacts, via any of the three pathways, have been identified as part of this assessment.

River Little Brosna Callows SPA (004086)

N N N

Slievefelim to Silvermines Mountains SPA (004165)

N N N

Note: N = No to potential pathway, Y = Yes to potential pathway


4 Existing Environment This section summarises the findings of the ecological walkover surveys of the embankments and channels at the mouth of the Nenagh River relative to the proposed 2018 - 2020 works for the Nenagh Arterial Drainage Maintenance Scheme. Habitats were identified to Fossitt level as per Fossitt (2000). Photographs of the embankments and habitats are included where appropriate.

4.1 General ecology of the site

The Nenagh Scheme area is located on the banks of Lough Derg, partially within the Lough Derg SPA. It includes depositing lowland rivers, embankments and drainage ditches. The majority of the surrounding land is improved agricultural grassland, except for along the banks of Lough Derg which includes a combination of woodlands, freshwater marsh, reedbeds and wet grassland.

The main habitats recorded are listed in Table 4-1 with descriptions, where necessary, in the below sections. A Fossitt habitat map is provided in Appendix A.2. Common Frog Rana temporaria, listed on Annex V under the Habitats Directive, Mute Swan Cygnus olor, an Amber Listed water bird and evidence of Badger Meles meles, protected under the 1979 Wildlife Act (and amendments) were observed using the channels to be maintained during the walkover survey, or within the zone of influence of the works. No Annex I habitats, protected under the Habitats Directive, were observed during the walkover survey.

No non-native invasive species listed on the third schedule of the EC (Birds and Natural Habitats) Regulations 2011 S.I. No. 477/2011 were recorded during the site visit. The National Biodiversity Data Centre records the aquatic invasive species Canadian Waterweed Elodea canadensis and Bloody-red Mysid Hemimysis anomala, as being present within 10 km of the area of works. Zebra Mussel Dreissena polymorpha have been identified previously as being present in Lough Derg.The terrestrial invasive species Ruddy Duck Oxyura jamaicensis, Greater White-toothed Shrew Crocidura russula, Mink Mustela vison, Musk Rat Ondatra zibethicus and Grey Squirrel Sciurus carolinesis as being present in the surrounding areas also.

A complete GIS database containing all species and habitats identified during the walkover surveys, including those relevant to the NIS and those not relevant but ecologically significant or protected under other legislation, has been provided separately to the OPW.

Table 4-1 Main habitats present at Nenagh Scheme

FOSSIT Level 3

BL3 - Buildings and artificial surfaces

FL4 - Mesotrophic standing waterbody

FS1 - Reed and large sedge swamps

FW2 - Depositing / lowland Rivers

FW4 - Drainage ditches

GA1 - Improved agricultural grassland

WL1 - Hedgerows

WL2 - Treelines

WN5 - Riparian woodland

WN6 - Wet willow-alder-ash woodland

WD2 - (Mixed) broadleaved/ conifer woodland

4.2 Description of habitats present

BL3 - Buildings and artificial surfaces

This includes a few buildings and a small access road leading to the dock. Maintenance works are not planned on any structures within the scheme, including these buildings, so they were not assessed for ecological significance e.g. as potential bat roosts.


FL4 - Mesotrophic standing waterbody

An aquatic survey did not take place as this was outside the scope of the survey, however, observations were made from the banks of the lake and this definition was determined as follows. Lough Derg was defined under the Lough Derg Site Synopsis as an eutrophic standing waterbody in the 1990s, as mesotrophic in the Lough Derg Water Management Unit (WMU) Action Plan in 2004 - 2006, as Oligotrophic in 2007 (WFD 2010) and in the Lough Derg SPA site synopsis most recently it is assessed as a mesotrophic system (NPWS 2014a).

The previously eutrophic nature of this lake is not believed to be natural and eutrophication has possibly been reversed due to the presence of the non-native invasive Zebra Mussel Drissena polymorpha (NPWS 2014a). Therefore, there is no potential for this habitat to correspond with the Annex I habitat Natural Eutrophic lakes with Magnopotamion or Hydrocharition type vegetation (3150).

Fringing vegetation included riparian woodland and reed and large sedge swamps as detailed further in the below sections.

FS1 - Reed and large sedge swamps

Reedbeds, dominated entirely by Common reed Phragmites australis, are present along the banks of Lough Derg (Figure 4-1).

Figure 4-1 Reedbeds on bank of Lough Derg

FW2 - Depositing lowland river

The Nenagh River is a depositing, lowland river with marginal vegetation composed of willowherbs Epilobium sp., Bur-reeds Sparganium spp., some reeds Phragmites australis and Fool's watercress Apium nodiflorum (Figure 4-2). Any floating river vegetation present on the Nenagh River was limited in species and tended to be distributed around bridges only. Due to the quality of the habitat and lack of key species, this habitat was assessed as not qualifying as the Annex I habitat


Watercourses of plain to montane levels with Ranunculion fluitanis and Calltricho-Batrachion vegetation (3260).

Figure 4-2 Nenagh River

FW4 - Drainage ditches

This drainage ditch was largely dry and separated from the Nenagh River by a hedgerow of Hawthorn Crataegus monogyna and Bramble Rubus fructicosus agg. The dry ditch had been invaded by Bramble in some places but was dominated by either by nettles Urtica dioica or Common Reed.

GA1 - Improved agricultural grassland

This habitat includes Perennial Rye-grass Lolium perenne, nettles and dock Rumex sp. It is the main habitat present inland from Lough Derg.

WL1 - Hedgerow

Hedgerow lines the banks of the Nenagh River and near Lough Derg. It tends to be wet and consists of Hawthorn, Bramble and Bindweed Calystegia sepium.

WL2 - Treeline

Treelines present include Alder Alnus glutinosa and Willow Salix spp. Non-native treelines composed of Leylandiiand Beech Fagus sylvatica are also present.

WN5 - Riparian woodland

Riparian woodland is present upstream, on both banks of the Nenagh River. It includes willows covered in Ivy Hedera sp., Hawthorn, Beech, Dog Rose Rosa canina, and an understory of Bramble and Nettle.

WN6 - Wet willow-alder-ash woodland

This habitat is present on the left bank and includes willows, Alder and Ash Fraxinus excelsior.

WD2 - (Mixed) broadleaved/ conifer woodland

This habitat is present on the edge of Lough Derg, surrounded by agricultural grassland and reedbeds.

https://www.google.co.uk/search?q=leylandii&spell=1&sa=X&ved=0ahUKEwjIiJmn2ePXAhWJDsAKHZNfA_oQvwUIJCgA


5 Natura 2000 sites within the Zone of Influence of the works/scheme

5.1 Introduction

This chapter provides baseline information on the Natura 2000 site within the Zone of Influence (ZOI) of the drainage maintenance activities (i.e. that screened into the assessment as detailed in Table 3-4). A description of the site is provided, along with details of the qualifying interests and conservation objectives and site vulnerabilities.

5.2 Lough Derg Shannon SPA (004058)

Lough Derg SPA is a lake on the River Shannon that crosses the counties of Tipperary, Galway and Clare, and varies between


Code Qualifying Interests Attributes

Taken from Conservation Objectives: Cork Harbour SPA 004030 (NPWS 2014b)

A061

Tufted Duck Aythya fuligula

Population trend - Long term population trend stable or increasing.

Distribution - No significant decrease in the numbers or range of areas used by waterbird species, other than that occurring from natural patterns of variation

Taken from Conservation Objectives: Lough Swilly SPA 004075 (NPWS 2011)

A067 Goldeneye Bucephala clangula

Population trend - Long term population trend stable or increasing.

Distribution - No significant decrease in the numbers or range of areas used by waterbird species, other than that occurring from natural patterns of variation


A193 Common Tern Sterna hirundo

Breeding population abundance: apparently occupied nests (AONs) - No significant decline in number of.

Productivity rate: fledged young per breeding pair - No significant decline in mean number.

Distribution: breeding colonies - No significant decline in number, location of or area.


A999 Wetland and Waterbirds Generic conservation objective: To maintain or restore favourable condition of the wetland habitat at Loug Derg (Shannon) SPA as a resource for the regularly-occurring migratory waterbirds that utilise it (NPWS 2016).

Habitat area - The permanent area occupied by the wetland is stable and not significantly declining - to include subtidal, intertidal, supratidal and lagoon habitats, other than that occurring from natural variation.

Adapted from Conservation Objectives: Lough Swilly SPA 004075 (NPWS 2011)

5.2.2 Site Vulnerabilities

Negative pressures or threats identified in the Standard Natura 2000 form for this site are listed in Table 5-2.

Table 5-2 List of pressures and threats to Lough Derg SPA

Threat or pressure Rank

Hunting Medium

Leisure fishing Medium

Nautical sports High

Fertilisation as a result of agriculture High


6 Appropriate Assessment

6.1 Introduction

The following chapter assesses the screened in Natura 2000 site in more detail and examines where adverse impacts may arise from the sources of impact identified above. The full impact assessment on these features is provided in Section 6.3. The screened in Natura 2000 site is as follows:

• Lough Derg SPA

Where potentially significant adverse impacts are identified, avoidance and mitigation measures are proposed to offset these impacts. These are discussed in the following sections.

Potential impacts that may occur to Lough Derg SPA and its features of interest include those that may arise as a result of disturbance to the key habitats and species during the works, those that may arise through the release of sediment through in-stream or riparian works, and those that may arise through accidental damage, trampling, physical loss of habitat or pollution events that may occur during the works. These impacts could occur through surface water, land and air or groundwater pathways.

As Lough Derg has been selected for breeding and wintering birds, disturbance during maintenance is possible due to the nature of the operations and the area where the works will occur.

Potential impacts to breeding birds, wintering birds and wetlands used by both wintering and breeding birds through disturbance, water pollution, sediment release and trampling or physical loss of habitat are considered in further detail as required. The following is a list of potential impacts that are considered in this assessment:

• Impacts to designated wetland habitats and bird species during maintenance, including disturbance and / or reduction in habitat quality due to physical disturbance or trampling;

• Direct effect on wetland habitats of the Natura 2000 sites due to changes in water quality and indirect effects on birds using the lake as a result of water quality;

6.2 Identification of Potential Sources of Impact

This section further examines the source > pathway > receptor chains that could potentially result in adverse impacts arising on the screened in Natura 2000 site in the Nenagh Arterial Drainage Maintenance Scheme; primarily informed by Ryan Hanley (2014a). Details of the possible pathways of impact (i.e. surface water, land and air, or groundwater) which have been identified as potentially affecting the screened in Natura 2000 site, its relevant conservation objectives and attributes are shown in Table 6-1. Reasoning for the decisions regarding potential pathways is discussed below in Section 6.2.1, Section 6.2.2 and Section 6.2.3. Surface water, groundwater and land and air pathways have been screened in as potential pathways for significant impacts to Lough Derg SPA and its features of interest in this assessment.

For a significant impact to occur, a pathway must be present to provide connectivity. Any negative changes to indicators of conservation value (e.g. water quality) within the Natura 2000 site must be considered. The main potentially significant impacts from the proposed works are on water quality, through disturbance and physical alteration, therefore those qualifying interests that occur within the zone of influence and may be impacted by these factors are considered further.

Table 6-1 Potential pathways of impact to the attributes of the designated features of Lough Derg SPA

Qualifying Interest Surface Water

Ground Water

Land and Air

Cormorant (Phalacrocorax carbo) ✓ ✓ ✓

Tufted Duck (Aythya fuligula) ✓ ✓ ✓

Goldeneye (Bucephala clangula) ✓ ✓ ✓

Common Tern (Sterna hirundo) ✓ ✓ ✓

Wetland and Waterbirds ✓ ✓ ✓


Wetland habitats are habitats that contain water, whether natural or artificial, permanent or temporary, static or flowing, fresh, brackish or marine. Wetland habitats that have been identified as being present, or potentially present within the Lough Derg SPA, include the Annex I habitats of 91E0 Alluvial forests, 3260 Floating river vegetation and 6430 Hydrophilous tall herbs. These habitats were not identified as being present within any of the areas of works during the ecological walkover survey (see section 4) and therefore, are not considered further within this report.

6.2.1 Surface Water

Surface water impacts, relevant to the proposed works of the scheme, can occur during the scheme works due to the nature of the work activity, or through accidental pollution events such as a fuel spillage.

Disturbance, caused by the use of heavy machinery or vehicles near the rivers and lake, along with rainfall can mobilise also solids and nutrients located on the site. Nutrients, suspended solids and spillages of fuel, could end up in Lough Derg if improperly managed during arterial drainage maintenance works.

Impacts from surface water pathways may occur during the works because of discharges containing silts, solids, oils, greases, anti-freeze and wood preservative. Discharges of silt laden waters to Lough Derg can cause clogging of spawning beds, smothering of plants and macroinvertebrates and overall, degradation or loss of valuable habitat. Chemicals such as fuels, oils and preservatives can directly poison aquatic life and cause harm or death of species. A reduction in the availability of prey species or suitable nesting and foraging habitat as a result of pollution events, may cause protected bird species to alter or abandon their usual foraging and breeding areas. Depending on the type and extent of the contamination event, protected birds and fish that they might prey upon could be directly poisoned.

Surface water runoff carrying increased sediment can cause changes to water levels and river morphology. Increased runoff, due to changes in runoff channels can also displace gravels and stones, damaging aquatic and associated riparian habitats along the shoreline.

Potential sources of impact via surface water pathways, as described above, can be summarised as follows:

• Release of suspended solids

• Release or changes in nutrient levels / pollutants

• Changes in water levels and channel morphology

There is potential for cumulative and in-combination effects through surface water pathways as a result of eutrophication from agriculture and sewage and through the spread of non-native invasive species, in particular Zebra Mussel and crayfish plague Aphanomyces astaci.

6.2.2 Groundwater

The birds of conservation interest at this site rely on the wetland habitats present for breeding, resting and foraging purposes. Any adverse impacts to these habitats will likely have a negative impact to the protected species and their conservation objectives. No specific groundwater dependant habitats were identified as being present during the walkover survey, however, surface water/groundwater exchanges may occur between surface water and groundwater bodies. Therefore, any impact that may occur through a surface water pathway could occur through a groundwater pathway also.

Groundwater impacts that could impact upon wetland habitats include release or changes in nutrient levels/pollutants, changes in water levels/channel morphology, changes to the groundwater catchment and groundwater flow paths and direct aquifer recharge from a stream bed in karst/fissured aquifer. The nature of these potential impacts through groundwater pathways are discussed further below.

• Release or changes in nutrient levels/ pollutants - this can arise from a variety of drainage maintenance activities, including removal of in-stream silt and vegetation, aquatic


vegetation cutting and bush cutting/ branch trimming. It can impact on GWD habitats indirectly through causing eutrophication (from mobile inorganics N03 and low mobility inorganics P04), or through pollution incidents from spillages or leaks (e.g. of fuel) during maintenance activities, which could then impact on groundwater quality through aquifer recharge. It can also impact indirectly on species, such as crayfish, lamprey, Salmon or birds, for example through reduced water clarity from eutrophication causing algal growth, or reduced water quality. Waterbirds of special conservation interest could be impacted indirectly by affecting food chains through increased algal growth and decreased invertebrate and algal diversity (i.e. the food source of the waterbirds).

• Changes in water levels/ channel morphology - this can arise from a variety of drainage maintenance activities, including removal of in-stream silt and vegetation, aquatic vegetation cutting and bush cutting/ branch trimming. It can also occur from maintenance activities that deepen and widen the channels back to their original level. This can impact on groundwater dependent habitats indirectly through:

o Increased capacity and flow in the channel leading to a reduction in water levels and hydrogeological impacts.

o Direct aquifer recharge from a stream bed in karst/fissured aquifer.

o Changes to the groundwater catchment and groundwater flow paths

o Lowering of channel water levels due to increased channel conveyance, which can increase the hydraulic gradient between the bankside groundwater table. This can potentially increase discharge from the channel and change the absolute value and pattern of variation in groundwater levels and potentially the location of groundwater divides. The distance from the channel at which an impact occurs is dependent on the subsoil and bedrock aquifer characteristics.

o It can also impact on species, such as fish, lamprey and waterbirds of special conservation interest by causing a loss of suitable habitat and impacting upon food chains through this loss/decline in quality of habitat.

There is potential for cumulative and in-combination effects through groundwater pathways as a result of eutrophication from agriculture and sewage.

6.2.3 Land and Air

The potential for impacts that may occur through land and/or air pathways are temporary and permanent impacts. Temporary impacts are those that may occur during the works and could include trampling of species or habitats, resulting in temporary damage. Permanent impacts are those that may occur during the works activities that will not return to their previous condition after the works and include loss of habitat or species.

The main impacts at this site through land and air pathways are noise, and visual and physical disturbance to waterbirds and wetland habitats. Impacts may also arise because of physical land alterations and / or a reduction in habitat area or quality. A loss of habitat quality may also occur through the introduction of non-native invasive species which have been recorded as being present in the adjacent areas.

• Disturbance - Birds designated within the Lough Derg SPA that may be using the site for commuting or foraging, are at risk from noise and visual disturbance, as well as physical disturbance. Disturbance that may occur without mitigation can be temporary one-off disturbances, which occur during the works, or permanent disturbance that may occur as a result of the works by causing physical alteration to a habitat or loss of an individual animal. Birds may temporarily avoid using the areas adjacent to the proposed development site due to noise and visual disturbance during the works and may choose alternative locations for foraging, breeding and social activities. Nesting birds may abandon eggs or young, should they be disturbed during the bird breeding season. Normal disturbance levels at this location are likely to include those caused by people and livestock only. Occasional machinery use may occur in areas adjacent to the SPA due to farmers operating as normal.

• Physical alterations to the habitat - these can be due to the physical removal of vegetation or the addition of spoil from the river beds, raising land levels along the embankment. This is particularly relevant along the banks of the rivers and drainage ditches which are within Lough Derg SPA.


• Reduction in area or quality of habitats - this impact may occur through the spread of non-native invasive species. The non-native invasive species Canadian Waterweed and the crustacean the Bloody-red Mysid, has been recorded in Lough Derg. More recently, the water mould Aphanomyces astaci, commonly known as Crayfish plague has been confirmed in the Lorrha River which feeds into the north of Lough Derg. Zebra Mussel has also been known to occur in Lough Derg. Unchecked, invasive non-native species can eradicate native crayfish species, replace native plant species that may provide food or cover for protected species or their prey and they can compete with native species for resources, reducing the amount of suitable habitat or food present. Zebra Mussel can change the nature of habitats, rendering them unsuitable for native species.

There is potential for cumulative and in-combination effects through Land and Air pathways from eutrophication from agriculture and sewage.

6.3 Impact Assessment

The main impacts that have the potential to occur as a result of the proposed works at the Nenagh River and associated embankments, include temporary impacts that occur during the works and permanent impacts that may occur as a result of the works. Temporary impacts include disturbance to birds, their prey and to wetland habitats, temporary impacts to water quality and physical alterations to habitats that will recover after the arterial drainage works finish. Permanent impacts include permanent loss of species and habitats, potentially permanent impacts to water quality and physical disturbance resulting in permanent loss of habitat. All potentially significant impacts are assessed to determine if they have the potential to adversely affect the integrity of t

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