Mornington Routine Maintenance - Arterial Drainage Maintenance Works
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Arterial Drainage Maintenance Works
Mornington Routine Maintenance
Appropriate Assessment: Stage 2
Natura Impact Statement
November 2020
1 Galway Business Park, Dangan, Galway H91A3EF
173 Ivy Exchange, Granby Place, Parnell Square West, Dublin 1
Work Order: 2514
Report Control Sheet FORM 214 Rev 003
BUSINESS MANAGEMENT SYSTEM
Client OPW
Project No. 2514
Project Title Mornington Routine Maintenance
Report Title Appropriate Assessment Screening Report
Rev. Status Authors Reviewed By Approved By Issue Date
- DRAFT S. Brady ND ES July 2020
- Updated S. Brady ND ES August 2020
Updated after
2.0 additional OPW S. Brady ND ES November 2020
comments
Report Control Sheet Page i
Report Control Sheet FORM 214 Rev 003
BUSINESS MANAGEMENT SYSTEM
Report Control Sheet Page ii
Mornington Routine Maintenance - NIS
EXECUTIVE SUMMARY
Ryan Hanley has been commissioned by the Office of Public Works (OPW) to provide environmental
consultancy services in relation to Mornington FRS operational activities.
Following the methodology outlined in Ryan Hanley (2014a), a screening assessment was conducted to assess
the likely significant effects on European sites of the proposed drainage maintenance activities in the
Mornington Arterial Drainage Scheme 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). Three “source >
pathway > receptor” chains were examined to assess the likely impact of drainage maintenance activities on
European sites; surface water, land and air, and groundwater pathways. The results of this screening exercise
identified that significant adverse impacts could not be excluded on the following European sites:
• Boyne Coast and Estuary SAC
• Boyne Estuary SPA
As a result, it was necessary to conduct a Stage 2 Appropriate Assessment to further examine the potential
direct and indirect impacts of the proposed works on the integrity and interest features of the above European
sites, alone and in-combination with other plans and projects, taking into account the site's structure, function
and conservation objectives.
Further examination of the potential sources of impact on the European sites above, looking at surface water
and land and air pathways and groundwater pathways was conducted. Where potentially significant
adverse impacts were identified, a range of mitigation and avoidance measures have been stipulated to help
offset them.
As a result of this Appropriate Assessment it has been concluded, that given the avoidance and mitigation
measures suggested, the proposed drainage maintenance operations in the Mornington Arterial Drainage
Scheme will not have a significant adverse impact on the above European sites.
NIS – Executive Summary Page ii
Mornington Routine Maintenance - NIS
Table of Contents
Executive Summary ........................................................................................................................................ii
1 Introduction ............................................................................................................................................ 7
1.1 Background ................................................................................................................................................................ 7
1.2 Legislative Context................................................................................................................................................... 7
1.3 Appropriate Assessment Process ........................................................................................................................... 7
1.3.1 Stage 1 - Screening for AA ............................................................................................................................... 8
1.3.2 Stage 2 - AA ........................................................................................................................................................ 8
1.3.3 Stage 3 - Alternative Solutions ......................................................................................................................... 8
1.3.4 Stage 4 - IROPI .................................................................................................................................................... 8
1.4 Methodology ............................................................................................................................................................. 9
1.4.1 Screening ............................................................................................................................................................... 9
1.4.2 Ecological Walkover Surveys .......................................................................................................................... 10
1.4.3 Consultation ......................................................................................................................................................... 11
2 Arterial Drainage Maintenance ............................................................................................................ 12
2.1 Background ..............................................................................................................................................................12
2.2 Drainage Maintenance Activities ........................................................................................................................12
2.2.1 Channel Maintenance Activities....................................................................................................................... 13
2.2.2 Structural Maintenance Activities .................................................................................................................... 15
2.2.3 Maintenance works considered outside of the Scheme Design Standards and outside of normal
Arterial Drainage Maintenance Works ....................................................................................................................... 15
2.2.4 Plant and Machinery ......................................................................................................................................... 16
2.2.5 Maintenance Access Corridors (MAC) and Working Zone ........................................................................ 16
2.2.6 Site Compounds (Welfare Facilities), Access Routes and Haul Roads .................................................... 16
2.2.7 Waste Output/Disposal ................................................................................................................................... 17
2.2.8 Working Hours ................................................................................................................................................... 17
2.2.9 Environmental Training ...................................................................................................................................... 17
2.2.10 Environmental Audits ..................................................................................................................................... 18
2.2.11 Environmental Guidance: Drainage Maintenance and Construction and Environmental Procedures
(EPs) 18
2.3 The Mornington Arterial Drainage Scheme.......................................................................................................19
2.4 Drainage Maintenance Works Proposed for the Mornington Arterial Drainage Scheme ......................20
3 Screening Assessment Results.............................................................................................................. 21
3.1 Introduction ..............................................................................................................................................................21
3.1.1 Surface Water Pathways................................................................................................................................. 22
NIS – Table of Contents Page iii
Mornington Routine Maintenance - NIS
3.1.2 Land & Air Pathways ........................................................................................................................................ 23
3.1.3 Groundwater Pathways ................................................................................................................................... 23
3.2 Screening Assessment Conclusions .......................................................................................................................24
4 European Sites within the Zone of Influence of Drainage Maintenance Activities ............................... 26
4.1 Introduction ..............................................................................................................................................................26
4.2 Boyne Coast and Estuary SAC (001957) ..........................................................................................................26
4.2.1 Qualifying Interests ........................................................................................................................................... 27
4.2.2 Conservation Objectives ................................................................................................................................... 27
4.3 Boyne Estuary SPA (004080) ..............................................................................................................................28
4.3.1 Qualifying Interests ............................................................................................................................................ 29
4.3.2 Conservation Objectives .................................................................................................................................... 29
4.4 Description of the Receiving Environment - Ecological Walkover Survey Results......................................32
4.4.1 Introduction .......................................................................................................................................................... 32
4.4.2 Habitats ............................................................................................................................................................... 32
4.4.3 Annex I Habitat Mapping ................................................................................................................................ 32
4.4.4 Non-Native Invasive Species ........................................................................................................................... 35
4.4.5 Protected Flora and Fauna .............................................................................................................................. 35
4.4.6 Bird Activity ......................................................................................................................................................... 35
4.4.7 Consultation Responses ..................................................................................................................................... 35
5 Appropriate Assessment ...................................................................................................................... 36
5.1 Introduction ..............................................................................................................................................................36
5.2 Identification of Potential Sources of Impact ....................................................................................................36
5.2.1 Potential Sources of Impact via Surface Water Pathways ....................................................................... 36
5.2.2 Potential Sources of Impact Via Land and Air Pathways .......................................................................... 37
5.2.3 Potential Sources of Impact via Groundwater Pathways .......................................................................... 38
5.3 Impact Assessment ..................................................................................................................................................39
5.3.1 Do-Nothing Impact............................................................................................................................................. 39
5.3.2 In-Combination Effects ...................................................................................................................................... 39
6 Avoidance and Mitigation Measures.................................................................................................... 48
6.1 Introduction ..............................................................................................................................................................48
6.2 Mitigation for Other Ecological Receptors ........................................................................................................48
6.3 Mitigation for Bridge/Structure Works .............................................................................................................50
7 Conclusions .......................................................................................................................................... 51
References ................................................................................................................................................... 53
NIS – Table of Contents Page iv
Mornington Routine Maintenance - NIS
List of Figures
Figure 1.1 The Appropriate Assessment Process (from Appropriate Assessment of Plans and Projects in Ireland -
Guidance for Planning Authorities. DEHLG, 2009)................................................................................................................ 8
Figure 1.2 Screening assessment process ............................................................................................................................... 10
Figure 2.1 Plane Bed to Low Gradient Channel in the Mornington Arterial Drainage Scheme ..................................... 14
Figure 2.2 Map of the Mornington Scheme .......................................................................................................................... 19
Figure 3.1 Channels with potential impacts via surface water pathways as referenced in the AA Screening ............. 22
Figure 3.2 Channels and Embankments with Potential Impacts via Land and Air Pathways as referenced in the AA
Screening .................................................................................................................................................................................... 23
Figure 3.3 Map of all channels, FRS Scheme and structures where significant likely effects may arise. ..................... 25
Figure 4.1 Habitat Map............................................................................................................................................................ 33
List of Tables
Table 2.1 OPW Drainage Maintenance Subcategories ...................................................................................................... 12
Table 3.1 Screening Report Conclusion .................................................................................................................................. 24
Table 4.1 Qualifying Interests of Boyne Coast and Estuary SAC (001957)................................................................... 27
Table 4.2 Qualifying Interests of Boyne Estuary SPA (004080) ...................................................................................... 29
Table 4.3 Conservation Objectives of Boyne Estuary SPA.................................................................................................. 29
Table 4.4 Annex I Habitats Recorded .................................................................................................................................... 34
Table 5.1 Potential Sources of Impact via Surface Water Pathways................................................................................ 37
Table 5.2 Potential Sources of Impact via Land and Air Pathways ................................................................................... 38
Table 5.3 Impact Assessment - Boyne Estuary SPA (004080)........................................................................................... 41
Table 5.4 Impact Assessment - Boyne Estuary SPA (004080)........................................................................................... 44
Table 6.1 Specific Mitigation Measures ................................................................................................................................. 48
Table 6.2 Specific Mitigation Measures for other Ecological Receptors........................................................................... 49
NIS – List of Tables & Figures Page v
Mornington Routine Maintenance - NIS
Abbreviations
COSD ----------------------------------Conservation Objective Supporting Document
DEHLG ----------------------------------Department of Environment, Heritage and Local Government
EPA ----------------------------------Environmental Protection Agency
GIS ----------------------------------Geographical Information System
GWB ----------------------------------Groundwater Body
GWD ----------------------------------Groundwater Dependent
IFI ----------------------------------Inland Fisheries Ireland
IROPI --------------------------------- Imperative Reason of Overriding Public Interest
NHA --------------------------------- Natural Heritage Area
NPWS ----------------------------------National Parks and Wildlife Service
OPW ----------------------------------Office of Public Works
SAC ----------------------------------Special Area of Conservation
SPA ----------------------------------Special Protection Area
SWD ----------------------------------Surface Water Dependent
WFD ----------------------------------Water Framework Directive
NIS – Abbreviations Page vi
Mornington Routine Maintenance - NIS 1 INTRODUCTION 1.1 Background Ryan Hanley has been commissioned by the Office of Public Works (OPW) to provide environmental consultancy services in relation to maintenance activities that will take place in 2020. This Natura Impact Statement (NIS) provides the results of the Appropriate Assessment conducted for the Mornington Arterial Drainage Scheme 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). A screening assessment has been conducted for the Mornington Arterial Drainage Scheme (Ryan Hanley, 2020). It determined that significant adverse effects on European sites are likely within the zone of influence of the proposed arterial drainage maintenance activities and so it moves to Stage 2 Appropriate Assessment. 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 this Directive 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 Special Protection Areas (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 European 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 (DEHLG) (2009) (revised February 2010). These guidance documents identify a staged approach to conducting an AA, as shown Figure 1.1. Natura Impact Statement Page 7
Mornington Routine Maintenance - NIS
Stage 1 Stage 2 Stage 3 Stage 4
Screening for AA AA Alternative Solutions IROPI
Figure 1.1 The Appropriate Assessment Process (from Appropriate Assessment of Plans and Projects in Ireland - Guidance for Planning
Authorities. DEHLG, 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 site’s 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 European 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 European 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.
Natura Impact Statement Page 8Mornington Routine Maintenance - NIS
1.4 Methodology
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 (2014a) The Office of Public Works, Arterial Drainage Maintenance Categories, Source
» Pathway » Receptor Chains for Appropriate Assessment. Prepared by Ryan Hanley Consulting
Engineers on behalf of the Office of Public Works.
▪ Ryan Hanley (2014b) Stage 1: Appropriate Assessment Screening Methodology for the Maintenance
of Arterial Drainage Schemes. Prepared by Ryan Hanley Consulting Engineers on behalf of the
Office of Public Works.
▪ Ryan Hanley (2014c) Office of Public Works Arterial Drainage Maintenance Service 2014-2018.
Source > Pathway > Receptor Chains for Appropriate Assessment. Unpublished Report.
1.4.1 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). The methodology
is based on source > pathway > receptor chain principles and involves assessing likely significant effects on
European (Natura 2000) sites within the zone of influence of the proposed drainage maintenance in relation
to three pathways:
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.
Natura Impact Statement Page 9Mornington Routine Maintenance - NIS
Figure 1.2 Screening assessment process
The screening process (Figure 1.2) 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 European Site. The Appropriate Assessment Screening report was produced on currently
available information.
1.4.2 Ecological Walkover Surveys
To further inform the Appropriate Assessment process, the OPW selected a number of channels within the
Mornington Arterial Drainage Scheme for assessment through the undertaking of an ecological walkover
survey. The main channel was surveyed with a particular focus on areas located in, or within 100m of, a
European site.
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).
▪ Ecological Surveying Techniques for Protected Flora and Fauna during the Planning of National Road
Schemes (NRA 2009).
▪ Fossitt, J. (2000). A Guide to Habitats in Ireland. The Heritage Council, Kilkenny (Fossitt 2000).
Habitats have been named and described following Fossitt (2000). Nomenclature for higher plants principally
follows that given in Webb’s An Irish Flora (Parnell and Curtis, 2012).
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 using QField (QGIS), and all information gathered was
provided to the OPW on a GIS database. The results of these surveys have informed this NIS where relevant.
Figure 4.1 in this report provides a map of field walkover survey area.
Natura Impact Statement Page 10Mornington Routine Maintenance - NIS 1.4.3 Consultation To further enhance understanding of the baseline of the scheme area, consultation has been undertaken with local representatives from Inland Fisheries Ireland (IFI) and the National Parks and Wildlife Service (NPWS). Local OPW officers were also contacted for further ecological information. 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. The findings of this assessment will be subject to consultation with the NPWS and IFI. Natura Impact Statement Page 11
Mornington Routine Maintenance - NIS
2 ARTERIAL DRAINAGE MAINTENANCE
2.1 Background
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 below (See also OPW (2019) Environmental
Guidance EP 1, Table 1.3 and 1.4), 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 Other Mulching embankment
Mowing embankment
Gate installation
Sluice maintenance
Bridge maintenance
Spraying with herbicide
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 F
Embankment Maintenance Bush cutting/Branch trimming D
Natura Impact Statement Page 12Mornington Routine Maintenance - NIS
Category Maintenance Type Code
Tree cutting E
Mulching F
Mowing F
Gate installation F
Structural Maintenance Sluice maintenance F
Bridge maintenance F
Bank protection C
Bush cutting/Branch trimming D
Tree cutting E
The following sections 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.
Natura Impact Statement Page 13Mornington Routine Maintenance - NIS 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, Water Treatment Plants and Waste Water Treatment Plants. 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
Mornington Routine Maintenance - NIS
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 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.
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. Pre-cast concrete elements are also used in some instances for repair of
structures.
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. Where bridge maintenance may be required, a Bridge Inspection Form
will be filled out by the Foreman, prior to the works. This will determine the need for further assessment and
potentially, any mitigation measures that may be required. See EP4 of the OPW (2019 Environmental
Guidance.
It is not known where bridges, sluice doors or structures may require maintenance on the Mornington Scheme.
Maintenance of bridges, structures and/or sluices will only occur within the scheme after following the relevant
environmental procedures as detailed in the OPW Environmental Procedures (OPW, 2019) and using specific
mitigation measures as defined in this document. This NIS does not include assessment for the removal,
demolition, replacement or erection of bridges, sluices or structures.
2.2.3 Maintenance works considered outside of the Scheme Design Standards and outside of normal Arterial
Drainage Maintenance Works
Occasionally, works are required that can be considered outside of the scope of the normal Arterial Drainage
Maintenance Works to maintain a scheme. Works considered outside of the normal scope of statutory arterial
drainage maintenance works are not assessed for impacts in this report. Works that could be considered
outside of the normal scope of works include those involving extensive bank protection measures, removal of
mature woodland; or significant bridge rehabilitation or replacement works or any other works within the
zone of influence of a European site that have not been discussed in this report.
Natura Impact Statement Page 15Mornington Routine Maintenance - NIS 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, weed cutting equipment, 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 2.2.6). 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 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 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 are 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 Natura Impact Statement Page 16
Mornington Routine Maintenance - NIS 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 through site visits and audits. A useful forum for knowledge sharing is the Foreman’s meeting which is typically held annually, although some years have been skipped. This meeting between IFI, the OPW’s environment section, and the on-site foremen presents new information and allows for discussion on environmental issues. 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 (EPs) (see section 2.2.10 for more details). Both sets of training were developed and delivered by Inland Fisheries Ireland (IFI). The formal approach to EDM Training was complimented with on-site training. Regular site visits with consultants and OPW’s Environment Section provided 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) was also carried out by the 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. More recently, an environmental training course was designed and provided by JBA to all OPW staff in 2017 and 2018. It was given in three different stages. Management staff 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 Natura Impact Statement Page 17
Mornington Routine Maintenance - NIS ecologically sensitive habitats and species, invasive non-native 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. Training in the completion of an Environmental Risk Assessment and Bridge Inspections from an ecological perspective, was designed and provided by JBA Consulting to OPW Foremen and selected engineering staff in 2018. Training with regard to the new OPW procedures, Environment Guidance: Drainage Maintenance and Construction was delivered in house by OPW Environment Section in June 2019. All relevant staff were trained in how to use the new Guidance and workshops on how to use Environmental Data EP6 proved useful. 2.2.10 Environmental Audits A portion of operational crews are audited annually by the OPW Environment Section and OPWs Environmental Consultants for the implementation of the Environmental Drainage Maintenance Guidance Notes (Ten Steps to Environmentally Friendly Maintenance) and the OPW’s Environmental Management Protocol and EPs. Auditing is carried 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 Guidance: Drainage Maintenance and Construction and Environmental Procedures (EPs) The OPW’s Environmental Guidance: Drainage Maintenance and Construction, Management Procedures 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 33 No. Environmental Procedures (EPs) are applied to the works. These EPs set out actions designed to eliminate, or substantially reduce likely impacts to identified species and their associated habitats. Environmental Procedures are broken down into the following: Section 1A Drainage Maintenance Planning Procedures (EP 1- 5) Section 1B, Drainage Maintenance Implementation Procedures (EP 6 – 13), including procures for the 10 Steps to Environmentally Friendly Maintenance, River Enhancement and Tree and Vegetation Management. Section 2 Construction Procedures (EP 14 – 17), including Construction and Environmental Management, Ecological friendly culverts ad water pollution management); Section 3 Invasive Species Procedures EP 18 A – D) including Procedures for general and high-level biosecurity and treatments; Section 4 Animal and Plant Procedures (EP 19-28) EP 19 Salmonid EP 20 Otter EP 21 Lamprey EP 22 Crayfish P 23 Badger EP 24 Bank Nesting Birds EP 25 Birds EP 26 Bats Natura Impact Statement Page 18
Mornington Routine Maintenance - NIS
EP 27 Rare Plants
EP 28 Fresh Water Pearl Mussel
Section 5 Habitat Procedures EP 30 – 33):
EP 30 Alluvial (Wet Woodland)
EP 31 Wetland
EP 32 Mudflat
EP 33 Floating River Vegetation Habitat.
All Environmental Procedures are available in the OPW’s “Environmental Guidance Drainage Maintenance &
Construction” (OPW. 2019).
This document can also be downloaded from https://www.opw.ie/en/media/environmental-guidance-
drainage-maintenance-and-construction-2019.pdf.
2.3 The Mornington Arterial Drainage Scheme
The construction of the Mornington Flood Relief Scheme was completed in 2012 according to the National
Arterial Drainage Maintenance List of Activities 2018 – 2021 (OPW, 2018). Under Section 37 of the Arterial
Drainage Act 1945, the OPW is statutorily obliged to maintain all rivers, embankments and urban flood
defences on which it has executed works since the 1945 Act, therefore, under the 1945 Arterial Drainage
Act. Maintenance will commence this year for the first time since completion of the scheme.
The Mornington Arterial Drainage Scheme, shown in Figure 2.2, is located on the coast of County Meath and
near the Louth border. It includes 3.936km of watercourse and c. 4.62km of embankment.
Figure 2.2 Map of the Mornington Scheme
Natura Impact Statement Page 19Mornington Routine Maintenance - NIS
2.4 Drainage Maintenance Works Proposed for the Mornington Arterial Drainage Scheme
Within the Mornington Arterial Drainage Scheme, the exact location and type of required maintenance
activity varies over time. This screening assessment is conducted on the assumption that all channels will be
maintained during a 5-year maintenance cycle. However, this Appropriate Assessment is based on more
detailed information provided on the timing, frequency and nature of maintenance operations to be conducted
on each channel. During the period 2021 to 2025 proposed maintenance activities for the channels in the
Mornington Arterial Drainage Scheme will include:
A - Silt and vegetation management
D - Brush cutting / branch trimming
E - Tree Cutting
F – Other (Mulching and mowing embankment, gate installation, sluice and bridge maintenance and
spraying with herbicide)
No aquatic vegetation cutting (activity B) is proposed to be undertaken during the period of 2021 to 2025.
It is currently not known if and where structural maintenance activities (F: Sluice and Bridge maintenance) as
detailed in Table 2-1, are proposed, and therefore it will be assumed that potentially these activities could
occur on all structures within the scheme area during the period of 2021 to 2025.
No High Impact invasive species were found during the ecological walkover survey; however, High Impact
Invasive Species may be encountered which require removal through pulling or cutting and / or treatment
with targeted herbicide spraying.
The spreadsheets in Appendix A provides full details of the drainage maintenance activities proposed for the
Mornington Arterial Drainage Scheme for the period 2021 to 2025.
Natura Impact Statement Page 20Mornington Routine Maintenance - NIS
3 SCREENING ASSESSMENT RESULTS
3.1 Introduction
An Appropriate Assessment screening assessment, addressing Stage 1 of the process, has already been
completed for Mornington Arterial Drainage Scheme (Ryan Hanley, 2020). This identified that likely
significant effects on European (Natura 2000) Sites 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 (Ryan Hanley,
2014a, b and c). This methodology is based on source > pathway > receptor chain principles and involves
assessing likely significant effects on European sites within the zone of influence of the proposed drainage
maintenance in relation to three pathways:
1. Surface Water
2. Land & Air
3. 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 a scheme could impact upon European sites.
Sites that had the potential to be impacted by the maintenance works were determined to be within the ZOI
and are as follows:
▪ Boyne Coast and Estuary SAC (001957)
▪ Boyne Estuary SPA (004080)
Natura Impact Statement Page 21Mornington Routine Maintenance - NIS
3.1.1 Surface Water Pathways
As a result of the screening assessment (Ryan Hanley, 2020) maintenance activities on those watercourses
shown in Figure 3.1 were identified as potentially resulting in significant adverse impacts on European sites
via surface water pathways. Specifically, the European sites that may be adversely impacted upon are:
▪ Boyne Coast and Estuary SAC (001957)
▪ Boyne Estuary SPA (004080)
Figure 3.1 Channels with potential impacts via surface water pathways as referenced in the AA Screening
Natura Impact Statement Page 22Mornington Routine Maintenance - NIS
3.1.2 Land & Air Pathways
As a result of the screening assessment (Ryan Hanley, 2020) maintenance activities on those watercourses
shown in Figure 3.2 were identified as potentially resulting in significant adverse impacts on European sites
via land and air water pathways. Specifically, the European site that may be adversely impacted upon is:
▪ Boyne Coast and Estuary SAC (001957)
▪ Boyne Estuary SPA (004080)
Figure 3.2 Channels and Embankments with Potential Impacts via Land and Air Pathways as referenced in the AA Screening
3.1.3 Groundwater Pathways
As a result of the screening assessment (Ryan Hanley, 2020) maintenance activities on those watercourses and
embankments shown in Figure 3.3 were identified as not resulting in significant adverse impacts on European
sites via groundwater pathways.
Natura Impact Statement Page 23Mornington Routine Maintenance - NIS
3.2 Screening Assessment Conclusions
The Screening Assessment (Ryan Hanley, 2020) identified that the sites detailed in Table 3.1 were likely to
be significantly affected by drainage maintenance operations undertaken within the Mornington Arterial
Drainage Scheme. These conclusions are based on the assumption that all drainage maintenance activities
are to be undertaken on all watercourses and structures during the life of the plan (2021-2025).
Table 3.1 Screening Report Conclusion
Pathway of Impact
Natura 2000 Site Comment
Surface Water Land and Air Groundwater
This site is designated for
range of qualifying
interests, which will be
impacted upon via
different pathways
depending on whether it is
surface water or
Boyne Coast and Estuary SAC Yes Yes No
groundwater dependent.
The majority of Annex I
habitats within the site will
be impacted upon by
land and air pathways
associated with drainage
maintenance works.
The special conservation
interests within the SPA
have the potential to be
impacted upon by
drainage maintenance
Boyne Estuary SPA Yes Yes No
activities through
disturbance within the
SPA, and impacts on
supporting habitats via all
three pathways
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