Guidance Document for the Design, Siting and Operation of Earth-Lined Slurry/Effluent Stores

Guidance Document for the Design, Siting and Operation of Earth-Lined Slurry/Effluent Stores

Guidance Document for the Design, Siting and Operation of Earth-Lined Slurry/Effluent Stores

TABLE OF CONTENTS

1Introduction

1.1Introduction

1.2What is an earth-lined slurry/effluent store?

1.3ELS role in the storage of animal slurry and effluent

1.4Advantages and disadvantages of ELSs

1.5The need for a guidance document for ELSs

1.6Overview of guidance document

2Site characterisation: general overview

2.1Introduction

2.2Objectives of the site assessment

2.3Risk based approach

2.4Key environmental receptors

2.5Hazard characterisation

2.5.1General

2.5.2Typical characteristics of effluent

2.6Site suitability (general requirements)

2.6.1Site restrictions

2.6.2Minimum design requirements

3Undertaking the site assessment

3.1Introduction

3.2Approach to site assessment

3.3Collation of supporting information

3.3.1Preliminary consultation

3.3.2Collation of relevant environmental data

(i)General

(ii)Topography

(iii)Surface water

(iv)Geological and hydrogeological

(v)Flora, fauna and cultural heritage

(vi)Drainage

(vii)Public utilities

(viii)General planning

3.3.3Interpreting the results of the background information

3.4Visual assessment

3.4.1On-site hazard evaluation

3.4.2Visual assessment of receptors

(i)Topography and landscape fit

(ii)Cultural heritage

(iii)Human

(iv)Flora and fauna

(v)Surface water

(vi)Drainage systems

(vii)Groundwater

(viii)Climate

(ix)Soil and subsoils

3.4.3Interpreting the results of the visual assessment

3.5Trial holes

3.5.1General

3.5.2Conducting and logging the trial hole

3.5.3Interpreting the findings from the trial hole investigation

3.6Decision process and preparation of recommendations

4Regulatory procedure

4.1Introduction

4.2Relevant legislation

4.3Planning pre-consultation

4.4Planning permission/documentation

5Earth-lined slurry/effluent store design

5.1Introduction

5.2Preparation for the design

5.3Volume requirements

5.3.1Slurry and other liquid volumes requiring storage

5.3.2Precipitation and evaporation volume

5.4Configuration of an ELS

5.5Embankment design

5.6Subsoil liner design

5.6.1Scenario A

5.6.2Scenario B

5.6.3Scenario C

6Earth-lined slurry/effluent store construction

6.1Introduction

6.2Working conditions

6.3Site preparation

6.3.1Clearing the site

6.3.2Installation of water table lowering system

6.3.3Drainage system

6.4Embankment construction

6.5Subsoil liner construction

6.5.1Compaction of subsoils

6.5.2Compactive energy

6.5.3Some compaction specification guidance

6.6Final surfaces

6.7Filling/emptying and agitation points

6.8Access to ELS

6.8.1Tractor access

6.8.2Other access points

6.9Fencing

7Operation and maintenance

7.1Introduction

7.2Operation of the ELS

7.3Maintenance of the ELS

7.3.1What needs to be inspected?

7.3.2How often shall it be inspected?

7.3.3Why shall it be inspected?

(i)Liquid level in the ELS

(ii)Grass mat cover

(iii)Access/filling/emptying points

(iv)Fencing and gates

(v)Embankment examination

(vi)Equipment

7.3.4What is the recommended course of action if damage is observed?

(i)Store liquid level

(ii)Grass mat

(iii)Access/filling/emptying points

(iv)Fencing and gates

(v)Embankments and subsoil liner

8Health and safety

8.1Introduction

8.2Health and safety issues for slurry/effluent stores

8.3Health and safety concerns for ELSs

8.4Children and young persons

8.5General health and safety references for agriculture

9Appendix 1 Groundwater response matrix for ELSs

9.1Introduction

9.2Vulnerability rating and aquifer classification

9.3Groundwater response matrix for ELSs

10Appendix 2 Classifying a subsoil

10.1Introduction

10.2Atterberg limits

10.3Particle size distribution (PSD) test

10.4Utilising the PSD curve and Atterberg limits

10.5Subsoil field assessment tests

10.5.1Field assessment of grading

10.5.2Field assessment of plasticity

(i)Cohesion and plasticity of fine fraction of coarse soils

(ii)Toughness of fine soils

(iii)Dilatancy test

10.6Using results to classify subsoil

11Appendix 3 ELS capacity calculations

11.1Slurry production

11.2Regulatory slurry capacity requirement

11.3ELS storage capacity

11.4Net rainfall capacity calculation

11.5ELS liquid volume calculation (worked example)

12Appendix 4 Site assessment form

12.1General details

12.2Background information

12.3Visual assessment

12.4Trial hole

12.5Laboratory soil test results

12.6Sketch of site

13Appendix 5 Worked example

13.1General details

13.2Background information

13.3Visual assessment

13.4Trial hole

13.5Laboratory subsoil test results

13.6Sketch of site

13.7Sizing the Grange ELS

13.7.1Slurry capacity requirement

13.7.2Precipitation capacity requirement

13.7.3Overall ELS volume

13.8Subsoil liner design

14Appendix 6 References

1Introduction______9

1.1Introduction______9

1.2What is an earth-lined store?______9

1.3ELS role in the storage of animal slurry and effluent______10

1.4Advantages and disadvantages of ELSs______10

1.5The need for a guidance document for ELSs______10

1.6Overview of guidance document______11

2Site characterisation-general overview______13

2.1Introduction______13

2.2Focussing the assessment (in the context of the ELS concept)_____13

2.3Risk based approach______14

2.4Key environmental receptors______15

2.5Hazard characterisation______15

2.5.1General______15

2.5.2Typical characteristics of effluent______15

2.6Site suitability (general requirements)______16

2.6.1Site restrictions______16

2.6.2Minimum design requirements______17

3Undertaking the site assessment______18

3.1Introduction______18

3.2Approach to site assessment______18

3.3Collation of supporting information______18

3.3.1Preliminary consultation______18

3.3.2Collation of relevant environmental data______19

(i)General______19

(ii)Topography______19

(iii)Surface water______20

(iv)Geological and hydrogeological______20

(v)Flora, fauna and cultural heritage______21

(vi)Drainage______21

(vii)Public utilities______22

(viii)General planning______22

3.3.3Interpreting the results of the visual assessment______22

3.4Visual assessment______23

3.4.1On-site hazard evaluation______23

3.4.2Visual assessment of receptors______23

(i)Topography and landscape fit______23

(ii)Cultural heritage______24

(iii)Human______24

(iv)Flora and fauna______24

(v)Surface water______24

(vi)Drainage systems______24

(vii)Groundwater______25

(viii)Climate______25

(ix)Soil and subsoils______25

3.4.3Interpreting the results of the visual assessment______25

3.5Trial hole______26

3.5.1General______26

3.5.2Conducting and logging the trial hole______26

3.5.3Interpreting the findings from the trial hole______27

3.6Decision process and preparation of recommendations______27

3.7Assessment of storage requirements______28

4Regulatory procedure______29

4.1Introduction______29

4.2Relevant legislation______29

4.3Planning pre-consultation______29

4.4Planning permission/documentation______29

4.5Planning timescale______30

5Earth-lined store design______31

5.1Introduction______31

5.2Preparation for the design______31

5.3Volume requirements______31

5.3.1Slurry volume______31

5.3.2Precipitation and evaporation volume______32

5.4Configuration of an ELS______32

5.5Subsoil liner design______33

5.5.1Scenario A______33

5.5.2Scenario B______33

5.5.3Scenario C______34

6Earth-lined store construction______37

6.1Introduction______37

6.2Working conditions______37

6.3Site preparation______37

6.3.1Clearing the site______37

6.3.2Installation of water table lowering system______38

6.3.3Drainage system______38

6.4Embankment construction______38

6.5Subsoil liner construction______39

6.5.1Compaction of subsoils______39

6.5.2Compactive energy______40

6.5.3Some compaction specification guidance______41

6.6Final surfaces______41

6.7Filling/emptying and agitation points______42

6.8Access to ELS______42

6.8.1Tractor access______42

6.8.2Other access points______43

6.9Fencing______43

7Operation and maintenance______44

7.1Introduction______44

7.2Operation of the ELS______44

7.3Maintenance of the ELS______44

7.3.1What needs to be inspected?______44

7.3.2How often should it be inspected?______45

7.3.3Why should it be inspected?______45

7.3.4What is the recommended course of action if damage is observed?____45

8Health and safety______47

8.1Introduction______47

8.2Health and safety issues for slurry stores______47

8.3Health and safety concerns for ELSs______48

8.4Children and young persons______48

8.5General health and safety references for agriculture______49

9Appendix 1 Groundwater response matrix for ELSs______50

9.1Introduction______50

9.2Vulnerability rating and aquifer classification______50

9.3Groundwater response matrix for ELSs______52

10Appendix 2 Classifying a subsoil______55

10.1Introduction______55

10.2Atterberg limits______55

10.3Particle size distribution (PSD) test______56

10.4Utilising the PSD curve and Atterberg limits______56

10.5Subsoil field assessment tests______57

10.5.1Field assessment of grading______57

10.5.2Field assessment of plasticity______57

(i)Cohesion and plasticity of fine fraction of coarse soils______57

(ii)Toughness of fine soils______57

(iii)Dilatancy test______58

10.6Using results to classify subsoil______58

11Appendix 3 Slurry capacity calculations______62

11.1Slurry production______62

11.2Regulatory slurry capacity requirement______62

11.3ELS slurry/effluent storage capacity______64

12Appendix 4 Site assessment form______65

12.1General details______65

12.2Background information______66

12.3Visual assessment______67

12.4Trial hole______68

12.5Laboratory soil test results______69

12.6Sketch of site______69

13Appendix 5 Worked example______72

13.1General details______72

13.2Background information______73

13.3Visual assessment______74

13.4Trial hole______78

13.5Laboratory soil test results______80

13.6Sketch of site:______81

13.7Sizing the Grange ELS______81

13.7.1Slurry capacity requirement______81

13.7.2Precipitation capacity requirement______82

13.7.3Overall ELS volume______82

13.8Subsoil liner design______85

14Appendix 6 Proposed slurry storage regulations______87

15Appendix 7 References______92

LIST OF TABLES

Table 21 Objectives and implications of site assessment

Table 22 Key environmental receptors and issues

Table 23 Water quality of sample collected directly beneath compacted subsoil liner at pilot-scale ELS at Teagasc Grange Research Centre (Scully, 2005)

Table 31 Minimum subsoil requirements

Table 32 Desk study information and site assessment phases

Table 51 Minimum requirements for configuration of an ELS

Table 61 Ground pressure values for a sample of hydraulic excavators

Table 62 Compaction guidance using different compaction plant (Table in NRA 2005)

Table 71 Recommended inspection schedule for ELS

Table 72 Embankment and subsoil liner remediation guidance

Table 91 Vulnerability rating (DELG/EPA/GSI, 1999)

Table 92 Aquifer classification (adapted from DELG/EPA/GSI,1999)

Table 93 Matrix of groundwater protection zones (DELG/EPA/GSI, 2005)

Table 94 Response matrix for earth-lined slurry/effluent stores (ELSs)

Table 95 General groundwater response requirements for ELSs

Table 101 Toughness characteristics for characterising the toughness of fine soils (BS5930:1999)

Table 102 Field tests for classification of subsoils (GSI, 2001)

Table 111 Estimated quantities of neat excreta produced by different classes of livestock (av. weight animals) (adapted from Table 2, Schedule 2, GAPPW, 2005)

Table 112 Proposed zonal configuration under European Communities (Good Agricultural Practice for Protection of Waters) Regulations 2005 (adapted from GAPPW, 2005)

Table 113 Proposed zonal configuration under European Communities Good Agricultural Practice for Protection of Waters, 2005 (adapted from GAPPW, 2005)

Table 114 Average net rainfall during the specified storage period

Table 115 Worked example illustrating how the liquid capacity of an ELS may be calculated (H. Scully, 2005)

Table 131 Groundwater and bedrock information obtained for proposed ELS site from the Geological Survey of Ireland (

Table 132 Details of nearest online borehole record to proposed ELS

Table 133 Minimum requirements for ELS (S131, DAF, 2005)

Table 134 Teagasc Grange ELS dimensions

Table 135 Store design calculations for Teagasc Grange ELS

Table 136 Fencing requirements for Teagasc Grange ELS using S131

LIST OF FIGURES

Figure 51 Basic configuration of an ELS (H.Scully)

Figure 52 Scenario A, B and C options for design of compacted subsoil liner in an ELS (H.Scully)

Figure 61 Example of how the required minimum no. of agitation points for an ELS may be assessed

Figure 71 Example of embankment breach caused by overtopping of embankment.

Figure 72 Trees located within an ELS footprint (not permitted)

Figure 73 Erosion on the inner embankment face of an ELS caused by careless filling of store

Figure 101 Atterberg limits and related indices (Scully 2005)

Figure 102 Flow chart to aid in classification of subsoils in Ireland

Figure 111 Proposed zonal configuration under European Communities Good Agricultural Practice for Protection of Waters, 2005 (adapted from GAPPW, 2005))

Figure 131 Proposed ELS location (adapted from

Figure 132 Geometrical design for earth-lined slurry/effluent store (ELS) at Teagasc Grange Research Centre (H.Scully)

Figure 133 Scenario C ELS subsoil liner design (H.Scully)

Figure 134 Teagasc Grange ELS

1Introduction

1.1Introduction

This document outlines the principles and approach to the planning, assessment, design, construction and operation and maintenance of earth-lined slurry/effluent stores (ELSs) as detailed in Department of Agriculture and Food Specification S.131: Minimum Specification for Earth-Lined Slurry/Effluent Stores and Ancillary Works (S.131). It is designed to give information and guidance concerning all stages of ELS sizing, assessment, design and construction. Each section below outlines the scope and methodology of each stage and more detailed information is given in the relevant chapters. Agricultural activities and processes give rise to a range of liquid streams sources including animal slurries, silage effluent, dairy washings and dirty water. The safe management of these sources is an objective for all farmers. As a signatory to the EU Nitrates Directive (91/676/EEC), Ireland is obliged to introduce a series of control measures designed to reduce pollution by nitrate. Sufficient storage capacity for animal slurries mustshall be provided to enable safe management of slurries during closed periods and when slurry cannot be spread due to poor weather conditions. Conventional slurry storage infrastructure requires significant investment to make up the slurry capacity shortfall. ELSs are an internationally recognised form of storage for varying types of polluted liquids effluents including those of industrial and agricultural origin and can be used to successfully store animal slurry. It is important however, that the objective shall always be good environmental management of the slurry and effluent production on a farm. Before evaluating the capacity requirements for any store, the client shall make every effort to make their farming operation as efficient as possible by reducing the quantities of liquids requiring storage. Diverting as much clean water as possible away from dirty water streams is an example of how the storage capacity requirement may be reduced.

1.2What is an earth-lined slurry/effluent store?

ELSs are subsoil-based structures which are used as a method of slurry storage. They may be used to store neat, dilute or separated slurries and the storage and settlement of dirty water. ELSs are typically < 20 m wide, between 20 to 50 m in length and 2.5 to 3.75 m deep. The shape of an ELS is often governed by the location and the site characteristics. The tank is formed by excavating soil and subsoil to formation level and using the excavated or imported material to form surrounding banks and subsoil liner. A subsoil liner is installed to protect the surrounding environment. The size of the store must take into account the quantity of liquid which needs to be stored, precipitation falling on the store, evaporation from the store and the freeboard required.

1.3ELS role in the storage of animal slurry and effluent

In Ireland, effluent from agricultural activities is known to be a major contributor to the nutrient enrichment of watercourses. Under the EU Nitrates Directive, Ireland is required to reduce pollution by nitrates.By increasing the available slurry storage capacity on Irish farms, the possibility of enforcedneed for inappropriate landspreading is reduced, because farmers will have the capacity to await more favourable landspreading times when the risk of overland flow is reduced and the soil crop can gain maximum benefit from the nutrients contained in the slurry. By maximising the utilisation of slurry nutrients, the farmers will reduce his their requirement for chemical fertilisers. Efficient recycling of nutrients within the environment is encouraged. An ELS allows farmers to increase their slurry storage capacities and consequently improve his their farming practices.

1.4Advantages and disadvantages of ELSs

Advantages:

  • a sustainable design using local materials (where suitable)
  • slurry/effluent storage capacity on farms can be greatly increased
  • adaptable to the needs of the farmer
  • low cost maintenance requirements
  • does not pose a significant threat to the environment when designed and constructed properly

like all structures it requires planning permission but unlike other low cost systems, will not require a discharge licence.

  • good landscape fit, particularly on gently sloping sites
  • toxic gases are not emitted into confined spaces therefore there is a reduced risk to humans and animals

Disadvantages:

  • requirement for competent site analysis and characterisation skills
  • requirement for construction supervisor
  • there are sites which will be unsuitable for construction of an ELS
  • relatively high maintenance time
  • there is an inherent risk in all slurry/effluent stores of drowning by humans and animals.

1.5The need for a guidance document for ELSs

The main purpose of this guidance document is to provide comprehensive guidance for the design and construction of an ELS. While this document provides the design guidance, a separate specification document (S131) is available from the Department of Agriculture and Food for the construction of ELSs. Farmers are reminded that they have a duty under the Safety, Health and Welfare at Work Act, 2005 to provide a safe working environment on the farm, including farm buildings, for all people who may work or enter that farm. There is a further duty to ensure that any contractor, or person hired to do building work, provides and/or works in a safe environment during construction. The steps outlined in this guidance document, from the initial decision on the appropriateness of an ELS to the final installation process, involve a variety of choices at each stage. The choices made will reflect the particular approach of the designer for particular locations, but once the steps outlined are followed, the robustness and sustainability of the ELS is upheld. This document is targeted primarily at Local Authority planners, site assessors, construction supervisors, agricultural consultants and farm advisors. The guidance document is available on the website of the Department of Agriculture and Food (www.agriculture.gov.ie).

1.6Overview of guidance document

Chapter 2: Site characterisation: general overview

Chapter 2 gives a general outline of the methodology which is employed when carrying out a site characterisation, which includes a risk based assessment, general site suitability requirements and some minimum design requirements.

Chapter 3: Undertaking the site assessment

This chapter gives guidance on how to carry out a specific assessment of a potential site being considered for an ELS by collating and analysing data pertaining to site location, farming practices, soil and subsoil type, groundwater protection requirements and general planning information.

Chapter 4: Regulatory procedure

Chapter 4 summarises relevant national legislation and planning regulations pertaining to obtaining planning permission for an ELS.

Chapter 5: Earth-lined slurry/effluent store design

This chapter details the design requirements necessary to ensure that the ELS is constructed to best meet the needs of the farmer with minimum impact on the environment. Design details include tank volume, length, width, depth of slurry, precipitation and evaporation requirements, freeboard, inner and outer bank slopes, minimum bank width, overall tank footprint and requirements for subsoil liner which is based on the recommendations of the site assessment.

Chapter 6: Earth-lined slurry/effluent store construction

Chapter 6 details the steps required for construction of an ELS. These include site preparation, excavation, embankment and subsoil liner construction, filling, agitation and emptying points, fencing, tractor access and external bank finish.

Chapter 7: Operation and maintenance

Guidance on routine maintenance checks is given including embankment inspection and maintenance of freeboard levels.

Chapter 8: Health and safety

This section gives guidance on possible health and safety issues which may arise including information on fencing, gates, access points and appropriate signage.

Appendices

Appendix 1 gives a brief introduction to the groundwater protection response matrix for ELSs and describes how it may isbe utilised during site assessment and characterisation. Appendix 2 contains guidance on classifying a subsoil using BS 5930:1999. Appendix 3 tabulates excerpts from documents which assist the designer in calculating the required slurry storage capacity of the proposed ELS. Appendix 4 contains a full copy of the site characterisation form and Appendix 5 gives a worked example of how the assessor and designer utilise the specification and guidance document to investigate a proposed site, give recommendations on the site suitability and design an ELS. Appendix 6 contains the most up to date version of the Nitrates Directive Action Programme as reported by the Department of Environment, Heritage and Local Government. Appendix 6 contains the references used in the preparation of this document.

2Site characterisation: general overview

2.1Introduction

Earth-lined slurry/effluent stores (ELSs) are a specific approach to the storage of liquid animal manures and soiled water on farms. ELSs are a way of increasing the slurry storage capacity on farms that is not excessively expensive, but does not pose a significant threat to the environment. The decision to use an ELS will be made on an integrated evaluation of technological, environmental, economic, and logistical criteria, and personal preference on the part of the farmer, but the suitability or otherwise of the site will be of key importance in the decision making process. It is therefore important that a systematic and logical approach is followed to allow the suitability of the site to be assessed as early as possible in the decision process, so that time and expense is not wasted unnecessarily. Any development of an ELS will require planning permission. The Planning Authority will need to be provided with adequate information in a standard, easily understood and logical format to assess the proposed development. The following cChapters, 2 & 3 provide guidance on how to assess site suitability with the objective of collecting sufficient information to:

  • determine if the ELS can be developed on the site
  • demonstrate that the construction of an ELS will not create a negative impact on the environment
  • to provide adequate data to enable the optimal design to be achieved.

The approach is termed site characterisation. Site characterisation combines various assessments including desk study, visual assessment and site tests to satisfy the objectives.