Itchen Implementation NEP Scheme Pump Testing and Associated Investigations of the Candover and Alre Augmentation Schemes, Summer 2011
Total Page:16
File Type:pdf, Size:1020Kb
Itchen Implementation NEP Scheme Pump testing and associated investigations of the Candover and Alre augmentation schemes, summer 2011 Southern Water Services November 2012 Itchen Implementation NEP Scheme Notice This document and its contents have been prepared and are intended solely for Southern Water’s information and use in relation to Itchen Implementation National Environment Programme (NEP) Scheme. Atkins Ltd assumes no responsibility to any other party in respect of or arising out of or in connection with this document and/or its contents. This document has 260 pages including the cover. Document history Job number: 5099146.410 Document ref: 5099146/70/DG/119 Revision Purpose description Originated Checked Reviewed Authorised Date Rev 2.0 Draft for Client comment SJW MB BP PS 24/05/201 JG 2 MB Rev 3.0 Working versions for SJW, JG, MB July2012 update Rev4.1 Draft for EA review and SJW, JG, MB HG, MB BP BP August sign-off 2012 Rev 6.0 Final SJW, BP BP November 2012 Atkins Pump testing and associated investigations of the Candover and Alre augmentation schemes, summer 2011 | Version 6.0 | November 2012 Itchen Implementation NEP Scheme Table of contents Chapter Pages Executive summary 1 1. Introduction 3 1.1. Context of investigations 3 1.2. Aim of investigations 4 1.3. Specific objectives 4 2. Background 5 2.1. Catchment water uses 5 2.2. Augmentation schemes 7 2.3. Upper Itchen conceptual understanding 9 3. Approach 11 3.1. Hydrological background to 2011 11 3.2. Asset register and survey 11 3.3. Test programme 12 3.4. Monitoring programme 13 3.5. Start-up pumping tests 15 3.6. Pre-test activity 16 3.7. Pipeline model and set-up 18 3.8. Stakeholder engagement 18 4. Results and analysis 20 4.1. Pumping test diary 20 4.2. Borehole performance 21 4.3. Early time aquifer test analysis 23 4.4. Impact of long term pumping on groundwater levels 30 4.5. Impact of long term pumping on river flows 35 4.6. Impact of pumping on ecology 44 4.7. Candover pipeline assessment 45 4.8. Impact of pumping on water quality 48 4.9. Stakeholder engagement 51 4.10. Revised conceptual understanding 52 5. Conclusions & Recommendations 53 5.1. Overview of success of testing programme in meeting project objectives 53 5.2. Asset suitability for support for public water supply 55 5.3. Issues around ecology 56 5.4. Other considerations 56 5.5. Recommendations 57 References 61 Appendices 63 Appendix A. Asset Survey 65 A.1. Data Collection 65 A.2. Site Visit 65 A.3. Desktop Study 65 A.4. Site survey information 69 A.5. Condition Assessment 71 Appendix B. Water Quality Data 113 B.1. Pre-test water quality testing and results 113 Appendix C. Stakeholder Engagement 118 Atkins Pump testing and associated investigations of the Candover and Alre augmentation schemes, summer 2011 | Version 6.0 | November 2012 Itchen Implementation NEP Scheme C.1. Webpage 118 C.2. Frequently asked Questions 120 C.3. Press Release (Draft) 121 C.4. Media Coverage 123 Appendix D. Pipeline modelling 126 D.1. Tables for WANDA 127 D.2. Hydraulic Profile Scenario 1.BMP 138 D.3. Hydraulic Profile Scenario 2.BMP 139 D.4. Hydraulic Profile Scenario 3.BMP 140 D.5. Candover Schematic.pdf 141 Appendix E. Ecological Reporting 142 Appendix F. Section 32 Details 245 Tables Table 2-1 CAMS final resource availability status ............................................................................................. 5 Table 2-2 CAMS Water Resource Management Units ...................................................................................... 6 Table 2-3 Public Water Supplies located in the Itchen catchment .................................................................... 6 Table 2-4 Augmentation Licence Returns ......................................................................................................... 8 Table 3-1 Assumed pumping rates for augmentation scheme boreholes ....................................................... 12 Table 3-2 Gauging stations for stream flow monitoring ................................................................................... 14 Table 3-3 Outfall water temperature monitoring .............................................................................................. 15 Table 3-4 Pre-test water quality sampling ....................................................................................................... 17 Table 4-1 Pumping test diary: operational issues ........................................................................................... 20 Table 4-2 Yield, drawdown and specific capacity of abstraction boreholes .................................................... 22 Table 4-3 Calculated early time values of transmissivity and storativity for the Alre abstractions .................. 25 Table 4-4 Calculated early time values of transmissivity and storativity for the Candover abstractions ......... 26 Table 4-5 Pre-pumping groundwater levels for 1976, 1989 and 2011 tests ................................................... 27 Table 4-6 Alre borehole aquifer properties: comparison with previous test results ........................................ 28 Table 4-7 Candover borehole aquifer properties: comparison with previous test results ............................... 29 Table 4-8 Maximum drawdown recorded at observation boreholes close to abstraction sites during the test pumping ........................................................................................................................................................... 32 Table 4-9 Maximum drawdown recorded at observation boreholes during the test pumping ......................... 33 Table 4-10 Observation borehole distance to nearest abstraction .................................................................. 36 Table 4-11 Summary of principal regression parameters. The regression parameters highlighted green were those chosen to estimate natural stream flows ............................................................................................... 38 Table 4-12 Summary of principal regression parameters from the 1979 Candover Pilot scheme pumping tests. Only results for those gauging stations used for both the 1979 pumping tests and summer 2011 pumping tests are presented. Source: Southern Water Authority (1979) ....................................................... 38 Table 4-13 The total volumetric net gain at each gauging station for the pumping period.Note – Easton and Allbrook & Highbridge net gains are based on adjusted estimated natural flows. Where the net gain is less than zero, these are shown as <0, and where they exceed 100% the figures are shown in red. ................... 42 Table 4-14 The total volumetric net gain at each gauging station for the pumping period. Note: The values shown for Easton and Allbrook & Highbridge use the original (non-adjusted) estimated natural flows. Where the net gain is less than zero, these are shown as <0, and where they exceed 100% the figures are shown in red. ................................................................................................................................................................... 43 Table 4-15 Bishops Sutton flow gauging results (Source: EA, November 2011) ............................................ 44 Table 4-16 Candover pipeline test pumping pattern - 19th October 2011 ....................................................... 45 Table 4-17 Flow rates delivered with siphon - Scenario 1 ............................................................................... 46 Table 4-18 Flow rates delivered without siphon - Scenario 2.......................................................................... 47 Table 4-19 Flow rates delivered with siphon up to final air valve - Scenario 3 ............................................... 47 Table 4-20 Recorded flows during field tests .................................................................................................. 48 Table 4-21 Water quality sampling programme during 2011 pumping test ..................................................... 48 Table 4-22 Remaining PAH that cannot be attributed to Axford 1A or Wield 3A ............................................ 51 Atkins Pump testing and associated investigations of the Candover and Alre augmentation schemes, summer 2011 | Version 6.0 | November 2012 Itchen Implementation NEP Scheme Figures Figure 1.1 Study area Figure 2.1 Candover scheme detail Figure 2.2 Candover site plans Figure 2.3 Alre scheme study area Figure 2.4 Alre site plans Figure 2.5 Upper Itchen conceptual understanding Figure 3.1 Long-term groundwater levels showing 2011 in its historic context Figure 3.2 Groundwater responses to rainfall prior to the 2011 pumping test Figure 3.3 Long-term stream flows at River Itchen gauging stations Figure 3.4 Proposed test pumping programme Figure 3.5 Groundwater monitoring locations Figure 3.6 Surface water monitoring locations Figure 4.1 Pump test diary including actual abstraction and other pump activity Figure 4.2 Early time aquifer test analysis: Alre abstractions Figure 4.3 Early time aquifer test analysis: Candover abstractions Figure 4.4 Comparison of antecedent hydrological conditions: 1976, 1989 and 2011 test pumping periods Figure 4.5 Groundwater contours - After 6 days of pumping (29th September 2011) Figure 4.6 Groundwater contours – After 17 days of pumping (10th October 2011) Figure 4.7 Groundwater contours – After 28 days pumping: Maximum drawdown Figure 4.8 Regional comparison of 2011 test maximum drawdown with 1976 and 1989 results