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rsTPsA W A T o c L S r RELOCATION OF SUFFOLK WATER COMPANY BOREHOLE D SECCOMBE HYDROGEOLOGIST NATIONAL RIVERS AUTHORITY 13 August 1992 Table of Contents 1. Introduction .......................................................... 1 2. Description of problem ............................................... 1 3. Licence requirements of new s i t e ..................................... 2 4. Proposed locations ................................................... 3 Dairy Farm, North Lopham ......................................... 3 Lovers Lane, Garboldisham ......................................... 5 Yaxley Crag borehole 3 A 2 ......................................... 7 Cranley borehole 10A ................... .......... ..... 8 5. Catchment water balances ............................................. 9 R. Lt O u s e ........................................................ 9 R. D o v e ............................................................ H 6. Areas of Environmental interest .................................... 12 7. Conclusion............................................................ 14 8. Recommendations..................................................... 15 This book is due for return on or before the last date shown below. Don G>*(1 W*II L»d.. London. N.21 C»l. No. 1208 DG 02342/71 List of Figures Figure 1 - Monthly abstraction data for two boreholes adjacent to Redgrave F e n ........................................................16 Figure 2 - Location for cross-section of R. Lt. O u s e ................. 17 Figure 3 - Geological cross-section of R. Lt O u s e ..................... ..18 Figure 4 - Predicted Drawdowns for TM08/085 ............................ ..19 Figure 5 - Predicted drawdown for TM08/117 ............................ ..20 Figure 6 - Geological cross-section of R. D o v e ..........................21 Figure 7 - Predicted drawdown for Yaxley Crag 3 A ..................... ..22 Figure 8 - Predicted drawdown for Cranley 1 0 A ............................23 Figure 9 - River transfer calculation for R. Lt. O u s e ................. 24 Figure 10 - Total licence quantities for R. Lt. Ouse (33/42) ........... 25 Figure 11 - Stream hydrograph for R. Waveney at Ellingham............. 26 Figure 12 - Stream hydrograph for R. Dove at Oakley P a r k ............. 27 Figure 13 - Total licence quantities for R. Dove ( 3 4 / 1 7 ) ............. .. 28 List of Maps Map 1 - Location of borehole s i t e s .................................... 25 Map 2 - Location of S S S I ' s ............................................. 26 List of Appendices Appendix 1 - Hater level plot for April 1991 Appendix 2 - Details of TM08/085, Dairy Farm, North Lopham Appendix 3 - Details of TM08/117, Lovers Lane, Garboldisham Appendix 4 - Details of Yaxley Crag 3A, Hall Lane, Yaxley Appendix 5 - Details of Cranley 10A, Cranley, Eye Appendix 6 - Nett resource balance for R. Lt. Ouse catchment Appendix 7 - Nett resource balance for R. Dove catchment Appendix 8 - Details of known SSSI's Key to symbols used B Aquifer thickness (m) CCTV Closed circuit Television logging D Distance(m) Fe Iron K Permeability (m/day) MAC Maximum admissable concentration (EC guidlines) Mn Manganese Q Discharge (nr/day) r Radial distance from abstraction well (m) S Storage co-efficient SSSI Site of Special Scientific Interest T Transmissivity (nr/day) t Time (mins) tcmd 1000 nr/day W(u) Well function 1/s Litres per second flowrate pg/1 micrograms (10 ) per litre 1 1. Introduction This report is to investigate water resource implications of relocating a Suffolk Water Company borehole adjacent to Redgrave and Lopham Fens to one of four possible NRA boreholes. It is not intended to make any recommendations which will be influenced by budgetary constraints, but only to comment from a water resources viewpoint. 2. Description of problem Abstraction from two Suffolk Water Company boreholes (TM 04650 79200) adjacent to Redgrave and Lopham Fens has caused the water level within the fens to fall to an unacceptable level. Certain species of flora and fauna have been lost and others are in danger - case in point is the raft spider. Through various discussions between the NRA and Suffolk Water Company it has been agreed that the NRA would examine the feasibility in relocating the abstraction point from the existing site to one of the following sites - Dairy Farm, North Lopham NGR TM 0251 8361 NRA No. TM08/085 - Lovers Lane , GarboIdisham NGR TM 0011 8198 NRA No. TM08/117 - Yaxley Crag borehole 3A2 NGR TM 1205 7351 - Cranley borehole 10A NGR TM 1506 7232 The first two boreholes are part of the Great Ouse Groundwater Scheme and are used for river transfers to the Ely-Ouse scheme. The latter two are part of the Waveney Groundwater Scheme and are used for river support to Suffolk Water Company's Shipmeadow intake. The source of the Lt Ouse and Waveney Rivers is located near many SSSI sites. Therefore, in selecting an appropriate alternative site consideration has to be given to any likely effect extra pumping from either of the four sites would have on sensitive environmental areas. The alternative site may also have an effect on local abstractors and these will have to be considered as well. A map showing the location of the borehole in relation to the proposed sites is presented in Map 1. The location of all known SSSI's and environmentally sensitive areas is presented in Map 2. A water level contour was constructed for April 1991 - presented in Appendix 1. There is a good coverage of water level data within the Lt Ouse area, an average coverage within the Dove area, and a fairly sparse coverage between. However, there is a strong indication that the two GOGWS boreholes will affect the resources of the R. Lt. Ouse (with flow paths running in a westerly direction), while the remaining two boreholes will effect the resources of the R. Dove (with flow paths running in an easterly direction). National Rivers Authority - Relocation of Suffolk Water Company borehole 2 3. Licence requirements of new site The current licence which covers the abstraction from the boreholes adjacent to Redgrave Fen (7/34/16/*G/048) was issued ls‘ April 1969. The licence is an aggregate licence to cover the abstraction from Boreholes adjacent to Redgrave Fen TM 046 792 Abstraction limit = 3637 irr/day Borehole off Cranley Green Road, Eye TM 15447295 Borehole off Roman Road, Mendlesham TM 11756440 Boreholes at High Elm, Syleham TM 209 783 All annual combined abstraction must not exceed a total of 2500 tcma. Actual monthly abstraction data from 1967 to 1990 (inclusive) - see Figure 1 - was used to estimate the historical average annual use. The historical avaerage annual abstraction is estimated to be 2.8tcmd. Suffolk Hater Company have not as yet provided details of the annual abstraction rate for the new site. However, it has been assumed that the daily pumping rate will be 3.6tcmd and the drawdown effect will be based on continuous pumping for 200 days. It must be noted that if Suffolk Water Company abstracted on average 2.8tcmd then any pumping impact, as estimated for 3.6tcmd, would be much less. It is realised that pumping could last longer than 200 days, however, this limit is used to take into consideration the longest expected period of no recharge. National Rivers Authority - Relocation of Suffolk Water Company borehole 3 4. Proposed locations It has been proposed that there are four likely sites to be used as a replacement. These sites in detail are as follows. Dairy Farm, North Lopham NGR TM 0251 8361 NRA No. TM08/085 The 610mm diameter by 160m deep borehole is drilled through 29.0m of Drift (Boulder Clay; glacial sands and gravels) into chalk - see Appendix 2. The borehole was drilled in March 1985 by Smiths (Grimsby) as part of the Great Ouse Groundwater Scheme. The borehole has been acidised at 45 and 100m below ground level. A CCTV log was conducted prior to acidisation but is not available for inspection. The borehole is located approximately 5km from R. Lt. Ouse and within a relatively large extent of Drift. A geological cross-section for the Lt. Ouse and located through this site is presented - see Figure 3 for location and Figure 4 for the cross-section. This shows that the borehole is located within boulder clay overlying chalk. However, the aquifer is categorised as having a low sensitivity to pollution by nitrates leaching from agricultural soils. The water table (when drilled) is within the Drift and, with consideration to the drilling log, the aquifer is considered to be confined. There have been two pump tests. The first pump test was a four daily stage step/recovery test (each step lasting 480mins and recovery averaging 960mins). The maximum drawdown was 11.15m at a maximum discharge rate of 80.5 1/s. The. data was analysed (see Appendix 2.) using both the Bierschenk and Wilson method as well as the Eden and Hazel method. The results are as follows:- Bierschenk and Wilson Method (eiOmins) s = 0.001182Q + 0.0000003703Q2 T = 1032 nr/day Eden and Hazel Method s = 0.0002512Q + 0.00064561ogt0 + 0.0000003864Qr The second pump test was a seven day constant rate test which commenced 31 May 1985 with an average discharge of 62 1/s. The drawdown apparently reached an equilibrium after 2000mins with possible recharge/discharge discontinuities before 30mins. It was considered appropriate to analyse the data using type curves for a leaky confined aquifer (see Appendix 2.). The results were as follows:- o Type curve for leaky confined aquifer Where * — *W(u) = 1; 1/u = 1; s = 1.33m; t = 53.91 mins; r/B = 0.25 Calculated parameters:- T = 375 m2/day S = 0.00106 leakage factor = 919.6m Hydraulic resistance = 2255 days National Rivers Authority - Relocation of Suffolk Water Company borehole 4 The leakage could be coming from o recharge from the R. Lt. Ouse o recharge through the confining Drift o direct recharge from rainfall during the pump test (40.5mm recorded at Harling Farm, East Harling). Data is not available to adequately separate out any possibility or combination of recharge. The value of transmissivity derived from type curve analysis (T=375 nr/day) is consistent with other estimates within the area.