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Storage and discharge of return water for KFM06CAt the surface level, the return hose was connected to a return pipe between the discharge headand the first return water container, see Figures 3-3 and 3-6. The return water was dischargedfrom the borehole via the expansion vessel and a flow meter to three containers, in which thedrill cuttings separated out in three sedimentation steps. The cuttings were preserved in thecontainers for later weighing. Due to environmental restrictions, the return water was pumpedthrough an exit pipe string directly to the Baltic Sea.The flow rate and electrical conductivity of the return water was measured and data stored inthe data-logging system. Technical specifications of the measurement instruments are given inTable 3-3.Flow rate and other flushing water data were continuously stored in an automatic data-loggingsystem, see Section 3.3.3. As a back-up and double-check, the total quantity of water suppliedto the borehole was acquired by counting the number of filled water tanks used, multiplied bythe tank volume.3.3.3 Drilling monitoring systemThe Onram 2000 CCD drilling machine is supplied with a computer based logging kit integratedin the steering system (cf. Section 3.3.1). The parameters logged are those used for automaticoperation of the drilling machine. During drilling of some of the earlier telescopic boreholes,KFM01A to KFM04A, quality problems with the core and the borehole wall were observedfrom time to time. Therefore an upgraded software was installed and some parts of the steeringsystem were exchanged already prior to drilling of borehole KFM05A, which was drilled duringthe period Feb 10 th 2004 to April 20 th 2004 /3/. The new software and equipment have been inuse since then.Table 3‐3. Technical specifications for instruments used for measurement of returnwater parameters.Instrument Manufactorer/type Range of measurement RemarksFlow meter Krohne IFC 010-D 1–350 L/min InductiveElectrical Conductivity Kemotron 2911 1 mS/cm–200 mS/cm0.1 mS/m–20 S/mFlushing Water fromclosed tanksCompressorReturn water fromthe boreholeMetal pipe supportfor water hoseContainerQ-gaugeTo recipientFigure 3‐6. Return water system. Air-lift pumping raises the return water, consisting of flushing water,groundwater and drill cuttings, from the borehole. The cuttings separate out in three stages in thecontainers (where it is preserved for later weighing), after which the water is pumped to an approvedrecipient.20