the renovation of Shiplake Lock in Oxfordshire . the original lock at Shiplake dates from 1787 and was a pound lock . the present lock , which has now been extensively overhauled by the Thames conservancy , was built in 1874 . the lock has an overall length from gate to gate of 133 ft 4 in , a width between rubbing strips of 18 ft 3 in , and an original depth over the head cill of 6 ft 5 in , and 5 ft 6 in at the tail - this latter depth now being increased to 6 ft 3 in . the lock is situated about three miles from Henley-on-Thames in Oxfordshire . the cills of the original lock , which have now been replaced , consisted of timber baulks spiked on a bed of heavy sleepers . this lock is of interest in that the quoins or corner pieces are not shaped to accommodate the heel post of the gate , but are square in section , the heel posts being hung on pintles set in front of the quoins and secured to them by iron collar straps at the top . a water seal is made between the heel post and the wall by means of a mitre board . in the renovated lock a strip of Linatex rubber has been incorporated in the edge of the mitre board to improve the seal . in common with many locks of early date , no hard floor was provided between the mass concrete lock walls , although timber baulks of substantial section were set in the earth floor to act as struts between the bases of the walls . renovation , which entailed closure of the river to traffic , took place between October 31 last and February 6 this year . the need for a major overhaul was brought about by the deterioration of a number of factors . the first of these was the tilting of the headgate pintles which were progressively moving out of true alignment as the timber sleepers under the cill deteriorated . this caused jamming between the pintle casting and the heelpost shoe casting , a situation which required removal of these components on two occasions for machining . this was , however , a palliative , the effect of which was lost with continued settling of the pintles . considerable leakage was also taking place under the timber sleepers and through lift construction joints in the cill wall , thus impairing the operation of the lock . the timber cills were also worn on their surfaces , in addition to being decayed , and had been recapped several times to ensure a tight fit between them and the gates . further causes of anxiety were the decayed state of the old timber baulks bracing the toe of the lock walls and the deterioration of the lock floor . the site preparations for lock repairs are normally governed by absence of road access to the site and , with the river closed , it is usually necessary to bring all materials and equipment including sufficient barges for transportation of broken stone to the site before the lock is sealed off . in this instance , road access was available at a point some 100 yards from the lock , but separated from it by a water meadow liable to recurrent flooding and by a 60 ft wide leat which formed the water course to a mill which existed near the site in earlier times . the preparations thus commenced with the transport by barge and erection of a 3 ton Butters luffing derrick , which commanded the body of the lock with the exception of the gate recesses . this crane was supplemented by a Priestman Wolf crane fitted with a 40 ft boom for service at these two points , this being augmented when necessary by a 3 1/2 ton Grafton steam crane mounted on one of the barges . the concrete preparation plant consisted of a 15 ton Portasilo to which cement was delivered in bulk by the C.M.C , this unit being set up in conjunction with a Parker 14/10 mixer with weighbatcher and scraper unit . the batching and stockpile yard was located above the general flood level , on a levelled dump of Thames ballast by the road side . the aggregate and sand used for the works were Kennett gravels , derived from Hall &amp; Co. &apos;s pit at Theale . type of conveyance of concrete from the batching plant to the lock was determined by the existence of waterlogged ground and a 60 ft wide leat , limited space on the lock side and the desirability of crossing the lock itself . transportation was thus by means of a road machines monorail system in which 12.5 cu.ft skips are driven by a 7 1/2 b.h.p motor and hydraulic drive . the skips are set in motion at the loading point and travel unattended until stopped automatically wherever a special stopping device is fitted in the rail . this was found to be particularly useful in that the rail was taken over the lock and along one side . a further section of rail was located on the other side of the lock and upon these rails was mounted a travelling bridge which traversed the lock length . a riser rail connected the main mono-rail system to a short length of curved rail on the bridge . concrete was discharged from the skips , through openings in the floor of the carriage to a trunking system for the various sections of the work . of particular importance in the scheme was the provision required to be made for a reliable drainage and pumping system . the work was carried out during the wet season , when high head and tail water conditions could be expected at the main cofferdams and when the ground water level would be close to surface . experience on work at other locks had shown that the throttle settings of normal self-priming centrifugal pumps required constant attention to reduce the amount of time lost through the flooding of the workings . when pumping from a sump with a 22 ft vertical suction it was found that with the setting too far advanced , or with a slackening of the inflow , the sump would be emptied and the suction lost and , whilst the priming was being regained , the water level would rapidly rise in the workings . similar delays had been experienced when sudden inflows were encountered or when the pump speed fell for any reason . such pumps also required to be set immediately over the lock , thus reducing the working space available . past experience indicated that an inflow of up to 90,000 gall &amp;sol; hour , might be reasonably expected and to allow for unforseen contingencies , two Sykes 8 in Univacs were installed to deal with twice this capacity . the use of these pumps enabled a horizontal as well as vertical suction to be used , enabling the pumps to be located well clear of the working area , whilst of greatest importance was the fact that the water level in the sump remained constant at the level of the flange on the base of the suction pipe . the pumps were arranged to deliver to the spillway of the old mill which served as a useful collecting launder for the gravel pumped out by the Univacs . the pumps were powered by Ruston &amp; Hornsby 4 VHR oil engines . both pumps were used each morning for rapid dewatering . thereafter one was sufficient to deal with seepage water . at a total head from all causes of about 30 ft including a vertical lift of 22 ft the inflow was well within the pump &apos;s capacity of about 90,000 gall &amp;sol; hour at this duty and worked for much of the time on snore . site lighting was provided by mains electricity to enable the pumps to be started up some 2 hours before the shift began , during which time the lock was emptied of some 210,000 gallons of water which accumulated during the night . a pump was also run for two hours after the shift had finished to enable the concrete to set . the operations started with the driving of the head and tail cofferdams , Larssen no 2 piles being used at the tail - where extra strength was required to accommodate the greater water pressure loading - pitched by the Priestman crane and driven by a no 5 BSP steam hammer . number IU Larssen piles were used for the head dam . at this dam , the pitching and driving were effected by the barge mounted Grafton steam crane . the bracing at the head dam consisted of 12 in x 12 in struts , braced off the wing walls of the dock . for the tail dam two 21 in x 8 1/4 in RSJ 40 ft long were used , strutted from sheet piling driven into either bank . baulks of Douglas fir were then wedged into position at 15 ft centres along the length of the lock , this spacing being arranged to coincide with the existing vertical rubbing strips of the lock . these baulks were set in two tiers , the lower tier being emplaced by diver whilst the lock was still full , each baulk being temporarily weighted with a length of Larssen piling . with the dams completed , the wall struts in place and the Univac pumps in position , the lock was pumped out , the suction line being placed in the tail recess of the lock . when the water had been taken down to within a few inches of the bottom , a 5 ft dia , 6 ft deep sump was excavated just upstream of the tail gate recess . this took place inside a box of trench sheeting , 5 ft dia precast concrete tube sections being used to form the sump to a depth of 4 ft below the formation level which allowed 1 ft 6 in below the invert of drainpipes to accommodate gravel , etc . this box sheeting was then extended up the length of the lock in the form of a 2 ft wide trench in order to drain the head of the lock , the trench being filled with hard core over drain . excavation of the floor of the lock followed up the completed hard core drain in 15 ft sections , the trench sheeting being removed and a 2 ft thick mass concrete slab of 7.4 : 1 total aggregate cement ratio being emplaced to within 3 ft of each wall . on completion of the floor , the remaining 3 ft strip at the base of the walls was removed and any over excavation under the walls filled with concrete and underpinned 2 ft 6 in back , the last stage being the emplacement of a 30 deg batter to the walls . the drain was thus covered over . its function during the works was to drain both the head and tail dams , the Univac holding the water level permanently at the level of the soffit . on completion all sumps were concreted , sealing the underdrainage system . whilst this work was in progress , other repairs were being effected at the head and tail of the lock , where new cills and groins were under construction . the new cills consist of 31.33 lb &amp;sol; ft steel channels of 12 in x 4 in section , set out on new 2 ft thick slabs , the channels being bolted down to their bases by Rawlbolts and secured to the step concrete behind by welded attachments to the channels . repair of the lock walls consisted of cutting back the old face to a depth of some 2 1/2 in with chipping hammers and then refacing with gunite to a depth of 2 in over a B.R.C reinforcing fabric . new tail gates were fabricated in the Reading workshops and delivered by water . the new gates have three sluices to each gate , whilst the original head gates , which carried four sluices to each gate , were overhauled , these gates being only 7 to 8 years old . the paddles controlling the sluices have been converted to hydraulic operation , along with the gate movement . the hydraulic equipment for the control and operation of the two pairs of lock gates was required to be capable of being operated either under power by the lock keeper from local control pedestals located near each pair of gates or manually from the same pedestals by members of the general public , after the lock keeper &apos;s working hours . this requirement has been met by the provision of hydraulic power equipment in the lock house , this equipment supplying a pressure supply to the pedestals ( which may , however , generate their own pressure supply by means of a handwheel operated transmitter ) . 