BRITISH WATERWAYS TECHNICAL DIRECTORATE CUTTING PRINCIPAL INSPECTION NEW PRINCIPAL INSPECTION - SUMMARY DETAILS Principal Inspection PMO: 3069560 Principal Inspection Z2: 11115245 Maintenance Plant: 9600 Functional Location: GU-027-001-L Structure Name: Cutting 22, Rowington Object Type: 006 Grid Reference (centre): SP200692 GIS Object: Yes BW Owned: Yes Include in AIP: Yes PI Date: 19/10/2011 PI Inspector: G Holland Weather: Overcast, dry Primary Asset - New Condition Grade: D Primary Asset - New CoF Grade: 1 Primary Asset - New Serviceability Grade: 1 Next Principal Inspection End Date: 19/10/2031 Reason: As AIP cycle PRIMARY ASSET CHARACTERISTIC DATA Design of Earth Structure: True Cutting Main Construction Material: Rock Full Length of Cutting (m): 700 Maximum Height (m): 14 Maximum Angle (o): 90 Minimum Navigation Width (m): 12 PREVIOUS PRINCIPAL INSPECTION – SUMMARY DETAILS Functional Location: GU-027-001-L Principal Inspection Date: 11/04/2001 Condition D CoF Grade: 1 Serviceability Grade: 1 Existing Outstanding Z4s: 10238023 – install timber bank protection PRINCIPAL INSPECTION REPORT
Superficial deposits are absent although mounds of Pleistocene till are recorded both N and S of the cutting. 4.0 Defects of Concern: At GU-028-P0000 is a crest parallel open drain ditch that has recently been excavated and an attempt made at cutting through the upper crest to drain water from the field down the face of the cutting. The landowner should be made aware of the inadvisability of discharging surface water onto the face of the cutting, particularly as this is immediately above an old slip on the lower face. The historic slips on the face should be visually monitored for evidence of remobilisation. Should this occur it is possible that the slips could cause local obstructions in the canal although it is unlikely that a total blockage would occur 5.0 Geotechnical Assessment / Stability: The and middle cutting is formed in benched sandstone and is likely to remain stable in the long term. However the geology of the cutting is such that groundwater will penetrate through the upper sandstone rock mass and along minor joints before meeting the upper surface of the underlying impermeable marl. Water will then discharge through the cutting face. It is unlikely that this could be prevented without significant drainage works. It is therefore likely that in the medium to long term minor slips will affect the face 6.0 100m Length Sub-Asset Grades Summary Table Condition C – 4m high with local face issues CoF 1 – Rough pasture Serv. 1. GU-027-P0600 Condition D – 5m high with minor slips CoF 1 – Arable Serv. 1. GU-027-P0700 Condition C – 6m high with drain and minor slips CoF 1 – Arable Serv. 1. GU-027-P0800 Condition D – 12m high with spoil mound and badger setts CoF 1 – Arable Serv. 1. Condition C – Vertical sandstone and stable slopes CoF 1 – Arable Serv. 1. GU-028-P0000 Condition D – Major historic face slip CoF 1 – Arable Serv. 1. GU-028-P0100 Condition D – 2 No. historic face slips CoF 1 – Arable Serv. 1. 7.0 Recommendations Discuss with landowner recent excavation of crest ditch and possible discharge of drainage onto cutting slope. Monitor lower slope for evidence of remobilisation or new slips. If detected geotechnical advice should be sought
PHOTOGRAPHS GU-028-P0150 – View W showing leaning trees on lower slope and offside slip encroaching into canal GU-028-P0050 – View W showing major offside slip with 1m toe bulge into canal GU-027-P0575 – View N showing minor offside face slip GU-027-P0700 – View E showing oversteepened offside lower slope and occasional leaning trees GU-027-P0475 – View E showing start of offside cutting GU-028-P0100 – View E showing offside cutting crest descending towards Rowington Hill Bridge
GU-028-P0100 – View W showing offside cutting crest and flat arable field to N GU-028-P0025 – View NE showing disused badger sett in crest spoil mound GU-027-P0725 – View E showing widening of cutting crest and start of crest spoil mounds GU-027-P0900 – View E showing rounded crest to crest spoil mound