The Humber Bridge

Humber Bridge

In the mid to late 1970’s the troubles in Ireland had resulted in the IRA carrying out a sustained bombing campaign in England, many large bombs were detonated causing serious damage to property and loss of life. Coded warnings were often given to provide time to evacuate the area, not always with enough time. 

Alongside actual bombs, virtual bombing campaigns were causing major disruption, a coded warning could result in huge evacuations and result in many hours or even days of disruption whilst the army bomb squads checked to ensure the area was safe.

The Humber Bridge was a potential target for either a real bomb scare, or a virtual warning. 

Calculations had been made as to the length of time it could take to check the entire structure for a device, should a coded warning be received. 

It was determined that so long as it could be proven that all openings accessing the bridge inner structure were closed, and that any access granted had been vetted and checked, only an external examination would be necessary which would save hundreds of hours of searching, should a threat arise. 

To permit this it would be necessary to monitor electronically every single door or access hatch in the structure. 

Tenders for the work were invited from all four national intruder alarm companies at that time, no one wanted the job, so vastly inflated prices were submitted, however Chubb drew the short straw and won the tender. 

The work entailed installing a contact on more than ninety access points, these were located at sea level, lower bridge level, road level etc. also installing personal attack alarms for each toll booth, as cash would be collected in considerable sums during the normal every day operation of the bridge.

Chubb used the electrical contractors to install Mineral Insulated (MI) cables from the control room to every point on the bridge, as the bridge measures one mile between the towers, and access hatches at both ends into the main cable anchors were greater than a mile from the tower bases, most cable runs were in excess of one and a half miles in length and some exceeded three miles.

I worked on the system on several occasions, initially the bridge roadway was still incomplete so it was necessary to know which end of the bridge required work on the day, as it was a 65 mile round trip if you were at the wrong end. 

The concrete was so hard that a special miniature pneumatic drill was purchased to drill fixing holes to fix contacts to the concrete with magnets attached by drilled and tapped holes in the steel doors/hatches.

On one occasion, I arrived at the Hessle end of the bridge to be advised that the contacts to be fitted were located at either side to the two main towers at the height of the main support cable intersection, some five hundred feet above sea level, the concrete towers at this time were hollow structures which would eventually have steel staircases installed some five hundred feet  high. 

The towers had fourteen doorways each and there are four towers. From the entrances at sea level, to the under bridge entrances for access to the maintenance cradles which would run under the bridge, to the road level access doors, then one door for each horizontal bracing concrete point and finally at the top.

On the day I installed the contacts at the top of the two towers at the Hessle end, the staircases had not been started, the towers were essentially five hundred feet concrete tubes. There was a steel railway line up the outer section of one of the concrete towers with an access cage attached. A steel cable ran to the top of the tower, over a pulley and back to a winding motor attached to the road surface with a single bolt. 

Climbing into the cage, and giving the thumbs up, an operator pushed and held a lever and the cage started to rise until I reached the access door at the top of the tower, at which point I waved to the operator who stopped the winch. There was no room for vertigo working here, I thought. 

After installing contacts onto the inner and outer doors at the top of one of the two towers, I took a little time to enjoy the view from the top of the bridge, later it was published that a person had fallen from the top and that the body had never been found, it had been calculated that his body hit the water very hard, then continued and hit the bed of the river Humber, before being washed out to sea.

During my time on the bridge, I had privileged access to parts most people would never see, from standing on the top of the towers, to riding in the maintenance cradle under the bridge, and witnessing the incredible anchor points where thousands of individual steel wires that make up the support cable come to ground. 

One view was quite spectacular, the view from inside the road surface sections, each connecting section had an oval hatch like a submarine door, with these open you could see the curvature of the earth in the rise and fall of the doors throughout the 2½ miles of the bridge road structure.

All the alarm points came back to a custom-built panel within the control and operations tower where individual lights would indicate if an access point were open or closed, or if a toll booth alarm had been activated. I was not deemed worthy to connect the system to the indicator panel, hence supervisors completed this task to commission the system. 

Alarm indicator panel

I later learned that the stunning, custom made panel had been built with a serious flaw in its design, all the circuits in intruder alarms are closed, going open in alarm, the panel had been built for open, going closed in alarm, the reverse of what was required. It had been necessary to jury rig the panel with an additional 100+ relays to reverse the operation of every circuit. What a painful alteration, taking a custom-made panel costing a lot of money and bodging it to work.

Working some sixty to a hundred miles away from the stores, depending upon which end of the bridge I needed to access, raised other questions. The engineers traditionally travelled by public transport to sites, carrying their hand tools. All parts, ladders, steps, drills, pipe benders etc. would be shipped to and collected from site by James in the company van. At one point, the company agreed that engineers who owned cars and were prepared to carry some parts, electric drill and extension lead etc. would be able to claim a mileage allowance.

I was using my motorcycle rather than public transport, but could not carry any parts, so was paid bus fares only. At the time, busses were heavily subsidised, to the extent that you could travel to Hull from Leeds return for just £3.70. I complained that my petrol costs were far greater for a one-hundred-and-twenty-mile round trip and was simply told by my favourite supervisor Gordon, “use the bus then” and if you don’t like it, we can always make you redundant.