Culvert investigations

Before I start, I’d like to point out that this investigation was conducted by two people – myself and [Howmuch?]. We are both sensible (well, usually) adults and have experience of, and training for, confined spaces. Entering such environments – and storm drains in particular – is a dangerous thing to do. I advise nobody to do it. Water can enter at a moments notice, there can be sudden drops, trips and gas hazards. What we did here, we undertook at our own risk, and in the full knowledge that we were trespassing and could well get into difficulty. Doing so without training, the correct equipment or suitable permission is dangerous, stupid and nobody should do it.

Since this blog started, there’s been a huge interest in Chasewater, and it’s dam. The reservoir was built as Norton Pool in the late 1700′s to feed the canal network. It’s worth thinking about this for a while, as it’s quite a concept, and one often lost on the casual observer. The canal system through the towns of the northern Black Country is almost exclusively fed by the 144m O.D. level of the Wolverhampton canal network, which runs from Horseley Junction, all the way through the suburbs of Worverhampton eastwards to Bloxwich and Brownhills in the form of the Wyrley and Essington canal. There is no canal linked to this that is higher – so where this contour canal transitioned to other waterways, downhill locks were employed. There were 30 alone on the Lichfield and Hatherton, for a start. Then there are locks at Longwood, Aldridge, At Birchills in Walsall, and several complex series at Wolverhapton. Every time a boat uses a lock, water is lost downhill. A busy canal, operating as the freight motorway of it’s day, would see huge water consumption. 

Google Earth aerial imagery with annotations as to the drainage arrangements of the spillway. Click for a larger version.

Water was precious, and Norton Pool was built to feed the canal’s voracious thirst. Over the years, the reservoir has been fed by the Crane Brook from the north (as it always has been), and has seen some water pumped into it from nearby mines. Water also seems to have been recovered from the canal at times when the level was high, and following an enquiry rom fellow Brownhills historian Dave Fellows, Chasewater Wildlife Group head honcho Graham Evans has discussed the nature of the pumping and feed arrangement last year. I’m now fairly sure water was being pumped from the coal mines on Brownhills Common into the Slough Arm. I think a mine owner may even have charged for this supply, although I can’t place where I got that impression. Together with other such sources of what would certainly have been very foul water, these contributed to the general canal supply. When the water was at a high level, it appears to have been pumped back from the canal into the Nine Foot Pool (so called because of the measuring scale erected in it). The Nine Foot is the pool on the Canal side of the dam, at the beginning of the spillway basin, designed to take the flow should the reservoir overflow. The spillway in general seems certainly to be as old as Chasewater itself, although alterations and strengthening seem to have taken place in the late Victorian period.

Ornance Survey mapping of 1902 showing the area in surprising detail. Note the 'Basin' - now dry - is marked full of water, possibly contained by the market sluices.

On Sunday last, after talking about the site for months previously, myself and top local history ferret [Howmuch?] decided to investigate the spillway, and it’s interesting drainage arrangements. To do this, we decided to enter the culverts to see where they went. On the way, we noticed some intriguing things about the civil engineering, and some pointers to the history. Much of this has already been suggested by the wonderful Andy Dennis.

We noted:

  • The current state of the spillway basin between Nine-Foot and the old sluice gates is stepped in profile on one side rather than a plain trough shape. We think this may be due to sediment dredging.
  • In Google Earth, and on the ground, the land within is darker. We’re thinking this is due to sedimentation from the filthy canal water it would have contained.
  • We’re wondering if the canal water was pumped into the basin to settle out before possibly being allowed to flow back into the main body of Norton Pool.
  • We have no direct evidence of that, just a hunch.
  • The top of the sluice seems to have had lock-style gates. We feel that water probably was retained by them, and they therefore sealed like lock gates.
  • The culverts on either side acted as a level control for the basin, but maybe a drain, too, depending on the location of the upper portals which are now buried.
  • The new storm drain seems to have been built any time from mid-1960′s to the late 1970′s. It’s a classic Reinforced Concrete Pipe (RCP) design.
  • The storm drain runs under the brickwork sluice, under the canal and heath, and emerges on the north of the new bypass as the continuation of the Crane Brook.
  • We think it was built to avoid possibly contaminated washdown or runoff  water from the old spillway basin contaminating the then improving canal water.
  • The above seems daft but it’s all we can think.
  • We’re wondering how it was all constructed, and if anyone has dates or photos. In places the brickwork in the sluice seems to have been disturbed and regrouted.
  • The brick sluice is probably now redundant, although in heavy flow conditions I wonder if the basin would backfill as a buffer?
This entry was posted in Brownhills stuff, Chasewater, Environment, Followups, Fun stuff to see and do, Interesting photos, Just plain daft, Local Blogs, Local History, News, Panoramio photo discussions, Panoramio updates, Reader enquiries, Shared memories, Social Media, Wildlife and tagged , , , , , , , , , , , , , , , , , , , . Bookmark the permalink.

18 Responses to Culvert investigations

  1. pedro says:

    I remember standing opposite the overflow with my late mucker in November 2005. I decided to find out more, but for some with enquiring mind these things just pile up.

    So thanks for the amazing detail!

    All the best Pedro

  2. David Evans says:

    HI Bob
    thank you for this amazing article. Very interesting.
    cheers
    David

  3. Becky Lisle says:

    Dear David Evans, (this is not a reply – but I don’t know how else to contact you) please may I use your photo of Elverdinghe chateau? I’m compiling a document about my great grandfather and he was stationed there june 1915. Thanks,
    Rebecca

  4. Hope you had a good long shower afterwards!

  5. Vikki Swain says:

    Hello Bob,
    Thank you very much for this brilliant article.rather you than me though lol.x

  6. D.Evans says:

    HI Becky
    of course! Try to go to Poperinghe if you can when you are there.
    David

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  8. Andy Dennis says:

    Excellent work, chaps!

    I’m trying to get a feel for how much water the basin could hold and how much rain would have to fall to fill it when the reservoir is brim full. Does anyone know what the surface area of the catchment is? And does anyone know what the interception rate is – in other words how much rainwater gets into the reservoir in a short period, assuming it’s the end of a wet winter.

    My initial sums indicate that the capacity of the basin (0.909 acres and 9 feet deep) is in the region of 6.5 million gallons. This would be filled by 1.5 inches of rain falling on the surface of the reservoir (200 acres) alone. Are these dimensions near enough? Please do correct me.

    According to Hammerwich Weather 31 mm (1.2 inches) has fallen in April and we’ve had more today.

    Another way of looking at this is to estimate the rate of overflow from experience. The old weir was approximately 18 yards long and 1 yard wide. Guessing the flow was 1 inch deep and water took 1 second to cross the weir, it would take less than 24 hours to fill the basin if closed. Last time it overflowed for much longer than this. Does this make sense? Again, do correct me.

    If my numbers are anything like right, the idea that the basin was designed as a flood control measure seems less far-fetched.

    Sorry about the imperial units, but the map gives 0.909 acres …

    Andy

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  10. Hi Andy, thanks for your great work.

    Sorry, you lost me there a tad. I’ve no doubt the basin/spillway was designed and functioned as an overflow. I’ve never questioned that. What interests me is the sluice gate arrangement and the fact that it was drafted on early aps – and seems to have been fairly permanently – full of water.

    The weir and breakwater etc. all tell a tale of energy removal in classic style. But why build the slice gates, spillway and such an beautiful twin gate-controlled sluice? This to me seems a late Victorian addition, and is really puzzling me.

    I still think they used it as a settling pond, but I have absolutely bugger all to back ha up.

    Cheers

    Bob

    • Andy Dennis says:

      Sorry, Bob, I didn’t mean to contradict you; just got ahead of myself.

      I had initially meant to write:

      “Hypothesis: All of the structures and earthworks downstream of the nine foot pool were purely for control of natural excess water in the reservoir.

      Test: At the top of the chute, which appears to have been built about the same time as the canal, are some grooves which can only have been part of a sluice mechanism (marked on the 1884 map) for holding water in the basin. A very large amount of water. If this was a response to a flooding incident, perhaps a flash flood, it must have been quite spectacular and there would surely be some exaggerated folk memory of something approaching the Biblical. The only report of such an event that I have heard relates to the failure of the original dam in 1799. If it was considered necessary to hold that amount of water for flood control purposes, why were the grooves at the top of the chute disused for so long? And, designed to 1,000 year standard, why have the newly completed works not included that scale of provision? In any case, the nine foot pool overflows so infrequently – at that for a short time – and appears not to cause any substantial problems in the Crane Brook or further downstream.

      Conclusion: On the information available, it appears unlikely that the basin and chute mechanism were purely for controlling natural overflow from the reservoir.”

      The massive pumping station must have been installed for some frequent task that would pay for itself. Pumping water from the canal into the reservoir in times of plenty doesn’t make sense to me. The canal can only be full if fed by the reservoir. If the reservoir is full, why pump more water in? If not full, why lower the canal? I say the pump must have been for pumping water out of the mine network – it did arrive a relatively short time after No 2 pit was opened, but there are two obvious problems:

      1. The plans, maps and pictures I have seen show only one route from the pumping station, that is an “aqueduct” to the top of the dam wall. If water was pumped into the reservoir, it would act as a settling tank and the basin would only come into play at times of flood.

      2. The absence of any indication of an alternative route for pumped water. Pumping to the nine foot pool would only fill up the reservoir, except in times of flood, but the mines could flood after heavy rain when the reservoir was low (in August, say). There appears to be no evidence of a route from the pumping house direct to the basin.

      A lack of evidence that you acknowledge, though the theory still seems reasonable enough (see http://coal.decc.gov.uk/en/coal/cms/environment/reedbeds/reedbeds.aspx) – “Reedbeds are the most ecologically friendly way of treating what is a serious problem – Minewater.”

      Going back to “A very large amount of water” I asked myself just how much water and whether it would need exceptional rainfall to fill the basin if the culvert to Crane Brook was closed. I think the answer is no, indeed I think the rain Hammerwich Weather has recorded this month, which is far from exceptional, might have been enough, but I don’t have enough information to be confident. How would the Victorian engineering mind have worked in light of the failure and consequences in 1799?

      The other factor is how much water was pumped out of the mines? Was this alone enough to require additional overflow capacity? There is still the same difficulty that the basin would only come into play at flood unless filled direct from the mine. Maybe, if water was pumped into the reservoir only, the filtration by reedbeds was only necessary at times of overflow? At least that gets around the absence of a direct route into the basin, but does it explain the capacity of the basin?

      • Hi Andy

        Contradict me all you like, I have no problem with that. Especially when it’s so well thought out and executed. You really are a star…

        It was just the early morning train journey fug. Canal level? Harrison’s Cathedral and earlier pits thought to have pumped waste water into the canal. I have the idea that one one owner charged for this, but that may be a flight of fancy on my part. I daresay lots of things discharged into the cut, so there may well have been times when it was prudent to reverse-fill.

        I’m just fascinated by the complexity of the sluice. I think you may well be on to something with the reed bed thing; but I’m guessing. I honestly don’t then the brick sluice in it’s current form is original. The gate mounts are concrete, and I’d day in practical terms that dates them around the latter part of the Victorian era. Perhaps it started as a pure, unlined spillway and changed with the Anglesey Branch.

        I’m hoping Graham Evans may pass this way soon. I’d be interested in his view on the matter.

        I really am open to suggestions here.

        Best wishes

        Bob

  11. Mike Hawes says:

    This is utterly fascinating to me – perhaps in the past they had some other ideas for chasewater and the surrounding areas. Now lost to time , which might account for the engineering there without explanation.

    Whilst I took my life in my hands going down the nuclear bunker in the dark I doubt I could go through those culverts, I’d be too afraid of getting stuck then water coming down. Surprised that they haven’t put raining on them given H&S nowadays.

    We had 20 mins earlier and we went to chasewater to see the new works and the levels but it was hammering it down when we got there. I shall try to visit later in the week.

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  15. George says:

    This is the first time I have come across your photographs and comments on the spillway at Chasewater unfortunately your warnings came 50 years too late for me, as I explored the culverts & tunnels in 1960. I am just as puzzled as to its original purpose as you are, I surmised that it may have been a way of getting boats from the reservoir into the canal but I could not see how.

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