Mystery at Stanley Pontlarge

Saturday 20 July

The bulk of the team's effort is still focused on Culvert 11A, however, there was a diversion today to do some investigation on Culvert 28A at Stanley Pontlarge. We'd had another report of flooding next to a chamber in the field on the downstream side of 28A. This seems to happen when there is heavy rain, which is understandable if there is a problem in the chamber. We believe that the culvert under Prescott Road has collapsed, it was CCTV surveyed back in February 2016 and reported to the local Highways Authority. There's no sign of any remedial work having been undertaken so we expected a major silt build up, more on this later.

Things have changed at Bridge 11 over the last week, the gabion installation has been completed, but there's still some work to do on the down side cess extension.

Roger and Michael inspecting Bridge 11 Down side gabion wall

Bridge 11 Down side gabion wall

The up side concrete is all solid enough to work on now.

Culvert 11A up side cess outfall concreted

Culvert 11A up side cess - shuttering removed

Culvert 11A up side, Alastair, Michael and Roger get started

Down side cess drain, Dave rescuing bricks for recycling

There's a slight issue on the down side cess extension, there's a bit of a leak somewhere and the flow is ruining under the pipe. A bit of remedial work will be required on Monday.

Flow under the extension pipe

Side walls are going on the up side cess ditch where it joins the culvert, there has been a bit of discussion about the design. In the end Roger took the curved route.

Roger working out the design
(Photo: Alastair)

Michael continues with the up side north wall
(Photo: Alastair)

We did a couple of resupply runs to keep the brickies in materials, the stockpile in the yard is being slowly migrated down to site.

More bricks anyone?

Dave unloads the sand and cement while Michael waits for another mix

The cess ditch outfall taking shape

Alastair rations the mortar supply

Dave and Stuart went off to do the Stanley Pontlarge investigation. We look after the downstream side of the culvert in return for access over the field to the railway.

Culvert 28A - the sandy patch is hiding the chamber
The hole towards the left corner is where the water escapes

Chamber lid dug out

Seems like a lot of spoil for a little hole

When the lid was removed, no issue was found, the chamber is remarkably clear considering the amount of silt on the top.

28A downstream chamber

This is where we get the mystery, the schematic below shows the layout.

As the flood water escapes upstream of the chamber it would seem to point to the chamber being blocked; it isn't. We know there are several pipes out of the up side chamber, the picture below from Nov 2015 shows two of them. The general understanding was that the the right hand pipe was abandoned and blocked, perhaps this is not the case.