Our riverside wall collapsed on 2/1/23 and the trench wall is cracked and bowed. We believe the damage is due to the tar floor between the walls preventing water soaking down into the ground, forcing the top of the walls out, causing the trench wall to bow and the river wall to collapse. The tar floor has a layer of soil above that absorbs water, but the tar floor prevents it draining into the ground below. On 18/3/23 we manually removed some of the debris to prevent it affecting the river flow and to show we had started to deal with it.
We needed to cross the blacksmith’s shop with digger, tractor and trailer to clear all the debris. This meant we had to put soil down in the blacksmith’s area to give a level surface to access the fallen wall, so we decided to permanently cover the area, as severe deterioration had already taken place. We had to temporarily remove the boiling house foundation bracket and cover for this work, it will be put back when the walls are repaired.
We had to wait for dry conditions to get machines on site, as the track to the mill becomes slippery in winter. On 10/6/23 the digger was taken to the mill and debris from the fallen wall was removed from the river, most was taken away to be crushed for ballast, some was left at the mill for use as infill when the wall is rebuilt. No further work was done immediately afterwards as we knew it would take a long time, as work has to be done at weekends when Fred is available and we didn't want major works in progress at our open days in September. The area between the walls was fenced off with Keep Out signs as the fallen and cracked walls were unsafe and the ground between them was badly churned up by machinery, making it difficult to walk on.
On 24/10/23 we had a meeting about the damaged walls. Rebuilding the river wall with bricks and mortar would be very expensive due to the materials and time involved, I looked into grant funding but no suitable grants were available. There were also concerns a brick wall might fall down again without major modifications and strengthening. Options considered were: A cement bag wall, but this was also expensive, not environment friendly and they don't look very good; a sloping river bank to match surrounding banks which was the lowest cost option; and Gabion Baskets filled with stones.
We decided to replace the fallen river wall with Gabion Baskets filled with natural rock of similar colour to the original wall. This is a relatively low cost, environment friendly solution as there is no need for cement or scaffold to be used next to the river. Other advantages are that it will retain the original footprint of the mill building (unlike the sloping river bank option) and allow water to flow through, preventing potential collapse (unlike the brick wall or cement bag options). The curved brick corner leading into the wall will be repaired with bricks, sand and lime already on site and will line up with the Gabion Baskets, as shown in the simulated picture below.
The trench wall has been bowed since early 2019 and has gradually got worse, its now cracked. When the riverside wall fell, we knew we had to address the bowed wall in case it also collapsed. Suggestions included wall plates and anchors to hold the wall in place, but this would not improve the bow, as we were advised not to try straightening the wall as this could cause it to collapse. It was decided to remove the bowed section and rebuild it using bricks already on site, although we may need to buy some more. The wall each side of the bow will be supported by scaffold or timber while the bowed section is removed and rebuilt.
The tar floor between the damaged walls, which we believe caused the wall problems, will be broken up and removed to prevent water damage to the rebuilt wall, then grassed over again when work is finished. We don't like removing original features but we have no choice when it threatens to cause major damage, the tar floor is not visible anyway as its under soil and grass. We have other tar floors running all the way up to the boiling house, also grassed over, the boiling house foundation bracket cover shows a small part of the floor, the cover will be replaced after the walls are rebuilt.
We need dry weather to get started, we'll order materials and get them on site so work can start when workload and weather permit, this is likely to be spring 2024. This page will be updated with progress. The volunteers will help assemble and fill the gabion baskets and do any preliminary work needed, we have started to make preparations ready for repairs:-
On 2/9/23 we refurbished the boiling house corner bracket surround and cover, as it was removed so we could access the fallen wall to clear up debris. We took the opportunity to file off splinters, sand it down and paint it ready to be put back after the wall is rebuilt.
In November 2023 we modified a Kingfisher nest tunnel so it can be built into the new river wall. I held this one back hoping to build it into the new wall as its the ideal location, as Kingfishers like vertical banks or walls by slow flowing water with enough height above and below their nest tunnel.
The Grey Wagtail box was removed when the middle of the wall collapsed, in case the end also fell down. It will be refitted when the wall is rebuilt. There is still a Grey Wagtail box at the other end of the site which we believe has been used. Grey Wagtail and Kingfisher nests are from our Green Community Grant project.
Graham Bartlett
Interactive Plan Collapse Activity Green Grant Clear Debris Gallery Volunteer Preservation
