Archived report · 2 min read · Set in Brook Row ·
Inspection of the Cutting Wall at Brook Row
A highways survey of the retaining wall above Brook Row finds damp rising in a pattern of footprints, each one a little higher up the stone than the last, and no drainage route that could account for them.
- filed: Filed at the spring sitting, under the drainage heading
- reference: HW/BR/22-114
Subject: retaining wall, eastern cutting, above Brook Row.
1. The wall is a dry-laid ashlar face, eleven metres high, built in 1889 to hold back the bank that carries the bus turning circle. It was last surveyed in 2019 and found sound.
2. On inspection the lower course shows a band of efflorescence approximately two metres long, running along the face at knee height. Moisture is visible within the joints. Readings on the meter are within normal range for a wall of this age.
3. The band is not a drainage line. No outlet, weep hole or culvert feeds the face at this point, and the bank behind is clay with no seepage. Damp of this kind normally travels down, under gravity. This damp travels up.
4. Above the first band, a second is visible at waist height, offset to the left. Above that, a third. Each mark is shaped like the sole of a bare foot, with five toe-prints at the front and a heel-print behind. The marks are dry at their edges and damp at their centres, as a footprint is when the water has just left it.
5. Photographs were taken at each level. The sequence shows the marks rising in a line from the bus shelter at the base of the cutting toward the parapet of the upper road.
6. The surveyor, Mr. D. Caddick, notes that the marks are not present on the photographs taken in 2019, and that no maintenance work has been carried out on the face since.
7. Recommendation: remove the efflorescence and reapply lime wash. Repeat the survey in three months to establish whether the marks continue to advance.
8. Observation not explained by the survey: at the time of inspection, the top mark was level with the parapet, and the surveyor's own boot print, made on the upper road, was found to match it exactly in size and pattern.