ATC-0082 · Attenuation
51.5m linear attenuation tank
A long, narrow attenuation tank at Cottenham: 51.5m × 2m × 0.8m of PSM1A crates, about 82m³, built along a trench beside a new development.
- Location
- Cottenham
- Region
- Cambridgeshire
- Sector
- Residential
- Completed
- 2026
Attenuation · Cottenham
82m³
- Ref
- ATC-0082
- Region
- Cambridgeshire
- Sector
- Residential
- Year
- 2026
What we did
NW300 geotextile and a 0.75mm LLDPE membrane laid the length of the trench, the PSM1A crates built inside, then the membrane wrapped and welded over the top. Two 300mm fittings and a 110mm vent were sealed into the wrap.
The tricky bits
Length. A 51.5m tank only 2m wide means long runs of membrane in a tight trench, with a seam or a fold at every step. Each fitting and the vent were detailed by hand so the wrap stays continuous end to end.
What we delivered
An 82m³ linear tank, wrapped and sealed with its fittings and vent in, handed back for backfill.
The tank
At 51.5m long, 2m wide and 0.8m deep, this is a shallow tank laid out in a line. The PSM1A crates were built inside the lined trench to the designed volume, with the NW300 geotextile under the 0.75mm LLDPE membrane to protect it from the formation.
Testing and sign-off
Every joint in the membrane was heat-welded rather than taped, and a test weld was carried out and recorded before the tank was handed back. The installation was signed off on site in September 2026, with the weld test record and QA documentation handed over.
- Volume
- 82 m³ (51.5 × 2 × 0.8m)
- System
- PSM1A crates
- Membrane
- 0.75mm LLDPE, welded
- Connections
- 2 × 300mm fittings, 110mm vent
On site · Cottenham
On site
101m³ Stormmaster attenuation tank
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