If it leaks your talking major excavations and disposal……
We just got rid of a single skin tank for this exact issues
There’s no reason to have a relatively new single skin tank surely. Are oftec installers still doing that -seems fairly negligent to allow home owners to fit singleskin tanks given some of the other rules they swear by
working in the contam land industry, I’d be bunding, double skin tank and drip tray protect underfloor pipework.
last job we did was in an old stone semi detatched cottage where a small leak had meant a relatively large pool had migrated under the cottage and saturated the foundations. Whole house floor needed dug out to groundwater level, chemical reagents used to treat the foundations, and a flush through.
I would have been better to demolish and rebuild as it’s still ongoing, but insurers didn’t want that, presumably due to neighbouring property can o worms.