Working Above Buried Drainage Storage Questions Checklist

Look through drainage drawings, building paperwork and completion documents for anything showing storage, a tank, a void or an attenuating arrangement.

The structure is usually recorded once, in a document nobody has opened since the house or the extension was finished.

Ask a previous owner, the builder or the original developer whether anything of this kind was built, and record who told you what.

A recollection from somebody who was there is often the only evidence available, and it is worth attributing rather than absorbing.

Ask whoever designed the site drainage what arrangement the plot relies on, and whether any part of it is a buried storage structure.

Owners frequently know a soakaway exists without knowing whether it is a stone-filled void, a crate store or a vessel.

What kind of structure is buried on a site, and what it does, is established by a qualified drainage professional from the records rather than from the surface.

Note any regular shape in the lawn, a strip that dries differently, or a settled line, and record it as a question rather than a finding.

Surface patterns are leads worth handing over and are not evidence of what lies beneath them.

Record any cover, inspection point or vent whose purpose nobody can account for, and photograph each one in place.

A structure of this kind often has a single access point that everybody has walked past for years.

Where nobody can confirm one exists, write that down with the date and who you asked, rather than concluding there is none.

An unanswered question recorded as unanswered behaves very differently from one quietly recorded as a no.

Ask whether the structure takes water from anywhere beyond your own plot, and whether any other property or party depends on it working.

A structure serving more than one property carries obligations an owner cannot see and cannot alter on their own.

Ask for the outline of the structure to be marked on a plan of the plot, showing its edges rather than a point on the lawn.

A point tells you where to avoid a post; an outline tells you where a shed base or a drive cannot go.

Ask for its position to be described from permanent features such as a building corner or a boundary, and keep that description.

Distances taken from things that were later removed are the reason many buried records cannot be used.

Ask how deep it sits and what lies between it and the surface, recording the answer in the professional's words rather than your own.

What sits above the structure is as much a part of the arrangement as the structure itself.

Ask where pipes enter and leave it and where those runs go, since the approach runs are as easily damaged as the structure.

Work that carefully avoids the storage frequently goes straight through what feeds it.

Ask whether it has an overflow or a secondary route, where that runs, and whether anything at the surface marks it.

The route that only operates when the structure is full crosses ordinary ground and is removed by ordinary landscaping.

Establish the extent from records and from a qualified professional rather than by probing, digging or pushing a bar into the ground.

The methods an owner might use to find the edges are the same ones that damage what is being looked for.

Excavation and probing risk buried services and structures. Locating anything buried is work for qualified professionals with the right equipment.

Ask what loading the structure and its cover were designed for, and record the answer as given rather than translating it.

A translated answer loses exactly the qualification that makes it usable by a later adviser.

What may be placed, built, parked or driven above a buried structure is a determination for the drainage designer or a qualified engineer for that structure.

Ask specifically what is ruled out above it rather than only what is permitted, and write the prohibitions down as a list.

The prohibitions are the part that protects you, and they are almost never volunteered alongside the permissions.

Ask whether the restriction applies only above the structure or also to ground around it, and record what you are told.

Owners reliably assume the restriction stops at the outline, and that assumption is the one that gets tested by a foundation.

Ask who should be approached in future when somebody wants to do something above it, and keep that answer with the record.

The question arises years later, when the original designer is remembered by nobody and the record is all there is.

Ask for the answer in writing, even briefly, rather than relying on a conversation on site or a recollection of one.

A written sentence survives a change of ownership; a conversation does not survive the following winter.

List the questions nobody was able to answer, and keep that list with the record rather than setting it aside.

The unanswered list is what a future adviser needs, and it is the part that gets tidied away first.

Ask what would be involved if the structure ever had to be removed or replaced, and who would have to agree to that.

Owners assume a buried structure is simply there, and the answer shapes what any future project on that ground can propose.

Whether a drainage structure may be altered, decommissioned or removed is a determination for the drainage designer and the relevant authority, not a site decision.

Write down everything you can imagine wanting to do in that part of the garden over the next several years, however minor it seems.

Listing them in advance turns each into a question with time to answer, rather than a decision made on a Saturday.

Flag anything that involves a base, footing, post hole or slab, since these are what put concentrated load onto something designed for spread load.

A structure that carries a lawn comfortably is being asked something different by four post holes.

Flag anything that would put a vehicle onto that ground, including a drive extension, a turning area or somewhere a van occasionally stands.

Standing and turning are heavier duties than passing, and the occasional van is the case nobody mentions.

Whether any ground may take a vehicle is established by a qualified professional for that construction, and a surface that looks capable may not be.

Flag any tree or deep-rooting planting proposed in that area, and put it as a question before it is planted rather than afterwards.

A tree is a decision that becomes expensive to reverse at about the point anybody notices the conflict.

Flag any trench for a cable, pipe, irrigation line or garden lighting that would cross the area, however shallow it is expected to be.

Shallow trenches are dug by people who have not been told there is anything to avoid, which is the whole risk here.

Flag anything that would raise or lower the ground above it, including a raised bed, added topsoil or a new terrace.

Changing what sits above a buried structure changes the loading and can bury its only access point.

Tell every contractor working outdoors that the structure exists, where it is believed to be, and show them the plan you hold.

Contractors ask about services and are rarely told about anything that is neither a pipe nor a cable.

Mention it when asking for quotations rather than after appointing somebody, so it can affect the proposal rather than the programme.

Raised early it is a constraint; raised on the first morning it is a variation nobody budgeted their week for.

Tell whoever mows, digs or plants the garden, including anyone doing occasional work, and put it where they would see it.

Routine garden work reaches this ground far more often than any contractor does.

Ask each party to confirm they have understood and to say what they intend to do differently because of it.

Confirmation turns a mention into a shared fact, and the answer occasionally reveals that the mention did not land.

Agree in advance what happens if anybody meets something unexpected in that area, and who is contacted before work continues.

Agreed in advance it is a phone call; unagreed it is a decision taken by whoever is holding the spade.

The person who is contacted has to be somebody qualified to establish what has been met; an owner cannot settle that from a photograph or a description.

Keep a short note of who you told, what you showed them and when, alongside the record of the structure itself.

It costs a line and it answers the question that comes up afterwards about whether anybody knew.

Put the plan, the photographs, the written restriction and the unanswered questions into one document kept with the property papers.

Records kept with the person who assembled them leave when that person does.

Tell everybody who lives there what exists and where the record is, rather than holding it as something one person knows.

The project that goes ahead above it is frequently somebody else's idea on a weekend.

Ask whether anything can reasonably mark the area at the surface, and what would be appropriate, rather than deciding that yourself.

Marking is possible in some arrangements and unhelpful in others, which makes it a question rather than an action.

Note where any access point sits and keep planting, storage and structures away from it, so it does not have to be found later.

Access points disappear under a shed or a border within a couple of seasons and are then located by excavation.

Add to the record whenever anything is built, planted or dug nearby, noting what was done and who did it.

The gap between the record and reality opens one small job at a time and is never closed retrospectively.

Include the record in what is passed on if the property changes hands, rather than leaving the next owner to rediscover it.

A structure nobody knows about is eventually diagnosed by excavation, which is an expensive way to learn something that was written down once.