the exploration of underground man-made drainage systems.
This text is not a three step guide to better draining. It is not a fast track to drain exploring knowledge, whilst by-passing drain exploring experience. It is most certainly not a text that will equip you to explore drains. So. Now we’ve firmly established what this is not, what exactly is it? What it is, is some common sense information, served with some hard facts in order to properly portray the very real dangers of exploring drains. If you’re even slightly contemplating exploring drains and you also value your life then please take the time to thoroughly read Predator’s Approach Doc. The .doc is written with Australian drains in mind, though much of the info is transferable, and although it is quite some years old now it is still the most comprehensive resource of it’s kind available online.
When it comes to drain exploring there’s one factor that is frequently overlooked, 99% of drains are active/operational environments. In a system that is largely automated and still functioning to fulfil its purpose, the presence of unauthorised visitors is not something that is equated into operational procedures. In short there are many potentially life threatening dangers in drains that are entirely beyond the control of any clandestine tourist and entirely outside an explorers ability to reasonably calculate for, consequently complacency is never an option!
In way of a little education to highlight some of the risks involved let’s very briefly break UK draining down into its rudimentary groupings. There are roughly three degrees of separation when it comes to explorable drains:
1. The Culvert / Underground Watercourse.
Where a formerly aboveground watercourse has been channelled underground through a conduit, most often in order to make use of the newly created land above. Quite often surface water drainage from the newly created land will be connected to the culvert, giving it a secondary function of draining surface water run-off, but primarily it exists to convey the watercourse underground. By its nature a culvert will feature an infall (upstream) and outfall (downstream) structure, depending upon its length it may also feature manhole access shafts along its underground course. It is not uncommon for Combined Sewers(see below) in close proximity to a culvert to have an overflow within the culvert, conveniently out of the gaze of the general public. To avoid the sewer becoming surcharged these Combined Sewer Overflows(CSO) are situated to allow an amount of flow from the sewer to discharge into the culverted watercourse during times of excessive rainfall. CSOs usually discharge via a screened overflow to prevent solid waste from entering the natural watercourse. Culverts are often mistakenly considered to be at the more recreational end of the draining spectrum. The risks in culverts are as plentiful as in any other underground drainage system and they should be approached with the exact same caution.
Pic. 1 – Baptiser culvert, Hockley Brook, Birmingham.
2. The Storm Drain / Storm Storage Tank / Storm Storage Tunnel.
Of course the name proclaims the function of these three common methods used to deal with sudden increases in water volumes due to excessive rainfall. The name should also sound alarm bells to anyone considering exploring such a facility, these places exists solely to channel or store huge volumes of water! These three variations on storm flow management are not exclusive of one another. The term ‘storm flow’ for the purpose of this text covers overflow from combined sewer systems and the surface water run-off of separate systems.
= Storm Drains =
Storm drains come in two basic flavours and both exist solely to deal with excessive flow during high rainfall conditions, thus during dry-weather conditions they will have little to no content.
Flavour number one is the Storm Relief Sewer, aka Storm Reliefs and Storm Sewers. In conjunction with a Combined Sewer System(see below) the Storm Relief Sewer provides extra capacity during storm conditions. A Storm Relief Sewer deals with its content by one, or all three, of the following: conveying the flow to a storage tank/tunnel(see below) from where it will be later pumped back into the system; channelling its flow back into the combined system at a point where it has a greater capacity; having an overflow outfall (CSO) on a local watercourse. It’s not uncommon for a Storm Relief Sewer to employ all three methods in that order of precedence.
Flavour number two is the Storm Water Drain, sometimes confusingly referred to as just Storm Drains and Storm Sewers, these are essentially a system of underground pipes whose collective function is to take only storm water run-off enabling it to be discharged directly into local watercourses with no adverse effect. Storm Relief Sewers and Storm Water Drains are usually contained systems, only being accessible via manholes or other similar access portals. Of course Storm Water Drains may feature an outfall structure but most are secured to restrict access for safety reasons, effectively creating a contained system. With a set up of this nature there can be an increased risk of air quality issues due to reduced airflow/ventilation. This can be further compounded in some Storm Drains by the presence of decaying organic matter in standing water deposited during the last storm event. There is a school of thought that suggests a contained system presents an increased risk of drowning in the event of a storm surge event, being as there is no outfall to we washed to. In reality the increased risk is minimal as the chances of being washed any distance in an open system without sustaining major injury or loosing your life before you reach the outfall is slim.
Pic. 2 – Bunker storm drain, Warrington.
= Storm Storage Tanks =
Storm storage tanks are most often used on a Combined Sewer System(see below) to provide increased capacity during higher than average rainfall conditions, to prevent sewage overflows into local watercourses, which would normally be a last resort. They come in all manner of shapes, sizes and configurations both vertical and horizontal. They may exist along the line of a Storm Relief Sewer, but could equally be an isolated storage tank or series of tanks joined to the Combined Sewer System via an overflow weir. Once the combined sewer levels have receded post-rainfall the storage tank(s) content is pumped back into the system at a regulated rate.
= Storm Storage Tunnels =
Storm storage tunnels are the natural progression from storage tanks where an even greater storage capacity is required and storage tanks of the equivalent capacity would not be financially viable or would be unachievable. As with storage tanks they may be connected to a Storm Relief Sewer or may be connected directly to the Combined Sewer System via an overflow.
Pic. 3 – C.O.T.S. storm storage tunnel, Brighton.
3. The Combined Sewer.
Considered by many to be a much more inhospitable exploration environment, largely due to the increased risks stemming from the greater levels of bacterial contamination and the presence of decaying organic matter resulting in increased potential for air quality issues. The Combined Sewer System is exactly as its name suggests, a drainage system built to deal with a combined flow comprised of:
Surface Water Run-off: street level rainwater drainage.
Foul Water(Brown/Black Water): waste-water with a high concentration of biological (faecal matter and urine) or chemical contamination, both domestic and industrial.
Grey Water: waste-water with a low concentration of biological or chemical contamination, generated from processes such as washing up and bathing.
Combined Sewers, like Storm Drains, are contained systems that generally do not have an infall or outfall. Small conduits feed from households, businesses and street drains into increasingly larger pipes conveying the flow to a treatment works where the contaminants are removed rendering the resulting liquids and solids suitable for discharge to the environment or re-use.
Pic. 4 – The Fleet Sewer, London.
The risks of drain exploration are many and are often entirely outside of an individuals control. Many people who explore drains do so with the assistance of specialised safety equipment, from Gas Monitors and Emergency Breathing Apparatus to Intrinsically safe lighting. Sticking on a pair of Wellington boots, grabbing a torch and heading into a drain for the first time is a recipe for disaster.
The decision to explore drains lies firmly with each individual and with that decision comes the responsibility for yourself and your actions, you have taken the decision and you are responsible!