Septic tanks, sewage treatment plants and drainage fields installed across west Cornwall, dug, bedded, connected and reinstated by a groundworks contractor, and built to the General Binding Rules for small sewage discharges.
Septic tank installation is the excavation, siting and connection of an underground tank that settles the wastewater from a property with no mains sewer, then discharges the liquid to ground through a drainage field.
A septic tank settles solids and lets the liquid soak away to ground, so it must never discharge directly to a surface water such as a stream, ditch or river. A sewage treatment plant treats the effluent biologically to a higher standard, which is why it may discharge to a surface water where a septic tank may not. That single difference decides which system your property is allowed to have.
Off mains drainage is ordinary across west Cornwall. Farmsteads, hamlets and single houses out on the Penwith and Lizard peninsulas are on their own system, and every new build, replacement and upgrade has to satisfy the same rules.
Excavation to depth, the tank bedded and surrounded to the manufacturer's requirement, inlet and outlet levels set so the run falls correctly, and backfill that does not distort the unit.
Trenches cut to level and gradient, pipework laid on washed stone, and the field sized on the percolation result to the guidance in BS 6297.
Trial holes for the water table and the depth to rock, and a percolation test to measure how fast your ground actually takes water.
Including the tank that still discharges to a ditch or stream, which has to be resolved when a property is sold.
Foul runs from the property, inspection chambers, venting and reinstatement afterwards. Surface water is kept out of the system and handled separately as drainage solutions or a soakaway.
Your system is compliant from the day it goes inSited, sized and discharged the way the General Binding Rules require, so the system is not a problem at sale or at building control.
The field is sized on your ground, not on an assumptionWest Cornwall ground changes over a few metres, from free draining head to granite at shallow depth. The percolation test tells you which you have.
No standing water and no smellCorrect falls, correct depth and the right separation distances keep a system working through a Cornish winter rather than surcharging in it.
One contractor for the hole and the systemThe excavation, the tank, the field, the connections and the reinstatement sit under one contract with one point of responsibility.
An off mains system is a regulated discharge before it is a piece of drainage. According to the Environment Agency's general binding rules for small sewage discharges in England, a septic tank must discharge to ground through a drainage field and never to a surface water such as a stream, ditch or river. Since 1 January 2020, any septic tank still discharging to a surface water had to be replaced or upgraded, and it must be dealt with when the property is sold. Discharges above the thresholds in those rules need an environmental permit from the Environment Agency.
The rules govern where a system can go. The groundworks decide whether it works. We excavate, level, bed, backfill, drain and reinstate every day, on ground where granite and Blue Elvan come up shallow and hard, and we carry £5m public liability including groundworks and demolition up to 15 metres.
Matt Richards owns and runs Cornwall Civils & Construction from Newlyn. He started in construction at 17 and has 23 years behind him, mason by trade, then working foreman, then site manager across groundworks and demolition, before founding the company, now going into its third year. Below ground drainage has been part of the work throughout.
The system is chosen to suit the ground, not the other way round.
A tank is a product. You can buy the same one anywhere. What decides whether it is still working in ten years is the hole it sits in, the fall on the pipe and the field it drains into, and all three of those are groundworks.Matt Richards, director
23 years in construction, since he was 17
£5m public liability, including groundworks and demolition up to 15 metres
Registered company 15894537
Working to architects' and engineers' drawings
Below ground drainage runs through most of our sites. Recent work includes 26 metres of soakaway installed in stages, and three attenuation tanks on the St Ives retaining wall job, one in the lower car park and two behind the wall.
We do not publish rates, because an off mains system is priced on the ground it is going into. What you get is a written quote before any work starts, setting out:
If something on site changes what is needed, you get the price for it in writing before it happens.
Our Google reviews are public, and they carry more weight than anything we could write here.
Based on 5 Google reviews
Great company to work with. Professional, reliable and well organised from start to finish. Communication is always clear, sites are well run & the team are a pleasure to deal with. I wouldn’t hesitate to recommend them and look forward to working together again!
Read more on GoogleCornwall Civils have been working on a complex external works package for our project in St Ives. Their works have included an extensive concrete retaining wall, in-situ concrete stairs and an in-ground modular drainage system.
Read more on GoogleCornwall Civils handled a tricky concrete shuttering, steel work, and pour for us on an emergency job. They stepped in at very short notice and worked through nights and weekends to get it done. The quality of their work was excellent, and their commitment was outstanding.
Read more on GoogleI recently had the pleasure of working with Matry at Cornwall Civils and Construction, and I couldn’t be more impressed with the service provided.
Read more on GoogleOne further five-star rating was left on Google without a written review.
Tell us the postcode, what is on site now and whether the ground has been tested, and we will come and look at it before we price it.
Call Matt Richards on 07958 102538 · Get a free quote online
14 The Strand, Newlyn, Penzance, TR18 5HN
Phone: 07958 102538
Email: info@cornwallcivilsandconstruction.co.uk
Hours: Mon to Fri 07:00 to 17:00 · Sat 08:00 to 12:00
Sunday: emergency call out only
Last updated: 22 September 2026
