Envex Contractors Ltd, Severn Stoke, Worcester. WR8 9JP

DRAINAGE & SEWER SYSTEMS

• Sewage & Water Treatment Works
• Gravity Sewers
• Pumping stations
• Pumping Mains
• Sewer Connections
• Storm & Flood Alleviation
• No Dig Installations
• Repairs and sewer linings

Sewage & Water Treatment Works

Although some treatment plants are occasionally built on green field sites, work normally involves the extension and modification to existing sites, often carried out under restrictive conditions whilst interfacing with live operations.
• Large and deep, sheet piled tank excavations.
• Installation of preformed GRP tanks and RBC units
• Insitu Reinforced Concrete aqueous retaining structures
• Reed Beds
• Ductile iron pipework
• Kiosk bases, ducting, builders work for M&E contractors
• Placement and removal of filter bed media.

Gravity sewers

• Large scale upgrade and renewal of urban sewer systems installing large diameter sewers at depths up to 7m deep
• Installation of first time sewer schemes to new developments or to properties currently using septic tanks where environmental requirements dictate connection to the mains sewer.
• Investigation and repairs to existing drainage systems, both commercial and domestic

Pumping stations

• Domestic applications - Individual prefabricated pumping stations can be installed to achieve outfalls to public sewers where ground levels do not permit natural gravity drainage.
• Segmental shafts - Deep, large diameter precast segmental shafts as part of a larger drainage project

Pumping Mains

Applications range from installing small diameter, low pressure mains for local drainage and irrigation, up to substantial projects requiring large diameter cross country, high pressure strategic trunk mains.
• Mains installed in a variety of materials and methods including
- Ductile Iron,
- Butt Fusion welded plastic pipe,
- Coiled plastic pipe and electrofusion joints
- Push fit mechanical jointed plastic pipes
Eg Hagley to Kidderminster dual 350mm. M.D.P.E. buttfusion pumping through agricultural and pasture land as well dealing with major highway and railway crossings
Sewer Connections
• We are NRSWA accredited and provide a prompt and efficient service to local builders or developers who require a connection to the main sewer.
• As well as installing the sewer, we will make all the necessary arrangements including applications to the Water Authority and dealing with the Highway Authorities for road closures, traffic management, NRSWA licenses etc.

Flood Alleviation & Storm Water Attenuation

There is an ever increasing demand for the prevention of flooding by controlling the methods with which rain & storm water are dispersed from existing and new developments. This entails the construction of various types of storm holding tanks, upsizing of existing sewer systems and modifications to watercourses. New construction methods can also include the construction of rainwater recycling systems and road surfaces that minimise the amount of rainwater run off.s.
• Storm Water Storage tanks
- Insitu concrete tanks
- Box culverts storage tanks
- Ovoid pipes
- Plastic & GRP tanks
- Cellular storage systems
• Sewer up sizing – see gravity pipelines.
• Regrading, cleansing and diversion of watercourses
• Recycling rainwater systems incorporating collection, storage and return pumping pipelines.
• Porous and Permeable road construction to allow natural drainage through hard surface areas.

No-dig Installations

With the advances in ‘no-dig’ technology and the increasing demand to minimise disruption to the public highways, pipelines and sewers can be installed using a variety of drilling, boring and tunnelling methods.
These are utilised to construct the full spectrum of drainage installations, subject to budget, ground conditions and other site restrictions. Applications range from awkward sewer connections in heavily congested roads to the installation of multiple lengths beneath areas of strategic or scientific importance.
We undertake projects which often include a combination of opencut trenching and no-dig installations. Using the services of our associated specialist suppliers we install pipe lines using:
- Timber headings
- Directional drilling
- Auger bores
- Pipejacking
- Segmental tunnels

Sewer repairs & linings

Where sewers are found to be in a poor state of repair, it is possible to extend the life span of the sewer using various structural lining methods. This is often less disruptive and a cheaper option rather than carrying out a full sewer replacement.
Local collapses and breakages are identified by CCTV surveys, which are then repaired prior to the sewer being cleansed and a GRP structural lining being inserted. This method is suitable to most applications ranging from domestic lateral sewer connections to large scale private and public sewers.

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