Case Studies

Precast Headwall with Diffuser Blocks

Precast Headwall with Diffuser Blocks

We can produce when required precast headwalls with diffuser blocks on the spillway of the headwall. Diffuser blocks reduce the velocity of water discharging through the connecting pipework into the watercourse.

The precast headwall shown in the photo has horizontal wingwalls, required due to the bank profile on this particular project. We have also factory fitted galvanised steel Kee Klamp® handrail to the back and side walls to for the safety of the passing public.

The headwall is shown being lifted by chains and M20 lifting loops to lifting points cast into the spillway of the headwall.

Precast Headwall with HDPE Flap Valve

Precast Headwall with HDPE Flap Valve

Pictured is a precast headwall with factory fitted HDPE flap valve to the back wall. We cast in fixing points for the flap valve into the headwall during manufacture. The headwall is delivered with the flap valve loosely fitted. The flap valve is removed during installation of the headwall then simply bolted back on to the backwall when the headwall and pipe are in place. The result of this is the headwall does not need to be drilled once on site.

The wingwall profile of this headwall has been selected due to the bank profile of the site in question. The wingwalls finish higher at the front end of the spillway when compared to a typical splayed wingwall headwall.

 The headwall is shown being lifted by chains and M20 lifting loops to lifting points cast into the spillway of the headwall.

Precast Headwall Deliveries

We typically deliver precast headwalls on flat bed articulated lorries. When required and the section weights permit we can provide forklift offload. If Hiab offload is required we will contact an external haulage company on your behalf if required.

The precast headwalls shown above have been factory fitted with Kee Klamp® galvanised steel handrails and Sewers for Adoption compliant outfall safety grilles. One of the headwalls has a large baffle block cast onto the spillway to reduce the rate at which water discharges from the connecting pipework before entering the watercourse. 

Precast Headwall Deliveries
Precast Headwall with Flap Valve and Cranked Grating

Precast Headwall with Flap Valve and Cranked Grating

We regularly supply precast headwalls with factory fitted flap valves. In this instance there was a requirement for a grating on the headwall as well. We factory fitted a cranked galvanised steel grating to the headwall. The grating had to be cranked to allow the flap valve to open fully during periods of heavy discharge through the connecting pipework.

The headwall is a Sewers for Adoption compliant unit. Along with this headwall we supplied a toe extension for the front end of the spillway to prevent the headwall slipping. Sockets are cast into the headwall for the toe extension, which must not protrude into the watercourse.

1600mm Circular HDPE Flap Valve

1600mm Circular HDPE Flap Valve

This is a 1600mm circular HDPE flap valve about to be packed for delivery from our factory. This is a large flap valve to be mounted to an existing concrete structure.

When retro fitting flap valves to existing concrete outfalls we supply an EPDM seal, stainless steel fixing kit and chemical anchors.

This is a wall mounted flap valve. We are also able to provide flange mounted flap valves, flap valves that connect directly onto pipework as well as tidal flap valves and reinforced flap valves for when the valve is subject to wave action

Large Rectangular HDPE Flap Valve

Large Rectangular HDPE Flap Valve

When required we are able to manufacture headwalls to site specific dimensions and specifications. We supplied a number of very large rectangular flap valves as pictured.

Most of our flap valves are manufactured in HDPE with stainless steel grade 316L reinforcements, hinges and fixings. Our flap valves typically have a design life of 50 years when subject to 1Mwc constant head of water. Our standard specification is to 5MWc for 72 hours.

Once we receive an order for a bespoke flap valve we will produce a drawing for approval. This enables site to check that the valve ordered will fit the available space. We are usually able to tweak our designs as necessary and are happy to work with contractors and engineers to find the best solution to a problem

Cast Iron Flap Valves on Headwalls

Cast Iron Flap Valves on Headwalls

When we supply a flap valve with a precast concrete headwall we typically offer HDPE. However when specified we can supply cast iron flap valves factory fitted to our precast headwalls.

This image shows a couple of our standard range H6C A precast headwalls with 450mm cast iron flap valves fitted to the backwall

The cast iron flap valve is removed during installation of the headwall then simply bolted back on to the backwall when the headwall and pipe are in place. The result of this is the headwall does not need to be drilled once on site.

We also offer cast iron flap valves as standalone products.

International Product Distribution

We regularly supply our products overseas. The image above shows a large rectangular HDPE flap valve fitted directly onto the end of a culvert section discharging into the man made watercourse below. This particular valve was one of many supplied to a project at Panama International Airport

We have experience in shipping all over the world, having recently supplied projects in Rwanda, Mongolia, Georgia, Australia, Dubai, Qatar and the US amongst others

International Product Distribution
Bespoke Precast Outfall Structures

Bespoke Precast Outfall Structures

Althon supply bespoke outfall structures for site specific requirements or extremely large culvert or pipework. This image is of large precast concrete sections produced for an RSPB project at Wallasea Island, Southend.

This structure has been retro fitted with two large HDPE flap valves, two smaller HDPE flap valves and a penstock with stainless steel frame. A galvanised steel pedestrian barrier and precast staircase were also added to the structure.

We worked closely with the designer and contactor to produce this precast solution in an environmentally sensitive area. The use of precast concrete dramatically reduced the amount of concrete that had to be poured on site (which could potentially contaminate the water in the surround area) and resulted in a very fast and safe installation

Culvert Sections, Wingwalls and Header Beam

Culvert Sections, Wingwalls and Header Beam

Althon provided precast concrete culvert sections with specially designed and manufactured precast wingwalls and header beams to the River Ilsington Conservation Centre.

We delivered the units to site in sections for a fast and efficient installation by the contractor.

We are able to design precast wingwalls for culverts to meet almost any site requirements and when required can supply accessories such as handrails, outfall safety grilles or a range of flow control devices to be retro fitted on site once the structure has been installed.

Bespoke Metalwork

Bespoke Metalwork

Outside of our range of standard outfall safety grilles and trash screens we are able to design and manufacture bespoke products when required.

We are also able to interpret design drawings to provide quotations. If we secure an order for the work we will produce our own design and preproduction drawings for approval prior to manufacture. These will detail materials used and section weights to enable the contractor to plan the installation in advance.

This photograph is or a bespoke cranked multi – level trash screen with galvanised steel safety rail supplied by Althon to a project near Telford. We undertook surveys before manufacture to ensure everything was manufactured to the correct dimensions.

Trash Screen Replacement

Althon designed and manufactured a replacement trash screen to a brickwork culvert in a wooded area. The original had become distorted over time and was no longer fit for purpose, as it regularly became blocked with leaves and other debris.

We manufactured and delivered a multi – level cranked trash screen with a mesh walkway for maintenance. We also provided a pedestrian guardrail for safety and step irons for safe access for inspection of the lower section of the trash screen.

We have large range of standard trash screens and outfall safety grilles manufactured to comply with various standards, such as Sewers for Adoption and Sewers for Scotland. However when requested we are capable of providing bespoke made to order trash screens and gratings.

Trash Screen Replacement
Swale Inlet Headwalls

Swale Inlet Headwalls

Althon manufacture swale and pond inlets allowing surface water runoff to enter SUDS features or to act as an outlet or overflow. The profile of the inlet 1:3 (18 Degrees) is the same as the surrounding ground in accordance with guidelines for the construction and adoption of swales and ponds. There is a recess formed in either side to key the unit into the slope of the swale or pond and prevent it slipping.

Our 150mm, 225mm and 300mm Swale Inlets are delivered to site with a section of twinwall pipework cast into the end to connect onto pipework on site. We also offer options for galvanised or stainless steel mesh or bar grilles to prevent access and stop debris entering the pipe system.

Precast Headwall with Extended Cascade Spillway

Precast Headwall with Extended Cascade Spillway

When required we are able to extend the spillway of many of our standard range of precast headwalls. In this instance we extended the spillway with a cascade panel made up of several diffuser blocks.

An extended spillway with cascade panel dramatically reduces the velocity with which the water discharging from connecting pipework enters the watercourse.

In this particular instance we also provided a factory fitted HDPE flap valve to prevent backflow up the connecting pipework during storm events or periods of flooding and high water

Bespoke Precast Headwall with Baffle Blocks

Bespoke Precast Headwall with Baffle Blocks

Althon are able to offer bespoke precast outfalls for instances when a standard headwall will not suffice.

In this instance we designed and manufactured a sectional precast structure with 84 large baffle blocks cast onto a sectional extended spillway.

The baffle blocks reduced the speed with which the water discharging from the pipework entered the water below. This was essential due to the steep bank profile.

After installation a handrail and galvanised steel grating were retro fitted to the precast outfall. When designing and manufacturing bespoke precast outfalls we will take into account factors such as maximum weight the site can handle either due to available lifting equipment or restricted access to the point of installation.

Inline Penstocks

Inline Penstocks

Althon have a standard range of inline penstocks for pipework up to 600mm. on request we are able to design and manufacture inline penstocks for project specific requirements.

The penstock in this photograph was to connect to 1200mm pipework at a waste water treatment works. This particular penstock had an extended pipe connection on one side.

Our inline penstocks are typically manufactured in HDPE with grade 316L stainless steel reinforcements and fixings for a 50 year design life.

This was one of several large inline penstocks installed on this project and are believed to be some of the largest ever supplied in the UK

Penstocks are typically used to control the flow of water, shut off the flow of water for maintenance or in emergency situations or maintain and manage water levels.