Background
The existing A465 (Neath to Abergavenny) was built in the 1960s and is a single three lane carriageway with two lanes in the uphill direction and one in the downhill direction. A regional traffic study in 1990 identified the need to improve this road. This improvement to the A465 is critical to the social and economic regeneration of the Heads of the Valleys area.
The width of the road restricts traffic flow and opportunities for safe overtaking. In many areas, there is poor visibility. Accidents on this stretch are concentrated around junctions and areas with poor visibility.
This improvement to the A465 is critical to the social and economic regeneration of the Heads of the Valleys area. It will improve access to key services, jobs and markets supporting inward investment to areas such as the Ebbw Vale Enterprise Zone. Total project costs circa £220m.
The Overall Objective
Due to the excavation work carried out, surface water runoff picked up slow settling solids leading to the need for chemical treatment. In addition, the pH levels of the surface water runoff were elevated due to a nearby batching plant, meaning pH adjustment would also be required.
Solution
Siltbuster installed a 3 stage Chemical Dosing System capable of flow proportional dosing both coagulant and flocculants alongside a pH adjustment system to automatically neutralise the high pH water.
Infeed waters (sampled from the lagoon) had TSS around 570mg/l and pH of 10. The sample of the treated water showed a massive reduction in TSS to 9mg/l and near neutral pH of 7.76.
