Case Study
Effective silt pollution prevention on the A59 at Kex Gill
Construction, Infrastructure & DevelopmentClient
RSK Environment
Location
Kex Gill
Objective
New road infrastructure on the A59
Challenge
Addressing landslips whilst avoiding silt pollution
The challenge
The A59 at Kex Gill has faced numerous landslips, prompting a rerouting project.
The road between Skipton and Harrogate has been closed multiple times due to landslips, with the latest closure lasting three weeks. The new road design aims to address these issues.
The solution
Managing silt on construction sites is challenging, especially on steep, rain-prone hillsides with highly mobile sub-soils and sensitive watercourses nearby. This was the situation at Kex Gill. We collaborated with RSK Environment to develop silt pollution management options in these challenging conditions.
When working on any site a priority task is conducting a Settlement Test on the subsoil to assess silt pollution risk. At Kex Gill, the test revealed a fine clayey subsoil structure that is difficult to control in surface water, particularly run off. The site’s designation as a SAC, SPA, and SSSI added further challenges, with many upland ground breeding bird species and notable fish species requiring specific mitigations to avoid disturbance.
Silt pollution from construction sites can significantly degrade water quality and harm aquatic life. When silt enters water bodies, it can make the water cloudy, reducing light penetration and affecting photosynthesis in aquatic plants. It can also clog the gills of fish and smother benthic organisms.
Additionally, silt can carry pollutants such as heavy metals and nutrients, further impacting water quality and ecosystem health.
Our products, including Clearflow’s Gel Flocculant in a Pipe Reactor, were used to pre-treat clay-impacted surface water. The Pipe Reactor discharges into a Silt Capture Channel, designed to disperse energy and capture flocculated particles.
Long-term silt capture
Floc Mat® and Silt Mat™ were used for long-term silt capture without frequent replacement. Water attenuation ponds were also employed to slow water flow and capture heavier silt particles.
Innovative water treatment
The innovative solutions ensured effective silt pollution prevention and sediment control. Gel Flocculant, Floc Mat® and Silt Mat™ used in conjunction with the Pipe Reactor, provided an environmentally safe and efficient method to treat clay-impacted water.
Minimal environmental impact
The Silt Capture Channel offered robust and long-lasting silt capture capabilities. Water attenuation ponds played a crucial role in managing water flow and capturing heavier silt particles, ensuring minimal environmental impact.
The results
Environment protected
Protections put into place that kept wildlife safe from silt pollution.
Cost-effective solutions
Early intervention and planning ahead saved money.
Low carbon design
Low carbon solutions which deliver immediate, effective and beneficial results.
Feedback from Georgina King Associate Director / Team Leader – North East and Central Region RSK Environment
“The Kex Gill road realignment scheme is a challenging project with multiple environmental risks including management of silt and water quality of the surrounding environment given the locality of designated sites.
“Frog Environmental are providing us with extensive technical support, including the design, supply and install of their silt control products on site to ensure the project minimises risks to the watercourses in the project vicinity and prevents impact on highly sensitive aquatic species.
“It’s great to be working with them and we’re delighted with the success of the whole project.”
The products
Floc Mat®
- Low cost, low carbon way to treat clay-impacted water run-off
- Can be used on land and in ditches
- 100% biodegradable for easy disposal or seed onsite
- Simple to deploy and highly effective at controlling fine particle silt pollution
Silt Capture Channel
- Captures silt and flocculated fine silt particles
- Unique design utilising Frog Environmental products
- Standard design polishes up to 900 litres per minute
- Supplied with site review service to ensure correct placement on site
Gel Flocculant for Silt Control
- Can be deployed passively in flowing water or in pumped systems (Pipe Reactor & Clearflow GFR)
- Long lasting, low maintenance silt control devices
- Supplied with site review service to ensure correct site-specific deployment and efficacy
- The most cost effective method to manage fine suspended solids on site
Pipe Reactor
- Portable unit for dosage of Gel Flocculant blocks
- Quick and simple to set up
- Treats water at up to 1,800 litres per minute
- Highly cost-effective method of managing clayey water on site
Silt Mat™
- Cost effective silt pollution control on site
- 100% biodegradable for easy disposal or seed onsite
- Can be used on land, in ditches, streams or rivers
- Unique heavy-weight design delivers longevity on site
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