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Huge Sewer River Contamination Remediation

History:  As a result of the penstock failure in the trunk sewer in  October 2011 sewage was discharged into a River in London. Waste Management Total Solutions Ltd was asked to conduct a clean-up operation along the River which ran through a Nature Reserve.

The remediation work was carried out over two separate periods. During the first clean-up in (December 2011) the whole section of river between the outfall and the upstream boundary  was addressed and remediated. Subsequent in-channel assessments of the river highlighted 10 areas which suggested signs of persistent polluted sediments. As a result, sediment sampling and analysis was carried out to identify those locations which warranted further attention (January 2012). This analysis indicated that four of the 10 sites would benefit from WMTS Ltd bespoke remediation program with further remediation and a second clean-up. 

Preperation: December 2011 this was carried out the, dates work was undertaken and the methods and equipment used during the initial clean up period. The number of operatives deployed at each section and the types and quantities of material removed are also listed. The materials removed were disposed of at registered waste disposal sites.

First Phase of Program

It was decided for remediation work during site inspections and underwent remediation until significant visual improvements were realised across the River and Nature Reserve dessimated by the sewage contamination.

Locations Description Methods Employed Material removed in Dec 2011

Bath Road bridge to Crane Banks reservation, adjacent to southern end of Waye Avenue (approx 1km). Two Operatives carried out manual removal of material using rakes and wet / dry aquatic Hoovers.

Vegetation was removed allowed to dry out and litter was collected. With Vegetation, sediment remediated and 20 refuse sacks of litter removed.

Crane Banks reservation, adjacent to southern end of Waye Avenue to A30 road bridge
Two Operatives carried out manual removal of material using rakes and wet / dry specialist aquatic Hoovers and 33 refuse sacks of dried material and litter were removed.

Donkey Wood to Brazil Mill Wood Two Operatives carried out manual removal of material using rakes and wet / dry aquatic Hoovers. Were employed 80 refuse sacks of litter and fly tipped waste were removed.

Second Phase of Program

March / April 2012

Following in-channel assessments and sediment sampling other locations were considered in need of further, targeted remediation. The locations at which work was carried out, the dates work was undertaken and the same methods and equipment used during this subsequent remediation period.

The number of operatives deployed at each section and the types and quantities of material removed are also listed. The materials removed were disposed of bt WMTS at licensed facility

Location Description Methods Employed Contaminants removed 12 April 2012.

Right bank 20m downstream of Bath Road bridge (known as ‘Location 10’ during sediment sampling) Six operatives carried out manual removal of material using rakes and shovels. Wet and dry aquatic bespoke Hoovers.

A rigid boom was deployed to help prevent dispersion of sediment into the river flow.6 x 50kg heavy duty waste sacks of silt, vegetation and fly-tipped waste. Were removed Waye Avenue disused footbridge (know as ‘Location 9’ during sediment sampling)

Also in April 2012 Beneath the A30 road bridge (know as ‘Location 8’ during sediment sampling) Six operatives carried out manual removal of material using rakes and shovels bespoke aquatic Hoovers,  28 x 50kg heavy duty waste sacks of silt, vegetation and fly-tipped waste. Were removed.

Crane Park Nature Reserve (know as ‘Location 7’ during sediment sampling) 500m of temporary road were laid by WMTS Ltd to allow a 6,000 litre tanker to access the park and remove sediment from the river which was discharged directly into Mogden STW.

Eight operatives carried out bank-side raking and manual removal of material using rakes and WMTS a peristaltic flow control pump,. aquatic Hoovers 8,082 litres of sediment sludge*. 6  x 1000 litre Intermediate Bulk Containers (IBC) of vegetation, sediment and sewage contaminated grasses were removed and other general waste.

At each location, measures were taken to reduce any adverse impacts from the clean-up operation on the local environment. However, special consideration was given to Crane Park  due to its status as a Local Nature Reserve.

To protect the pathways and grassed areas from potential damage from vehicles, heavy machinery and tankers, 500m of temporary road was laid from the entrance at Hanworth Road to the work area adjacent to the Shot Tower.

Plywood boards were deployed at the inlet to the network of channels on Shot Island and at the weir downstream of the work area, in order to prevent dispersal of any sediment disturbed during the clean-up operation.

Sandbags were also used to reduce the flow through at location during the work, with a rigid boom  positioned to prevent floating debris passing through the mill sluice. Burrows identified during a water vole survey were flagged so operatives could ensure they remained undisturbed.

Over a  4 month period the river and Nature Reserve were remediated back into a main free flowing  river and habitat Nature Reserve again through WMTS bespoke aquatic and control program.

Habitat Control measures were needed and applied by WMTS Ltd.

 

Photograph 1: Temporary road in Crane Park Nature Reserve to protect pathways and grassed areas.

 

Photograph 2: Contaminated Silt and sediment.

 

 Photograph 3 Sandbags upstream of Location

 

Picture 4 Contamination Cleared area

Photograph 5 Rigid boom at the mill sluice

Photograph 6 (Before): Team clearing river bank

From Shot Island, Crane Park River Channel and marshes 13 March 2012

 

Photograph 7 (Before): Sediment 

Photograph 8 (After):

From Shot Island, Crane Park River channel and marshes 19 March 2012

 

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