Silt Trap Service Report

Murray Timber Group,

Ballon,

Co. Carlow.

Reference: 0127: Murray Timber

File Reference_____________________

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Project Ref : Murray Timber Method Statement

Report status: Silt Trap Service Report

Contractor: Murray Timber

Address: Murray Timber, Ballon, Co. Carlow

Date: 01/03/17

Prepared by:

Martijn Leenheer BSc (Hons)

Environmental Scientist

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Murray Timber, Ballon, Co. Carlow Silt Trap Inspection

Mitchell Environmental called to the above site on the 22nd February 2017 to carry

out a Service of the silt trap.

Weather: first showery, later continuous rain.

Introduction

Following the recommendations to service the system annually. As the system is

dependent on filters and settlement these maintenance service intervals are important

for the efficient functioning of the system, These works were part of a scheduled

service regime.

Inspection of silt-trap before works commenced

The first gully is effectively holding all large solids. All screens seemed to have been

holding solids and sludge. The screen from tank 3 to tank 4 seemed to have been

working but the screen from tank 2 to tank 3 seemed to have been clogged and some

signs of overflowing was noted. It was proposed to replace the foam filter with a

geotextile filter. The coalescent filters in the interceptor were sacking and need

replacement. It was agreed to replace these filters on the next inspection.

Service Works

In order to make the works possible the water had to be removed. The water in Tank

1 was pumped forward into Tank 2 the previous day. As Tank 1 was emptied

completely the water in Tank 2 was pumped into Tank 3. This was done to ensure

no untreated water would be discharged.

The sludge in Tank 1 had a depth of 220mm before the additional screen and seemed

to have been settled evenly. After the screen the sludge had a depth of 150mm. The

sludge was evenly dispersed, indicating that the screens that were added in 2015 are

effective. All walls and the floor of the tank were cleaned using a high-pressure

washer. The geotextile of the screen was washed and desludged. The sludge was

taken out using a vacuum tanker. The screen has sustained some damage as one of

the wooden beams had cracked. The repair will be scheduled for the next time when

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the tank will be pumped dry. The damage is not significant or interfering with the

efficiency of the system.

The gully was cleaned and all solids were removed. The screen lip was clogged, the

obstruction was removed and screen cleaned. Sludge was taken off the gully floor.

Tank 2 contained 350mm of sludge covering the whole floor. The procedure of tank

1 was repeated.

While works commenced in tank 2 the rain intensified and the system started to fill

rapidly. The water in tank 1 started to flow into tank 2 while work was still

conducted. As the tank one filled within the course of 2.5 hour it was decided that,

for safety reasons, the work in tank 3 and tank 4 could not be carried out.

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Photos

Photo 1: Some signs of overflowing due to clogged screen

Photo 2: Screen effectively stopping floating solids (left) and Geotextile filter (right)

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Photo 3: Cleaning of the tank in progress

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Photo 4: Cleaning the gully

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Photo 5: Gully after cleaning

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Photo 6: Screen withholding solids and sludge

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Photo 7: Cleaned screens in their position

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