Watercourse Maintenance
Case study
Watercourse Maintenance
Annual watercourse maintenance contract for the Ouse and Humber Internal Drainage Board
Scope
Areas of low lying land typically in the east of England utilise thousands of kilometres of inland drainage channels managed by Internal Drainage Boards (IDBs) to facilitate draining, crop irrigation, storage of water and safeguarding of wildlife, habitats and protected species.
The management of these watercourses is a key aspect of flood prevention measures on a wider scale involving pump stations, flood gates, sluices and penstocks. Watercourse management of these channels is undertaken by weed cutting, de-silting, re-profiling, new cutting and in some instances stabilisation works such as toe-piling at key times of the year to ensure nesting birds and crop damage is minimal.
Contracts for management can range from a single year up to 10 years and often encompass further necessary works as become apparent such as bank stabilisation, watercourse diversion measures, culvert replacement, pumping works, cofferdams and water structure replacement; occasionally as an emergency response.
The River Ouse around the Goole area is up to 350m wide with varying tidal depths from 0.0m up to 5.29m and infrequent surges topping 7.4m. Obviously, any works involving tides, flooding and water management structures generate considerable concerns for local residents, landowners and businesses which need to be managed by appropriate liaison with the relevant bodies.
Key Aspects
Weed Cutting
Ensuring the sides of any watercourse ditch are free of weeds and blockages is undertaken using excavators with bespoke cutting attachments, depositing on the side of the bank to allow any invertebrates to return to their native habitat.
Flail Mowing
Involves the mowing of the sides of the banks using a flail mowing attachment to the excavator, to reduce the amount of vegetation.
De-silting
This activity is undertaken to reduce silt build up in the base of the channel, to ensure water is free flowing and to maximise holding capacity, either in drought or flood conditions as deemed necessary.
Re-profiling
Watercourse channels at varying times require to be re-profiled or re-cut and this involves the use of excavators.
Re-profiling of a watercourse ditch to specified angles and culvert under roadway
Challenges
Working with Water
Working in or around water poses hazards for employees arising from the natural environment. The presence of vermin and exposure to leptospirosis twinned with the possibility of drowning, all add to the normal risks involving accidents concerning machinery and moving parts.
To this end, it is necessary to adopt protocols to reduce and minimise these risks as a bona fide contractor and furthermore, to carry the necessary accreditations for both the company and the employee, reinforced with ongoing training and assessment.
Lone Working
Watercourse maintenance can often involve people working alone for long, extended periods of time. Some people prefer this, others do not. It is important to have protocols in place to provide regular checks throughout the day, welfare support and to have a programme in place to address unforeseen circumstances.
Biosecurity
Moving machinery from one property to another often requires biosecurity and environmental protocols to minimise transfer of contaminants or invasive species such as black grass. This is particularly important when working in protected sites such as SSSI.
Landowner Access & Liaison
Each watercourse usually crosses numerous landowners property and as such, it is necessary to form good working relationships to facilitate access, and understand their particular use of the land. Cropping and harvesting times all play key parts in the delivery of the contract and works need to be timed to accommodate this.
Road/Footpath Closure; Buried Services & Overhead Power Cables
Works often encompass footpath/access restrictions, diversions or buried services and overhead cables. To protect the public, contractors need to observe all the necessary licensing and permissions from the relevant authorities, whilst maintaining good relationships with residents. Communication of any anticipated inconvenience is always undertaken at the earliest opportunity.
Health & Safety
All workings require a comprehensive assessment of all risks and a method statement to minimise or overcome them. Working in the base of existing channels is a very difficult environment to keep clean and dry and pose significant risks to the health and safety of our workforce. Larger projects often involve cofferdams and over-pumping to ensure safe working conditions.
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