JRHT are planning works on the ponds at Derwenthorpe, during 2022. DRA has been asking for some of this work –for example stabilisation of the banks– for a long time, so we’re pleased to see it going forward now.
If you have any questions about the works, please email firstname.lastname@example.org, and we’ll put the questions to JRHT if we do not know the answers.
The following is JRHT’s description of the works:
Derwenthorpe pond remediation works
This leaflet has been produced to inform Derwenthorpe residents of upcoming works around and within the two ponds. The works are a combination of maintenance, repairs and upgrades to the existing infrastructure and will be completed gradually over the course of 2022.
The two ponds at Derwenthorpe are a significant part of the drainage scheme for the whole development and this is their primary and most important function. They are designed to take surface water run off via a number of inlets and slow it down before it enters Osbaldwick Beck. There is also an element of filtering by the reed beds as their root networks trap silt and filter out some incidental pollution that is washed off the roads by rainfall.
In slowing down the water they act as flood attenuation for Derwenthorpe and parts of Osbaldwick by preventing rapid rises of the water level in the beck which could then lead to flooding.
The ponds have also become home to a variety of wildlife and were designed to be an attractive part of the overall landscape providing important secondary functions of aesthetic, amenity and natural habitat value.
In 2021 JRHT drafted a scope works in liaison with specialist consultants. The works package picks up a backlog of maintenance tasks and repairs known issues with parts of the infrastructure, such as the nesting islands and decking area at pond one.
What is included in the works package?
The following items are included in the package.
- Ecological assessments and newt surveys.
- Surveys of all inlets and outlets.
- Subsequent clearing of debris from all inlets and outlets.
- Repairs to inlet and outlet components.
- Repairs to fencing and railings around inlets and outlets.
- Installation of new fencing or railings where lacking.
- Installation of new security grilles where lacking
- Removal of vegetation from the base of the maintenance slipway.
- Removal of silt build up to maintain safe working capacity.
- Reduction in the extent of reed bed encroachment.
- Replacement of deck area at pond one.
- Reinstatement of bank areas adjacent to deck.
- Repairs to adjacent path where slippage is occurring (tarmac and kerbs).
- Installation of new, higher spec nesting islands.
What will be the impact on residents?
Some of the work listed above may cause disruption to residents in the form of noise from works equipment, contractors’ vehicles, and path/road closures. We will work closely with contractors and residents to mitigate this as much as possible. We will ensure that no work begins before 08:00 and that all work is completed by 17:00 each day. Any road or footpath closures will be kept to a minimum.
Small works areas will be closed off in sequence (i.e. around an inlet) with heras fencing. We expect to close the footpath leading past the deck during works to that area.
The most significant disruption will be during the removal of silt which will require heavy plant and/or large pumps to be working for longer periods.
More information will be available once a contractor has been appointed.
What will be the impact on wildlife?
In order to minimise the impact of the works on wildlife, we have appointed ecologists to carry out an ecological assessment and survey the ponds for great crested newts. The timing of the rest of the works package will depend on the outcome of these surveys and will take into account bird nesting and presence of any protected species such as newts.
Some of the works require the water level in pond one to be reduced by pumping. This will inevitably impact on any wildlife using the pond at the time as it will reduce the surface area and depth of the water significantly. It will also expose areas of bank that are usually submerged which may affect amphibians or invertebrates living in those areas.
The pond will be allowed to refill naturally and therefore, depending on rainfall, the pond may take some time to refill.
The partial removal of some of the reedbed in pond one will reduce this habitat but is necessary to maintain the designed capacity of the pond. By their nature reed beds will gradually encroach across areas of open water, especially relatively shallow areas such as the Derwenthorpe ponds. By trapping silt and sediment, they gradually form new ‘land’ in which to root themselves. This causes the water holding capacity of the area to reduce.
Why are these works necessary?
The works related to maintaining flow and capacity within the drainage scheme are critical to the overall flood prevention strategy of the whole of Derwenthorpe. For example, if a pond inlet became blocked residents would experience localised flooding during rainfall at the various drains leading to that inlet.
Other works such as the replacement of fencing are about maintaining a safe public environment and some, such as the replacement of the nesting islands are about improving the ponds for wildlife.
Once JRHT has completed this work package and we are confident the ponds are in a fit and proper state, future maintenance will be carried out via the Derwenthorpe Estate Charge.
Who is paying for this work?
JRHT is funding this works package from our own funds. The aim is to get the ponds to a state where a maintenance contract can be put in place with a suitable contractor, the costs of which will then be covered by the Derwenthorpe Estate Charge and not JRHT.