Our designs for the development in Cookridge

Drainage
Proposed Foul Water Drainage
Yorkshire Water have stated that the development of the site should take place with
Our designs for
the development
in Cookridge
separate systems for foul and surface water drainage.
Yorkshire Water have confirmed that foul flows from the development should
discharge to the existing combined diameter public combined sewers crossing the
site at a point in the south east corner of the site.
A new on site foul drainage system will be required to be constructed to adoptable
standards to serve the development. The topography of the site will allow the
proposed foul drainage to be able to drain via a gravity system.
There are existing sewers crossing the site that have not been accommodated within
the current layout and will require diversions under a Section 185 Agreement. The new
diverted sewers will provide continued drainage capacity following the diversions.
At present it is proposed to utilize the diverted combined and foul water sewers
from the site to serve the new development. This will involve the relaying of a new
combined sewer up to 900mm diameter to cater for all the existing flows from the
site and the inflows from the adjacent development.
Proposed Surface Water Drainage
The existing surface water from the site has been approved to discharge into the
watercourse crossing the site. The general topography of the site falls towards
Moseley Beck and the site would fall within its natural catchment.
The surface water runoff from the development will be restricted, in terms of
discharge, in line with Leeds City Council development control standards for flood
risk. This requirement stipulates an agricultural discharge of 2.5 or 5 lit/sec/hectare.
An analysis of the system will be made to ensure this is achieved for the whole,
or any part /phase of the development. This will entail the use of storm-water
attenuation systems incorporating flow control devices and associated storm-water
storage facilities. These will be a mixture of above and below ground systems.
Due to the topography of the site and the existing watercourses crossing the site the
overall site area has been split into three sub catchments to allow control of surface
water discharges to the watercourse crossing the site.
The new surface water scheme will be designed to ensure no flooding on site for the
1 in 30 year return periods and to ensure no flooding of properties for the 1 in 100yr
storms, including climate change.
Land Drainage
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There are areas of boggy land to the south eastern portion of the land and these
are believed to be due to isolated perched water tables in areas of sand inclusions
within the clay soils. It is proposed to improve the land drainage system to allow
these areas to drain better to Moseley beck via field drains. There are shallow
channels crossing the site that appear to have been installed when the existing
residential development to the north was constructed. These channels have
become in filled it is proposed to reopen these channels and form shallow banked
watercourses across the site to improve the ecology and the drainage of the area at
the same time.
The general levels of the land in these areas will be raised slightly to ensure amenity
areas and gardens are not subject to flooding from ground water. A perimeter French
drain will also be provided between the site and the adjacent residential development.
Proposed Layout
Not To Scale
Key Facts
Separate systems of foul and surface drainage
Storm water storage above and below ground
Diversion of existing foul sewers
French drain between site and existing houses
Surface water drainage to Moseley Beck
Reinstatement of historic field drains