scope:

This Manual applies to new and existing drainage systems. This includes:

a) Drainage assets, including culverts which convey water.

i) The function of "small culverts" (internal diameter less than or equal to 450mm) are considered the same as pipes. These assets will be classed as pipes in Ellipse and will be referred to as pipes henceforth.

ii) The maintenance of the flow of water through all culverts whose purpose is to convey water is the accountability of Route Asset Manager (RAM) Drainage.

iii) Where a culvert is greater than 450mm, the structural integrity is the accountability of RAM Structures.

b) Buildings and structures drainage at the interface with the drainage system only. The outflow of the buildings and structures drainage can be identified as an inflow to the drainage system.

c) Tunnel drainage as described below:

i) Where the drainage is provided within the tunnel to relieve the hydrostatic pressure acting on the lining or within the rock / soil mass surrounding the lining (e.g. weep holes, bore hole drains, collector pipes etc.) or integral to the tunnel portal, the drainage assets are the responsibility of the RAM Structures as the stability and integrity of the tunnel lining could be dependent on them. The RAM Drainage is responsible for the flow of water through the drainage system via the normal maintenance regime.

ii) Where the drainage provided within the tunnel has no impact on the hydrostatic pressure they are the accountability of the RAM Drainage and will be maintained and inspected via normal maintenance regime.

This manual can also apply to drainage systems abutting, feeding or receiving flow to or from railway drainage systems, as well as those that cross Network Rail's infrastructure.

This manual does not cover:

a) Operational property drainage systems, other than at their interfaces with railway drainage systems,

b) Drainage systems for bridges, tunnels and retaining structures that are managed as part of the structure,

c) Installation and inspection of Pumps.

Purpose

This Manual helps mitigate the risk of drainage system failure by promoting a coordinated approach to the management of railway drainage assets.

The purpose of this Manual is to define the requirements and provide recommendations for drainage whole life cycle activities. It comprises of 15 modules (see Figure 1 and Table 1) which collectively:

a) promote a co-ordinated approach to the management of railway drainage systems

b) provide procedures for identifying risks, assigning priorities and determining measures to maintain safety and reduce performance loss attributable to defective drainage systems

c) provide details to those persons who have responsibility for inspecting, evaluating, maintaining, renewing and improving the drainage systems

Failure to manage assets in line with this Manual may lead or contribute to the risk identified in the Drainage Bow Tie: Exceeding drainage capacity or loss of function; for example, leading to flooding or earthwork failure. An example of the Drainage Bow-Tie is provided in Appendix A with the latest version available from the Professional Head.