H - Revised Integrated Water Management Plan by Cardno (inc MUSIC file) (13.09.19)

   3.3.12 Inspection and Maintenance Considerations
   Fundamental to the design of any WSUD system is consideration to inspection and maintenance. Asset owners
   are very interested in the provision of easy access, safety and minimal maintenance requirements. Additionally, the
   longevity, resilience and effectiveness of the system is largely dependent on appropriate maintenance, which therefore
   requires careful consideration in design. The following may be used as a guide.


    Issue                   Description                                       Guidance
    Access                  Easy access to inspect the system is fun-         Consider lifting weights of the grate
                            damental to ensuring maintenance can be
                                                                              Consider lifting procedure (specialised open-
                            carried out efficiently.
                                                                              ings requiring specific equipment to prevent
                                                                              public access)
    Blockage                Inlets and outlets must remain free of sedi-      The system is designed with an inspection
                            ment, gross pollutants and debris to ensure       port (vertical pipe) connected to the underd-
                            that stormwater is not hindered in entering       rain system. The inspection pipe comprises
                            and exiting the tree pit – maximising perfor-     a screw-cap above the surface of the tree pit
                            mance.                                            which may be opened to check the underd-
                                                                              rain and use a water jet or pipe rod to flush if
                                                                              necessary.
    Damage                  Damage to tree pit infrastructure can cause       Consider traffic management options such
                            stormwater to bypass the tree pit affecting       as bollards.
                            treatment performance. Tree pits located ad-
                                                                              Maximise structural integrity of tree pit infra-
                            jacent to roads and car parks are particularly
                                                                              structure. Include
                            susceptible to damage from traffic.
    Erosion                 Erosion of mulch or the filter media may          Inlet design should consider minimising ve-
                            occur, particularly during large events, if not   locity and sharp hydraulic drops. Rockwork
                            designed appropriately                            may be required.
    Tree, Vegetation        The tree will inevitably require maintenance      Tree supports are often required during the
    and Mulch               in the form of pruning and weeding. Design        establishment phase to stabilise plants.
                            can nonetheless minimise the burden of
                                                                              Consider using mulch that isn’t displaced
                            maintenance in some aspects
                                                                              easily
    Health and Safety       All maintenance activities must be under-    Consider siting
                            taken in such a way to minimise the occupa-
                                                                         Consider lifting weights
                            tional health and safety risk to maintenance
                            personnel and general health and safety of
                            the public.


   An Inspection and Maintenance plan should be undertaken after design of Strataflow tree pit sets which as a minimum
   would identify the requirements and frequency of maintenance. Maintenance staff should be periodically inspecting the
   system for: damage (cracking, subsidence), blockage and erosion.




16 | www.citygreen.com