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May 26, 2020
Maintenance Hole Technical Addendum Technical Addendum Number: SEW TA SEW-01 – Revision C MRWA edition version 1.0 of WSAA Sewerage Code WSA 02-2002-2.3
Construction validation activities carried out in 2011 identified a number of constructed shallow cast in-situ Maintenance Hole (MH) structures that did not meet the Design and Construction requirements outlined in the MRWA edition of the WSAA Sewerage Code WSA02-2002.3. These installations presented occupational health and safety hazards due to the incorrect design and installation of shaft, cone and neck increments. Technical Addendum SEWL TA SEW-01 Revision A was published to address this issue and other general Maintenance Hole matters to clarify South East Water’s requirements. Following a 2012 review of the existing WITS Standard drawings and Sewer Code requirements, Revision B was released to clarify South East Water’s requirements for the design and construction of MHs. Revision C further clarifies South East Water’s requirements around drops in MHs, connections to existing MHs, MH cover class in driveways and accessibility of MH necks. The drawings have also been re-numbered to avoid confusion with previous WITS versions of the drawings.
SEWL TA SEW-01 – Rev C Page 2 of 3 Issued January 2015
Changes to the Sewerage Code Requirements
1. South East Water has re-introduced a set of drawings based on former Water Industry Technical
Standard (WITS) Drawings. These drawings take precedent over the equivalent Standard Drawings provided in the MRWA edition of the WSAA Sewerage Code. The following table summarises the drawings that have been re-introduced.
Drawing Rev Name Comments and Purpose
MHTA-01 0 General Requirements for Maintenance Holes and Flat Top Details
These drawings replace SEW-1301-V.
The Designer is required to specify the type of each maintenance hole on the design drawings.
Drawing MHTA-01 includes a table of maintenance hole types and depth ranges, which is to be used as a guide for selecting appropriate maintenance hole types.
Details for construction joints between the base and shaft have also been included.
Clearances and depths in MH necks have also been clarified to ensure accessibility.
MHTA-02 0 Conical Top and Truncated Top Details
MHTA-03 0 Minimum Drop Heights and Type 5 Drop Details
This drawing includes a table of the minimum heights of drops, below which the incoming sewer should be graded out to connect at the base of the MH.
Details of Type 5 drops for large sewers ≥DN375 have also been included.
MHTA-04 0 Landings, Stepirons & Landing Planks
The Sewerage Code does not currently include a drawing with details for landings and portable standing planks.
This drawing also provides details for step irons in addition to those shown on the current standard drawing SEW-1307-V.
MHTA-05 0 Shallow Maintenance Holes
The Sewerage Code does not currently include drawings with details for shallow maintenance holes. Use of these maintenance holes is subject to prior South East Water approval.
MHTA-06 0 Water Seal Arrangements – Twin Maintenance Hole System
Revises SEW-1411 to include additional details for twin maintenance hole water seals (also referred to as ‘gas check maintenance holes’).
The above Standard Drawings have been attached to the end of this Technical Addendum. In accordance with these drawing changes, the following changes are being applied to the MRWA edition of the WSAA Sewerage Code WSA 02 – 2002-2.3:
Clause 6.1, item (a) will be replaced with “Maintenance Holes (MHs), which are applicable to all sewer sizes and allow personnel and equipment access to the sewer system. (Refer to Standard Drawings SEW-1300-V, SEW-1302-V, SEW-1303-V, SEW-1304-V, SEW-1305-V, SEW-1306-V, SEW- 1307-V, SEW-1308-V, SEW-1309-V, SEW-1313-V, MHTA-01, MHTA-02, MHTA-03, MHTA-04, MHTA- 05, MHTA-06.”
SEWL TA SEW-01 – Rev C Page 3 of 3 Issued January 2015
Clause 6.6.2, final paragraph will be replaced with “Special construction details are shown on Standard Drawings SEW-1309 and SEW-1313-V. WITS Standard Drawing SCH.031 Rev B can be used in conjunction with Standard Drawing SEW-1309-V for larger diameter MH installations.”
Clause 7.3.2, final sentence is replaced with “Default detailed design requirements for water seals in sewers and gas check MHs are shown in Standard Drawing MHTA-06 and SEW-1409-V.”
Clause 9.2.4 includes new items (j), (k) and (l):
“(j) The Designer must specify each Maintenance Hole type (eg conical, truncated, flat top,
precast), and whether they are cast in situ (CI) or precast (P), on the Maintenance Hole Schedule
(k) A base layout must be shown for MHs where there are three or more incoming sewers, two
or more drops, angles of deflection greater than 90 degrees, unusual configurations of incoming
sewers, or sewers are offset from the centre of the MH.”
(l) Clear instructions for connecting into the existing sewer network. A base layout must be
drawn for all existing MHs that are to be connected to, showing existing details and any
modifications that are required in order to achieve working space requirements and ensure the
operation and structural integrity of the MH. Existing MHs should be inspected as part of the
design process to ensure that they are suitable for connection. A base layout is not required if
connecting to an existing stub that does not need any modification.
2. Other Maintenance Hole Technical Addendum changes being applied to the MRWA edition of the WSAA Sewerage Code WSA 02 – 2002-2.3 are as follows:
a) Protective coatings: Clause 4.7.2, last sentence is to be replaced with “South East Water requires the application of an approved lining or protective coating on all new Maintenance Hole (MH) structures on sewers ≥DN450, Gas check MHs, Pressure sewer/Rising main discharge MHs, Sewage Pumping station wet well/ valve pit chambers, and other specific structures as directed.”
b) Connection of 10 or more units: Clause 5.5.2, last sentence will be replaced with “Where 10 or more units/apartments are to be connected to the sewer system, this must be done via a Maintenance Hole.”
c) Cast in situ cover slabs: Clause 6.6.2 (a) is to be replaced with “Poured in situ MH comprising a poured base, channels and walls with a poured or precast concrete cover slab;”
d) Structural calculations for deep MHs: Clause 6.6.3 includes a new paragraph: “For Maintenance Holes >6.0metres in depth, structural calculations and a design layout must be prepared and submitted to South East Water for auditing purposes.”
e) Specification of step irons and ladders: Clause 6.6.8, third sentence and dot points are to be replaced with “Stainless steel/plastic encapsulated step irons or stainless steel/GRP ladders must be specified for all Maintenance Holes located on sewers ≥DN450, within or downstream of industrial developments, and the downstream chamber of a Gas check MH.”
f) Retrofitted landings: Clause 6.6.8 includes a new paragraph: “Where it is necessary to retrofit a landing in an existing MH, the designer is required to obtain Water Agency approval, submit structural calculations, and show full design details and construction methodology on the design drawings. Retrofitted concrete landings will not be permitted.”
This revision of the Maintenance Hole Structures Technical Addendum will take immediate effect on all Land Development sewerage projects that have not completed lodgement of Design Verification, and all Capital Works sewerage projects currently under detail design phase.
If you have any further enquiries or suggestions regarding any of the information outlined in this Technical Addendum, please e-mail Mr Colin Paxman at [email protected]
Full Set.pdf MHTA-01-Drawing No. XXXX MHTA-02-Drawing No. XXXX MHTA-03-Drawing No. XXXX MHTA-04-Drawing No. XXXX MHTA-05-Drawing No. XXXX MHTA-06-Drawing No. XXXX