Maintenance Hole Structures Technical Addendum Background

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Cecil Jacobs
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1 Maintenance Hole Structures Technical Addendum Technical Addendum Number: SEWL TA SEW 01 Revision B MRWA edition version 1.0 of WSAA Sewerage Code WSA Background Construction validation activities carried out in 2011 identified a number of constructed shallow cast in situ Maintenance Hole structures that did not meet the Design and Construction requirements outlined in the MRWA edition of the WSAA Sewerage Code WSA 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 recent review of the existing WITS Standard drawings and Sewer Code requirements, this updated technical addendum clarifies South East Water s requirements for the design and construction of maintenance holes.

2 Changes to the Sewerage Code Requirements 1. South East Water has re introduced a set of drawings, including some 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 Revision Name Comments and Purpose SCH.021 B Maintenance Hole Landings, Stepirons & Landing Planks SCH.031 B Cast In Situ Maintenance Holes Flat Top SCH.032 B Cast In Situ Maintenance Holes Conical Top SCH.033 B Cast In Situ Maintenance Holes Truncated Top SCH.034 B Shallow Maintenance Holes SEW B Water Seal Arrangements Twin Maintenance Hole System 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. These drawings replace SEW 1301 V. The Designer is required to specify the type of each maintenance hole on the design drawings. Drawing SCH.032 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. 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. Revises SEW 1411 to include additional details for twin maintenance hole water seals (also referred to as gas check maintenance holes ). WITS Standard Drawings SCH.021 Rev B, SCH.031 Rev B, SCH.032 Rev B, SCH 033 Rev B, SCH.034 Rev B and SEW 1411 SE WATER REV2.1 B 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 : 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, SCH.021 Rev B, SCH.031 Rev B, SCH.032 Rev B, SCH 033 Rev B and SCH.034 Rev B. SEWL TA SEW 01 Rev B Page 2 of 3 Issued 15 June 2012

3 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 SEW 1411 SE WATER REV2.1 B and SEW 1409 V. Clause includes new items (j) and (k): (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 (refer 9.2.6). (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. 2. Other Maintenance Hole Technical Addendum changes being applied to the MRWA edition of the WSAA Sewerage Code WSA 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 (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 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 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. Further Information This revision of the Maintenance Hole Structures Technical Addendum will take immediate effect on: All South East Water Land Development sewerage projects that have not completed lodgement of the Design Verification Form and Design drawing documentation via the SWIFT application. All South East Water Capital Works branch sewer and reticulation pipeline 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 colin.paxman@sewl.com.au SEWL TA SEW 01 Rev B Page 3 of 3 Issued 15 June 2012

LAND DEVELOPMENT - SURVEY MANUAL 01

LAND DEVELOPMENT - SURVEY MANUAL 01 2012 Central Highlands Water All rights reserved. This publication is protected by copyright and is provided under licence. No part of this publication may be reproduced, distributed, transmitted, stored