MEMO
DATE
30 August 2019
TO
Alisdair Simpson, Senior Planner
FROM
Matthews and Matthews Architects (Jane Matthews)
SUBJECT
Historic Character (built heritage) requirements
DOC NO.
CRL-AOT-RME-LKA-MEM-800000
CRL Aotea Utility Relocation Works (Stages 1 to 3): Review of Potential Effects and Control Measures 1
Introduction
As part of the City Rail Link (CRL) project existing utilities around the proposed Aotea Station are required to be relocated. City Rail Link Limited (CRLL) has already gained authorisation for the relocation of utilities along the west side of Albert Street, between Victoria Street and Wellesley Street. A much broader area of utility relocations is now required, as shown in figure 1 below. Figure 1 Proposed utility works
2
Proposed works
It is proposed to undertake utility relocation works for electrical, telecommunication, gas,potable water, stormwater and wastewater assets along parts of Albert Street, Kingston Street and Victoria Street. Temporary trenches are to be formed in the footpath to a depth of around 1.5m to 3m with a width of 1m to 1.8m. Once the trench is formed, bedding will be placed in the trench, with the new utility ducts and pipes installed. Once installed, the trench will be backfilled with the surface of the footpath reinstated. The works are to be undertaken in three stages, as outlined in table 1 below. Link Alliance – Building B, 600 Great South Road, Ellerslie, Auckland 1051
MEMO
No building canopies are to be removed as part of the Aotea Utility Relocation Works Stages 1 to 3. Table 1 Proposed stages of utility relocation works Stage
Details of Works
Duration of Works (approximate)
Stage 1
Works will be located along the footpaths of Albert Street, between Wyndham Street and Victoria Street, extending into part of Kingston Street and Victoria Street and along the northern slip lane between Albert Street and Durham Street.
3 months (September 2019 – November 2019)
Trenching along Victoria Street will be to a depth of 1.5m. All other trenches will be around 2.5m to 3m in depth. The total length of trenches constructed will be approximately 340m resulting in approximately 1350m³ of spoil being removed. Works will be located along the footpath of Victoria Street, between Albert Street and Elliott Street (on the south side of the street) with trenching being around 1.5m in depth.
2 months (November 2019 – December 2019)
Between Victoria and Kingston Street, on the western side of Albert Street, trenching will be around 2.5m in depth. Stage 2 A support site compound will be provided in part of the car park of Bledisloe House (details provided below). The total length of trenches constructed will be approximately 160m resulting in approximately 480m³ of spoil being removed.
Stage 3
Works will be located along the east side footpath of Albert Street (between the top of the ramp from Durham Street to the corner of Victoria Street) and the north side footpath of Victoria Street, between Albert Street and Elliott Street. Works will also be undertaken on the north side of Vitoria Street, between Federal Street and Albert Street.
1.5 months (December 2019 / January 2020 – March 2020)
The total length of trenches constructed will be approximately 180m resulting in approximately 585m³ of spoil being removed. Total length of 680m of trench resulting in approximately 2,415m³ of spoil being removed.
Approx. 6 months
In addition, a temporary construction site compound (Figure 2) will be formed on the corner of Wellesley Street and Mayoral Drive in the part of the Bledisloe House car park. This compound will be within the project designation boundary and will be established approximately from October 2019 (Stage 2), until Link Alliance - Building B, 600 Great South Road, Ellerslie, Auckland 1051
MEMO
March 2020. This site compound will be occupied by storage containers, the objective of the site compound is to provide a site that can be used as a rest area for workforce staff, and house equipment and vehicles during the works. Temporary fencing will be used to delineate the site, along with Link Alliance branded mesh scrim. Vehicle access will be via the existing entrance off Mayoral Drive and through the gate as marked on the plan. Containers are likely to include machinery equipment and a total of up to 1,200L (6x 20L drums) of diesel in bunds.
Figure 2 Indicative layout of the Stage 2 Site Compound
Detailed site layouts for each stage of the works have been provided in Appendix C of the CEMP addendum which also informs the location of the construction site compound. Table 2 below outlines the proposed activities to be undertaken along with the equipment and materials to be used. Table 2 Activities, equipment and materials Activity
Equipment and Materials
Identify and mark-out position of trenches
Truck, hand held service locator
Saw cut and remove existing pavement/ hardstanding.
Concrete saw, handheld concrete breaker (only where necessary), excavator, truck
Expose and support existing services to 1.5m depth.
Hydro vac, normal excavator, truck
Lay new power and communication ducts, place and
Trucks, plate compactor (no vibrating rollers)
Link Alliance - Building B, 600 Great South Road, Ellerslie, Auckland 1051
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compact trench backfill
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Built Heritage overview
Within the proposed works area, the following buildings are identified in Appendix 2 of the CRL Designation conditions. Table 3 Built heritage within works area
REF
Address
16
Description Bluestone Wall + toilets under wall
76 to 78 Albert Street Auckland Central
17
83 to 85 Albert Street Auckland Central
18
102 Albert Street
Link Alliance - Building B, 600 Great South Road, Ellerslie, Auckland 1051
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21
37-43 Victoria Street West
22
51-53 Victoria Street West
23
61-65 Victoria Street West
24
66 Victoria Street West
London Dairy
25
68 Victoria Street West
J H Hannan
Martha’s Corner
Link Alliance - Building B, 600 Great South Road, Ellerslie, Auckland 1051
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4
Overview of Potential risks to Built Heritage
Unreinforced masonry buildings are likely to be at higher risk from the effects of vibration or ground movement; they may have shallow foundations, soft mortar joints, simple connections of structural members or limited bracing. It is therefore important to understand the specific building structure including foundations, fabric and detailing, likely effects and methods to avoid, remedy or mitigate these effects. The Construction Noise and Vibration Delivery Work Plan (CNV DWP) for the Aotea Utility Relocation Works (July 2019) notes that some construction activities are predicted to generate high levels of vibration including excavation, compaction and breaking. Management and mitigation measures are required to avoid or mitigate potential effects. A Site-Specific Construction Vibration Management Plan (SSCVMP) is required for all properties identified in Error! Reference source not found. of the CNV DWP for the Aotea Utility Relocation Works. In addition, Appendix 2 of the CRL designation conditions requires a pre-construction building condition survey for built heritage in the vicinity of the utility relocation works in accordance with Condition 46 including the following: · · · · · · · · ·
74 Albert Street 76 -78 Albert Street (Bluestone Wall and Toilets) 4 Kingston Street 6-12 Kingston Street 83 Albert Street 98-102 Albert Street 85 Albert Street 66 Victoria Street West 68 Victoria Street West
The CNV DWP sets out required mitigation and management measures to avoid and minimise exceedances of vibration limits that may cause damage. These measures include training, and the appropriate selection, management and use of plant and equipment. Measuring and monitoring construction vibration levels is also recommended. Link Alliance - Building B, 600 Great South Road, Ellerslie, Auckland 1051
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As set out in the CNV DWP, detailed pre-construction building condition survey will be undertaken at all of the identified buildings and services detailed in Table 5Error! Reference source not found. of that report before construction begins on the Project. A Site Specific Construction Vibration Management Plan (SSCVMP) for the Aotea Utility Relocation works set out the best practicable option to avoid, remedy or mitigate adverse effects on sensitive receivers resulting from vibration that does not comply with the Project Vibration Standards. The review of potential Groundwater and Settlement Effects and Control Measures (Memo 21 August 2019) notes that no consolidation settlement is expected as a result of the proposed Stage 1 to 3 trenching activities, and therefore no groundwater settlement monitoring is required. The potential effects on buildings adjacent to the additional utility relocation works are expected to be negligible. With regards to proposed trenching works for the CRL Project, Aecom’s Technical Director- Structures notes: Early works to be carried out are within the road reserve and footpath along the front of the buildings. Some of these buildings are likely to be unreinforced masonry / brick buildings on shallow foundations, which are relatively susceptible to damage. Prior to carrying out work, investigative potholing at discrete locations will be carried out to confirm foundation type and size. These works will not cause any damage to foundations of the building being inspected. The outcome of the investigations will determine the mitigation measures to be implemented to control settlement to the building foundations. The potential mitigation methods include trench strutting, pregrouting and underpinning. Each individual building will be assessed according to its foundation type, construction and sensitivity to ground movement� Foundation depth and type are to either be investigated at the time that utility investigation trenches are carried out, or with pot-holing investigation immediately preceding the utility diversion trench construction. Appropriate mitigation measures, such as trench support, are to be put in place for the utility diversions where excavation exceeds 1.5m or where the excavation will be deeper than the foundation of the adjacent property. Damage from machinery can be mitigated through ensuring adequate protection is in place prior to commencement and ensuring a contractor briefing advising of the risks to, and importance of heritage features, is undertaken prior to construction. Damage or adverse impacts from vibration is unlikely due to the nature and extent of the work. There is potential for damage to buildings from plate compactors if they come into contact with building fabric. This is unlikely given the location of the trenches is not immediately adjacent to the building facades, and pavement replacement is only over the proposed trenches. The area also features historic streetscape elements including basalt kerbs. These features should be retained or carefully removed and reinstated, if required during the utility investigations and relocations. Link Alliance - Building B, 600 Great South Road, Ellerslie, Auckland 1051
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5
Overview of Methods to Manage and Mitigate Potential Risks
Given the nature and scale of the proposed works, together with the management proposed by this memo and other relevant Management Plans, DWPs and their addendums, it is not anticipated that the built heritage outlined above will be adversely affected during the utility relocation works. Appropriate management and protection of built heritage in proximity to the Aotea Utility Relocation Works in Stages 1 to 3 will be achieved through the proposed design, investigations, construction methods and monitoring detailed below and throughout the CEMP and suite of sub-plans.
Overview of Methods to manage and mitigate potential risks The key methods to manage and avoid or mitigate any potentials effects on built heritage from the utility relocation works include: Site Specific Construction Vibration Management Plans (SSCVMP) The objective of these management plans is to detail the best practicable option to avoid, remedy or mitigate adverse effects on a receiver resulting from vibration that does not comply with the Project Vibration Standards. Refer to the CNV DWP. Condition surveys are required prior to any works to investigate building construction including foundations and record the present condition of historic heritage buildings immediately adjacent to the early works locations. Refer to Table 5 of the CNV DWP for a list of buildings for which Pre-Construction condition surveys are recommended and including the Bluestone Wall and Toilets. The Condition Surveys form the basis for recording buildings and recording baseline information prior to works commencing. Investigations of building foundations are to be undertaken prior to the trenches being formed, in order that any mitigation measures required for the trenches are put in place. Monitoring during the works is required to ensure that vibration is recorded, and any required mitigation methods are put in place. Adequate protection along the base of buildings, near canopies, and to protect other building fabric or features if required, is to be put in place to avoid any accidental damage during the trenching for utility relocations. The Table below outlines proposed protection for the exterior facades of built heritage. Table 4 Proposed protection methods
Feature
Protection
The exterior facades of built heritage
If works are proposed near or adjacent to these elements and surfaces, appropriate protection to a minimum of 2 metres will be required. Where practicable this could be plywood sheeting.
Building canopies
These will be protected against machinery movement during the works.
Link Alliance - Building B, 600 Great South Road, Ellerslie, Auckland 1051
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Protection shall be provided within the work areas for construction works adjacent to external walls of built heritage. This shall be determined to be required by the Project Built Heritage Specialist identified in method statements. Should monitoring indicate that additional building specific protection is required, the form of protection will be confirmed by the Project Built Heritage Specialist on a case by case basis. Any work adjacent to building canopies of built heritage will need to be carried out in a way that ensures no damage. Any potential issues and necessary protection will be set out in detailed method statements. Recording Pre-construction Condition Surveys form the basis for recording buildings, including photographic recording and recording baseline information prior to works commencing.
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Conclusion
It is considered that due to the scale and nature of the proposed Aotea Utility Relocation works in Stages 1 to 3, and with the management and mitigation measures required by the CEMP, and the suite of Delivery Works Plans and Memos, it is unlikely that damage to heritage buildings would occur. Additional protection measures have been proposed to further reduce likely adverse impacts occurring. As such a Historic Character DWP for Built Heritage has not been prepared for the proposed utility relocation works.
Link Alliance - Building B, 600 Great South Road, Ellerslie, Auckland 1051