Built Heritage

12 December 2019

Normanby Road Early Works Historic Character (built heritage) requirements Memo from: Jane Matthews Memo to: Michelle Chan

1. Introduction As part of the City Rail Link (CRL) project, existing utilities along and in the vicinity of Normanby Road are required to be diverted. The Normanby Road early works will commence in March 2020 and will involve establishment of a Construction Site Area, utility diversion and construction of a temporary utility and pedestrian bridge across the North Auckland Line.

This work will not directly affect any identified historic heritage buildings or structures, or their scheduled extent of place, however, the south sewer diversion work is located in the driveway to the south side of the scheduled building at 26 Normanby Road (Former Colonial Ammunition Company Bulk Store). Other scheduled historic heritage places nearby include the Colonial Ammunition Company Shot Tower, Former Main Offices at 49 Normanby Road, and Mount Eden Prison at 1 Lauder Road, Mount Eden.

49 Normanby Road

26 Normanby Road

Shot Tower

Figure 1 Proposed wastewater diversion works in Normanby Road

Link Alliance | Level 3, 25 College Hill, Freemans Bay, Auckland 1144

2. Proposed works in proximity to identified heritage buildings

26 Normanby Road

Figure 2 Part of staging diagram showing proposed diversion of wastewater line (sewer) connecting to Normanby Road.

The existing wastewater line (sewer), is shown in pink in Figure 2 above, extending from Normanby Road, through the property at 22 Normanby Road and past the south west corner of the building at 26 Normanby Road. The utility relocation works include a diversion of the sewer in the driveway of the property at 22 Normanby Road. The new section of sewer will be the located to the south of the scheduled Former CAC Bulk store at 26 Normanby Road, to connect to the existing wastewater line towards the rear of the building.

This work will involve a trench approximately 2 metres wide x 2.5 metres deep, generally parallel, and approximately 4.5 metres from the main south wall of the building.

For the sewer diversion, the sequence of construction works will generally be as outlined below: • Cut seal.

• Excavate trench.

• Install pipes and Manholes.

• Backfill and compact trench.

• Reinstate road and footpaths.

Construction equipment will include: • 20t digger • 3.5t loader • 200kg plate compactor • 15t Roller • Floor saw • Hydro-excavator • 6-wheel tip truck

3. Built Heritage overview The following heritage buildings are located near to the proposed works.

Table 1 Built heritage near to works

REF

Address

Heritage Identification / Description and Photo Former Colonial Ammunition Company (CAC) Bulk Store Refer PC 31; Scheduled in AUP Schedule 14.1 in Category B

26 Normanby Road

The bluestone CAC Bulk Store was built in 1921-1922 Former CAC Shot Tower Scheduled in AUP Schedule 14.1 in Category A (ID 1770) Listed by Heritage New Zealand Pouhere Taonga, Category 1, List number 87

24 Normanby Road

The Shot Tower was built around 1916 to manufacture lead shot for shotgun cartridges and is the only remaining shot tower in New Zealand.

Former CAC General Office Scheduled in AUP Schedule 14.1 in Category B (ID 2752) Listed by Heritage New Zealand Pouhere Taonga, Category 1, List number 9926 49 Normanby Road

1 Lauder Road

The brick CAC General Office building was built in 1916-1917.

Mount Eden Prison Scheduled in AUP Schedule 14.1 in Category A (ID 01721) Scheduled extent of place applies to whole site, extending to Normanby Road near intersection with Lauder Road.

Listed by Heritage New Zealand Pouhere Taonga, Category 1, List number 88.

Figure 3 Plan showing property addresses; Auckland Council Geomaps.

4. Potential Impacts and Mitigation As set out in the Construction Noise and Vibration Delivery Works Plan (CNV DWP) for the works, preliminary compaction vibration level predictions in Section 6.2 identify that there is potential to exceed the cosmetic building damage thresholds for heritage buildings at the south-eastern end of the building at 26 Normanby Road. Cosmetic building damage effects are deemed minor damage in the DIN Standard referred to in Section 5.2 of the CNV DWP, such as cracking in paint or plasterwork that can generally be easily repaired. A pre-construction Building Condition Survey is recommended, 1 Engineering Geologists for the Link Alliance advise that the sewer diversion is unlikely to encounter groundwater. The excavation will mostly be in basalt/gravel fill and may encounter basalt at the base.

Care will be required to avoid mechanical settlement during excavation of the trenches, but consolidation as a result of groundwater drawdown will not occur. 2 Other potential impacts on built heritage include possible impact damage from machinery working near to the building at 26 Normanby Road.

Methods to be implemented during the utility diversion work to manage and mitigate any potential effects of vibration on built heritage are set out in the CNV DWP. A site-specific noise and vibration management plan has been prepared for 26 Normanby Rd including vibration monitoring. A building condition survey is to be carried out prior to the trenching works commencing to record baseline information and ensure any damage is identified for remediation.

Appropriate protection, such as site fencing to 2 metres high, will be installed along the south side of the building at 26 Normanby Road to avoid any risk of impact damage.

5. Conclusion The proposed utility diversion works may have potential to exceed cosmetic building damage thresholds at the south eastern side of the heritage building at 26 Normanby Road. A building condition survey will be prepared, and monitoring and management measures identified in the CNV DWP will be put in place, together with appropriate protection as required. These measures will enable any potential damage to be avoided as far as practicable or remediated if any cosmetic damage occurs.

J Matthews 16 December 2019

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Section 6.2 Construction Noise and Vibration Delivery Work Plan, Normanby Road Early Works, 12 December 2019 Email W Roberts, Senior Engineering Geologist, Link Alliance, to M Chan 10 December 2019.

ATTACHMENT A – SOUTH SEWER DIVERSION DRAWING WITH ANNOTATED NOTES

Link Alliance | Level 3, 25 College Hill, Freemans Bay, Auckland 1144