supplementary letter report apz / bal 29 compliance

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PI_CIC041103_APZ_Advice_Apr14 Bushfire Protection Planning & Assessment Services

of 10 15/05/14 Ph: (02) 4476 3681 - Mob. 0428 296 526 - Email: [email protected]

SUPPLEMENTARY LETTER REPORT

APZ / BAL 29 COMPLIANCE - AMENDED STAGE 2B

BAY RIDGE ESTATE 15th May 2014 ___________________________________________________________________________________________________________________

The following advice / report relates to a proposed amendment / revised allotment plan for Stage 2B of

Bay Ridge Estate, North Batemans Bay (herein ‘the subject development ’).

This additional advice / report should be considered supplementary to the previous APZ compliance

report for the subject development as dated 28th January 2014.

This additional advice / report has been prepared at the request of Mitchell Alexander, CIC Australia

Limited PO Box 1000 Civic Square ACT 2608.

This advice / report refers to;

an approved subdivision plan of the subject development, which also denotes the designated area of

an Easement for Drainage of Water and associated buffer (Appendix 1) – herein ‘the approved

plan’,

a proposed / revised subdivision plan of the subject development (Appendix 2) – herein ‘the revised

plan’,

estimated AS3959 BAL-29 setback compliance for interfacing allotments to identified / persisting

bushfire hazard areas affecting the proposed / revised plan (Appendix 3 & 4), &

Australian Standard 3959 Construction of buildings in bushfire prone areas – Clause 2.2 Simplified

Procedure & Table 2.4.2 Determination of Bushfire Attack Level (BAL) – FDI 100 (1090 K), herein

‘AS3959 ’.

The purpose of this additional advice / report is to more accurately detail the available area of Asset

Protection Zone (APZ) available to allotments interfacing the identified / persisting bushfire hazard and

demonstrate the available area of the interfacing allotment to facilitate a residential building designed and

constructed to AS3959 BAL-29. Further, this advice / report makes a considered determination regarding

any implications for any reduction in building envelopes for the affected lots.

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For the purpose of this advice / report, the interfacing allotments include;

Lots 136-141 - being those allotments adjacent to forest equivalent vegetation to be retained as part

of an ‘Easement for drainage of water ’, estimated to be approximately 80m wide. This includes a

40m wide easement area plus an additional 20m wide vegetated buffer either side, &

Lots 115-122 - being those allotments adjacent to remnant or rainforest equivalent retained as a

vegetated buffer to the Kings Hwy, estimated to be approximately 25m wide.

The location and extent of the Easement for drainage of water, in relation to the revised plan, is derived

from a combination of the current revised plan and previous approved plan. These plans respectively

denote the single easement area (estimated 40m wide) and easement area plus vegetated buffer

(estimated to be an additional 20m wide to the easement area), as otherwise shown Appendices 1 & 2.

Whilst it is not suggested the previous assessment of the easement area and associated APZ / setbacks

were incorrect (for the purpose of the previous report), it is acknowledged that this assessment is more

detailed and has slightly modified the location and extent of the easement area and associated buffers.

The advice / report also notes comments from the NSW Rural Fire Service to the Council (email 3/04/14)

which states;

Note condition 4b of the BFSA which highlights the potential for the assessment of future

dwellings on lots within Stage 2B1 and 2B2 (map shown below) as being BAL 40 and BAL FZ

under AS3959. I am bringing this to your attention to assist Council in providing advice to any

future land owners/developers of the site and also so that Council is aware of this implication

during any future complying development assessments or assessments under s79BA of the

EP&A Act for sites within the subdivision.

Council may wish to consider approaching NSW Planning and Infrastructure to ascertain the

permissibility of parts of the areas identified on the map below as “forest hazard” (vegetation

buffer) being maintained as an Outer Protection Area. An additional 4m – 14m would be required

as an Outer Protection Area within the “Forest Hazard” (Vegetation Buffer) to ensure future

development can achieve BAL 29.

The relevant section of the BFSA (Condition 4b), dated 31/03/14, states;

The RFS has identified that future dwellings on a number of lots within Stage 2B1 or 2B2 is

anticipated to be required to comply with Sections 3 and 8 (BAL 40) and/or Sections 3 and 9 (BAL

FZ Australian Standard AS3959-2009 ‘Construction of buildings in bush fire-prone areas’.

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The above RFS comments and BFSA condition are discussed at the conclusion of this advice / report.

For the purposes of AS3959 BAL-29 determined compliance, the previously established site conditions

(APZ Compliance 28/01/14) are still considered applicable.

Predicated upon the previously established vegetation and slope parameters, the minimum distance of

the site from the predominant vegetation class, to achieve BAL-29 or determined compliance, would be;

18m from remnant / rainforest equivalent, &

39m (49m1) from forest vegetation.

The determined compliance in this regard is established using AS3959 Method 1 – Simplified Procedure (Clause 2.2)

AS3959 Table 2.4.2 (as follows) outlines the respective distances and corresponding parameters. A spatial analysis of the required / minimum setback distance to reasonably achieve AS3959 BAL-29

determined compliance is as shown Appendices 3 & 4.

Each building envelope within the interfacing allotment can be easily and reasonably separated away

from the potential forest or remnant forest hazard by the prescribed distances.

The building sitings as shown by this report are generally2 at least 400sqm or more in area, and are

located within the previously determined ‘developable land’ described and shown by the previous APZ

compliance report.

The building sitings are indicative only (for the purposes of this advice) and do not necessary denoted the

only shape and extent of a building foot-print for the purpose of this report and determined compliance.

In some instances (e.g. Lots 115, 122, 136, 140 & 141), the indicative building sitings could technically

move closer to the identified hazard and still reasonably achieve AS3959 BAL-29 determined

compliance.

Considering the above, it is reasonable to conclude that the revised plan would reasonably facilitate

residential building sites at BAL-29 if technically required.

1 It should be noted that the 49m APZ distance is only applicable across the neighbouring allotment on steepest down slope gradient – Lots 137-141 (see Appendix 3). 2 Lot 119 approx. 377sqm & Lot 120 approx. 310 sqm

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Discussion / Conclusion

The RFS comments dated 3/04/14 would suggest that it is their position the revised plan and established

developable areas would potentially locate future residential building sites within a BAL-40 and/or BAL-

FZ predicament.

BAL or Bushfire Attack Levels are derived using AS3959 methodology, either ‘Simplified’ or ‘Detailed’.

For the purpose of this advice, the Simplified methodology has been used – which is the methodology

that is generally accepted for standard BAL assessment and associated Complying Development Code

application in NSW.

This assessment is more detailed and more accurately designates the area of persisting forest vegetation

(i.e. that vegetation persisting within the Easement for drainage or water and associated buffer areas)

affecting the revised plan.

Based on the assessment of BAL compliance as determined by this report, it is reasonable to suggest

that almost the entire area of the previously identified developable area (or building envelope) is located

within a BAL-29 range or lower.

It is acknowledged that a very minor part of some of the developable areas (as previously established)

would technically extend into a BAL-40 limit (i.e. Lots 115-122 & Lot 163). Even so, a building footprint of

at least 300-400sqm can reasonably be sited within the developable area, and setback to the extent

required for BAL-29.

Just as it would be possible to reasonably reduce the developable areas as previously identified, it would

also be reasonable to suggest that the previously identified developable area within Lots 139-141 could

be technically increased.

With regard to any suggestion that the developable areas would be located with a BAL-FZ limit, this

report and assessment disputes this outcome – predicated upon the vegetation and effective slope

parameters, and extent of persisting forest or remnant forest vegetation retained as part of the revised

plan.

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Therefore, it is respectfully concluded that;

the revised plan can easily and reasonably facilitate sufficient area for future residential building sites

to achieve BAL-29 (or lower) for all interface allotments,

whilst this report does not necessarily dispute the previously denoted developable areas (or building

envelopes) as marginally within a BAL-40 range, it is disputed that any part of developable area

would be within a BAL-FZ range,

Any reduction of the previously established developable areas (or building envelopes) is

unwarranted as the majority of those areas already facilitate AS3959 BAL-29, &

any requirement or approval condition for additional / increased APZ areas is over and above the

prescribed minimum areas, as outlined by this report, for determined compliance or AS3959 BAL-29.

Notwithstanding this conclusion, it is acknowledged that any additional interfacing areas of the

identified forest hazard that could be managed as an Outer Protection Area would facilitate a greater

level of radiant heat management, and may potentially facilitate a lower AS3959 BAL limit (i.e. BAL-

19).

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The above letter report has been prepared by:

Matt Jones BAppSc Environmental Health Grad. Dip Design for Bushfire Prone Areas BPAD-L3-14598 Accredited Practitioner

Bushfire Protection Planning & Assessment Services Pty. Ltd, BPAD-A Certified Business BPD-BA-09336 Corporate Member No. 14598 Fire Protection Association Australia

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APPENDIX 1 – Subdivision Plan Approval

40m wide Easement

20m wide Buffer

20m wide Buffer

40m

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APPENDIX 2 – Proposed (Revised) Subdivision Plan – Stage 2B1

40m wideEasement

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APPENDIX 3 – Estimated BAL-29 Setback Limit – Lots 136-141

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APPENDIX 4 – Estimated BAL-29 Setback Limit – Lots 115-122

supplementary letter report apz / bal 29 compliance

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