Wildland Urban Fire Interface Assessment - Strathcona Forestry Consulting
Hazard assessment report evaluating wildfire risk for the proposed construction at 2700 Herbate Road.
Margaret Symon, RPF PCP Strathcona Forestry Consulting PO Box 457 Shawnigan Lake, BC V0R 2W0
To: Building Inspections; Planning Dept. Town of View Royal cc: Brad Johnson, 2700 Herbate Road Date: 09/01/2016
Re: Interface Fire Hazard Assessment and Setback Variance – 2700 Herbate Road
Background
In accordance with the Town of View Royal Development Permit Area guidelines for wildfire, Mr. Brad Johnson retained Strathcona Forestry Consulting to conduct an interface wildfire threat assessment of 2700 Herbate Road. The Johnsons are planning to construct a new single-family home to replace an existing garage at the eastern portion of the subject property. The Johnsons have requested a variance to the Town of View Royal required setback (7.5 m). The current setback from the existing garage structure is 0.9 m.
The primary purpose of this assessment was to rate the fire hazard/fire threat rating at the subject property. A decision on the setback variance lies with the Town of View Royal, in liaison with View Royal Fire Rescue.
The interface (wildland urban interface/wildland residential interface) describes any area where combustible wildland fuels are found adjacent to homes or other buildings. Fuels may occur at the interface, where development and wildland vegetation meet at a well-defined boundary, or in the intermix, where development and wildland fuels intermingle with no clearly defined boundary (as at the subject property, located near Thetis Lake Regional Park, where development and wildland fuels intermingle with no clearly defined boundary).
Hazard Assessment
This report describes the vegetation, terrain, and local infrastructure at the subject property, and provides recommendations that will assist the property owner to reduce the risk of wildfire. Assessment criteria are based on Rating Interface Wildfire Threats in British Columbia (https://ground.hpr.for.gov.bc.ca/ratingthreats.htm), FireSmart (FireSmart, Protecting Your Community From Wildfire (Second Edition. Partners in Protection Partners in Protection, 2003), and the Home Owners FireSmart Manual (BC Edition). Fire behavior modeling is standardized with the Canadian Forest Fire Danger Rating System (CFFDRS). FireSmart Fuel Zones are described in Appendix 1. Fuel Types listed in this assessment are customized from the CFFDRS Fuel Type list for applicability in south coastal BC (see Appendix 2). This assessment conforms to fire hazard planning authorized by Section 3(2) of the BC Fire Services Act.
Field Inspection
Strathcona Forestry Consulting conducted the wildfire hazard assessment on December 23, 2015. Bridget Johnson provided a site tour. Weather was cool and rainy.
Location and Description of Subject Property
The subject property at 2700 Herbate Road is located in a small rural neighbourhood at the north end of Thetis Lake Regional Park (map pg. 4; site plan pg. 5). The property is accessed the TransCanada Highway via Watkiss Way, Highland Road, and Barker Road. The subject property is located on a southern aspect in an area of low relief on the north side of Mackenzie Lake. An existing residence occupies the western portion of the subject property.
The subject property and surrounding area are classified in the Coastal Douglas-fir moist maritime (CDFmm) biogeoclimatic subzone, which represents the mildest climate in Canada. Common soils in the area are well-drained Brunisols. Vegetation cover at the subject property consists of grassed lawn surrounding the lake; fragmented second growth coniferous cover extends away from the lake to the neighbouring properties (Fuel Type C-5 - moderately well-stocked coniferous stands; tree crowns separated from ground). The existing garage occupies a cleared area east of an existing residence. A trail from the driveway to the lake passes the eastern end of the garage. The neighbouring property to the east of the garage has relatively low fuel loading due to an open canopy of mature, naturally pruned Douglas-fir, and a sparse shrub/herb understorey. Extensive stands of mature second-growth coniferous forest in Thetis Lake Park extend around the small wooded neighbourhood.
A common driveway extending south from Herbate Road provides a fuel buffer.
Prevailing winds are southeasterly/southwesterly. Under warm dry conditions, a fire start at the subject property or adjacent lands would spread rapidly to the surrounding forest stands at Thetis Lake Regional Park. Conversely, a fire start at the park has potential to spread to homes at the north end of the park.
Fire Suppression
View Royal Fire/Rescue is a is a composite fire department which operates from 280 Island Highway. View Royal Fire/Rescue response time to the subject property – "probably the most challenging area in View Royal" - is "over 10 minutes – quite delayed" (phone conversations with VRF/R Duty Officer, Dec. 29, 2015; Jan. 2, 2016). Fire department response time is the elapsed time, in minutes, from when the first fire fighting unit is dispatched to when the first fire fighting unit arrives at the emergency scene. Fire department intervention time is crucial in determining the consequences of a fire in terms of deaths, injuries, and loss of property and damage to the environment. An early aggressive and offensive primary interior attack on working fire is usually the most effective strategy to reduce the loss of lives and property damage.
Mutual Aid
Fire Departments within CRD fire protection areas operate under a mutual aid agreement with other fire departments with in (and outside) the region. In the case of a serious fire, mutual aid from adjoining fire departments (i.e., Colwood) benefit benefits fire suppression by pooling manpower and resources (water supply, water tenders, etc.).
Wildfires
CRD Fire Departments automatically respond to structure fires and small easily accessible bush fires. Assistance from the Wildfire Management Branch is requested when larger brush fires and/or forest fires occur in the area.
Water Supply
An adequate and reliable water supply for firefighting is an essential part of a community's fire protection system. The BC Building Code states all structures (proposed and existing) within interface areas should have a water supply for firefighting purposes that meets requirements of either the FUS (Fire Underwriters Survey) or the National Fire Protection Association (NFPA).
The property is not serviced by community piped water; there are no hydrants in the area.
In fire protection areas served by a community water system, water supply for fire protection generally consists of a piped system in common with domestic potable water. Where no adequate or reliable water distribution system exists (as at the subject area), minimum specifications for fireflow may be based on NFPA standards.
In areas not served by community water systems, such as the subject neighbourhood, the Wildfire Management Branch generally recommends a minimum of 2500 gallons for on-site emergency fireflow.
The Johnsons stated they will install a pump system to draw onsite emergency fireflow from Mackenzie Lake.
Access
FireSmart infrastructure and access increase the resident and firefighter safety, and facilitate quick response by firefighters. All developments should have sufficient access for emergency vehicles, including 2-way road access in and out of any site, and safe driveway access. Local government standards for roads and driveways generally follow the Geometric Design Guide for Canadian Roads (www.tac-atc).
The subject property is accessed from Herbate Road by a common driveway with a moderate gradient. There is a turnaround at the end of the driveway. Access roads through Thetis Lake Regional Park are narrow and winding.
Wildland Urban Interface Wildfire Threat Assessment Results
Scoring from the WUI Wildfire Threat Worksheet (from Rating Wildfire Threats in British Columbia) rates the subject property with a High Wildfire Threat. Under the MFLNRO Wildfire Threat Rating system, ratings of High and Extreme are unacceptable. Ratings must be low or moderate for an area to be considered safe. The rating reflects biophysical and development characteristics of the general area (delayed response time, narrow winding access roads through Thetis Lake Park, intermix >1 structure/ha, continuous forest fuels in the general area).
This report contains recommendations to reduce the fire threat rating to acceptable levels.
Hazard Assessment Checklist
FireSmart comments and recommendations for action are outlined in the checklist on pg. 5. Photos are in Appendix 3.
Interface Fire Hazard (Wildfire Threat) Plan of Action
| Feature | Observations/Comments: | Action Items: |
|---|---|---|
| Signage | 2700 Herbate Road sign at driveway. | - If new home is to have separate address, install address signage at head of driveway access (signage must be present during construction phase in the event of emergency response). |
| Driveway Access | Existing driveway has turnaround. Douglas-fir trees border E portion of driveway. | - See note below under PZ 1 re; pruning of trees along driveway. |
| Setback | Current setback is 0.9 m. | - Town of View Royal to make decision on setback, based on Fire Hazard/Fire Threat rating, and collaboration with VRFR. |
| Land-clearing (see comments pg. 4) Vegetation Management (See Appendix 2 - FireSmart zones) | Priority Zone 1 (0-10 m around structure(s). Fuel Modified Zone 2 (10-30 m – or to property boundaries) | PZ 1: The current fuel loading is low at the subject property. As discussed with the property owner: - prune lower branches of trees along the driveway north of the existing garage (to a height of 3 m from ground level; any smaller trees should be pruned to 1/3rd their height). Ensure any new landscaping incorporates non-combustible features. ** Vegetation management within PZ 1 Zone must be completed prior to Building Permit. ------------------------------------------------------------------------------------------------ - FMZ 2 (10 – 30 m): - Re-assess at Building Permit. Additional fuel treatment likely not be required if sufficient fuel reduction accomplished in PZ 1. ------------------------------------------------------------------------------------------------ - Ensure any soils disturbed during construction phase are promptly rehabilitated to prevent encroachment from invasive plant species (broom). |
| FireSmart Construction/ Emergency water supply for fire fighting | Roofing/siding must meet FireSmart guidelines. On-site water storage (emergency fireflow) is mandatory. | - Roofing and siding of new structure must meet FireSmart guidelines for fire-resistant exterior construction. - Follow FireSmart guidelines for design, construction, and maintenance of window and door glazing, eaves and vents, soffits and fascia, decks, etc. www.partnersinprotection.ca - Facilitate onsite supply of emergency fireflow (i.e., pump system from lake). Ensure fittings are compatible with forestry (1 1/2 "). - Liaise with VRFR to ensure emergency water supply is mapped on fire pre-planning system. - Hard-wire smoke alarms into new structure. |
| Other | Additional FireSmart measures. | - If construction occurs during the fire season (April – Oct.) ensure sufficient fire tools on site, along with minimum water supply (i.e., 7500 L via pump system from lake) for initial attack. - Ensure home and property are equipped with basic firefighting tools: shovel, hose(s), exterior sprinkler(s), bucket(s). - Hazard abatement must take place in compliance with Town of View Royal bylaws. - Develop an Emergency Plan of Action, listing key contact information in case of fire and/or other emergency at the neighbourhood. |
| Ignition Risk | Subject property located at rear of large public wooded park. | - Ignition risk is moderate in the immediate neighbourhood. Install on-site water supply and ensure fire fighting tools are readily available to resident. |
| Follow-up Assessment at | Follow-up assessment at lock-up. | - Final assessment prior to lock-up. - At lock-up stage, check to ensure new home and fireflow sources are mapped on Fire Dept. fire pre-planning maps. |
Summary
A wildfire interface hazard/wildfire threat rating assessment of a new home proposed to replace an existing garage at 2700 Herbate Road determined the current hazard/threat rating is high. Factors contributing to the high rating include: fire department response time, location of subject property in relation to Thetis Lake Regional Park, amount and continuity of forest fuels in the area, lack of a community water supply in the local neighbourhood, and narrow, winding roads accessing the subject area.
In my professional opinion, if FireSmart recommendations provided in this report are followed, the interface fire threat rating can be reduced at the property. The capacity to draw emergency onsite water supply from Mackenzie Lake is an asset. On a broader scale, however, the local neighbourhood presents a significant challenge to fire protection from View Royal Fire Rescue in terms of response time and mitigating resources (equipment, water, etc.).
Prepared by: Margaret Symon Margaret Symon, R.P.F. P.C.P. Strathcona Forestry Consulting
Appendix 1. FireSmart Interface Priority Zones
In interface areas, FireSmart advocates the establishment and maintenance of Fuel Management Zones* extending outward from structures and along access routes: Priority Zone 1 (0-10 m). Priority Zone 2 (10-30 m). Priority Zone 3 (30-100 m).
Priority Zone 1 (0-10 m): The main objective of vegetation management is to create an environment that will not support fire. Vegetation management focuses on fuel removal, conversion, and reduction.
Priority Zone 2 (10-30 m): Where treatment in PZ 1 is not sufficient to significantly reduce the fire hazard due to fuel loading, extend the fuel modified area with a variety of thinning and pruning actions.
Priority Zone 3 (30-100 m): Where fuel modification in PZ1 and PZ2 is insufficient to protect structures and/or property, FireSmart advocates treatment in Priority Zone 3 with a variety of thinning and pruning actions in order to create an environment that will not support high-intensity crown fires.
*Setback Zone distances may be extended depending on aspect, slope, fuel loading, etc.
Appendix 2. Generic Fuel Types (adopted from CFFDRS).
| Fuel Type | Description | Wildfire Behaviour Under High Wildfire Danger |
|---|---|---|
| Coniferous: C1 | Terrestrial herbaceous ecosystem: mossy rock outcroppings | High potential for surface fire, especially if high moss/lichen |
| C2 | Dense regeneration to pole-sapling (immature) forest with crowns almost to ground | High potential for crown fires; low to very high fire intensity and rate of spread |
| C3 | Fully stocked, mature forest, crowns separated from ground; sparse understorey | Surface and crown fire, low to very high fire intensity and rate of spread |
| C4 | Dense, pole-sapling (immature) forest, heavy standing dead and down, dead woody fuel; continuous needle litter; continuous vertical crown fuel continuity | High potential for crown fires, high to very high fire intensity and rate of spread |
| C5 | Moderately well-stocked, mature forest, moderate dense understorey crowns well separated from ground; continuous needle litter | Low to moderately fast-spreading, low to moderate intensity surface fire |
| C6 | Fully stocked conifer plantation; absent understorey; tree crowns separated from ground; continuous needle litter | Surface fire may spread rapidly to become high intensity fire with high rate of spread |
| C7 | Open, mature coniferous stand; uneven-aged; discontinuous understorey; tree crowns mostly separated from ground | Surface, torching, rarely crowning (except on steeper slopes), moderate to high intensity and rate of spread |
| D (Deciduous) | Moderately well-stocked deciduous stands; moderate medium to tall shrubs and herb layers; D-1 Leafless; D-2 In leaf | Typically a surface fire; low to moderate rate of spread and fire intensity. Surface, torching and crowning; moderate to very high intensity and spread rate (varies with slope and % vegetation cover) |
| M (Mixed Forest) | Moderately well-stocked mixed stand of conifers and deciduous tree species; moderate shrub understorey; conifer crowns extend nearly to ground; M-1 Leafless; M-2 in Leaf | Fine fuel % and cedar foliage retention will result in faster ignition and spread |
| S (Slash) | Slash from logging and land clearing | Rapid spreading, moderate to high intensity surface fire |
| O1-Long | Continuous standing grass – fuel loading is 0.3 kg/m2; scattered trees; 01-a Matted; 01-b Tall | The taller, and more cured the grass, the more rapid spread; low to moderate intensity surface fire |
| O1-Short | Continuous human modified short grass | Typically low rate and spread and low fire intensity. |
Appendix 3. Photos.
2700 Herbate Road. Top left: view looking W from existing garage to existing home; top right: view from driveway of existing garage; bottom left: view from driveway looking southeast to existing garage; bottom right: view southeast from driveway. Coniferous trees along the driveway should be pruned.
Limitations
This report provides an assessment of WUI hazard and risk. Evaluation is based on professional judgment. The investigation involved a field observation. Recommended treatment pertains only to the particular site as disclosed at the time of inspection. The report was prepared considering site-specific circumstances and conditions. It is intended only for use by the client for the purpose for which it was commissioned and for use by local government regulating the activities to which it pertains.
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