B08_Att_7_Wildfire_Report_2023-06-06.pdf

National Park Service U.S. Department of the Interior

Denver Service Center

31405867.008

REPLACE OBSOLETE HOUSING AT DEVILS TOWER NATIONAL MONUMENT

Report of Wildfire Risk Assessment

June 06, 2023

March 28, 2023

Mr. Adam Lamb, AIA, NCARB Project Manager, Architect Croft & Associates, PC 3380 Blue Springs Road Kennesaw, Georgia 30144

Subject: Report of Wildfire Risk Assessment

Replace Obsolete Housing at Devils Tower National Monument Project Number 31405867.008

Dear Mr. Lamb:

Thank you for this opportunity to be of service to Croft & Associates, PC on the Replace Obsolete Housing at Devils Tower National Monument Project. WSP USA Environment & Infrastructure Inc (WSP) has completed a wildfire risk assessment for the proposed housing site in the southwest portion of the

Monument. This report summarizes the potential wildfire risk to the site, based on a desktop review of regional wildfire risk data and history and site vegetation and topography coupled with a Fire Hazard

Severity Form prepared by the National Park Service (NPS).

1.0 Site Overview

The following maps and figures show the location of the proposed housing project. The location of the project area is near the southern boundary of Devils Tower National Monument, near the floodplain of the

Belle Fourche River as depicted on the following figure.

WSP Environment & Infrastructure Inc.

920 E. Sheridan St., Suite A

Laramie, WY 82070 T: 307-460-3249 www.wsp.com

Report of Wildfire Risk Assessment 31405867.008 Replace Obsolete Housing at Devils Tower March 28, 2023

Figure 1: Devils Tower Area Overview

Topography and Vegetation

The Housing Site is mostly flat to gently sloped, on the edges of the floodplain of the Belle Fourche River, thus there is not the presence of terrain features that would exacerbate fire behavior. Based on aerial imagery from

Figure 3 ESRI (leaf off), Figure 4 NAIP 2022, and Google Maps Imagery the Housing Site contains and is surrounded by trees, the vegetation is a mosaic of ponderosa pine woodlands and mixed-grass prairie, with a narrow riparian corridor of cottonwoods and some Aspen. There are large areas of open space/grassland, agricultural land west and south of the Housing Site; this could prove beneficial as a fuel break for wildfires to the west. Other existing fuel breaks include the Belle Fourche River to the south and east of the site, and Devils

Tower National Monument Road to the north. Most of the project area is maintained through mowing and landscaping which greatly reduces fuels.

Figure 2: Proposed Improvements at Devils Tower Housing Site

Figure 3: Devils Tower Housing Site Leaf-Off

Figure 4: Devils Tower Housing Site Leaf-On

Figure 5: Devils Tower Housing Site Infrared

2.0 Regional Wildfire Risk Assessment

Regional Wildfire History

The National Interagency Fire Center (NIFC) maintains data of past and present perimeter and point GIS layers for fire on public lands throughout the United States. NIFC is home to the national fire management programs for the Bureau of Indian Affairs, Bureau of Land Management, U.S. Fish and Wildlife Service, National Park Service, USDA Forest Service, along with partners including the National Association of State

Foresters, the U.S. Fire Administration, and the National Weather Service. A Department of Defense liaison was added as a permanent partner at NIFC in 2008. Some fires may be missing altogether or have missing or incorrect attribute data. Some fires may be missing because historical records were lost or damaged, fires were too small for the minimum cutoffs, documentation was inadequate, or fire perimeters have not yet been incorporated into the database. Also, agencies are at different stages of participation. For these reasons, the data should be used cautiously for statistical or analytical purposes.

Figure 6 below shows a map of past wildfires that have affected the area in and around the National

Monument based on the National Interagency Fire Center database. The three largest recorded fires are west of the Home Site. The largest was the Belle Fourche prescribed burn on May 7, 2013 which turned into an uncontrolled wildfire, which was 59 acres. A detailed description of the event can be accessed here:

https://www.nps.gov/ngpfire/Documents/Rx_DETO_Belle_Fourche_13.pdf This indicates that there are fuels that can carry fire near the site, but those fuels are managed as evidenced through the prescribed fire. The

2021 Buffalo CA (54 acres) and Hauber CA (26 acres) wildfires were determined to be of natural causes.

Other fires within and near the Devils Tower parcel were small events.

Figure 6: Devils Tower Area Fire History

Regional Wildfire Threat and Risk

The Wyoming Wildfire Risk Assessment Portal (WYWRAP) was used to assess regional wildfire risk. This web-based application provides immediate, on-line access to West Wide Wildfire Assessment data calibrated for

Wyoming to help communities, fire departments, emergency planners, and land management agencies collectively prepare for and be resilient to wildfires by facilitating effective, efficient, and consistent data and information exchange. This allows for an enhanced public awareness of wildfire risk and helps to build capacity for planning efforts and develop fuels treatment priorities.

Figure 7 shows the areas at greatest threat of wildfire near the project area, based on WYWRAP data. Wildfire

Threat is an index related to the likelihood of an acre burning. The Fire Threat Index integrates the probability of an acre igniting and the expected final fire size, based on the rate of spread in four weather percentile categories, into a single measure of wildfire threat. The Housing Site project area includes areas of High and

Medium Wildfire Threat with the highest rating on the eastern portion of the project site.

Figure 7: Devils Tower Area Wildfire Threat

Figure 8 shows the areas at greatest risk of wildfire, based on WYWRAP data. Within the WYWRAP, the data layer that defines wildland fire risk is the Fire Risk Index (FRI). The Fire Risk Index is calculated from a combination of the Fire Threat Index (possibility of suffering harm or loss) and the Fire Effects Index (harm or loss). The entire project/housing site is within the Medium Risk area with Low Risk just west of the site and

National Monument boundary.

Figure 8: Devils Tower Area Wildfire Risk

3.0 Site Specific Fire Hazard Severity Analysis

As part of the survey, the NPS inspected the project area and buildings for site-specific fire hazards. This was captured through a Fire Hazard Severity Form that allowed the scoring on the following categories:

subdivision design, vegetation, topography, roofing material, fire protection-water source, existing building construction materials, and utilities. A scoring was provided for each relevant subcategory. In general, the points applied were low, representing low hazard for most all categories and an overall score of 34. A score of 40-59 represents “Moderate” Hazard. The highest rating was applied to the existing building construction materials, a 10 out of 10, for combustible siding and deck. The site was assessed as Medium for fuel types and ranked favorably for defensible space (70% or more of the site). While there is only one road into the site, there is a cul-de-sac turnaround. The full assessment is included as an attachment.

4.0 Conclusions and Recommendations

Based on the regional aspects of this assessment the Project Site has a medium to high Fire Threat rating

(likelihood) based on regional scale mapping, and a medium Fire Risk rating, though fuels breaks exist on nearly every side of the property. The WYRAP results are useful at a larger scale but the site-specific conditions ultimately determine the actual risk for a specific location. The site specific assessment yielded some risk to existing buildings, but an overall low hazard rating. However even low rated sites can experience wildfire impacts. An assessment of past wildfires in the region determined that the area has an active history. Some recommendations to improve fire safety are noted below.

Recommendation 1: Vegetation Management and Defensible Space

The National Fire Protection Association (NFPA) research around home destruction versus home survival in wildfires points to embers and small flames as the primary way that homes ignite in wildfires. Embers are burning pieces of airborne wood and/or vegetation that can be carried more than a mile through the wind, and can cause spot fires and ignite homes, debris, and other objects. Experiments, models, and post-fire studies have shown that homes ignite due to the condition of the home and everything around it, up to

200 feet from the foundation. This is called the Home Ignition Zone (HIZ).

To increase a structure’s chance of surviving a wildfire, fire-resistant building materials and limiting the amount of flammable vegetation in the three home ignition zones is highly recommended. The zones include the Immediate Zone: (0 to 5 feet around the house), the Intermediate Zone (5 to 30 feet), and the

Extended Zone (30 to 100 feet). The following figure shows distance measurements for the Site from GIS for reference purposes.

It was observed that there will be an optional gathering place with fire pit installed. This proposed firepit could potentially be near existing tree canopy. It is recommended that the firepit should be well protected and only used in conjunction within open fire regulations.

Figure 9: Existing Site Distance Measurements

The landscaping and maintenance recommendations recommended by Firewise are strongly encouraged in the Immediate Zone around the structure. The attached Firewise Pamphlet has general recommendations for vegetation management in the home ignition zones. These practices are highly recommended to limit the potential for structure ignition.

Existing coniferous trees should be limbed of ladder fuels and thinning of these trees should be considered.

Based on aerial imagery, aspen trees are present at the site. These trees should be maintained and encouraged, as these species are less flammable.

Recommendation 2: Maintain and Enhance Existing Fuel Breaks

The site benefits from existing fuel breaks. These should be maintained, and possibly enhanced by regular mowing of shoulders along the Devils Tower National Monument Road.

Recommendation 3: Employ Fire Resistant Construction Where Possible

The attached Firewise Pamphlet has general recommendations for fire resistant construction. These are highly recommended to limit the potential for structure ignition.

Recommendation 4: Evacuation Preparedness

A plan to evacuate the site should be developed in the event of a wildfire, with pre-assembled “go-kits” of essential items and important documents or equipment.

WSP appreciates the opportunity to provide these services to Croft. Please contact us if you have any questions or if we may be of further assistance.

Sincerely, WSP USA Environment & Infrastructure Inc.

Jeff Brislawn, CFM Vice President Hazard Mitigation and Emergency Management Team Lead

Attachments: Fire Hazard Severity Form Firewise Pamphlet

ATTACHMENTS

Fire Hazard Severity Form (Completed by NPS, 2023)

Attachments

Firewise Pamphlet

Attachments