Biomass removal and thinning to protect sequoias, wildlife habitat and communities-Wawona Road to Merced Grove

Yosemite National Park » Biomass removal and thinning to protect sequoias, wildlife habitat and communities-Wawona Road to Merced Grove » Document List

This project reduces post-drought and post-fire fuels to protect the Merced and Tuolumne groves of giant sequoias, Yosemite Valley, the communities of Yosemite West, Wawona, El Portal, Foresta, Yosemite Village, significant Pacific fisher and great grey owl habitat, prehistoric and historic archeological sites, and improves safety for the public and first responders. Immediate actions are needed to protect these areas from high severity fire. The goals are reached by thinning conifers <20" diameter, standing dead trees, and removing dead and down trees that died after the 2012-2016 drought. Biomass are either removed and hauled offsite or piled and burned.

This project incorporates and expands PEPC 41967 Merced Grove Special Management Area Burn Preparation and Fire Fuels Thinning Project-Phase I into Phase II. It follows the 2004 Fire Management Plan EIS (FMP) with several additions. Actions are described for those that adhere directly to the FMP and the Forestry Programmatic CE (PEPC 79616) and then those actions that tier off the FMP. Tiered actions are specifically called out with an explanation how it differs from FMP.

Description of actions

• Cut down hazard trees following criteria of the Forestry CE.
• Cut down <20" diameter ponderosa pine, incense cedar, white fir, and douglas-fir. Flush cut stumps. Post removal tree density should be left at 24-130 trees/acre to mimic pre-settlement tree density.
• Remove biomass including recently dropped hazard trees. Haul biomass to the nearest mill, co-gen plant, or other biomass processing plant. Remove biomass with rubber balloon tires, skidding, winching, or with tracked equipment (*FMP does not specify if tracked equipment is permitted along road corridors). Equipment will go off road but will not enter Wilderness. Any value from biomass removal will offset project costs and will not support park operations.
• Chip, lop and scatter, or pile and burn limbs as appropriate.

Location of action and extent

The work extent of each segment is 200 feet from centerline on both sides of the road unless otherwise noted. No work will occur in Wilderness. Work may not occur in areas because the area is too steep, work area is unsafe, or there is sensitive species or cultural resource concerns. Work will only occur in sensitive sites with appropriate mitigations and/or monitoring from subject matter experts. Actions are described as road segments, road segments that expand the FMP, Merced Grove treatments, and well and stream gage installation.

Road segments
• Wawona Road-Alder Creek to South Side Drive: 16.68 miles, 810.77 acres
• Henness Ridge Road-Wawona Road to park boundary: 0.79 miles, 41.15 acres
• South side drive-Wawona Road to Big Oak Flat Road: 1.86 miles, 92.72 acres (*FMP does not specify roadside thinning on south side drive)
• Big Oak Flat Road-El Portal Road to Merced Grove parking lot: 13.22 miles, 643.3 acres
• Tioga Road-Big Oak Flat Road to Gin Flat: 3.76 miles, 184.44 acres
• Merced Grove Trail: 1.21 miles, 64.6 acres
• Merced Grove Truck trail north-Merced Grove parking lot to Y: 1.21 miles, 61.33 acres

Expanded road segments
The following two road segments expand what is prescribed in the FMP. These segments extend the area from beyond the road corridor uphill to the ridgeline where there is a pre-existing dozer line. Removing fuels in this area decrease the risk of losing a prescribed fire from a mid-slope holding line. Merced Grove Truck Trail is divided in two segments as the north segment was burned during the Ferguson fire. Merced Grove Truck trail south also protects the boundary area as specified in the FMP.
• Merced Grove Truck trail south-Y to park boundary: 68.25 acres, 2.57 miles
• South Landing Road-Big Oak Flat Road to park boundary-63.35 acres, 2.12 miles

Merced Grove
Merced Grove is split into two areas. The treatment is the same, but the rationale for the treatment differs and is specified below.
• Merced Grove of sequoias (~60 acres). Heavy equipment may not operate off-road to avoid damaging sequoia seedlings or sequoia roots. (* FMP calls for removal of conifers <12" diameter in sequoia groves. It has been 17 years since the FMP was written. Tree density far surpasses the on the ground conditions and removal of 12" diameter trees is insufficient to protect the sequoias.)
• Downhill of sequoias (~60 acres). FMP specifies removal of <20" conifers in boundary areas such as this one. Thinning conifers also reduces the threat of fire entering the grove from below.

Well and stream gage installation
This project also includes monitoring to evaluate ground and surface water pre- and post-treatment. Installations would consist of three soil moisture/snow depth nodes and one stream gage. The soil moisture/snow depth nodes would consist of a 10 foot long 2-inch diameter aluminum pole anchored with a post pounded into the soil. A snow depth sensor would be mounted to the end of a three foot cross piece mounted to the top of each pole. Each pole would also contain a 10 x 10 inch solar panel, a 10x10x5 inch datalogger box, a 7x7x6 inch white solar shield housing for temperature and humidity sensors, and associated conduit for wiring along the pole. Soil moisture probes would be located to a depth of one meter. Two of the nodes would be co-located with fire effects plots in the grove, which would sample the northeast facing slope of the Grove on the west side of Moss Creek. The 3rd node would be located in the valley bottom at a lower gradient site on the west side of Moss Creek.

The stream gage design would be consistent with other low-visibility and low-impact sites in Yosemite. The gage would consist of an electronic pressure transducer encased in a pvc pipe section approximately 1-2 ft long. The PVC pipe would be secured with hose clamps to 3-5 pieces of rebar pounded into the stream bed. The stream gage would be located near the road crossing of Moss Creek. A small barologger approximately 6 inches long and 1.5 inches in diameter would be screwed onto a nearby tree to measure barometric pressure.