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Eight trenches were excavated in close proximity to the Big Lost River (BLR) during 2002 to support a geomorphic study of historical flood patterns and potential flood hazards on the INL Site (Figure 17). The trenches were excavated to a depth of approximately 1.5 m, and ranged in length from about 20 m to about 380 m. Average trench width was 10-12 m. The BLR Trenches Revegetation Demonstration Project was initiated in the fall of 2007, at which time the trenches were backfilled and planted. Care was taken during backfill activities to minimize soil compaction and replace topsoil on the surface. Planting included drill seeding, installation of container stock, and transplanting wildings. Application of mulch and fertilizer occurred immediately after planting and supplemental irrigation was applied on four occasions using a water truck in June of 2008. Undesirable species are surveyed on a regular basis and those having the potential to significantly impact revegetation success are removed.

The monitoring plan for the project integrates two distinct approaches, frequent and rapid informal assessments and detailed, annual formal assessments. Activities completed during informal site inspections include: photo documentation, survey for noxious weeds, pulling crested wheatgrass (Agropyron desertorum), repairing electric fences, and assessing water stress, mortality, and seed production for native, perennial species. Results of the informal assessments are used to guide short-term maintenance actions.

Formal revegetation assessments focus on the acquisition of objective cover data using a statistically-rigorous experimental and sampling design. Initially, cover data will be collected on each of the trenches and compared to general background cover values estimated from appropriate surrounding plant communities. As vegetative cover on the trenches begins to approach values of those estimated from background plant communities, site-specific control data will be collected adjacent to the trenches using a similar sampling design. Statistical models will be used to compare the cover of target species or groups of species on the trenches to the cover of the same entities on the control sites. Data collection for formal revegetation assessments is completed coincident with peak biomass. In 2009, formal assessment sampling was conducted in mid-July. Results from cover sampling are used to assess progress toward meeting a goal of 70 percent of background native, perennial cover in order to be considered for release from regulatory oversight.

The primary purpose of the Big Lost River Trenches Revegetation Demonstration Project is to assess the efficacy of several revegetation techniques that often are recommend but rarely employed on the INL Site, such as using container stock seedlings, providing supplemental irrigation and applying intensive weed management practices. Successfully implementing these techniques could increase the recovery rate of revegetation sites, thereby reducing the amount of time and long-term maintenance required to reach regulatory revegetation standards. Some of the techniques used for the Big Lost River Trenches Project also may reduce uncertainty associated with the outcome of revegetation on the INL Site, which also translates to increases in long-term efficiencies for revegetation and restoration projects.

All activities related to backfilling and planting were completed in 2007. Maintenance activities have been completed on at least a monthly basis from April through October 2008 and 2009. Data to support formal revegetation assessments were collected in July 2009. General estimates for background vegetation cover were obtained from plot data collected as a component of the INL Site Plant Community Classification and Vegetation Mapping Project in 2008.

Annual species were abundant on all of the trenches. Native, perennial cover values were highest at BLR-8 and fell within the range of values estimated from background plots. Native, perennial cover values were lowest at Big Loop and fell well below the range of values estimated from background plots. This result likely is related to a combination of low shrub cover in the background estimate values for this set of trenches due to a fire in 2000 and soils favoring herbaceous germination and establishment.

Informal site inspections, maintenance activities, formal revegetation assessments and stakeholder interaction will continue until all eight trenches have reached 70 percent of native, perennial background cover. Site-specific control data will be collected at the BLR-8 trenches in 2010 to support statistical hypothesis testing.

Publications, Theses, and Reports
An annual report, Big Lost River Trenches Revegetation Demonstration Project Progress Report and Formal Revegetation Assessment 2009 (Forman and Hafla 2010), was produced in support of this project.

Full Report (pdf format)