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Preserve Infrastructure

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If you drive along Highway 89 between Downtown Prescott and the Granite Dells, or if you spend much time in Watson Woods Riparian Preserve, you would have a hard time not noticing the construction project that has been occurring over the last several months. Last year the City of Prescott approached Prescott Creeks with plans to install a new Sewer Main from the Sundog Wastewater Treatment Plant across Watson Woods and along Highway 89 to the north. This project is the first phase of a much needed overhaul of Prescott’s aging sewer system, with the end goals of moving all of the City’s wastewater treatment to the treatment plant near the airport and replacing the old pipes with modern, higher capacity pipes. As the managing organization for the City-owned 126-acre Preserve, Prescott Creeks is responsible for working with the City on infrastructure projects that impact Watson Woods.

One of two black hawk juveniles born in 2017 in Watson Woods Riparian Preserve.

The initial plan the City presented to bring the sewer line across Watson Woods specified open-trenching through the Preserve and across Granite Creek, which would have caused extensive impacts to restored riparian habitat (see additional info below) and would have damaged nesting habitat for Common Black Hawks among other species of concern. Common Black Hawks (an uncommon bird in this area, contrary to their name) require flowing water and mature trees to nest and feed their young – in Arizona, they seem to prefer building nests in large cottonwoods. The riparian cottonwood-willow forests in which Black Hawks reside are among the rarest biotic communities in North America and have been in decline due to development, groundwater extraction and surface water diversion, grazing, and other human disturbances. Because of their sensitivity to disturbance, the presence of nesting Black Hawks in Watson Woods indicates a measure of success in the restoration and protection of our riparian areas.

Through negotiation with the City and their contractor, Fann Contracting, the plans ultimately shifted to using a Horizontal Directional Drill to bore under the Preserve, which greatly reduced impact on riparian habitat and the Granite Creek channel. Drilling turned out to be a win-win solution for all involved. Surface disturbance was largely limited to only the drill’s entrance and exit pits and the trench that allowed connection from the drill pit to the Sundog Wastewater Treatment Plant. This meant impact was focused mainly on upland grassland and shrubby habitats. The contractor has recently seeded these areas with a mix of native grasses, which will help accelerate the return of upland plants to hold soil in place and begin the healing process.

Installation of the 12-inch sewer main line in Watson Woods

This winter, after the deciduous trees have dropped their leaves and begun their seasonal dormancy, Prescott Creeks will work to mitigate the damage that did occur within the Preserve. It is during this period of dormancy that harvesting and planting pole cuttings (clones) of cottonwoods and willows is the most successful. Revegetation with both pole cuttings and with nursery vegetation will take place within Watson Woods Preserve in areas where construction impacts were unavoidable. To do this, we will need your help! If you are interested in making a positive impact, please consider becoming a volunteer and keep an eye out for forthcoming announcements.


Additional Info:

Established as a Riparian Preserve in 1995, Watson Woods had previously been the site of sand and gravel mining and, prior to the construction of the now closed landfill adjacent to Prescott Lakes Parkway, it was the unofficial town “dump”. As you may imagine, the habitat around Granite Creek had been almost completely removed and the landscape was heavily altered, with large mounds and pits scattered throughout. After over a decade of planning, Prescott Creeks implemented a significant restoration project in the Preserve, with the bulk of the work completed between 2009 and 2013. This $1.6 million project was funded primarily by the Arizona Water Protection Fund and Arizona Department of Environmental Quality, and was supported by the City of Prescott. During the restoration, the Granite Creek channel within Watson Woods was realigned and reshaped to be more stable and tens of thousands of cottonwood and willow trees were planted with the goal of reestablishing ecosystem services including reducing erosion and stabilizing the creek channel, filtering pollutants, locally reducing air temperature and increasing humidity, and providing habitat to which wildlife could return.

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