Powerline Plan and Environ. Assessment Jan. 2013 - Flood Control ...

Powerline Flood Retarding Structure
Pinal County, AZ
Draft Supplemental Watershed Plan
and Environmental Assessment
include scatters of artifacts on the surface, or artifacts with remnants of just one or a few
roasting pits, agricultural features, and/or other non-habitation features) or historical
sites (which might include homesteads, farming or ranching features, or simply scatters
of historical artifacts). Most of the remaining sites would be smaller prehistoric
habitation sites, with up to two relatively large prehistoric habitation sites.
2. Threatened and Endangered Species – Survey protocol for the Tucson shovel-nosed snake
has not been published by the USFWS. Prior to construction the status of the Tucson
shovel-nosed snake on the USFWS threatened, endangered, proposed, and candidate list
will be re-verified (i.e. status changed from candidate to threatened) and coordination
with the USFWS will be undertaken to determine if a survey protocol has been
established and/or if a survey is required. If this species is observed construction will
cease until measures can be taken to ensure the preservation of the snake and/or its
habitat. Prior to start of construction, the project area will be canvassed for tortoises
and, if any tortoises are discovered, AGFD guidelines (October 2007) will be followed.
Prior to start of construction, a survey for burrowing owls will be conducted in the
disturbance area following the AGFD protocol (January 2009). As a result of the
actions described above, there will be no effect on federally threatened and endangered
species or their critical habitat due to implementation of this alternative. The abovementioned
mitigation measures will be utilized to minimize impacts to special status
species.
3. Vegetative Community - Areas disturbed associated with construction activities will be
hydro-seeded with native mix. Approximately 120 acres of mesquite bosque will be
impacted. Mesquite bosque mitigation may include planting new tall-pot mesquite trees
(approximately 60 acres) and salvage of some mature mesquite trees and transplanting
in designated areas (e.g., along Powerline Channel and potential mitigation area at north
end of Vineyard Road FRS). The Sponsor and NRCS will coordinate with ASLD
regarding trees along the existing low flow channel along the Powerline FRS.
Mitigation plans will be refined during final design.
Major Conclusions: The decommissioning of the Powerline FRS and replacement of the dam with a
channel will remove the dam from ADWR jurisdiction. The channel will continue to provide 100-
year flood protection for the downstream benefitted area. This alternative will reduce the risk of
catastrophic failure of the existing structure and thus reduce the risk of loss of life and property. No
significant adverse environmental effects will result from implementation of this project.
Areas of Controversy: None.
Issues to be Resolved: The Powerline channel will need to meet Flood Control District and NRCS
design requirements for open channel flow. If portions of the channel include embankment for the
purpose of providing channel freeboard, the embankments may need to meet the Federal
Emergency Management Agency’s (FEMA) requirements for levee certification.
Evidence of Unusual Congressional or Local Interest: None
This report is in compliance with executive orders, public laws, and other statues governing the
formulation of water resource projects.
USDA- NRCS Page 1-5 January 2013
Kimley-Horn and Associates, Inc.