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

Powerline Flood Retarding Structure
Pinal County, AZ
Draft Supplemental Watershed Plan
and Environmental Assessment
Climate and Topography: The upstream contributing watershed for the Powerline FRS originates in
the southwest facing slopes of the Superstition Mountains with steep mountain topography. The
mountains drain onto a wide alluvial fan with various land uses and flattening topography. The
downstream inundation area is a largely flat topography with mixed land uses. The climate is
typical of the arid southwest with mild winters and hot summers. Rainfall is limited and typically
occurs in either the winter wet period or the summer monsoon period.
Watershed size: Approximately 11,264 acres in the downstream breach inundation area;
approximately 29,952 acres in the upstream contributing watershed.
Land Uses: The downstream area consists of open space, residential and commercial/industrial
developments, agriculture and open space. The upstream contributing watershed consists primarily
of open space.
Land Ownership Information (downstream area): Private Land – 87%, State/Local 12%, Federal
1%.
Population and Demographics: The current residential population in the study area downstream of
the FRSs is estimated at 91,700. The population at risk of flooding downstream of the Powerline
FRS is estimated at 27,100. The majority of the total population encompassing the Powerline,
Vineyard Road and Rittenhouse Flood Retarding Structures (PVR FRSs) area is White which
comprises 86.9% of the population. The total minority population is 13.1% with the breakdown of
racial and ethnic demographics as follows: Black or African American 1.4%; American Indian and
Alaskan Native 1.0%; Asian 1.2%; Native Hawaiian and other Pacific Islander 0.2%; Other 6.6%;
Population of Two or More Races/Not Hispanic or Latino 2.8%. The percentages of racial, ethnic
and total minority populations appear to be consistent with those of the surrounding communities.
The demographics were conducted on the area defined as the ‘Social Population Demographics
Existing Conditions Study area’ (SPDECS) for the Powerline, Vineyard Road, and Rittenhouse
FRSs and documented in the “Social, Population and Demographics Existing Conditions Study”
(Kimley-Horn July, 2010). The analysis approach was based on Census Track and Block Groups
within and adjacent to the SPDECS study area. The source of the data is the decennial Census
2000 data sets from the United States Census Bureau (Census 2000). The SPDECS study is
summarized in Appendix D.
The median household income for the PVR FRSs area is between $32,055 and $101,124 for an
average median household income of $60,789. This represents a slightly higher median household
income than the neighboring communities which range between $33,170 (Apache Junction) and
$68,032 (Gilbert) for an average median household income of $58,399.
Resource Concerns: The following is a listing of the relevant resource concerns considered during
the scoping process.
Aesthetics: Structures are significant features on landscape.
Cultural Resources: Previous cultural resources surveys and research in the vicinity suggest that
there would be a significant number of archaeological sites located within the area of potential
effects (APE) for the project.
Environmental Justice: Minority and disadvantages populations downstream of dam are at high risk
if no action is taken.
USDA- NRCS Page 1-2 January 2013
Kimley-Horn and Associates, Inc.