Background

The Salt River Federal Reclamation Project (SRFRP) is a federal Reclamation project, operated and maintained by Salt River Project Agricultural Improvement and Power District and the Salt River Valley Water Users’ Association (collectively SRP) in accordance with contracts with the United States. The SRFRP includes an approximately 248,000-acre service area in Maricopa County, Arizona, as well as infrastructure in portions of Maricopa, Gila, Yavapai, and Coconino counties, Arizona. The SRFRP water supply is developed from seven storage dams on the Salt River, Verde River, and East Clear Creek and from water withdrawn from approximately 270 groundwater wells throughout the service area. The SRFRP delivers water through more than 1,200 miles of canals, laterals, and ditches to users including shareholders, cities, towns, irrigation districts, Indian tribes, and individuals.

Horseshoe Dam is an earthen embankment dam on the Verde River constructed in 1946. Horseshoe Dam has been modified, including in 1949, to add spillway gates funded by the City of Phoenix. The total storage capacity of Horseshoe Dam and Reservoir was originally 144,030 acre-feet (AF) but, due to sedimentation, is now approximately 108,000 AF.

Bartlett Dam is a multiple-arch concrete dam on the Verde River constructed in 1939 and modified in 1994 and 1996 to address the National Dam Safety Program Act, in the Water Resources Development Act of 1996 (Pub. L. 104-303, 110 Stat. 3658). Bartlett Dam is downstream of Horseshoe Dam. The storage capacity of Bartlett Reservoir in 1939 was 182,608 AF. Due to sedimentation, Bartlett Reservoir now has a capacity of approximately 168,000 AF.

The Verde Reservoirs Sediment Mitigation Project (VRSMP) Feasibility Study was authorized by the Infrastructure Investment and Jobs Act (P.L. 117-58). The purpose of the feasibility study is to analyze options to address the problem of sediment accumulation, loss of storage capacity due to sedimentation, and water supply resiliency in the Verde River reservoirs of the SRFRP. The results of the feasibility study, which includes an environmental review and financial analysis, will be used to make recommendations to the U.S. Congress on how best to address the problem. The VRSMP Environmental Impact Statement (EIS) will analyze the environmental impacts of the alternatives detailed in the feasibility study. As part of the feasibility study, Reclamation is preparing a feasibility report to summarize  and present the planning, engineering, economic, environmental, and social analyses of the alternatives analyzed.

The VRSMP will evaluate alternatives to restore lost storage capacity at Horseshoe Reservoir and mitigate sediment accumulation, while addressing future water-supply resiliency. The VRSMP Feasibility Study will investigate and analyze: (a) the design of the two Bartlett Dam modification alternatives identified as viable for feasibility-level analysis in the VRSMS; (b) at least one non-structural sediment and water management alternative; (c) a no-action alternative; and (d) other alternatives developed through the NEPA process.

Cooperating Agencies

The EIS also supports other Federal decisions, including those of the U.S. Army Corps of Engineers (USACE), U.S. Fish and Wildlife Service (USFWS), and U.S. Forest Service (USFS). Other entities will be considered, as necessary, during the EIS process.

Purpose of and Need for the Proposed Action

The purpose of the proposed action is to restore lost storage capacity from sedimentation at Horseshoe and mitigate reservoir sediment accumulation while addressing future water-supply resiliency through increased surface-water yield from the SRFRP’s Verde River reservoir system.

As of a 2021 sediment survey, approximately 36,000 AF of water-storage capacity has been lost to sediment accumulation in Horseshoe Reservoir. This capacity loss represents approximately one-fourth of Horseshoe Reservoir’s original capacity. Additionally, Bartlett Reservoir has lost approximately 15,000 AF of capacity to sedimentation. Combined, Horseshoe and Bartlett reservoirs sediment losses amount to approximately 15% of the total original storage capacity of the SRFRP Verde River reservoir system. Today, it is estimated that Horseshoe Reservoir loses approximately 500 AF of storage capacity per year from sedimentation, and Bartlett Reservoir loses approximately 180 AF per year. This loss of capacity on a highly variable river system, coupled with the increase in hydrologic variability anticipated with climate change, creates concerns about future SRFRP water deliveries. Restoring lost storage capacity and mitigating sediment-accumulation impacts on storage capacity in the Verde River reservoir system would promote resiliency of future SRFRP water deliveries, aid the United States in meeting certain federal obligations, and ensure that the SRFRP continues to fulfill its authorized purposes.

Central Arizona water users primarily rely on surface water from the Salt, Verde, and lower Colorado rivers, groundwater, and treated effluent. Changes or variations in the availability of lower Colorado River water supplies and groundwater resulting from, among other things, extended drought and climate change highlight the need for maintaining the resiliency of the water supplies from the Verde River. The Proposed Action provides opportunities to benefit Indian tribes and Arizona water users through the provision of additional water supplies, dam safety, flood routing, and recreation.

Principles, Requirements, and Guidelines

As part of the environmental analysis process, the Federal Principles, Requirements, and Guidelines for Water and Land Related Resources Implementation Studies (PR&Gs) will be applied to examine the various technical, economic, hydrologic, recreation and ecosystem services considerations of each alternative, including the No-Action Alternative. The requirements of a PR&G analysis are unique to the feasibility study process and are not included in the  Department of the Interior’s NEPA implementing regulations. The PR&Gs govern how federal agencies evaluate proposed water-resource projects, programs, activities, and related actions involving federal investment and include the following components:

• The Principles and Requirements for Federal Investments in Water Resources (P&R) outline the overarching concepts that the federal government seeks to achieve through policy implementations and requirements for inputs into analysis of federal investment alternatives (CEQ 2013).

• The Interagency Guidelines (IG) provide guidance for determining the applicability of the P&R for affected federal agencies, including but not limited to the Department of Interior, U.S. Department of Agriculture, and USACE (CEQ 2014).

• Agency Specific Procedures (ASP) are used for identifying which programs and activities are subject to the PR&G. DOI’s Agency Specific Procedures for Implementing the Council on Environmental Quality’s Principles, Requirements, and Guidelines for Water and Land Related Resources Implementation Studies (707 DM 1 Handbook) is its ASP (DOI 2015).

The PR&Gs are not regulations and do not substitute for or supersede NEPA requirements or other planning requirements required by law; nevertheless, we will integrate relevant portions of the PR&Gs analysis from the Feasibility Study into the EIS.

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For more information on the VRSMS, VRSMP Feasibility Report and EIS, please visit Reclamation’s project website, or email VRSMP@usbr.gov. If you would like to receive email notifications and updates on the VRSMP, please email VRSMP@usbr.gov with subject line "Add me to Email List."