Carson City Sutro Regional Detention Basin Scoping
Terraphase was engaged to support the development of a Federal Emergency Management Agency (FEMA)-funded mitigation project in Carson City, Nevada for the Sutro Terrace Storm Drain system through a comprehensive set of technical studies and planning documents. The work aimed to refine prior analyses, assess environmental and cost feasibility, engage stakeholders, and develop a funding-ready project plan to reduce flood and debris flow risk in the area.
Scope of Services
Terraphase delivered a full suite of planning and analysis services, including refined hydrologic and hydraulic modeling using FLO-2D, environmental assessments, agency coordination, and cost-benefit evaluation. The team also led early-stage public outreach, developed preliminary designs and cost estimates, and compiled all project documentation into a Scoping Design Report (SDR). The SDR and supporting materials were presented to the Technical Advisory Committee (TAC) for review and finalized for future funding pursuits.
Notable Accomplishments
- Refined storm drain modeling using FLO-2D, including fire and debris flow scenarios
- Completed FEMA-compliant Benefit/Cost Analysis (BCA) using the BCA Toolkit
- Led proactive public engagement throughout project development
- Developed mitigation project scope, schedule, and budget to support future funding efforts
City of Bremerton Water Right and Mitigation Plan Support
Terraphase is providing water rights consulting services to the City of Bremerton in Washington state for Wells 9, 21, and 22. The original applications for these wells date back to the early 1990s in sub-basins that the Washington State Department of Ecology (Ecology) has since closed to new appropriations. With the introduction of the U.S. Geological Survey (USGS) Kitsap Groundwater Model in Water Resource Inventory Area (WRIA) 15, Ecology determined that approval of these applications would require evaluation through the Kitsap Model and submission of mitigation plans.
Scope of Services
Terraphase is supporting the city in navigating Ecology’s updated permitting process. Our team helped identify necessary modifications to the Kitsap Model, facilitated permit extensions to align timelines for all three water rights, and prepared technical memoranda evaluating both steady-state and transient groundwater modeling scenarios and their potential impacts on nearby streams. We also collaborated with city staff to define feasible mitigation options and propose a mitigation plan and protocol. Looking ahead, Terraphase will oversee drilling and testing of a new 950-foot-deep well at the Well 9 site in 2024 to better evaluate aquifer conditions. We will also participate in technical discussions with Ecology and tribal stakeholders and prepare Reports of Examination for Ecology review under a Cost Reimbursement Agreement.
Notable Accomplishments
- Supported permit extensions to synchronize timelines for all three well applications
- Developed mitigation strategies and protocols in collaboration with City staff
- Planned and will oversee the drilling and testing of a new 950-foot-deep well at Well 9
Washoe County Golden Valley Aquifer Recharge Assessment
In a rapidly developing region near Reno, Nevada, aquifer recharge efforts were originally supported by comprehensive technical evaluations conducted in the 1980s and 1990s. The aquifer recharge efforts influenced well performance and changes in the recharge practices had potential for affecting several hundred water right users. The original technical data was sufficient to convince stakeholders to invest in construction and operation of the aquifer recharge program. Part of the initial investigation into the feasibility of aquifer recharge was the development of a groundwater flow model. Steady-state and transient groundwater flow models for the basin were updated in 2017, and the transient model was calibrated using data collected prior to ceasing aquifer recharge operations. Other components included analysis of surface water availability, the economic feasibility of the project, and the chemistry of the basin groundwater and proposed infiltration water.
Scope of Services
Terraphase’s approach focused on evaluating how basin conditions have changed since the original program design and utilizing that new understanding to revise and recalibrate the 2017 model to current conditions. Our team assessed the adequacy of historical data and supplemented it with new information, including bedrock surface development from over 100 wells, pumping depths from 530 domestic well logs, and hydraulic conductivity derived from 140 well yield records. This work supported the refinement and recalibration of the MODFLOW groundwater model, allowing for predictive scenario analysis to inform future aquifer recharge decisions. The Terraphase team also developed a conceptual site model and prepared a final technical report and public presentation.
Notable Accomplishments
- Integrated new and historical data to refine basin understanding
- Developed and calibrated a MODFLOW model incorporating over 100 well records
- Evaluated over 500 domestic well logs to characterize pumping depths and
derived hydraulic conductivity values from 140 well yield data sets - Delivered a comprehensive conceptual site model and predictive groundwater analysis
- Informed future aquifer recharge strategies with calibrated model scenarios
- Provided final technical documentation and supported public engagement through presentations
- Our analysis gained wide public support and was selected for a paper presentation at the February 2023 Nevada Water Resources Association conference.
