Assessment Workshop for Colusa Groundwater Authority Board of Directors

COLUSA GROUNDWATER AUTHORITY BOARD OF DIRECTORS ASSESSMENT WORKSHOP JUNE 3, 2025 1

ASSESSMENT APPROACH The proposed Assessment is intended to fund CGA s core services, which provide a benefit to parcels within CGA (irrigated parcels in particular). These costs will contribute to: SGMA compliance and management of the Subbasin. Project and Management Action (PMA) planning and implementation support. Addressing data gaps related to water use within the Subbasin, which will create a better understanding of groundwater use on a parcel scale and help CGA make decisions regarding demand management. Future costs related to projects are intended to be generated in a manner that further acknowledges the relative benefit provided to specific parcels. This may be addressed with an extraction approach and/or with area-specific funding both of which would take into account relative groundwater use on a parcel basis. 2

COSTS AND SERVICE CATEGORIES Professional Services Professional Services Budget Administrative SGMA Compliance Admin Components $349,250 $72,500 $284,250 $706,000 General administrative costs, SGMA compliance costs, and administrative PMA components. Subtotal Planning Services Long-term funding planning, project implementation planning, and study implementation. Planning Services Budget Long Term Funding Planning Project Implementation Study Implementation $50,000 $40,000 $95,000 $185,000 Groundwater Sustainability Services Subtotal Domestic well mitigation program and demand management mitigation program. Groundwater Sustainability Services Budget Domestic Well Mitigation Demand Management Mitigation $250,000 $850,000 $1,100,000 Subtotal Total: $1,991,000 3

LAND USE GROUPS Non-Irrigated lands that do not irrigate with groundwater or surface water. Groundwater Only lands that irrigate with only groundwater (no surface water access). Mixed Use lands that irrigate and have access to both groundwater and surface water. 4

1. PROFESSIONAL SERVICES Scoring factors: Percentage Allocation (a) 1. Basin Management 2. SGMA Compliance Land Use Subtotal Basin Management. SGMA Compliance. Relative Weight (%) 50% 50% 100% 100.0% (Scored 1 to 10) 2 10 10 (Scored 1 to 10) 2 10 10 Rationale: Non-Irrigated Groundwater Only Mixed Use 2 10 10 9.1% 45.5% 45.5% Non-Irrigated parcels receive a lesser degree of benefit but do benefit from Basin Management and SGMA Compliance. Costs Professional Services Total Annual Costs $706,000 All irrigated parcels benefit from Basin Management and SGMA Compliance, particularly from maintaining local control of the Subbasin and improved water supply management. Land Use % Allocation (a) Total Acres (b) 9.1% 45.5% 45.5% Benefit Units (a*b) 6,176.82 32,230.91 119,469.55 Rate/Acre ('c) $0.41 $2.03 $2.03 67,945 70,908 262,833 Non-Irrigated Groundwater Only Mixed Use 5

2. PLANNING SERVICES Scoring factors: Percentage Allocation 1. Project Preparation 2. Data Management Land Use Subtotal Project Preparation. 100.0% Relative Weight (%) 50% 50% 100% Data Management. (Scored 1 to 10) 0 10 10 (Scored 1 to 10) 0 10 10 Non-Irrigated Groundwater Only Mixed Use 0 10 10 0.0% 50.0% 50.0% Rationale: Non-Irrigated parcels do not receive a benefit from Project Preparation and Data Management. Costs Planning Budget Total Annual Costs $185,000 All irrigated parcels benefit from Project Preparation and Data Management, as they are directly affected by CGA s planning efforts. Land Use % Allocation (a) 0.0% 50.0% 50.0% Total Acres (b) 67,945 70,908 262,833 Benefit Units (a*b) Rate/Acre ('c) 0.00 35,454.00 131,416.50 Non-Irrigated Groundwater Only Mixed Use $0.00 $0.55 $0.55 6

3. GROUNDWATER SUSTAINABILITY SERVICES (1) Scoring factors: Percentage Allocation 1. Data Management 2. Access to Groundwater 3. Reliance on Groundwater Land Use Subtotal Data Management. Access to Groundwater. Relative Weight (%) 25% 25% 50% 100% 100.0% (Scored 1 to 10) 0 10 10 (Scored 1 to 10) 0 10 10 (Scored 1 to 10) 0.00 7.64 2.36 Reliance on Groundwater. Non-Irrigated Groundwater Only Mixed Use 0.00 8.82 6.18 0.0% 58.8% 41.2% Rationale: Non-Irrigated parcels do not receive a benefit from Data Management, Access to GW, or Reliance on GW. Costs Groundwater Sustainability Total Annual Costs $1,100,000 All irrigated parcels receive a benefit from Data Management, Access to GW, and Reliance on Groundwater. Land Use % Allocation (a) Total Acres (b) Benefit Units (a*b) 0.0% 67,945 58.8% 70,908 41.2% 262,833 Rate/Acre ('c) $0.00 $4.31 $3.02 Non-Irrigated Groundwater Only Mixed Use 0.00 41,691.28 108,296.93 Groundwater Only parcels receive a higher degree of benefit stemming from Reliance on Groundwater. Note: Reliance on Groundwater uses historical AF/acre use (as noted in the GSP) to apportion benefit scoring. More info on next slide. 7

3. GROUNDWATER BALANCE SERVICES (2) Reliance on Groundwater scoring based on assumptions included in the GSP. Groundwater Only areas: 1.65 AF per acre. Mixed Use areas: 0.51 AF per acre. Ratio: 7.64 2.36 GW Pumping (AF per Acre) Approximate Weight Reliance on GW Score User Class Groundwater Only Mixed Use Total 1.65 0.51 NA 76.4% 23.6% 100% 7.64 2.36 10.00 8

SUMMARY RATE TABLE Groundwater Balance Services $0.00 $4.31 $3.02 Total Rate per Acre Professional Services Planning Services Land Use Non-Irrigated Groundwater Only Mixed Use $0.41 $2.03 $2.03 $0.00 $0.55 $0.55 $0.41 $6.90 $5.61 9

ALTERNATIVE APPROACHES Staff has developed two alternative approaches that add a fourth Land Use Group: Surface Water. Non-Irrigated: Lands that are not irrigated / not using water. Groundwater Only: Irrigated / water-using lands that have no access to surface water. Mixed Use: Irrigated lands that use both groundwater and surface water (includes the CVP Contractors). Surface Water: Irrigated lands that primarily use surface water (includes riparian users and the Settlement Contractors). Alternative Reliance on Groundwater Scoring GW Pumping (AF per Acre) 1.65 1.02 0.19 NA Approximate Weight 57% 35% 6% 100% Reliance on GW Score 5.7 3.5 0.6 10.0 User Class Groundwater Only Mixed Use Surface Water Total 10

ALTERNATIVE APPROACH SCENARIO 2 Costs Professional Services Total Annual Costs As an alternative approach, Scenario 2 adds a fourth Land Use Group Surface Water. This group incudes irrigated lands that use limited or no groundwater. $706,000 Land Use % Allocation (a) Total Acres (b) 7.4% 37.0% 37.0% 18.5% Benefit Units (a*b) 4,625.48 24,627.78 35,045.93 30,836.67 Rate/Acre ('c) $0.55 $2.75 $2.75 $1.37 62,444 66,495 94,624 166,518 Non-Irrigated Groundwater Only Mixed Use Surface Water Costs Planning Budget Total Annual Costs $185,000 Land Use % Allocation (a) 0.0% 40.0% 40.0% 20.0% Total Acres (b) 62,444 66,495 94,624 166,518 Benefit Units (a*b) Rate/Acre ('c) 0.00 26,598.00 37,849.60 33,303.60 Non-Irrigated Groundwater Only Mixed Use Surface Water $0.00 $0.76 $0.76 $0.38 Costs Groundwater Sustainability Total Annual Costs $1,100,000 Land Use % Allocation (a) Total Acres (b) Benefit Units (a*b) 0.0% 62,444 45.1% 66,495 38.8% 94,624 16.1% 166,518 Rate/Acre ('c) $0.00 $5.31 $4.56 $1.89 Non-Irrigated Groundwater Only Mixed Use Surface Water 0.00 29,999.18 36,707.59 26,796.00 11

ALTERNATIVE APPROACH SCENARIO 2 Groundwater Sustainability Services $0.00 $5.31 $4.56 $1.89 Total Rate per Acre Professional Services Planning Services Land Use Non-Irrigated Groundwater Only Mixed Use Surface Water $0.55 $2.75 $2.75 $1.37 $0.00 $0.76 $0.76 $0.38 $0.55 $8.81 $8.07 $3.65 12

ALTERNATIVE APPROACH SCENARIO 3 Costs Professional Services Total Annual Costs $706,000 As another alternative approach, Scenario 3 weights the cost of Groundwater Sustainability Services based only on Reliance on Groundwater. Land Use % Allocation (a) Total Acres (b) 7.4% 37.0% 37.0% 18.5% Benefit Units (a*b) 4,625.48 24,627.78 35,045.93 30,836.67 Rate/Acre ('c) $0.55 $2.75 $2.75 $1.37 62,444 66,495 94,624 166,518 Non-Irrigated Groundwater Only Mixed Use Surface Water Costs Planning Budget Total Annual Costs $185,000 Land Use % Allocation (a) 0.0% 40.0% 40.0% 20.0% Total Acres (b) 62,444 66,495 94,624 166,518 Benefit Units (a*b) Rate/Acre ('c) 0.00 26,598.00 37,849.60 33,303.60 Non-Irrigated Groundwater Only Mixed Use Surface Water $0.00 $0.76 $0.76 $0.38 Costs Groundwater Sustainability Total Annual Costs $1,100,000 Land Use % Allocation (a) Total Acres (b) Benefit Units (a*b) 0.0% 62,444 58.2% 66,495 35.7% 94,624 6.1% 166,518 Rate/Acre ('c) $0.00 $7.74 $4.75 $0.81 Non-Irrigated Groundwater Only Mixed Use Surface Water 0.00 38,675.66 33,794.29 10,194.98 13

ALTERNATIVE APPROACH SCENARIO 3 Groundwater Sustainability Services $0.00 $7.74 $4.75 $0.81 Total Rate per Acre Professional Services Planning Services Land Use Non-Irrigated Groundwater Only Mixed Use Surface Water $0.55 $2.75 $2.75 $1.37 $0.00 $0.76 $0.76 $0.38 $0.55 $11.25 $8.26 $2.57 14

SCENARIO RATE COMPARISON Groundwater Balance Services $0.00 $4.31 $3.02 Total Rate per Acre Professional Services Planning Services Land Use Scenario 1 Proposed Assessment Non-Irrigated Groundwater Only Mixed Use $0.41 $2.03 $2.03 $0.00 $0.55 $0.55 $0.41 $6.90 $5.61 Groundwater Sustainability Services $0.00 $5.31 $4.56 $1.89 Total Rate per Acre Professional Services Planning Services Land Use Scenario 2 Alternative Approach Non-Irrigated Groundwater Only Mixed Use Surface Water $0.55 $2.75 $2.75 $1.37 $0.00 $0.76 $0.76 $0.38 $0.55 $8.81 $8.07 $3.65 Groundwater Sustainability Services $0.00 $7.74 $4.75 $0.81 Total Rate per Acre Professional Services Planning Services Land Use Scenario 3 Alternative Approach Non-Irrigated Groundwater Only Mixed Use Surface Water $0.55 $2.75 $2.75 $1.37 $0.00 $0.76 $0.76 $0.38 $0.55 $11.25 $8.26 $2.57 15

ASSESSMENT BALLOTING PROCESS Per Board direction, ballots are mailed to all affected property owners along with a notice that details: A description of services to be funded by the assessment and the benefits provided to property owners. The proposed charge for each property owner, the total cost of the assessment, and the maximum assessment rates. An explanation of the process for submitting objections and ballots. Objections based on noncompliance with Proposition 218 may be submitted up to 45 days after ballots are mailed. CGA will review and provide written responses to objections. Changes to the assessment may be considered. Ballots may be submitted up until the public input portion of the public hearing has closed (must be at least 45 days after ballots are mailed CGA is considering a 55-day balloting period). If a majority of returned ballots are submitted against the assessment, then it cannot be imposed. 16

TENTATIVE ASSESSMENT TIMELINE Date Item Notes 5/26 Engineer s Report, Notice and Ballot to District and District Counsel for Review BOARD MEETING: Assessment Workshop 6/2 6/6 Balloting Materials sent to mail house for preliminary preparation. BOARD MEETING: Engineer s Report Considered and Approved Notices and Ballots Mailed 6/10 6/13 6/25 Community Meetings Held Potential for two meetings on the same day. Provides 46 days to submit objections. Provides 55 days to submit protests. 7/29 Deadline to Submit Exhaustion of Remedies Objections BOARD MEETING: Public Hearing / Tabulation of Ballots Direct Charge Rolls Finalized and Submitted to Auditor s Offices. 8/7 8/8 17

QUESTIONS / DISCUSSION ASSESSMENT WORKSHOP JUNE 3, 2025 18