Phosphorus Offset
Agreement by and between
the City of Santa Rosa and
the Town of Windsor
City of Santa Rosa
Board of Public Utilities Contract Review
Subcommittee
December 5, 2022
Overview
• Brief history of nutrient offset requirements
• Agreement with Town of Windsor
2 Phosphorus Regulatory Requirements
• 2006 Permit: Nitrogen &
Phosphorus Zero Net Loading
• 2008 RWB Approves Nutrient
Offset Program (NOP)
• 2009-present: City implements
NOP Projects
• 2013 Permit: Zero Net Loading
for Phosphorus only
• 2018 RWB Adopts Water Quality
Trading Framework – Includes
Windsor Treatment Plant
Phosphorus Compliance
Strategy
1. Maximize reuse/minimize discharges
2. Decrease phosphorus in recycled water
3. Offset discharges via nutrient offset
projects
4. Buy and sell credits to reduce amount of
unused and expired credits
Santa Rosa has Episodic Discharges
0 10
20 30
40 50
60 0
500
1,000
1,500
2,000
2,500
3,000
3,500
4,000
4,500
Annual rainfall inches
Volume, million gallons/ year
Discharge year (Oct 1 through Sep 30)
Annual Discharge and Rainfall
Rainfall Discharge
Geysers Pipeline
Phosphorus Discharges
Period Total Phosphorus Discharged
(Pounds)
2013-2014 0
2014-2015 0
2015-2016 114
2016-2017 15,448
2017-2018 0
2018-2019 6,886
2019-2020 0
2020-2021 0
2021-2022 0
6 4 Nutrient Offset Projects Implemented
1) Beretta Dairy –
Manure & Pasture Management
2) Pepperwood Nature Preserve –
Road & Drainage Improvements
3) Ocean View Dairy –
Manure Removal & Land Application
4) Laguna 1 and 2 Restoration–
Sediment Removal and Restoration
Cost of Projects
Project Cost
Total Sum of
Phosphorus
Credits
Cost per
Credit
Beretta $508,250 7,600 $67
Pepperwood $512,850 10,964 $47
Ocean View $474,000 23,345 $20
Laguna $746,300 14,926 $50
Credit life
9 Project
Total
Credits Credit Life
Used or
Expired
Credits
Remaining
Credits
Beretta 3,337 3 Years 2,925 412
Pepperwood 4,027 In
Perpetuity 3,680 337
Ocean View 21,932 3 Years 21,932 0
Laguna 14,926 In
Perpetuity 46 14,880
Agreement
• Allows buying and selling of credits between City of
Santa Rosa and Town of Windsor
• Credits will be sold at the cost of development plus
a 20% handling fee
• City has credits that will expire if not used or sold • Windsor’s credit needs are more frequent, but
smaller amounts less than 1,000 credits per year
10 Recommendation
It is recommended by the Santa Rosa Water
Department that the Contract Review Subcommittee
recommend approval of the Phosphorus Offset
Agreement by and between the City of Santa Rosa
and the Town of Windsor.
11