ImpactReport(EIR)inaccordancewiththeCalifornia uatearangeofenvironmentaltopics,including: ands)
Connecting winter water to storage for a more resilient water supply
standexistingsiteconditions,includingareasthatmaycontain
softheprojectandevaluatewaystoavoid,minimizeor derationofconstruction-relatedimpactsaswellas
Marin Water is proposing to construct the Atmospheric River Capture (ARC) Project, a water supply project designed to improve Marin Water’s resilience during dry periods. It would provide the infrastructure needed to deliver high flows from the Russian River during and following key winter storms to Nicasio Reservoir for storage, where the water can be used later during dry periods.
HOW IT WORKS
s,increasingreservoircapacity,etc.? evaluatedawiderangeofwatersupplyandstorageoptionsas on,thecreationofnewreservoirs,desalination,recycled ntefforts,andincreaseduseofsupplementalRussianRiver dentifiedasthemostpracticalandcost-effectivenear-term
Even in dryyears with below-average rainfall, intense atmospheric river storms can temporarilyswell the Russian Riverwith high winter flows
TheARC Project would operate during these dryyear storm windows to d otherwise flow to the ocean
createaconnectingpipelinetoaccessandstorewaterduring nowunderway,arangeofalternativeswillcontinuetobe valisconsidered.
nter water captur storm windows Russian River watersh r than Marin Water’s M rshed. As a result, sto rate sustained runoff flows – even in dry ye ting opportunities to c
NorthBayandbroaderregionalwatersystemsareint duringdroughts,emergencies,andotherperiodsofu
TheproposedARCProjectwouldstrengthenregiona waterduringspecificstormconditionsforlaterused locallyduringwetperiods,theprojectcanhelpimpro flexibleuseofsharedregionalwatersuppliesduringf
MarinWaterandneighboringagencieshave regionalwaterresilienceduringchangingcon
vels through existing rth Marin Aqueduct captured winter water would travel ugh existing infrastructure already by Marin Water Today, this water s directly to the distribution system nto local reservoirs.
Conveyed to storage via new pipeline and pump system
The ARC Project builds a new connection between the Aqueduct and Nicasio Reservoir, providing the missing link that allows for captured winter water to be stored for later use.
red in Nicasio Reservoir for r use
ed water would supplement Marin er’s supply during extended dry ods. Diversions from the Russian r would be closely coordinated with her forecasts and reservoir levels would only occur when storage space ailable and local conditions in the ian River Watershed allow.
THE FULL PROJECT AT A GLANCE
New infrastructure would connect the North Marin Aqueduct to Nicasio Reservoir, allowing captured winter flows to be stored for use during dry periods. What Would Be Built
*This connection to Stafford Lake creates a potential future opportunity for North Marin Water District to more efficiently capture and store available winter water during dry periods.
The full Project would include a 13.2-mile pipeline, two pumping stations, a dechlorination facility and points of delivery at both Stafford Lake and Nicasio Reservoir.
CURRENTESTIMATEDPROJECTCOSTANDFUNDING
$195million,withapotentialrangeof$137millionto$293million
MarinWaterisfundingthedesignoftheARCProjectthroughitscapitalbudgetprogramand planstofinanceconstructionthroughbondfunding.Inparallel,theProjectteamisalsoactively investigatingallavailablestateandfederalfundingopportunitiesthatmayhelpoffsetsomeof theProjectcosts.
PROJECTTIMELINE
KEY BENEFITS What Would Be Built
Estimated as of May 2026 and may change based on environmental review, property acquisitions and permitting.
2025-2026 Preliminary Design
2025-2027 Environmental Review
(Environmental Impact Report prepared in compliance with the California Enviornmental Quality Act)
Improve Drought Resilience
Captures excess winter water resulting from storm events, and stores it in local reservoirs for use during dry periods.
1
Scoping: Initiate Environmental Review with Notice of Preparation (NOP) & Public Outreach Comments on EIR scope collected March 13 –
Publish Draft EIR
EDPROJECTCOSTANDFUNDING potentialrangeof$137millionto$293million ngthedesignoftheARCProjectthroughitscapitalbudgetprogramand tructionthroughbondfunding.Inparallel,theProjectteamisalsoactively ablestateandfederalfundingopportunitiesthatmayhelpoffsetsomeof
P bli C t P i d f D ft EIR (45 d )
4
Address Public Comments on Draft and Publish Final EIR
Anticipated late 2026 / early 2027
2026-2027 Final Design & Permitting
2027-2030 Construction
Align with Community Priorities
Marin Water is coordinating with local agencies as the project develops to identify opportunities, where feasible, to align the project with local priorities and provide added community value.
Amount of water flowing to Pacific Ocean from Russian River
HOW THE PROJECT WOULD HAVE WORKED IN PREVIOUS DROUGHTS
DFUNDING
millionto$293million
Drought of Record – 1976-1977
Projectthroughitscapitalbudgetprogramand unding.Inparallel,theProjectteamisalsoactively ndingopportunitiesthatmayhelpoffsetsomeof
(Winter months when ARC Project would operate)
139 days of available surplus water (~27,000 acre-feet)
Whatenvironmentalstudiesarebeingconducted?
MarinWateriscurrentlypreparingadraftEnvironmentalImpactReport(EIR)inaccordancewiththeCalifornia EnvironmentalQualityAct(CEQA) ThedraftEIRwillevaluatearangeofenvironmentaltopics,including:
Trafficandtransportation
Noise
Biologicalresources(suchaswetlandsandoakwoodlands)
Culturalandarchaeologicalresources
Airqualityandotherenvironmentalfactors
Environmentalsurveysarealsounderwaytobetterunderstandexistingsiteconditions,includingareasthatmaycontain sensitivehabitatsorresources
Howwillenvironmentalimpactsbeaddressed?
ThedraftEIRwillidentifypotentialenvironmentalimpactsoftheprojectandevaluatewaystoavoid,minimizeor mitigatethoseimpactswherefeasible.Thisincludesconsiderationofconstruction-relatedimpactsaswellas operationaleffects.
WhyARCoverotheroptionslikemorestoragetanks,increasingreservoircapacity,etc.?
Overthelastfiveyears,MarinWaterhasdevelopedandevaluatedawiderangeofwatersupplyandstorageoptionsas partofitslong-termplanning,includingreservoirexpansion,thecreationofnewreservoirs,desalination,recycled water,directpotablereuse,bolstereddemandmanagementefforts,andincreaseduseofsupplementalRussianRiver supplies.Basedonthatevaluation,theARCProjectwasidentifiedasthemostpracticalandcost-effectivenear-term optionforimprovinglong-termwatersupplyreliability.
TheARCProjectwouldleverageexistinginfrastructuretocreateaconnectingpipelinetoaccessandstorewaterduring keystormeventsforuseduringdryperiods
AspartoftheEnvironmentalImpactReport(EIR)processnowunderway,arangeofalternativeswillcontinuetobe formallyevaluatedandanalyzedbeforeanyprojectapprovalisconsidered.
Nicasio Reservoir
diesarebeingconducted?
eparingadraftEnvironmentalImpactReport(EIR)inaccordancewiththeCalifornia (CEQA) ThedraftEIRwillevaluatearangeofenvironmentaltopics,including: on
Why Regional Water Supply Collaboration Matters
uchaswetlandsandoakwoodlands) gicalresources
nvironmentalfactors
alsounderwaytobetterunderstandexistingsiteconditions,includingareasthatmaycontain ces impactsbeaddressed?
potentialenvironmentalimpactsoftheprojectandevaluatewaystoavoid,minimizeor erefeasible.Thisincludesconsiderationofconstruction-relatedimpactsaswellas
tionslikemorestoragetanks,increasingreservoircapacity,etc.? arinWaterhasdevelopedandevaluatedawiderangeofwatersupplyandstorageoptionsas ng,includingreservoirexpansion,thecreationofnewreservoirs,desalination,recycled ,bolstereddemandmanagementefforts,andincreaseduseofsupplementalRussianRiver aluation,theARCProjectwasidentifiedasthemostpracticalandcost-effectivenear-term ermwatersupplyreliability.
Drought Response (2021) – Residential Preparedness
erageexistinginfrastructuretocreateaconnectingpipelinetoaccessandstorewaterduring uringdryperiods
talImpactReport(EIR)processnowunderway,arangeofalternativeswillcontinuetobe lyzedbeforeanyprojectapprovalisconsidered.
Drought Response (2021) – Agricultural Use
NorthBayandbroaderre duringdroughts,emerge
TheproposedARCProje waterduringspecificsto locallyduringwetperiod flexibleuseofsharedreg
MarinWaterandneig regionalwaterresilie
During the most recent drought, Marin Water and North Marin Water District worked with the County of Marin and other partners to prepare for providing emergency potable water supplies for rural residents relying on wells that were at risk of running dry These measures were ultimately not needed due to changing conditions
Both water districts also worked with the County of Marin to support water needs in areas outside both districts’ service areas, including allowing West Marin ranchers to purchase and truck untreated reservoir water for agricultural use over several months during the drought.
Novato Landslide (2023)
A landslide in Novato raised concerns about access to local water supply Marin Water coordinated with North Marin Water District and was prepared to support emergency interconnections if needed to help maintain service for North Marin Water District customers.
Future Opportunity – Stafford Lake Winter Water Storage
Future Opportunity – Supporting North Bay Water Resilience
The ARC Project would include infrastructure connecting to Stafford Lake, creating a potential future opportunity for North Marin Water District to more efficiently capture and store available winter water during key storm events. By leveraging infrastructure used by both agencies, this could support additional drought resilience and more efficient use of available regional winter water sources.
By allowing Marin Water to store water captured during key winter storm events for later use, the ARC Project could help reduce reliance on shared regional water supplies during droughts. This added flexibility may help support broader North Bay water resilience during periods when water supplies are limited.
