CALIFORNIA ASSOCIATION OF RESOURCE CONSERVATION DISTRICTS
SHANNON SWEENEY, WATER RESOURCES MANAGER, CITY OF SANTA MARIA
ANNE COATES, CACHUMA RESOURCE CONSERVATION DISTRICT
THURSDAY,NOVEMBER 13, 2014
RETHINKING WATER:PROTECTING MUNICIPAL
WATER BY PASSIVELY TREATING AGRICULTURAL
RUNOFF
SANTA MARIA VALLEY GROUNDWATER BASIN
• BENEFICIAL USES INCLUDE:
• AGRICULTURAL SUPPLY
• MUNICIPAL SUPPLY
• GROUNDWATER BASIN CONNECTED TO SURFACE WATERS WITH BIOLOGICAL, RECREATIONAL USES.
• IMPACTED BY NITRATE, WHICH AFFECTS ALL OF THE BENEFICIAL USES.
CITY OF SANTA MARIA MUNICIPAL SUPPLY
• CITY OF SANTA MARIA HAS TWO SOURCES OF DOMESTIC WATER SUPPLY:
• STATE WATER: HIGH QUALITY, VARIABLE SUPPLY
• GROUNDWATER: VERY RELIABLE, VARIABLE QUALITY
• DOMESTIC SUPPLY NEEDS TO MEET STATE AND FEDERAL WATER QUALITY STANDARDS FOR NITRATE AND TOTAL DISSOLVED SOLIDS.
GROUNDWATER SUPPLY AND QUALITY
• CITY PRODUCTION WELLS HAVE VARIABLE QUALITY.
• TESTING SHOWS LOWER WELL PERFORATIONS
LOWER IN NO3 THAN
UPPER PERFORATIONS.
RWQCB AGRICULTURAL ORDER
• FARMERS SEEK LOW NITRATE IRRIGATION WATER TO LOWER NITRATE IN RUNOFF, OR AVOID RUNOFF COMPLETELY.
• PROBLEMS – IF EVERYONE DIGS DEEPER WELLS, THEN “LOWER” AQUIFER BECOMES IMPACTED ALSO. LEAVING WATER ONSITE LEADS TO SALT BUILDUP – BAD FOR FARMERS AND MUNICIPAL SUPPLY.
• REGIONAL BOARD’S NUTRIENT CONCERNS: DOWNSTREAM BIOSTIMULATORY EFFECTS (ALGAL BLOOMS) AND RECHARGE FOR MUNICIPAL SUPPLY
UC DAVIS REPORT FOR THE SWRCB SBX2 1 REPORT TO
THE LEGISLATURE• 2008 – SBX2 1 SIGNED INTO LAW – REQUIRES A STUDY TO BETTER UNDERSTAND NITRATE ISSUES.
• FINISHED PRODUCT: ADDRESSING NITRATE IN CALIFORNIA’S DRINKING WATER.
• KEY FINDING: “DIRECT REMEDIATION TO REMOVE NITRATE FROM LARGE GROUNDWATER BASINS IS EXTREMELY COSTLY AND NOT TECHNICALLY FEASIBLE. INSTEAD, “PUMP-AND-FERTILIZE” AND IMPROVED GROUNDWATER RECHARGE MANAGEMENT ARE LESS COSTLY LONG-TERM ALTERNATIVES.”
Main Issue: How can farmers “pump and fertilize” without letting nitrate-impacted runoff affect downstream uses, while still removing salts?
One thought: If nitrate is removed from the runoff, then salts can move to a proper sink (the ocean!) and municipal supply can be protected from both salts and nitrate.
DRAINAGE
• MOST OF SM VALLEY DRAINS THROUGH DISCRETE POINTS TO SM RIVER.
• THESE DISCRETE PATHS LEND THEMSELVES TO TREATMENT LOCATIONS.
NUTRIENT REMOVAL• BIOLOGICAL TREATMENT FOR NUTRIENT REMOVAL IS COMMON:
• WETLANDS – NEED LARGE FOOTPRINT
• TERTIARY WWTP’S – LABOR INTENSIVE, LARGE CAPITAL INVESTMENT
• BIOFILTERS – PASSIVE TREATMENT, LOW FOOTPRINT
• SOLUTION NEEDS TO MAXIMIZE NITRATE REMOVAL WITH SMALL FOOTPRINT AND LITTLE INVOLVEMENT.
BIOFILTER CONCEPTS• FACULTATIVE ANAEROBES CONVERT AMMONIA TO
NITRATE WHEN OXYGEN IS PRESENT.
• SAME BACTERIA SCAVENGE OXYGEN OFF NITRATE IN THE ABSENCE OF OXYGEN. NITRATE IS CONVERTED TO NITROGEN GAS.
• PROCESS NEEDS A SUBSTRATE, A CARBON SOURCE, AND SUFFICIENT TIME FOR BACTERIA TO GROW AND METABOLIZE.
• CONSTANT FLOW AND NUTRIENTS HELP, TOO.
WOODCHIP BIOFILTER• WOODCHIPS PROVIDE THE
CARBON AND THE SUBSTRATE
• CITY & COUNTY SUPPORT INSTALLATION AT JIM MAY PARK, FOR TREATING WATER FROM BRADLEY CHANNEL.
• BRADLEY CHANNEL DRAINS 5,700 ACRES OF AG LAND, 913 ACRES OF URBAN LAND.
• FEASIBILITY STUDY COMPLETED. EXPECTED TO REMOVE UP TO 50,000 LBS NITRATE PER YEAR.
El Centro, CA
CAN THIS HAPPEN?
• FILTER IS A PHYSICAL SOLUTION IN NEED OF FUNDING.
• RCD GRANT HAS FUNDING NOT OTHERWISE AVAILABLE TO A MUNICIPAL AGENCY.
• RWQCB SUPPORTS THIS EFFORT.