Progress of Implementation of Nitrate TMDL for the San Lorenzo River, Santa Cruz County, California
- 1 Background
- 2 Summary
- 3 Action Taken Since TMDL Approval
- 4 References
- 5 Disclaimer
- Nitrate concentrations have increased in the San Lorenzo River watershed since the 1950's and are dangerously close to violating parts of the Central Coast Region Water Quality Control Plan, also known as the Basin Plan. The Basin Plan contains the following objective for taste and odor: “Waters shall not contain taste or odor-producing substances in concentrations that impart undesirable tastes or odors to fish flesh or other edible products of aquatic origin, that cause nuisance, or that adversely affect beneficial uses." 
- Since high nitrate levels can stimulate biological growth of algae, molds, and fungi, it threatens drinking water supplies by releasing organic compounds. These compounds are known to cause noxious tastes and odors,but more importantly, they produce potentially carcinogenic disinfection byproducts when the water is treated.
- The San Lorenzo River Total Maximum Daily Load for nitrate was the first TMDL written for a water body in the central coast region. The TMDL was first initiated in 2000, when the [Central Coast Regional Water Quality Control Board (CCRWQCB)] approved an amendment to the original Basin Plan. The amendment addressed the issue of inadequate nitrate concentration reporting limits, which was 5-7 times above background levels, by switching to the target concentration required by the TMDL for the San Lorenzo River. The CCRWQCB approved the nitrate TMDL for the San Lorenzo River in September of 2000, and it was finally approved by the EPA in 2003 .
- The 1995 Nitrate Management Plan determined that nearly 67% of the nitrate in the San Lorenzo River detected in the summer season came from areas close to the Santa Margarita Sandstone. Septic systems in these areas contribute between 10-15 times more nitrate to the river than other less permeable soils. Thus, reduction efforts are most effective in areas with sandy soils. 20% of contamination is directly caused by humans during the wet season. 
- The San Lorenzo River is still considered impaired and nitrate levels have not declined as rapidly as projected. Reductions in harmful nitrate levels in the San Lorenzo River can be achieved with better management of wastewater disposal methods (e.g. septic system upgrades), improved livestock management strategies, and various land-use practices which require less fertilizers. Continued monitoring of established sites is crucial to ongoing efforts that aim to identifying nitrogen hot spots and point sources.
Action Taken Since TMDL Approval
Much of the implementation plan for the San Lorenzo nitrate TMDL was adopted from the existing Nitrate Management Plan (NMP), which was developed for the Basin Plan in 1995 . Santa Cruz County was required to submit a Nitrate Management Plan Implementation Report to the CCRWQCB in 2005, and 2010 . However, the plan for 2010 is not available for public review, and the next submission is not required until 2020.
In 2008, the County of Santa Cruz submitted a DRAFT SAN LORENZO WASTEWATER MANAGEMENT PLAN PROGRAM STATUS REPORT 2002-2007 for the Wastewater Management Plan, which included a review of the Nitrate Management Plan's progress. Implementation of the NMP was expected to reduce nitrate levels by 15-20% from 1995-2005, followed by a reduction of 10% in the next 10 years. Observed nitrate trends show that reductions are occurring slower than desired, with an 11% decrease over the past 15 years. Ben Lomond and Boulder Creek sites has experienced significant reductions of up to 60%. The report suggested that "no significant adverse impacts resulting from nitrate loading at the current level have been identified".
Below is a list of planned actions and progress of implementation plan of nitrate TMDL in the San Lorenzo River. The following nitrate reduction measures have been directly taken from the 2008 program status report:.
Wastewater Disposal and Nitrogen Reduction Management
There are 13,000 parcels with a total of 13,900 septic systems in the county’s database. In the past, the status of the 13,900 systems were evaluated via site inspections for failures, assessment of groundwater levels, water quality monitoring and septic tank pumping records. Over 80 boreholes and 11,700 parcels were inspected by the time the DRAFT SAN LORENZO WASTEWATER MANAGEMENT PLAN PROGRAM STATUS REPORT 2002-2007] was produced. Since 2008, roughly 10 wells continue to be monitored on an annual basis and periodic site inspections are ongoing but infrequent.
- New Development
Most of the suitable parcels have already been developed. According to the 2002-2007 Management Plan, 30% of new developments must use alternative systems, and any new developments must meet the existing requirement implemented in 1983 of a one acre minimum parcel size if the resulting septic system(s) are in the San Lorenzo Watershed. Additionally, in 2002, the county approved an exception which allows 20 commercial parcels to be developed in the village areas of the San Lorenzo Valley. However, the most common reason for bringing septic systems up to current standards is due to remodeling projects on existing homes in the watershed.
- Land Use Regulations for Nitrogen Reduction
Current density restrictions require that owners maintain a 10 acre per parcel limit for new land divisions. Current regulations for erosion control, land clearing practices, and riparian corridor protection are required to be maintained and ongoing. No new land use projects within the watershed can be approved if the project area will increase nitrate discharges to groundwater or surface water by more than 15 pounds per acre, per year.
Wastewater Disposal Treatment
1. Planned: Implement improved wastewater disposal management through the San Lorenzo Wastewater Management Plan
2. Progress: Ongoing
- Boulder Creek Country Club Treatment Plant
1. Planned: Complete ongoing efforts to improve treatment procedures at Boulder Creek Country Club Treatment Plant to reduce nitrate discharge by using wastewater reclamation on the golf course. (The treatment process was refined and fully operational by May 1998. The improvements provide for treatment for nitrogen removal, with the possibility of wastewater reclamation on the golf course much of the year. Effluent has generally not been used for reclamation on the golf course, due to strict regulations. However, the effluent that is delivered to leach fields for disposal has significantly lower nitrogen levels. Nitrogen levels in Boulder Creek are 60% less than the levels from the mid 1990’s.
2. Progress: Ongoing
Shallow Leach Fields
1. Planned: Maintain the new requirement for shallow leach fields for new and repaired septic systems (less than 4 feet in sandy areas, and 4-6.5 feet in other areas).
2. Progress: Ongoing
1. Planned: Implement enhanced technology for at least 50% nitrogen removal for septic system in sandy soils. Require septic systems serving new or expanded uses in sandy soils to install enhanced treatment measures which will reduce nitrogen discharge by at least 50%. (Implemented August 1995; existing systems to be upgraded at the time of major remodels (originally projected rate of 1.2% (20 systems) per year is actually 0.3%, or 5.25 systems per year over the past 12 years.
- Encourage the use of nitrogen removal methods for any onsite disposal system which will use a nonstandard system. (Since 1995, 245 alternative systems with capability for nitrogen removal have been approved for use in the San Lorenzo Watershed: 15 sand filters, 63 Advantex Systems, and 167 FAST systems. The 61 systems installed in sandy soils will reduce the summer nitrate load from sandy areas by 6%.)
- Continue to evaluate new onsite wastewater disposal technology for nitrogen reduction to identify more cost-effective measures. Require higher levels of nitrogen removal if measures become available that are more cost-effective than sand filters. (Some new technology is becoming available, but the cost continues to be high.)
- Apply for State revolving funds and other funds to develop a funding source to assist property owners in repairing their systems to provide enhanced treatment. (Revised program is now being implemented, beginning June 2005. This could fund 100 upgrades over the next five years, although only 7 loans have been applied for in the past 2 years.)
- When more cost-effective technology and/or funding assistance becomes available, require all onsite system repairs in sandy areas to utilize enhanced treatment for nitrogen removal. (Implementation deferred, pending more inexpensive technology and documented need for further nitrogen reduction.)
- Require all large onsite disposal systems which serve more than 5 residential units or dispose more than an average of 2000 gallons per day to utilize enhanced treatment to reduce nitrate discharge by at least 50%. Installation of such measures for existing systems shall be required at the time of system repair or upgrade. (Estimated 1-2 upgrades involving approximately 5000 gallons per day per year, but only about 8 upgrades have occurred in the past 12 years.)
- Require all new or revised waste discharge permits and all new development projects in the San Lorenzo Watershed to include nitrogen control measures consistent with this Nitrate Management Plan. (County staff has worked with staff at the Regional Board to include nitrogen reduction requirements in new or amended waste discharge permits. This was included in the permits for expansion of the Mount Hermon Association system, the Boulder Creek Country Club system, the San Lorenzo Valley High School system, Brookdale Lodge, Pasatiempo Inn, and Bear Creek Estates.)
2. Progress: Ongoing
1. Planned: Require all large onsite disposal systems which serve more than 5 residential units or dispose more than an average of 2000 gallons per day to utilize enhanced treatment to reduce nitrate discharge by at least 50%. Installation of such measures for existing systems shall be required at the time of system repair or upgrade. (Estimated 1-2 upgrades involving approximately 5000 gallons per day per year, but only about 8 upgrades have occurred in the past 12 years.)
2. Progress: Ongoing
Nitrogen Control Measures
2. Progress: Ongoing.
- If 2010 summer nitrate levels in the San Lorenzo River have not declined by at least 15%, reevaluation of implementation practices, and recommendations for more stringent control measures may be required. (No available updates on the status of this requirement available).
Livestock Management for Nitrogen Reduction
1. Planned: Continue to work with stable owners and develop a new ordinance requiring practices to reduce nitrate discharge: cover manure piles, maintain manure piles and paddock areas at least 50-100 ft from streams or drainage areas, direct drainage away from paddock areas, and provide other measures as necessary to reduce discharge of nitrate, sediment, and contaminants.
- After meetings with stable and horse owners, it was decided to pursue an approach of education, technical assistance, and voluntary compliance. A grant funded effort by the Resource Conservation District and Ecology Action got underway in 2001 and continues with new grant funds. This program has provided for 9 pilot projects implemented in the watershed, 13 area workshops, 30 site visits for technical assistance in the watershed, and significant outreach to the Horsemen’s Association and horse owners. All new or modified horse operations now prepare and implement manure management plans to reduce the runoff or percolation of nitrate.
Ongoing Monitoring of Nitrogen Sources
- Scotts Valley Nitrate Plume
1. Planned: Monitor the Scotts Valley nitrate plume, and identify potential ongoing sources of nitrate. Work with the City of Scotts Valley and property owners for reduction of nitrate discharge from Scotts Valley, if feasible.
2. Progress: Ongoing monitoring, nitrate concentrations seems to be diminishing by 30%.
- Nitrate Level Monitoring
1. Planned: Continue to monitor nitrate levels in surface and groundwater. Reevaluate implementation of more stringent control measures if summer nitrate levels in the River have not declined by at least 15% by 2010.
2. Progress: Ongoing monitoring, reevaluation in 2010
- CCRWQCB. 2000. Resolution No. 00-003
- DRAFT SAN LORENZO WASTEWATER MANAGEMENT PLAN PROGRAM STATUS REPORT 2002-2007
- [Santa Cruz County. 2008. San Lorenzo wastewater management plan: draft program status report 2002-2007. 1-28
- CCRWQCB. 2000. Staff report for regular meeting for September 15, 2000: San Lorenzo River nitrate Total Maximum Daily Load. State of California: 1-32.
- CCRWQCB. 2000. Nitrate Total Maximum Daily Load for San Lorenzo River, Carbonera Creek, Shingle Mill Creek, and Lompico Creek. State of California: 1-44. http://www.waterboards.ca.gov/centralcoast/water_issues/programs/tmdl/docs/san_lorenzo/nitrate/slr_nitrate_tmdl_proj_rpt.pdf
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