Highlights of the New NPDES Permit Jim Keller Monica Oakley Mark Koekemoer August 3, 2016

About NPDES Permits NPDES = National Pollutant Discharge Elimination System Federal and State permit Issued by the Regional Water Quality Control Board (a state agency) Federal authority is delegated to the state by the U.S. Environmental Protection Agency NPDES Permit lasts for five years

Permit Dates Renewal Application Submitted September 30, 2015 Tentative Order (Public Review) April 26, 2016 Adopted July 13, 2016 (Uncontested Calendar) Effective September 1, 2016 Expires August 31, 2021

Permit Adoption Hearing – July 13, 2016 Regional Water Board members commended NSD: Perfect compliance during previous permit term Extensive recycled water program

Permit Adoption Hearing – July 13, 2016 …and expressed significant concern with the existing rate of collection system repair and replacement at 1.1% Tim Healy explained the recent rate increase going to 1.3% for the next three years and reaching 2% in five years Tim emphasized NSD’s commitment to integrity of collection system Board members were satisfied with this development

Regional Water Board is Also Looking at Sanitary Sewer Overflow (SSO) Data First draft of permit: Medians Length (miles) Age (years) Total SSO Rate (per 100 miles of sewer) 2012 2013 2014 2015 Napa Sanitation District (main and lower lateral lines) 418 57 26.6 27.3 30.4 19.8 Solano County median (>100 miles) 426 33.7 6.5 6.1 8.9 Sonoma County median 117.1 59.1 4.9 0.9 7.8 2.1 San Francisco Bay Region median of 45 large systems (> 100 miles) 230 50 5.0 4.5 5.2 3.5 median of all 132 systems 46 45 4.6 6.2 3.2

Average Age of Pipe (years) Main and Lower Lateral Lines Final permit: Medians No. Systems Length (miles) Average Age of Pipe (years) Total SSO Rate (per 100 miles of sewer) 2012 2013 2014 2015 Main Lines Only Napa Sanitation District 1 271 43 4.1 3.0 9.2 Solano County median (>100 miles) 3 270 34 3.8 2.4 4.2 Sonoma County median (>100 miles) 2 165 59 6.9 3.3 10.9 4.3 Marin County median (>100 miles) 4 173 48 12.1 8.1 10.3 8.8 Main and Lower Lateral Lines 418 26.6 27.3 30.4 19.9 426 6.5 6.1 8.9 177 9.8 3.9 12.4 San Francisco Bay Region median of large systems (>100 miles) 45 230 50 5.0 4.5 5.5 San Francisco Bay Region median of all systems 133 46 5.2 6.3 3.7

Notable Changes from Previous Permit Discharge “Prohibition” Period Reduced Old: May – Oct (6 months) New: July – Sep (3 months) New discharge period will result in more recycled water storage “Wet season” BOD and TSS Limits Extended These BOD and TSS limits extended to May, June, and October: Constituent “Wet Season” “Dry Season” BOD – average monthly 30 mg/L 10 mg/L BOD – average weekly 45 mg/L 20 mg/L TSS – average monthly TSS – average weekly

More Notable Changes New Reporting of Recycled Water Volumes Daily Monthly Purpose is to justify change in “prohibition” period. If a discharge less than 4 days occurs in July, August, or September, reduced sampling is allowed Mobilization not justified for short-term discharge Lots of sampling already at other times of year

Other Constituents with Effluent Limits 2011 Permit 2016 Permit Copper Nickel Cyanide Total Ammonia Dioxin -TEQ

Successes in Permit Negotiations Prevented change to ammonia limits Final permit allows greater operational flexibility and reduces risk of non-compliance Simplified recycled water reporting Only recycled water distribution will be reported Ammonia Limit (mg/L) 2011 Permit 2016 Draft Final Average Monthly Limit 21 12 Maximum Daily Limit 49 37

Chronic Toxicity Trigger (Tuc) More Successes Increased influent cyanide concentration action trigger Action trigger in draft permit was 8.9 mg/L, final permit has 12 mg/L. Retained existing chronic toxicity triggers Chronic Toxicity Trigger (Tuc) Draft Permit Final Permit 3-Sample Median 1 10 Single Sample Maximum 2 20

Monitoring Frequency Reductions Constituent(s) 2011 Permit 2016 Permit Estimated Cost Savings to District During Permit Term BOD & TSS Sampling Frequency 2 / week 1 / week $4,500 Turbidity 2 / month none $200 Dissolved Oxygen Sampling Frequency 1 / day $3,100 Priority Pollutants 2 / year 1 / year $20,260 Pretreatment Pesticides $3,060 Groundwater – several parameters $1,300

Successful NPDES Permit Adoption Was a Team Effort Tim Healy Andrew Damron Jim Keller Mark Koekemoer Jeff Tucker Elsa Seal Monica Oakley Dave Richardson (RMC) Jennie Pang (RMC)