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

2. 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

3. 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

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

5. 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

6. 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

7. 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

8. 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

9. 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

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

11. 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

12. 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

13. 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

14. 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)