UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

REGION IX 

75 Hawthorne Street 

San Francisco, CA 94105 

Memorandum 

November 3, 2015 

From: Diane 

Daniel 

Fleck 

Oros 

f fA1i { ~ 

-~ Water Quality Assessment Section 

Water Division, US EPA Region 9 

To: Administrative Record for Selenium Criteria for the San Francisco Bay and Delta; 

Administrative Record for Selenium Criteria for the Rest of California 

Re: Salinity from Ocean Influence on the San Joaquin River 

The Consent Decree in Our Children's Earth Foundation and Ecological Rights Foundation v. U.S. 

EPA et al., ("Consent Decree") and the National Taxies Rule (57 FR 60848, December 2, 1992) 40 CFR 

131.36(b)(10)(ii), identify three specific areas of California: · 

(1) Waters of San Francisco Bay upstream to and including Suisun Bay and the Sacramento-San Joaquin 

Delta; 

(2) Waters of the San Joaquin River from the mouth of the Merced River to Vernalis; and 

(3) Waters of Salt Slough, Mud Slough (north) and the San Joaquin River, Sack Dam to the mouth of the 

Merced River. 

The Consent Decree defines these three areas as the "Bay Delta." The Consent Decree also 

contemplates the possible proposal of Selenium Criteria for "Salt and Estuarine Waters of the Bay 

Delta." The purpose of this memo is to evaluate whether the areas in (2) and (3) contain "Salt and 

Estuarine Waters of the Bay Delta." 

As defined in the Consent Decree, the set of "Fresh Waters" is disjoint with the union of "Salt 

Waters" and "Estuarine Waters." Further, Fresh Waters are defined as "those with 1 ppt or less of 

salinity 95% or more of the time." Thus, waters of the Bay Delta with 1 ppt or less of salinity 95% or 

more of the time are Fresh Waters and are not Salt and Estuarine Waters of the Bay Delta, as these 

terms are used in the Consent Decree. Salinity in the Bay Delta system is from ocean influence. 

The areas in (2) and (3) along the San Joaquin River (and Salt Slough and Mud Slough) are above 

the confluence of the River with the Delta; the most downstream point along the ~iver is Vernalis (i.e., 

the confluences of the Merced River, Salt Slough, and Mud Slough with the San Joaquin River, and Sack 

Dam along the San Joaquin River, are all upstream of Vernalis). 

Data indicate that the areas described in (2) and (3) have salinities from ocean influence of less 

than 1 ppt, 95% or more of the time. Salinity from ocean influence is predominantly caused by sodium 

1 
and chloride. The San Joaquin River at Vernalis is the most downstream point along the River of the 

areas described in (2) and (3). Salinity from ocean influence (measured as chloride concentration [CI-]) is 

not usually measured along the River at this location; instead, electrical conductivity (EC) is measured. 

EC is a measure of the ability of water to pass an electrical current. Conductivity in water is affected by 

the presence of inorganic dissolved solids including chloride, nitrate, sulfate, and phosphate anions (ions 

that carry a negative charge) or sodium, magnesium, calcium, iron, and aluminum cations (ions that 

carry a positive charge). EC measurements include chloride (CI-) which is found in both freshwater and 

seawater. 

The EC at Vernalis over the last five years (from June, 2010 through July 2015) is illustrated in 

the graph below. EC is measured in microsiemens per centimeter (11S/cm). The mean daily EC for the 

sampling station at Vernalis along the San Joaquin River peaked at 1323 11S/cm on February 3, 2015, 

which is equivalent to 0.66 ppt salinity (see Figure A entitled 11How to Convert Electrical Conductivity to 

Salinity"). This shows that the salinity due to ocean influences at Vernalis is well below 1 ppt; upstream 

stations will have even less ocean influence (i.e., less salinity from ocean influence). 

In summary, these data indicate that: 

• Areas (2) and (3) have salinity from ocean influence less than 1 ppt 95% or more of the time 

• Areas (2) and (3) are Fresh Waters; and 

• Neither Area (2) nor Area (3) includes 11Salt and Estuarine Waters of the Bay Delta." 

2 
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0 -

VERNALIS STATION ELECTRICAL CONDUCTIVITY 

I I • VERNALIS (USBR) ( VER ) 

Date from 0612912010 00:00 throu h 0712912015 08:17 D ration~ 1856 days 

a of perle : (0210 12015 00:00, 1323.0 r in of period: 07t12f201 2 00:00, 0.0 

. .... 

.0 

0 11tl1/11 00 01Kl 1/ 12 00 011tl1 /13 00 0 11tl1/ 14 00 011tl1/15 00 

1- ELECTRICAL CONDUCTIVTY MICRO S - uSfc m (1 00 I 

Generated on Wed Jul29 08:18:14 PDT 2015 VER data I ShawVER Map I VER Info 

Station ID: !vER Sensor No: '-!1o_o_-'l Duration Code: 0 M @ D 0 H 0 E 

End Date:j07/29/2015 08:17 I Plot Size: ® Small 0 Medium 0 Huge 

To Recreate this chart of EC at Vernalis: 

Step 1: Go to Department of Water Resources California Data Exchange Center website: 

http://cdec.water.ca.gov/ 

Go to QUERY TOOLS select and drop down to HISTORICAL DATA {HOURLY,EVENT,DAILY,MONTHLY) and 

select 

Step 2: This takes you to: http:Ucdec.water.ca .gov/cgi-progs/selectQuerv 

To get excel data (optional): Station ID is VER; Start date is 07/11/2010; End date is now; Duration is 

Daily; then select GET DATA 

To generate a data plot: At the bottom of the page select ROUGH PLOT 

Step 3: This takes you to: http://cdec.water.ca .gov/histPiot/ 

3 
To generate the plot: Station ID is VER; Duration Code is Daily; Start date is 07 /11/2010; End date is 

now; Plot size is small; then select ATIEMPT TO PLOT 

Step 4: This takes you to: 

http:// cdec. water.ca .gov /histPiot/Data Plotter.jsp ?staid=ver&sensor no=&d u ration=D&sta rt=08%2 F01% 

2F2010+09%3A52&end=now&geom=Small 

Select the option ELECTRICAL CONDUCTIVITY MICROS 

The data plot will then pop up. You can save the webpage as is or use your snipping tool to grab only 

the plot and table, which can be saved as a JPEG. If you save it as a JPEG then open it using PAINT, press 

select all, copy, and then paste it into a word document. Save it as a word document. 

Figure A How to Convert Electrical Conductivity to Salinity 

How To Convert Electric Conductivity (uS/em) to Salinity (mg/L or ppt) at Water Temperature (25"C): 

One way to convert EC to salinity is to use a common Salinity to EC or EC to Salinity conversion 

calculator found on the web at: 

http://www.hamzasreef.com/Contents/Calculators/SalinityConversion.php 

0 

Using the calculator: 1323 ~S/cm Electrical Conductivity= 0.66 ppt (or 0.66 mg/L) salinity at 25"C; 

(1 ppt [or 1 mg/L] of salinity= 1968 ~S/cm EC at 25"C). 

4 
Map of the Sacramento-San Joaquin Delta Showing the Electrical Conductivity Sampli ng Stations 

I I 

Sacr menta 

Davis 

Winter IL 

St 1elena 1 '" .... 

1 on 

Your tvillc Elk Grove 

1..: 1 Vacavi lle 

onoma Napa 

Fairfield al t 

1:1 1 l y 

J, Lodi 

ll!O 

Mor ada 

Concord 

Walnut Creek 

Berkeley 

San Francisco 

D:: l r Ctty Pleasanton 

1 data ~·.2" 15 C3ooyle 

The symbols depict electrical conductivity (EC) sampling site locations in t he Delta. The Vernalis 

sampling station is at the lower right corner of the delta. This snapshot was taken over a 3 day duration 

(10-13 August 2015). The blue co lor signifies very low EC and sa linity, wh ile red co lor signifies high EC 

and salinity. The website for live sa linity monitoring in t he Delta is http://www.baydeltalive.com/salinity.