### UNITED STATES ENVIRONMENTAL PROTECTION AGENCY REGION IX 75 Hawthorne Street San Francisco, CA 94105 Memorandum November 3, 

### 2015 From: Diane Fleck 

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# ~ Daniel Oros



## -~ 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 11 

### How 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 11 

### Salt and Estuarine Waters of the Bay Delta . "

2E 1300 1 2 00 1100 1000 

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### cJ5 7 00 :J 600 500 400 300 2 00 100

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 1201 5 00: 00 , 1 323. 0 

### r in of period : 07t12f201 2 00: 00 , 0 .0



# . .... .0

0 1 1tl1 / 11 00 01 Kl 1/ 12 00 011tl1 / 1 3 00 0 1 1tl 1/ 14 00 01 1tl 1/ 1 5 00 

# 1 - E L E CTR I CAL CO N D U CT IVTY M IC R O S - u Sfc m ( 10 0 

# I Generated on Wed Jul29 08 : 18 : 14 PDT 2015 VER data 

## I ShawVER Map 

## I VER Info Station I D : !vER Sensor No : '-! 1o

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_-'l Duration Code : 

## 0 M @ D 

## 0 H 

## 0 E End Date:j 07/2 9 /2015 08 : 17 

# I Plot Size: 

### ® Small 

## 0 Med i um 

## 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/


### 3To 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 E lectrical C ondu ctivity Samp li ng Station s I I 

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### El k Grove 1..: 1 

### Vacavi ll e on oma 

### Napa Fa irfi eld al t 1:1 1 l y J , 

### Lod i ll!O M or ad a 

### Concord Walnut Cree k Berke l ey 

## San Franc isco

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**~·.2" 15**  C3o oy le The symbol s d epict e lectrical co nductivity ( EC) samp lin g site location s in t he De lta. The Vernali s samplin g station is at th e lowe r right corner of the d e lta. This snapshot w as taken over a 3 da y duration 

### ( 10- 13 Augus t 

### 2015) . The blu e co lor signifies very lo w E C and sa lini ty, wh il e red co lor sig nifi es hi g h EC and salinity . Th e we bsite for live sa lini ty monitoring in t he De lta is http://www.baydeltalive.com/salinity .