### Staff Report of the



### C ALIFORNIA 

### E NVIRONMENTAL 

### P ROTECTION 

### A GENCY 

# R EGIONAL 

# W ATER 

# Q UALITY 

# C ONTROL 

# B OARD 

# C ENTRAL 

# V ALLEY 

# R EGION



# Selenium TMDL for Grasslands Marshes S T A T

E O F C A L I F O

R

N I A

R E G

I O N A L W

A T

E

R Q U A L I T Y C O

N T R O L B O A R D ★ ★

CENTRAL

V ALLEY REGION



# April 2000

# Selenium TMDL for Grasslands Marshes

Table of Contents List of Figures

................................................................................................................ ................ 2 List of Tables

................................................................................................................. ................ 2 List of Attachm e nts

............................................................................................................ ............ 2 Sum m a ry of TMDL Action

......................................................................................................... .. 3 Problem Statem ent

.............................................................................................................. ........... 3 Num e ric Target

................................................................................................................. ............. 7 Source Analysis

................................................................................................................ ............. 7 Im plem enta tion Plan

............................................................................................................ .......... 8 Allocations

.................................................................................................................... ................. 8 Perform a nce Measures and Feedback

............................................................................................ 8 Margin of Safety

............................................................................................................... ........... 12 Public Par ticipation

........................................................................................................... ........... 13 References

..................................................................................................................... ............... 13

List of Figures Figure 1. Location Map

......................................................................................................... ........ 4 Figure 2. W e tland W a ter Supply Schem a tic Before Grassland Bypass Project

............................ 5 Figure 3. W e tland W a ter Supply Schem a tic After Grassland Bypass Project

.............................. 6 Figure 4. Mean Monthly Selenium in Santa Fe Canal

.................................................................. 9 Figure 5. Mean Monthly Selenium in San Luis Canal

.................................................................. 9 Figure 6. Mean Monthly Selenium in Cam p 13 Canal

................................................................ 10 Figure 7. Mean Monthly Selenium in Agatha Canal

................................................................... 10

List of Tables Table 1. Annual Median Sele nium Concentrations

..................................................................... 11

List of Attachments

1. Grassland W a tershed W e tland Channels for W h ich Beneficial Uses Have Been Identified 2. Regional W a ter Quality Control Board, Central Valley Region, 1996 Basin Plan Am endm ents for the Control of Agricultural Subsurface Drainage Discharges, Resolution 96-147, Adm i nistrative Record Index 3. Regional W a ter Quality Control Board, Central Valley Region, 1996 Basin Plan Am endm ents for the Control of Agricultural Subsurface Drainage Discharges, Letters Received 4. Regional W a ter Quality Control Board, Central Valley Region, 1996 Basin Plan Am endm ents for the Control of Agricultural Subsurface Drainage Discharges, Response
t o C o mme n t s

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### Summary of TMDL Action Following are the waste load allocations and load allocations for the Grassland Marshes selenium TMDL:

TMDL (Loading Capacity) 2 ppb Selenium as a m onthly m ean Load Allocation Subsurface Drainage from Drainage Problem Area Background 2 ppb Selenium as a m onthly m ean 2 ppb Selenium as a m onthly m ean Waste Load Allocation (no NPDES sources) 0 lbs Selenium

Problem Statement The Grassland Marshes are listed in accordance with Section 303(d) of the Clean W a ter Act for exceeding selenium water quality objectives. Areal extent of the im pairm e nt was listed as 8,224 acres in 1988 as part of the water quality assessm ent and 303(d) listing process. The original basis for determ ining the extent of im pairm e nt is not available. As part of its 1996 Basin Plan Am endm ent, the Regional Board re-evaluated the m iles of wetland channels and the extent of wetland acreage im paired or threatened by selenium contam ination. The Regional Board determ ined that approxim a tely 75 m iles of wetland supply channels and 61,810 acres of wetland

m a rshes were im paired or threatened by elevated selenium concentrations in agricultural subsurface drainage water (California Regional W a ter Quality Control Board, Central Valley Region, 1998b, Appendix 40). The Regional Board has not updated its 305(b) report or 303(d) list to reflect the m o re recent evaluation. The TMDL described below is based on the m o re recent inform ation available regarding the extent of im pairm e nt.

Soils in the Grassland W a tershed (Figure 1) are derived from rocks of m a rine origin in the Coast Range that are high in selenium and salts. Major land uses in the watershed include agriculture and wetlands. W a ter supplied to the 61,810 acres of wetland m a rshes through supply channels that, prior to com p letion of the Grassland Bypass Project in Septem ber 1996, also conveyed agricultural drainage water (Calif ornia Regional W a ter Quality Control Board, Central Valley Region, 1996). Prior to com p letion of the Grassland Bypass Project, these supply channels alternately conveyed fresh water supplies and agricultural drainage water from 97,000 acres of tile drained farm land. Subsurface tile drainage water from these 97,000 acres is the prim ary source of selenium in the Grassland W a tershed. The result of this com b ined use was that the wetland water supply channels and the wetlands, periodically had elevated selenium concentrations. There are no NPDES perm itted sources that drain to the wetland channels that convey water to the Grassland m a rshes.

Dry conditions m a ke irrigation necessary for nearly all crops grown com m e rcially in the watershed. Irrigation of soils derived from m a rine sedim e nts leaches selenium into the shallow groundwater. Subsurface drainage is produced wh en farm ers drain the salty groundwater from the root zone to protect their crops, and a por tion of the Grassland W a tershed that generates subsurface drainage has been designated as the Dr ainage Project Area (DPA). The discharge of subsurface drainage from that area resulted in elevated selenium concentrations in the wetland supply channels and other water bodies within the watershed and downstream . Selenium is a

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### highly bioaccum u lative trace elem ent which, under certain conditions, can be m obilized through the food chain and cause both acute and chronic toxicity to fish and wildlife. Deform ities and deaths of waterfowl have been linked to toxic concentrations of selenium . There was concern that elevated selenium concentrations in subsurface drainage would cause problem s for the aquatic birds and wildlife that use the Grassland m a rshes. The Grassland m a rshes were placed on the Section 303(d) list in 1988 because water in the wetland supply channels routinely exceeded 2 μg/L. At the tim e of the 1988 listing, 2 μg/L was the United States Fish and W ildlife Serevice recom m e nded selenium criteria to protect waterfowl and other wildlife uses.

The Grassland W a tershed has undergone dram atic changes in hydrology and water quality due to agricultural developm ent over the years. Prior to Septem ber 1996, subsurface drainage from the DPA flowed through the Grassland wetlands on its way to the San Joaquin River (figure 2). Starting in Septem ber 1996, this subsurface drai nage was collected and conveyed in a single channel, the Grassland Bypass, to the northern reach of the San Luis Drain. The San Luis Drain discharges into Mud Slough (north) nine m iles upstream of its confluence with the San Joaquin River. The effect of this Grassland Bypass Proj ect was rem oval of m o st of the selenium load from wetland supply channels and therefore the wetlands them selves (Figure 3).

                                                                   
                                                               Sa l t Sl o u g h M u d S l ough

M e n dot a Pool S J R ne ar V e rnalis S t an i s laus Ri v e r

Tuolum ne Ri v e r

M e r c ed Ri v e r

Gras s l a nds W a t e rs h e d (3 70, 000 ac re s )

D r ain a ge P r oj ec t A r e a ( 97, 00 0 a c r e s ) No rt h Gr as slan d W a t e r Dis t ric t

S outh Gras s l a nd W a t e r D i s t r i c t



### Figure 1. Location Map

4S ant a F e Canal



### Dra i na ge P r oj e c t A r e a A gat h a C a n a l Cam p 1 3 Canal 

### • Nor t h Grassl a n d Wa t e r D i st rict

Sout h Grassl a n d Wa t e r D i st rict • S an L u i s Ca nal Sa l t S l ou gh 

### San J o a qui n R i v e r

M u d Sl ou gh (n o r th )

S an L u i s Dr ai n



### • •

CCI D M a i n Canal 

### •

Figure 2. Wetland Water Supply Schematic Before Grassland Bypass Project

5S ant a F e Ca nal



### D r ain a g e Pr o j ect A r ea A gat ha C a n a l Ca m p 1 3 Ca nal 

### • Nor t h Gr assl an d Wat e r D i st r i ct

South Gr assl an d Wat e r D i st r i ct • S an Lui s Ca n a l Sa l t S l ough 

### San J o a qui n R i v e r

M ud Sl ough ( nor t h )



### • •

CC I D M a i n C a n a l 

### • S an Lui s Dr ai n

G r as s l and B y pa s s



### Figure 3. Wetland Water Supply Schematic After Grassland Bypass Project

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### Numeric Target In 1996, the Regional Board adopted a Basin Plan Am endm ent for the Regulation of Agricultural Subsurface Drainage. The am endm ent contained a selenium water quality objective for wetland water supply channels and Salt Slough. This objective, which was approved by the State Board and the Office of Adm i nistrative Law, is a m onthly m ean concentration of 2 μg/L. The objective for the supply channels was m a de m o re stringent than the selenium objective for downstream waterbodies to offer added protection to the wate rfowl using the wetlands. Based on a review of the available scientif ic literature, the Regional Board determ ined that a 2 μg/L m onthly m ean selenium objective would be protective of waterfowl . This 2 μg/L m onthly m ean selenium objective incorporates a m a rgin of safety because it is based upon threshold water borne concentrations of 2.3 to 2.5 μgL correlated with selenium tissue concentrations in aquatic birds that have shown im paired hatchability of eggs and susceptibility to disease (Calif ornia Regional W a ter Quality Control Board, Central Valley Region; 1996; pg. 61).

Consideration was given to translating the selenium water quality objective into a load lim it, but water quality data collected in wetland water delivery channels in the late 1980’s through early 1990’s showed little change in concentration even in response to significant load reductions (California Regional W a ter Quality Control Board, Central Valley Region; 1995; pp. 5-7). Based on this inform ation, the Regional Board concluded that rem oval of untreated subsurface agricultural drainage was required to m eet water quality objectives (Calif ornia Regional W a ter Quality Control Board, Central Valley Region; 1996; pp. 67-68). Therefore, a concentration based objective was determ ined to be the best m easure of success for protecting beneficial uses and achieving water quality im provem e nts. The num eric target for wetland water supply channels and the Grassland Marshes TMDL is the adopted Basin Plan selenium water quality objective of 2 μg/L (m onthly m ean).

Source Analysis Although selenium exists naturally in the soils of this watershed, som e land use practices accelerate its m ovem e nt to ground water and surface water. Prior to the Grassland Bypass Project, water supply for the Grassland Marshes shared conveyance channels with subsurface and surface drainage from the DPA. Subsurface dr ainage, specifically from the tile drains in the DPA, is the m o st signif i cant source of selenium in the Grassland W a tershed. A survey of tile drainage in the San Joaquin River Basin (Chilc ott et al., 1988) found the highest concentrations of selenium in the Grassland W a tershed. Eighty-two percent of the sam p les collected at 173 tile drainage sites in the Grassland W a tershed had selenium concentrations ranging from 11 to 500 μg/L. The Regional Board has conducted water quality sam p ling in wetland water supply channels since 1985. Som e of these channels, such CCID Main Canal at Russel Blvd., are upstream of the tile drainage discharges from the DPA. This site represents background selenium concentrations in supply water delivered to the wetland channels. The source of water in CCID Main Canal at Russel Blvd. includes deliveries from the Delta Mendota Canal, Mendota Pool, and agricultural return flows from outside the DPA. The m e dian value of selenium was 1.6 μg/L and the m ean was 2.2 μg/L for over 200 sam p les collected (California Regional W a ter Quality Control Board, Central Valley Region; February, 1998a; pg. 178).

Tile drainage from the Drainage Project Area is the prim ary source of selenium in the Grassland W a tershed. There are no m unicipal or industrial sources. Selenium is a naturally occurring

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### elem ent in sedim e nts of the Grassland W a tershed. Selenium can therefore be found in surface runoff and groundwater throughout the watershed.

Implementation Plan In 1996, the Regional Board am ended its Basin Plan for control of agricultural subsurface drainage discharges. This Basin Plan Am endm en t prohibits discharge of subsurface drainage water to Grassland W a tershed wetland supply channels if the discharge results in concentrations exceeding the water quality objective. Rem oval of selenium from wetland supply channels will

rem ove the source of selenium loading to the Grassland Marshes. This prohibition has elim inated the largest loading of selenium to the wetland supply channels. Since Septem ber 1996, the Grasslands Bypass Project has isolated a nd rerouted tile drainage from the DPA away from wetland supply channels by using a portion of the form er San Luis Drain to convey tile drainage directly to Mud Slough. The San Luis Drain discharges to Mud Slough approxim a tely nine m iles upstream of the San Joaquin River confluence (figure 3).

Other sources of water in the wetland supply channels are deliveries from the Delta Mendota Canal and Mendota Pool via the Main Canal, we tland discharges, overland flows from the DPA during storm events, surface agricultural return flows, and groundwater accretions. Inform ation available prior to 1996 indicated that selenium concentrations of those sources com m only fell below 2 μg/L. On this basis, no other im plem entation provisions appeared necessary, nor were included, in the 1996 Basin Plan Am endm ent for the Control of Agricultural Subsurf ace Drainage Discharges (Calif ornia Regional W a te r Quality Control Board, Central Valley Region; 1996).

Allocations Subsurface drainage is prohibited from discharg e into Grassland wetland supply channels if the discharge results in concentrations exceeding the water quality objective; therefore, the subsurface drainage allocation is expressed as the water quality concentration of 2 μg/L as a

m onthly m ean. As discussed in the Source Analysis section above, load allocations for the surface agricultural drainage and wetlands discharges are not necessary since they are not significant sources. Regional Board m onitoring data shows that surface agricultural drainage and wetland discharges typically have selenium concentrations of less than 2 μg/L. Background sources such as groundwater and surface runoff are given a load allocation expressed as a

m onthly m ean water quality concentration of 2 μg/L.

Performance Measures and Feedback W a ter quality m onitoring conducted after the start of the Grassland Bypass Project in Septem ber, 1996 indicates that overall selenium concentrations in wetland supply channels have decreased dram atically, although the m ean m onthly objective is still being exceeded. The 2 μg/L objective has been exceeded in ten out of 24 m onths in the Santa Fe Canal (figure 4) and eleven out of 24

m onths in the San Luis Canal (figure 5). The 2 μg/L objective has been exceeded in 10 out of 24

m onths in the Cam p 13 canal (figure 6) and 5 out of 24 m onths in the Agatha Canal (figure 7). These four channels are representative of supply channels that deliver water to the Grassland Marshes.

80 2 5 5 0 7 5 1 0 0

S e p - 9 2 S e p - 9 3 S e p - 9 4 S e p - 9 5 S e p - 9 6 S e p - 9 7 S e p - 9 8 S e ptembe r 199 2 t o S e pt e m b e r 19 98

Sel e ni u m ( μ g/L ) Au g u st 19 96 t o S e p t em b e r 19 98

0 2 4 6 8 1 0

A u g - 9 6 F e b - 9 7 A u g - 9 7 F e b - 9 8 A u g - 9 8 Au g u st 19 96 t o S e p t em b e r 19 98

Sel e ni u m ( μ g/L )



### Figure 4. Mean Monthly Selenium in Santa Fe Canal

0 2 5 5 0 7 5 1 0 0

S e p - 9 2 S e p - 9 3 S e p - 9 4 S e p - 9 5 S e p - 9 6 S e p - 9 7 S e p - 9 8 S e ptembe r 199 2 t o S e pt e m b e r 19 98

Sel e ni u m ( μ g/L ) Au g u st 19 96 t o S e p t em b e r 19 98

0 2 4 6 8 1 0

A ug- 9 6 F eb- 9 7 A ug- 9 7 F eb- 9 8 A ug- 9 8 Au g u st 19 96 t o S e p t em b e r 19 98

Sel e ni u m ( μ g/L )



### Figure 5. Mean Monthly Selenium in San Luis Canal

90 2 5 5 0 7 5 100

S ep- 9 2 S ep- 9 3 S ep- 9 4 S ep- 9 5 S ep- 9 6 S ep- 9 7 S ep- 9 8 S e ptembe r 199 2 t o S e pt e m b e r 19 98

Sel e ni u m ( μ g/L ) Au g u st 19 96 t o S e p t em b e r 19 98

0 2 4 6 8 1 0

A ug- 9 6 F eb- 9 7 A ug- 9 7 F eb- 9 8 A ug- 9 8 Au g u st 19 96 t o S e p t em b e r 19 98

Sel e ni u m ( μ g/L )



### Figure 6. Mean Monthly Selenium in Camp 13 Canal

0 2 5 5 0 7 5 1 0 0

S e p - 9 2 S e p - 9 3 S e p - 9 4 S e p - 9 5 S e p - 9 6 S e p - 9 7 S e p - 9 8 S e ptembe r 199 2 t o S e pt e m b e r 19 98

Sel e ni u m ( μ g/L ) Au g u st 19 96 t o S e p t em b e r 19 98

0 2 4 6 8 1 0

A ug- 9 6 F eb- 9 7 A ug- 9 7 F eb- 9 8 A ug- 9 8 Au g u st 19 96 t o S e p t em b e r 19 98

Sel e ni u m ( μ g/L )



### Figure 7. Mean Monthly Selenium in Agatha Canal

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### Most elevated selenium concentrations occurre d during and im m e diately following storm events when surface runoff from the DPA that exceeded the capacity of the GBP was diverted into the wetland supply channels (Chilcott, 2000). There are som e m i nor exceedances throughout the year. The m e dian annual selenium concentration was less than or equal to 2.0 μg/L for all four sites in water years 1997 and 1998 except for the Santa Fe Canal which had a m e dian concentration of 2.1 μg/L in water year 1997 (table 2). These m e dian concentrations are m u ch lower than the concentrations observed prior to use of the Grassland Bypass when m e dian annual selenium concentrations som e tim es exceeded 50 μg/L in these channels. This data suggests that with the control program already in place, m o st of the selenium has been diverted from the wetland supply channels. Annual m e dian selenium concentrations were near or below 2 μg/L, indicating that exceedances of the objective are generally m i nor com p ared with concentrations observed prior to use of the Grassland Bypass.

Moni tori ng Si t e 1 9 8 6 1 9 8 7 1 9 8 8 1 9 8 9 1 9 9 0 1 9 9 1 1 9 9 2 1 9 9 3 1 9 9 4 1 9 9 5 1 9 9 6 1 9 9 7 1 9 9 8 Agat ha C a nal 4 4 3 8 3 9 2

. 9 2 6 5 3 3 1 2 3 1 4 4

. 4 3

. 6 1

. 2 1

. 2

C a m p 13 Sl ough 4 3 4 3 4 3 5 9 5 4 5 5 6 4 5 6 5 8 3 2 5 7 1

. 6 1

. 6

CCID Main Can a l @ Ru ssel Blv d

. 1

. 3 2

. 2 1

. 7 1

. 7 2

. 3 1

. 5 2 1

. 4 1

. 7 1

. 4 0

. 9

- 1

. 1

Sant a Fe C a nal @ Henry Miller Ro ad 2 5 3 0

- - - - - 5

. 3 1

. 8 1

. 7 1

. 8 2

. 1 1

. 5

San Lui s C a nal @ Henry Miller Ro ad - - - - - - - 1 2 2

. 5 2

. 2 1

. 8 2 1

. 8



### Table 1. Annual Median Selenium Concentrations A review of potential causes for the continued ex ceedances of the 2 μg/L objective is currently underway. Prelim inary findings from this review suggest several possible causes for the elevated selenium concentrations, including: releases from the DPA during flooding, seepage from DPA gates and canals, elevated selenium concentrations in supply water, surface and subsurface agricultural drainage from areas out side of the DPA, and groundwater accretions (Chilcott, 2000). Most exceedances of the 2 μg/L objectives have been associated with flood flows, seepage from the DPA, subsurface agricultural drainage from outside the DPA, and supply water.

Several efforts are currently underway in response to these findings. A storm w ater m a nagem e nt plan has been put in place by local agencies to reduce selenium loading during and following
storm events and to increase m onitoring during storm events. Other recent efforts have focused on further controlling seepage from the DPA and consolidating and rerouting agricultural discharges f r om outside the DPA. Continued m onitoring will be used to assess the ef f ectiveness of

these actions. Regional Board staf f will review this m onitoring data and will assess other sources, including supply water and groundwater, if selenium objectives are still being exceeded. At this tim e, Regional Board staff believes that corrective action taken to m i nim i ze storm w ater flow, to control subsurface drainage outside the DPA, and to prevent seepage from the DPA, will elim inate the largest exceedances. Further action m a y be needed to elim inate all exceedances, particularly if these exceedances are associated with elevated selenium concentrations in water supplied to the wetland supply channels from the Mendota Pool, the Delta Mendota Canal, and

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### other sources. Appropriate actions will be evaluated subsequent to the corrective actions currently underway. A load allocation for these possible sources is unnecessary at this tim e because the prohibition of subsurface drainage is sufficient to fully im plem ent the TMDL and

m eet the objective. Should further corrective actions be necessary to reduce concentrations in the supply water, a TMDL will be established for the sources of this supply water.

Margin of Safety The Clean W a ter Act requires that a m a rgin of safety be included with TMDL developm ent. Sources of uncertainty in this analysis include the f o llowing three assum p tions:

• there will be no f u ture discharges of tile drainage to wetland channels

• com p lete rem oval of tile drainage alone will result in the attainm e nt of established water quality objectives

• the num eric objective is fully protective of beneficial uses

Load reductions needed to m eet water quality objectives for this TMDL are achieved through the

com p lete prohibition of discharge of tile drainage to wetland water supply channels unless the 2 μg/L objective is being m e t. This prohibition has, in practice, resulted in a selenium load allocation of zero f o r tile drainage. As described in the Implementation Plan section, all tile drainage in the DPA is now discharged to a portion of the San Luis Drain. The m ean annual selenium concentration of tile drainage discharged to the San Luis Drain was 62 μg/L in water year 1997, and 67 μg/L in 1998 (Chilcott et al, 2000). No future discharges of this tile drainage to wetland supply channels will be possible without rem oval of over 95 percent of the selenium load. This level of selenium load reduction is not likely in the foreseeable future. An additional im plicit m a rgin of safety is provided with the 2 μg/L m ean m onthly selenium objective. As explained in the Numeric Target section above, this objective is fully protective of waterfowl.

Com p lete rem oval of selenium load attributable to the m a jor source (tile drainage) provides the

m a xim u m possible m a rgin of safety. Revision of this TMDL or the m a rgin of safety m a y be necessary if ongoing m onitoring suggests that current and subsequent control m easures are insufficient to reduce selenium concentrations in the wetland supply channels below 2 μg/L.

Seasonal Variation The load allocation for subsurface drainage, expressed as a m ean m onthly water quality concentration of 2 μg/L, applies year round. As discussed in the Implementation Plan section, all tile drainage in the DPA is now discharged to a portion of the San Luis Drain. Discharge of tile drainage into wetland supply channels has been elim inated during all seasons of the year including periods of low flow. As discussed in the Numeric Target section above, the 2 μg/L

m ean m onthly selenium objective is fully protective of waterfowl during all seasons.

Prior to the 1996 am endm ents to the Basin Plan, wetland water supplies had generally been protected seasonally during the fall, when seasonal wetlands that had been dry during the

sum m e r m onths were then filled.. Subsequent to this Basin Plan am endm ent, wetland water supplies m a y be delivered to wildlife refuges using the wetland water supply channels at any tim e during the year. A seasonal adjustm e nt in the num eric target (the water quality objective) is therefore not needed.

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### Public Participation The Regional Board held workshops and public hearings for the 1996 Basin Plan Am endm ents for the Control of Agricultural Subsurface Drainage Discharges. The State Board also held approval hearings. Adoption of the Basin Plan Am endm ent in 1996 enabled im plem entation of the Grasslands Marshes TMDL; theref ore, the public hearings held f o r the Am endm ent will be used to fulfill the public participation requirem e nts of this TMDL. The adm i nistrative record for the workshops and public hearings held for the Am endm ent are on file at the Regional Board in five 3.5 inch binders. The index for the adm i nistrative record is included as Attachm e nt 2. Letters received during the com m e nt periods are included in Attachm e nt 3 and responses to these letters and the com m e nts m a de during the workshops are included in Attachm e nt 4.

This TMDL will be incorporated into the Regional Board’s W a ter Quality Control Plan during the next Basin Plan Update. The Grasslands Marshes will be taken off the Section 303(d) list during the next Section 303(d) update, pending full com p liance with established selenium water quality objectives.

References California Regional W a ter Quality Control Board, Central Valley Region, 1995, Staff Report on the Beneficial Uses Designations and Water Quality Criteria to be Use(d) for the Regulation of Agricultural Subsurface Drainage Discharges in the San Joaquin Basin (5c) ; June, 1995.

California Regional W a ter Quality Control Board, Central Valley Region, 1996, Amendments to the Water Quality Control Plan for the Sacramento River and San Joaquin River Basins for the Control of Agricultural Subsurface Drainage Discharges; Staff Report ; March, 1996.

California Regional W a ter Quality Control Board, Central Valley Region, 1998a, Compilation of Electrical Conductivity, Boron, and Selenium Water Quality Data for the Grassland Watershed and San Joaquin River; May 1985-September 1995 ; February, 1998.

California Regional W a ter Quality Control Board, Central Valley Region, 1998b, Fourth Edition of the Water Quality Control Plan (Basin Plan) for the Sacramento River and San Joaquin River Basins ; Septem ber, 1998.

Chilcott, J.E.,1988, Water Quality Survey of Tile Drainage Discharges in the San Joaquin River Basin , Regional W a ter Quality Control Board, Cent ral Valley Region, Staff Report. ,October, 1988.

Chilcott, J.E., 2000, Review of Selenium Concentrations in Wetland Water Supply Channels in the Grassland Watershed, Regional W a ter Quality Control Board, Central Valley Region, Draft Staff Report.

Chilcott, J.E., Grober, L., Vargas, A, Eppinger, J., 2000, Agricultural Drainage Contribution to Water Quality in the Grassland Watershed of Western Merced County, California: October1997 to September 1998 (Water Year 1998) , Draft Staff Report.

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# Attachment Note

Attachm e nts 1 through 4 are available upon request . Please contact Jennifer Heyd at (916) 464 – 4735 or at jheyd@waterboards.ca.gov to request copies.

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