TABLE I-2 STORET Data Used to Calculate Average Oil and Grease Concentrations in Major Inland Rivers

River

Station name

Parameter code

# of observations

Date(s) of observations

Average concentration (mg L−1)

Columbia

Columbia River at Bradwood, OR

00550

27

4/24/74−10/17/78

1.80

Delaware

Delaware Rvr-2000 yds up buoy R6M-Marcus Hook

00556

107

5/23/88−12/29/98

6.00

Delaware (1990s)

Delaware Rvr-2000 yds up buoy R6M-Marcus Hook

00556

99

1/22/90−12/29/98

5.80

Hudson

Hudson River below Poughkeepsie, NY

00550

2

6/4/70−9/7/71

60.50

James

Buoy 8 (City of Hopewell)

00556

1

7/20/92

19.30

Mississippi

Mississippi River at Venice, LA

00556

229

10/4/73−11/19/96

1.74

Mississippi (1990s)

Mississippi River at Venice, LA

00556

46

1/11/90−11/19/96

0.84

Neuse

Neuse River at 3 locations

00550

7

6/6/73−6/7/73

0.00

Sabine

Sabine River at Ruliff, TX

00556

45

3/27/74−5/9/78

2.50

Sacramento

Sacramento River at Freeport, CA

00550

4

10/25/91−2/2/92

0.83

Susquehanna

Susquehanna R at Rte 40 bridge

00500

2

8/3/78

0.00

Trinity

Trinity River at Liberty, TX

00550

11

5/4/71−8/31/72

8.18

Equation I-1

Li=ciQi,

where Li= average annual load for river i (tonne yr−1),

ci= average oil and grease concentration for river i (mg L−1),

Qi= average annual flow for river i (m3 yr1),

tonne= 106 g.

The average annual flow (per calendar year) was determined from USGS daily flow data available for each of the rivers at the nearest nontidally influenced station to that of the reported oil and grease data (Table I-3). For calculations of loads using average concentrations in the 1990s only, average annual flows for those rivers were calculated using only daily flow data from the 1990s.

  1. Using data obtained from the U.S. Bureau of the Census (1998), unit loads per urban land area were calculated as follows:

    Equation I-2

    where lai= unit load per urban land area for river i (g m−2 yr),

    Aui= 1996 urban land area for river i (m2).

    The 1996 urban land area in each river basin was determined by using Table I-1 in U.S. Bureau of the Census (1998), which contained land area data for metropolitan areas defined as of June 30, 1996. Metropolitan areas in this table were partitioned into the major river basins identified in Table I-1, coastal areas, the Great Lakes, or areas not discharging to the coast of the United States or Canada (e.g., Great Salt Lake basin). Metropolitan areas contributing urban runoff to the Great Lakes or areas not discharging to the coast of the United States or Canada were not included further in the analysis. It was assumed that oil and grease dis

TABLE I-3 USGS Gages Used to Calculate Average Annual Flows for Major Inland Rivers

River

Station name

Period of record used

Average annual flow (m3 yr−1)

Columbia

14246900: Columbia R at Beaver Army Terminal nr Quincy, Ore

1969, 1992-1997

220,892,000,000

Delaware

01463500: Delaware River at Trenton, NJ

1913-1997

10,441,000,000

Delaware (1990s)

01463500: Delaware River at Trenton, NJ

1990-1997

10,712,000,000

Hudson

01358000: Hudson River at Green Island, NY

1947-1996

12,365,000,000

James

02037500: James River near Richmond, VA

1938-1997

6,209,000,000

Mississippi

07289000: Mississippi River at Vicksburg, MS

1932-1997

537,114,500,000

Mississippi (1990s)

07289000: Mississippi River at Vicksburg, MS

1990-1997

625,760,000,000

Neusea

02089500: Neuse River at Kinston, NC

1983-1997

3,524,394,745

Sabine

08030500: Sabine River nr Ruliff, TX

1960-1997

7,043,181,292

Sacramento

11447650: Sacramento River at Freeport, CA

1949-1997

21,000,000,000

Susquehanna

01578310: Susquehanna River at Conowingo, MD

1968-1997

36,779,000,000

Trinityb

08067000: Trinity River at Liberty, TX

1977, 1979-1986

8,944,000,000

NOTES: aadjusted to Station 02091814 using 1997 data; bmissing flows regressed with Station 08066500: Trinity River at Romayor, TX (y = 0.8559x + 4047.8).



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