Prepared in cooperation with the 

EL DORADO COUNTY DEPARTMENT OF TRANSPORTATION,

TAHOE ENGINEERING DIVISION

Chemistry of Runoff and Shallow Ground Water at the 

Cattlemans Detention Basin Site, South Lake Tahoe, 

California, August 2000 – November 2001

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2004–5254
(Back of Cover)
Chemistry of Runoff and Shallow Ground Water at the 

Cattlemans Detention Basin Site, South Lake Tahoe, 

California, August 2000 – November 2001

By David E. Prudic, Sienna J. Sager, James L. Wood, Katherine K. Henkelman, and

Rachel M. Caskey

U.S. GEOLOGICAL SURVEY

Carson City, Nevada

2005

Prepared in cooperation with the 

EL DORADO COUNTY DEPARTMENT OF TRANSPORTATION, 

TAHOE ENGINEERING DIVISION

Scientific Investigations Report 2004–5254
U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

CHARLES G. GROAT, Director

Any use of trade, product, or firm names in this publication is for descriptive

purposes only and does not imply endorsement by the U.S. Government

For additional information For more information about the

contact: U.S. Geological Survey and its

products:

District Chief 

U.S. Geological Survey <http://www.usgs.gov>

333 West Nye Lane, Room 203 Telephone: 1-888-ASK-USGS

Carson City, NV 89706–0866

Email: GS-W-NVpublic-info@usgs.gov

<http://nevada.usgs.gov>
 iii

CONTENTS

Abstract. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 

Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 

Description of Cold Creek . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Location and Description of Cattlemans Detention Basin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 

Urban Runoff from Pioneer Trail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Well Location and Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 

Measurement of Water Levels in Wells and Stage of Cold Creek . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Water Quality Sampling Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Urban Runoff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Ground Water and Cold Creek . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Analyses of Water Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Urban Runoff. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Ground Water. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Distribution of Unconsolidated Deposits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Direction of Ground-Water Flow. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Seasonal Trends in Ground-Water Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Quality of Ground Water, Cold Creek, and Precipitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Chemical Composition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Distribution of Total Dissolved Solids, Chloride, and Iron. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Distribution of Nutrients and Organic Carbon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Seasonal Variations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Summary and Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

References Cited. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

FIGURES

1. Map showing location of Lake Tahoe and study area adjacent to Cold Creek, South Lake Tahoe, California . . . . . . . . . . . . . . . . . . 3

2. Aerial view showing different channels of Cold Creek near Cattlemans detention basin prior to its construction. . . . . . . . . . . . . . 4

3. Photographs showing Cold Creek in January 2001 at the first meander adjacent to Cattlemans detention basin prior 

to its construction, and Cold Creek in May 2001 downstream of detention basin prior to its construction. . . . . . . . . . . . . . . . . . . . . . . 5

4. Drawing of Cattlemans detention basin in relation to Cold Creek, Pioneer Trail, and Cattlemans Court, and location of 

wells drilled during November and December 2000. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

5. Aerial view showing location of areas that contributed runoff to the area of the planned Cattlemans detention basin prior 

to its construction in August and September 2001. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

6. Photographs showing selected features in the area of Cattlemans detention basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

7. Diagram showing construction of wells in the area of Cattlemans detention basin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

8. Vertical section showing distribution of shallow unconsolidated deposits beneath Cattlemans detention basin prior to its

construction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

9. Graphs showing time-distance curves and velocity-depth profile for seismic-refraction line A–A' near Cattlemans 

detention basin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

10. Drawing of ground-water level contours for May 2001 in the area of Cattlemans detention basin prior to its construction. . . . . 17
iv 

11. Graphs showing trends of ground-water levels in wells with recording pressure transducers in the area of Cattlemans

detention basin prior to and during its construction in relation to precipitation and air temperature, January through 

September 2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

12. Graphs showing trends of ground-water levels from periodic measurements in wells without recording pressure 

transducers in the area of Cattlemans detention basin prior to and during its construction, December 2000 through

October 2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

13. Graph showing relation between stage of Cold Creek and ground-water level at well cc14 on west side of Cattlemans

detention basin prior to and during its construction, June through September 2001. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

14. Graph showing relation between total dissolved solids and dissolved chloride and bromide in ground water in the area 

of Cattlemans detention basin prior to and during its construction, January to November 2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

15. Drawing of distribution of total dissolved solids, dissolved chloride, and dissolved iron in ground water from meadow 

deposits in the area of Cattlemans detention basin prior to its construction, late April and May 2001 . . . . . . . . . . . . . . . . . . . . . . . . . . 25

16. Vertical sections showing distribution of total dissolved solids, dissolved chloride, and dissolved iron in ground water

beneath Cattlemans detention basin prior to its construction, late April and May 2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

17. Drawing of distribution of dissolved ammonia plus organic nitrogen, dissolved phosphorus, and dissolved organic carbon

in ground water from meadow deposits in the area of Cattlemans detention basin prior to its construction, late April and

May 2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

18. Vertical sections showing distribution of dissolved ammonia plus organic nitrogen, dissolved phosphorus, and dissolved

organic carbon in ground water beneath Cattlemans detention basin prior to its construction, late April and May 2001 . . . . . . . 33

19. Graph showing relation between the mean concentration of dissolved organic carbon to mean concentration of total 

dissolved nitrogen in ground-water samples from the area of Cattlemans detention basin prior to and during its 

construction, January to November 2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

20. Graphs showing trends of major dissolved constituents in ground water from meadow deposits in the area of Cattlemans

detention basin prior to and during its construction, January to November 2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

21. Graphs showing trends of major dissolved constituents in ground water from deeper sand and gravel in the area of 

Cattlemans detention basin prior to and during its construction, January to November 2001. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

22. Graphs showing trends of dissolved nitrogen and phosphorus in ground water from meadow deposits in the area of

Cattlemans detention basin prior to and during its construction, January to November 2001. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

23. Graphs showing trends of dissolved nitrogen and phosphorus in ground water from deeper sand and gravel in the area

of Cattlemans detention basin prior to and during its construction, January to November 2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

24. Graphs showing trends of dissolved organic carbon in ground water in the area of Cattlemans detention basin prior to and 

during its construction, January to November 2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

TABLES

1. Well name, land-surface altitude, and construction data for wells in the area of Cattlemans detention basin, South Lake 

Tahoe, California. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2. Duration, total volume, nutrient mass, and total suspended solids of urban runoff from Pioneer Trail and Montgomery

Estates subdivision, August 2000 to March 2001. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

3. Median and mean concentrations of dissolved constituents in ground water and in Cold Creek in the area of 

Cattlemans detention basin prior to and during its construction, South Lake Tahoe, California, and in perennial and 

ephemeral springs in granitic rocks and snow in the Sierra Nevada . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

4. Concentrations of principal dissolved inorganic constituents and dissolved organic carbon in ground water in the area of 

Cattlemans detention basin prior to and during its construction, South Lake Tahoe, California, January to November 2001. . . . 23

5. Concentrations of dissolved inorganic trace elements in ground water in the area of Cattlemans detention basin prior to 

and after its construction, South Lake Tahoe, California, January to November 2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

6. Concentrations of dissolved nutrients in ground water in vicinity of Cattlemans detention basin prior to and during its 

construction, South Lake Tahoe, California, January to November 2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
 v

CONVERSION FACTORS AND VERTICAL DATUM 

Multiply By To obtain

Length

inch (in.) 25.4 millimeter

foot (ft) 0.3048 meter

mile (mi) 1.609 kilometer

Area

square foot (ft2) 0.09290 square meter

square mile (mi2) 2.590 square kilometer

Volume

quart (qt) 0.9464 liter 

gallon (gal) 3.785 liter 

cubic foot (ft3) 0.02832 cubic meter

Flow rate

foot per second (ft/s) 0.3048 meter per second

cubic foot per second (ft3/s) 0.02832 cubic meter per second

Mass

ounce, avoirdupois (oz) 28.35 gram

pound, avoirdupois (lb) 0.4536 kilogram

Temperature: Degrees Celsius (oC) can be converted to degrees Fahrenheit (oF) by using the formula oF = [1.8(oC)]+32. Degrees 

Fahrenheit can be converted to degrees Celsius by using the formula oC = 0.556(oF-32).

Sea level: In this report, “sea level” refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929, formerly called 

“Sea-Level Datum of 1929”), which is derived from a general adjustment of the first-order leveling networks of the United States 

and Canada.

Horizontal coordinate information is referenced to North American Datum of 1983 (NAD 1983).

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 25°C).

Concentrations of chemical constituents in water are given in milligrams per liter (mg/L) or micrograms per liter (μg/L).

Chemistry of Runoff and Shallow Ground Water at the 

Cattlemans Detention Basin Site, South Lake Tahoe, 

California, August 2000 – November 2001

By David E. Prudic, Sienna J. Sager, James L. Wood, Katherine K. Henkelman, and Rachel M. Caskey

Abstract

A study at the Cattlemans detention basin site began in 

November 2000. The site is adjacent to Cold Creek in South 

Lake Tahoe, California. The purpose of the study is to evaluate 

the effects of the detention basin on ground-water discharge and 

changes in nutrient loads to Cold Creek, a tributary to Trout 

Creek and Lake Tahoe. The study is being done in cooperation 

with the Tahoe Engineering Division of the El Dorado County 

Department of Transportation. This report summarizes data 

collected prior to and during construction of the detention basin 

and includes: (1) nutrient and total suspended solid concentrations of urban runoff; (2) distribution of unconsolidated deposits; (3) direction of ground-water flow; and (4) chemistry of 

shallow ground water and Cold Creek.

Unconsolidated deposits in the area of the detention basin 

were categorized into three classes: fill material consisting of 

a red-brown loamy sand with some gravel and an occasional 

cobble that was placed on top of the meadow; meadow deposits 

consisting of gray silt and sand with stringers of coarse sand and 

fine gravel; and a deeper brown to yellow-brown sand and 

gravel with lenses of silt and sand. Prior to construction of the 

detention basin, ground water flowed west-northwest across the 

area of the detention basin toward Cold Creek. The direction of 

ground-water flow did not change during construction of the 

detention basin. 

Median concentrations of dissolved iron and chloride were 

500 and 30 times higher, respectively, in ground water from the 

meadow deposits than dissolved concentrations in Cold Creek. 

Median concentration of sulfate in ground water from the 

meadow deposits was 0.4 milligrams per liter and dissolved 

oxygen was below the detection level of 0.3 milligrams per liter. 

The lack of oxygen in the shallow ground water likely is caused 

by microbial oxidation of organic matter. The higher chloride 

concentrations in ground water compared with Cold Creek 

likely are caused from the application of salt on Pioneer Trail 

and streets in Montgomery Estates subdivision during the 

winter. Runoff from these roads contributes to the recharge of 

the shallow ground water. The range of dissolved constituents 

generally was greater in the meadow deposits than in the deeper 

sand and gravel. 

Ammonia plus organic nitrogen were the dominant forms 

of dissolved nitrogen and concentrations ranged from 0.04 to 

18 milligrams per liter as nitrogen. Highest concentration was 

beneath the middle of the detention basin. Nitrate plus nitrite 

concentrations were low (<0.33 milligrams per liter as nitrogen) 

throughout the area and dissolved phosphorus concentrations 

ranged from 0.001 to 0.34 milligrams per liter. Nitrogen and 

dissolved organic carbon showed no consistent pattern in the 

direction of ground-water flow, which suggests that, similar to 

iron and sulfate, local variations in the chemical and biological 

reactions within the meadow deposits controlled the variation in 

nitrogen concentrations. The gradual increase in dissolved 

phosphorus along the direction of ground-water flow suggest 

that phosphorus may be slowly dissolving into ground water. 

Dissolved phosphorus was consistently low in July, which may 

be the result of greater microbial activity in the unconsolidated 

deposits or from uptake by roots during the summer. 

Introduction

Lake Tahoe is a beautiful high alpine lake and a popular 

vacation destination. The lake is located on the State line of 

Nevada and California near the crest of the Sierra Nevada, 

about 150 mi northeast of San Francisco (fig. 1). Lake Tahoe 

is remarkable in its size, depth, and clarity, and it is considered 

by many to rank amongst the world's most beautiful scenes 

(Crippen and Pavelka, 1970). Unfortunately, Lake Tahoe's

clarity has been decreasing (Goldman, 1988). The decrease 

in clarity has been attributed to increased sediments and 

nutrients in surface water entering the lake as a result of human 

activity (Crippen and Pavelka, 1970; Glancy, 1988; and 

Goldman, 1988; Goldman and Byron, 1986).

Maintaining Lake Tahoe's beauty continues to be a priority 

for the states of California and Nevada as well as the Federal 

Government. Additionally, the Clean Water Act greatly 

affected transportation agencies by requiring implementation of 

wetland mitigation and urban detention basins in response to 

provisions of the act (Yu and others, 1998). Numerous detention basins have been constructed in the Lake Tahoe Basin 

(Fenske, 1990; Reuter and others, 1992b) in response to the 

Clean Water Act and to help maintain Lake Tahoe's clarity. 
2 Chemistry of Runoff and Shallow Ground Water at the Cattlemans Detention Basin Site, South Lake Tahoe, California

Constructing wetlands in or adjacent to urban detention basins 

have improved the quality of urban runoff (Scherger and Davis, 

1982; Martin, 1986; Reuter and others, 1992a; and Reuter and 

others, 1992b; Hydro Science, 2000, p. 44). Conversely, the 

potential exists for degrading water quality in ground water 

beneath the detention basins and associated wetlands (K.B. 

Foster Civil Engineers, Inc.,1989; Church and Friesz, 1993; 

Granato and others, 1995).

This study is being done in cooperation with the El Dorado 

County Department of Transportation, Tahoe Engineering 

Division (TED). TED started data collection in 1999 through a 

Tahoe Keys Mitigation Grant. The cooperative study began in 

November 2000, ten months prior to actual construction of the 

detention basin. Through funding from California Tahoe

Conservancy, El Dorado County entered into a joint funding 

agreement with the U.S. Geological Survey (USGS) to continue 

the study through 2006.

Purpose and Scope

The purpose of the study is to evaluate the effects of 

Cattlemans detention basin on ground-water discharge and 

changes in nutrient and sediment loads to Cold Creek, a 

tributary to Trout Creek and Lake Tahoe. Cattlemans detention 

basin is along Pioneer Trail in South Lake Tahoe, California 

(fig. 1). The detention basin was constructed in August and 

September 2001 as part of the El Dorado County Pioneer 

Trail III Erosion Control and Bike Lane Project. 

The scope of the project is to: (1) estimate the quantity of 

urban runoff that enters and exits the detention basin along with 

estimates of total nutrient and suspended sediment loads; 

(2) estimate ground-water flow before and after construction of 

the detention basin; and (3) evaluate changes in nutrient loads 

that may enter Cold Creek from increased ground-water flow 

as the result of the detention basin. The overall project includes 

about one year of data collection prior to construction of 

the detention basin and four years of data collection after 

construction. 

This report summarizes data collected prior to and during 

construction of the detention basin and includes: (1) nutrient 

and total suspended solid concentrations of urban runoff collected between August 2000 and March 2001; (2) description 

of unconsolidated deposits determined from the drilling of 

30 monitoring wells in November and December 2000; 

(3) analysis of the direction of ground-water flow between 

January 2001 and November 2001; and (4) chemistry of shallow ground water and Cold Creek between January 2001 and 

November 2001. Data on urban runoff from Pioneer Trail and 

the adjoining Montgomery Estates subdivision and data on 

ground-water levels and water quality were collected prior to 

construction of the detention basin to provide a basis for 

evaluating changes caused by the detention basin. Although the 

detention basin was constructed during August and September 

2001, four ground-water samples from wells adjacent to the 

detention basin were not sampled until November 2001. These 

wells were sampled at a later date because access to them was 

difficult during construction of the detention basin. The samples 

are included with the preconstruction data for continuity with 

samples collected from other wells in September 2001.

The flow-proportional sampler used to monitor flow and to 

collect urban samples from Pioneer Trail and parts of adjacent 

Montgomery Estates was installed and maintained by the TED. 

The USGS measured the stage in Cold Creek, installed monitoring wells, identified the unconsolidated deposits in the subsurface, measured water levels, and collected water samples from 

monitoring wells and from Cold Creek. 

Acknowledgments

Many employees from the TED participated in this study. 

David Friestad designed the Pioneer Trail III Erosion Control 

and Bike Lane Project where the Cattlemans detention basin is 

located. Troy Alexander installed and operated the portable 

automatic flow meters and samplers in a culvert along Pioneer 

Trail prior to construction of the detention basin. The sampler 

captured urban runoff from part of Montgomery Estates subdivision and Pioneer Trail. Initially, the flow meter and sampler 

was loaned to the TED by Vernon Finney from the Department 

of Agriculture, National Resource Conservation Service, Davis, 

California. Clayton Chappell and Janel Gifford from the TED 

and Kimberly Carr from the California Tahoe Conservancy 

were instrumental in developing the work plan and in securing 

funding for this study. Troy Alexander, Clayton Chappell, 

Eric Prouty, and Jennifer Quickel of TED assisted with data 

collection. Finally, precipitation and temperature data used in 

this report was provided by Russell Wigart, Assistant Engineer 

with the City of South Lake Tahoe.

Description of Cold Creek

The headwater area of Cold Creek is in the mountains 

south of Lake Tahoe. The creek flows northwest until it joins 

Trout Creek about 3.6 mi from Lake Tahoe (fig. 1). Cold Creek 

is the largest watershed tributary to Trout Creek. The drainage 

area of Cold Creek is 12.8 mi2

 (Rowe and Allander, 2000, p. 8). 

Upstream of Pioneer Trail, the drainage is largely undeveloped 

and is underlain by granodiorite that is covered in places by 

glacial deposits (Bonham and Burnett, 1976). Cold Creek enters 

a large meadow where Pioneer Trail crosses the creek about 

0.6 mi above its confluence with Trout Creek. 
Description of Cold Creek 3

Figure 1. Location of Lake Tahoe and study area adjacent to Cold Creek, South Lake Tahoe, California (modified from Allander, 2003).

89

50

50

50

89

0

0 1 2 3 KILOMETERS

1 2 3 MILES

Nevada

California California

Lake

Tahoe

South Lake South Lake

Tahoe

Tahoe Keys Tahoe Keys

Meyers

Stateline Stateline

Trout C reek

Upper

Truckee Truckee

River

Nevada

California

Lake

Tahoe

South Lake

Tahoe

Tahoe Keys

Meyers

Stateline

Trout

C reek

Upper

Truckee

River

Pioneer Pioneer

Trail

Pioneer

Trail

Cold C reek

120 ̊00' 119 ̊55'

38 ̊

55'

38 ̊

50'

Base from U.S. Geological Survey digital data, 1:24,000 and 1:100,000, 

1969–85 Universal Transverse Mercator projection, Zone 10

Basin-fill deposits

Study area

Developed area

Bedrock

Boundary of Lake Tahoe

 Basin

Boundary of Trout Creek

 watershed

EXPLANATION

Area

of map

Lake

Tahoe

Fallen

Leaf Lake

CALIFORNIA

NEVADA

San

Francisco

San Francisco San

Francisco

Reno

Sierra NevadaSierra Nevada

Carson RangeCarson Range
4 Chemistry of Runoff and Shallow Ground Water at the Cattlemans Detention Basin Site, South Lake Tahoe, California

Cold Creek and the meadow have undergone several 

changes since the early 1950's (fig. 2). Prior to the development 

of the surrounding area, Cold Creek flowed through the 

meadow in a relatively small and shallow channel. The channel 

likely did not extend far below the water table; rather the channel bottom in the sandy deposits was controlled by the groundwater level, which in the meadow, is only a few feet below land 

surface. During periods of high flow, usually in the spring and 

early summer, the creek would leave its banks and flow across 

the meadow, which effectively filtered the sediment from the 

water.

By 1969, a small dam had been constructed across the 

1954 channel of Cold Creek about midway between Pioneer 

Trail and its confluence with Trout Creek, which created Lake 

Christopher (fig. 2). Sometime between 1969 and 1987 a ditch 

was excavated along the northern edge of the meadow. The 

ditch was used to both divert flow around Lake Christopher and 

to supply flow to the lake.

The dam was removed and the channel of Cold Creek was 

reconstructed in 1994 into its present form (fig. 2; Kimberly 

Carr, California Tahoe Conservancy, oral commun., 2003). 

The reconstructed channel is wider and deeper than the natural 

channel and has a greater sinuosity. The channel was designed 

to contain most of the flow within its banks (fig. 3A). The 

excavation of the channel below the water table and the creation 

of meanders that cross the direction of ground-water flow in 

the meadow likely increased ground-water exchange with the 

creek as compared to the exchange with the natural channel. 

The increased ground-water exchange may in part be responsible for bank instability and erosion along the channel (fig. 3B), 

particularly along meanders that are perpendicular to the slope 

of the meadow (see fig. 2). 

Figure 2. Different channels of Cold Creek near Cattlemans detention basin prior to its construction, South Lake Tahoe, 

California on three dates between 1954 and 2000 and seismic-refraction line A–A' used to determine thickness of 

unconsolidated deposits.

Image base from Space Imaging, IKONOS-2, Pan sharpened natural color, Aug 10, 2000

Universal Transverse Mercator projection, Zone 10, NAD 1983

119 ̊58'0" 119 ̊57'50"

38 ̊54'30"

38 ̊54'40"

38 ̊54'50"

0 50 100 150 METERS

0 200 400 600 FEET

Stream channel

2000

1987

1954

Area of Figure 4 Area of Figure 4 rea of Figure 4

Pioneer 

 

Trail

Lake Christopher 

 in 1987

A

A'

Seismic line
Location and Description of Cattlemans Detention Basin 5

Location and Description of Cattlemans 

Detention Basin

Cattlemans detention basin is located at the end of Cattlemans Court cul-de-sac and is bordered by Pioneer Trail to the 

east and Cold Creek to the north and west (fig. 4). Construction 

began in late August 2001 and ended in late September 2001.

Prior to construction of the detention basin, urban runoff 

from part of Montgomery Estates flowed through a culvert on 

the west side of Pioneer Trail and discharged into Cold Creek 

through a shallow ditch excavated along the base of Pioneer 

Trail (fig. 5). Runoff from a small area along the east side of 

Pioneer Trail entered Cold Creek through a small gully on the 

southeast side. Once in the gully, the runoff discharged into an 

abandoned meander of Cold Creek that joined the active channel just upstream from the culvert beneath Pioneer Trail (fig. 5). 

Runoff from Cattlemans Court and from part of Montgomery 

Estates subdivision flowed into a storm drain at the north edge 

of the cul-de-sac, where it flowed north through a short section 

of culvert before it discharged to the surface of a large flat area. 

Runoff generally flowed northwest on the large flat area (fig. 5). 

The large flat area (fig. 6A) at the end of Cattlemans Court was 

constructed during development of the adjacent subdivision 

when 4 to 5 ft of fill was placed on top of the meadow. Following completion of the detention basin, runoff from these three 

areas were rerouted into Cattlemans detention basin through a 

series of buried culverts (fig. 4).

Figure 3. Photographs showing (A) Cold Creek in January 2001 at the 

first meander adjacent to Cattlemans detention basin prior to its 

construction, and (B) Cold Creek in May 2001 downstream of detention 

basin prior to its construction, South Lake Tahoe, California. Photograph 

(B) shows a plastic pipe and large boulders that are stained orange 

indicating precipitation of iron on the streambed.

A

B
6 Chemistry of Runoff and Shallow Ground Water at the Cattlemans Detention Basin Site, South Lake Tahoe, California

The unlined detention basin was constructed to hold a total 

volume of 22,000 ft3

 without surface discharge (Jennifer 

Quickel, Tahoe Engineering Division, El Dorado County 

Department of Transportation, written commun., 2003). Much 

of the fill that had been placed in the area was removed during 

excavation of the detention basin (fig. 6B). A spillway was 

constructed of concrete with large boulders on the west side of 

the detention basin (fig. 6C). Overflow from the detention basin 

is routed through the spillway and apron into the adjacent 

meadow. The capacity of the basin when the spillway is at the 

maximum altitude of 6,276 ft is 28,500 ft3

 (Jennifer Quickel, 

written commun., 2003). Flow into the meadow is retained 

behind bundled straw (referred to as a biolog) to prevent 

overflow from the detention basin directly reaching Cold Creek 

(fig. 6D).

Methods

Urban Runoff from Pioneer Trail

Urban runoff from Pioneer Trail was monitored in a culvert on the west side of Pioneer Trail prior to construction of the 

detention basin. A portable automatic flow meter and sampler 

(ISCO 6700 provided by the National Resources Conservation 

Service) was installed in the culvert at an access location on the 

west side of Pioneer Trail in April 2000. The sampler was 

replaced in April 2001 with an American Sigma sampler 

(900MAX) and flow meter (950). The pump on the American 

Sigma is a high speed peristaltic, dual roller that uses a 3/8 in. 

inside diameter by 5/8 in. outside diameter medical grade 

Figure 4. Cattlemans detention basin in relation to Cold Creek, Pioneer Trail, and Cattlemans Court, and location of 

wells drilled during November and December 2000. Well name listed in table 1 has been abbreviated by omitting the

“cc” designation.

0 50 METERS

0 200 FEET

Cold Creek

Biolog 

Diversion D

D

D

D

1

2

4

D

3

5

6

7

8

9

10

11

12

13

14

15

D

16 17

18

19

20

21

22 23

24

24

Spillway

Cattlemans Court

Gate

Road

slope

Pioneer 

Trail

NORTH

Shallow monitoring well and well number 

 (D indicates an adjacent deep well)

Surface-water level recorder

Surface-water flow direction

Ground-water level recorder

Stormwater drain

EXPLANATION

Base from Tahoe Engineering Division, El Dorado County Department of Transportation, Nov 2000
Methods 7

Figure 5. Location of areas that contributed runoff to the area of the planned Cattlemans 

detention basin prior to its construction in August and September 2001.

N

119 ̊57'50" 119 ̊57'30"

38 ̊54'30"

38 ̊54'10"

0 1 MILE 0.5

0 1 KILOMETER 0.5

Image base from Space Imaging, IKONOS-2, Pan sharpened natural color, Aug 10, 2000

Universal Transverse Mercator projection, Zone 10, NAD 1983

Storm drain

Weather station

EXPLANATION

30-inch culvert

Surface drainage

Montgomery Montgomery

Estates drainage Estates drainage

area

Montgomery

Estates drainage

area

Cattlemans attlemans

drainage drainage

area

Cattlemans

drainage

area

Pioneer Pioneer

Trail

Pioneer

Trail

Cold Creek
8 Chemistry of Runoff and Shallow Ground Water at the Cattlemans Detention Basin Site, South Lake Tahoe, California

A

B

Figure 6. Photographs showing selected features in the area of Cattlemans detention basin: (A) May 2001, view 

looking northwest across large flat area at end of Cattlemans Court prior to construction of detention basin; 

(B) September 2001, view looking east across flat area from well cc13 during construction of detention basin; 

(C) March 2002, view looking south across spillway structure of detention basin to Cattlemans Court; and 

(D) March 2002, view looking west from the spillway across meadow showing biolog used to keep overflow 

from entering Cold Creek. 
Methods 9

Figure 6.—Continued.

C

D
10 Chemistry of Runoff and Shallow Ground Water at the Cattlemans Detention Basin Site, South Lake Tahoe, California

silicone rubber pump tube. Clear flexible polyvinyl chloride 

(PVC) tubing (3/8 in. inside diameter by 5/8 in. outside 

diameter) was used for the intake line from the culvert to the 

sampler. The pump and intake tubing was similar for the ISCO 

6700 sampler. The purpose of the flow meters and automatic 

samplers was to monitor the volume of runoff and the total load 

of nutrients and sediments that discharge through the culvert. 

The sampler was set to collect 1.1 qt (1 liter) of water for every 

1,500 ft3 of flow that passed through the culvert. The initial 

sampler had 21 bottles and each bottle was 0.8 qt (750 milliliters). Water samples were collected in sequence. The replacement sampler had 8 bottles and each bottle was 2.1 qt (2 liters). 

During runoff, the ISCO 6700 sampler collected a flow 

portioned sample every 5 minutes whereas the American Sigma 

collected a 0.21-qt (200-milliliters) sample for every 300 ft3

of flow and thus, the sample interval was dependent on the flow 

volume. Because nutrient samples are time critical and must 

be kept chilled, the sampler was routinely checked during and 

between storms. 

Well Location and Construction

Because of concern over potential transport of nutrients 

by ground water from the detention basin to Cold Creek, 

30 monitoring wells were installed prior to construction (fig. 4). 

The locations of the wells were selected specifically to help 

determine directions of ground-water flow in the area of the 

detention basin and the exchange of ground water with Cold 

Creek. Wells were placed east and south of the planned detention basin where the land surface altitude was higher, to the 

north and west between the planned detention basin and Cold 

Creek, and in the meadow west of the planned spillway structure where the land surface altitude was lower than the basin. 

In this report, a shallow well adjacent to the deeper well is 

designated by an S following the well number and the deeper 

well is designated by a D following the well number (for

example; wells cc3S and cc3D, table 1). 

Wells were installed during November and December 

2000. A trailer mounted hollow-stem auger was used to install 

wells in the area where 4 to 5 ft of fill had been previously 

placed on top of the meadow. The augered holes measured 7 in. 

in diameter. Well casings made of nominal 2-in. diameter 

schedule 40 PVC pipe were placed in the augered holes at 

depths of 9 to 10 ft below land surface (wells cc3S, cc4, cc5, 

cc6S, cc8S, cc9, cc10, cc13S, and cc15; table 1). These shallow 

wells were completed in the meadow deposits. Each well casing 

had a 1-ft long slotted interval (slot size is 0.02 in.) placed 0.5 ft 

above the bottom of the casing and 2 to 3 ft below the water 

table at the time the wells were drilled. An end cap was attached 

to the bottom of each casing using stainless steel rivets. Deeper 

wells were installed to depths of 15 ft below land surface at 

selected wells (cc3D, cc6D, cc8D, and cc13D; table 1). The 

deeper wells were completed in a brown sand and gravel with 

lenses of silt and sand, and were designed to determine the 

vertical component of ground-water flow and difference in 

water chemistry with depth. 

Monitoring wells in the meadow and along Cold Creek 

were installed in hand-augered holes that were 5 to 7.2 ft below 

land surface (table 1). These hand augered holes were 4.5 in. in 

diameter. Normally, the nominal 2-in. diameter well casing was 

installed in the augered holes. Depth to ground water ranged 

from 2 to 4 ft below land surface at the time the wells were 

installed. A large stone was encountered while augering the 

hole for well cc2 (fig. 4) and a 3-in. diameter auger bucket was 

used until granodiorite was encountered at a depth of 6.8 ft. 

Because of the smaller diameter, a nominal 1-in. diameter 

schedule 40 PVC well casing was installed in the augered hole 

(table 1). The well casing had a one-foot slotted interval (slot 

size is 0.02 in.) placed 0.5 ft above the bottom of the casing. 

The bottom of the casing was capped in the same manner as the 

2-in. diameter well casing.

Two deeper wells were drilled adjacent to wells cc17S and 

cc19S and were designated cc17D and cc19D (table 1). The 

hole for well cc17D was augered by hand using 4.5 in. diameter 

bucket and nominal 2-in. diameter well casing was installed to 

a depth of 10.6 ft. However, because of flowing sands encountered while augering the hole for well cc19D, a 3-in. bucket was 

used inside nominal 4-in. diameter PVC pipe. The pipe was 

designed to prevent sand from entering the hole. The hole was 

deepened by alternately pushing the PVC pipe until refusal and 

then augering out the materials inside the pipe. Total depth of 

the hole was 10 ft. The well was completed in the same manner 

as well cc2 (table 1).

Wells installed to depths of 10 ft or less were one piece and 

excess pipe exposed above land surface was cut prior to attaching the upper cap. Wells deeper than 10 ft were installed by 

attaching a 5-ft section of flush threaded PVC pipe with Teflon 

O-ring seals to the 10-ft length of PVC pipe with screen. Excess 

pipe exposed above land surface also was cut prior to attaching 

the upper cap. Except for the smaller diameter PVC used for 

wells cc2 and cc19D, the construction of these smaller-diameter 

wells was the same as the 2-in. well. A lockable and tightly 

sealed (using two O-rings) cap was placed at the top of each 

2-in. diameter PVC pipe to prevent surface runoff from entering 

the well (fig. 7). The 1-in. diameter wells also were sealed with 

a lockable cap but the cap differs from the 2-in. diameter wells 

in that it uses a rubber gasket to seal the top of the casing. 

Table 1 summarizes the location (latitude and longitude) 

and construction information for each well. 

Once the casing was placed into the hole, the hole around 

the slotted interval of the well was filled with very coarse silica 

sand (0.04 to 0.08 in.) until the sand was about 0.5 to 1 ft above 

the screen (fig. 7). A layer (1 to 3 ft thick) of laboratory grade 

silica flour was placed on top of the very coarse sand. Silica 

flour was used in place of a bentonite grout because of potential 

reactions of the sodium-rich bentonite with the ground water. 

Unconsolidated deposits removed from the hole during augering were placed around the well casing above the silica flour in 

the deeper holes until the hole was filled to within 3 ft of land 

surface. Cement grout was poured in the uppermost 1.5 to 3 ft 

of each hole to seal it. The grout was placed around the 2-in. 

diameter well cap. Each well cap has a flange at its base (fig. 7) 

to prevent the cap from being removed once the cement hardened. The top of each well was at or slightly above land surface.
Table 1. Well name, land-surface altitude, and construction data for wells in the area of Cattlemans detention basin, South 

Lake Tahoe, California

Well

name

Standard

identification

number

1

Standard identification number is used to store all ground water information in the National Water Information System (NWIS). The first 6 

digits are the latitude of the well in degrees, minutes, and seconds; the following 7 digits are the longitude of the well in degrees, minutes, and 

seconds; and the last 2 digits are for sequential numbering of wells when more than one well has the same latitude and longitude. Location of wells 

is shown in figure 4.

1

cc1

cc2

cc3S

cc3D

cc4

385432119574001

385432119574002

385432119574301

385432119574302

385433119574201

6,278.84

6,281.57

6,281.23

6,281.21

6,279.12

 5.6

 6.8

 10.2

 15.1

 10.2

4.1

5.3

8.7

13.6

8.7

5.1

6.3

9.7

14.6

9.7

no

no

yes

yes

no

meadow deposits

weathered granodiorite

meadow deposits

sand and gravel

meadow deposits

cc5

cc6S

cc6D

cc7

cc8S

385433119574202

385433119574301

385433119574302

385433119574203

385432119574303

6,278.03

6,277.37

6,277.40

6,273.29

6,278.134

4Surface casing lowered at wells cc8S and cc8D October 3, 2001 after construction of detention basin. Excavation lowered land surface to 

6,276.63 feet at well cc8S and to 6,276.95 feet at well cc8D. Total depth of well 8S was decreased to 7.7 feet and well cc8D was decreased to 

13.8 feet.

 10.2

 9.0

15.0

 5.0

 9.2

8.7

7.5

13.5

3.5

7.7

9.7

8.5

14.5

4.5

8.7

no

5

Recording pressure transducers initially in wells cc8S and cc8D were moved to wells cc6S and cc6D following construction of detention basin 

in October 2001 because of concerns that the pond behind the detention dam could flood wells cc8S and cc8D.

yes5

yes5

no

yes5

meadow deposits

meadow deposits

sand and gravel

meadow deposits

meadow deposits

cc8D

cc9

cc10

cc11

cc12

385432119574304

385432119574305

385433119574303

385434119574401

385434119574402

6,278.154

6,279.30

6,276.39

6,272.83

6,272.64

 15.0

 9.9

 10.2

 5.7

 5.1

13.5

8.4

8.7

4.2

3.6

14.5

9.4

9.7

5.2

4.6

yes5

no

no

no

no

sand and gravel

meadow deposits

meadow deposits

meadow deposits

meadow deposits

cc13S

cc13D

cc14

cc15

cc16

385433119574401

385433119574402

385433119574403

385432119574401

385433119574404

6,275.14

6,275.69

6,272.60

6,278.33

6,273.47

 10.2

 15.2

 5.5

 10.2

 7.2

8.7

13.7

4.0

8.7

5.7

9.7

14.7

5.0

9.7

6.7

yes

yes

yes

no

no

meadow deposits

sand and gravel

meadow deposits

meadow deposits

meadow deposits

cc17S

cc17D

cc18

cc19S

cc19D

385433119574501

385433119574502

385433119574503

385433119574504

385433119574505

6,272.71

6,272.82

6,271.93

6,272.19

6,272.11

6.7

 10.6

 5.1

 5.6

10.0

5.2

9.1

3.6

4.1

8.5

6.2

10.1

4.6

5.1

9.5

no

no

no

no

no

meadow deposits

sand and gravel

meadow deposits

meadow deposits

sand and gravel

cc20

cc21

cc22

cc23

cc24

385432119574501

385432119574601

385433119574701

385433119574702

385432119574701

6,272.77

6,272.19

6,271.94

6,271.08

6,271.97

 7.2

 5.0

 5.6

 5.4

 5.5

5.7

3.5

4.1

3.9

4.0

6.7

4.5

5.1

4.9

5.0

no

no

no

no

no

meadow deposits

meadow deposits

meadow deposits

meadow deposits

meadow deposits

Methods 11

Land-surface

altitude2

(feet)

2Land-surface altitude referenced to pin set by Tahoe Engineering Division of the El Dorado County Department of Transportation at end of 

Cattlemans Court. Altitude referenced to NGVD of 1929. 

Bottom

of well

(depth,

feet 

below 

land

surface)

Screened interval

(depth, in feet 

below land surface) Wells with

recording

pressure

transducers

Lithologic unit in

which screened

interval of well

is completed3

3Meadow deposits consist of gray silt and sand with stringers of coarse sand and fine gravel. The deeper sand and gravel consists of brown to 

yellow-brown sand and gravel with lenses of silt and sand. Both units are alluvium deposited by Cold Creek.

Top Bottom
12 Chemistry of Runoff and Shallow Ground Water at the Cattlemans Detention Basin Site, South Lake Tahoe, California

Measurement of Water Levels in Wells and Stage of 

Cold Creek

Measurements of depth to water in the wells were made 

periodically. Depth to water was measured using either a steel 

tape or an electric tape calibrated to a steel tape. Water depths 

ranged from 2 ft or less below land surface in wells located next 

to Cold Creek to more than 9 ft below land surface at wells cc3S 

and cc3D. Water-level altitudes were determined by subtracting 

the depth to water in each well from the altitude of the top of 

each well. The altitude of the top of each well was surveyed 

using a Nikon Total Station (model DTM-A5LG) and an altitude reference mark set by the TED at the north end of Cattlemans Court. The reference mark has an altitude of 6,282.85 ft 

above sea level.

Several monitoring wells (cc3S, cc8S, cc8D, cc13S, 

cc13D, and cc14) were installed with Global Water pressure 

transducers (Global Water, Inc. model number WL14x) during 

January 2000 to record changes in water levels during the inaccessible period, when snow covered the ground, and to assess 

daily variations in water levels. Each pressure transducer and 

attached datalogger fits inside the 2-in. diameter PVC casing 

and has a range from 0 to 15 ft. Additional pressure transducers 

were installed in June 2001 at well cc3D and in Cold Creek next 

to well cc14. One pressure transducer failed shortly after it was 

installed in January 2001 and reliable data were not obtained 

until June 2001. Water-level data from the pressure transducers 

were recorded every hour and the data were retrieved from the 

dataloggers using a laptop computer. 

Water Quality Sampling Procedures

Urban Runoff

Samples of urban runoff collected by the automatic samplers were frozen and then sent to a laboratory for nutrient and 

total suspended-solid analyses. The water was unfiltered and 

only total concentrations of nutrients were determined. Initially 

(April and May 2000), most samples were analyzed for total 

suspended solids and selected samples also were analyzed for 

nutrient content. Nutrient analyses of the unfiltered water 

consisted of ammonia (or ammonium), nitrate plus nitrite, total 

Kjeldahl nitrogen (ammonia plus organic nitrogen), soluble 

reactive phosphorus (orthophosphorus), total phosphorus, and 

total iron (analyzed starting October 26, 2000). Because of 

difficulties in estimating the total mass of nutrients from analyses of selected samples for each runoff period in April and 

May 2000, a composite of the individual samples for each 

Sealed and lockable

PVC cap

1-foot long screen

Schedule 40

PVC casing

Hole diameter 4 to 7 inches

Cement grout

1.5 to 3 feet thick

Native material

1 to 6 feet thick

Silica flour

1 to 3 feet thick

Coarse silica sand

2 to 3 feet thick

Figure 7. Diagram showing construction of wells in the area

of Cattlemans detention basin.
Urban Runoff 13

subsequent runoff period was done by shaking each sample and 

mixing a known volume from each that was representative of 

the percentage of the total runoff. The composite, which was 

representative of total runoff, was then analyzed for nutrients.

Ground Water and Cold Creek

Wells selected for chemical and nutrient analyses were 

pumped using a portable battery-operated peristaltic pump 

using C-flex (Masterflex 6424-15) tubing. The C-flex tubing 

was rinsed with deionized water following each sampling. 

About 1 gal was pumped from the wells every 10 min. At least 

three well-bore volumes were pumped prior to sampling. 

Volumes ranged from about 1 qt (for the shallow wells in the 

meadow area) to 2 gal (for the deeper wells). Two wells (wells 

cc17S and cc21) recovered slowly after water was removed 

from the casing. These wells were allowed to recover before 

removing more water from the casing. The process was 

repeated until three well-bore volumes were removed.

Measurements of temperature, specific conductance, and 

pH were made in a flow-through cell at the time the wells were 

sampled. Alkalinity and dissolved oxygen also were determined 

at the time of sampling for wells that were sampled for major 

and trace inorganic dissolved constituents. Bicarbonate concentrations were calculated from alkalinity. Initially, eight wells 

were sampled for dissolved nutrients, organic carbon, and 

major and trace inorganic constituents in January 2001. During 

the spring, summer, and fall of 2001, all wells were sampled for 

nutrients at least once and 26 wells were sampled three times. 

During this same period, 13 wells were sampled three times 

for dissolved organic carbon and major and trace inorganic 

constituents. All ground water samples were filtered through 

a 0.45-micron filter.

Water samples were collected in September 2001, from 

Cold Creek adjacent to well cc1 above Pioneer Trail and well 

cc14 below the detention basin. Samples were collected by 

placing the end of the C-flex tubing from the peristaltic pump 

at mid-depth in the creek and pumping water through a flowthrough chamber prior to collecting the sample. The purpose of 

these samples was to compare the chemical quality of water in 

the creek with that of ground water in the wells next to the creek 

above and below the planned detention basin. Measurements of 

temperature, specific conductance, pH, and dissolved oxygen 

were made in the flow-through chamber at the time of sampling. 

The water samples from Cold Creek were filtered.

Water samples collected for nutrient analyses were split 

into 3 bottles. The nutrient analyses included Kjedahl nitrogen, 

ammonia, nitrate plus nitrite, phosphorus, orthophosphorus, 

and iron. The water sample for filtered iron was acidified with 

nitric acid to a pH of 2.0 or less. The water samples were placed 

on ice and chilled to 4o

C or less and remained chilled until analyzed. Water samples collected for dissolved organic carbon 

were poured into an amber colored glass bottle and preserved 

with 4.5N sulfuric acid. Water samples collected for anions 

were poured into a bottle untreated and the samples that were 

used for cations and trace elements were poured into a separate 

bottle and acidified with nitric acid to a pH of 2.0 or less. One 

unfiltered and untreated water sample was used for laboratory 

determination of specific conductance and pH. 

Analyses of Water Quality

Water samples from urban runoff collected by TED were 

sent to Acculabs, Inc. in Sparks, Nevada, which is an Environmental Protection Agency (EPA) certified laboratory. All other 

water samples collected by the USGS were sent either to the 

USGS National Water Quality Laboratory (NWQL) in Lakewood, Colorado (major and trace inorganic constituents and 

dissolved organic carbon) or to the University of California, 

Davis, Tahoe Research Group (TRG) Laboratories (nutrients 

and filtered iron). Samples for kjeldahl nitrogen (ammonia and 

organic nitrogen) and (filtered and biologically available) 

iron were sent to the University of California, Davis in Davis, 

California and the other samples were sent to the TRG Laboratory in Tahoe City, California. Analytical results from 

all ground water and Cold Creek samples are stored in the 

USGS National Water Information System (NWIS) data base. 

Analytical results from urban runoff are available from TED.

Urban Runoff

Nutrient concentrations in runoff were determined for 

six runoff events that occurred between August 2000 and 

March 2001 (table 2). The largest event with the greatest 

loads occurred on August 3, 2000 when a thunder storm 

resulted in runoff through the culvert of about 30,000 ft3

over a 5-hour period. The estimated total load of nitrogen 

was 190 oz (5,300 grams) of which most was in the form of 

organic nitrogen and the total load of phosphorus was 8.1 oz 

(230 grams; table 2). Total suspended solids were estimated 

at 4,000 lbs. The mean concentration of total nitrogen was 

6.4 mg/L and total phosphorus was 0.28 mg/L. 

The highest runoff rate (total runoff divided by duration) 

occurred on September 1, 2000 when 19,000 ft3

 was estimated 

during a 11⁄2-hr period (table 2). Although the runoff rate 

was more than that of the August storm, the total load of 

nitrogen was only 17 oz (480 grams), phosphorus was 3.9 oz 

(110 grams), and total suspended solids were only 55 lbs. The 

mean concentration of total nitrogen was 0.9 mg/L and total 

phosphorus was 0.2 mg/L. The considerably lower loads may 

have resulted because much of the nutrients and sediments had 

been removed from the drainage area during the August event 

and insufficient time had elapsed to accumulate more. Three 

urban runoff events were recorded in October 2000. Total nitrogen and phosphorus loads in the three October events were 

similar to the September event; however, total suspended solids 

in all three October events were about three times greater than 

the September event. 
14 Chemistry of Runoff and Shallow Ground Water at the Cattlemans Detention Basin Site, South Lake Tahoe, California

Only one urban runoff event was recorded during snowmelt in the spring of 2001. Total runoff for the March 6, 2001, 

event was 26,000 ft3

 and was nearly equal to that on August 3, 

2000, although the duration was 2.5 times longer; however, the 

total nitrogen load for this event was considerably less than that 

for the August 2000 event (table 2). The dominant form of 

nitrogen for the March 6, 2001 event was still organic nitrogen 

even though nitrate (plus nitrite) load was the highest of any 

recorded event. The mean total nitrogen concentration during 

the March 6, 2001 event was 1.7 mg/L, and total phosphorus 

was 0.26 mg/L. 

Ground Water

The shallow ground-water system beneath Cattlemans 

detention basin is a potential pathway for dissolved nutrients in 

urban runoff to reach Cold Creek. Ground water has the potential to flow from the detention basin through unconsolidated 

deposits and discharge into Cold Creek. Understanding groundwater flow is important in assessing how effectively the detention basin reduces nutrients loads to Cold Creek.

Ground water in the area of the detention basin prior to its 

construction primarily was from four sources: recharge from 

precipitation and snowmelt; subsurface flow from the adjacent 

upland areas; seepage from Cold Creek into unconsolidated 

deposits upstream of Pioneer Trail; and periodic infiltration 

of urban runoff. 

Distribution of Unconsolidated Deposits

Unconsolidated deposits penetrated during the augering 

for each monitoring well were classified according to texture, 

color, and odor. Three general classes of unconsolidated deposits were categorized—fill, organic silt and sand, and sand and 

gravel (fig. 8). Fill material consists of red-brown loamy sand 

with some gravel and an occasional cobble. The loamy sand is 

similar to that found in the adjacent uplands and the gravel and 

cobbles are granodiorite. This suggests the fill was obtained 

locally and placed on top of the meadow. Construction 

materials such as wood and electrical wiring were occasionally 

encountered in the fill.

Immediately below the fill are meadow deposits that consist of medium to dark gray organic silt and sand with stringers 

of coarse sand and fine gravel. These deposits contain organic 

matter, have a musty odor, and are generally from 5 to 8 ft thick 

in the area of the detention basin. Mica flecks are common 

throughout the deposits. Roots from the meadow grasses are 

common to a depth of 1 ft and occasional pieces of decomposing wood (possibly roots of large trees) were found in the 

deposits.

The origin of meadow deposits might be related to a 

change in the slope of the Cold Creek channel. Upstream (east) 

of Pioneer Trail, Cold Creek is incised into bedrock and has a 

higher gradient than the channel downstream (west) of Pioneer 

Trail (Harrill, 1977). The deposit could be from the gradual 

accumulation of sediments during flooding that caused Cold 

Creek to overflow its banks and spread across the meadow. 

Another possibility is that the lenses of silt were deposited in 

shallow ponds that may have formed in the meadow. 

The third category of deposits found in the augered holes 

is a sand and gravel with lenses of silt and sand. The thickness 

of this unit is unknown but it was found everywhere beneath the 

gray organic silt and sand. The unconsolidated deposits consist 

of a brown to yellow brown (oxidized) sand and gravel with 

lenses of silt and sand. The deposits are similar in origin to 

the meadow deposits. A profile across the detention basin prior 

to construction (fig. 8) shows the general distribution of unconsolidated deposits.

Table 2. Duration, total volume, nutrient mass, and total suspended solids of urban runoff from Pioneer Trail and 

Montgomery Estates subdivision, August 2000 to March 2001

1

Data are from the Tahoe Engineering Division of the El Dorado County Department of Transportation, South Lake Tahoe, California. 

Nutrient and total suspended solids were analyzed by Acculabs, Inc. in Sparks, Nevada, for El Dorado County Department of Transportation. 

Acculabs is an U.S. Environmental Protection Agency (EPA) certified laboratory. Data used for this table are available through El Dorado 

County Department of Transportation. Sampling location is shown in figure 5.

1

[Symbols: <, less than; --, no data]

Date Duration

(hours)

Total

volume

(cubic feet)

Ammonia Nitrate Nitrite

Ammonia

+ organic

nitrogen

Total

nitrogen

Soluble

reactive

(ortho)

phosphorus

Total

phosphorus

Total

iron

Total

suspended

solids

Ounces of nitrogen Ounces of phosphorus Pounds

08/03/2000

09/01/2000

10/09/2000

10/26/2000

10/28/2000

03/06/2001

5

1.5

2

22

21

13

30,000

19,000

2,600

25,000

17,000

26,000

5.6

1.1

.71

<1.2

<.85

3.1

1.4

2.8

<.14

<.25

<.18

4.9

<0.28

.19

<.03

<.25

<.18

<.28

190

14

21

28

14

39

190

17

21

28

14

44

0.56

1.5

<.07

1.5

.85

.74

8.1

3.9

2.2

4.6

2.5

6.7

--

--

--

6.0

5.3

11

4,000

55

157

163

165

287
Ground Water 15

Depth to bedrock along a north-south profile just west 

of the planned detention basin was estimated from seismicrefraction data (location of north-south profile is shown on 

fig. 2). The following discussion is excerpted from D.L. Berger 

(U.S. Geological Survey, written commun., 2004). The seismicrefraction data is based on measured travel times of artificially 

generated waves of elastic energy. The waves of elastic energy 

refract according to Snell's Law whenever they encounter a 

contrast in properties within the subsurface, such as a contrast 

between unconsolidated deposits and bedrock (Telford and 

others, 1976, p. 245). For the method to work, each successively 

deeper refractor must have a higher seismic velocity along with 

a considerable velocity contrast.

Travel times of the refracted elastic energy waves are 

measured by an array of geophones. The travel times are plotted 

against distance from the surface shock point along the line 

(profile) of geophones (for example, see fig. 9A). The inverse 

slope of the time-distance curve is equal to the apparent velocity 

of a corresponding refracting interface in the subsurface. 

Travel-time estimates are collected from the surface shock 

points at either end of the seismic profile to correct for dipping 

interfaces and to compute a true seismic velocity. The seismic 

profile was 473 ft long and consisted of two seismic lines of 

12 geophones spaced 20 ft apart. Because of the shallow depth 

to saturated deposits (water table was less than 3 ft below land 

surface in September 2001) relative to the spacing of the 

geophones (20-ft spacing), an accurate estimate of the depth 

to saturated deposits along the transect could not be made. 

The velocity of the unsaturated deposits ranged from 1,700 to 

3,100 ft/s (fig. 9A) and averaged 2,300 ft/s. The velocity of the 

saturated deposits ranged from 4,800 to 5,800 ft/s (fig. 9A) and 

averaged 5,500 ft/s. The velocity of the buried granitic bedrock 

(granodiorite) ranged from 10,700 to 14,700 ft/s (fig. 9A) and 

averaged 12,700 ft/s.

The seismic-refraction data were interpreted by an 

inversion algorithm that used the delay-time method 

(Barthelmes, 1946; Pakiser and Black, 1957) to obtain a 

first-approximation depth model, then these approximations 

were enhanced by a series of ray-tracing iterations (Scott, 

1993). The result is the estimated profile of the contact between 

the unconsolidated deposits and the buried granitic bedrock 

(fig. 9B). The estimated altitude of the bedrock just west of the 

planned detention basin was about 6,200 ft (south end of profile), which means that the thickness of unconsolidated deposits 

is about 80 ft. The bedrock surface rises to the north where the 

altitude of the bedrock is about 6,220 ft and there, the depth to 

bedrock is about 60 ft. 

Pioneer Trail

Sand and gravel

Organic silt and sand

Fill

6,290

6,300

6,280

6,270

6,260

Cold Creek

cc13S and cc 13D

cc14

cc8S and cc8D

cc3S and cc3D

ALTITUDE, IN FEET ABOVE SEA LEVEL

Water table, May 2001

0 50 100 150 FEET

0 10 20 30 METERS

Figure 8. Distribution of shallow unconsolidated deposits beneath Cattlemans detention basin prior to its construction. 
16 Chemistry of Runoff and Shallow Ground Water at the Cattlemans Detention Basin Site, South Lake Tahoe, California

The depth to bedrock decreases eastward because granodiorite is exposed at the surface east of Pioneer Trail and the 

area is mapped as bedrock (fig. 1). Bedrock (granodiorite) may 

have been encountered in well cc2 at a depth of 6.8 ft below 

land surface. This well is east of Pioneer Trail and near the base 

of the hill slope (fig. 4). 

Direction of Ground-Water Flow

Ground-water flow generally is from areas of higher 

ground-water levels to areas of lower ground-water levels. 

Prior to construction of the detention basin, the ground-water 

levels were highest east of Pioneer Trail and decreased westward following the slope of the meadow (fig. 10). On the basis 

of ground-water level contours, ground water beneath the 

planned detention basin was flowing toward two meanders on 

Cold Creek that trend perpendicular to the direction of groundwater flow. Although ground-water levels were higher in the 

spring and lower in the fall and winter, the general pattern of 

higher ground-water levels east of Pioneer Trail and lower 

ground-water levels west of the planned detention basin 

remained persistent throughout the year indicating the direction 

of flow also did not change. 

Seasonal Trends in Ground-Water Levels

Ground-water levels increased rapidly at wells cc3S and 

cc13S beginning March 5, 2001 (fig. 11). The response at wells 

cc8S and cc8D were much less on March 5 in relation to the 

rapid increase on March 16, 2001. The rapid rise on March 5, 

2001, correlates to precipitation that likely was in the form of 

rain (fig. 11C; minimum temperature was near freezing and 

maximum temperature was above freezing). The absence of a 

water-level rise in February was because much of the precipitation was in the form of snow (fig. 11C; precipitation occurred 

on days when temperatures were generally below freezing). The 

delayed response at wells cc8S and cc8D could have been due 

to the wells being in the center of the area covered by fill. 

Water levels in wells with recording pressure transducers 

peaked on March 21, 2001, declined through early April, and 

then increased again following snowstorms on April 6 and 7 

(figs. 11C). Water levels reached a second peak on April 23, 

2001, that followed 4 days of rain and snow from April 18-21, 

2001 (fig. 11C) before slowly declining until September 2001. 

The increase in water levels at the end of August 2001 was 

not related to precipitation; however, the rapid increase on 

September 25, 2001, corresponds to rain on the same day. 

0

10

20

30

40

50

60

2,000 ft/s

10,700 ft/s

5,600 ft/s

3,100 ft/s

5,600 ft/s

14,700 ft/s

2,400 ft/s

5,800 ft/s

4,800 ft/s

1,700 ft/s

TIME, IN MILLISECONDS

A

6,100

6,150

6,200

6,250

6,300

0 50 100 150 200 250 300 350 400 450 500

ALTITUDE, IN FEET ABOVE SEA LEVEL

 Unsaturated basin-fill deposits (average velocity 2,300 ft/s)

 Saturated basin-fill deposits (average velocity 5,500 ft/s)

 Granitic bedrock (average velocity 12,700 ft/s)

?

?

?

A'

DISTANCE ALONG SECTION, IN FEET

Land surface

Figure 9. Time-distance curves and velocity-depth profile for seismic-refraction line A–A' near Cattlemans detention basin. 

Location of line is shown on figure 2. Units are in feet per second (ft/s).
Ground Water 17

0 50 METERS

0 200 FEET

24

Cattlemans Court

Gate

Road

slope

Pioneer Trail

Shallow monitoring well (D indicates an adjacent deep well)—Large number is local

 well number; smaller number is water-level altitude when added to 6,200 feet

Surface-water level recorder

Ground-water level recorder

EXPLANATION

Water level contour—Contour interval is 0.5 feet from 6,269 feet to 6,274 feet above 

 mean sea level. Ground-water level contours for May 9, 2001

68.8

68.8

68.8

69.0

70.0

70.6

69.4

69.6

76.1

76.3

73.0

72.2

72.1

72.8 73.8

72.0

71.9

71.6

71.0

70.2

71.6

70.5

70.7

71.4

69.3

NORTH

Base from Tahoe Engineering Division, El Dorado County Department of Transportation, Nov. 2000

6273

6269

6270

6271

6272

6274

6269

Cold Creek

D

D

D

D

1

2

4

D

3

5

6

7

8

9

10

11

12

14

15

D

16 17

18

19

20

21

22 23

24

13

Biolog 

The greatest rise in water level was observed at well cc3S, 

which rose 2.3 ft between January 30 and March 21, whereas 

the water level rose only 0.2 ft during the same period at well 

cc14 next to Cold Creek. The observed trends in water levels in 

the area of the detention basin prior to its construction are consistent with subsurface flow from the upland areas to the east 

and south, and recharge from infiltration of precipitation (rain 

and snowmelt) and urban runoff in the study area. The groundwater levels rose throughout the study area between January 

and May 2001 as indicated from periodic measurements in all 

the wells and declined during the summer (fig. 12). Again, the 

trends are consistent with recharge during the spring, and discharge of ground water to Cold Creek as well as discharge by 

evapotranspiration in the meadow during the summer. 

Differences in ground-water levels between the paired 

shallow and deep wells (figs. 11 and 12) indicate that ground 

water was moving upward from the deeper sand and gravel into 

the meadow deposits at the middle part of the detention basin 

prior to construction (wells cc8S, and cc8D; fig. 11A). The 

ground-water level in wells cc3D and cc6D also were slightly 

higher than the ground-water levels in wells cc3S and cc6S, 

although differences were slight. In contrast, a component of 

water in the meadow deposits was contributing water to the 

deeper deposits at the lower end (wells cc13S and cc13D in 

fig. 11B). The change from an upward gradient at well cc8S to 

a downward gradient at well cc13S suggests the unconsolidated 

deposits thicken rapidly between the two wells.

The stage of Cold Creek next to well cc14 was monitored 

with a pressure transducer beginning June 13, 2001. The rapid 

response between stage and ground-water levels in well cc14 

indicates that the shallow ground water and the creek are 

hydraulically connected (fig. 13). The stage was slightly less 

than that in well cc14 with the greatest difference in June. Water 

levels slowly converged until August when they were nearly the 

same (within 0.02 ft). Plywood was placed across the culvert on 

the upstream side of Pioneer Trail by neighborhood youths to 

create a pond. This decreased the stage of Cold Creek downstream of the culvert and in well cc14 and increased water levels 

in wells cc1, cc2, and cc4 (well cc5 showed only a slight rise) 

in August 2001 (fig. 12). The observed rise in these wells while 

Cold Creek was dammed at the culvert indicates that groundwater levels beneath the detention basin are sensitive to changes 

in water levels in Cold Creek above Pioneer Trail. The plywood 

was removed on September 25; the same day that 0.3 in. of precipitation was recorded at a nearby weather station (fig. 11C).

Figure 10. Ground-water level contours for May 2001 in the area of Cattlemans detention basin prior to its construction. 

Well name listed in table 1 has been abbreviated by omitting the “cc” designation.
18 Chemistry of Runoff and Shallow Ground Water at the Cattlemans Detention Basin Site, South Lake Tahoe, California

Figure 11. Trends of ground-water levels in wells with recording pressure transducers in 

the area of Cattlemans detention basin prior to and during its construction in relation to

precipitation and air temperature, January through September 2001: (A) wells cc3S, cc3D, 

cc8S, cc8D; (B) wells cc13S, cc13D, and cc14; and (C) cumulative precipitation and daily 

minimum and maximum temperature from weather station at the nearby elementary school. 

Location of wells is shown in figure 4, and location of weather station is shown in figure 5. 

6,270

6,271

6,272

6,273

6,274

6,275

Jan 1 Jan 31 Mar 2 Apr 1 May 1 May 31 June 30 July 30 Aug 29 Sept 28

WATER-LEVEL ALTITUDE, IN FEET ABOVE SEA LEVEL

cc3S

cc3D cc3D

cc8D

cc8S

6,269

6,270

6,271

6,272

6,273

6,274

2001

cc13S

cc13D

cc14

cc13D

Periodic measurements

Pressure-transducer data

A

B

C

Daily minimum temperature

Daily maximum temperature

Cumulative precipitation

0

30

60

90

DAILY TEMPERATURE,

IN DEGREES FAHRENHEIT

0

3

6

9

CUMULATIVE PRECIPITATION, IN INCHES
Ground Water 19

Figure 12. Trends of ground-water levels from periodic measurements in wells 

without recording pressure transducers in the area of Cattlemans detention 

basin prior to and during its construction, December 2000 through October 2001: 

(A) wells east of detention basin; (B) wells north of detention basin; (C) wells 

south and west of detention basin; (D) wells in meadow near west edge of study 

area. Location of wells is shown in figure 4. 

2001

cc19S

cc19D

2000

cc20

cc22

cc24

cc21

cc23

Water levels in meadow near west edge of study area

Nov 30 Dec 30 Jan 29 Feb 28 Mar 30 Apr 29 May 29 June 28 July 28 Aug 27 Sept 26 Oct 26

6,267

6,268

6,269

6,270

6,271

cc9

cc15

cc16

cc17S

cc17D

cc18

C Water levels in wells south and west of detention basin

D

6,269

6,270

6,271

6,272

6,273

WATER-LEVEL ALTITUDE, IN FEET ABOVE SEA LEVEL

cc5

cc6S

cc6D

cc10

cc7

cc11

cc12

B Water levels in wells north of detention basin

6,270

6,271

6,272

6,273

6,274

cc4

cc1

cc2

A Water levels in wells east of detention basin 

6,273

6,274

6,275

6,276

6,277
20 Chemistry of Runoff and Shallow Ground Water at the Cattlemans Detention Basin Site, South Lake Tahoe, California

6,269.4

6,269.6

6,269.8

6,270.0

6,270.2

6,270.4

June 10 June 20 June 30 July 10 July 20 July 30 Aug 9 Aug 19 Aug 29 Sept 8 Sept 18 Sept 28

WATER-LEVEL ALTITUDE, IN FEET ABOVE SEA LEVEL

2001

cc14

Cold Creek

Plywood placed across culvert on

upstream side of Pioneer Trail

Plywood removed from culvert

and precipitation occurred

Quality of Ground Water, Cold Creek, and Precipitation

The quality of ground water in the area of the detention 

basin prior to its construction was mostly dependent on the 

quality of water from the different sources (precipitation, urban 

runoff from Pioneer Trail, Montgomery Estates, and Cattlemans Court, inflow from upland areas, and seepage from Cold 

Creek), the chemical and biological reactions that occurred 

within the unconsolidated deposits through which ground water 

flowed, and the residence time of water in the deposits. The 

detention basin was constructed at the base of the upland area 

adjacent to the upper edge of a large meadow. The water table 

beneath the area of the detention basin prior to and during its 

construction was primarily in the gray silt and sand of the 

meadow deposits; consequently, lateral ground-water flow 

from the area of the planned detention basin to nearby Cold 

Creek was primarily through the meadow deposits. 

Chemical Composition

Dissolved calcium, sodium, and bicarbonate in Cold Creek 

were about 12 times more than the snow, whereas chloride concentrations were nearly the same (table 3). Greater concentrations of dissolved constituents in Cold Creek compared with 

ephemeral springs is attributed to the dissolution of minerals as 

water moves through the shallow soil and saprolite (Feth and 

others, 1964, p. 35). The ephemeral and perennial springs listed 

in table 3 are from areas of granitic rocks in the Sierra Nevada, 

some of which are springs that were sampled in the upland areas 

south of South Lake Tahoe (Feth and others, 1964, table 1). A 

summary of the chemistry of these springs is listed in table 3 

(Feth and others, 1964, table 2). The lack of an increase in chloride concentrations in Cold Creek compared with ephemeral 

springs and precipitation suggests rapid infiltration of precipitation and minimal evaporation prior to reaching Cold Creek. 

Like precipitation, water from ephemeral and perennial springs 

and Cold Creek is a calcium, sodium bicarbonate type. This 

suggests that granitic rocks in the Cold Creek drainage are the 

principal source of dissolved constituents in water from the 

creek.

Ground water in meadow deposits within the study area 

had higher concentrations of most constituents than either snow 

or water in Cold Creek (table 3); a notable exception is sulfate. 

Total dissolved solids in the ground water were 34 times more 

than snow and about 4 times more than the water in Cold Creek. 

Total dissolved solids in Cold Creek on September 11, 2001, 

were 10 times more than that of snow and were similar to that 

from ephemeral and perennial springs. 

The mean silica concentration in ground water was more 

than 100 times greater than the mean silica concentration in 

snow. Some of the greatly increased dissolved silica in water 

pumped from the wells could be caused by dissolution of the silica flour and quartz sand used in well construction; however, 

Figure 13. Relation between stage of Cold Creek and ground-water level at well cc14 on west side of Cattlemans detention basin prior 

to and during its construction, June through September 2001.
Ground Water 21

dissolved silica concentrations in ground water were similar to 

concentrations in Cold Creek and ephemeral and perennial 

springs (table 3). Thus, the dissolved silica concentration in 

water from the shallow wells likely is caused by dissolution of 

the abundant silica naturally present in minerals in the unconsolidated deposits. 

In contrast to water in Cold Creek and water from ephemeral and perennial springs, ground water in the meadow deposits 

had higher concentrations of iron, sodium, chloride, and bicarbonate, and lower concentrations of sulfate (table 3). Dissolved 

nitrate plus nitrite in ground water was similar to dissolved 

nitrate from the perennial springs (Feth and others, 1964), indicating that dissolved nitrate in ground water occurs naturally. 

The dissolved iron concentrations in the meadow deposits were 

about 500 times greater and chloride was more than 30 times 

greater than dissolved concentrations in Cold Creek or water 

from the ephemeral and perennial springs. The median and 

mean sulfate concentrations in the meadow deposits were 

0.4 mg/L (table 3) and dissolved oxygen was near the detection 

limit (<0.3 mg/L; see table 6). The low dissolved oxygen concentrations indicate that shallow ground water in the meadow 

is largely anoxic. The lack of oxygen is likely the result of 

microbial oxidation of organic matter in the meadow deposits. 

The anoxic conditions allow for iron and manganese to be dissolved at higher concentrations than oxygenated ground water. 

Dissolved chloride concentrations in ground water from 

the meadow deposits and deeper sand and gravel correlate well 

to total dissolved solids, whereas bromide concentrations 

(although much lower) show no relation (fig. 14). These two 

anions have similar sources and both have similar geochemical 

behavior. Because bromide does not show a correlation to total 

dissolved solids, the increase in chloride cannot be explained by 

concentration resulting from evapotranspiration of ground 

water. The chloride in the ground water probably was from a 

source other than the unconsolidated deposits. One likely 

source of chloride and sodium is from the application of a mixture of road cinders and salt (sodium chloride) at proportions of 

1 part salt to 4 parts cinders along Pioneer Trail and streets in 

Montgomery Estates subdivision during the winter (Jennifer 

Quickel, Tahoe Engineering Division, El Dorado County 

Department of Transportation, written commun., 2003).

Table 3. Median and mean concentrations of dissolved constituents in ground water and in Cold Creek in the 

area of Cattlemans detention basin prior to and during its construction, South Lake Tahoe, California, and in 

perennial and ephemeral springs in granitic rocks and snow in the Sierra Nevada

[Values are reported to two significant figures unless reported by laboratory to one significant figure. Symbol: --, not determined]

Constituent

Concentrations in milligrams per liter

Ground water

1Median and mean concentrations are from ground water in the meadow deposits of gray silt and sand (see table 4). Nitrate 

concentrations listed in this table were converted from nitrate plus nitrite concentrations listed as nitrogen in table 6. Location of 

wells is shown in figure 4.

1

Silica (SiO2)

Iron (Fe)

Calcium (Ca)

Magnesium (Mg)

Sodium (Na)

18

15

10

1.6

25

18

19

14

2.3

22

22

.01

10

1.0

5.5

25

.03

10

1.7

6.0

13

.02

2.6

.5

2.7

16

.03

3.1

.70

3.0

16

.04

5.5

.62

5.0

0.16

--

.4

.17

.46

Potassium (K)

Bicarbonate (HCO3)

Sulfate (SO4)

Chloride (Cl)

Nitrate (NO3)

Dissolved solids

2.0

100

.40

31

.24

130

2.5

120

.38

31

.33

160

1.4

51

1.6

.45

.1

72

1.6

55

2.4

1.1

.28

75

1.0

14

.6

.2

.0

29

1.1

20

1.0

.50

.02

36

.90

30

2.2

.52

--

45

.32

2.9

.95

.50

.07

4.7

Perennial 

springs2

2

Median and mean concentrations are from perennial and ephemeral springs that discharge from granitic rocks in the Sierra 

Nevada (Feth and others, 1964, table 2). Ground water from the upland areas is assumed to have similar concentrations as the 

perennial springs because granitic rocks underlie the upland areas east of the detention basin.

Ephemeral 

springs2

Cold

Creek3

3Mean concentration in water sampled from Cold Creek. Mean is based on two samples collected on September 11, 2001: one 

upstream of Pioneer Trail near well cc1; and one near well cc14 (see fig. 4 for location of wells). Bicarbonate concentration was 

estimated from the difference in sum of cations and anions.

Snow4

4Mean concentration in water from snow collected in the Sierra Nevada (Feth and others, 1964, table 3).

Median Mean Median Mean Median Mean Mean Mean
22 Chemistry of Runoff and Shallow Ground Water at the Cattlemans Detention Basin Site, South Lake Tahoe, California

The chemical composition of water in shallow meadow 

deposits was similar to the chemical composition of water in 

the deeper brown sand and gravel. Exceptions include sulfate 

concentrations, which were generally higher, and dissolved iron 

and organic carbon, which were about 2 times less (table 4). 

The range in dissolved concentrations of most constituents 

generally was greater in the meadow deposits than in the deeper 

sand and gravel. Iron concentrations in the meadow deposits 

ranged from 0.66 to 60 mg/L, whereas concentrations in the 

deeper sand and gravel ranged from 0.035 to 19 mg/L (table 4). 

Similarly, dissolved organic carbon ranged from 2.5 to 

14 mg/L in the meadow deposits, and from 1.2 to 5.8 mg/L 

in the sand and gravel (table 4). The greater dissolved organic 

carbon in ground water from meadow deposits likely was 

caused by the greater availability of organic material in the 

meadow deposits. 

Except for aluminum, barium, manganese, molybdenum, 

and uranium, concentrations of most dissolved trace elements in 

ground water were less than 2 μg/L (table 5). Similar to iron, 

concentrations of manganese and aluminum were lower in 

ground water from the deeper sands and gravels compared with 

ground water from the shallow meadow deposits. 

Distribution of Total Dissolved Solids, Chloride, and Iron

Concentrations of total dissolved solids, chloride, and 

iron for April-May 2001, shortly after peak ground-water 

levels, were used to illustrate areal distributions of dissolved 

constituents within the meadow deposits. The highest measured 

dissolved solids concentration of 339 mg/L was at well cc21 

(fig. 15A). In the area of the planned detention basin, concentrations of dissolved solids were higher at wells cc3S and cc8S 

than at wells closer to Cold Creek (wells cc10, cc11, cc12, 

cc13S, and cc14) or from well cc9 at the end of Cattlemans 

Court. Chloride concentrations also were highest at well cc21 

and were nearly the same in wells cc3S, cc9, cc15, and cc14 

(fig. 15B). The nearly uniform chloride concentrations in the 

vicinity of the planned detention basin suggest that chloride 

is well dispersed in the shallow meadow deposits. Chloride 

concentrations were least in wells cc11 and cc12 and could 

result from mixing with the more dilute water in Cold Creek. 

Dissolved iron was analyzed as part of the nutrient analyses, consequently more wells were sampled for dissolved iron 

than for total dissolved solids and chloride (fig. 15C). The distribution of iron shows a similar pattern—highest concentration 

of iron was measured in well cc21 and the lowest was next to 

Cold Creek at well cc7. The low dissolved iron concentration in 

Figure 14. Relation between total dissolved solids and dissolved chloride and bromide in ground water in the area of Cattlemans

detention basin prior to and during its construction, January to November 2001.

Bromide = -0.0005(TDS)+ 0.23

r

2

 = 0.015

Chloride= 0.36(TDS)- 19.07

r

2

 = 0.76

0

20

40

60

80

100

120

140

0 50 100 150 200 250 300 350 400

TOTAL DISSOLVED SOLIDS, IN MILLIGRAMS PER LITER

CHLORIDE CONCENTRATION, IN MILLIGRAMS PER LITER

0

0.2

0.4

0.6

0.8

1

1.2

1.4

BROMIDE CONCENTRATION, IN MILLIGRAMS PER LITER

Chloride

Bromide
Ground Water 23

well cc7 supports water-level measurements that indicate Cold 

Creek was supplying water to the meadow deposits at or near 

the well (fig. 10). Dissolved iron concentrations in wells next 

to Cold Creek were highest at well cc14, which is consistent 

with water-level measurements that indicate ground water is 

discharging to Cold Creek near the well.

Concentrations of dissolved constituents also differed 

between ground water in the shallow meadow deposits and in 

the deeper sand and gravel (fig. 16). Total dissolved solids were 

lower in the deeper wells cc3D and cc8D when compared with 

total dissolved solids in wells cc3S and cc8S, whereas total dissolved solids in well cc13D were higher than in well cc13S 

(fig. 16A). Total dissolved solids in well cc14 are higher than in 

well cc13S suggesting that dissolved solids near the water table 

could be higher than that measured at well cc13S. Chloride concentrations were consistently higher in the deeper sand and 

gravel than in the shallow meadow deposits (fig. 16B). Chloride 

was highest in well cc3D next to Pioneer Trail suggesting that 

the application of salt mixed with cinders was contributing 

chloride to the deeper sand and gravel. Iron concentrations in 

the deeper sand and gravel were low at well cc3D and highest 

in the shallow meadow deposits at well cc8S (fig. 16C). Similar 

to total dissolved solids, iron concentration in well cc14 

was higher than in well cc13S. This suggests that dissolved 

constituents vary considerably in the meadow deposits

depending on organic content, and chemical and biological 

reactions.

Distribution of Nutrients and Organic Carbon

Concentrations of the different forms of dissolved nitrogen 

and phosphorus, and concentrations of dissolved iron, and 

organic carbon were generally higher in the meadow deposits 

than in the deeper sand and gravel (table 6). Ammonia plus 

organic nitrogen were the dominant forms of nitrogen and had 

a maximum concentration of 18 mg/L. Median concentrations 

of dissolved nitrogen, phosphorus, and organic carbon in the 

meadow deposits were higher than those in the deeper sand 

and gravel. 

Table 4. Concentrations of principal dissolved inorganic constituents and dissolved organic carbon in ground water in 

the area of Cattlemans detention basin prior to and during its construction, South Lake Tahoe, California, January to 

November 2001

[Abbreviation: microsiemens per centimeter, μS/cm. Values are reported to two significant figures unless reported by laboratory to one significant 

figure.]

Constituent

Ground water in meadow deposits

1

Water was sampled from shallow wells between January and November 2001. Values are based on 34 samples collected from wells 3S, 8S, 9, 

10, 11, 12, 13S, 14, 15, and 21, except dissolved iron, which is based on 70 samples collected from wells 1, 2, 3S, 6S, 7, 8S, 9, 10, 11, 12, 13S, 14,

15, 16, 17S, 18, 19S, 20, 21, 22, 23, and 24. Well name has been abbreviated by omitting the “cc” designation. Shallow wells are screened in meadow deposits of gray silt and sand with lenses of sand and gravel. Location of wells is shown in figure 4. 

1

(concentrations in milligrams per liter, 

except as noted)

Silica (SiO2)

Iron (Fe)

Calcium (Ca)

Magnesium (Mg)

Sodium (Na)

12

0.66

4.5

.68

6.7

18

15

10

1.6

25

28

60

32

5.3

43

18

19

14

2.3

22

15

0.035

5.6

.82

15

22

5.9

11

1.9

26

26

19

20

3.2

63

20

8.3

11

1.9

31

Potassium (K)

Bicarbonate (HCO3)

Sulfate (SO4)

Chloride (Cl)

Bromide (Br)

.67

46

.1

3.0

<.02

2.0

100

.4

31

.12

7.6

270

.8

104

1.2

2.5

120

.38

31

.19

1.2

60

.3

5.5

<.02

1.7

73

1.1

33

.06

2.2

99

3.4

96

.34

1.7

77

1.4

40

.1

Fluoride (F)

Organic carbon (DOC)

pH (standard units)

Specific conductance (μS/cm)

Dissolved solids

<.2

2.5

5.8

84

61

<.2

5.2

6.5

260

130

<.2

14

6.9

550

340

<.2

5.5

6.5

280

160

<.2

1.2

6.2

160

82

<.2

2.0

6.5

260

150

<.2

5.8

6.8

350

240

<.2

2.2

6.5

270

150

Deeper ground water in sand and gravel2

(concentrations in milligrams per liter, 

except as noted)

2

Water was sampled from deeper wells between January and November 2001. Values are based on 12 samples from wells 3D, 8D, and 13D 

except for dissolved iron, which is based on 21 samples collected from wells 3D, 6D, 8D, 13D, 17D, and 19D. Well name has been abbreviated by 

omitting the “cc” designation. Deeper wells are screened in the brown to yellow brown sand and gravel with lenses of silt and sand. Location of 

wells is shown in figure 4. 

Minimum Median Maximum Mean Minimum Median Maximum Mean
24 Chemistry of Runoff and Shallow Ground Water at the Cattlemans Detention Basin Site, South Lake Tahoe, California

Concentrations of dissolved ammonia plus organic nitrogen, phosphorus, and organic carbon for samples collected in 

late April and early May 2001, shortly after peak ground-water 

levels, from ground water in the meadow deposits do not show 

any consistent areal patterns (fig. 17). This suggests that variations in concentration likely are controlled by variations in the 

chemical and biological reactions within the meadow deposits. 

Ammonia plus organic nitrogen ranged from 0.07 mg/L at well 

cc7 next to Cold Creek to 16 mg/L as well cc8S in the middle 

of the detention basin site (fig. 17A). With the exception of three 

wells, ammonia plus organic nitrogen concentrations were less 

than 2 mg/L. Dissolved phosphorus was more uniform with 

concentrations ranging from 0.04 to 0.32 mg/L (fig. 17B). 

Dissolved organic carbon concentrations ranged from 3.2 to 

7.7 mg/L (fig. 17C). 

Ammonia plus organic nitrogen, phosphorus, and organic 

carbon concentrations were consistently less in the deeper sand 

and gravel than in the meadow deposits (fig. 18). Ammonia plus 

organic nitrogen and dissolved organic carbon show no consistent change in the direction of ground-water flow again suggesting that local variations in the chemical and biological reactions 

within the meadow deposits are controlling the variation in 

nitrogen concentrations; however, dissolved phosphorus 

increased in both the meadow deposits and in the deeper sand 

and gravel along the direction of ground-water flow. This 

suggests that phosphorus concentrations in ground water 

may be controlled by the dissolution of phosphorus-containing 

minerals in the unconsolidated deposits. 

The two highest concentrations of dissolved organic 

carbon in ground water from the meadow deposits were from 

wells cc3S and cc8S and are coincident with the highest concentrations of total dissolved nitrogen (sum of all nitrogen 

compounds, fig. 19). These wells are located in an area where 

thick fill was placed over the meadow deposits. Ground water 

from wells near the edge of the fill (wells cc9, cc10, cc13S, and 

cc15), and from wells along Cold Creek and in the meadow 

west of the planned detention basin (wells cc11, cc12, cc14, and 

cc21) also suggest that total dissolved nitrogen may be correlated to dissolved organic carbon but the increase in total dissolved nitrogen compared with the increase in dissolved 

organic carbon is much less than that at wells cc3S and cc8S. 

The correlation between dissolved nitrogen and dissolved 

organic carbon in the meadow deposits may be nonlinear as 

suggested by the data shown on figure 19. The higher dissolved 

nitrogen and organic carbon at well cc8S could be from the 

decomposition of vegetation buried by the fill.

Table 5. Concentrations of dissolved inorganic trace elements in ground water in the area of Cattlemans detention 

basin prior to and after its construction, South Lake Tahoe, California, January to November 2001

[Values are reported to two significant figures unless reported by laboratory to one significant figure.]

Constituent

Ground water in meadow deposits

1

Water was sampled from shallow wells between January and November 2001. Values are based on 34 samples collected from wells 

cc3S, cc8S, cc9, cc10, cc11, cc12, cc13S, cc14, cc15, and cc21. Shallow wells are screened in meadow deposits of gray silt and sand 

with lenses of sand and gravel. Location of wells is shown in figure 4.

1

(concentrations in micrograms per liter)

Aluminum (Al)

Antimony (Sb)

Arsenic (As)

Barium (Ba)

Beryllium (Be)

4

<0.05

<2

6.1

<.06

10

<0.05

<2

22

<.06

65

<0.05

5

100

<.06

21

<0.05

<2

33

<.06

1

<0.05

<2

8.2

<.06

2

<0.05

<2

20

<.06

6

0.09

2.6

77

<.06

2.5

<0.05

<2

27

<.06

Cadmium (Cd)

Chromium (Cr)

Cobalt (Co)

Copper (Cu)

Lead (Pb)

<.04

<.8

.04

<.6

<.08

<.04

<.8

.82

<.6

<.08

.14

1.7

3.3

<.6

.44

.05

<.8

.94

<.6

.09

<.04

<.8

.5

<.6

<.08

<.04

<.8

.66

<.6

<.08

.12

<.8

1.5

<.6

<.08

.05

<.8

.83

<.6

<.08

Manganese (Mn)

Molybdenum (Mo)

Nickel (Ni)

Selenium (Se)

Silver (Ag)

59

1.7

<.06

<2.4

<1

230

6.0

<.06

<2.4

<1

1,500

39

.49

<2.4

<1

390

8.5

.15

<2.4

<1

38

1.9

<.06

<2.4

<1

130

11

<.06

<2.4

<1

280

24

.35

<2.4

<1

130

11

.11

<2.4

<1

Uranium (U) 

Zinc (Zn)

.7

<2

2.1

<2

30

<2

4.4

<2

1.8

<1

3.7

<1

11

<1

4.4

<1

Deeper ground water in sand and gravel2

(concentrations in micrograms per liter)

2

Water was sampled from deeper wells between January and November 2001. Values are based on 12 samples from wells cc3D, 

cc8D, and cc13D. Deeper wells are screened in the brown to yellow brown sand and gravel with lenses of silt and sand. Location of 

wells is shown in figure 4.

Minimum Median Maximum Mean Minimum Median Maximum Mean
Ground Water 25

0 50 METERS

0 200 FEET

Cold Creek

Biolog 

D

D

D

D

1

2

4

D

3

5

6

7

8

9

10

11

12

13

14

15

D

16 17

18

19

20

21

22 23

24

Spillway

Cattlemans Court

Gate

Road

slope

Pioneer Trail

Surface-water level recorder

Surface-water flow direction

Ground-water level recorder

Stormwater drain

EXPLANATION

NORTH

Base from Tahoe Engineering Division, El Dorado County Department of Transportation, Nov. 2000

A Total Dissolved Solids, late April–May 2001

182 127

132

166 274

139

231

110

339

113

182 127

132

274

139

110

339

113

339 Total dissolved solids—In milligrams per liter 

24 Shallow monitoring well and well number 

 (D indicates an adjacent deep well)

Figure 15. Distribution of (A) total dissolved solids, (B) dissolved chloride, and (C) dissolved iron concentrations in 

ground water from meadow deposits in the area of Cattlemans detention basin prior to its construction, late April 

and May 2001. Well name listed in table 1 has been abbreviated by omitting the “cc” designation.
26 Chemistry of Runoff and Shallow Ground Water at the Cattlemans Detention Basin Site, South Lake Tahoe, California

0 50 METERS

0 200 FEET

Cold Creek

Biolog 

D

D

D

D

1

2

4

D

3

5

6

7

8

9

10

11

12

13

14

15

D

16 17

18

19

20

21

22 23

24

Spillway 

Cattlemans Court

Gate

Road

slope

Pioneer 

Trail

Surface-water level recorder

Surface-water flow direction

Ground-water level recorder

Stormwater drain

EXPLANATION

NORTH

Base from Tahoe Engineering Division, El Dorado County Department of Transportation, Nov. 2000

B Dissolved chloride, late April–May 2001

36 27

22

39 29

35

38

10

104

15

36 27

22

39

29

35

38

10

104

15

104 Dissolved chloride—In milligrams per liter 

24 Shallow monitoring well and well number 

 (D indicates an adjacent deep well)

Figure 15.—Continued.
Ground Water 27

C Dissolved iron, late April–May 2001

0 50 METERS

0 200 FEET

Cold Creek

Biolog 

D

D

D

D

1

2

4

D

3

5

6

7

8

9

10

11

12

13

14

15

D

16 17

18

19

20

21

22 23

24

Spillway 

Cattlemans Court

Gate

Road

slope

Pioneer 

Trail

Surface-water level recorder

Surface-water flow direction

Ground-water level recorder

Stormwater drain 

EXPLANATION

NORTH

Base from Tahoe Engineering Division, El Dorado County Department of Transportation, Nov. 2000

11

14

34

29 19

48

14

26

18

60

14 13

6

21

9

14

0.7

11

14

34

29 19

48

14

26

18

60

14

13

6

21

9

14

0.7

14 Dissolved iron—In milligrams per liter

24 Shallow monitoring well and well number 

 (D indicates an adjacent deep well)

Figure 15.—Continued.
28 Chemistry of Runoff and Shallow Ground Water at the Cattlemans Detention Basin Site, South Lake Tahoe, California

Pioneer Trail

Sand and gravel

Organic silt and sand

Fill

6,290

6,300

6,280

6,270

6,260

Cold Creek

cc13S and cc13D

cc14

cc8S and cc8D

cc3S and cc3D

cc13S and cc13D

cc14

cc8S and cc8D

cc3S and cc3D

cc13S and cc13D

cc14

cc8S and cc8D

cc3S and cc3D

Pioneer Trail

Sand and gravel

Organic silt and sand

Fill

6,290

6,300

6,280

6,270

6,260

Cold Creek

ALTITUDE, IN FEET ABOVE SEA LEVEL

Pioneer Trail

Sand and gravel

Organic silt and sand

Fill

6,290

6,300

6,280

6,270

6,260

Cold Creek

0 50 100 150 FEET

0 10 20 30 METERS

Water table

Water table

Water table

Direction of ground-water flow

C Dissolved iron, late April- May 2001

48

12

16

11 34

26

1

25 Dissolved iron, in milligrams per liter 

B Dissolved chloride, late April- May 2001

29

32

38

74

24

22 36

29 Dissolved chloride in milligrams per liter 

A Total dissolved solids, late April- May 2001

274

146

231

194

149

132 182

274 Total dissolved solids in milligrams per liter 

Figure 16. Vertical sections showing distribution of (A) total dissolved solids, (B) dissolved chloride, 

and (C) dissolved iron concentrations in ground water beneath Cattlemans detention basin prior to 

its construction, late April and May 2001.
Ground Water 29

Seasonal Variations

Concentrations of dissolved calcium, sodium, iron, bicarbonate, and chloride varied during the year among ground water 

in the meadow deposits from four wells sampled across the 

detention basin site (fig. 20). Changes in sodium, calcium, and 

iron concentrations were not consistent among the four wells. 

In general, sodium was the dominant cation in wells cc3S and 

cc13S; iron was the dominant cation at well cc8S; and iron was 

dominant during the winter and spring and sodium during 

the summer and fall at well cc14. Concentrations of sodium, 

calcium, and iron remained unchanged at well cc8S. Sodium 

concentrations varied the least at all four wells whereas calcium 

was most variable at well cc3S and iron was most variable at 

well cc14. Bicarbonate concentrations were nearly constant 

at wells cc8S and cc14, decreased slightly after the spring at 

well cc3S, and increased from winter to summer at well 

cc13S. Bicarbonate concentrations were highest at well cc8S 

(exceeded 260 mg/L) and lowest at well cc13S (ranged from 

65 to 100 mg/L). Chloride concentrations were nearly constant 

at wells cc3S and cc8S; generally followed the same trend as 

bicarbonate at well cc13S; and slowly decreased from spring to 

fall at well cc14. 

Concentrations of dissolved calcium, sodium, iron, bicarbonate, and chloride generally varied more during the year 

among ground water in the deeper sand and gravel sampled 

from three wells compared with ground water in the meadow 

deposits (fig. 21). Changes in sodium, calcium, and iron concentrations were not consistent among the three deeper wells 

and were not consistent with changes in the meadow deposits. 

Calcium, iron, and bicarbonate concentrations in the deeper 

sand and gravel at wells cc3D and cc8D were less than concentrations in adjacent wells in the meadow deposits (compare 

cc3D and cc8D in fig. 21 to cc3S and cc8S in fig. 20). Although 

changes in concentrations during the year were not the same for 

wells cc13D and cc13S, concentrations of calcium, sodium, 

iron, bicarbonate, and chloride were similar between ground 

water from the meadow deposits and the deeper sand and gravel 

(figs. 20C and 21C). Iron concentrations increased in the deeper 

sand and gravel along the general direction of ground-water 

flow. Variations of dissolved constituents among ground water 

in the meadow deposits and in the deeper sand and gravel and 

through time suggests that concentrations at any one well is 

affected by a variety of processes that include; subsurface flow 

from upland areas, recharge through the fill materials that overlie the meadow deposits, flow between the meadow deposits 

and deeper sand and gravel, and chemical and biological reactions within the unconsolidated deposits.

Concentrations of sodium and chloride in the deeper wells 

were much higher at well cc3D than at wells cc8D and cc13D. 

The water at well cc3D was dominated by sodium and chloride 

in May and July 2001. Because of the close proximity of well 

cc3D to Pioneer Trail and because the shallow meadow deposits 

do not extend into the upland area, the likely source of the 

sodium and chloride is the application of salt mixed with 

cinders during winter along surface roads. The peak in chloride 

concentrations lags a couple of months behind the peak in 

ground-water levels measured in well cc3D (see fig. 11). The 

later chloride peak may correspond to the time for chloride 

to travel from its source area along Pioneer Trail and the 

Montgomery Estates subdivision to well cc3D. 

Table 6. Concentrations of dissolved nutrients in ground water in vicinity of Cattlemans detention basin prior to and during its construction, South Lake Tahoe, California, January to November 2001

[Values are reported to two significant figures unless reported by laboratory to one significant figure.]

Nutrient

Ground water in meadow deposits

1

Water was sampled from shallow wells between January and November 2001. Values are based on 70 samples collected from wells 1, 2, 3S, 6S, 7, 8S, 9, 10, 

11, 12, 13S, 14, 15, 16, 17S, 18, 19S, 20, 21, 22, 23, and 24 except for organic carbon and dissolved oxygen which are based on 34 samples from wells 3S, 8S, 

10, 11, 12, 13S, 14, 15, and 21. Well name has been abbreviated by omitting the “cc” designation. Shallow wells are screened in meadow deposits of gray silt and 

sand with lenses of sand and gravel. Location of wells is shown in figure 4.

1

(concentrations in milligrams per liter)

Ammonia (NH3) as nitrogen (N)

Nitrate (NO3) + nitrite (NO2) as N

Ammonia (NH3) + organic nitrogen as N

Phosphorus (P)

0.004

.002

.040

.006

0.31

.054

.44

.10

18

0.33

18

.34

1.5

0.075

1.9

.12

0.014

.004

.015

.004

0.062

.043

.14

.025

0.64

.12

.64

.40

0.15

.047

.22

.056

Orthophosphorus, as P

Organic carbon (DOC)

Dissolved oxygen (DO)

.001

2.5

<.3

.02

5.2

<.3

.34

14

2.4

.069

5.5

.4

.001

1.2

<.3

.005

2.0

.4

.40

5.8

1.0

.039

2.2

.5

Deeper ground water in sand and gravel2

(concentrations in milligrams per liter)

2

Water was sampled from deeper wells between January and November 2001. Values are based on 21 samples collected from wells 3D, 6D, 8D, 13D, 17D, 

and 19D except organic carbon and dissolved oxygen, which are based on 34 samples from wells 3S, 8S, 10, 11, 12, 13S, 14, 15, and 21. Well name has been

abbreviated by omitting the “cc” designation. Deeper wells are screened in the brown to yellow-brown sand and gravel with lenses of finer-textured silt and sand. 

Location of wells is shown in figure 4.

Minimum Median Maximum Mean Minimum Median Maximum Mean
30 Chemistry of Runoff and Shallow Ground Water at the Cattlemans Detention Basin Site, South Lake Tahoe, California

0 50 METERS

0 200 FEET

Cold Creek

Biolog 

D

D

D

D

1

2

4

D

3

5

6

7

8

9

10

11

12

13

14

15

D

16 17

18

19

20

21

22 23

24

Spillway

Cattlemans Court

Gate

Road

slope

Pioneer 

Trail

Surface-water level recorder

Surface-water flow direction

Ground-water level recorder

Stormwater drain

EXPLANATION

NORTH

Base from Tahoe Engineering Division, El Dorado County Department of Transportation, Nov. 2000

A Ammonia plus organic nitrogen, late April–May 2001

0.63

1.4

2.4 1.3

0.42

16

2.8

0.86

1.2

0.16 0.13

0.14

0.46

0.07

0.36 0.15

Ammonia plus organic nitrogen as nitrogen—In

milligrams per liter 

1.4

0.63

1.4

2.4

1.3

0.42

16

2.8

0.86

1.2

0.16 0.13

0.14

0.46

0.07

0.36 0.15

1.4

2.4

24 Shallow monitoring well and well number 

 (D indicates an adjacent deep well)

Figure 17. Distribution of (A) dissolved ammonia plus organic nitrogen, (B) dissolved phosphorus, and (C) dissolved organic 

carbon concentrations in ground water from meadow deposits in the area of Cattlemans detention basin prior to its construction,

late April and May 2001. Well name listed in table 1 has been abbreviated by omitting the “cc” designation.
Ground Water 31

0 50 METERS

0 200 FEET

Cold Creek

Biolog 

D

D

D

D

1

2

4

D

3

5

6

7

8

9

10

11

12

13

14

15

D

16 17

18

19

20

21

22 23

24

Spillway

Cattlemans Court

Gate

Road

slope

Pioneer 

Trail

Surface-water level recorder

Surface-water flow direction

Ground-water level recorder

Stormwater drain

EXPLANATION

NORTH

Base from Tahoe Engineering Division, El Dorado County Department of Transportation, Nov. 2000

B Dissolved phosphorus, late April–May 2001

0.21

0.18

0.10

0.10

0.32

0.16

0.14

0.09

0.32

0.04 0.11 0.05

0.06

0.10

0.19

0.07 0.21

0.18

0.10

0.10

0.32

0.31

0.16

0.14

0.09

0.32

0.04 0.11 0.05

0.06

0.10

0.19

0.07

0.31 Dissolved phosphorus—In milligrams per liter 

24 Shallow monitoring well and well number 

 (D indicates an adjacent deep well)

Figure 17.—Continued
32 Chemistry of Runoff and Shallow Ground Water at the Cattlemans Detention Basin Site, South Lake Tahoe, California

0 50 METERS

0 200 FEET

Cold Creek

Biolog 

D

D

D

D

1

2

4

D

3

5

6

7

8

9

10

11

12

13

14

15

D

16 17

18

19

20

21

22 23

24

Spillway 

Cattlemans Court

Gate

Road

slope

Pioneer 

Trail

Surface-water level recorder

Surface-water flow direction

Ground-water level recorder

Stormwater drain

EXPLANATION

NORTH

Base from Tahoe Engineering Division, El Dorado County Department of Transportation, Nov. 2000

C Dissolved organic carbon, late April–May 2001

6.4

4.0

3.3

3.2

7.5

7.7

4.1

5.5

5.8

6.4

4.0

3.3

3.2

7.5

7.7

4.1

5.5

4.1

5.8

4.1 Dissolved organic carbon—In milligrams per liter

24 Shallow monitoring well and well number 

 (D indicates an adjacent deep well)

Figure 17.—Continued.
Ground Water 33

Pioneer Trail

Sand and gravel

Organic silt and sand

Fill

6,290

6,300

6,280

6,270

6,260

Cold Creek

Pioneer Trail

Sand and gravel

Organic silt and sand

Fill

6,290

6,300

6,280

6,270

6,260

Cold Creek

ALTITUDE, IN FEET ABOVE SEA LEVEL

Pioneer Trail

Sand and gravel

Organic silt and sand

Fill

6,290

6,300

6,280

6,270

6,260

Cold Creek

Water table

Water table

Water table

Direction of ground-water flow

C Dissolved organic carbon, late April-May 2001

7.5

2.4

7.7

3.5

2.1

4.0 6.4

7.7 Dissolved organic carbon, in milligrams per liter 

B Dissolved phosphorus, late April-May 2001

0.14

0.04

0.09

0.01

0.14

0.32 0.18

0.09 Dissolved phosphorus, in milligrams per liter 

A Ammonia plus organic nitrogen, late April-May 2001

16

0.09

2.8

0.15

0.64

1.2 0.86

2.8 Ammonia plus organic nitrogen as nitrogen, in milligrams per liter 

0 50 100 150 FEET

0 10 20 30 METERS

cc13S and cc13D

cc14

cc8S and cc8D

cc3S and cc3D

cc13S and cc13D

cc14

cc8S and cc8D

cc3S and cc3D

cc13S and cc13D

cc14

cc8S and cc8D

cc3S and cc3D

Figure 18. Vertical sections showing distribution of (A) dissolved ammonia plus organic nitrogen, 

(B) dissolved phosphorus, and (C) dissolved organic carbon concentrations in ground water beneath 

Cattlemans detention basin prior to its construction, late April and May 2001.
34 Chemistry of Runoff and Shallow Ground Water at the Cattlemans Detention Basin Site, South Lake Tahoe, California

Dissolved nitrate plus nitrite concentrations in ground 

water from the meadow deposits were consistently less than 

0.33 mg/L as nitrogen. Ammonia and ammonia plus organic 

nitrogen (dissolved kjeldahl nitrogen) were consistently higher 

than dissolved nitrate plus nitrite throughout the year (fig. 22). 

Ammonia and ammonia plus organic nitrogen was highest in 

November at well cc3S (fig. 22A), whereas highest concentrations were observed in July at wells cc8S, cc13S, and cc14 

(figs. 22B–D). Concentrations of ammonia plus organic nitrogen should always be greater than or equal to ammonia. This 

was the case for all analyses in which dissolved ammonia 

plus organic nitrogen concentrations were less than 1 mg/L; 

however, for concentrations that exceeded 1 mg/L, analytical 

results of dissolved ammonia plus organic nitrogen were occasionally less than ammonia. When the difference in concentrations exceeded the analytical error, the concentrations of dissolved ammonia plus organic nitrogen was assumed to equal 

the ammonia concentration. Analysis of ammonia had less variability among samples from the same well than did the ammonia plus organic nitrogen, thus the error in the analysis was 

assumed to be in the analysis for the ammonia plus organic 

nitrogen.

Dissolved phosphorus concentrations in all ground water 

were consistently lower in July than at the other sampled dates. 

The decrease in dissolved phosphorus in July may be the result 

of greater microbial activity in the unconsolidated deposits. 

Concentrations of dissolved phosphorus should always be 

greater than or equal to the concentration of orthophosphorus. 

Similar to ammonia, an occasional analytical result of orthophosphorus was greater than that of dissolved phosphorus. 

When the difference in concentrations exceeded the analytical 

error, the concentration of dissolved orthophosphorus was 

assumed to equal the dissolved phosphorus. For example, the 

July sample from well cc14 had a dissolved orthophosphorus 

concentration greater than the concentration of dissolved phosphorus plus the analytical error. The concentration of orthophosphorus in the well exceeded all other analyses from the 

well and all analyses for that date. Consequently, the orthophosphorus was set equal to the dissolved phosphorus. 

Dissolved nitrogen concentrations were much lower in the 

deeper sand and gravel than in the meadow deposits (figs. 22 

and 23). Although ammonia plus organic nitrogen concentrations were the predominant form of nitrogen, concentrations did 

not exceed 0.6 mg/L as nitrogen. Ammonia plus organic nitrogen concentrations were highest in November 2001 at wells 

cc3D and cc8D (fig. 23A and B), and were highest in January at 

well cc13D (fig. 23C). Dissolved phosphorus concentrations 

were lowest in July, and showed the same pattern as ground 

water from wells in the meadow deposits. Orthophosphorus 

generally follows the same trend as dissolved phosphorus.

Figure 19. Relation between the mean concentration of dissolved organic carbon to mean concentration of total 

dissolved nitrogen in ground-water samples from the area of Cattlemans detention basin prior to and during its 

construction, January to November 2001.

0

3

6

9

12

15

18

0 2 4 6 8 10 12

DISSOLVED ORGANIC CARBON, IN MILLIGRAMS PER LITER

TOTAL DISSOLVED NITROGEN, IN MILLIGRAMS PER LITER

cc3S cc8S

cc9 cc10

cc11 cc12

cc13S cc14

cc15 cc21
Ground Water 35

2001

D cc14

BICARBONATE AND CHLORIDE CONCENTRATIONS, IN MILLIGRAMS PER LITER

0

10

20

30

40

50

60

70

80

0

20

40

60

80

100

120

140

160

January 18 May 8 July 18 September 18

January 17 May 2 July 16 November 7

January 17 April 30 July 17 November 7

January 18 May 7 July 17 September 19

Calcium Sodium

Iron Bicarbonate

Chloride

C cc13S

0

10

20

30

40

50

60

70

80

0

20

40

60

80

100

120

140

160

B cc8S

CALCIUM, SODIUM, AND IRON CONCENTRATIONS, IN MILLIGRAMS PER LITER

0

10

20

30

40

50

60

70

80

0

40

80

120

160

200

240

280

320

A cc3S

0

10

20

30

40

50

60

70

80

0

20

40

60

80

100

120

140

160

2001

C cc13D

0

20

40

60

80

100

120

140

160

January 18 May 8 July 17 September 19

January 17 May 2 July 16 November 7

January 17 April 30 July 17 November 7

0

10

20

30

40

50

60

70

80

Calcium

Sodium

Iron

Bicarbonate

Chloride

B cc8D

0

20

40

60

80

100

120

140

160

CALCIUM, SODIUM, AND IRON CONCENTRATIONS, IN MILLIGRAMS PER LITER 

BICARBONATE AND CHLORIDE CONCENTRATIONS, IN MILLIGRAMS PER LITER

0

10

20

30

40

50

60

70

80

A cc3D

0

20

40

60

80

100

120

140

160

0

10

20

30

40

50

60

70

80

Figure 20. Graphs showing trends of major dissolved constituents

in ground water from meadow deposits in the area of Cattlemans 

detention basin prior to and during its construction, January to 

November 2001.

Figure 21. Graphs showing trends of major dissolved constituents 

in ground water from deeper sand and gravel in the area of 

Cattlemans detention basin prior to and during its construction, 

January to November 2001.
36 Chemistry of Runoff and Shallow Ground Water at the Cattlemans Detention Basin Site, South Lake Tahoe, California

2001

D cc14

January 18 May 8 July 18 September 18

0

0.1

0.2

0.3

0.4

0

1

2

3

4

NITROGEN CONCENTRATION, IN MILLIGRAMS PER LITER AS NITROGEN

PHOSPHORUS CONCENTRATION, IN MILLIGRAMS PER LITER AS PHOSPHORUS

C cc13S

January 18 May 7 July 17 September 19

Ammonia

Ammonia plus organic nitrogen

Nitrate plus nitrite

Phosphorus

Orthophosphorus

0

0.1

0.2

0.3

0.4

0

1

2

3

4

B cc8S

January 17 April 30 July 17 November 7

0

0.1

0.2

0.3

0.4

0

6

12

18

24

A cc3S

January 7 May 2 July 16 November 7

0

0.1

0.2

0.3

0.4

0

2

4

6

8

January 18 May 8 July 17

2001

September 19

C cc13D

0

0.3

0.6

0.9

0

0.1

0.2

0.3

January 17 April 30 July 17 November 7

NITROGEN CONCENTRATION, IN MILLIGRAMS PER LITER AS NITROGEN

PHOSPHORUS CONCENTRATION, IN MILLIGRAMS PER LITER AS PHOSPHORUS

B cc8D

0

0.2

0.4

0.6

0

0.1

0.2

0.3

January 17 May 2 July 16 November 7

A cc3D

0

0.2

0.4

0.6

0

0.1

0.2

0.3

Ammonia Ammonia plus organic nitrogen

Nitrate plus nitrite Phosphorus

Orthophosphorus

Figure 22. Graphs showing trends of dissolved nitrogen and 

phosphorus in ground water from meadow deposits in the

area of Cattlemans detention basin prior to and during its 

construction, January to November 2001.

Figure 23. Graphs showing trends of dissolved nitrogen and 

phosphorus in ground water from deeper sand and gravel in the 

area of Cattlemans detention basin prior to and during its 

construction, January to November 2001.
Summary and Conclusions 37

Dissolved organic carbon concentrations were highest in 

November 2001 at wells cc3S, cc8S, and cc3D (fig. 24). The 

higher organic carbon concentrations in wells cc3S and cc3D 

coincided with higher dissolved ammonia and organic nitrogen 

concentrations compared with samples collected earlier (figs. 

22A and 23A). The wells were sampled after the construction 

of the detention basin and following one storm that produced 

runoff from Pioneer Trail and Montgomery Estates subdivision 

on September 25, 2001. The runoff produced a rapid increase in 

water levels in wells cc3S, cc8S, cc3D, and cc8D (fig. 11A). 

The quality of the runoff that entered the newly constructed 

basin was unknown because the automatic flow meter and 

sampler had not been installed. It is possible that this water may 

have resulted in an increase in both dissolved organic 

carbon and nitrogen concentrations at wells cc3S and cc3D; 

however, dissolved ammonia plus organic nitrogen concentration decreased from July to November 2001 at well cc8S, which 

is inconsistent with the increase in dissolved organic carbon. 

Variations in concentrations and changes in concentrations of 

nutrients in ground water beneath the detention basin suggest 

that factors other than the transport of nutrients from the detention basin through ground water to Cold Creek may be important in evaluating the effectiveness of the detention basin.

Summary and Conclusions 

Detention basins are used in the Lake Tahoe area to reduce 

sediment and nutrient loads from urban runoff. Ground water 

beneath detention basins may provide avenues for transport of 

dissolved nutrients to nearby streams and thence to Lake Tahoe. 

A study was initiated in November 2000 in cooperation with 

the Tahoe Engineering Division of the El Dorado County 

Department of Transportation to determine if nutrients in a 

detention basin are transported by ground water to a nearby 

stream. The area being studied is the Cattlemans detention 

basin, which was constructed in a meadow adjacent to Cold 

Creek in South Lake Tahoe, California. This report summarizes 

data collected prior to construction of the detention basin. 

Thirty wells were installed in the area of the detention 

basin during November and December 2000, 10 months prior 

to construction of the detention basin in late August and 

September 2001. The wells were used to determine the direction 

of ground-water flow and to collect samples for analyses of 

dissolved ions and nutrient concentrations. Nutrient and 

sediment loads also were determined from urban runoff. 

The data collected prior to construction of the detention basin 

provide a basis for evaluating changes in sediment and nutrient 

loads to Cold Creek resulting from the detention basin.

The area where the detention basin was constructed has 

been altered by human activity several times. These activities 

include: altering the channel of Cold Creek at least twice; 

placement of fill across the meadow in the area of the detention 

basin; and construction of residences in the upland areas 

adjacent to the meadow. Excavation of a new channel for Cold 

Creek in 1994 below the natural water table likely increased 

ground water exchange along the channel, particularly in areas 

where meanders were constructed perpendicular to the direction of ground-water flow. The placement of fill across the 

meadow during construction of the nearby residences in the 

mid-1970’s likely affected runoff, infiltration, and groundwater chemistry in the area of the detention basin.

Unconsolidated deposits were categorized into three 

classes: (1) fill material consisting of a red-brown loamy sand 

with some gravel and an occasional cobble; (2) meadow deposits of gray silt and sand with stringers of coarse sand and fine 

gravel; and (3) deeper brown to yellow-brown sand and gravel 

with lenses of silt and sand. Ground water prior to construction 

of the detention basin generally flowed from Pioneer Trail in a 

west to northwest direction toward two meander bends on Cold 

Creek that trended perpendicular to the direction of groundwater flow. The direction of ground-water flow remained the 

same all year, although ground-water levels were higher during 

the spring and early summer than during the fall and winter. 

Total dissolved solids were generally higher in ground 

water from the meadow deposits than from the deeper sand and 

gravel. The principle dissolved constituents are calcium, 

sodium, bicarbonate, and chloride. Dissolved iron concentrations in ground water from the meadow deposits can exceed

0

1

2

3

4

5

6

2001

DISSOLVED ORGANIC CARBON CONCENTRATION, IN MILLIGRAMS PER LITER

cc13D

cc3D

cc8D

B Ground water from deeper sand and gravel

Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec

0

3

6

9

12

15

cc3S

cc8S

cc13S

cc14

A Ground water from meadow deposits

Figure 24. Graphs showing trends of dissolved organic carbon in 

ground water in the area of Cattlemans detention basin prior to

and during its construction, January to November 2001.
38 Chemistry of Runoff and Shallow Ground Water at the Cattlemans Detention Basin Site, South Lake Tahoe, California

those of calcium and sodium. Concentrations of dissolved constituents in ground water generally had a greater range in the 

meadow deposits compared with the deeper sand and gravel. 

Concentrations of dissolved iron and chloride were 500 and 

30 times higher, respectively, in ground water from the meadow 

deposits than dissolved concentrations in Cold Creek. The high 

concentrations of dissolved iron (median concentration of 

15 mg/L) and the lack of dissolved oxygen (generally below the 

detection limit of 0.3 mg/L) indicate that ground water in the 

meadow deposits is anoxic. The lack of oxygen is likely caused 

by microbial oxidation of organic matter. The source of chloride 

(median concentration in the meadow deposits of 32 mg/L) is 

most likely from the application of a mixture of cinders and salt 

on the surface streets during winter.

Nitrogen concentrations were generally higher in ground 

water from the meadow deposits than in ground water from the 

deeper sand and gravel. Higher concentrations of dissolved 

nitrogen correspond to higher concentrations of dissolved 

organic carbon. Ammonia plus organic nitrogen were the 

dominant forms of dissolved nitrogen and ranged from 0.04 to 

18 mg/L as nitrogen. Ammonia plus organic nitrogen concentrations were highest in the middle of the area where fill covered 

the meadow deposits. Nitrate plus nitrite concentrations were 

low (<0.33 mg/L) throughout the area. Dissolved nitrogen and 

organic carbon did not show a consistent change in the direction 

of ground-water flow. This suggests that nitrogen concentrations in ground water are controlled by chemical and biological 

reactions within the meadow deposits.

Dissolved phosphorus concentrations ranged from 0.004 

to 0.4 mg/L and were similar in ground water from both the 

meadow deposits and the deeper sand and gravel. Concentrations of phosphorus generally increased in the direction of 

ground-water flow. Consequently, dissolved phosphorus was 

lower in ground water from well cc3S on the east side of the 

detention basin and higher at well cc14 on the west side next 

to Cold Creek. This suggests that the dissolved phosphorus 

concentrations in ground water are controlled by dissolution of 

minerals in the unconsolidated deposits. Dissolved phosphorus 

concentrations decreased throughout the area in July. This 

decrease may be the result of greater microbial activity in 

ground water or from the uptake by roots during the summer.

In conclusion, nitrogen, phosphorus, and iron are dissolved in ground water beneath the area of the planned detention basin in sufficient concentrations that could affect nutrient 

concentrations in Cold Creek or in the streambed sediments. 

Although the expected result of excavating a detention basin 

adjacent to Cold Creek is to reduce nutrient loads into Cold 

Creek from urban runoff by capturing sediments, the detention 

basin potentially could increase ground-water flow through the 

meadow deposits by inducing greater recharge whenever the 

detention basin is filled with runoff. 

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Since 1879, the U.S. Geological Survey has been providing maps, reports, and information to help others 

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Prudic and others—CHEMISTRY OF RUNOFF AND SHALLOW GROUND WATER AT THE CATTLEMANS DETENTION BASIN SITE, SOUTH LAKE TAHOE, CALIFORNIA, AUGUST 2000 – NOVEMBER 2001—USGS, SIR 2004-5254