Three-Dimensional Visualization Maps of Suspended-Sediment

Prepared in cooperation with the U.S. Army Corps of Engineers

Three-Dimensional Visualization Maps of Suspended- Sediment Concentrations during Placement of Dredged Material in 21st Avenue West Channel Embayment, Duluth-Superior Harbor, Duluth, Minnesota, 2015

Explanation 240

180

in milligramps per liter 22

8 Suspended-sediment concentration,

End of dredge material discharge pipe

Scientific Investigations Report 2016–5086

U.S. Department of the Interior U.S. Geological Survey Cover illustration: Modified version of figure 13 from this report and 21st Avenue West Channel Embayment of the Duluth-Superior Harbor, Duluth, Minnesota, on September 4, 2015 (photograph provided by U.S. Army Corps of Engineers). Three-Dimensional Visualization Maps of Suspended-Sediment Concentrations during Placement of Dredged Material in 21st Avenue West Channel Embayment, Duluth-Superior Harbor, Duluth, Minnesota, 2015

By Joel T. Groten, Christopher A. Ellison, and Mollie H. Mahoney

Prepared in cooperation with the U.S. Army Corps of Engineers

Scientific Investigations Report 2016–5086

U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior SALLY JEWELL, Secretary U.S. Geological Survey Suzette M. Kimball, Director

U.S. Geological Survey, Reston, Virginia: 2016

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Suggested citation: Groten, J.T., Ellison, C.A., and Mahoney, M.H., 2016, Three-dimensional visualization maps of suspended-sediment concentrations during placement of dredged material in 21st Avenue West Channel Embayment, Duluth-Superior Harbor, Duluth, Minnesota, 2015: U.S. Geological Survey Scientific Investigations Report 2016–5086, 26 p., http:// dx.doi.org/10.3133/sir20165086.

ISSN 2328-0328 (online) iii

Acknowledgments

The authors would like to thank the U.S. Army Corps of Engineers and Roen Salvage for their assistance with this study. Esther Johnson and Joseph Kreitinger of the U.S. Army Corps of Engineers were integral to the design and implementation of the study. Corey Weston and Daniel Carlson of the U.S. Army Corps of Engineers provided key support for coordinating field aspects of the study.

Gerald Storey, Brent Mason, J. William Lund, Joshua Ayers, Lindsay Hastings, Molly McCool, Chris Sanocki, Michael Roberts, Scott Bennett, and Christopher Ruth of the U.S. Geological Sur- vey and Shon Schooler of the Lake Superior National Estuarine Research Reserve are acknowledged for assistance with data collection. Mark Brigham, Erik Smith, and Paul Reneau of the U.S. Geological Survey are acknowledged for their technical reviews of the report. iv

Contents

Abstract...... 1 Introduction...... 1 Purpose and Scope...... 3 Description of the Study Area...... 3 Methods of Data Collection and Analysis...... 7 Model Development...... 7 Relation between Suspended-Sediment Concentrations and Turbidity...... 8 Generation of Three-Dimensional Visualization Maps ...... 9 Three-Dimensional Visualization Maps of Suspended-Sediment Concentrations and Limitations...... 9 Summary ...... 22 References Cited...... 22 Appendix 1...... 25

Figures

1. Map showing location of the study area within the 21st Avenue West Channel Embayment of the Duluth-Superior Harbor, Duluth, Minnesota...... 2 2. Configuration one schematic...... 3 3. Configuration two schematic...... 4 4. Configuration three schematic...... 4 5. Configuration four schematic...... 5 6. Aerial photograph showing silt curtain within the 21st Avenue West Channel Embayment of the Duluth-Superior Harbor, Duluth, Minnesota, on October 29, 2015...... 5 7. Map showing selected sampling sites used for generation of three-dimensional suspended-sediment concentration maps during 2015 within the 21st Avenue West Channel Embayment of the Duluth-Superior Harbor, Duluth, Minnesota...... 6 8. Graph showing relation between suspended-sediment concentration and turbidity for selected sites in the 21st Avenue West Channel Embayment, Duluth-Superior Harbor, 2014 and 2015...... 8 9. Three-dimensional suspended-sediment concentration map of the study area within the 21st Avenue West Channel Embayment in the Duluth-Superior Harbor on July 21, 2015, before placement of dredged materials...... 10 10. Three-dimensional suspended-sediment concentration map of the study area within the 21st Avenue West Channel Embayment in the Duluth-Superior Harbor on August 16, 2015, during placement of dredged materials with configuration one and without a silt curtain...... 11 11. Three-dimensional suspended-sediment concentration map of the study area within the 21st Avenue West Channel Embayment in the Duluth-Superior Harbor on August 22, 2015, during placement of dredged materials with configuration two and without a silt curtain...... 12 v

12. Three-dimensional suspended-sediment concentration map of the study area within the 21st Avenue West Channel Embayment in the Duluth-Superior Harbor on August 28, 2015, during placement of dredged materials with configuration three and without a silt curtain...... 13 13. Three-dimensional suspended-sediment concentration map of the study area within the 21st Avenue West Channel Embayment in the Duluth-Superior Harbor on September 4, 2015, during placement of dredged materials with configuration four and without a silt curtain...... 14 14. Three-dimensional suspended-sediment concentration map of the study area within the 21st Avenue West Channel Embayment in the Duluth-Superior Harbor on September 11, 2015, during placement of dredged materials with configuration four and without a silt curtain...... 15 15. Three-dimensional suspended-sediment concentration map of the study area within the 21st Avenue West Channel Embayment in the Duluth-Superior Harbor on September 18, 2015, during placement of dredged materials with configuration four and with a silt curtain...... 16 16. Three-dimensional suspended-sediment concentration map of the study area within the 21st Avenue West Channel Embayment in the Duluth-Superior Harbor on September 22, 2015, during placement of dredged materials with configuration four and with a silt curtain...... 17 17. Three-dimensional suspended-sediment concentration map of the study area within the 21st Avenue West Channel Embayment in the Duluth-Superior Harbor on October 7, 2015, during placement of dredged materials with configuration four and with a silt curtain...... 18 18. Three-dimensional suspended-sediment concentration map of the study area within the 21st Avenue West Channel Embayment in the Duluth-Superior Harbor on October 29, 2015, during placement of dredged materials with configuration four and with a silt curtain...... 19 19. Three-dimensional suspended-sediment concentration map of the study area within the 21st Avenue West Channel Embayment in the Duluth-Superior Harbor on November 6, 2015, 24 hours after placement of dredged materials ceased...... 20 20. Three-dimensional suspended-sediment concentration map of the study area within the 21st Avenue West Channel Embayment in the Duluth-Superior Harbor on November 8, 2015, 72 hours after placement of dredged material ceased...... 21

Appendix Tables

1–1. Summary of turbidity and suspended-sediment concentrations used for calibration of the simple linear regression model for sampled sites in the 21st Avenue West Channel Embayment, Duluth-Superior Harbor, 2014 through 2015...... 26 1–2. Results of quality-assurance samples for suspended-sediment concentrations in the 21st Avenue West Channel Embayment, Duluth-Superior Harbor, 2014 through 2015...... 26 1–3. Turbidity and suspended-sediment concentrations outliers collected in the 21st Avenue West Channel Embayment, Duluth-Superior Harbor, 2014 through 2015...... 26 1–4. Information on selected sampling sites in the 21st Avenue West Channel Embay- ment, Duluth-Superior Harbor, 2015, and predicted suspended-sediment concentrations for 12 dates in 2015 during which turbidity was measured...... 26 vi

Conversion Factors

International System of Units to U.S. customary units Multiply By To obtain Length meter (m) 3.281 feet (ft) Area square kilometer (km2) 0.3861 square mile (mi2)

Datum

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Vertical coordinate information is referenced to the International Great Lakes Datum of 1985 (IGLD 85).

Elevation, as used in this report, refers to distance above the vertical datum.

Supplemental Information

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

Abbreviations

® registered trademark AOC Area of Concern BCF bias-correction factor BUI beneficial use impairment FNU formazin nephelometric units NWIS National Water Information System R 2 coefficient of determination SLR simple linear regression SSC suspended-sediment concentration USACE U.S. Army Corps of Engineers USGS U.S. Geological Survey UTM Universal Transverse Mercator Three-Dimensional Visualization Maps of Suspended- Sediment Concentrations during Placement of Dredged Material in 21st Avenue West Channel Embayment, Duluth-Superior Harbor, Duluth, Minnesota, 2015

By Joel T. Groten,1 Christopher A. Ellison,1 and Mollie H. Mahoney2

Abstract Introduction

Excess sediment in rivers and estuaries poses serious Suspended sediment is a major concern in U.S. water- environmental and economic challenges. The U.S. Army ways because of the role it plays in water quality degradation, Corps of Engineers (USACE) routinely dredges sediment in navigability, and loss of aquatic habitat (Baker, 1980; U.S. Federal navigation channels to maintain commercial shipping Army Corps of Engineers, 2016a; Minnesota Pollution Con- operations. The USACE initiated a 3-year pilot project in 2013 trol Agency, 2009). Under certain conditions, transport and to use navigation channel dredged material to aid in restora- deposition of suspended sediment fills in navigable waterways, tion of shoreline habitat in the 21st Avenue West Channel requiring costly dredging operations to maintain commercial Embayment of the Duluth-Superior Harbor. Placing dredged shipping (U.S. Army Corps of Engineers, 2016b). The 21st material in the 21st Avenue West Channel Embayment sup- Avenue West Channel Embayment of the Duluth-Superior ports the restoration of shallow bay aquatic habitat aiding in Harbor (fig. 1) is located in the lower St. Louis River Estuary, the delisting of the St. Louis River Estuary Area of Concern. which is listed by the International Joint Commission as an The U.S. Geological Survey, in cooperation with the Area of Concern (AOC). An AOC is defined as “a geographic USACE, collected turbidity and suspended-sediment concen- area that fails to meet the general or specific objectives of the trations (SSCs) in 2014 and 2015 to measure the horizontal beneficial-use agreement where such failure has caused or and vertical distribution of SSCs during placement operations is likely to cause impairment of beneficial use of the area’s of dredged materials. These data were collected to help the ability to support aquatic life’’ (U.S. Environmental Protection USACE evaluate the use of several best management prac- Agency, 2016). Nine beneficial use impairments (BUIs) are tices, including various dredge material placement techniques listed for the lower St. Louis River Estuary AOC, and one of and a silt curtain, to mitigate the dispersion of suspended these BUIs is the loss of fish and wildlife habitat (LimnoTech, sediment. 2013). Three-dimensional visualization maps are a valuable tool The U.S. Army Corps of Engineers (USACE), Detroit for assessing the spatial displacement of SSCs. Data collec- District, initiated a 3-year pilot project in 2013 to place tion was designed to coincide with four dredged placement dredged material in support of their navigation mission with configurations that included periods with and without a silt the additional benefit of aiding in the restoration of shoreline curtain as well as before and after placement of dredged habitat of the 21st Avenue West Channel Embayment (fig. materials. Approximately 230 SSC samples and correspond- 1). The goal of the pilot project was to determine the least ing turbidity values collected in 2014 and 2015 were used to expensive and environmentally acceptable manner to place develop a simple linear regression model between SSC and Duluth-Superior Harbor dredged material while also con- turbidity. Using the simple linear regression model, SSCs were tributing to the removal of BUIs to aid in the delisting of the estimated for approximately 3,000 turbidity values at approxi- lower St. Louis River Estuary AOC. The 21st Avenue West mately 100 sampling sites in the 21st Avenue West Channel Channel Embayment was chosen for the pilot project because Embayment of the Duluth-Superior Harbor. The estimated of its proximity to existing dredged material sources, lack of SSCs served as input for development of 12 three-dimensional habitat, and its sheltered location within the Duluth-Superior visualization maps. Harbor (U.S. Army Corps of Engineers, 2014). In coordination with the Minnesota Pollution Control Agency, the USACE implemented best management practices designed to miti- 1U.S. Geological Survey. gate disbursement of suspended sediment during dredged 2U.S. Army Corps of Engineers. 2 Three-Dimensional Visualization Maps of Suspended-Sediment Concentrations during Placement of Dredged Material 92°05' Lake Superior

Lake Superior Lake Superior Lake Superior Lake Wisconsin Superior Duluth Wisconsin Minnesota Minnesota 92°06' KILOMETERS 2 U.S. Geological Survey streamgage Superior Bay Duluth Ship Canal at Duluth, Minnesota (464646092052900) MILE Blatnik Bridge 1 5 3 1.5 5 I I 5 3 1 Interstate Island 92°07' Area 0.5 0.5 21st Avenue West 21st Avenue Channel Embayment Study Area of map shown in figure 7 Coffee Creek

0 0 St. Louis River Estuary River Louis St. North 21st Avenue West North 21st Avenue 5 3 I I 3 5 Miller Creek estern Lake W Superior Sanitary District 92°08' Bong Bridge Location of the study area within the 21st Avenue West Channel Embayment of the Duluth-Superior Harbor, Duluth, Minnesota. Channel Embayment of the Duluth-Superior Harbor, West Location of the study area within 21st Avenue

92°09' Base from Minnesota Department of Natural Resources digital data, 2012, various scales zone 15 Mercator, Universal Transverse North American datum of 1983 (NAD 1983) Figure 1. 46°46' 46°45' 46°44' fig01.ai Introduction 3 material placement operations. This included implementation were generated to elucidate the distribution of SSCs under of various dredged material placement configurations and the following conditions: (1) before placement of dredged the employment of a silt curtain for a substantial portion of materials, (2) during placement of dredged materials using dredged material placement. Dredge material was hydrauli- four dredged-material placement configurations without a silt cally pumped through a high density polyethylene pipe and curtain, (3) during placement of dredged materials with a silt was discharged through one of four configurations (figs. 2–5). curtain, and (4) after placement of dredged materials ceased. During portions of dredged material placement, a permeable silt curtain made of a heavy vinyl-coated fabric skirt spanned approximately 500 meters (m) across the 21st Avenue West Purpose and Scope Channel Embayment and extended from the top of the water The purpose of this report is to document the vertical column to 0.31–0.61 m above the bottom of the water column and horizontal displacement of suspended sediment before, (fig. 6). during, and after placement of dredged material in the 21st In 2014 and 2015, the U.S. Geological Survey (USGS), Avenue West Channel Embayment in the Duluth-Superior in cooperation with USACE, collected approximately 230 Harbor, Duluth, Minnesota. Specifically, this report presents water samples at selected sites in the 21st Avenue West Chan- a series of 12 three-dimensional visualization maps of SSCs nel Embayment for analysis of suspended-sediment concen- from July to November 2015. This report includes descriptions tration (SSC). The USGS also collected approximately 3,000 of the study area, methods of data collection, development of turbidity measurements at approximately 100 sites (fig. 7) in an SLR model, and the three-dimensional map interpolation of 2015. Data collection was designed to quantify the horizontal predicted SSC values. and vertical distribution of SSCs during placement of dredged material. Data collected during 2014 and 2015 were used to develop a simple linear regression (SLR) model between SSC Description of the Study Area and turbidity. Rasmussen and others (2009) and Lietz and Debiak (2005) reported that when the magnitude of turbidity The cities of Duluth, Minnesota (population 86,238), and is proportional to SSC, then the turbidity-SSC relation can be Superior, Wisconsin (population 26,705) are port towns on quantified through an SLR model. The SLR model was used Lake Superior (U.S. Census Bureau, 2016). The 21st Avenue to predict SSCs from the measured turbidity values at each West Channel Embayment (study area) is in the lower St. site. Using these data, 12 three-dimensional visualization maps Louis River Estuary, which is the largest U.S. tributary to

Top to remain open for visual inspection Chute height must be high enough to prevent splash-out 4 sided or cylindrical open-ended vertical chute Floating high density polyethylene pipe from dredge/pump Flow direction Flow direction

Floating work platform Water level

Chute has telescoping capability to change length

End of chute approximately 1−2 feet above current bottom elevation Gravity flow Existing bottom

Figure 2. Configuration one schematic (image provided by U.S. Army Corps of Engineers).

fig02.ai 4 Three-Dimensional Visualization Maps of Suspended-Sediment Concentrations during Placement of Dredged Material

Floating high density polyethylene pipe from dredge/pump Flow direction Flow direction

Floating work platform Water level

Flow direction

End of discharge pipe approximately 1−2 feet below water surface

Baffle plate fixed to pipe

Existing bottom

Figure 3. Configuration two schematic (image provided by U.S. Army Corps of Engineers).

fig03.ai Floating high density polyethylene pipe from dredge/pump Field formed or Flow direction Flow direction pre-formed bend Floating work platform Water level

Discharge pipe is vertical or nearly vertical Flow direction

Position baffle plate below target Baffle plate fixed to pipe elevation of placed dredge material to prevent bottom scour

Existing bottom

Figure 4. Configuration three schematic (image provided by U.S. Army Corps of Engineers).

fig04.ai Introduction 5

Floating high density polyethylene pipe from dredge/pump Flow direction Flow direction Baffle plate fixed to pipe Floating work platform Water level

Existing bottom

Figure 5. Configuration four schematic (image provided by U.S. Army Corps of Engineers).

fig05.ai

Silt curtain

N Figure 6. Silt curtain within the 21st Avenue West Channel Embayment of the Duluth-Superior Harbor, Duluth, Minnesota, on October 29, 2015 (photograph provided by U.S. Army Corps of Engineers).

fig06.ai 6 Three-Dimensional Visualization Maps of Suspended-Sediment Concentrations during Placement of Dredged Material 92°06'30" KILOMETER 1 EXPLANATION August 16, 2015 August 22, 2015 August 28, 2015 September 4, 2015 September 11, 2015 September 18, 2015 September 22, 2015 October 7, 2015 October 29, 2015 0 1 2 0 0 0 1 1 1 Location and date of the end of dredged material discharge pipe MILE G G G 0.5 9 8 7 6 5 9 9 9 9 9 G G G G G 1 9 9 8 4 3 2 0 9 9 T 9 T 9 G G G G G G 8 7 6 5 4 3 2 8 8 8 8 8 8 8 G G G G G G G 1 0 9 8 7 6 5 4 0.5 8 8 7 7 7 7 7 7 G G G G G G G G 0 7 3 2 1 9 8 7 6 5 7 7 7 T 6 6 6 6 6 G G G G G G G G G I 5 3 3 2 1 0 9 8 7 6 5 4 92°07' 6 6 6 6 5 5 5 5 5 5 G G G G G G G G G G 3 2 1 0 9 8 7 6 5 4 3 3 5 5 5 5 4 4 4 4 4 4 4 G G G G G G G G G G G 7 5 3 3 2 1 0 9 8 6 4 2 1 3 4 4 4 3 T 3 T 3 3 3 3 3 G G G G G G G G G G G G 7 2 6 5 4 3 2 1 0 9 8 9 8 T 2 2 2 2 2 2 2 1 1 2 2 G G G G G G G G G G G G 0 0 7 6 5 4 3 2 0 1 1 1 1 1 1 1 1 8 9 1 G G G G G G G G G G North Channel 5 6 7 G G G Sampling site and number (see table 1 − 4) Federal navigation channel I 3 5 1st Avenue Selected sampling sites used for generation of three-dimensional suspended-sediment concentration maps during 2015 within the 2 1st Avenue

92°07'30" Base from Minnesota Department of Natural Resources digital data, 2012, various scales zone 15 Mercator, Universal Transverse North American datum of 1983 (NAD 1983) Figure 7. Duluth, Minnesota. Channel Embayment of the Duluth-Superior Harbor, West 5 46°45'40" 46°45'20" Methods of Data Collection and Analysis 7

Lake Superior (The Nature Conservancy, 2016). The size of 12 percent, with some sites having noticeably higher relative the contributing watershed to the study area is approximately percent differences than others (table 1–2 in appendix 1). Sites 9,582 square kilometers (km2) (Lorenz and others, 2009), and with higher differences between primary and replicate samples the size of the study area is approximately 2 km2 (Host and most likely are associated with unstable site conditions. others, 2013). The study area receives wastewater effluent Water samples collected in 2014 and 2015 were trans- from the Western Lake Superior Sanitary District (fig. 1) along ported to the USGS sediment laboratory in Iowa City, Iowa, a point in the southeast direction from the wastewater treat- and analyzed for SSCs according to procedures in Guy (1969). ment plant, and Miller and Coffee Creeks also discharge into SSC was reported in milligrams per liter, and turbidity was the northernmost bay. reported in FNU. The results of USGS sampling are presented One primary Federal navigation channel is within the in table 1–1 in appendix 1; the results also are stored in the 21st Avenue West Channel Embayment along with a decom- USGS National Water Information System (NWIS) and are missioned deep-water channel that hereafter will be referred available at http://waterdata.usgs.gov/nwis (U.S. Geological to as the North Channel (fig. 7). The North Channel bisects Survey, 2016). the study area and extends into the Federal navigation chan- Turbidity data were collected in 2014 and 2015 at mul- nel. The North Channel extends toward the northernmost bay, tiple sites and depths and are available at http://waterdata.usgs. but sections were filled in with dredged material during the gov/nwis (U.S. Geological Survey, 2016). In 2014, turbidity USACE pilot project. Interstate Island (fig. 1) is located to data were collected at three depths in the water column if the the southeast of the study area and was created from dredged water depth was 3.05 m or greater. Measurements were col- material. Interstate Island is maintained as a Wildlife Manage- lected at 0.31 m below the water surface, at mid-depth, and ment Area by the Minnesota Department of Natural Resources 0.31 m above the bottom of the estuary. If the total depth was (St. Louis River Estuary, 2016). less than 3.05 m but equal to or greater than 1.53 m, then two The nearest streamgage is located at Superior Bay turbidity measurements were collected at 0.31 m below the Duluth Ship Canal in Duluth, Minnesota (USGS station water surface and 0.31 m above the bottom of the estuary. If 464646092052900) (fig. 1). The elevation of the water surface the depth was less than 1.53 m, then one turbidity measure- (stage readings) are recorded every 15-minutes, and prelimi- ment was collected at mid-depth. nary data are available at http://waterdata.usgs.gov/mn/nwis/ In 2015, additional turbidity measurements were col- uv?site_no=464646092052900. The reference datum for water lected for depths less than 3.35 m. This change was incorpo- surface is the International Great Lakes Datum of 1985. rated into the sampling plan to improve understanding of SSCs at shallower depths. If the water depth was 3.35 m or greater, then four turbidity measurements were collected at depths below the water surface of 0.31, 2.14, 3.05, and at Methods of Data Collection and 0.31 m above the bottom of the estuary. If the water depth was Analysis less than 3.35 m but greater than 3.05 m, then three turbidity measurements were collected below the water surface at 0.31, Data collection was designed to quantify horizontal and 2.14, and 3.05 m. If the water depth was less than 3.05 m but vertical distribution of SSCs within the 21st Avenue West greater than 2.44 m, then turbidity measurements were col- Channel Embayment. Approximately 100 monitoring sites lected at 0.31 and 2.14 m below the water surface. If the water (fig. 7) were established in the embayment from which SSC depth was 2.44 m or less but equal to or greater than 0.92 m, and turbidity measurements were collected. Each site con- then measurements were collected at 0.31 m below the water sisted of one to four depths from which samples or measure- surface and at 0.31 m above the estuary bottom. If the depth ments were collected vertically. was less than 0.92 m, then one measurement was collected at Depth-integrated samples were collected with a Kem- 0.31 m below the surface. merer (Wildco® Product Number 1520-A45, Yulee, Florida; Shelton, 1994). A YSI Inc. (Xylem Inc.®) model 6136 Model Development turbidity sensor and a YSI model 6920 V2 sonde were used to measure turbidity. Turbidity sensors were calibrated to three Approximately 230 SSC and corresponding turbidity YSI standards (0, 126, and 1,000 formazin nephelometric units values were used for SLR model development (table 1–1 [FNU]) in the morning before collection of turbidity mea- in appendix 1). During model development, eight outliers surements. Turbidity measurements and corresponding SSC were removed (four SSC values and the four corresponding samples were collected at the same depth, time, and location turbidity values) from the model development (table 1–3 in (table 1–1 in appendix 1). Sequential replicate SSC samples appendix 1). The four samples associated with the outliers were collected immediately after the primary water sample were collected in proximity to the end of the dredged mate- to assess variability of SSC measurements (table 1–2 in rial discharge pipe (table 1–3 in appendix 1). These unusual appendix 1). The overall mean absolute relative percent dif- measurements (outliers) may have been caused by rapidly ference between primary and sequential replicate samples was 8 Three-Dimensional Visualization Maps of Suspended-Sediment Concentrations during Placement of Dredged Material changing SSCs near the end of the dredged material discharge SSC = 10β0 * Turb.β1 * BCF (1) pipe (fig. 7). The simultaneous collection of the SSC sample and associated turbidity measurement from the same volume where of water near the end of the discharge pipe, which was being SSC is suspended-sediment concentration, in inundated with sediment directly from the discharge pipe, milligrams per liter; likely resulted in the observed discrepancies between the two β0 is the intercept; measurements. Turb. is turbidity, in formazin nephelometric units;

An SLR model was developed using SSC samples and β1 is the slope; and turbidity measurements collected in 2014 and 2015 (table 1–1 BCF is the bias-correction factor. in appendix 1; U.S. Geological Survey, 2016). The SLR model was then used to predict SSC from the measured turbidity values collected at selected sites in 2015 (table 1–4 Relation between Suspended-Sediment in appendix 1). The SSC and turbidity values were log- Concentrations and Turbidity transformed (base-10 logarithms) to normalize the data to meet the assumptions of the SLR model in order to reduce The relation between SSC and turbidity for the 2014 and heteroscedasticity and skewness of the residuals (Helsel and 2015 dataset is illustrated in figure 8. The resulting SLR equa- Hirsch, 2002). Log-transformed data were used to develop an tion follows: SLR equation using the S-Plus statistical package (TIBCO® Software Inc., 2010). Diagnostics for the model included a 0.8872 residual normal quantile-quantile plot (also known as a QQ SSC = 1.1876 * Turb. * 1.04 (2) plot; Chambers and others, 1983) and removing unusual measurements (outliers). Model variance was evaluated by plotting where residual and response values against fitted values. A bias- SSC is suspended-sediment concentration, in correction factor (BCF) (Duan, 1983) was applied to the data milligrams per liter; and after they were retransformed into the original units (Miller, Turb. is turbidity, in formazin nephelometric units. 1951; Koch and Smillie, 1986). The following model was used to predict SSC from turbidity:

1,000 EXPLANATION Measured value

Best fitted regression line 2 R Coefficient of determination

100

0.8872 Suspended-sediment concentration = 1.1876 x Turbidity x 1.04 10 2

Suspended-sediment concentration, in milligrams per liter R = 0.93

0 0 10 100 1,000 15,000 Turbidity, in formazin nephelometric units

Figure 8. Relation between suspended-sediment concentration and turbidity for selected sites in the 21st Avenue West Channel Embayment, Duluth-Superior Harbor, 2014 and 2015. Three-Dimensional Visualization Maps of Suspended-Sediment Concentrations and Limitations 9

The SLR equation had a p-value less than 0.01 and a coef- where 2 ficient of determination R( ) of 0.93, which indicate a strong, Ĉj is the interpolated value for grid node j, significant relation between SSC and turbidity. i is the first grid point, Using the SLR equation (equation 2), SSCs were pre- n is the total number of grid points, dicted for approximately 3,000 turbidity values collected on hij is the effective separation distance between 12 dates in 2015 at the sampling sites in the 21st Avenue grid node j and the neighboring point i,

West Channel Embayment of the Duluth-Superior Harbor Ci are the neighboring points, 2 (table 1–4 in appendix 1). The estimated SSCs served as input dij is the squared distance between grid node j for development of 12 three-dimensional visualization maps as and the neighboring point i, described in the following subsection. β is the power or weighting parameter, and δ is the smooth parameter (Franke, 1982). The fifth and final step involved displaying the location of the Generation of Three-Dimensional Visualization dredged material placement discharge pipe and the location of Maps the silt curtain.

A total of 12 three-dimensional visualization maps were created using three-dimensional visualization software Voxler®4 (Golden Software, LLC, 2012). Voxler®4 was used Three-Dimensional Visualization to display Universal Transverse Mercator (UTM) easting, Maps of Suspended-Sediment northing, and elevation coordinates (x, y, and z dimensions, respectively) and predicted SSC values for 12 dates in 2015 Concentrations and Limitations (table 1–4 in appendix 1). Between 244 and 261 predicted SSC values for each of 12 dates for approximately 100 sites The visualization maps were generated to elucidate the (fig. 7) were used to generate the three-dimensional visualiza- distribution of SSC under four conditions: (1) before place- tion maps. One to four SSC values at various depths were ment of dredged materials (fig. 9), (2) during placement of assigned to each of the sites during map generation. The data dredged materials using four dredged-material configurations collected in 2015 are referenced horizontally to the North (figs. 2–5) without a silt curtain (figs. 10–14), (3) during place- American Datum of 1983 using UTM projection Zone 15N. ment of dredged materials with a silt curtain (figs. 15–18), and During each of the 12 sampling days in 2015, 15-minute stage (4) after dredged material placements ceased (figs. 19 and 20). readings from the USGS streamgage at Superior Bay Duluth Three-dimensional visualization maps are valuable for assess- Ship Canal at Duluth, Minnesota (station 464646092052900) ing the spatial displacement of SSC during dredged material were averaged over each sampling day to obtain the surface- placement in open waters. Three-dimensional visualization water elevation. Elevations associated with SSC values were maps also provide an effective tool to support the design of determined by subtracting the measured sampling depths from projects requiring placement of dredged material in open the surface-water elevation. water, and such projects aid in the delisting of the lower St. A sequence of five steps was used to generate the Louis River Estuary from the International Joint Commis- three-dimensional visualization maps. The first step entailed sion’s AOC. using 2015 data to create a horizontal and vertical (x, y, and A limitation of the Voxler®4 software is its inability to z) grid of the bottom of the estuary using elevation software recognize and account for the presence of physical obstruc- Surfer®13 (Golden Software, LLC). The second step was tions between interpolated data points. For example, if a to create a visual display of the elevation grid of the bottom physical obstruction (such as a shoreline) is present between of the estuary using Voxler®4. The third step was to overlay sites with predicted SSC values, then Voxler®4 will continue a georeferenced Google Earth (Google Earth, 2016) aerial to interpolate SSC values through the obstruction as if it does photograph (image from August 2010) above the elevation not exist. The limitation is a concern because SSC values were grid of the estuary bottom. The fourth step entailed interpolat- interpolated and displayed for portions of the study area where ing SSC data between the sampling sites using Voxler®4 and a physical obstruction was present; thus, interpolated points the inverse distance method using the following equations near the shoreline and near the estuary bottom should be (Franke, 1982): closely inspected to ensure obstructions are not present.

n Ci The three-dimensional visualization maps presented in ∑ i=1 hijβ , and (3) this report should not be used for permitting, navigation, or Ĉj = n 1 ∑ i=1 hijβ other legal purposes. The USGS provides these maps as a reference and planning tool and users are cautioned to care- fully consider the use of the maps before making decisions h 2 2 (4) that concern personal or public safety or before the conduct ij = √dij + δ of business that involves substantial monetary or operational consequences. The USGS assumes no legal liability or respon- sibility resulting from the use. 10 Three-Dimensional Visualization Maps of Suspended-Sediment Concentrations during Placement of Dredged Material

Northing coordinates, in meters

Interstate 535 referenced to North American Datum of 1983 Universal Transverse Mercator zone 15

225

200 Elevation, in meters in Elevation,

175 referenced to the International Great Lakes Datum of 1985 1985 of Datum Lakes Great International the to referenced

EXPLANATION Estuary bottom 240

referenced to North American Datum of 1983 Universal Transverse Mercator zone 15 180 Easting coordinates, in meters Map data: Google, Google Earth (2016)

in milligrams per liter 45

Suspended-sediment concentration, 22 8

Figure 9. Three-dimensional suspended-sediment concentration map of the study area within the 21st Avenue West Channel fig09.ai Embayment in the Duluth-Superior Harbor on July 21, 2015, before placement of dredged materials. Three-Dimensional Visualization Maps of Suspended-Sediment Concentrations and Limitations 11

End of dredged material discharge pipe Northing coordinates, in meters

Interstate 535 referenced to North American Datum of 1983 Universal Transverse Mercator zone 15

225

200 Elevation, in meters in Elevation,

175 referenced to the International Great Lakes Datum of 1985 1985 of Datum Lakes Great International the to referenced

EXPLANATION 240 Estuary bottom

referenced to North American Datum of 1983 Universal Transverse Mercator zone 15 180 Easting coordinates, in meters Map data: Google, Google Earth (2016)

in milligrams per liter 45

22 Suspended-sediment concentration, 8

Figure 10. Three-dimensional suspended-sediment concentration map of the study area within the 21st Avenue West Channel fig10.ai Embayment in the Duluth-Superior Harbor on August 16, 2015, during placement of dredged materials with configuration one and without a silt curtain. 12 Three-Dimensional Visualization Maps of Suspended-Sediment Concentrations during Placement of Dredged Material

End of dredged material discharge pipe Northing coordinates, in meters

Interstate 535

referenced to North American Datum of 1983 Universal Transverse Mercator zone 15 225

200 Elevation, in meters in Elevation,

175 referenced to the International Great Lakes Datum of 1985 1985 of Datum Lakes Great International the to referenced

EXPLANATION 240 Estuary bottom

180 referenced to North American Datum of 1983 Universal Transverse Mercator zone 15 Map data: Google, Google Earth (2016) Easting coordinates, in meters

45 in milligrams per liter

22 Suspended-sediment concentration, 8

Figure 11. Three-dimensional suspended-sediment concentration map of the study area within the 21st Avenue West Channel Embayment in the Duluth-Superior Harbor on August 22, 2015, during placement of dredged materials with configuration two and fig11.ai without a silt curtain. Three-Dimensional Visualization Maps of Suspended-Sediment Concentrations and Limitations 13

End of dredged material discharge pipe

Interstate 535 Northing coordinates, in meters

referenced to North American Datum of 1983 Universal Transverse Mercator zone 15

225

200 Elevation, in meters in Elevation,

175 referenced to the International Great Lakes Datum of 1985 1985 of Datum Lakes Great International the to referenced

EXPLANATION Estuary bottom 240 referenced to North American Datum of 1983 Universal Transverse Mercator zone 15 Map data: Google, Google Earth (2016) Easting coordinates, in meters 180

in milligrams per liter 45

22 Suspended-sediment concentration, 8

Figure 12. Three-dimensional suspended-sediment concentration map of the study area within the 21st Avenue West Channel fig12.ai Embayment in the Duluth-Superior Harbor on August 28, 2015, during placement of dredged materials with configuration three and without a silt curtain. 14 Three-Dimensional Visualization Maps of Suspended-Sediment Concentrations during Placement of Dredged Material

End of dredged material discharge pipe

Northing coordinates, in meters Interstate 535

referenced to North American Datum of 1983 Universal Transverse Mercator zone 15

225

200 Elevation, in meters in Elevation,

175 referenced to the International Great Lakes Datum of 1985 1985 of Datum Lakes Great International the to referenced

EXPLANATION Estuary bottom 240

referenced to North American Datum of 1983 Universal Transverse Mercator zone 15 Map data: Google, Google Earth (2016) 180 Easting coordinates, in meters

in milligrams per liter 45

Suspended-sediment concentration, 22 8

Figure 13. Three-dimensional suspended-sediment concentration map of the study area within the 21st Avenue West Channel fig13.aiEmbayment in the Duluth-Superior Harbor on September 4, 2015, during placement of dredged materials with configuration four and without a silt curtain. Three-Dimensional Visualization Maps of Suspended-Sediment Concentrations and Limitations 15

End of dredged material discharge pipe

Northing coordinates, in meters Interstate 535

referenced to North American Datum of 1983 Universal Transverse Mercator zone 15

225

Elevation, in meters in Elevation, 200

175 referenced to the International Great Lakes Datum of 1985 1985 of Datum Lakes Great International the to referenced

EXPLANATION Estuary bottom 240 referenced to North American Datum of 1983 Universal Transverse Mercator zone 15 Easting coordinates, in meters Map data: Google, Google Earth (2016) 180

in milligrams per liter 45

22 Suspended-sediment concentration, 8

Figure 14. Three-dimensional suspended-sediment concentration map of the study area within the 21st Avenue West Channel Embayment in the Duluth-Superior Harbor on September 11, 2015, during placement of dredged materials with configuration four fig14.ai and without a silt curtain. 16 Three-Dimensional Visualization Maps of Suspended-Sediment Concentrations during Placement of Dredged Material

End of dredged material discharge pipe

Silt curtain Northing coordinates, in meters

Interstate 535

referenced to North American Datum of 1983 Universal Transverse Mercator zone 15

225

Elevation, in meters in Elevation, 200

175 referenced to the International Great Lakes Datum of 1985 1985 of Datum Lakes Great International the to referenced

Estuary bottom EXPLANATION 240 referenced to North American Datum of 1983 Universal Transverse Mercator zone 15 Easting coordinates, in meters Map data: Google, Google Earth (2016)

180

in milligrams per liter 45

22 Suspended-sediment concentration, 8

Figure 15. Three-dimensional suspended-sediment concentration map of the study area within the 21st Avenue West Channel Embayment in the Duluth-Superior Harbor on September 18, 2015, during placement of dredged materials with configuration four fig15.ai and with a silt curtain. Three-Dimensional Visualization Maps of Suspended-Sediment Concentrations and Limitations 17

End of dredged material discharge pipe

Northing coordinates, in meters Silt curtain

Interstate 535

referenced to North American Datum of 1983 Universal Transverse Mercator zone 15

225

Elevation, in meters in Elevation, 200

175 referenced to the International Great Lakes Datum of 1985 1985 of Datum Lakes Great International the to referenced

Estuary bottom EXPLANATION 240 referenced to North American Datum of 1983 Universal Transverse Mercator zone 15 Map data: Google, Google Earth (2016) Easting coordinates, in meters 180

in milligrams per liter 45

22 Suspended-sediment concentration, 8

Figure 16. Three-dimensional suspended-sediment concentration map of the study area within the 21st Avenue West Channel Embayment in the Duluth-Superior Harbor on September 22, 2015, during placement of dredged materials with configuration four fig16.ai and with a silt curtain. 18 Three-Dimensional Visualization Maps of Suspended-Sediment Concentrations during Placement of Dredged Material

End of dredged material discharge pipe

Northing coordinates, in meters Silt curtain

Interstate 535

referenced to North American Datum of 1983 Universal Transverse Mercator zone 15

225

Elevation, in meters in Elevation, 200

175 referenced to the International Great Lakes Datum of 1985 1985 of Datum Lakes Great International the to referenced

EXPLANATION Estuary bottom 240 referenced to North American Datum of 1983 Universal Transverse Mercator zone 15 Easting coordinates, in meters Map data: Google, Google Earth (2016) 180

in milligrams per liter 45

22 Suspended-sediment concentration, 8

Figure 17. Three-dimensional suspended-sediment concentration map of the study area within the 21st Avenue West Channel Embayment in the Duluth-Superior Harbor on October 7, 2015, during placement of dredged materials with configuration four fig17.ai and with a silt curtain. Three-Dimensional Visualization Maps of Suspended-Sediment Concentrations and Limitations 19

End of dredged material discharge pipe

Silt curtain

Interstate 535 Northing coordinates, in meters

referenced to North American Datum of 1983 Universal Transverse Mercator zone 15

225

Elevation, in meters in Elevation, 200

175 referenced to the International Great Lakes Datum of 1985 1985 of Datum Lakes Great International the to referenced

Estuary bottom EXPLANATION 240 referenced to North American Datum of 1983 Universal Transverse Mercator zone 15 Map data: Google, Google Earth (2016) Easting coordinates, in meters

180

in milligrams per liter 45

22 Suspended-sediment concentration, 8

Figure 18. Three-dimensional suspended-sediment concentration map of the study area within the 21st Avenue West Channel Embayment in the Duluth-Superior Harbor on October 29, 2015, during placement of dredged materials with configuration four fig18.ai and with a silt curtain. 20 Three-Dimensional Visualization Maps of Suspended-Sediment Concentrations during Placement of Dredged Material

Silt curtain Northing coordinates, in meters

Interstate 535

referenced to North American Datum of 1983 Universal Transverse Mercator zone 15

225

200 Elevation, in meters in Elevation,

175 referenced to the International Great Lakes Datum of 1985 1985 of Datum Lakes Great International the to referenced

EXPLANATION Estuary bottom 240

referenced to North American Datum of 1983 Universal Transverse Mercator zone 15 Easting coordinates, in meters Map data: Google, Google Earth (2016) 180

in milligrams per liter 45

22 Suspended-sediment concentration, 8

Figure 19. Three-dimensional suspended-sediment concentration map of the study area within the 21st Avenue West Channel fig19.ai Embayment in the Duluth-Superior Harbor on November 6, 2015, 24 hours after placement of dredged materials ceased. Three-Dimensional Visualization Maps of Suspended-Sediment Concentrations and Limitations 21

Northing coordinates, in meters Silt curtain

Interstate 535

referenced to North American Datum of 1983 Universal Transverse Mercator zone 15

225

200 Elevation, in meters in Elevation,

175 referenced to the International Great Lakes Datum of 1985 1985 of Datum Lakes Great International the to referenced

EXPLANATION Estuary bottom 240

referenced to North American Datum of 1983 Universal Transverse Mercator zone 15 Map data: Google, Google Earth (2016) 180 Easting coordinates, in meters

in milligrams per liter 45

22 Suspended-sediment concentration, 8

Figure 20. Three-dimensional suspended-sediment concentration map of the study area within the 21st Avenue West Channel Embayment in the Duluth-Superior Harbor on November 8, 2015, 72 hours after placement of dredged material ceased. fig20.ai 22 Three-Dimensional Visualization Maps of Suspended-Sediment Concentrations during Placement of Dredged Material

Summary Chambers, J.M., Cleveland, W.S., Kleiner, Beat, and Tukey, P.A., 1983, Graphical methods for data analysis: Boston, Excess sediment in rivers and estuaries poses serious Massachusetts, PWS-Kent Publishing Co., 395 p. environmental and economic challenges. The U.S. Army Duan, Naihua, 1983, Smearing estimate—A nonparametric Corps of Engineers (USACE) routinely dredges sediment in retransformation method: Journal of the American Statisti- Federal navigation channels to maintain commercial shipping cal Association, v. 78, no. 383, p. 605–610. [Also available operations. The 21st Avenue West Channel Embayment in the at http://dx.doi.org/10.2307/2288126.] Duluth-Superior Harbor is located in the lower St. Louis River Estuary, which is listed by the International Joint Commission Franke, R., 1982, Scattered data interpolation—Test of some as an Area of Concern (AOC). In 2013, the USACE, Detroit methods: Mathematics of Computations, v. 33, no. 157, District, initiated a 3-year pilot project to place dredged mate- p. 181–200. [Also available at http://dx.doi.org/10.1090/ rial in support of their navigation mission with the additional S0025-5718-1982-0637296-4.] benefit of aiding in the restoration of shoreline habitat of the 21st Avenue West Channel Embayment. The goal of the pilot Golden Software, LLC, 2012, Voxler®4: Golden, Colorado, project was to determine if dredged material could be used to Golden Software, LLC. [Also available at www.goldensoft- aid in the improvement of aquatic habitat, which will con- ware.com.] tribute to the delisting of sites from the lower St. Louis River Google Earth 7.15.1557, 2016: accessed December 26, 2015, Estuary AOC. In 2014 and 2015, the U.S. Geological Survey, at http://www.google.com/earth/index.html. in cooperation with USACE, collected suspended-sediment concentrations (SSCs) and turbidity measurements at approxi- Guy, H. P., 1969, Laboratory theory and methods for sediment mately 100 selected sites with the objectives of quantifying the analysis: U.S. Geological Survey Techniques of Water- horizontal and vertical distribution of SSC during placement Resources Investigations, book 5, chap. CI, 58 p. (Also of dredged material. These data are useful for evaluating the available at http://pubs.usgs.gov/twri/twri5c1/.) effectiveness of various dredged material placement configurations as well as the efficacy of a silt curtain in mitigating the Helsel, D.R., and Hirsch, R.M., 2002, Statistical methods in disbursement of suspended sediment. water resources—Hydrologic analysis and interpretation: Data collected in 2014 and 2015 were used to develop a U.S. Geological Survey Techniques of Water-Resources simple linear regression (SLR) model between SSC and tur- Investigations, book 4, chap. A3, 510 p., accessed Decem- bidity. The SLR model was used to generate an SLR equation ber 12, 2015, at http://pubs.usgs.gov/twri/twri4a3/. to predict SSC at each of the sites where turbidity measure- Host, G., Meysembourg, P., Reschke, C., Brady, V., Niemi, G., ments were collected in 2015. Using the predicted SSC Bracey, A., Johnson, L., James, M., Austin, J., and Butter- values, 12 three-dimensional visualization maps were gener- morem, E., 2013, An ecological design for the 21st Avenue ated to elucidate the distribution of SSC under four condi- West remediation-to-restoration project: Natural Resources tions: (1) before placement of dredged materials, (2) during Research Institute, NRRI/TR-2013/2014, 67 p. placement of dredged materials using four dredged-material placement configurations without a silt curtain, (3) during Koch, R.W., and Smillie, G.M., 1986, Bias in hydrologic placement of dredged materials with a silt curtain, and prediction using log-transformed regression models: (4) after placement of dredged materials ceased. Three-dimen- Journal of the American Water Resources Association, sional visualization maps are valuable for assessing the spatial v. 22, no. 5, p. 717–723. [Also available at http://dx.doi. displacement of suspended sediment during dredged material org/10.1111/j.1752-1688.1986.tb00744.x.] placements and provide an effective tool to support the design of projects requiring placement of dredged material in open Lietz, A.C., and Debiak, E.A., 2005, Development of rating water; such projects aid in the delisting of the lower St. Louis curve estimators for suspended-sediment concentration and River Estuary from the International Joint Commission’s transport in the C-51 canal based on surrogate technology, AOC. Palm Beach County, Florida, 2004–05: U.S. Geological Survey Open-File Report 2005–1394, 19 p., accessed March 2016 at http://pubs.usgs.gov/of/2005/1394/. LimnoTech, 2013, St. Louis River Area of Concern implemen- References Cited tation framework—Roadmap to delisting (remedial action plan update): accessed February 26, 2016, at https://www. pca.state.mn.us/sites/default/files/wq-ws4-02a.pdf. Baker, R.A., 1980, Contaminants and sediment—Volume 1, Fate and transport, case studies, modeling, toxicity: Ann Arbor, Mich., Ann Arbor Science, 558 p. References Cited 23

Lorenz, D.L., Sanocki, C.A., and Kocian, M.J., 2009, Tech- TIBCO Software Inc., 2010, TIBCO Spotfire S+: Boston, niques for estimating the magnitude and frequency of peak Massachusetts, accessed October 8, 2015, at http://spotfire. flows on small streams in Minnesota based on data through tibco.com/. water year 2005: U.S. Geological Survey Scientific Investi- gations Report 2009–5250, 54 p., accessed April 15, 2015, U.S. Army Corps of Engineers, 2016a, Channel Maintenance, at http://pubs.usgs.gov/sir/2009/5250/. accessed April 15, 2016 at http://www.mvp.usace.army.mil/ Missions/Navigation/ChannelMaintenance.aspx Miller, C.R., 1951, Analysis of flow-duration sediment rating curve method of computing sediment yield: U.S. Depart- U.S. Army Corps of Engineers, 2016b, Civil Works budget ment of Interior, Bureau of Reclamation, 55 p. of the U.S. Army Corps of Engineers, Fiscal Year 2017: accessed April 15, 2016, at http://cdm16021.contentdm. Minnesota Pollution Control Agency, 2009, Minnesota’s oclc.org/cdm/ref/collection/p16021coll6/id/42. impaired waters and total maximum daily loads (TMDLs): accessed February 26, 2016 at http://www.pca.state.mn.us/ U.S. Army Corps of Engineers, 2014, Environmental assess- water/tmdl/index.html. ment—Dredged material placement, 21st Avenue embayment, Duluth, Minnesota: accessed February 29, 2016, at Rasmussen, P.P., Gray, J.R., Glysson, G.D., and Ziegler, A.C., http://cdm16021.contentdm.oclc.org/cdm/ref/collection/ 2009, Guidelines and procedures for computing time-series p16021coll7/id/888. suspended-sediment concentration and loads from in-stream turbidity-sensor and streamflow data: U.S. Geological Sur- U.S. Census Bureau, 2016, Duluth, Minnesota and Superior, vey Techniques and Methods, book 3, chap. C4, 54 p. [Also Wisconsin populations: accessed January 31, 2016, at http:// available at http://pubs.usgs.gov/tm/tm3c4/.] www.census.gov/. Shelton, L.R., 1994, Field guide for collecting and process- U.S. Environmental Protection Agency, 2016, Great Lakes ing stream-water samples for the National Water-Quality Area of Concern: accessed January 31, 2016, at http://www. Assessment Program: U.S. Geological Survey Open-File epa.gov/great-lakes-aocs. Report 94–455, 42 p. [Also available at https://pubs.er.usgs. U.S. Geological Survey, 2016, National Water Information gov/publication/ofr94455.] System—USGS water data for the Nation [database]: St. Louis River Estuary, 2016, 21st Avenue West Restoration accessed April 14, 2016, at http://waterdata.usgs.gov/nwis/. Site: accessed January 30, 2016, at http://stlouisriverestuary. org/restoration_21w.php. The Nature Conservancy, 2016, Minnesota, St. Louis Estu- ary: accessed January 30, 2016, at http://www.nature.org/ ourinitiatives/regions/northamerica/unitedstates/minnesota/ placesweprotect/st-louis-river-estuary.xml.

Appendix 1 26 Three-Dimensional Visualization Maps of Suspended-Sediment Concentrations during Placement of Dredged Material

A summary of sampling sites at which suspended- Turbidity and SSC outliers collected during 2014 and sediment samples were collected and turbidity values were 2015 are provided in table 1–3. Outliers were not included in measured during 2014 and 2015 are provided in table 1–1. the simple linear regression model development. Table 1‒3 Approximately 230 suspended-sediment concentrations (SSC) is presented as a Microsoft Excel® spreadsheet (http://dx.doi. and corresponding turbidity values were used in simple linear org/10.3133/sir20165086). regression model development. Table 1‒1 is presented as a Microsoft Excel® spreadsheet (http://dx.doi.org/10.3133/ sir20165086). Table 1–3. Turbidity and suspended-sediment concentrations outliers collected in the 21st Avenue West Channel Embayment, Table 1–1. Summary of turbidity and suspended-sediment Duluth-Superior Harbor, 2014 through 2015. concentrations used for calibration of the simple linear regression model for sampled sites in the 21st Avenue West Channel Embayment, Duluth-Superior Harbor, 2014 through 2015. A summary of selected sampling sites at which turbidity was measured during 2015 is provided in table 1–4. This table also provides the predicted SSC values based on measured tur- Results of primary and sequential replicate samples for bidity values from 96 sites for 12 dates in 2015 that were used SSC collected during 2014 and 2015 are provided in table for generation of three-dimensional concentration maps.Table 1–2. This table also provides the relative percent difference 1‒4 is presented as a Microsoft Excel® spreadsheet (http:// between the primary and sequential replicate samples. dx.doi.org/10.3133/sir20165086). Table 1‒2 is presented as a Microsoft Excel® spreadsheet (http://dx.doi.org/10.3133/sir20165086). Table 1–4. Information on selected sampling sites in the 21st Avenue West Channel Embayment, Duluth-Superior Harbor, 2015, Table 1–2. Results of quality-assurance samples for suspended- and predicted suspended-sediment concentrations for 12 dates in sediment concentrations in the 21st Avenue West Channel 2015 during which turbidity was measured. Embayment, Duluth-Superior Harbor, 2014 through 2015.

Publishing support provided by: Rolla Publishing Service Center For more information concerning this publication, contact: Director, USGS Minnesota Water Science Center 2280 Woodale Drive Mounds View, Minnesota 55112 (763) 783–3100 Or visit the Minnesota Water Science Center Web site at: http://mn.water.usgs.gov/

Groten and others—Three-Dimensional Visualization Maps of Suspended-Sediment Concentrations during Placement of Dredged Material—Scientific Investigations Report 2016–5086 ISSN 2328-0328 (online) http://dx.doi.org/10.3133/sir20165086