Assessment Project Report

SIOUX FALLS TOTAL MAXIMUM DAILY LOAD ASSESSMENT PROJECT

Topical Report RSI-2014

prepared for

City of Sioux Falls Office of Public Works 224 Ninth Street Sioux Falls, South Dakota 57104-6407

October 2008

SIOUX FALLS TOTAL MAXIMUM DAILY LOAD ASSESSMENT PROJECT

Topical Report RSI-2014

Jared K. Oswald Lacy M. Pomarleau

RESPEC P.O. Box 725 Rapid City, South Dakota 57709-0725

prepared for

City of Sioux Falls Office of Public Works 224 Ninth Street Sioux Falls, South Dakota 57104-6407

October 2008

TABLE OF CONTENTS

1.0 NPS PROJECT SUMMARY SHEET ...... 1

2.0 STATEMENT OF NEED ...... 2 2.1 WATER-QUALITY PRIORITY...... 2 2.2 SIOUX FALLS TOTAL MAXIMUM DAILY LOAD PROJECT AREA BACKGROUND ...... 3 2.2.1 Big Sioux River Description ...... 3 2.2.2 Big Sioux River Uses...... 5 2.2.3 Baseline Data and Sources...... 6 2.3 PROJECT MAPS...... 8 2.4 GENERAL WATERSHED INFORMATION ...... 8 2.5 DESCRIPTION OF WATER-QUALITY PROBLEMS...... 15 2.5.1 Total Suspended Solids Initial Data Analysis Summary ...... 15 2.5.2 Fecal Coliform Bacteria Initial Data Analysis Summary...... 17

3.0 PROJECT DESCRIPTION...... 20 3.1 GOALS ...... 20 3.2 OBJECTIVES AND TASKS...... 21 3.3 ANTICIPATED SCHEDULE...... 42 3.4 SPECIAL PERMITS ...... 44 3.5 LEAD PROJECT SPONSOR ...... 44 3.6 BEST MANAGEMENT PRACTICES ...... 44

4.0 COORDINATION PLAN...... 45 4.1 PROJECT SPONSORS...... 45 4.2 LOCAL SUPPORT ...... 46 4.3 PROJECT COORDINATION...... 46 4.4 SIMILAR ACTIVITIES IN THE WATERSHED...... 46

5.0 EVALUATION AND MONITORING PLAN...... 47 5.1 FIELD DATA COLLECTION ...... 47 5.2 MONITORING STRATEGY...... 47 5.3 DATA MANAGEMENT, STORAGE, AND REPORTING...... 47 5.4 DESCRIPTION OF MODELS USED...... 49 5.5 LONG-TERM FUNDING PLANS FOR THE OPERATION AND MAINTENANCE OF RESTORATION ACTIVITIES...... 50

TABLE OF CONTENTS (Continued)

6.0 BUDGET...... 51

7.0 PUBLIC INVOLVEMENT ...... 55

8.0 REFERENCES...... 56

LIST OF TABLES

TABLE PAGE

2-1 Waterbodies Being Assessed in the Sioux Falls Total Maximum Daily Load Assessment Project and Corresponding Impairments Identified in the 2008 Integrated Report ...... 2 2-2 Numeric Criteria for Fecal Coliform and Total Suspended Solids Assigned to Beneficial Uses of Surface Waters in the Sioux Falls Total Maximum Daily Load Project Area...... 3 2-3 Public Recreation Areas Near the Sioux Falls Total Maximum Daily Load Project Area...... 6 2-4 Site List With Current Status...... 9 2-5 Land Area and Population of Counties in the Sioux Falls Total Maximum Daily Load Project Area ...... 14 2-6 Total Suspended Solids Concentration Grouped by Flow Regime at Key Sites ...... 16 2-7 Fecal Coliform Grouped by Season...... 18 3-1 Project Monitoring Site List With Recommended Changes ...... 25 3-2 Equipment and Sampling Needed for the Big Sioux River TMDL Project ...... 33 6-1 Complete Project Budget Summary ...... 52 6-2 Big Sioux River Monitoring Budget for Calendar Year 2009...... 54

iii

LIST OF FIGURES

FIGURE PAGE

2-1 Sioux Falls Total Maximum Daily Load Project Area ...... 4 2-2 Sioux Falls Drinking Water Source Distribution...... 5 2-3 Correlation Between Total Suspended Solids and Turbidity...... 7 2-4 Western Corn Belt Plains Ecoregion Including the Sioux Falls Total Maximum Daily Load Project Area ...... 10 2-5 Land Use Distribution Map of Sioux Falls Total Maximum Daily Load Project Area...... 12 2-6 Land Use Distribution in the Sioux Falls Total Maximum Daily Load Project Area...... 13 2-7 South Dakota Precipitation Normals for 1971–2002 ...... 13 2-8 South Dakota Growing Season Precipitation in Inches...... 14 2-9 Median Total Suspended Solids Concentration Grouped by Flow Regime at Key Sites...... 15 2-10 Median Fecal Coliform Concentration Grouped by Flow Regime at Key Sites ...... 18 3-1 Process Flow for the Big Sioux River Total Maximum Daily Load Development ...... 22 3-2 Sampling on the Big Sioux River, Three Key Tributaries, and the Diversion...... 23 3-3 Project Monitoring Site List With Recommended Changes ...... 26 3-4 Annual Hydrograph for BSR010 (USGS 06481000) ...... 27 3-5 Potential Monitoring Points for Urban Storm Drain Sampling...... 32 3-6 Graphic Comparison Example of Optimal Runoff Volume Capture Ratio and the Normalized Best Management Practice Design Volume (Depth) to Determine the MEP Design Depth ...... 37 3-7 Example Load Duration Curve for E. coli...... 38 3-8 Schedule for the Sioux Falls Total Maximum Daily Load Project...... 43 5-1 Thematic Layers of the ArcHydro Data Models...... 48

1.0 NPS PROJECT SUMMARY SHEET

AWARD FISCAL YEAR: 2009

PROJECT TITLE: Sioux Falls, TMDL Assessment Project

NAME, ADDRESS, PHONE AND E-MAIL OF LEAD PROJECT SPONSOR: City of Sioux Falls Department of Public Works-Engineering 224 W. Ninth Street Sioux Falls, South Dakota 57117-7402 Phone: 605.367.8601 Fax: 605.367.4310 Email: [email protected]

PROJECT TYPE: Watershed, I&E PROJECT LOCATION: Latitude 43°N Longitude 96°W

WATERSHED NAME: Lower Big Sioux River Watershed HYDROLOGIC UNIT CODE (HUC): 10170203

HIGH PRIORITY WATERSHED: Yes POLLUTANT TYPE: E. coli, Fecal Coliform, Total Suspended Solids (TSS)

TMDL DEVELOPMENT: Yes TMDL IMPLEMENTATION: No

UWA CATEGORY: 5 TMDL PRIORITY (High, Medium, Low): Medium/High

WATERBODY TYPES: River, Streams ECOREGION: Northwestern Great Plains

PROJECT CATEGORY: Agricultural/Urban GROUNDWATER PROTECTION: No

PROJECT FUNCTIONAL CATEGORY: Water-Quality Assessment/Monitoring

319 Funds: $350,400 Matching Funds: $233,600 Other Federal Funds: $55,000 Total Project Cost: $639,000

GOALS: The goals of this project are to: (1) assess the historic and existing health of the Big Sioux River from near Dell Rapids to just upstream of Brandon; (2) identify and allocate loads to the primary stressors that have led to the impairment of these reaches and listing in the 2008 South Dakota Integrated Report for Surface Water Quality Assessment (IR); (3) develop Total Maximum Daily Load (TMDL) reports for these reaches to specify the existing load, load capacity, and current departure from load capacity for the pollutants of concern, (4) identify best management practices (BMPs) that will restore beneficial uses in these reaches; and (5) provide information to the public and key stakeholders to increase watershed awareness and provide training sessions to appropriate management personnel.

PROJECT DESCRIPTION: The Lower Big Sioux River Watershed (LBSRW) is located in eastern South Dakota and drains approximately 2,195 square miles in South Dakota and an additional 1,120 square miles in Minnesota and Iowa. Within the LBSRW lies the Sioux Falls TMDL Assessment Project Area which includes the City of Sioux Falls, the state’s largest city. According to the South Dakota Department of Environment and Natural Resources (SD DENR) report titled 2008 South Dakota Integrated Report for Surface Water Quality Assessment (IR), there are 21 segments within the LBSRW listed as not supporting its assigned use of Immersion Recreation because of excessive fecal coliform bacteria [South Dakota Department of Environment and Natural Resources, 2008]. Five of these segments are on the Big Sioux River and are located in the Sioux Falls TMDL project area. These segments, which are impacted by runoff from the City of Sioux Falls and surrounding areas, are impaired for fecal coliform. These five stream segments are not currently listed as impaired for TSS; however, these reaches have historically been listed for TSS and likely continue to be impaired by sediment loads from stormwater effluent and other nonpoint sources. Therefore, fecal coliform (or Escherichia coli, E. coli) and TSS TMDLs will be developed for the five impaired stream segments in the Sioux Falls TMDL project area. A Sioux Falls TMDL Assessment Project report will be written summarizing the TMDLs developed for each impaired waterbody and the BMPs recommended for reducing pollutant loading throughout the project area.

This is a cooperative project with work to be completed by multiple agencies working together on multiple aspects of this project. Cooperators on this project include the City of Sioux Falls Public Works Department, USGS, and RESPEC. The City of Sioux Falls Public Works Department is primarily responsible for administration and project oversight; USGS is primarily responsible for continuous stream gauging; and RESPEC is primarily responsible for project management, field sampling and coordination, watershed model development, and information and education. The assessment and TMDL report will be initially developed by RESPEC and then edited collaboratively by each of the project partners and contributing agencies.

2.0 STATEMENT OF NEED

2.1 WATER-QUALITY PRIORITY

Pursuant to the requirements of the Federal Clean Water Act, SD DENR is required to develop Total Maximum Daily Loads (TMDLs) for all impaired waterbodies listed on the 2008 IR. In total, 21 stream segments in the Lower Big Sioux River Watershed (LBSRW) were listed as impaired in the 2008 IR. Five of the stream segments have previously or are currently being assessed as part of a TMDL project. The Sioux Falls TMDL assessment project will assess an additional five of the listed stream segments on the Big Sioux River (BSR). This project will specifically address water-quality impairments from the Big Sioux River near Dell Rapids (SD DENR Reach 8) to the Big Sioux River above Brandon (SD DENR Reach 12). The waterbodies being assessed in the Sioux Falls TMDL assessment project, along with the corresponding impairments and identified sources, are shown in Table 2-1. All waterbodies being assessed have been identified as U. S. Environmental Protection Agency (EPA) Category five stating that the water is impaired or threatened and a TMDL is needed. Based on the severity of the pollution and the beneficial uses, the waterbodies being assessed have been assigned by the SD DENR a water-quality priority of two, with the exception of Reach 8, which was assigned the highest water-quality priority of one.

Table 2-1. Waterbodies Being Assessed in the Sioux Falls Total Maximum Daily Load Assessment Project and Corresponding Impairments Identified in the 2008 Integrated Report

Waterbody Waterbody Location Impaired Cause Source I.D. Name Description Use

Near Dell Rapids to Immersion Fecal Livestock (Grazing or Feeding SD-BS-R-BIG_SIOUX-08 Big Sioux River Below Baltic Recreation Coliform Operations)

Below Baltic to Skunk Immersion Fecal Livestock (Grazing or Feeding SD-BS-R-BIG_SIOUX-09 Big Sioux River Creek Recreation Coliform Operations)

Skunk Creek to Immersion Fecal Residential Districts, Livestock SD-BS-R-BIG_SIOUX-10 Big Sioux River Diversion Recreation Coliform (Grazing or Feeding Operations)

Diversion Return to Municipal (Urbanized High Immersion Fecal SD-BS-R-BIG_SIOUX-11 Big Sioux River Sioux Falls Wastewater Density Area), Livestock Recreation Coliform Treatment Facility (Grazing or Feeding Operations)

Sioux Falls Wastewater Immersion Fecal Livestock (Grazing or Feeding SD-BS-R-BIG_SIOUX-12 Big Sioux River Treatment Facility to Recreation Coliform Operations) Above Brandon

The five stream segments in the Sioux Falls TMDL project area are listed in the 2008 IR as not supporting the assigned use of Immersion Recreation because of excessive fecal coliform bacteria [South Dakota Department of Environment and Natural Resources, 2008]. These segments are impacted by runoff from the City of Sioux Falls, South Dakota, and surrounding

areas. These segments are not listed as impaired for TSS; however, these reaches have historically been listed for TSS and will likely continue to be impaired by sediment loads from stormwater effluent and other nonpoint sources. The beneficial uses that have been assigned to impaired streams within the project area and the corresponding water-quality standards can be seen in Table 2-2.

Table 2-2. Numeric Criteria for Fecal Coliform and Total Suspended Solids Assigned to Beneficial Uses of Surface Waters in the Sioux Falls Total Maximum Daily Load Project Area

Numeric Criteria Beneficial Uses Fecal Coliform TSS (per 100 ml) (mg/l)

Domestic Water Supply (a) (a) Warmwater Semipermanent Fish Life Propagation (a) 90(b)/158(c)

Immersion Recreation 200m/400s (a)

(a) No established standards assigned to beneficial use. (b) 30-day average.

2.2 SIOUX FALLS TOTAL MAXIMUM DAILY LOAD PROJECT AREA BACKGROUND

The Sioux Falls TMDL project area is located within the lower portion of the BSR Watershed in 8-digit Hydrologic Unit Code (HUC) 1017020 and entirely within the state of South Dakota. The project area is approximately 194 square miles in size and encompasses the City of Sioux Falls in Minnehaha County. Other South Dakota counties included in the project area are Lincoln and Moody. The major tributaries of the Big Sioux River within the project area include Skunk Creek, Slip Up Creek, and Silver Creek. A map of the Sioux Falls TMDL project area is shown in Figure 2-1.

2.2.1 Big Sioux River Description

The BSR is a natural, permanent, stable river with several intermittent tributaries that only flow during snowmelt and rainfall events. The river rarely loses all flow, but the amount of discharge can be significantly impacted by wet-dry periods as well as stormwater runoff. There are many road crossings along the river that were channelized in some locations over time.

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Figure 2-1. Sioux Falls Total Maximum Daily Load Project Area.

2.2.2 Big Sioux River Uses

As illustrated in Figure 2-2, Sioux Falls uses both surface water and groundwater as the raw water supply for approximately 166,000 people [City of Sioux Falls Public Works Department, 2006]. In 2006, the BSR supplied the City of Sioux Falls with approximately 27 percent of its total water supply. The remaining 73 percent came from shallow aquifers, which also provide water to other regional residents. These aquifers are recharged by the BSR and its tributaries.

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Sioux Falls Source Water Distribution, 2006

Mi ddl e S k unk Split Rock Creek Creek Aquifer Aquifer 6.4% 1.3%

Big Sioux river 26.6%

Big Sioux Aquifer 65.7%

Middle Skunk Creek Aquifer Split Rock Creek Aquifer

Big Sioux river Big Sioux Aquifer

Figure 2-2. Sioux Falls Drinking Water Source Distribution [City of Sioux Falls Public Works Department, 2006].

The Big Sioux River is one of the most popular canoeing and kayaking rivers in South Dakota because of its slow current and meandering path [South Dakota Department of Game, Fish and Parks, 2008]. A variety of fishing opportunities also exists on the BSR. Smallmouth bass, bullhead, catfish, crappie, northern pike, sauger, and walleye all reside in the BSR. There are many state, county, and local parks in the project area which provide hiking, camping, canoeing, and fishing opportunities. Some of the prominent parks include the Big Sioux State Recreation Area, Aspen Park, and McHardy Park. Other public recreational areas near the project area are listed in Table 2-3.

Table 2-3. Public Recreation Areas Near the Sioux Falls Total Maximum Daily Load Project Area [East Dakota Water Development District, 2004]

County City Public Recreational Area

Lake Chester Brant Lake Access Area Big Sioux Recreation Area, City Parks–Aspen and Brandon McHardy Colton Colton City Park City Parks–Brown Memorial, Dell Rapids, and Dells of Dell Rapids the Sioux Palisades State Park Garretson Beaver Creek Nature Area Minnehaha Hartford Hartford City Park City Parks–Cherry Rock, Dunham, Elmwood, Falls, Fawick, Frank Olson, Great Bear, Kenny Anderson, Kuehn, Laurel Oak, Lewis, Lion’s Centennial, Sioux Falls McKennan, Morningside, Pioneer, Riverdale, Rotary, Sertoma, Spellerberg, Spencer, Terrace, Tomar, Tuthill, and Yankton Trail Outdoor Campus/Sertoma Butterfly House

2.2.3 Baseline Data and Sources

There has been a large amount of data collected in the past on the Big Sioux River and its tributaries in and near the Sioux Falls TMDL Project Area. Discharge and water-quality data were collected in the past by the U.S. Geological Survey (USGS), SD DENR, City of Sioux Falls, East Dakota Water Development District (EDWDD), and others. The City of Sioux Falls collects water samples to verify compliance of point source discharges with the federal National Pollutant Discharge Elimination System (NPDES).

EDWDD was previously contracted by the SD DENR under 319 grant funds to perform water-quality assessments on the Big Sioux River and its tributaries (e.g., Silver Creek, Slip Up Creek, and Skunk Creek) between Brookings and Brandon. The monitoring project included: chemical analysis on BSR and its tributaries, macro-invertebrate monitoring on the BSR and its tributaries, fish habitat studies on Slip Up Creek and Skunk Creek, collection of USGS flow data on the BSR, and setting up flow hydro meters on the BSR tributaries to include instantaneous readings and calculated flows. A final TMDL was not accepted for the project area.

The USGS currently has four active and three historic streamflow gauging stations from which discharge data can be obtained, as well as two sites where continuous water-quality data

are being collected. Continuous water-quality parameters include conductivity, dissolved oxygen, pH, turbidity, and water temperature. Some work previously completed by the USGS looked at the relation between turbidity and TSS. Work was also completed in other parts of the nation relating turbidity measurements to bacteria concentrations. Figure 2-3 shows the correlation between turbidity and TSS for sites with paired data in the Sioux Falls TMDL project area. The graph displays strong correlation (R2=0.79) between TSS and turbidity values when plotted on a natural log scale. Note that individual stations show stronger correlations. Poor correlation at the lower end is likely because of slight calibration errors or drift when using the turbidity probe (natural logs of turbidity on the x-axis below about 2.3 represent turbidity values of about 0 to 10). Continuous turbidity data would be correlated with results from TSS samples to develop continuous estimated TSS loading information and to further narrow down BMP choices and methods by evaluating effects of individual BMPs to predicted TSS loading. If these relations hold, the continuous water-quality data can provide great insights into the variability of these two parameters during the various flow regimes.

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Turbidity Vs TSS Natural Log

8 7 6 5

4 y = 0.885x + 1.0233 3 R2 = 0.7925 2 TSS, log natural 1 0 012345678 Turbidity, natural log

TSS, Natural Log Linear (TSS, Natural Log)

Figure 2-3. Correlation Between Total Suspended Solids and Turbidity.

Historical USGS streamflow and water-quality data are also available for retrieval through the USGS National Information System (NWIS) Web pages. Some water-quality data of interest would include results from stormwater runoff studies in 1995–1996 [Niehus, 1997] and sampling for the occurrence of organic wastewater compounds in 2001–2004 [Sando et al., 2006].

The SD DENR Ambient Monitoring Program also collects water-quality data from six locations along the BSR and one location on Skunk Creek in the study area. Monthly to quarterly samples are collected at these sites and include TSS and fecal coliform. The data are available from SD DENR as well as from the EPA database Storage and Retrieval (STORET). A summary of known monitoring data is listed in Table 2-4.

2.3 PROJECT MAPS

Project maps are shown throughout the document.

2.4 GENERAL WATERSHED INFORMATION

The boundaries of this project lie in the Loess Prairies (Level IV) of the Western Corn Belt Plains ecoregion (Level III) (Figure 2-4). Land elevation ranges from 1,200 to 1,700 feet. The geology in the region is characterized as Loess deposits over Cretaceous sandstone, shale, and Sioux Quartzite. The Precambrian Sioux Quartzite is exposed in several sections of the river valley throughout the project boundaries which provides a quartzite substrate that enhances habitat for aquatic life.

Glacial drift covers the Cretaceous formations. Glacial drift can be separated into till, outwash, and lake deposits. The principal glacial drift is glacial till which is an assortment of silt, sand, and large rock fragments surrounded by clay. Within the small depressions of the glacial till areas, glacial lake sediments can be found. Glacial lake sediments are made of clay and silt with a thickness ranging from 4 to 10 feet. Glacial outwash is composed of gravel, sand, and silt and is typically found in the valleys and plains of the basin. Newer alluvial deposits consisting of clay, silt, sand, and some gravel have recently been deposited along the edges of the Big Sioux River as well as its tributaries. These alluvial deposits are generally 3 to 15 feet thick.

A variety of parent materials have derived the soils within the Sioux Falls TMDL project area. The fine-grained upland soils have built up over glacial till or eolian (Loess) deposits. Coarse-grained soils that were derived from glacial outwash and alluvial sediments can be found near present and past water courses. Near Dell Rapids, there is a noticeable shift to highly erodible soils. Moody, Nora, and Trent soil series are common within the project area.

The natural vegetation in the project area is tallgrass prairie including big and little bluestem, indiangrass, and green needlegrass. On the steeper slopes in the southern part of the project area, needlethread, prairie dropseed, and deciduous woodland are common.

Table 2-4. Site List With Current Status

Site I.D. Alias(es) Name Current Status

06481000, 460703, Water- Active USGS Real-Time Discharge Big Sioux River Near BSR010 Quality Monitoring and Water Quality, Active SD DENR Dell Rapids (WQM) 3, R8MBSR WQM, Discontinued EDWDD Site

Big Sioux River I-90 Bridge Active SD DENR WQM, Active Sioux BSR020 46BS23, BS23, 26C Upstream of Sioux Falls Falls Monitoring

Big Sioux River at Silver Discontinued EDWDD Monitoring BSR030 R9MBSR Creek Site

Active Monitoring by the City of WPT010 Water Treatment Intake Water Treatment Intake Sioux Falls

Big Sioux River Below USGS Real-Time Stage, Peakflow BSR040 06481400 Diversion at Sioux Falls Discharge

Active USGS Real-Time Discharge, 06481500, 460121, Skunk Creek at Marion Road Active DENR WQM, Active Sioux SKC030 WMQ 121, 26D, T23SKCK Bridge at Sioux Falls Falls Monitoring, Active EDWDD Site

Big Sioux River at I-229 Discontinued EDWDD Monitoring BSR050 R10MBSR Bridge Site

Big Sioux River Near South USGS Real-Time Stage, Peakflow BSR060 06482000 Western Avenue Bridge at Discharge, Active EDWDD Sioux Falls Monitoring Site

Big Sioux River From Skunk BSR070 460664, WQM 64 Active DENR WQM Creek to Diversion Return

JMC010 John Morrell & Co. NPDES Discharge Location NPDES Monitoring

Silver Creek 259 Street Discontinued EDWDD Monitoring SVC010 T24SVRC Bridge Site

USGS Real-Time Stage, Peakflow SVC020 06482010 Silver Creek at Sioux Falls Discharge

Active USGS Real-Time Discharge Big Sioux River at North Cliff BSR080 06482020, R11MBSR and Water Quality, Discontinued at Sioux Falls EDWDD

Big Sioux River at Bahnson Active DENR WQM, Active Sioux BSR090 46BS29, BS29, 26A Avenue Bridge Falls Monitoring

Sioux Falls Waste Water SFW010 NPDES Discharge Location NPDES Monitoring Treatment Plant

Slip Up Creek 477 Avenue Discontinued EDWDD Monitoring SUC010 SLPCK010 Bridge Site

Big Sioux River at Bridge Active DENR WQM, Active Sioux BSR100 460117, WQM 117, 26B Downstream of Slip Up Creek Falls Monitoring

Discontinued USGS Discharge, 06482100, 460831, BSR110 Big Sioux River Near Brandon Active SD DENR WQM, WQM 31, R12MBSR Discontinued EDWDD `

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Figure 2-4. Western Corn Belt Plains Ecoregion Including the Sioux Falls Total Maximum Daily Load Project Area.

Developments have changed the watershed to include a vast array of agricultural areas as well as urban and residential areas (Figure 2-5). Land use in the project area is predominantly agricultural. Approximately 45 percent of the area is cultivated cropland, predominantly corn and soybeans; 20 percent is pasture and hay land; and 26 percent is developed to various extents (Figure 2-6). There are approximately 70 animal feeding operations that encompass 134 acres of the project area. A total livestock count of 10,548 was reported by East Dakota Water Development District [2008]. Of the total livestock, 70 percent were beef cattle, 24 percent were pigs, 6 percent were dairy cows, and the remaining 0.25 percent consisted of sheep and horses. The land within the project area is predominately private land with a very small area dedicated to a South Dakota Game, Fish and Parks game production area.

The watershed level processes have undergone extensive modifications because of developmental changes. One major modification is the increase in overland flow as a result of decreased groundwater infiltration and subsurface recharge. Increases in nonpoint source transport of sediment, nutrients, agricultural and residential chemicals, and feedlot runoffs have been linked to increased surface runoff. There are currently eight surface water discharge permits within the cities of Dell Rapids, Baltic, and Sioux Falls which enhanced runoff into the BSR. One of the special wastewater discharge (SWD) permits is issued to the City of Sioux Falls which is classified as a Phase 1 stormwater community and received a Municipal Separate Storm Sewer System (MS4) permit in 1999.

Whitetail deer, turtles, waterfowl, and numerous songbirds can be seen along the Big Sioux River [South Dakota Game, Fish and Parks, 2008]. The following threatened-and-endangered species and candidates for that designation are identified by the South Dakota Game, Fish and Parks as located within the counties of the watershed: Whooping Crane, Bald Eagle, Topeka Shiner, Central Mudminnow, Trout Perch, Northern Redbelly Dace, American Burying Beetle, Dakota Skipper, Regal Fritillary, Western Prairie Fringed Orchid, Blanding’s Turtle, Spiny Softshell Turtle, Northern Redbelly Snake, Lined Snake, and the Black-Footed Ferret. The implementation of this assessment project will not impact any of these species.

The Sioux Falls TMDL project area receives 73 percent of its average annual precipitation— 24.7 inches—during the growing season of April through September (Figure 2-7 and Figure 2-8) [South Dakota State University, 2008]. Local storms with short durations often produce heavy rainfall events. These storms can elevate to severe thunderstorms and occasionally produce tornados. The average seasonal snowfall is 41.1 inches per year [U.S. Department of Commerce National Climatic Data Center, 2004].

The Sioux Falls TMDL project area is centered in a densely populated region of South Dakota. Sioux Falls is the largest city in the state of South Dakota. Sioux Falls is located in Minnehaha County, the most densely populated county in the state, with Lincoln County being the second most densely populated county. Towns directly in the project area include Sioux

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Figure 2-5. Land Use Distribution Map of Sioux Falls Total Maximum Daily Load Project Area.

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Land Use Distribution in the Sioux Falls TMDL Project Area

Emergent Herbaceous Wetlands, 1.03% Open Water, 0.60% Developed, Open Space, 12.21% Woody Wetlands, 0.04%

Developed, Low Intensity, 7.16%

Developed, Med. Inte ns ity, 4 .3 1 %

Developed, High Intensity, 2.45%

Barren Land (Rock/Sand/Clay) Cultivated Crops, 45.26% 0.27%

Deciduous Forest, 2.52%

Evergreen Forest, 0.00%

Shrub/Scrub, 0.02%

Grassland/Herbaceous, 3.77% Pasture/Hay, 20.37%

Figure 2-6. Land Use Distribution in the Sioux Falls Total Maximum Daily Load Project Area.

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Figure 2-7. South Dakota Precipitation Normals for 1971–2002 [South Dakota State University, 2008].

Falls, Dell Rapids, and Baltic in Minnehaha County. Other towns in close proximity to the project area include: Garretson, Colton, Sherman, Brandon, Crooks, Hartford, Rowena, and Valley Springs all within Minnehaha County; Chester in Lake County; Trent in Moody County; as well as Tea and Harrisburg in Lincoln County. The City of Sioux Falls and several surrounding communities have undergone considerable growth and urban development in recent years. Information for each county in the study area including land area, population density, and the 2004 Census population are shown in Table 2-5.

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Figure 2-8. South Dakota Growing Season Precipitation in Inches [South Dakota State University, 2008].

Table 2-5. Land Area and Population of Counties in the Sioux Falls Total Maximum Daily Load Project Area

Size Population Density County Population (mi2) (people/mi2)

Minnehaha 159,893 813.7 196.5 Lincoln 29,819 578.6 51.5 Moody 6,615 521.1 12.7

2.5 DESCRIPTION OF WATER-QUALITY PROBLEMS

The following discussion summarizes RESPEC’s initial data analysis for the Sioux Falls TMDL Project Area.

2.5.1 Total Suspended Solids Initial Data Analysis Summary

TSS in the Big Sioux River follows a typical pattern for streams in South Dakota. TSS concentrations are low during low flow and almost always meet the water-quality criteria. As flows increase, TSS concentrations increase accordingly, with most exceedances occurring during high flow periods. This pattern also holds for the major tributaries entering the Big Sioux River in the Sioux Falls area. Figure 2-9 shows the median concentration by flow regime, while Table 2-6 provides the median TSS concentrations and percent exceedances by season. It should be noted that the number of samples listed in Table 2-6 is different for some sites than the number of samples used in the analysis by flow regime, since paired flow and water-quality data were not present for all stations. For many stations, no flow data were available at the sampling location, so flow data were applied from the nearest gauge station that could provide reasonably accurate estimates.

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Median TSS Concentration Grouped by Flow Regime

1000

l Al l Flows High Flows 100 Mid Fl ows TSS mg/ TSS Low Fl ows

0 0 3 80 02 010 0 C C0 C R R090 C010 R100 K K SR 070 V S S U BSR010BSR020BSR030S S BSR050B S B B S BS

Figure 2-9. Median Total Suspended Solids Concentration Grouped by Flow Regime at Key Sites.

Table 2-6. Total Suspended Solids Concentration Grouped by Flow Regime at Key Sites

Total Spring Summer Fall Winter Site I.D. Samples n Median % Median % Median % Median % n n n n (mg/l) Exceedance (mg/l) Exceedance (mg/l) Exceedance (mg/l) Exceedance

BSR010 410 144 69.5 8 105 86.0 3 64 39.0 3 97 9.0 3

BSR020 834 343 74.0 9 273 72.0 6 165 47.0 1 53 13.0 0

BSR030 15 6 177.0 50 7 116.0 14 2 19.5 0 0 0.0 0

SKC020 36 17 69.0 18 14 91.5 21 5 37.0 0 0 0.0 0

SKC030 130 50 69.0 12 35 93.0 23 27 42.0 7 18 11.5 6

16 BSR050 34 16 59.5 19 13 76.0 15 5 51.0 0 0 0.0 0

BSR070 389 133 66.0 12 97 80.0 3 61 31.0 2 98 10.0 0

SVC010 11 6 31.5 17 4 3.5 0 1 70.0 0 0 0.0 0

BSR080 41 14 67.0 29 15 66.0 7 6 32.0 0 6 6.5 0

BSR090 804 272 66.2 12 205 67.0 9 134 36.7 1 193 11.0 1

SUC010 17 8 270.0 63 7 53.0 29 2 18.5 0 0 0.0 0

BSR100 1,088 373 66.0 14 273 60.0 9 183 36.0 2 259 10.0 0

BSR110 404 141 92.0 23 102 81.0 14 62 34.0 5 99 15.0 0

TSS concentrations appear to be fairly constant between BSR010 (near Baltic) and BSR020 (at I-90). The data show an increase between BSR020 and BSR030 (at the diversion); however, it is unlikely that there is a significant change in water quality between these two stations and that the difference in concentration data is more likely caused by the differences in sample size (n=834 at BSR020 compared to n=15 at BSR030). Based on the data, TSS concentrations do not appear to increase significantly along the urban stream corridor, upstream of the diversion reentry. The river reach from the diversion downstream to BSR100 (just downstream of Slip Up Creek) has the highest concentrations during high flows according to available data. It should be noted that BSR110 (near Brandon) does not have associated flow data and is not shown on Figure 2-9. Slip Up Creek appears to have higher TSS concentrations during the spring and during high flow periods than the Big Sioux River and may be one source of impairment. Again, the small sample size on Slip Up Creek (n=17) makes it difficult to formulate clear conclusions.

2.5.2 Fecal Coliform Bacteria Initial Data Analysis Summary

Figure 2-10 shows median fecal coliform concentrations grouped by flow regime at key tributary and Big Sioux River sampling sites for samples collected during the recreation season. Table 2-7 gives median and percent exceedances for samples broken out by recreation period and nonrecreation period. Fecal coliform concentrations are about equal at the two sites upstream of the diversion, with a slight decrease from BSR010 to BSR020 in percent exceedance and median concentrations during the recreation season. Similar to the pattern seen for TSS, BSR030 concentrations in the river are higher than BSR020 (50 percent exceedance and a median of 395 colony-forming units per 100 milliters (cfu/100 ml)), which again is probably a function of sample size (n=10 during the recreation season). Fecal coliform concentrations generally increase through the city to BSR070 (just upstream of the diversion). BSR020 has a median concentration of 200 cfu/100 ml and 26 percent exceedance, while BSR070 has a median concentration of 400 cfu/100 ml and 48 percent exceedance. Most of this increase appears to be during high flow events; concentrations actually appear to be lower through the city during low flows. It appears that coliform concentrations in Skunk Creek are about equal to those in the Big Sioux River. Median concentrations across the diversion reentry (from BSR070 to BSR080) jump nearly fivefold while exceedances increase from 48 percent to 62 percent, suggesting that the diversion area is contributing a fecal coliform load, possibly from the addition of Silver Creek to the diversion. It is difficult to account for the jump in median concentration downstream of the diversion reentry (BSR080) based on data from Silver Creek since there is a large difference in the number of samples collected at these sites (n=7 at SVC010, n=151 at BSR070, and n=69 at BSR080). At BSR080, concentrations are high (median of 1,300 cfu/100 ml in the recreation season with a 62 percent exceedance) compared to data from BSR090 just downstream (median of 314 cfu/100 ml in the recreation season with a 43 percent exceedance), most likely because of a difference in the period of record for sampling (the majority of samples collected at BSR080 were collected during the 1970s while sampling has been constant at BSR090 since the mid-1970s).

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Median Fecal Coliform Concentration Grouped by Flow Regime

100000

l 10000 Al l Flows High Flows 1000 Mid Flows Low Flows

cfu per 100 m per 100 cfu 100

30 50 10 80 10 0 0 0 0 R020 C020 C030 R070 C0 R090 C S K K S S BSR010 B BSR S S BSR B SV BSR B SU BSR100

Figure 2-10. Median Fecal Coliform Concentration Grouped by Flow Regime at Key Sites.

Table 2-7. Fecal Coliform Grouped by Season

Nonrecreational Recreational Total Site I.D. Samples % n Median % Median n n Exceedanc (cfu/100 ml)(a) Exceedance (cfu/100 ml)(a) e

BSR010 421 195 60 13 226 230 35

BSR020 701 260 43 9 441 200 26

BSR030 15 5 170 40 10 395 50

SKC020 36 13 100 31 23 310 39

SKC030 81 34 50 15 47 320 45

BSR050 34 12 110 33 22 415 50

BSR070 277 126 40 13 151 400 48

SVC010 11 4 3,075 50 7 340 43

BSR080 126 57 2,200 68 69 1,300 62

BSR090 686 368 53 17 318 313.5 43

SUC010 17 6 1,750 83 11 4,200 100

BSR100 954 517 260 36 437 286 37

BSR110 295 134 160 36 161 330 45

(a) cfu/100 ml = colony-forming units per 100 milliliters.

Slip Up Creek (SUC010) appears to contribute a large coliform load just downstream of the Waste Water Treatment Plant, although the number of samples (n=9) is too low to bear any statistical significance. Because of the limited number of sample collection sites, the lack of data at urban stormwater outfalls, and the limited number of samples at some key sites, it is difficult to determine the source of waters bearing high concentrations of fecal coliform bacteria. In general, throughout the Sioux Falls area, median concentrations go down as sample sizes go up.

3.0 PROJECT DESCRIPTION

3.1 GOALS

The goals of the Sioux Falls TMDL Assessment Project are listed below:

1. Assess the historic and existing health of the Big Sioux River from near Dell Rapids to just upstream of Brandon.

2. Identify and allocate loads to the primary stressors that have led to the impairment of these reaches and listing in the 2008 IR [South Dakota Department of Environment and Natural Resources, 2008].

3. Develop TMDL reports for these reaches to specify the existing load, load capacity, and current departure from load capacity for the pollutants of concern.

4. Identify BMPs that will restore beneficial uses in these reaches.

5. Provide information to the public and key stakeholders to increase watershed awareness and provide training sessions to appropriate management personnel.

TMDLs consider all loading sources, which can be generally categorized into permitted point and MS4 sources (waste load allocations (WLAs)), nonpoint sources (load allocations (LA)), and a margin of safety (MOS). It is also important to recognize that there is some level of background (or natural) loading in all systems. Background load is usually incorporated into the allowable LA for nonpoint sources. It is important to understand the natural background to ensure the TMDL is feasible.

NPDES-regulated stormwater discharges must be addressed by the WLA component of a TMDL. WLAs are established to meet “water-quality-based effluent limitations.” Simply stated, this means the WLA must meet the established beneficial use criteria at the point of discharge. The level of stormwater-quality control is also defined in the federal regulations in terms of the maximum extent practicable (MEP). MEP takes into consideration the practicality (economics) of trying to treat low-frequency (very large) events and recognizes that the majority of stormwater loadings are generated by the frequent, smaller events. There are a few key publications that have provided guidance on the determination of the MEP, which are based on rainfall characteristics and the level of watershed development [Urbonas et al., 1990; Roesner et al., 1991; Urbonas and Stahre, 1993]. What becomes important is that the development of the TMDL incorporates the WLA based on the load reduction achieved by implementing the MEP. Additionally, it is important to understand recent policy that states:

“Water-Quality Based Effluent Limitations for NPDES-regulated stormwater discharges that implement WLAs in TMDLs may be expressed in the form of BMPs under specified

circumstances (See 33 U.S.C. §1342(p)(3)(B)(iii); 40 C.F.R. §122.44(k)(2)&(3)). If BMPs alone adequately implement the WLAs, then additional controls are not necessary.”

The basic meaning of this policy is that specification and implementation of BMPs to reduce stormwater loadings must meet the TMDL WLA. Thus if the TMDL is developed by incorporating BMPs that are sized based on the MEP, the TMDL should be met and beneficial uses attained. This is considered a performance-based approach in that if the BMPs are designed and implemented appropriately, the water-quality standards should be achieved.

TMDLs need to be completed for fecal coliform (or E. coli) bacteria and total suspended solids for the five identified stream segments of the Big Sioux River (Table 2-1). An E.coli TMDL may be done in lieu of a fecal coliform TMDL based on direction from the SD DENR. The approach to develop the BSR TMDLs is shown in Figure 3-1. The primary tasks included in this process are:

1. Developing and implementing a water-quality monitoring plan for data acquisition.

2. Determining the stormwater treatment capability of the City (i.e., the MEP).

3. Determining the existing load, the loading capacity (i.e., the TMDL) of the waterbodies and the existing departure from the TMDL.

4. Allocating the TMDL to the LA and WLA components.

5. Analyzing the BMP (including stormwater treatment) implementation scenarios.

3.2 OBJECTIVES AND TASKS

Objective 1: Develop Budgets for Water-Quality Constituents Listed as Impaired in the Sioux Falls TMDL Project Area and Recommend BMPs for Pollutant Load Reduction.

Task 1: Develop and Implement a Water-Quality Monitoring Plan for Data Acqui- sition

The monitoring plan selected is based on information presented in Love [2008] and a meeting with key project team members held in Pierre, South Dakota, on September 11, 2008.

There are four key components to the success of this monitoring plan: (1) increasing the sampling on the Big Sioux River, including both additional water-quality sampling and increased monitoring of river discharge; (2) sampling on the three key tributaries; (3) understanding the flow being diverted around the Sioux Falls area through the diversion canal; and (4) sampling stormwater runoff within the storm drainage network in Sioux Falls. Table 2-4 lists the existing monitoring sites, along with their current status, and Figure 3-2 shows their locations.

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Figure 3-1. Process Flow for the Big Sioux River Total Maximum Daily Load Development.

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Figure 3-2. Sampling on the Big Sioux River, Three Key Tributaries, and the Diversion.

The following list presents key assumptions made while developing the monitoring plan and budget:

• One season of sampling is proposed (beginning March 2009 and extending through November 2009). In September 2009, the project team will evaluate the need to conduct an additional year of monitoring; i.e., March 2010 through November 2010. If an additional year of monitoring is deemed necessary, additional funding will be required and the scheduled end of the project will be extended from December 31, 2010, to June 30, 2011.

• The monitoring and current status of the USGS gauges will remain unchanged. Water- quality monitoring at SD DENR WQM sites will remain unchanged; real-time stage recorders will be installed by the SD DENR at each of their WQM sites in the Sioux Falls area.

• The monitoring performed by RESPEC as part of this project will be done in lieu of the City of Sioux Falls NPDES Stormwater Program monitoring, and some of the city’s equipment (e.g., six ISCO sampling units) will be available to this project. This equipment will be leased to the project and shown as in-kind cost share.

• Equipment from the SD DENR would be used in some locations at no cost to the project, including an Acoustic Doppler Stream Profiler for discharge measurements.

• The constituents analyzed will be fecal coliform bacteria, E. coli, and TSS. The bacteriological analysis will be performed by the City of Sioux Falls Health Laboratory. The TSS analysis will be performed by the City of Sioux Falls Water Reclamation Laboratory. Both the bacteriological and TSS analysis will be shown as in-kind cost share.

• Fifty percent of the water-quality samples collected at urban storm drain sites will undergo deoxyribonucleic acid (DNA) source tracking, testing for the presence/absence of human bacteria source indicators. RESPEC will hire two professional associates as subcontractors located in the Sioux Falls area to locally lead the monitoring program.

Task 1.1: Sampling on the Big Sioux River, Three Key Tributaries, and the Diversion

Table 3-1 gives a summary of changes to current monitoring on the Big Sioux River, three key tributaries, and the diversion that would be necessary to effectively implement this monitoring plan. Figure 3-3 shows the locations and recommended changes.

Task 1.1.1: Continuous Flow

Continuous stage will be collected at all nine sites shown in Table 3-1. SKC030, BSR060, and BSR080 are active USGS gauges that currently collect stage data and provide estimates of flow real-time. However, the rating curve at BSR060 is not maintained and the flow estimates have significant uncertainty. Discharge should be measured a sufficient number of times over a range of flows at BSR060 to evaluate/modify the existing stage-discharge relationship.

Table 3-1. Project Monitoring Site List With Recommended Changes

Continuous Continuous Storm Event Weekly Flow Water Sampling Site I.D. Name Sampling (Stage Quality (Grab and (Grab) Recorder) (YSI) ISCO)

Big Sioux River I-90 BSR020 Bridge Upstream of Y Y Y Y Sioux Falls

Big Sioux River at Silver BSR030 Y N N N Creek

Skunk Creek at Marion SKC030 Road Bridge at Sioux N N Y Y Falls

Big Sioux River Near BSR060 South Western Avenue N N Y Y Bridge at Sioux Falls

SVC015 Silver Creek Near I-90 Y N Y Y

DIV010 Diversion Y N N N

Big Sioux River at North BSR080 N N Y Y Cliff at Sioux Falls

Slip Up Creek Upstream SUC020 of Confluence With Big Y N Y Y Sioux

Big Sioux River Near BSR110 Y N Y Y Brandon

BSR030 and DIV010 are located at the diversion check structure and a weir within the diversion, respectively. Once equipped with a stage-recording device and data logger, standard hydraulic equations can be used to provide continuous estimates of flow at these sites.

The other four sites in Table 3-1 will require stage-recording equipment to be installed and stage-discharge curves to be developed to convert the continuous stage to flow. Discharge should be measured a sufficient number of times over a range of flows to create the stage- discharge relationships at each site. Discharge will be measured frequently early in the year after ice-out to quickly develop these curves and to take advantage of the wide range of flows seen as the snowpack melts. Figure 3-4 provides the average annual hydrograph from BSR010 (USGS 06481000 Big Sioux River near Dell Rapids, South Dakota) based on daily data from 1948 through present. Equipment from SD DENR would be used in some locations, including an Acoustic Doppler Stream Pro for discharge measurements. An existing HEC-RAS model, the HSPF model, and other nearby USGS gauges will also provide/verify discharge estimates at these locations.

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Figure 3-3. Project Monitoring Site List With Recommended Changes.

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Station 06481000

4 02/19 04/09 05/29 07/18 09/06 10/26 12/15 10 25th Percentile 50th Percentile 75th Percentile

3 10

2 10 Flow (cfs) Flow

1 10

0 10 50 100 150 200 250 300 350 Day of Year

Figure 3-4. Annual Hydrograph for BSR010 (USGS 06481000).

Task 1.1.2: Continuous Water Quality

A DENR water-quality sonde will be installed at BSR020 and to collect continuous temperature, dissolved oxygen, conductivity, turbidity, and pH data. Continuous turbidity data will be correlated with results from TSS samples to develop a continuous estimate of TSS loads entering the Sioux Falls area from upstream nonurban sources.

Task 1.1.3: Storm Event Sampling

ISCO automatic samplers will be installed at seven locations along the Big Sioux River and the three key tributaries with the intent to concurrently collect a minimum of six storm events (see Table 3-1 and Figure 3-2). These ISCOs will be housed in semipermanent structures and equipped with cell phone modems allowing remote triggering during runoff events. Each ISCO sampler would be equipped with sequential sample bottles, allowing samples to be composited based on incremental flow volume. Stage and discharge data from the event will be used to composite samples based on flow volume to make a single sample. Results from composite sample analysis will yield the event mean concentration (EMC). Samples collected using ISCOs will be analyzed for TSS, fecal coliform bacteria, and E. coli. A grab sample will also be collected concurrently for each event at each site. Also, one depth-integrated sample using an equal-width increment method will be collected at each ISCO site per year.

Quality assurance/quality control (QA/QC) procedures will be implemented to reduce known problems with analyzing bacteria with ISCO samplers. The grab, ISCO-composited, and integrated samples will be compared in an attempt to quantify differences and potential bias associated with the different sampling methods. Weekly visits to each site will be made to evaluate/maintain the sampling equipment.

Task 1.1.4: Weekly Grab Sampling

Weekly grab samples will be collected from the same seven ISCO sites to characterize the typical conditions seen in the system (see Table 3-1 and Figure 3-2). These samples will be initially nonspecific in the flow regime they are targeting and based solely on a predetermined schedule of days to sample. However, if it appears that either too many storms or baseflow events are being sampled, the schedule will be adjusted to reduce any bias in the dataset. These samples will be collected concurrently with weekly maintenance being performed on equipment at the stations.

Task 1.1.5: Recommended Changes by Site

The following list details site changes on the Big Sioux River required for this monitoring plan. At current USGS and SD DENR monitoring sites not listed here, sampling efforts would continue at their current level.

BSR020. It is recommended that a cell-phone-triggered ISCO automatic sampler coupled with a water-quality sonde and stage-recording device be installed at this site, weekly and

event grab samples be collected, and a stage/discharge relationship be developed by measuring flows during grab sampling and during high flow events.

BSR030. Continuous discharge is important to monitor the operation of the diversion canal. The flow that remains in the Big Sioux River and passes through the diversion gate structure on the Big Sioux River can be monitored by placing a pressure transducer connected to a continuously recording data logger. Additionally, the number of gates open along with the amount they are open will be recorded automatically by placing potentiometers on the gates and coupling them with a data logger. Once all data are collected, flow can be calculated using the following equation:

= ()0.5 QCabghdo2 (3-1) where:

Q =discharge in ft3 /s = Cd discharge coefficient a =sluice gate opening in feet

b =sluice gate width in feet g =gravitational acceleration in feet per second = ho upstream water depth above the invert in feet.

SKC030. Skunk Creek has a long-term discharge gauging station (USGS) and a coinciding water-quality sampling station (DENR and City of Sioux Falls) near its confluence with the Big Sioux River. It is recommended that a cell-phone-triggered ISCO automatic sampler be installed at this site and weekly and event grab samples be collected.

BSR060. This station is currently a USGS real-time stage site; however, the rating curve at this site is not maintained. It is, therefore, recommended that a cell-phone-triggered ISCO automatic sampler be installed at this site, weekly and event grab samples be collected, and the existing stage/discharge relationship be verified/modified by measuring flows during grab sampling and during high flow events.

SVC015. The USGS currently operates a peak flow discharge monitoring station on Silver Creek (SVC020 on Figure 3-2); however, this site is prone to backwater effects from the diversion canal. Sampling on Silver Creek should take place at SVC015 (Figure 3-3) since it is further upstream and will not be affected by the diversion canal. It is recommended that a cell- phone-triggered ISCO automatic sampler coupled with a stage-recording device be installed at SVC015, baseline grab and event samples be collected, and a stage/discharge relationship be developed by measuring flows during grab sampling and during high flow events.

DIV010. Flow in the diversion canal and in the Big Sioux River below the diversion needs to be monitored with more accuracy than the methods currently being used. Flow that passes through the diversion canal can be estimated by converting stage data collected by a stage- recording device installed upstream of the dam located just downstream from the confluence of Silver Creek (Station DIV010 on Figure 3-3). Stage data would be input to an equation similar to Equation 3-2 for standard fully contracted weirs once the dimensions of the dam are known.

QhLh=××−×3.3332÷ () 0.2 (3-2) where:

Qs= discharge in feet3 per neglecting velocity of approach L = the length of weir in feet h = head on the weir in feet.

BSR080. This site is currently a real-time USGS discharge and water-quality site. This site is critical to monitor for water quality because it is immediately downstream of the confluence of the diversion canal and the Big Sioux River. It is recommended that a cell-phone- triggered ISCO automatic sampler be installed at this site and weekly and event grab samples be collected.

SUC020. Slip Up Creek appears to be a major contributor of both TSS and fecal coliform bacteria. Reestablishing a site on Slip Up Creek is vital for this monitoring plan option; however, it may be beneficial to move the site immediately upstream of the confluence with the Big Sioux River. It is recommended that a cell-phone-triggered ISCO automatic sampler coupled with a stage-recording device be installed at SUC020, baseline grab and event samples be collected, and a stage/discharge relationship be developed by measuring flows during grab sampling and during high flow events.

BSR110. This site is important since it is an end point of a TMDL reach and, ultimately, the location the TMDL is written for. Currently, there are no stage data being collected at this location; however, this site is a historic USGS discharge gauging site, with discharge data collected from July 1959 to October 1972, as well as a current SD DENR WQM site. It is recommended that a cell-phone-triggered ISCO automatic sampler coupled with a stage- recording device be installed at this site, baseline grab and event samples be collected, and a stage/discharge relationship be developed by measuring flows during grab sampling and during high flow events.

Task 1.2: Urban Storm Drain Sampling

Additional monitoring sites will be established on key urban storm drainages that drain to the Big Sioux River. Specifically, nine sites will be identified and monitored using three rotating ISCOs: four sites will be located at the outlet of drainages with relatively uniform land

uses (residential, commercial, industrial, recreational) and two sites located on key drainages that are likely to be large contributors (e.g., the zoo). These rotating ISCOs will be installed and removed for individual storm events to reduce the opportunity for equipment damage to occur in these highly visible areas.

These six sites shown in Figure 3-5, will provide critical information on the loads coming off the urban landscape, calibrating the watershed/water-quality model, and identifying/verifying potential “hotspots.” These are preliminary selections; insight from the City of Sioux Falls based on their local knowledge of the system will be critical in determining the final site locations. These urban storm drain ISCOs will be used to monitor and develop EMCs for the same six events monitored by the semipermanent ISCOs located on the river and creeks. The exact equipment and associated costs for these sites can be found in Chapter 6.0.

Task 1.2.1: Source Tracking

Fifty percent of the water-quality samples collected at urban storm drain sites, or nine total samples, will undergo DNA source tracking to test for the presence/absence of human bacteria source indicators. This will aid in locating sources of impairments; specifically, leaking sewer lines or failing septic systems.

Task 1.3: Monitoring Summary

Table 3-2 gives a breakdown of all of the monitoring that will take place during this project, with a list of expected equipment to be installed. The table is color-coordinated to give insight as to what group/agency is responsible for providing and maintaining equipment. It should be noted that Table 3-2 shows two DENR WQM stations (BSR070 and BSR090) that are not proposed to be actively sampled by RESPECs project team. The DENR indicated that continuous stage-recording devices will be added at these sites. The addition of stage-recording devices and the continued water-quality sampling at these two sites will benefit this TMDL project by adding additional data at semicritical locations in the Sioux Falls area.

Product: Implemented Monitoring Plan

Cost: 319 Funds $170,400 Matching Funds $168,600 Other Federal Funds $0 Task 1 Total $339,000

Task 2: Determine the Stormwater Treatment Capability of the City of Sioux Falls (i.e., the MEP)

It has been shown that a large percent of runoff volume is caused by small rainfall events [Roesner et al., 1991; Water Environment Federation, 1998]. Thus a significant amount of runoff volume can be captured and treated by designing for a moderate rainfall event depth.

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Figure 3-5. Potential Monitoring Points for Urban Storm Drain Sampling.

Table 3-2. Equipment and Sampling Needed for the Big Sioux River TMDL Project (Page 1 of 3)

Continuous Storm Event Base Flow Site Continuous Name WQ Grab Grab Additional Current Status I.D. Flow (sonde) Sampling Sampling

Active USGS Real-Time Discharge Big Sioux River Near BSR010 Y Y N Y and Water Quality, Active SD Dell Rapids DENR WQM Big Sioux River I-90 Bridge Kalesto/YSI Active SD DENR WQM, Active BSR020 Y Y Y Y Upstream of Sioux Falls Nonvented Sioux Falls Monitoring Gate Height Big Sioux River at Discontinued EDWDD Monitoring BSR030 Y N N N Recorders/Stage Silver Creek Site Recorder WPT010 Water Treatment Intake N N N N Water Treatment Plant Intake

33 Big Sioux River Below USGS Real-Time Stage, Peakflow BSR040 N N N N Diversion at Sioux Falls Discharge Active USGS Realtime Discharge, Skunk Creek at Marion SKC030 Y N Y Y ISCO Active DENR WQM, Active Sioux Road Bridge at Sioux Falls Falls Monitoring Big Sioux River at I-229 Discontinued EDWDD Montoring BSR050 N N N N Bridge Site Big Sioux River Near USGS Real-Time Stage, Peakflow BSR060 South Western Ave Bridge Y N Y Y ISCO Discharge at Sioux Falls Big Sioux River in BSR070 Y N N Y Kalesto Active SD DENR WQM Sioux Falls

Table 3-2. Equipment and Sampling Needed for the Big Sioux River TMDL Project (Page 2 of 3)

Continuous Storm Event Base Flow Site Continuous Name WQ Grab Grab Additional Current Status I.D. Flow (sonde) Sampling Sampling

JMC010 NPDES Discharge Location N N N Y NPDES Monitoring Silver Creek 259 Street Discontinued EDWDD Montoring SVC010 N N N N Bridge Site SVC015 Silver Creek Above I-90 Y N Y Y Nimbus/ISCO USGS Real-Time Stage, Peakflow SVC020 Silver Creek at Sioux Falls N N N N Discharge DIV010 Diversion Withdrawal Y N N N Nimbus No Previous Monitoring Active USGS Real-Time Discharge Big Sioux River at BSR080 Y Y Y Y ISCO and Water Quality, Discontinued

34 North Cliff at Sioux Falls EDWDD Big Sioux River at Active SD DENR WQM, Active BSR090 Y N N Y Kalesto Bahnson Avenue Bridge Sioux Falls Monitoring SFW010 NPDES Discharge Location N N N Y NPDES Monitoring Slip Up Creek 477 Avenue Discontinued EDWDD Monitoring SUC010 N N N N Bridge Site Slip Up Creek Upstream of SUC020 Y N Y Y Nimbus/ISCO No Previous Monitoring Confluence With Big Sioux Big Sioux River at Bridge Active SD DENR WQM, Active BSR100 Downstream of Slip Up Y N N Y Kalesto Sioux Falls Monitoring Creek

Table 3-2. Equipment and Sampling Needed for the Big Sioux River TMDL Project (Page 3 of 3)

Continuous Storm Event Base Flow Project Continuous Name WQ Grab Grab Additional Current Status ID Flow (sonde) Sampling Sampling

Discontinued USGS Discharge, Big Sioux River Near BSR110 Y N Y Y Kalesto/ISCO Active SD DENR WQM, Brandon Discontinued EDWDD Storm Sewer Outfalls STW010 (3 Stations rotating to Y N Y N Nimbus/ISCO-3 No previous Monitoring (3) 9 sites)

35 DENR Equipment and Labor DENR Equipment/ RS Labor USGS RESPEC NPDES Monitoring SF Equipment/RESPEC Labor

The question becomes what depth represents the maximum extent practicable. Urbonas et al. [1990], Roesner et al. [1991], and Urbonas and Stahre [1993] used measured rainfall/runoff data and modeled the volume of runoff captured by stormwater BMPs for various cities in the United States. They defined the maximized treatment volume as the point at which rapidly diminishing returns in the number of runoff events captured begins to occur. This point is defined as the “knee” of the curve of percent annual runoff captured versus unit storage volume (treatment volume).

The analysis to estimate the MEP design rainfall event requires application of a rainfall- runoff method (i.e., model) to a range of rainfall events (depth and frequency), watershed characteristics (levels of development), and various types of BMPs, creating a relationship between optimal runoff volume capture ratio and the normalized BMP design volume (depth). The project team will run a fairly simple analysis early in the project to provide an estimate of the MEP. This simple model uses a curve number method and historic hourly rainfall to get a good estimate of the MEP design rainfall event. As shown in Figure 3-6, the MEP can be defined as the point where additional capture volume would result in diminishing returns. Beyond this point, the number of events and the total volume of stormwater runoff fully captured during an average year decrease significantly as the detention volume is increased. This point, referred to by some as the “knee of the curve,” was later defined as the point of maximized capture volume [Urbonas and Stahre, 1993]. The project team believes that determination of MEP early in the project will enable the city to develop and initiate possible changes to design criteria that will be in line with the estimated MEP. By obtaining this early estimate, a comparison can be made with the frequency-based design storm used by the city for sizing stormwater quality BMPs and to evaluate whether a significant change in current practices is necessary.

The impact BMPs (with capture volumes developed by this simple modeling approach and representative removal efficiencies) have on water quality in the Big Sioux River will be evaluated with a continuous water-quantity and quality modeling application. Through this process, the capture volume will be optimized to reduce the predicted exceedances within the BSR caused by stormwater to the MEP.

Product: Recommended Capture Volume Technical Document

Cost: 319 Funds $0 Matching Funds $10,000 Other Federal Funds $10,000 Task 2 Total $20,000

RSI-1827-08-027

Example of Rainfall Analysis for Optimizing Runoff Capture Volume 1

0.9

0.8 Optimum Runoff Volume Capture Ratio = 0.69 Optimum Runoff to Capture = 0.57 (inches)

0.7

0.6

0.5

0.4

0.3 Optimal Runoff Volume Capture Ratio

Watershed Size = 10.00 (acres) Max Pond Brim Full Volume - Pm = 1.28 (acre-ft); 1.53 (inches) 0.2 Pond Emptying Time = 24.00 (hours) Runoff Coeficient - C = 1.00 (--) Event Depth = 0.10 (inches) Event Seperation = 6.00 (hours) 0.1 Results Ave. Event Depth = 0.52 (inches) Ave. Event Duration = 2.57 (hours) 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Normalized Optimal Pond Size (Pd/Pm)

Figure 3-6. Graphic Comparison Example of Optimal Runoff Volume Capture Ratio and the Normalized Best Management Practice Design Volume (Depth) to Determine the MEP Design Depth.

Task 3: Determine the Existing Load, the Loading Capacity of the Waterbodies, and the Existing Departure From the TMDL

Determining the existing load, the loading capacity of the waterbodies, and the existing departure from the loading capacity will require analysis of both historical data and model predictions. The models used will include the load duration curve (LDC) method and HSPF watershed application.

The LDC method involves the development of a flow duration curve or a representation of the percentage of days when a given instream flow is equaled or exceeded. Figure 3-7 shows an example of an LDC developed using MATLAB at a TMDL endpoint. A lower percentile rank of flow indicates periods when flow rarely occurs and typically represents high flow periods (runoff events); whereas, a high percentile rank of flow indicates periods when flow is exceeded most of the time (low flow periods). The allowable pollutant load curve (solid blue line in Figure 3-7) will then be calculated using the flow duration curve and multiplying the flow values by the applicable TMDL concentration target. The curve represents a dynamic expression of the allowable daily load as a function of the measured flow for the respective day.

The observed pollutant loads in the river for the local sampling point can then be plotted on the LDC to show the departure or lack of from water-quality standards for existing conditions. The points that fall above the allowable load curve indicate exceedances while the points that fall below the curve indicate acceptable loads. The observed pollutant loads can also be symbolized by season to provide a temporal aspect to the analysis. Using this curve, departure statistics by flow range and/or season can be calculated.

RSI-1827-08-028

Flow (cfs) 61516 41565 31323 22235 13783 9975 5257 2950 1768 1184 987 823 746 358 234 1017 WQ Standard Station 10570001 Spring Summer Fall Winter

16 10

15 10

14 10 Load / (org day)

13 10

12 10

11 10 0.1 0.3 1 2 5 10 25 50 75 90 95 98 99 99.7 99.9 Percentage of Time Flows are Equaled or Exceeded

Figure 3-7. Example Load Duration Curve for E. coli.

The calibrated and verified HSPF model application framework will be used to provide hourly flow and load predictions at key points in the system for the existing and future conditions. This will provide the ability to allocate loadings to all potential sources; e.g., tributary, upstream, and nonpoint/stormwater loads. Since the model is continuous, the framework can be used to determine the critical environmental conditions (e.g., flow variable, seasonal) for the impaired segments and to gain an understanding of what upstream stressors are driving the impairments. Calibrated HSPF-predicted flows can also be used for the LDCs when measured flows are not concurrently collected with water-quality samples and/or not available at a TMDL endpoint.

Once the system is thoroughly understood and the critical conditions and primary stressors are identified, the TMDL will be expressed in a way that is both achievable and in compliance with water-quality standards.

Product: Watershed Model and Predictions of Existing Load and Departure From TMDL

Cost: 319 Funds $0 Matching Funds $55,000 Other Federal Funds $45,000 Task 3 Total $100,000

Task 4: Allocate the TMDL to the LA and WLA Components

Indirect or nonpoint sources of pollutant loadings are a result of runoff generated from rainfall events; whereas, direct or point sources are discharged to waterbodies on a continuous basis, with no association to rainfall runoff. A comprehensive accounting/allocation of all indirect and direct sources of bacteria and sediment loadings to TMDL endpoints will be made for existing and future conditions. These estimates will be based on a combination of HSPF predictions and available data; the predictions will represent the combined processes of generation and transport and fate.

The WLA and LA will be set based on the assumption that hydrologically connected TMDL reaches (i.e., Big Sioux upstream of Baltic and Skunk Creek) can achieve compliance with water-quality standards, and technically feasible and economically viable BMPs can be strategically implemented within the watershed to capture the MEP rainfall event and best manage the system.

The WLA component will include the summation of the relatively static direct permitted loads (e.g., wastewater treatment plant (WWTP) effluent) and the dynamic indirect stormwater loadings of the MS4. The direct loads will be calculated as the permitted flow times the water- quality standard concentration; some expected future growth will be included in the permitted flow. The indirect component of the WLA can be estimated as follows:

1. The HSPF application can be exercised using long-term historic meteorological data to predict the existing impacts of stormwater runoff generated by the city at each of the TMDL endpoints.

2. Based on an understanding of the critical conditions, predicted exceedances, and driving stressors, the HSPF application can be configured to represent BMPs located throughout the city designed to capture stormwater and reduce pollutant loadings through representative removal efficiencies.

3. The HSPF application can then be adapted to optimize compliance with the TMDL through a combination of capturing stormwater to the MEP and other BMPs throughout the system.

The WLA will be expressed as the sum of the direct and indirect loads in a manner consistent with the TMDL and will include a recommended stormwater capture volume.

The LA at the TMDL endpoint can be calculated using the following equation:

LA=−−− TMDL WLA MOS Boundary Condition Loadings. (3-3)

The boundary condition loadings represent the loads associated with upstream hydrologically connected TMDL reaches. The LA will be expressed in a manner consistent with the TMDL.

The statute and regulations require that a TMDL include a margin of safety to account for any lack of knowledge concerning the relationship between load and wasteload allocations and water quality. EPA guidance explains that the margin of safety (MOS) may be implicit; i.e., incorporated into the TMDL through conservative assumptions in the analysis, or explicit. If the MOS is implicit, the conservative assumptions in the analysis that account for the MOS must be described. If the MOS is explicit, the loading set aside for the MOS must be identified.

The exact method of incorporating the MOS will be determined once uncertainties in the data, models, and resulting TMDL developed for this project are better understood.

Product: Watershed Model and Predictions of the LA and WLA Components of the TMDL

Cost: 319 Funds $65,000 Matching Funds $0 Other Federal Funds $0 Task 4 Total $65,000

Task 5: Analyze the Best Management Practice (Including Stormwater Treatment) Implementation Scenarios

Implementation of the proposed BMPs necessary to reduce loadings and achieve the water- quality target(s) requires an evaluation of feasibility taking into account both the practicality of selected BMPs and the economics of their placement. The implementation of stormwater BMPs is expected to be a significant consideration for the implementation plan. The TMDL analysis will identify a WLA for the stormwater component taking into consideration potential load reductions from all other sources in the study reach. In early discussions with the City of Sioux Falls, it is clear that in some areas of Sioux Falls, it is less feasible to implement stormwater management practices because of the level of development and available space. This does not imply that BMPs cannot be implemented, but the level and type of implementation is expected to vary. RESPEC proposes to use the developed model to evaluate the physical and economical feasibility of BMP implementation based on level of development, space availability and economics, and currently accepted practices. Thus the implementation plan may result in higher levels of implementation in some areas because of feasibility, but the overall implementation will meet the TMDL load allocations.

The proposed or recommended implementation plan will identify the types and level of BMP implementation and other practices related to load reduction and allocation, such as the diversion operation. An initial level of prioritization will be developed in cooperation with the City of Sioux Falls.

Product: Watershed Model and Analysis of BMPs

Cost: 319 Funds $40,000 Matching Funds $0 Other Federal Funds $0 Task 5 Total $40,000

OBJECTIVE 2: Write TMDL Reports and a Final Watershed Assessment Report.

Task 6: Write Watershed Final Assessment Report

A TMDL report for each impaired stream segment will be written using the water-quality data, collected during the stream monitoring efforts, and the results from the HSPF watershed model. The TMDL report for each impaired stream segment will consist of a pollutant assessment, natural background loads, point and nonpoint load allocations, recommended BMPs for achieving pollutant loads allocated, and any follow-up monitoring needed. One student with a master of science degree will write a thesis based on the results of this project and the thesis will be included as an attachment to the final report. A total of ten stream TMDLs will be written for the Sioux Falls TMDL Assessment Project. The TMDLs written will be combined and summarized in a final watershed assessment report.

The final watershed assessment report will be delivered as one hard copy and one electronic copy to the SD DENR and the City of Sioux Falls at the end of the project. The watershed assessment report will be submitted no later than June 30, 2011. SD DENR and the EPA will review and approve the final assessment report. The watershed assessment report will include TMDLs for both fecal coliform (or E. coli) and TSS for the five impaired reach segments and suggested load reductions to achieve the beneficial uses of these segments. BMPs will be suggested to achieve these reductions in a relatively gross but spatially explicit manner. Specifically, the BMPs required will be specified in terms of their location, removal efficiencies required, and areas served.

Product: Watershed Assessment Report and Ten TMDL Summary Reports

Cost: 319 Funds $55,000 Matching Funds $0 Other Federal Funds $0 Task 6 Total $55,000

OBJECTIVE 3: Information and Education.

Task 7: Information and Education

All stakeholders within the watershed will share findings of the data and will work to protect the environment. We hope to support the City of Sioux Falls at city council meetings and other public meeting to present findings. The development of a Web site will be used to disseminate and network project information to aid the general public, concerned landowners, agricultural producers, municipalities, and participating agencies in making sound decisions. The maintenance of the Web site will also produce the opportunity to network and share findings.

Stakeholders within the watershed will be contacted, have access to the Web site, and be invited to participate in outreach meetings. A compilation of the group’s efforts within the watershed will reduce duplication and network data and findings and will work toward the common goal of the watershed. The group will share technology and findings at public meetings with dissemination of minutes, reports, and practical applications and findings.

Product: Public Information and Outreach Including a Project Web Site

Cost: 319 Funds $15,000 Matching Funds $0 Other Federal Funds $0 Task 7 Total $15,000

Task 8: HSPF Model Training

A training session will be provided to a maximum of ten potential HSPF model users. Training materials will be provided to facilitate future model use.

Product: Watershed Technical Training Session

Cost: 319 Funds $5,000 Matching Funds $0 Other Federal Funds $0 Task 8 Total $5,000

3.3 ANTICIPATED SCHEDULE

The anticipated completion of this project is December 31, 2010; however, if additional sampling is deemed necessary and performed in calendar year 2010, the completion date will be extended through June 2011. The anticipated schedule required to complete the proposed work is broken down by task products in Figure 3-8.

RSI-1827-08-029 43

Figure 3-8. Schedule for the Sioux Falls Total Maximum Daily Load Project.

3.4 SPECIAL PERMITS

No special permits are required to perform this assessment project.

3.5 LEAD PROJECT SPONSOR

The City of Sioux Falls is the appropriate lead project sponsor for this activity. The city plays a major role in implementation of the TMDL that will be developed as a result of this study. The city will also be involved in compiling available data and reviewing and evaluating the results and feasibility of the project.

3.6 BEST MANAGEMENT PRACTICES

No BMPs will be funded or implemented during this assessment project.

4.0 COORDINATION PLAN

4.1 PROJECT SPONSORS

The City of Sioux Falls Public Works Department is the sponsor for this project. At the start of the project, watershed stakeholder agencies will be contacted in writing to describe the project and solicit their participation. The following agencies have been or will be contacted and encouraged to participate by providing data and developing consensus on the methodology and resulting conclusions:

• United States Army Corps of Engineers

• United States Department of Agriculture, Natural Resources Conservation Service

• United States Department of Agriculture, Farm Service Agency

• United States Fish and Wildlife Service

• United States Geological Survey

• South Dakota Cattlemen’s Association

• South Dakota Corn Growers Association

• South Dakota Department of Environment and Natural Resources

• South Dakota Department of Game, Fish and Parks

• South Dakota Soybean Association

• South Dakota State University, Water Resources Institute

• Sioux Falls Public Works Department

• Counties and cities within the watershed

• Resource, Conservation, and Development Associations within the watershed

• Conservation Districts within the watershed.

This is a cooperative project with work to be completed by multiple agencies working together on multiple aspects of this project. Cooperators on this project include the City of Sioux Falls Public Works Department, USGS, and RESPEC. The City of Sioux Falls Public Works Department is primarily responsible for administration and project oversight; USGS is primarily responsible for continuous stream gauging; and RESPEC is primarily responsible for project management, field sampling and coordination, watershed model development, and information and education. The final report will be a collaboration of each of the project partners and contributing agencies. There will be contractual agreements between the project

sponsor and project partners involved in contributing services and equipment to complete the TMDL assessment.

4.2 LOCAL SUPPORT

The City of Sioux Falls Public Works Department, the project sponsor, is fully supportive of the development of this TMDL and recommendations for remediation that will be included in the final report. The land within the city limits of Sioux Falls has the potential to be a significant contributor to the pollutant loading as well as a catalyst in the restoration of the impaired waterbodies, especially in the lower portion of the project area.

4.3 PROJECT COORDINATION

There are several ongoing projects in the Sioux Falls TMDL project area being conducted to maintain and restore the health of the watershed. The East Dakota Water Development District is currently implementing best management practices targeted to reduce TSS and fecal coliform loading to the North Central and Central Big Sioux River Watersheds. The Natural Resources Conservation Service (NRCS) is also actively seeking local partners to help implement conservation projects with aid from programs such as their Environmental Quality Incentive Program (EQIP) and/or Wildlife Habit Incentive Program (WHIP). Several local conservation districts are also involved in various watershed restoration projects. The developers of this TMDL study will consult with all ongoing projects within the watershed to help develop BMPs that have been successful in the past, are practical, and can be economically implemented.

4.4 SIMILAR ACTIVITIES IN THE WATERSHED

There are no similar activities being conducted in the watershed that this project would duplicate.

5.0 EVALUATION AND MONITORING PLAN

5.1 FIELD DATA COLLECTION

The collection of all field data will be performed in accordance with SD DENR’s Standard Operating Procedures for Field Samplers, Tributary and In-Lake Sampling Techniques. The monitoring strategy is explained in Section 3.2. The monitoring plan selected is based on information presented in Love [2008] and a meeting with key project team members held in Pierre, South Dakota, on September 11, 2008. Approved QA/QC procedures will be utilized on all sampling and field data collected during this project. A minimum of 10 percent of all water- quality samples collected will be QA/QC samples. QA/QC samples will consist of field blanks and field duplicates. The activities involved with the QA/QC procedures and the results of the QA/QC monitoring will be compiled and reported in the final assessment report.

5.2 MONITORING STRATEGY

Monitoring sites will be maintained and sampled for TSS, fecal coliform and E. coli during baseflow and storm events. Loadings will be calculated from collected samples. QA/QC procedures will be used to evaluate whether the project goals and objectives have been met. The goals and objectives will be reanalyzed based on the model calibration results, statistical analysis, correlations, and developed relationships. If large data gaps are unclear or are identified as problematic, a decision to extend the monitoring into 2010 will be considered based on the return on investment (e.g. will the benefit of continued monitoring outweigh the corresponding costs). At this point, future monitoring and funding would need to be discussed. The project goals and objectives will be achieved when the TMDLs for TSS and fecal coliform (or E. coli), as well as the final watershed assessment report, are completed and approved by the SD DENR and the EPA.

5.3 DATA MANAGEMENT, STORAGE, AND REPORTING

RESPEC’s GIS analysts work with SQL Server using ESRI’s spatial data engine (SDE) geodatabase format. ESRI is the defacto standard in GIS; therefore, the project team will be using this software application to manage all project data. RESPEC routinely customizes the ArcHydro data model to include additional thematic layers, attribute and time-series tables, and relationship classes. This data model is the industry-adopted schema for water resources. The thematic layers routinely used in the ArcHydro model are shown in Figure 5-1.

RSI-1827-08-030

Figure 5-1. Thematic Layers of the ArcHydro Data Models.

Historical data for this project were processed into the ArcHydro format and stored in the SDE geodatabase. New water-quality data will be processed using methods developed by RESPEC to quickly transform the data into the format necessary to import to the project SDE geodatabase. Although RESPEC chooses to use the ESRI’s SDE geodatabase, the associated SQL server can be used to export the data to numerous platforms and file formats. In summary, RESPEC will export the data in a format that is most compatible for the EPA STORET database.

RESPEC has also developed a custom map application using ESRI’s ArcGIS Server technology. The map application is used for people involved in this project to visualize both spatial and tabular data. This map application will be maintained for the duration of this project.

5.4 DESCRIPTION OF MODELS USED

A watershed model application will be developed to quantify the relative contribution of the different stressors (sources of pollution), including point sources from industrial and municipal effluent; nonpoint sources derived from diffuse origins, such as runoff from urban, agricultural, and forested lands; and the impact of upstream and tributary sources to the impairment of the receiving waterbodies.

The watershed model will first be calibrated and verified with historic data and data collected as part of this project to represent existing or baseline conditions within the five BSR TMDL reach segments. These data will include instream data and event mean concentration data coming off nonpoint sources within the watershed. This framework will then be used to (1) develop the target TMDLs for fecal coliform (or E. coli) and TSS for the five BSR reaches, (2) understand the existing departure from the target TMDLs, (3) allocate the loads to the WLA and LA components of the TMDL, (4) illustrate the effects of land use conversions and alterations, and (5) evaluate the effectiveness of BMPs to achieve the TMDLs.

The watershed modeling package selected for this project is HSPF. HSPF is a comprehensive watershed model of hydrology and water quality that includes modeling of both land surface and subsurface hydrologic and water-quality processes, linked and closely integrated with corresponding stream and reservoir processes. It is considered a premier, high-level model among those currently available for comprehensive watershed assessments. The major steps in the watershed model application process consist of the following:

1. Acquisition and analysis of data.

2. Characterization and segmentation of the watershed.

3. Calibration and verification of the model for existing or baseline conditions.

4. Analysis of alternative management scenarios and BMPs.

5.5 LONG-TERM FUNDING PLANS FOR THE OPERATION AND MAINTENANCE OF RESTORATION ACTIVITIES

There are several entities and funding sources available to share the cost of implementing BMPs recommended as a result of this TMDL study. The NRCS has several programs such as their Conservation Reserve Program (CRP), Environmental Quality Incentives Program (EQIP), and Wildlife Habitat Incentives Program (WHIP), which provide cost-share dollars to rural landowners that could be used to help implement agricultural BMPs. There is also cost- share money available to help implement agricultural BMPs through the U.S. Fish and Wildlife Service and the South Dakota Game, Fish and Parks. EPA 319 grant funds available through the SD DENR are a possible source to help offset the cost of implementing urban BMPs. The City of Sioux Falls, other local municipalities, and local conservation districts and watershed groups will also be called upon to provide funding assistance.

6.0 BUDGET

Budget breakdowns are shown in Table 6-1. The total cost of this project is $639,000, of that $350,400 is EPA 319 funds, $233,600 is matching funds divided amongst the City of Sioux Falls, EDWDD, and the SD DENR, and $55,000 is being provided by the SD DENR in the form of a 604(b) grant. Of the total cost, $339,000 is allocated for an implemented monitoring plan (Table 6-2). The total amount of requested funds for monitoring is $339,000. The total costs for monitoring include $31,000 dollars of in-kind cost share provided by the City of Sioux Falls for laboratory analysis, assuming the analysis and costs are covered by the City Health Laboratory, and for equipment, assuming that six ISCO samplers are available for use for 1 year on this project. If these assumptions are not true, the total for in-kind cost share would be needed as part of the requested funding package for this project. Labor costs have been divided into two categories: RESPEC labor and subcontract labor (Table 6-2). RESPEC intends to hire two field technicians through subcontract agreements in the City of Sioux Falls. The labor for these two individuals is presented separately in Table 6-2.

Table 6-1. Complete Project Budget Summary (Page 1 of 2)

Other Matching Funds Federal ($) Funds Total EPA 319 EPA 319 and Matching Funds Budget Product ($) City of SD DENR Cost ($) EDWDD 604(b) Grant Sioux Falls Fee Funds ($) ($) ($) ($)

Objective 1. Develop Budgets for Water-Quality Constituents Listed as Impaired in the Sioux Falls TMDL Project Area and Recommend BMPs for Pollutant Load Reduction

Task 1. Develop and Implement a Water-Quality Monitoring Plan for Data Acquisition

Product 1. Implemented Monitoring Plan $170,400 $81,000 $75,000 $12,600 $339,000 52 Task 2. Determine the Stormwater Treatment Capability of the City of Sioux Falls

Product 2. Recommended Capture Volume $10,000 $10,000 $20,000 Technical Document

Task 3. Determine the Existing Load and the Loading Capacity of the Waterbodies, and the Existing Departure From the TMDL

Product 3. Watershed Model and Predictions of Existing Load and Departure From $40,000 $15,000 $45,000 $100,000 TMDL

Task 4. Allocate the TMDL to the LA and WLA Components

Product 4. Watershed Model and Predictions of the $65,000 $65,000 LA and WLA Components of the TMDL

Task 5. Analyze the BMP (Including Stormwater Treatment) Implementation Scenarios

Product 5. Watershed Model and Analysis of BMPs $40,000 $40,000

Table 6-1. Complete Project Budget Summary (Page 2 of 2)

Other Matching Funds Federal ($) Funds Total EPA 319 EPA 319 and Matching Funds Budget Product ($) East City of SD DENR Cost ($) Dakota 604(b) Grant Sioux Falls Fee Funds WDD ($) ($) ($) ($)

Objective 2. Write TMDL Reports and a Final Watershed Assessment Report

Task 6. Write Watershed Final Assessment Report

Product 6. Watershed Assessment Report and Ten $55,000 $55,000 TMDL Summary Reports 53 Objective 3. Information and Education

Task 7. Information and Education

Product 7. Public Information and Outreach $15,000 $15,000 Including a Project Web Site

Task 8. HSPF Model Training

Product 8. Watershed Technical Training Session $5,000 $5,000

Totals $350,400 $131,000 $75,000 $27,600 $55,000 $639,000

Table 6-2. Big Sioux River Monitoring Budget for Calendar Year 2009

Funds In-Kind Total Requested Cost Share

Sampling $3,000 $22,000 $25,000 Equipment $68,000 $9,000 $77,000 RESPEC Labor $126,000 $0 $126,000 Subcontract Labor $111,000 $0 $111,000

Monitoring Costs Costs Monitoring Total $308,000 $31,000 $339,000

7.0 PUBLIC INVOLVEMENT

In addition to soliciting the participation of interested public agencies, the principal investigators will participate in a minimum of four public meetings with interested stakeholders to review the results of this study; one at the start of the project, one in the middle of the project, and two near the end.

8.0 REFERENCES

City of Sioux Falls Public Works Department, 2006. Raw Water Sources, retrieved September 1, 2008, from the World Wide Web http://www.siouxfalls.org/PublicWorks/ purification/documents/raw_water_sources

East Dakota Water Development District, 2004. Phase 1 Watershed Assessment Final Report and TMDL Central Big Sioux River, Brookings, Lake, Moody, and Minnehaha Counties, South Dakota, prepared by East Dakota Water Development District, Brookings, SD, for South Dakota Department of Environment and Natural Resources, Pierre, SD.

East Dakota Water Development District, 2008. Electronic communication between East Dakota Water Development District, Brookings, SD, and J. Lambert, RESPEC, Rapid City, SD, July 3.

Love, J. T., 2008. Preliminary Findings and Future Monitoring Recommendations, memorandum RSI(RCO)-1827/9-08/2, prepared by RESPEC, Rapid City, SD, for A. Berg, City of Sioux Falls, Sioux Falls, SD, September 5.

Niehus, C. A., 1997. Characterization of Stormwater Runoff in Sioux Falls, South Dakota, 1995–96: U.S. Geological Survey Water-Resources Investigations Report 97-4070, p. 72.

Roesner, L. A., E. H. Burgess, and J. A. Aldrich, 1991. “Hydrology of Urban Runoff Quality Management,” Proceedings, 18th National Conference Water Resources Planning and Management Symposium on Urban Water Resources, American Society of Civil Engineers, New Orleans, LA, May 20–22.

Sando, S. K., E. T. Furlong, J. L. Gray, and M. T. Meyer, 2006. Occurrence of Organic Wastewater Compounds in Drinking Water, Wastewater Effluent, and the Big Sioux River in or Near Sioux Falls, South Dakota, 2001-2004: U.S. Geological Survey Scientific Investigations Report 2006–5118, p. 168.

South Dakota Department of Environment and Natural Resources, 2008. The 2008 South Dakota Integrated Report for Surface Water Quality Assessment, prepared by South Dakota Department of Environment and Natural Resources, Pierre, SD.

South Dakota Department of Game, Fish and Parks, 2008. Big Sioux River Canoe/Kayak Map, retrieved September 8, 2008, from the World Wide Web http://www.sdgfp.info/ Publications/Parks/BigSioux.pdf

South Dakota State University, 2008. South Dakota Climate and Weather, retrieved September 1, 2008, from the World Wide Web http://climate.sdstate.edu/climate_site/ climate.htm

United States Department of Commerce National Climatic Data Center, 2004. Snowfall-Average Totals in Inches, retrieved September 1, 2008 from the World Wide Web http://lwf.ncdc.noaa.gov/oa/climate/online/ccd/snowfall.html

Urbonas, B. R., J. C. Y. Guo, and L. S. Tucker, 1990. “Optimization of Stormwater Quality Capture Volume,” Proceedings, Urban Stormwater Quality Ennacement–Source Control, Retrofitting, and Combined Sewer Technology, Urban Water Research Council of the American Society of Civil Engineers, Davos Platz, Switzerland, October 22–27.

Urbonas, B. R. and P. Stahre, 1993. Stormwater—Best Management Practices Including Detention, Prentice Hall, Englewood Cliffts, NJ.

Water Environment Federation, 1998. Urban Runoff Quality Management, WEF Manual of Practice No. 23, ASCE Manual and Report on Engineering Practice No. 87, Water Environment Federation and American Society of Civil Engineers, pp. 249.