United States 

Environmental Protection 

Agency 

Using Economic Incentives to 

Manage Stormwater Runoff in the 

Shepherd Creek Watershed, Part I 
i

 

 

 EPA/600/R-08-129 

October 2008 

Using Economic Incentives to 
 

Manage Stormwater Runoff in the 
 

Shepherd Creek Watershed, 
 

Part I
 


By 
 

Hale W. Thurston, Allison H. Roy, William D. Shuster, Matthew A. Morrison*, 
 

Michael A. Taylor, and Heriberto Cabezas 
 

A portion of the work outlined in this report was done under 
 

Contract number EP-C-05-061 Task Order #08 
 

Project Officer Hale W. Thurston, PhD. 
 

Sustainable Technology Division 
 

*Land Remediation and Pollution Control Division 
 

National Risk Management Research Laboratory 
 

US Environmental Protection Agency 
 

Cincinnati, OH 45268
 

 

Notice 

The U.S. Environmental Protection Agency (EPA) through its Office of Research and 

Development performed and managed the research described in this report. It has been subjected 

to the Agency‘s peer and administrative review and has been approved for publication as an EPA 

document. Any opinions expressed in this report are those of the author and do not, necessarily, 

reflect the official positions and policies of the EPA. Any mention of products or trade names 

does not constitute recommendation for use by the EPA. 

Acknowledgments 

The U.S. Environmental Protection Agency through its Office of Research and 

Development funded and collaborated in the research described here under the Scientific, 

Technical, Research, Engineering and Modeling Support (STREAMS) contract EP-C-05-061, 

Task Order 8: “Implementing Dispersed Best Management Practices in the Shepherd Creek Area 

of Cincinnati.” Support for water quality sampling and analysis was provided by Pegasus 

Technical Services, Inc. under EPA Contract # EP-C-05-056. The U.S. EPA's Central Regional 

Laboratory in Chicago, IL provided critical and timely analytical services for the majority of the 

water quality analyses. Periphyton and macroinvertebrate identifications and chlorophyll 

analyses were performed in 2003-04 by PhycoTech, Inc. under simplified acquisition 3C-R312­

TTSA and in 2005-06 by EnviroScience, Inc. under simplified acquisition EP05C00134. 

Directly connected impervious area (DCIA) data entry and assessment were performed under 

STREAMS Contract EP-C-05-059, task order 0009, to Eastern Research Group, Inc. Support for 

some of the hydrologic monitoring was made available through an Interagency Agreement (IAG) 

with the U. S. Department of Agriculture-National Resources Conservation Service (USDANRCS) for “Hydroecological benefits and economic attributes of on-lot stormwater best 

management practices”, DW12921597-01-0, 2004 and an IAG with the US Geological Survey 

(USGS) titled “Hydroecological benefits and economic attributes of on-lot stormwater best 

management practices”, DW-14-921600-01-0, 2004-2007. 

This report would not be possible without the work of many people along the way. 

Haynes C. Goddard, David Szlag, Beth Lemberg, Michael Miller, and Jamie C. Coleman had 

significant intellectual input at the inception of this project. Laura Boczek of ORD's Water 

Supply and Water Resources Division coordinated microbial assessments for all water samples. 

Ward Wilson, Mike Valerius and David Snook provided invaluable work in the field. 

ii 
Foreword 

The U. S. Environmental Protection Agency (USEPA) is charged by Congress with 

protecting the Nation's land, air, and water resources. Under a mandate of national 

environmental laws, the Agency strives to formulate and implement actions leading to a 

compatible balance between human activities and the ability of natural systems to support and 

nurture life. To meet this mandate, USEPA’s research program is providing data and technical 

support for solving environmental problems today and building a science knowledge base 

necessary to manage our ecological resources wisely, understand how pollutants affect our 

health, and prevent or reduce environmental risks in the future. 

The National Risk Management Research Laboratory (NRMRL) is the Agency's center 

for investigation of technological and management approaches for preventing and reducing risks 

from pollution that threaten human health and the environment. The focus of the Laboratory's 

research program is on methods and their cost-effectiveness for prevention and control of 

pollution to air, land, water, and subsurface resources; protection of water quality in public water 

systems; remediation of contaminated sites, sediments and ground water; prevention and control 

of indoor air pollution; and restoration of ecosystems. NRMRL collaborates with both public 

and private sector partners to foster technologies that reduce the cost of compliance and to 

anticipate emerging problems. NRMRL's research provides solutions to environmental problems 

by: developing and promoting technologies that protect and improve the environment; advancing 

scientific and engineering information to support regulatory and policy decisions; and providing 

the technical support and information transfer to ensure implementation of environmental 

regulations and strategies at the national, state, and community levels. 

This publication has been produced as part of the Laboratory's strategic long-term 

research plan. It is published and made available by USEPA's Office of Research and 

Development to assist the user community and to link researchers with their clients. 

 Sally Gutierrez, Director 

National Risk Management Research Laboratory 

iii 
 

Abstract 

Communities nationwide are facing increased responsibility for controlling stormwater 

runoff, and, subsequently, rising costs of stormwater management. In this report we describe and 

test a methodology that can be used by communities to focus limited budgets on the most 

efficient and ecologically-effective installation of stormwater management practices. The 

overall project has two primary objectives: (1) to test the use of an auction to cost-effectively 

allocate stormwater management practices among landowners, and (2) to determine the 

effectiveness of the resulting implementation in terms of hydrological, water quality, and 

ecological measures. Here, we describe the theories, methods, and criteria used to distribute rain 

gardens and rain barrels to homeowners in a small, midwestern watershed. The first round of the 

reverse auction in 2007 resulted in 50 rain gardens and 100 rain barrels installed at 67 of the 

approximately 350 residential properties in the experimental watershed. In 2008, the auction 

was repeated and we accepted bids for an additional 35 rain gardens and 74 rain barrels. 

Stormwater management practices were distributed relatively evenly throughout the watershed 

and are expected to result in significant improvements in stream quality. We describe our 

monitoring approach, including 1) parcel-scale hydrology and water quality monitoring of 

selected rain gardens, and 2) stream monitoring following before-after-control-impact approach 

for assessing the hydrological, water quality, and biotic responses to stormwater management 

installation. By employing a multidisciplinary approach to watershed management, the case 

study offers an example of stormwater management that should be readily transferable to other 

residential watersheds. 

iv 
 

Table of Contents 

Page
 

Title Page..........................................................................................................i 
 

Notice................................................................................................................................................. ii 
 

Acknowledgments.............................................................................................................................. ii 
 

Foreword...........................................................................................................................................iii 
 

Abstract...........................................................................................................iv 
 

List of Tables .................................................................................................................................... vi 
 

List of Figures................................................................................................................................... vi 
 

CHAPTER 1 Introduction.................................................................................................................. 1 
 

1.1 Background............................................................................................................................... 1 
 

1.2 Purpose ..................................................................................................................................... 1 
 

1.3 Study setting ............................................................................................................................. 1 
 

CHAPTER 2 Developing a Retrofit Watershed Management Strategy ............................................ 2 
 

2.1 Characterizing the impairment ................................................................................................. 2 
 

2.2 Assessing the source of impairment and potential for improvement ....................................... 5 
 

2.3 Evaluating economic incentive mechanisms............................................................................ 9 
 

CHAPTER 3 Stream Monitoring Design ........................................................................................ 14 
 

3.1 Experimental design ............................................................................................................... 14 
 

3.2 Hydrologic monitoring ........................................................................................................... 16 
 

3.3 Water quality monitoring........................................................................................................ 16 
 

3.4 Ecological monitoring ............................................................................................................ 18 
 

CHAPTER 4 Auction Design .......................................................................................................... 21 
 

4.1 Background............................................................................................................................. 21 
 

4.2 Information to homeowners.................................................................................................... 21 
 

4.3 Methods for assessing auction bids ........................................................................................ 25 
 

CHAPTER 5 Auction Results.......................................................................................................... 29 
 

5.1 Phase 1, Year 2007 ................................................................................................................ 29 
 

5.2 Phase 2, Year 2008 ................................................................................................................ 33 
 

CHAPTER 6 Stormwater Management Practice Installations ........................................................ 36 
 

6.1 Overview ................................................................................................................................ 36 
 

6.2 Rain gardens ........................................................................................................................... 36 
 

6.3 Rain barrels............................................................................................................................. 38 
 

CHAPTER 7 Rain Garden and Rain Barrel Monitoring ................................................................. 40 
 

7.1 Overview ................................................................................................................................ 40 
 

7.2 Hydrology and soils................................................................................................................ 40 
 

7.3 Water quality .......................................................................................................................... 40 
 

CHAPTER 8 Conclusions................................................................................................................ 42 
 

Publications related to this project................................................................................................... 43 
 

References........................................................................................................................................ 45 
 

APPENDIX A: Rain Garden Schematics ........................................................................................ 49 
 

APPENDIX B: Rain Barrel Schematic............................................................................................ 54
 


APPENDIX C: Quality Management Program ............................................................................... 55 
 

v 
 

 

 

List of Tables 

Table 2.2.1 Total (TIA) and Directly Connected (DCIA) Impervious Area Categorized by Impervious Surface Type. 7
 


Table 3.1.1 Start dates for hydrology, water quality, and ecology monitoring............................................................... 14
 


Table 3.3.1 Summary of water quality monitoring parameters and associated impairments.......................................... 17
 


Table 3.4.1 Summary of samples collected and sampling resolution. ............................................................................ 18
 


Table 5.1.1 Summary of bids for rain gardens and rain barrels in 2007 and 2008 ......................................................... 29
 


Table 5.1.2 Rain barrel rankings, 2007........................................................................................................................... 30
 


Table 5.1.3 Rain garden rankings, 2007 ......................................................................................................................... 31
 


Table 5.2.1 Rain garden rankings, 2008 ......................................................................................................................... 33
 


Table 5.2.2 Rain barrel rankings, 2008........................................................................................................................... 34
 


List of Figures 

Figure 2.1.1 Map of impervious areas and parcels within the Shepherd Creek study watersheds.................................... 2
 


Figure 2.1.2 Pre-implementation data for Shepherd Creek sites, comparing baseflow and stormflow water quality data 
 

for the years 2005 and 2006. (A) Dissolved Inorganic Nitrogen; (B) Total Phosphorus and (C) Extent of bacterial
 


Figure 2.2.1 Total connected and disconnected impervious area in the Shepherd Creek watershed based on property
 


contamination (as Escherichia coli); note log scale for y axis on these plots................................................................... 4
 


ownership. ........................................................................................................................................................................ 6
 


Figure 2.2.2 Percent TIA given 0, 25, 50, and 100% landowner acceptance rates of rain gardens and rain barrels. ....... 8
 


Figure 2.3.1 Costs of runoff detention with Tradable Allowances................................................................................. 11
 


Figure 3.1.1 Location of sites for various sampling activities in the Shepherd Creek watershed................................... 15
 


Figure 4.2.1 Brochure sent to eligible homeowners. ..................................................................................................... 22
 


Figure 4.2.2 Auction bid form included in second mailing. ........................................................................................... 23
 


Figure 4.2.3 Pictures of demonstration rain barrel (A), rain garden (B), and signage (C)............................................. 24
 


Figure 5.1.1 Location of rain barrel and rain garden bids in Phase 1, 2007 ................................................................... 32
 


Figure 5.2.1 Location of rain barrel and rain garden bids in Phase 2, 2008 ................................................................... 35
 


Figure 6.2.1 Species in plant communities planted in rain gardens, 2007...................................................................... 37
 


Figure 6.2.2 Typical rain garden installation.................................................................................................................. 38
 


vi 
CHAPTER 1 Introduction 

1.1 Background 

Traditional stormwater control policies have concentrated on solutions that build 

centralized capacity to direct and hold excess runoff within a storm sewer system. However, such 

centralized infrastructures do not sufficiently alleviate water quality problems for receiving waters, 

and can be expensive for municipalities who must work within budget constraints. This project 

tests an alternative approach to stormwater control using a decentralized approach that disperses 

retrofit runoff detention practices throughout a small suburban watershed, thus reducing runoff 

before it reaches the sewer system. By distributing decentralized stormwater detention through 

market mechanisms, we concurrently study the hydrological, water quality, and ecological benefits 

of stormwater management practice implementation and explicitly evaluate the cost of meeting 

environmental quality standards through this type of approach. 

1.2 Purpose 

The overall project has two primary objectives: (1) to test the use of an auction to costeffectively allocate stormwater management practices among landowners, and (2) to determine the 

effectiveness of the resulting implementation in terms of hydrological, water quality, and 

ecological measures. The stormwater management practices used in this project were limited to 

rain barrels and rain gardens. A voluntary, sealed-bid auction was used to allocate stormwater 

management practices and determine the compensation private landowners will receive in 

exchange for accepting the installation of a stormwater management practice on their property. 

The winners of the auction were those who offered to accept stormwater management practices 

with the greatest environmental benefits at the lowest price. The auction provided a means of 

identifying willing landowners and offers a mechanism by which these stormwater management 

practices can be systematically allocated to these landowners within the watershed. 

1.3 Study setting 

The study took place in the Shepherd Creek watershed, a tributary to the West Fork Mill 

Creek, located in Mt. Airy, Cincinnati, Ohio. The watershed is 1.85 km2

 (457 acres), 

approximately one-third of which lies within a city park with mature deciduous forest. The other 

two-thirds of the watershed represent a mix of 1960-1980s residential parcels in the headwaters, 

and horse pastures at downstream locations. The residential area consists primarily of single 

family homes and has a median lot size of 880 m

2 (0.22 acres). Over three-quarters of the 406 

houses in the catchment were built between 1950 and 1990. There are also three apartment 

complexes (27 buildings) in the headwaters and several public buildings with parking lots (e.g., a 

church, police station, park arboretum). The watershed sits on calcareous shale and limestone 

formations with moderate slopes, and silt and silty clay loam soils dominate. 

1
 

Figure 2.1.1 Map of impervious areas and parcels within the Shepherd Creek study watersheds. 

CHAPTER 2 Developing a Retrofit Watershed Management Strategy 

2.1 Characterizing the impairment 

 Cincinnati’s Mill Creek is considered by the Ohio Environmental Protection Agency to 

be among the most polluted waterways in the state (OEPA, 1994), with stormwater runoff being 

a major direct and indirect contributor to the pollution. The Shepherd Creek is similarly 

impaired by stormwater runoff, as evidenced by hydrologic, geomorphic, water quality, and 

biotic assessments of the stream and its tributaries (Figure 2.1.1). 

In terms of stream geomorphology, the cobble/gravel riffles are highly embedded with silts 

and other smaller-sized eroded sediments. A high percentage of total streambed area is observed 

to be highly scoured and entrenched, leaving platy formations of bedrock which are in an active 

process of rotting, and these surfaces are typically found to be covered with a thin layer of silt. 

Since the streambeds have been down cut to bedrock, stream reaches have attempted to adjust to 

2 
 
present stream flow patterns through lateral expansion. This process involves the erosion of soils 

and wearing away of bedrock to each side of the original streambed. For areas where roads are 

adjacent to the streams, some banks have been fortified with concrete, limiting lateral expansion 

to one stream bank only. 

Developed areas exhibit the predictable flashy behavior found in urban streams, which was 

much more pronounced than the more gradual rise and fall hydrograph shape for adjacent 

forested areas in Mt. Airy park (Sub5). Storm runoff from urban areas is flashy and delivered 

quickly and in great volumes to stream reaches (Paul and Meyer 2001). These small urban 

streams may also lack natural baseflows, resulting in streambeds that are dry in the summer 

months such that stream flows that can be sporadic and limited to storm events. 

Water chemistry in the sub-watersheds is characterized by neutral to alkaline pH (average 

values range from 7.7 to 7.9), with high average alkalinity (225 to 295 mg CaCO3·l-1) from natural 

dissolution of the calcareous shale bedrock that is extant throughout the watershed. As in many 

established urban watersheds, chloride (Cl) concentrations are elevated at some stream locations 

mostly because of road salt application (Godwin et al. 2003, Kaushal et al. 2005). Sub4, which 

receives direct street runoff and is downstream from a moderately steep hill (where salt 

application would be expected to be heavy during the winter months), averages 280 mg/L year 

round. This value is above the chronic toxicity limit for Cl in freshwater (250 mg/L), and much 

higher than the approximately 50 mg/L average measured at Sub1 and Sub2. Sub5 also receives 

road runoff and has an average Cl concentration of 161 mg/L that appears to cycle throughout the 

year as salt is loaded into the stream during the winter and flushed out in the summer. Nitrogen 

and phosphorus concentrations fall within the range of values expected for urban land uses (Figure 

2.1.2 A and B) (e.g., Schoonover et al. 2005). Average baseflow values for dissolved inorganic 

nitrogen (DIN) and total phosphorus (TP) ranging from 0.20 to 0.98 mg·l-1 and 0.17 to 0.37 mg·l-1 

respectively for the years 2005-2006. 

Since hydrology and water chemistry tend to regulate biological activity in aquatic 

ecosystems, we were not surprised to find that our periphyton samples contained high 

concentrations of chlorophyll a (average 4.3 to 10.2 mg/m2 across sites, 2003-2006). Average 

algal ash-free-dry-mass in 2005-2006 ranged from 57.1 (Catch) to 87.9 (Sub5a) g/m2. A 

majority of the algal cells sampled were cyanobacteria, which reflects overall poor water quality. 

Macroinvertebrate assemblages were typically dominated by isopods, amphipods, and 

chironomids. In 2005-2006, there was an average richness of 18.0 (Sub4) to 24.1 (Sub2) taxa 

per site. Sensitive taxa in the orders Ephemeroptera, Plecoptera, and Trichoptera (EPT) 

constituted a mere 0.5% (Sub2) to 5.4% (Catch) of the samples by abundance, further reflecting 

poor biotic integrity within the tributary streams. Hilsenhoff’s Family Biotic Index scores for 

macroinvertebrates suggest fairly poor (5.76–6.50) or poor (6.51–7.25) water quality (Hilsenhoff 

1988), which is consistent with water quality and periphyton samples. 

3
 

Figure 2.1.2 Pre-implementation data for Shepherd Creek sites, comparing baseflow and 

stormflow water quality data for the years 2005 and 2006. (A) Dissolved Inorganic Nitrogen; (B) 

Total Phosphorus and (C) Extent of bacterial contamination (as Escherichia coli); note log scale 

for y axis on these plots. 

4
 

Of great interest to public health interests in stormwater and watershed management, we 

observed average fecal coliform bacteria and Escherichia coli counts derived from baseflow 

water samples that were 1–2 orders of magnitude higher than Ohio EPA’s ambient surface water 

quality criteria (e.g., mean limit 126 CFU 100 ml-1 for Escherichia coli). These high counts of 

pathogens were observed at both baseflow and, more recently, in storm flow samples; Figure 

2.1.2 (C) shows that median baseflow concentrations of Escherichia coli are highest at Sub1 

(1,400 CFU/100 mL), while median stormflow concentrations are highest at Sub2 (37,500 

MPN/100 mL). After further investigation we concluded that the most likely sources are: a) 

wastewater infrastructure, which is sometimes improperly connected from residences, leaking 

flows to stormwater conveyances; b) exfiltration from septic fields that were hydrologicallyconnected to headwater reaches in the north-central area of the watershed; and c) improper 

storage of horse manure in the lower part of the watershed. Additional investigation is needed to 

clearly identify and allocate bacterial loads among these, and possible wildlife sources. 

2.2 Assessing the source of impairment and potential for improvement 

Impervious area 

Impervious surfaces are a primary source of impairment in urban and suburban areas, 

resulting in increased stormwater runoff and reduced infiltration compared to more natural 

settings (Arnold and Gibbons 1996). This exacerbated amount of stormwater runoff translates to 

hydrologic impairments in streams such as increased volume of peak flow and storm “flashiness” 

(Konrad and Booth 2005), which subsequently alters stream morphology and sediments (Booth 

and Jackson 1997, Bledsoe and Watson 2001). Stormwater runoff also carries pollutants from 

the landscape, resulting in altered water quality in urban streams (Hatt et al. 2004). The 

combined physical effects of impervious surfaces in streams has led to impaired biotic 

communities and reduced ecosystem functioning in urban streams (Paul and Meyer 2001; Walsh 

et al. 2005b). 

Percent urban land cover and total impervious area (TIA) are commonly used as 

indicators of urban disturbance. More recently, studies have shown that the subset of impervious 

surfaces that route stormwater runoff directly to streams via stormwater pipes, called directly 

connected impervious area (DCIA), may be responsible for the majority of stream alteration due 

to urbanization (Booth and Jackson 1997, Brabec et al. 2002, Walsh 2004, Walsh et al. 2005a). 

For this project, we used a combination of field assessments, aerial photography, and GIS data to 

determine both TIA and DCIA in the Shepherd Creek watershed. 

Impervious (22.1 ha) and semi-impervious (1.8 ha) areas comprise 13.1% of the 

Shepherd Creek catchment (Catch; Figure 2.1.1). Of the impervious area, 56.3% was connected, 

although percent connectivity varied widely across parcels. Across watersheds, the lowest 

percent TIA (11.2%) and DCIA (5.4%) were at Sub4, and the highest percent TIA (19.9%) and 

DCIA (11.6%) were at Sub1. A majority of the TIA in Shepherd Creek was on private land 

(70.5%) compared to public land (29.5%). Public properties (e.g., roads, city park) encompassed 

a larger proportion of the connected (37.4%) versus disconnected (19.4%) impervious area. 

Conversely, single-family residential properties comprised a higher proportion of the total 

impervious area found to be disconnected (68.1%) than connected (42.1%). The public parcels 

and the private, multi-family residential parcels both had more than double the total amount of 

5
 

 

connected versus disconnected impervious area; whereas single-family residential parcels had 

overall lower amounts of connected than disconnected impervious area (Figure 2.2.1). 

Figure 2.2.1 Total connected and disconnected impervious area in the Shepherd Creek watershed 

based on property ownership. 

We evaluated the primary types of impervious surfaces and percent connectivity of those 

surfaces to assess types of stormwater management practices that may result in best potential for 

retrofit. The highest amounts of TIA were due to buildings (i.e., rooftops; 27.6%), driveways 

(24.6%), streets (22.7%), and parking areas (12.3%; Table 2.2.1). A majority (89.2%) of the 

streets were connected, so that streets composed the highest percent DCIA (36.0%) in the 

catchment, followed by buildings (32.9%), driveways (17.4%), and parking areas (13.5%). The 

remaining impervious surface types (e.g., sidewalks, concrete patios, etc.) comprised less than 

13% of TIA and 0.2% of DCIA. 

6
 

Table 2.2.1 Total (TIA) and Directly Connected (DCIA) Impervious Area Categorized by 

Impervious Surface Type. 

TIA DCIA % 

Surface Type (m2) (%) (m2) (%) Connected 

Building 66168 27.6 44364 32.9 67.0 

Driveway 58918 24.6 23525 17.4 39.9 

Street 54432 22.7 48551 36.0 89.2 

Parking area 29473 12.3 18144 13.5 61.6 

Sidewalk 13097 5.5 3 0.0 0.0 

Concrete 6963 2.9 211 0.2 3.0 

Wooden deck 4984 2.1 0 0.0 0.0 

Pool 2363 1.0 0 0.0 0.0 

Shed 882 0.4 12 0.0 1.3 

Other 2047 0.1 4 0.0 6.7 

Selected stormwater management practices 

Because a majority of TIA was on private property (70.5%) and in buildings and 

driveways (52.2%), we targeted private properties for installation of stormwater management 

practices in the form of rain gardens and rain barrels. Parcels in Shepherd Creek are of adequate 

size (median lot size = 880 m2 or 0.22 acres) to permit placement of rain gardens within lawns 

and rain barrels on roof gutter downspouts. Rain gardens are engineered bioretention cells that 

have porous substrate and soils designed to allow rain and snowmelt to seep naturally into the 

ground. Rain gardens typically have a concave surface to increase the capacity for holding rain 

water, and they are planted with hearty plant species that are selected for their tolerance of local 

climate and extremes in root zone water content. They are ideally located downslope of 

impervious surfaces to capture stormwater runoff generated from rooftops, driveways, sidewalks, 

and patios. By encouraging infiltration, rain gardens reduce flooding and pollution in local 

streams and rivers, and can help to recharge local water tables. Rain barrels, or cisterns, are 

tanks attached to roof gutter downspouts which are used to collect rainwater from rooftops. 

Water from rain barrels can be used to water gardens and lawns and other domestic uses and, 

therefore, may diminish other household demands on potable water. By storing stormwater 

runoff during storm events, rain barrels reduce downstream flooding. Furthermore, if barrels are 

emptied into the landscape after storms (i.e., then the soil is no longer saturated), they can 

effectively recharge local water tables. The combination of stormwater management practices 

were selected for their ease of implementation in an existing neighborhood and potential for 

addressing the major sources of impairment in the Shepherd Creek watershed. 

Potential for improvement 

Previous studies have reported that biotic impairment of streams typically occurs around 15­

20% urban land cover or 8-12% impervious surface cover (see reviews by Schueler, 1994; Paul 

and Meyer, 2001; Walsh et al., 2005b). In Figure 2.2.2, we report % TIA in each of the six 

subcatchments (black bars), and projected % TIA (effective) with various rates of stormwater 

management practice acceptance. The calculations assume that rain barrels and rain gardens 

7
 

effectively eliminate runoff effects from both rooftops and driveways. With 100% homeowner 

acceptance rates, these stormwater management practices have the combined potential to reduce 

effective impervious area in sites 2–5 from above the 8–12% impervious area threshold to well 

below the threshold (Booth and Jackson 1997). If 50% of the homeowners have stormwater 

management practices installed, it is still likely that some subwatersheds will exhibit 

improvements in stream condition. 

Some important caveats should be noted regarding the estimates of potential improvement. 

First, it is unlikely that all runoff from impervious surfaces will be routed to rain gardens and 

rain barrels, and there is a limited capacity for storing and infiltrating runoff. Detailed rainfallrunoff modeling is necessary to determine actual amounts of stormwater detained or infiltrated 

following various size precipitation events. Estimated reductions in DCIA may more effectively 

capture the potential improvements with retrofit; however, thresholds of biotic impairment for 

DCIA are limited and variable (Wang et al. 2001, Walsh et al. 2005a, Wenger et al. 2008). 

Further, there are no empirical models that provide data on expected responses of hydrology and 

water quality to changes in TIA or DCIA. Given the mechanism of stream impairment via 

stormwater runoff, we expect that changes will first be detected in surface hydrology parameters, 

followed by water quality, and, lastly, biotic assemblages. Thus, our estimates of potential 

improvement may be conservative with respect to hydrology and water quality. Finally, we 

Figure 2.2.2 Percent TIA given 0, 25, 50, and 100% landowner acceptance rates of rain gardens 

and rain barrels. 

expect the potential for detecting change to be highest in the smallest catchments (e.g., the 

stormwater outfalls and Sub1), as larger catchments are more likely to have additional sources of 

impairment and mediating factors. Although stream sampling will be necessary to determine 

actual changes associated with retrofit, it is important that our selection of stormwater 

management practices addressed the primary sources of imperviousness, and that the 

subcatchments do not have excessive amounts of imperviousness (e.g., >50%, Walsh et al. 

2005a), such that stream improvement following retrofit is possible. 

8
 

2.3 Evaluating economic incentive mechanisms 

Command-and-control 

The economic portion of the study began with a theoretical examination of the potential cost 

savings from using various market based mechanisms to provide economic incentive for 

widespread participation in a dispersed storm water retention exercise. This was a necessary first 

step because we wanted to see if there was any potential savings over current policy before 

proceeding to the actual implementation. To evaluate the cost effectiveness of various market 

mechanisms we wanted first to determine, in a case study setting, the cost of a command and 

control mechanism. Command and control is a mechanism that allows for very little flexibility 

among the regulated entity; the regulating agency sets a standard and the regulated must meet the 

standard under penalty of fines. Below we compare, in a real setting, using realistic cost and 

hydrology figures, the costs in per unit runoff detention under a command and control situation 

or either of two market based incentive mechanisms: tradable credits, and fee and rebate. We 

conclude by proposing a market mechanism that will fit legally with our study area, a 

procurement auction. 

Using the parcels from the actual Shepherd Creek area the type of stormwater management 

practice, concomitant detention cost (DC) functions and inverse cost functions, were assigned to 

parcels in the watershed based on land use and soil type to calculate what the cost would be, in 

the absence of any market incentives, to control the excess stormwater runoff from watershed 

areas with dispersed, small-scale stormwater management practices. To calculate the cost of a 

dispersed set of stormwater management practices to store all of the excess runoff discharge 

from a one and a half year storm event of 3.12 cm (1.23 inches) on site, we assigned the 

appropriate least-cost stormwater management practice technologies on a parcel-by-parcel basis 

in our small case area and solve each landowner’s cost equation. 

	 	 Parcels with residential land use and hydrologic soil group (HSG) B, which are soils of 

silt or loam, are assumed to employ sand filters. The cost function is: 

DC  26 . 6 Q0 6. 4 

Re sB + 0.126Q

	 	 Residential parcels with HSG C or D, soils with lower infiltration capabilities due to 

existence of more clay, are assumed to use rain gardens/grassed swales, the relevant cost 

function of which is DC Re sC  4.94Q + 0.126Q 

Where Q is the quantity of stormwater runoff detained in cubic feet, and second term in each is 

the log-linear estimated opportunity cost of land. We choose to not include a quadratic term 

estimated from a previous paper because while it is statistically significant, it is not economically 

significant at the stormwater management practice sizes we are concerned with. The cost 

functions are modified from Schueler (1987) and Heaney et al (2002). 

This calculation presumes that the parcel owner is responsible for all the runoff over and 

above that which would result if the parcel were in its undeveloped state. This in effect is a 

command-and-control regime with no rebate and the water detained with this constraint is 2344 

m3

 (82,767 ft3), at an average cost of $950 per homeowner. When we considered only 

construction costs of stormwater management practices, we calculated an average cost of $4.62 

per cubic foot of stormwater runoff detained via stormwater management practices over all 

9
 

 

 

 

properties in the study area. Finally, we recalculated the cost to include the opportunity cost of 

land, which was estimated from the hedonic price function and noted in the cost functions above; 

for the log-linear case this adds $0.126 per ft2

. Assuming again that command-and-control 

policy is implemented that causes all parcel owners to use stormwater management practices to 

manage all excess stormwater runoff, the recalculated cost was $6.49 per ft3, at an average cost 

per homeowner of $1337. 

Tradeable allowances 

The first hypothetical study we conducted in the Shepherd Creek area was one that 

envisioned the use of tradable credits for stormwater runoff, an idea first suggested by Coleman 

(2000). The cost effectiveness of the tradable allowance approach to pollutant reduction in 

airsheds is well established in the literature (Eheart 1980, Baumol and Oates, 1988, and 

Tietenberg 2000), and the SO2 trading program in the United States has been operating 

successfully for several years. Watersheds differ from airsheds, however, in key aspects, such as 

confinement to a channel, non-uniform mixing and downstream accumulation, and these present 

new challenges for the establishment of tradable allowance systems. Watershed trading is not a 

new concept, but the specific application explored in this paper is new. The US EPA’s Draft 

Framework for Watershed-Based Trading (1996) provides an overview of some twenty tradable 

allowance programs across the United States. Several of these grew out of cooperative 

agreements with the US EPA, the Water Environment Research Foundation, and various local 

stakeholder groups. These programs focus on reducing concentrations of nutrients or toxics, and 

most rely upon an organizational effort similar to US EPA’s total maximum daily load (TMDL) 

process to drive stakeholder involvement. 

Two necessary conditions for tradable allowance regimes to be cost reducing are that: i) 

transactions costs of such programs be no greater than the gains achieved and ii) there be 

sufficient difference in abatement cost across parcel owners so that potential cost savings can be 

realized through market exchange of runoff control. With these conditions satisfied, a tradable 

allowance system can efficiently assign runoff control to dispersed locations and may avoid the 

larger cost of centralized approaches. 

The usefulness of inclusion of opportunity costs can hardly be overstated in this 

application. We use the results of our opportunity cost estimation1

 to inform a tradable 

allowances system much like those currently used in water quality trading programs around the 

country (USEPA 2003). Figure 2.3.1 compares, for the Shepherd Creek Pilot project, the perunit runoff reduction costs faced by homeowners under assumptions of different credit prices, 

and inclusion or exclusion of opportunity costs. Not surprisingly when opportunity costs are 

ignored all costs are lower. The cost line named “18-mile tunnel” represents the costs per unit of 

detention in a proposed large infrastructural stormwater conveyance system that is under 

consideration by the Metropolitan Sewer District for the city of Cincinnati2

. 

1

 Thurston (2006) describes in detail how a Hedonic price function is estimated to approximate the opportunity cost
 


of dedicating land to Stormwater management practices for stormwater runoff control. 
 2

 It should be noted that the tunnel would serve a much larger population than the Shepherd Creek Pilot project area, 
 

which is used in the other calculations. 
 

10
 
 

 

 

Costs of Runoff Detention

 Using Tradable Allowances 

0 

2 

4 

6 

8 

10 

12 

14 

2.5 5 8 15 C & C 

Allowance Price 

$/CF 

O.C.= $0 

O.C.= $0.13 

O.C.= $0.28 

18 mile tunnel 

Figure 2.3.1 Costs of runoff detention with Tradable Allowances 

Fee and rebate 

We also considered the potential application of a fee and rebate system. An efficient tax 

on pollution should be a direct tax that equals the marginal external damages (Pigou 1962). But 

directly taxing pollution is complex, especially when monitoring is difficult (such as with a nonpoint source) or when there are institutional barriers to imposing differing taxes on different 

people in the same area. Fullerton and Wolverton (1999, 2003) note that when directly taxing 

the pollution is not an option, the policy maker can exploit the relationship the optimal pollution 

tax has with income tax and rebates on products that are related to, and relatively cleaner than the 

polluting good. 

This type of policy is already in place in many municipalities in the United States (Doll et 

al 1998, Doll and Lindsey 1999), but these programs are almost exclusively for commercial 

properties. Where residential fees are in place they tend to be too small to either promote abating 

behavior or warrant a rebate. For example, monthly residential stormwater fees in Columbus, 

OH, St. Louis, MO, and Indianapolis, IN are about $2.70, $0.24, and $1.25 respectively. Many 

agree that the existing programs have not encouraged the desired behavior because the fees and 

rebates are simply too low (Doll and Lindsey 1999). If the fee and the rebate are high enough to 

make households reflect their true underlying preferences, based on our knowledge of the costs 

facing the residential property owner, a stormwater runoff reduction goal can be met using 

dispersed stormwater management practices and a two part instrument at a relatively low cost to 

the utility and at a low per-unit cost to the average stakeholder. We include the opportunity costs 

11
 

 

of land into the calculated the fee and rebate scenario for the Shepherd Creek watershed which 

makes the model more realistic. But we find that to substantially increase people’s participation 

in stormwater infiltration practices, the fees and rebates have to be orders of magnitude larger 

than those that are currently in use. 

Auction 

There are a variety of legal barriers to implementation of most incentive mechanisms. 

These barriers stem mostly from language in the Clean Water Act (CWA) of 1972, and “takings” 

issues. The CWA provides no regulatory “stick” for policy dealing with water quantity as it is 

only regulated under specific circumstances. Tradable credits are simply not tested as they have 

just recently been recognized by the EPA as a means to control stormwater runoff. Furthermore, 

this recognition comes in the form of relatively weak support in the EPA Water Quality Trading 

Policy (EPA 2003). Imposition of a “cap” on a watershed’s runoff, and the consequent 

requirement for attainment through impingement on established property rights is recognized as 

a takings issue. As for a fee and rebate program, although we have shown it to be economically 

feasible, existing fees are not tightly tied to excess runoff, and imposition of sufficient fees 

(much like the imposition of the cap in the trading scenario) would not be politically feasible. 

Thus, we turned to a wholly voluntary economic auction approach designed to encourage 

landholders to install stormwater management practices so as to control runoff without 

necessitating a legal mandate. 

There are essentially four types of auctions, English, Dutch, first-price sealed bid, and 

Vickrey. The English auction is the type of auction most people are familiar with. An auctioneer 

calls out prices sequentially higher and players bid until only one remains, then that person pays 

the highest price called. In the Dutch auction the auctioneer calls out bids in descending order 

until the price reaches that which one person is willing to pay, and that person wins the item at 

that price. In a first price sealed bid auction bids are submitted without other bidders seeing 

them and the highest bidder wins. The Vickrey auction (named after William Vickrey, the first 

person to investigate some of the nuances of auction theory) is similar to the first price sealed bid 

auction, but the winning bidder pays the price that the second highest bidder bids. Using 

rigorous mathematical proofs these mechanisms have been proven to all be “revenue 

equivalent,” that is that they all theoretically elicit the same winning price; although 

experimental and experiential evidence is mixed. Revenue equivalence and other theoretical 

characteristics of auction such as efficiency conditions, revenue equivalence, or pareto efficient 

allocation at a Bayesian Nash equilibrium are not in the scope of this paper to go into. The 

theoretical underpinnings of auctions have been well defined in the economics and game theory 

literature and are treated rigorously elsewhere. The auction we use is a variant of the first price 

sealed bid auction, known as a reverse or procurement auction. In this case the auctioneer is the 

one who wants to buy the item and there are many sellers. We describe this type of action in 

detail below. 

Regardless of the type of auction, auctions are viewed as superior to other means of 

allocating public resources due to their efficiency, objectivity, transparency, and flexibility 

(CSIRO 2005). They are efficient because they will allocate the resource to those who are 

willing to pay the most and therefore are situated to make the best use of them. Objectivity is 

12
 

achieved because the price is not determined capriciously by a government official, rather it is 

market determined. The auction process is transparent because the rules for bidding and winning 

are known. Finally, auctions are flexible in that the mechanism can be altered to allow for 

various contingencies, such as changing annual budgets (CSIRO 2005). 

Using market mechanisms as incentive for pollution control has increased in popularity 

over the years because they allow flexibility among the regulated which can decrease overall 

policy cost to society. Market mechanisms also act as an organizing device through which 

transactions costs to the policy maker or regulating agency are decreased. We have assumed that 

the policy maker has at his disposal several mechanisms that range, in order of increasing 

flexibility: command and control, tradable credits, fee and rebate and auctions. The choice of 

which mechanism to employ depends heavily on the situation and the legal obstacles and 

ecological goals of the program. 

13
 

 

CHAPTER 3 Stream Monitoring Design 

3.1 Experimental design 

The project uses a before-after control-impact site design (Underwood 1994), where the 

“impact” is the installation of parcel-level stormwater management practices. We established six 

hydrologic, water quality, and ecological monitoring sites in the watershed (Table 3.1.1), four of 

which are receiving streams for the stormwater management practice installation area (Sub1, 

Sub2, Sub3, and Catch), and two which are control watersheds that will not receive stormwater 

management practices (Sub4 and Sub5). Stream sampling sites were monitored for a minimum 

of two years prior to installation of stormwater management practices (Summer 2007) and will 

continue to be monitored for three years following the last installation (Summer 2008). In 

addition to sampling locations along main tributaries of Shepherd Creek, there are 3 

neighborhood sites (N1, N2, and N3) at stormwater outfalls of residential areas and that are 

monitored for hydrology. Sampling locations for hydrology, water quality, and/or ecology are 

mapped in Figure 3.1.1. 

The original study design consisted of five ecological and water quality sampling sites 

(Sub1, Sub2, Sub3, Sub5a, and Catch). The sampling location for the control site moved from 

Sub5a to Sub5 in 2005 after two years of pre-implementation sampling. The site was re-located 

downstream because: 1) Sub5a lacked adequate baseflow for proper sampling during dry times 

of the year, 2) the hydrologic monitoring station was located at Sub5, and 3) the larger drainage 

area at Sub5 was more comparable to the other sites. Ecological and water quality data collected 

from both Sub5 and Sub5a in 2005 compared well, although stormwater samples were not 

collected at Sub5a. We also added a second control site, Sub4, in spring/summer of 2005. 

Table 3.1.1 Start dates for hydrology, water quality, and ecology monitoring. 

Site 

Sub1 

Type 

Treatment 

Hydrology 

Fall 2004 

Water Quality 

Baseflow, Spring 2004 

Stormflow, Summer 2005 

Ecology 

Spring 2003 

Sub2 Treatment Fall 2004 Baseflow, Spring 2004 

Stormflow, Summer 2005 

Spring 2003 

Sub3 Treatment Fall 2004 Baseflow, Spring 2004 

Stormflow, Summer 2005 

Spring 2003 

Sub4 Control Summer 2005 Baseflow, Spring 2005 

Stormflow, Summer 2005 

Spring 2005 

Sub5 

Sub5a 

Catch 

Control (replaced 

Sub5a) 

Control 

(decommissioned 

Spring 2006) 

Treatment 

Fall 2004 

N/A 

Fall 2004 

Baseflow, Summer 2005 

Stormflow, Summer 2005 

Baseflow, Spring 2004 

through Summer 2005 

Baseflow, Spring 2004 

Stormflow, Summer 2005 

Summer 2005 

Spring 2003 

Spring 2003 

N1 

N2 

N3 

Treatment 

Treatment 

Treatment 

Spring 2006 

Spring 2006 

Spring 2006 

N/A 

N/A 

N/A 

N/A 

N/A 

N/A 

14
 

Figure 3.1.1 Location of sites for various sampling activities in the Shepherd Creek watershed. 

15
 
3.2 Hydrologic monitoring 

Hydrology is a “master” variable that drives dynamics in other aspects of watershed 

structure and function (Konrad and Booth 2005), and its characterization is key to understanding 

watershed dynamics and any impact that the LID retrofits might have. For this project, we set up 

a gaging network to measure flows at stormwater outfalls (neighborhood sites) and within 

streams at various locations within the watershed, thus capturing the spatial hydrology of the 

watershed. 

Stream stage is measured at intervals of 5 minutes or less, so as to better resolve storm peaks 

and transient characteristics of stormflow in urbanized watersheds. Flow controls were designed 

for each site and implemented as either broad-crest with v-notch weirs in natural stream reaches, 

or as semi-elliptical plate weirs for the site with pipe culverts. Flow depth at each gage is 

measured with bubbler-type stage measurement devices (Design Analysis H350XL; Logan UT). 

Depth is converted to discharge with a site-specific stage-discharge relationship that has been 

determined over multiple years with episodic manual measurements made at different water 

depths during both baseflow and storm flows. Flows at the outlet of the watershed (Catch) are 

realized as mean daily flows only. The cost was prohibitive to establish a proper flow control at 

this large a stream cross-section, and so discharge is therefore estimated via an empirical 

relationship between flows explicitly measured at Sub2, Sub3, and Sub5, and accounting for the 

increase in drainage area and cross-sectional dimensions. We also used peak flow data derived 

from crest-stage gages (which passively mark and record flow depth at peak storm discharge) 

and converted into discharge values through modeling with USACE HEC-RAS (River Analysis 

System) to refine the empirical model for Catch. 

Rainfall is measured at four locations around the watershed: 1) in the northeastern part of 

the watershed (operated by Hamilton County), 2) in the centroid of the watershed near Sub3, 3) 

in the eastern part of the watershed at Mt. Airy Arboretum, and 4) along the eastern edge of the 

watershed (near the police station). Rainfall data is gathered with tipping-bucket-type rain gages 

with 0.01” sampling resolution. Tip data is truncated to 5-minute intervals, and all time bases are 

coordinated and referenced to Greenwich Mean Time (GMT). In 2008, we also installed an 

integrated evapotranspiration measurement system (Campbell ET107 station; Logan UT), which 

we use to generate estimates of hourly evapotranspiration data. 

3.3 Water quality monitoring 

Urbanization causes significant changes in water chemistry that are regulated under the 

Clean Water Act, to the extent that these changes have the potential to harm human health and 

impair biological condition (Paul and Meyer 2001). Table 3.3.1 lists each of the water quality 

parameters sampled for the Shepherd Creek sites, and the potential sources and impairments 

associated with each parameter. Water quality and chemistry sampling were conducted monthly 

under baseflow conditions, on or near the 15th day of the month throughout the year. Water 

quality sampling was performed in conjunction with ecological data collection when feasible, 

and followed baseflow protocols defined as no significant rainfall (i.e., >1 mm) in the 72 hours 

prior to sampling. The sampling dates and times were subject to modification due to inclement 

weather, or other environmental or climatic conditions deemed unsafe. 

16
 
 

 

Water quality baseflow samples were collected in clean bottles (I-Chem, HDPE 

Environmental Sample bottles) as grab samples or field-filtered during collection using a 

peristaltic pump (Geopump Series II, Geotech Environmental Equipment), Teflon sample tubing 

and in-line filter holders (47mm; with 0.45 μm Millipore Durapore membranes) for dissolved 

constituents. Samples were preserved by acidification (as needed, depending on the type of 

analysis) and shipped on ice, overnight, to U.S. EPA’s Central Regional Laboratory for most 

analyses. Alkalinity was determined using EPA Method 310.1; organic carbon analysis via EPA 

Method 415.1 (high temperature combustion); anions were determined by ion chromatography; 

nutrients by automated colorimetric methods (EPA Methods 353.2, 350.1, 351.2 and 365.4); and 

metals and cations by ICP-AES (EPA Method 200.7 and 200.2). Suspended sediment 

concentration was determined in-house following ASTM Method D 3977-97. For each baseflow 

sample, in-situ water quality parameters (temperature, dissolved oxygen, etc. as indicated in 

Table 3.1.1) were measured using a YSI 6600 Water Quality sonde. 

In addition to monthly baseflow sampling, periodic stormflow samples were collected at a 

frequency of 6–8 storms per year, with a goal of sampling 2 storm events per season. Stormflow 

samples can be used to estimate pollutant loads from nonpoint source runoff and provide water 

quality data at high flow conditions. For each storm event, 4–6 samples per site were collected 

using automated samplers (Teledyne-ISCO Model 6712; timed or triggered from changes in 

depth or turbidity signals from YSI 6600 Water Quality sondes). Stormflow samples were 

analyzed using the same methods described above for baseflow samples, except that filtration 

was performed in the laboratory. Samples were split for analysis as needed using a Dekaport 

Teflon Cone Sample Splitter (Geotech Environmental Equipment). 

Table 3.3.1 Summary of water quality monitoring parameters and associated impairments. 

Water Quality 

Category 

Constituents to be Monitored Potential Sources in 

the Watershed 

Potential Impairments 

In-situ water Temperature, Specific General condition pH critical for determining 

quality monitoring Conductance, Dissolved Oxygen, assessment used to metal speciation; 

(YSI 6600) pH, ORP, Turbidity support specific 

parameter analyses 

Conductivity is a surrogate 

for chloride; Turbidity is a 

surrogate for suspended 

sediment 

Sediment Suspended Sediment Concentration 

(SSC); Turbidity; Particle Size 

Distribution 

Erosion, both hillslope 

and channel; Runoff 

from impervious 

surfaces 

Changes to sediment regime 

may degrade the physical 

habitat in streams; 

Sediment-associated 

contaminants may impair 

biological condition 

Nutrients Dissolved Inorganic Nitrogen 

(DIN; NO3-N+NO2-N); Ammonia 

(NH4-N); Total Kjeldahl Nitrogen 

(TKN); Total and Total Dissolved 

Phosphorus (TP and TDP) 

Lawn and garden 

fertilizers; Human and 

animal waste 

Excess nutrients may cause 

localized eutrophication; 

Export of nutrients to more 

sensitive waterbodies may 

promote eutrophication 

17
 

 

Organic Carbon Total and Dissolved Organic 

Carbon (TOC and DOC) 

Runoff from lawns and 

gardens and inputs 

from riparian 

vegetation; In-stream 

primary production; 

Wastewater 

Degradation of excess OC 

may cause localized hypoxia 

or anoxia 

Ions and Anions: Cl-

, Br-, F-, SO4 

2-, NO3 -

, Natural weathering; Changes in ionic strength 

Alkalinity PO4 

3-; Cations: Na+

, Mg2+, K+ , 

Ca2+; Alkalinity (mostly HCO3 

-

) 

Fertilizers; Road salt; 

Wastewater 

may alter contaminant 

speciation; Decreased 

alkalinity limits capacity to 

buffer inputs of acidic 

wastewater; Clcan be a 

chronic or acute stressor 

Metals Total and Dissolved Fe, Mn, Al, 

Cu, Zn 

Roadway and rooftop 

runoff; Wastewater 

Excess may cause 

impairment of biological 

condition (chronic/acute 

toxicity) 

Microbiology Enterococci, Fecal Coliforms, 

E.Coli 

Human and animal 

waste 

Bacteria may impair human 

health and present a contact 

hazard 

3.4 Ecological monitoring 

We designated 61 m (200 ft) reaches at each site for sampling periphyton, benthic 

macroinvertebrates, and physical habitat. Pre-treatment sampling began in 2003 and sampling 

will continue for three years following the installation of stormwater management practices. 

Sites were sampled for all parameters five times per year, approximately 6 weeks from April 

through October. An additional, quantitative bucket method for sampling benthic 

macroinvertebrates occurred 3 times per year associated with the spring, mid-summer, and fall 

sampling events. An overview of the types of samples collected is provided in Table 3.4.1, and 

sampling methods are described below in more detail. 

Table 3.4.1 Summary of samples collected and sampling resolution. 

Sample Type Data collected Data resolution Output/Indices Reference 

Periphyton (50 mL) Biomass 5 times per year (every 

6 weeks Apr.-Oct.) 

dry mass, ash-free dry 

mass 

Barbour et 

al. (1999) 

Periphyton (~400 

mL) 

Taxonomic ID and 

abundance (cell and 

natural units) 

5 times per year (every 

6 weeks Apr.-Oct.) 

richness, diversity, 

composition, tolerance, 

multimetric indices, etc. 

Barbour et 

al. (1999) 

Periphyton (2 glass 

fiber filters) 

Chlorophyll a 5 times per year (every 

6 weeks Apr.-Oct.) 

chlorophyll a 

concentration 

Barbour et 

al. (1999) 

18
 

 

Benthic 

macroinvertebrates 

(triangular dip net) 

Taxonomic ID, 

abundance, and 

length 

5 times per year (every 

6 weeks Apr.-Oct.) 

richness, diversity, 

composition, tolerance, 

multimetric indices, etc. 

Barbour et 

al. (1999) 

Benthic 

macroinvertebrates 

(bucket sampler) 

Taxonomic ID, 

abundance, and 

length 

3 times per year (April, 

July, October) 

richness, diversity, 

density, biomass, 

composition, tolerance, 

multimetric indices, etc. 

Fritz et al. 

(2006) 

Physical 

characterization 

and habitat 

assessment data 

sheets 

Ranking of physical 

attributes of sampling 

sites 

5 times per year (every 

6 weeks Apr.-Oct.) 

Qualitative Habitat 

Evaluation Index (QHEI), 

separate habitat metrics 

Barbour et 

al. (1999) 

Periphyton 

Periphyton samples were collected from ~12 cobbles selected randomly from pool and 

riffle habitats throughout the reach. Cobbles were removed from the stream and a designated 

11.4-cm2

 ring (PVC circle) on each rock was brushed with a toothbrush for ~2 min. Rocks and 

brushes were then rinsed with stream water into a 500-mL bottle. Periphyton from all rocks 

within a reach were composited into a single bottle and placed in the dark on ice. In the lab, 

samples were split for three analyses: chlorophyll a, algal biomass, and periphyton identification. 

First, the total volume of the sample was measured and recorded. The sample was shaken and 

homogenized prior to every 10 mL of sample removed. A minimum of 30 mL was filtered onto 

each of two glass fiber filters and frozen for analysis of chlorophyll a using a multi-wavelength 

spectrophotometer (Arar 1997). Both the biomass sample and the remaining sample for 

periphyton identification were preserved with a 1% solution of gluteraldehyde. For biomass 

analysis, 50 mL of sample was filtered onto a pre-ashed glass fiber filter (47 mm, PALL Type 

A/E, 1-μm pore size). Filters were dried for 24 hours at 105oC to a constant weighted and then 

ashed in a muffle furnace for 1.5 hours at 500oC to obtain ash-free dry weight. Periphyton cells 

(300 ±10%) were identified to genus level and densities were reported as both cells and natural 

units per cm2. 

Macroinvertebrates 

Benthic macroinvertebrates were collected using two methods: qualitative kick samples 

and quantitative bucket samples. The kick sample method was adapted from EPA’s Rapid 

Bioassessment Methods and designed to capture the diversity of macroinvertebrates by sampling 

habitat types according to their dominance in the stream reach (Barbour et al. 1999). Qualitative 

kick samples were collected by kicking or otherwise disturbing the substrate over the entire reach 

and collecting invertebrates and debris in a triangular net (0.5-mm mesh). The quantitative 

bucket sampler (Fritz et al. 2006) was designed to sample a fixed area and does not require flow 

for adequate performance. Samples were taken from three haphazardly-selected locations within 

riffle habitats (rocky pools if riffles are dry). A five-gallon bucket (0.053 m2

) with the bottom 

removed was driven into the stream bed 3-5 cm deep. Using a trowel, the bed sediment was 

disturbed to 10 cm for 10 seconds, and a dip net (0.5-mm mesh) was used to remove the 

suspended material. Material was placed into a wash basin and the procedure was repeated two 

19
 

more times. For both the qualitative and quantitative samples, organic material was elutriated in 

a bucket to remove inorganic material, sieved, and preserved in 70% ethanol. Bucket samples 

were kept separate for identification of macroinvertebrates. Three hundred individuals (± 10%) 

per sample were counted, measured, and identified to genus level. 

Physical habitat 

General morphometric, geomorphic, and water quality parameters were measured within 

the 61-m sample reach during ecological sampling. Physical attributes measured included visual 

estimates of: % riffle, % pool, % run, average width, average depth, wetted area, surface 

velocity, large wood density, % small wood, % large wood, % detritus, bed texture (% bedrock, 

cobble, gravel, sand, silt), and % canopy cover. Water quality measurements were taken with a 

YSI multi-probe, and included: water temperature, conductivity, dissolved oxygen, pH, 

oxidation-reduction potential, and turbidity. Finally, we calculated two visual assessment habitat 

evaluation scores: EPA’s Rapid Bioassessment Protocols Quantitative Habitat Assessment 

(QHEI), and the Primary Headwater Habitat Evaluation Form (HHEI) that is specifically 

designed for streams with water depths <40 cm (Barbour et al. 1999). Visual assessments 

included ten parameters: substrate, pool depth, bankfull width, riparian zone width, vegetative 

protection, bank stability, flow regime, sinuosity, bed stability, embeddedness, and channel 

alteration. 

An additional geomorphic assessment was conducted once during the pre-treatment phase 

(Fall 2004) and will be repeated in 2010 (post-treatment). Cross-section profiles were taken at 

several locations along the stream reach using an electronic total station (Trimble 5600 Direct 

Reflex, Dayton, OH). The number of cross-section surveys made was dependent upon the 

number of breaks between reach areas with contrasting or changing geomorphic properties. The 

total station was also used to generate bankfull and water surface longitudinal surveys. Bank soil 

was collected at locations where cross sectional surveys had been made. Soil samples were dried 

and analyzed in the laboratory for particle size distribution. Finally, a pebble count (Harrelson 

et al. 1994) was conducted at 100 random locations along the thalweg to determine particle size 

distribution and median particle size (D50) for the reach. 

20
 

CHAPTER 4 Auction Design 

4.1 Background 

Within the treatment areas of the Shepherd Creek watershed, rain barrels and rain gardens 

were distributed to homeowners using an auction mechanism. There are approximately 350 

parcels, each of which was offered the opportunity to receive stormwater management practices 

free of charge. Apartment buildings (11 within 2 apartment complexes) were also eligible to 

receive stormwater management practice free of charge; however, apartment owners were 

approached separately and were not included in the auction. 

We conducted the procurement auction design which is consistent with the types of 

auctions currently being used by federal, state, and local agencies for the purposes of land 

conservation. We determined a base amount of money to be used for the auction, and 

stormwater management practices were allocated based on that limit. All homeowners within 

the pilot area were provided fair and equal opportunity to participate in the auction. 

We use a sealed bid, first price, discriminative price auction, where bids are further 

tempered by the environmental weighting index, and are accepted up to the cumulative 

reservation price of the agency. A non-uniform price auction is employed because of its 

theoretical “truth-revelation” properties, which should induce an optimal bidding strategy and 

will reflect the actual opportunity cost of stormwater management practice adoption. All eligible 

participants received background information (described below) and those wishing to adopt 

stormwater management practices submitted bids. The goal was to pay those landowners who 

adopt the most effective best management practices at the lowest price. The auction was run in 

the spring 2007and repeated in spring 2008, and resulting in actual payouts and installations of 

rain gardens and rain barrels. The auction, installations, and maintenance were contracted to 

TetraTech, Inc.; however, we assessed the auction bids and performed all monitoring. 

4.2 Information to homeowners 

Potential participants received two direct mailings detailing the function and uses of the 

rain gardens and rain barrels, and the auction process. The first mailing included a cover letter 

and informational brochure (Figure 4.2.1), which was intended to notify the landowners in the 

watershed of the opportunity to participate in the Shepherd Creek project. The second mailing 

was sent out two weeks after the first and contained a cover letter, a copy of the informational 

brochure, an auction bid form (Figure 4.2.2), a self-addressed, stamped envelope. All recipients 

also received nominal financial compensation ($5) to encourage bidding and compensate 

homeowners for their time. In 2007, due to the novelty of the project, we used door hangers to 

inform homeowners of the forthcoming mailing. We also extended the auction for 2-3 weeks 

and sent an additional letter with another copy of the bid form. Homeowners were directed to 

the project website (www.mtairyraincatchers.org) or a contact phone number for additional 

information. 

21
 

Figure 4.2.1 Brochure sent to eligible homeowners. 

22
 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

REVERSE AUCTION FORM - MT. AIRY RAIN CATCHERS
 


FUNDED BY THE U.S. ENVIRONMENTAL 
 

PROTECTION AGENCY WITH ASSISTANCE FROM
 


CONTRACTOR TETRA TECH EM, INC.
 


A few weeks ago, we sent a form to bid on a rain barrel and/or rain garden to Mt. Airy 

residents. We have received many bids, but have also heard that some residents had 

questions about the process, so we have extended the deadline on bidding. 

If you did not respond last time because you are not interested, we understand and 

thank you for your time: please disregard this second mailing. But, if you didn’t respond 

because you had a question or thought your property wouldn’t be eligible (all properties 

in the area will be considered and would provide environmental benefits) we are glad to 

give you this second opportunity. 

To bid, please complete this form and send it back to us in the enclosed envelope by 

May 9th. If you have any questions at all, please contact Mike at 241-0149 or 

Michael.valerius@ttemi.com. There is more information at www.mtairyraincatchers.org. 

EPA and Tetra Tech will select winners of the auction based on the amount of the bid 

(lower bids are more likely to be accepted) and the potential environmental benefits 

based on where you live. If you are selected, you will receive the rain catcher(s) for free 

plus a one-time payment equal to your bid amount. 

Bid amount for rain garden (amount you will receive if selected): 

 $0  $250 

 $50  other amount 

 $100 

 $150 

Bid amount for rain barrels (amount you will receive if selected): 

 $0  $150 

 $50  $250 

 $100  other amount 

Number of barrels requested 

 Name:

 Address: 

Phone: Email: 

Preferred contact method (email, regular mail, phone): 

Please send us your comments on this process, even if you do not bid: 

Figure 4.2.2 Auction bid form included in second mailing. 

The back of the form had map of the parcel, house, driveway, etc. and asked the 

homeowner to indicate their preferred rain garden location. 

23 
 

 

 

A. C. 

B. 
 

In addition to the information mailed to homeowners, a demonstration rain barrel and two 

rain gardens were installed in Fall 2006 at the Mt. Airy Arboretum, a public park area within the 

Shepherd Creek watershed. The rain gardens had signage explaining the project and the 

stormwater management practices (Figure 4.2.3). 

Figure 4.2.3 Pictures of demonstration rain barrel (A), rain garden (B), and signage (C). 

24
 

 

 

 

 

 

4.3 Methods for assessing auction bids 

To rank auction bids for stormwater management practices, we considered each eligible 

parcel’s total impervious area, rooftop connectivity to sewer pipes, the predominant soil type, 

and distance from a stream based on GIS data. Our scoring procedure weighted bids from a 

procurement auction with the above-listed environmental criteria to systematically place rain 

gardens and rain barrels in the watershed. Individual auction bids were assessed for their relative 

acceptability based on the cost of installation (C), the bid price (B), and the environmental 

benefit index (EBI). Bids for rain gardens and rain barrels were evaluated and ranked separately. 

For the purposes of ranking bids, C was assumed to be uniform across properties, and was 

estimated to be $1500 for each rain garden and $250 for each rain barrel, such that: 

 (i) Cgarden = $1500 

 (ii) Cbarrel = $250 × # barrels 

The overall rank (R) for rain gardens and rain barrels is designed to give weight to the bid 

price, in order to appropriately reward lower bids, which is reflected in B/EBI. Equally 

important is the actual cost of installing the rain gardens and rain barrels, and this is reflected in 

C/EBI. Importantly, the potential environmental benefits are included in both portions. In order 

to give equal weight to the two calculations, they are normalized by the maximum value across 

all bids, and further scaled from 1-100. The equation for ranking, which is to be calculated 

separately for rain gardens and rain barrels, is as follows: 

R = (((B÷EBI) ÷ Max(B÷EBI)) + ((C÷EBI) ÷ Max(C÷EBI))) × 50 (iii) 

Environmental valuation provides a basis for assessing the potential environmental 

benefits resulting from stormwater management practice installation. The variable set was 

developed based on the potential beneficial environmental impact on the receiving stream. In 

addition, all variables can be evaluated using Geographic Information System (GIS) software 

and do not require individual site visits, which would constitute a major undertaking. The 

environmental values were determined from sum of likewise weighted and property-specific 

characteristics, which are detailed below for rain gardens and rain barrels. 

Beyond these objective criteria, there was also potential for bid refusal based on the 

location of the stormwater management practice on the property. Because the goal of the project 

is to mitigate stormwater runoff within the Shepherd Creek watershed, any barrel or garden that 

would be located such that it benefits areas outside of Shepherd Creek was not accepted. This 

was the case for the few bids from households on the watershed’s border. For the rain barrels, 

this can largely be determined on GIS (i.e., if the rooftop is outside of the watershed, the bid will 

be refused). However, if there are roof downspouts inside and outside the watershed, then bids 

were only be accepted if the homeowner agreed to put the barrel on a downspout inside the 

watershed (determined during field visits). For the rain gardens, the homeowners indicated their 

preferred location on the bid form; however, the precise location was based on field evaluations 

and discussions with the homeowner. If the field crew determined that the garden would have no 

25
 

 

 

 

benefit or minimal benefit for the watershed, for example if the house’s back yard sloped into the 

adjacent watershed, the bid was refused. 

Environmental Benefits Index (EBI) 

The scoring process was designed to be a simple, informative, and repeatable technique 

for quantifying the potential environmental value of placing stormwater management practices 

on the property. This allows for objective comparison of landowner bids based on the potential 

environmental benefits and utilizes available GIS information. Variables were scored for each 

property, with high numbers indicating a preferred condition. The rationale and scoring for each 

variable is detailed below. 

Rain Gardens 

The environmental value of rain gardens was based on the amount of stormwater runoff 

potentially infiltrated and the proximity of property to a stream channel. Potential infiltration of 

runoff was determined using percent total impervious area (TIA) on the parcel and soil drainage 

characteristics. Environmental value for rain garden installation will be maximized where: there 

is high % TIA on the parcel, soils have comparatively low capacity for drainage, and the 

property is in close proximity to stream channels. Scoring criteria for each variable are detailed 

in the next section. The following formula was used to create a linear combination of variable 

scores for the environmental weighting. TIA is expected to be twice as important for influencing 

runoff quantity (and hence, environmental valuation) compared to the other two variables, and is 

likewise reflected in the coefficient. 

EBIgarden = 2(TIA score) + (Soil score) + (Proximity score) (iv) 

Calculation of scores: 

1) Percent total impervious area 

Total impervious area (TIA) is the area of land that is covered by rooftops, driveways, 

sidewalks, pools, or other surfaces that do not allow for water to infiltrate into the ground. 

Parcels with a high percent of total area as TIA received higher scores because these areas 

presently have the least opportunity for infiltration, and would therefore benefit the most from 

rain gardens. Parcel-level TIA was available as GIS layers of rooftops, driveways, and 

sidewalks which were digitized from 2001 aerial photography (specifically, ortho-rectified 

images), and updated with recent site-specific surveys (ca. 50% of the properties). 

Variable Description: TIA Score 

>30% parcel area as TIA 4 

15-30% parcel area as TIA 3 

5-15% parcel area as TIA 2 

<5% parcel area as TIA 1 

26
 

2) Soil drainage characteristics 

Soil series differ in terms of capacity to infiltrate precipitation and surface runoff. 

Therefore, the dominant soil series on the parcel was used to estimate the existing capacity for 

drainage for a given parcel. For parcels in this watershed the dominant soil types are 

Switzerland silt loam, which has moderate drainage characteristics; and Eden silty clay loam, 

which has relatively poor drainage characteristics. Where the soils have been modified due to 

urban disturbance (UELC = urban Eden land complex; USLC = urban Switzerland land 

complex), they are assumed to have slightly less infiltrative capacity compared to the 

undisturbed soils, and are scored accordingly. Parcels where the dominant soils have poorer 

drainage characteristics were given preference for receiving a rain garden because these 

properties are likely to generate a greater amount of surface runoff, and would likely benefit the 

most from having a rain garden. A detailed soil survey map created by the Natural Resource 

Conservation Service was used to determine the dominant soil series for a given parcel. Scoring 

was as follows: 

Variable Description: Soils Score 

Dominant soil type has low infiltration capacity (UELC) 4 

Dominant soil type has med-low infiltration capacity (Eden) 3 

Dominant soil type has med-high infiltration capacity (USLC) 2 

Dominant soil type has high infiltration capacity (Switzerland) 1 

3) Proximity to stream channel 

The proximity of a parcel to a stream channel is inversely proportional to the area of land 

available to act as a buffer for upstream developed land. The closer the parcel is to the stream 

channel, the fewer opportunities for infiltration of runoff, and therefore an increased potential for 

runoff contributing to peak flows in the stream channel. Properties that are closer to the stream 

would be expected to benefit the most from a rain garden acting to intercept and infiltrate surface 

runoff. The stream network determined from 2 ft. Digital elevation maps (DEMs) was used to 

calculate the distance between the centroid of the parcel and the stream channel following the 

flow path. Scoring proximity was as follows: 

Variable Description: Proximity Score 

Centroid of parcel <50 m from stream channel 4 

Centroid of parcel 50-100 m from stream channel 3 

Centroid of parcel 100-150 m from stream channel 2 

Centroid of parcel >150 m stream channel 1 

Rain Barrels 

The environmental value of rain barrels was based on the potential amount of water that 

would otherwise be lost to direct connection or conveyance to storm sewers. Environmental 

value will be maximized where 1) higher numbers of barrels were requested, and 2) the roof 

gutter downspouts were wholly or in-part connected to storm sewers. The environmental 

weighting of rain barrels are therefore calculated accordingly: 

EBIbarrel = # barrels × Rooftop connectivity score (v) 

27
 
The proportion of rooftop area that is directly connected to storm sewer pipes reflects the 

potential for precipitation to be stored in rain barrels rather than contributing directly to peak 

flows in streams. Thus, properties with higher connectivity of rooftops to storm sewers received 

higher scores, because runoff from these areas are currently routed directly into streams and 

could benefit the most from storage in rain barrels. Rooftop connectivity was determined using a 

combination of local storm sewer pipe information, a rooftop data layer digitized from 2001 

ortho-rectified aerial photography, and site-specific surveys of roof gutter downspouts (ca. 50% 

of properties surveyed and 50% estimated from neighboring lots). Rooftop connectivity was 

scored as follows: 

Variable Description: Rooftop connectivity Score 

75-100% connectivity of rooftops to storm sewers 4 

50-75% connectivity of rooftops to storm sewers 3 

25-50% connectivity of rooftops to storm sewers 2 

0-25% connectivity of rooftops to storm sewers 1 

28
 

 

CHAPTER 5 Auction Results 

5.1 Phase 1, Year 2007 

Of the ~350 eligible homeowners, we received 57 bids for rain gardens and 61 bids for a 

total of 121 rain barrels (Table 5.1.1). Most homeowners bid for both rain gardens and rain 

barrels (47), although there were some bids for just gardens (10) and some for just barrels (16; 

Figure 5.1.1). Bids ranged from $0 to $500, with a mean bid of $50.27 for a rain garden and 

$32.06 for a rain barrel. Interestingly, a majority of bids were $0, indicating the willingness of 

homeowners to receive stormwater management practices for free without any additional 

compensation (Table 5.1.1). 

Table 5.1.1 Summary of bids for rain gardens and rain barrels in 2007 and 2008 

2007 2008 Total % Change 

Rain gardens 

Number of bids 57 37 94 -21.3 

Minimum bid $0.00 $0.00 $0.00 0.0 

Maximum bid $500.00 $1,000.00 $1,000.00 50.0 

Mean bid $58.16 $88.54 $70.12 43.3 

Mean bid excluding max $50.27 $63.22 $60.12 21.5 

Number of $0 bids 30 16 46 -30.4 

Percent $0 bids 52.6 43.2 48.9 -19.2 

Rain barrels 

Number of bids 63 45 106 -17.0 

Average number of barrels per bid 1.9 1.7 1.8 -11.5 

Minimum bid (per barrel) $0.00 $0.00 $0.00 0.0 

Maximum bid (per barrel) $500.00 $250.00 $500.00 -50.0 

Mean bid (per barrel) $32.06 $44.30 $36.44 33.6 

Mean bid excluding max (per barrel) $24.51 $34.74 $32.03 31.9 

Number of $0 bids 38 20 58 -31.0 

Percent $0 bids 60.3 44.4 54.7 -29.0 

Because the sum of all bids did not exceed the amount of money allocated for subsidies 

and installations, we accepted nearly all of the bids. Two barrel bids were refused because the 

roofs were located outside the Shepherd Creek watershed, and one barrel bid was refused due to 

the high bid amount ($500 for 1 barrel) relative to other bidders and the cost of installation. All 

but one rain garden bid were initially accepted, again excluding the extremely high bid ($500) 

relative to other bids. Bidders were relatively evenly distributed throughout the treatment area 

(Figure 5.1.1). 

29
 
30
 

 

Table 5.1.2 Rain barrel rankings, 2007 

Barrel # Weighted Barrel # Weighted
 

Rank Bid ($) Barrels Score Accept? Rank Bid ($) Barrels Score Accept?
 

1 0 4 3 yes 33 0 1 13 yes 

2 100 4 4 yes 34 0 1 13 yes 

3 0 3 4 yes 35 0 1 13 yes 

4 0 4 4 yes 36 0 1 13 yes 

5 0 3 4 yes 37 0 1 13 yes 

6 0 3 4 yes 38 0 1 13 yes 

7 0 4 4 yes 39 0 1 13 yes 

8 50 3 5 yes 40 5 1 13 yes 

9 0 3 6 yes 41 27 1 13 yes 

10 0 2 6 yes 42 50 1 14 yes 

11 0 2 6 yes 43 50 1 14 yes 

12 0 2 6 yes 44 50 1 14 yes 

13 0 2 6 yes 45 100 1 15 yes 

14 0 4 6 yes 46 100 1 15 yes 

15 0 2 6 yes 47 0 1 17 yes 

16 0 2 6 yes 48 0 3 17 yes 

17 0 2 6 yes 49 0 1 17 yes 

18 0 2 6 yes 50 50 1 18 yes 

19 0 2 6 yes 51 250 4 19 yes 

20 0 2 6 yes 52 100 3 20 yes 

21 0 2 6 yes 53 0 2 25 yes 

22 50 2 7 yes 54 0 2 25 yes 

23 100 2 8 yes 55 0 2 25 yes 

24 100 2 8 yes 56 0 2 25 yes 

25 100 2 8 yes 57 100 2 30 yes 

26 100 2 8 yes 58 150 2 33 yes 

27 150 2 8 yes 59 0 1 50 yes 

28 0 2 8 yes 60 0 1 50 yes 

29 250 2 9 yes n/a 500 1 100 no 

30 500 2 13 yes n/a 100 1 n/a no 

31 0 1 13 yes n/a 50 1 n/a no 

32 0 1 13 yes 

Number of barrel bids accepted 60 

Total number of barrels 118 

Total cost (bid amount) $2,532 
Table 5.1.3 Rain garden rankings, 2007 

Garden Weighted Garden Weighted 

Rank Bid ($) Score Accept? Rank Bid ($) Score Accept? 

1 0 25 yes 30 0 36 yes 

2 0 25 yes 31 0 36 yes 

3 0 25 yes 32 0 36 yes 

4 5 25 yes 33 5 37 yes 

5 0 27 yes 34 50 38 yes 

6 25 28 yes 35 100 39 yes 

7 0 29 yes 36 100 39 yes 

8 0 29 yes 37 0 40 yes 

9 0 29 yes 38 0 40 yes 

10 0 29 yes 39 0 40 yes 

11 0 29 yes 40 0 40 yes 

12 50 30 yes 41 150 42 yes 

13 30 31 yes 42 50 45 yes 

14 0 31 yes 43 100 46 yes 

15 0 31 yes 44 250 46 yes 

16 0 31 yes 45 250 46 yes 

17 0 31 yes 46 250 46 yes 

18 0 31 yes 47 250 46 yes 

19 50 32 yes 48 100 50 yes 

20 100 33 yes 49 100 50 yes 

21 0 33 yes 50 50 50 yes 

22 0 33 yes 51 50 50 yes 

23 0 33 yes 52 0 50 yes 

24 0 33 yes 53 0 50 yes 

25 50 35 yes 54 100 56 yes 

26 50 35 yes 55 250 59 yes 

27 0 36 yes 56 250 59 yes 

28 0 36 yes n/a 500 90 no 

29 0 36 yes 

Number of garden bids accepted 56 

Total cost (bid amount) $2,815 

31
 

32
 


Figure 5.1.1 Location of rain barrel and rain garden bids in Phase 1, 2007 
5.2 Phase 2, Year 2008 

When the auction was repeated in spring 2008, there were 37 bids for rain gardens 

averaging $88.54, 43% higher than in 2007 (Table 5.1.1). The high bid was $1000 and the 

percent $0 bids dropped to 43.2%. For barrels, there were 45 bids for 76 barrels, averaging 

$44.30 per barrel, a 33% increase from 2007 bids. Thirteen homeowners who bid in 2007 also 

bid in 2008, reflecting their pleasure with the stormwater management practices received the 

previous year and/or their continued interest in this project. Two garden bids and one barrel bid 

were refused due to their high weighted score relative to other bidders, reflecting the high bid 

price and/or low environmental benefit of the stormwater management practice on that property 

(Table 5.2.1, 5.2.2). Again, bidders were located throughout the treatment portion of the 

watershed, although there were clusters of bidders that may reflect influences from neighbors 

(Figure 5.2.1). 

Table 5.2.1 Rain garden rankings, 2008 

Garden Weighted Garden Weighted 

Rank Bid ($) Score Accept? Rank Bid ($) Score Accept? 

1 0 19 yes 20 100 29 yes 

2 0 20 yes 21 0 30 yes 

3 0 20 yes 22 0 30 yes 

4 0 20 yes 23 0 30 yes 

5 50 20 yes 24 0 30 yes 

6 0 21 yes 25 250 30 yes 

7 50 22 yes 26 150 31 yes 

8 25 22 yes 27 100 32 yes 

9 0 23 yes 28 50 33 yes 

10 0 23 yes 29 250 33 yes 

11 0 23 yes 30 100 35 yes 

12 0 23 yes 31 150 38 yes 

13 100 23 yes 32 1 38 yes 

14 150 23 yes 33 50 41 yes 

15 50 25 yes 34 50 41 yes 

16 0 25 yes 35 100 44 yes 

17 0 25 yes n/a 250 71 no 

18 250 27 yes n/a 1000 80 no 

19 0 27 yes 

Number of garden bids accepted 35 

Total cost (bid amount) $2,026 

33
 

 

Table 5.2.2 Rain barrel rankings, 2008 

Barrel # Weighted Barrel # Weighted
 

Rank Bid ($) Barrels Score Accept? Rank Bid ($) Barrels Score Accept?
 

1 0 4 13 yes 24 50 1 17 yes 

2 0 4 13 yes 25 0 1 17 yes 

3 0 3 13 yes 26 0 1 17 yes 

4 0 3 13 yes 27 150 2 19 yes 

5 0 2 13 yes 28 50 2 19 yes 

6 0 2 13 yes 29 25 1 20 yes 

7 0 2 13 yes 30 100 1 21 yes 

8 0 2 13 yes 31 150 1 25 yes 

9 0 2 13 yes 32 150 1 25 yes 

10 0 2 13 yes 33 150 1 25 yes 

11 0 1 13 yes 34 0 2 25 yes 

12 0 1 13 yes 35 1 1 25 yes 

13 0 1 13 yes 36 200 1 29 yes 

14 0 1 13 yes 37 250 1 33 yes 

15 50 3 14 yes 38 250 1 33 yes 

16 50 2 15 yes 39 0 4 50 yes 

17 50 2 15 yes 40 0 2 50 yes 

18 50 2 15 yes 41 0 1 50 yes 

19 25 1 15 yes 42 1 1 51 yes 

20 50 1 17 yes 43 100 2 67 yes 

21 50 1 17 yes 44 100 2 67 yes 

22 50 1 17 yes n/a 300 2 100 no 

23 50 1 17 yes 

Number of barrel bids accepted 44 

Total number of barrels 74 

Total cost (bid amount) $2,152 

34
 

35
 

Figure 5.2.1 Location of rain barrel and rain garden bids in Phase 2, 2008 
CHAPTER 6 Stormwater Management Practice Installations 

6.1 Overview 

We installed rain barrels and rain gardens on those properties identified through the 

auction and granted subsequent permission by the homeowner. Soon after the bidding process 

we contacted the homeowners by mail and informed them they had been selected to participate, 

and scheduled a site visit. Upon visiting the site for the first time the homeowner was asked to 

sign an access agreement that gave consent to the “Mt. Airy Rain Catchers Project Team” to 

access their yard to install and maintain the rain barrels and rain gardens. The agreement 

specified the term of three years for the maintenance period. Both the property owner and a 

representative of the Project Team signed the agreement. Also in the first site visit the 

homeowner was handed a check in the amount of his or her bid. In 2007, we installed 50 

gardens and 100 barrels. The lower number of installations relative to accepted bids was due to 

not finding an acceptable location for the stormwater management practice on the property (e.g., 

preferred garden location above utility or lacked hydrologic benefit) and homeowners changing 

their mind upon consultation (e.g., did not want their gutter downspouts cut). In 2008, we 

installed 25 gardens and 50 barrels. An explanation of the installation guidelines and 

maintenance protocol for rain gardens and rain barrels follows. 

6.2 Rain gardens 

Installation protocol 

We worked with individual homeowners to determine location and design (i.e., shape) of 

the rain garden stormwater management practice. Rain gardens were approximately 150 sq. ft., 

although the final shape depended on the landscape and property features of each individual 

parcel. Using our index of ecological effectiveness we worked with individual homeowners to 

determine an optimal location and design for the rain garden, to maximize hydrological benefit 

while being suitable for the homeowner. If the homeowner indicated a location on the auction 

bid form, we flagged the location of the garden on the lawn and work with the homeowner to 

determine shape and design. If the homeowner indicated that they were flexible, we worked 

with the homeowner to determine the best location. We maintained the qualification that if we 

and the homeowner could not reach agreement about placement of the rain garden, either party 

could terminate the process of installing the rain garden. 

Rain gardens were installed between June and September. First, the sod was removed 

and a Dingo excavator was used to excavate a trench for installing a perforated underdrain pipe 

at the bottom of the trench. Most rain gardens were fitted with underdrains and outlets to allow 

for free-drainage of water to prevent the incidence of standing water for any extended period of 

time (Appendix A, Garden A). If landscape slope was insufficient to place an underdrain, the 

rain garden was instead made slightly larger (160 ± 10% sq. ft.) and 6” deeper (Appendix A, 

Garden B). In 2007, a majority of the rain gardens (34 of 50) were fitted with underdrains. Rain 

36
 

 

Number of Each Species Planted in Summer 2007 

- 40 80 120 160 200 

Species 

Great Blue Lobelia 

Cardinal Flower 

Fox Sedge 

Side Flowering Aster 

Mountain Mint 

Smooth Aster 

Pink Turtle Head 

Monkey Flower 

Smooth Beardtongue 

Crested Sedge 

Blue Flag Iris 

Lurid Sedge 

Lance-Fruited Sedge 

Marsh Milkweed 

Sweet Black-eyed Susan 

Bergamont 

Boneset 

Riddle's Goldenrod 

Showy Black-eyed Susan 

Foxglove Beard Tongue 

Monarda 

Spreading Oval Sedge 

Ohio Golden Rod 

Golden Alexander 

Franks Sedge 

Heath Aster 

221 

209 

209 

172 

155 

153 

147 

147 

139 

138 

137 

131 

129 

128 

127 

121 

106 

97 

91 

55 

49 

45 

40 

33 

30 

20 

240 

gardens were developed from native soils, but amended with coarse peat moss and sand and 

supplemented with organic fertilizer. In 2008, we amended the soils with peat moss and native 

compost (aged 3 years), since we felt that the proportion of sand was so low that they were 

unlikely to increase infiltration. Exposed soil on the berm was seeded and covered in straw held 

in place with netting. 

Due to drought conditions that persisted into September 2007, the gardens were planted 

in the fall that year so as to maximize plant survival. The planting area was covered with mulch 

to retain moisture and reduce weeds. Plants were primarily native species and cultivars that are 

adapted to periodic wet conditions expected in the rain gardens (Figure 6.1.1). Homeowners 

were given some choice in plants, and were asked to water the gardens periodically in the 1-2 

weeks following planting. In spring 2008 we conducted a plant inventory to determine plant 

success. In the second year, we used larger plant starts (8-10” pots) and planted species that 

were most successful in 2008. Additional species that were expected to be more resistant to deer 

browsing were also used. Figure 6.2.1 overviews the numbers of species planted while figure 

6.2.2 presents a typical raingarden in the study area. 

Figure 6.2.1 Species in plant communities planted in rain gardens, 2007. 

37
 

Figure 6.2.2 Typical rain garden installation 

Maintenance protocol 

We took on responsibility for maintenance of rain gardens over the research project 

period of three years from the date of construction. Regular maintenance was implemented into 

the project plan so as to sustain good performance and improve consistency in rain garden 

condition over the course of the research project. This includes assuring that the rain gardens are 

draining properly and plants remain in good conditions for the duration of the pilot study. 

Maintenance involves mulching and re-planting (as necessary) in the spring, weeding in the 

summer, and mulching and pruning in the fall. Homeowners also received a manual that 

explained our maintenance plan and asked homeowners not to add plants, fertilize, or otherwise 

disturb the garden. 

6.3 Rain barrels 

Protocol for installation 

The location of rain barrel(s) was determined by the amount of rooftop draining into a 

gutter downspout, the current drainage location of the gutter, and preferences of the homeowner. 

Ideally, rain barrels were located where a large portion of the roof runoff will be collected, and 

38
 

where runoff currently drains to stormwater conveyances. However, rain barrels connected to 

any downspout were deemed to be acceptable. 

We used green, 75-gallon rain barrels which were fitted with a spigot and hose located 

near the bottom of the barrel that allowed the barrels to be emptied in accordance with 

procedures set out in the owners manual. The barrels also have an internal overflow tube that is 

routed to another external opening at the bottom of the barrel. A screened cap was placed on top 

of the barrel to prevent debris from entering the barrel and prevent insects from breeding in the 

barrel. Roof gutter downspouts were cut and fitted with a flexible pipe to route the water to the 

barrel. Barrels were placed on cinder blocks and overflow tubes were routed into storm drains or 

landscape areas away from the house. Up to four barrels could be linked together on a single 

downspout to allow for increased detention capacity. Although the standard-issue rain barrel in 

the Mt. Airy project was 75 gallons, 23% of barrels issued to homeowners in 2007 were 55 

gallons due to shortfall in supplier inventory. See Appendix B for schematic representations of 

the rain barrels and their typical setting for installation. 

Maintenance protocol 

As a part of the licensing agreement, the homeowner agreed to take responsibility for 

maintenance of the rain barrels (e.g., emptying the barrel after a rainfall event). Homeowners 

were instructed on how to empty their barrels and given a manual that explained recommended 

maintenance. If a homeowner did not plan to use the water in their barrel, we recommended that 

the overflow and spigot hoses empty into the rain garden (if applicable) or other landscape 

feature that is designed to infiltrate water (e.g., a swale). Homeowners were advised to empty 

their barrels in the winter to prevent freezing and cracking of the barrels. 

39
 

CHAPTER 7 Rain Garden and Rain Barrel Monitoring 

7.1 Overview 

In cooperation with individual homeowners, we identified a subset of rain gardens to 

monitor for a period of three years from the date of construction. This monitoring will be 

conducted for a period of three years, and includes hydrology, soil, and water quality 

measurements. Five rain gardens are being monitored from the 2007 installations and an 

additional 5 gardens will be selected in 2008 to represent a range in soil types, landscape settings 

and drainage types (garden types A and B). Rain barrels are also monitored for water level and 

water quality. 

7.2 Hydrology and soils 

At each location, we are monitoring rain gardens for infiltration and water redistribution. 

We are measuring soil water content by averaging measurements taken every 30 seconds and 

recorded as a datum point every 10 minutes and at 10-cm intervals to 50-cm (Sentek EasyAG; 

Campbell Scientific; Logan UT), and this data is stored using an automatic logging system 

(Campbell CR800). Underdrains are evaluated qualitatively for evidence of flow (trickle flow 

after storms, build up of algae at outlet, erosion around outlet). Rain barrels are monitored 

continuously for water level using level loggers (In-Situ; Fort Collins CO) in order to determine 

patterns in the times and rates of water use by residents and number of overflow events. The 

level loggers are removed each winter (November-March) as rain barrels will be left open and 

freezing would damage the level logger pressure sensors. 

7.3 Water quality 

Monitoring for water quality will consist of episodic, storm-event based sampling of 

surface runoff to rain gardens, soil water sampling using suction lysimeters installed at a depth of 

12 to 18 inches in rain gardens, and underdrain flow sampling (where applicable; one rain garden 

site does not have an underdrain). Stainless steel suction lysimeters (SW-071 single chamber; 

Soil Measurement Systems, LLC) were installed in finished rain gardens during the months of 

April and May 2008 according to ASTM standard specifications (ASTM International 1992). 

Water quality sampling will also include periodic sampling of water collected in rain barrels at 

the chosen site locations. 

For rain garden and rain barrel performance monitoring, the results from sampling will be 

aggregated for data analysis purposes in order to determine: 1) the chemical composition of roof 

runoff as captured in rain barrels; 2) the chemical composition of lawn runoff to rain gardens on 

a seasonal basis; and 3) the treatment provided by rain gardens with respect to changes in 

nutrient concentrations (nitrogen and phosphorus), organic carbon, alkalinity, ions and metals. 

Lawn runoff samples also will be analyzed for suspended sediment concentration. Treatment 

will be determined by comparing soil water (lysimeter) and underdrain concentrations directly 

with lawn runoff and rain barrel samples using paired sample analysis of variance methods 

40
 

(Dietz and Clausen 2006, Davis 2007). Sampling frequency will consist of 2 storm events per 

season for a total of 8 events per year. The minimum acceptable number is 6 storm events, given 

the element of chance and practical problems associated with storm sampling. For purposes of 

replication, the goal will be to collect 3 samples of each type (lawn runoff, soil water from 

lysimeters, and underdrain discharge) at each site for each storm event. This yields a minimum 

of 18 samples of each type per site each year, where applicable. Only a single sample will be 

collected from the rain barrel at the end of the storm event, for a total of 6 to 8 samples per year. 

In the event that the replicate samples for a given storm exhibit temporal trends, they will be 

treated as independent samples. 

41
 

 

CHAPTER 8 Conclusions 

This study is a part of an ongoing effort to fully describe a realistic market-based 

mechanism to alleviate the water quality and ecological problems caused by the typically large 

volumes of excess stormwater runoff in urban and urbanizing areas. As impervious surface 

grows relative to natural landscapes the problem will increase, and municipal authorities will 

look for ways to deal with it that are both practical from a political standpoint and ecologically 

effective. We hypothesized that deployment of stormwater management practices in a watershed 

via market incentives would reduce stormwater runoff substantially, thus improving stream water 

quality and biotic integrity. To test this hypothesis, we examined four market mechanisms: 

command and control, cap and trade, fee and rebate, and auction. We modeled each policy using 

realistic cost functions, including the estimated opportunity cost of residential land dedicated to 

particular stormwater control practices, and we employed sound hydrologic models. In most 

cases we showed the incentive schemes to be economically efficient. When considering actual 

application of the market mechanism to a small Midwestern watershed, there were several legal 

and regulatory obstacles to the imposition of a cap on stormwater runoff (for a tradable credit 

mechanism) and the appropriately high stormwater fee (to allow for a fee and rebate policy). 

Thus, we opted for a wholly voluntary approach using a reverse auction. 

We are now testing our hypothesis that deployment of enough distributed, low-tech 

stormwater management practices in a watershed will reduce stormwater runoff sufficiently to 

effect positive hydrologic, water quality, and ecological change. We are doing this with actual 

installation of stormwater management practices in the Shepherd Creek watershed. We 

employed a before-after-control-impact experimental design, wherein we monitor streams for 

three years before installing the stormwater management practices in the treatment watersheds, 

and then continue monitoring for an additional three years. We employed a reverse auction to 

determine where to install the management practices in a cost effective way. The reverse, or 

procurement, auction is often used when there are many potential sellers of an item (in this case, 

homeowners selling the limited use of their property) and a single buyer (in this case, a 

government agency trying to buy as much stormwater retention capacity as economically 

feasible). To try to improve the subscription rate among homeowners and to test our hypotheses 

about iterative auctions, we conducted the auction and installation two years in a row. In 2007, 

we installed 50 rain gardens and 100 rain barrels at 68 properties for a total bid payout of $5,347. 

In 2008, we received acceptable bids for 35 rain gardens and 74 rain barrels on 49 properties, 

including 12 properties that received some stormwater management practice(s) in 2007. After 

two years of running the auction, we will have installed stormwater management practices on 

about 30% of the eligible properties in the treatment watershed. Future research includes the 

ongoing monitoring effort wherein we will quantify the hydrologic and ecological effectiveness 

of the installed storm water management practices. Overall, this methodology will provide 

defensible results about the efficiency, both economic and ecologic, of deploying rain gardens 

and rain barrels in a suburban watershed in order to reduce the effects of stormwater runoff. 

42
 

 

Publications related to this project 

Morrison M.A., W.D. Shuster and R.Webb. 2008. A streamlined monitoring framework for 

sustainable and low-impact development stormwater management practices. Proceedings of the 

11th International Conference on Urban Drainage, August 31-September 5, 2008, Edinburgh, 

Scotland, UK. 

Parikh, P., M. Taylor, T. Hoagland, H. Thurston, and W. Shuster. 2005. At the intersection of 

hydrology, economics, and law: application of market mechanisms and incentives to reduce 

stormwater runoff. Environmental Science and Policy 8:133-144. 

Prahalad, P. P., M. P. Clagett, and N. T. Hoagland. 2007. Beyond water quality: can the Clean 

Water Act be used to reduce the quantity of stormwater runoff? The Urban Lawyer 39:85-109. 

Roy, A.H. and W.D. Shuster. In press. Assessing impervious surface connectivity and 

applications for watershed management. Journal of the American Water Resources Association. 

Roy, A.H., H. Cabezas, M.P. Clagett, N.T. Hoagland, A.L. Mayer, M.A. Morrison, W.D. 

Shuster, J.J. Templeton, and H.W. Thurston, 2006. Retrofit stormwater management: navigating 

multidisciplinary hurdles at the watershed scale. Stormwater 7:16-29. 

Roy, A.H., A.L. Mayer, W.D. Shuster, H.W. Thurston, N.T. Hoagland, M.P. Clagett, P.K. 

Parikh, and M.A. Taylor. 2005. A multidisciplinary approach to stormwater management at the 

watershed scale. Proceedings of the 10th International Conference on Urban Drainage, August 

21-26, 2005, Copenhagen, Denmark. 

Roy, A.H., S.J. Wenger, T.D. Fletcher, C.J. Walsh, A.R. Ladson, W.D. Shuster, H.W. Thurston, 

and R.R. Brown. 2008. Impediments and solutions to sustainable, watershed-scale urban 

stormwater management: lessons from Australia and the United States. Environmental 

Management 42:344-359. 

Morrison M.A., W.D. Shuster and R.Webb. In press. Front-loading urban stormwater 

management for success – a perspective incorporating studies of retrofit low-impact 

development. Cities and the Environment. 

Shuster, W.D., J. Bonta, H. Thurston, E. Warnemuende, and D.R. Smith. 2005. Impacts of 

impervious surface on watershed hydrology: A review. Urban Water Journal 2:263-275. 

Shuster, W.D., R. Gehring, and J. Gerkin. 2007. Prospects for enhanced groundwater recharge 

via infiltration of urban storm water runoff: A case study. Journal of Soil Water and 

Conservation 62(3):129-137. 

43
 

Shuster, W.D., A.H. Roy, H.W. Thurston, M. Morrison, M. Taylor, and M. Clagett. 2008. 

Implementation of retrofit best management practices in a suburban watershed (Cincinnati, OH) 

via economic incentives. Proceedings of the 11th International Conference on Urban Drainage, 

August 31-September 5, 2008, Edinburgh, Scotland, UK. 

Shuster, W.D., Thurston, H.W. and Zhang, Y. 2006. Simulated rain Garden Effectiveness and 

performance in Response to synthetic and Natural Rainfall Patterns. Proceedings of the 7th 

International Conference on Urban Drainage Modelling and the 4th International Conference on 

Water Sensitive Urban Design, April 2-7 2006, Melbourne, Australia. 

Thurston, H.W. 2006. Opportunity costs of residential best management practices for 

stormwater runoff control. Journal of Water Resource Planning and Management 132:89-96. 

Thurston, H.W., H.C. Goddard, D. Szlag, and B. Lemberg. 2002. Trading stormwater abatement 

credits in Cincinnati’s Shepherd Creek: A proposal to spread responsibility for stormwater 

control across a watershed cost-effectively and equitably. Stormwater 3(5):50-59. 

Thurston, H.W., H.C. Goddard, D. Szlag, and B. Lemberg. 2003. Controlling stormwater runoff 

with tradable allowances for impervious surfaces. Journal of Water Resources Planning and 

Management 129:409-418. 

Thurston, H.W., W.D. Shuster, M.A. Taylor and S. Stewart. 2006. Evaluation of Economic 

Incentives for Decentralized Stormwater Runoff Management: The Shepherd Creek Watershed 

Pilot Project. Proceedings of the 7thInternational Conference on Urban Drainage Modelling and 

the 4th International Conference on Water Sensitive Urban Design, April 2-7 2006, Melbourne, 

Australia. 

Thurston, H.W., M.A. Taylor, A.H. Roy, M. Morrison, W.D. Shuster, J. Templeton, M. Clagett, 

and H. Cabezas. 2008. Appling a reverse auction to reduce stormwater runoff. Ambio 37(4):326­

327. 

44
 

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4696 – 92 (Reapproved 2000) ASTM International, West Conshohocken, PA. 

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Baumol, W. J. and Oates, W. E. 1988. The Theory of Environmental Policy, Cambridge 

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Association (JAWRA) 33:1077-1090. 

Brabec, E., S. Schulte, and P.L. Richards. 2002. Impervious surfaces and water quality: a review 

of current literature and its implications for watershed planning. Journal of Planning Literature 

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Davis, A.P. 2007. Field performance of bioretention: water quality. Environmental Engineering 

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Dietz, M.E. and J.C. Clausen. 2006. Saturation to improve pollutant retention in a rain garden. 

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Coleman, J.C., II 2000. Cost Minimization Analysis as a Foundation for a Marketable Credit 

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CSIRO. 2005. Catchment Care – Developing an Auction Process for Biodiversity and 

Water Quality Gains 

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Environmental Protection Agency, Office of Research and Development, Washington, DC. 

Godwin, K.S., S.D. Hafner, M.F. Buff. 2003. Long-term trends in sodium and chloride in the 

Mohawk River, New York: the effect of fifty years of road-salt application. Environmental 

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illustrated guide to field technique. United States Department of Agriculture, Forest Service. 

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drainage infrastructure on the concentrations and loads of pollutants in small streams. 

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Maryland, pp. 157-177. 

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Systematics 32:333-365. 

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of stream water across an urban-rural gradient in western Georgia. Urban Ecosystems 8:107-124. 

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Reading, Massachusetts. 

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Environmental Disturbances. Ecological Applications 4:4-15. 

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imperviousness or improve drainage design? Marine and Freshwater Research 55:317-326. 

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watershed manipulation. Journal of the North American Benthological Society 24(3):690- 705. 

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Walsh, C.J., A.H. Roy, J.W. Feminella, P.D. Cottingham, P.M. Groffman, and R.P. Morgan, II. 

2005b. The urban stream syndrome: current knowledge and the search for a cure. Journal of the 

North American Benthological Society 24(3):706-723. 

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and fish across multiple spatial scales. Environmental Management 28:255-266. 

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occurrence in response to impervious cover, historic land use, and hydrogeomorphic factors. 

Canadian Journal of Fisheries and Aquatic Sciences 65:1250-1264. 

48
 

APPENDIX A: Rain Garden Schematics 

49
 

50
 

51
 

52
 

53
 

APPENDIX B: Rain Barrel Schematic 

54
 

APPENDIX C: Quality Management Program 

1.0 Purpose 

The intent of this appendix is to better illustrate the sampling processes for hydrologic, 

ecological, and water quality monitoring efforts, and describe important changes that have been 

implemented since the project’s inception. This document will be updated periodically to 

document, amend, and otherwise record changes and progress in this monitoring effort. 

2.0 Problem definition/Background 

Successful ecosystem management of watersheds requires the integration of the ecological, 

economic, and social influences that collectively determine the sustainability of human 

communities. Additional impervious surface as a consequence of urbanization has altered the 

partitioning of stormwater into runoff, infiltration, interflow, stream flow, and groundwater 

recharge. These urbanized conditions increase the risk of downstream flooding, stream channel 

degradation, and damage to both aquatic and terrestrial ecosystems. 

Although off-site detention and retention are used to mitigate the hydrologic impacts of 

urbanization, the large areas needed for these best management practices (BMPs) are considered 

by many to be impractical. BMPs based solely on economic decisions typically lead to 

inadequate BMP capacity; while BMPs may improve the stormwater retention and water quality 

on the site in which they are located, there are no data to suggest that BMPs effectively improve 

the ecological integrity of either the streams directly downstream, nor the integrity of the overall 

watershed. 

An alternate approach to stormwater runoff management addresses runoff production at smaller 

scales, and involves reduction of impervious surface and increased temporary storage of runoff at 

the parcel level, or on-lot measures. The idea of limiting excess runoff at the parcel level is 

relatively new, and capitalizes on converting impervious surfaces to at least partially pervious 

surface, as well as capturing modest runoff volumes in economical parcel-level facilities. The 

implementation of this approach to storm water management has not been tested, nor has a path 

to implementation been outlined. There is a critical need to determine whether the type and 

storage capacity of typical on-lot BMPs, as chosen using economic constraints, are adequate to 

restore or protect ecosystems. 

3.0 Project organization 

The Shepherd Creek Monitoring Project is primarily supported by the Office of Research and 

Development, National Risk Management Laboratory, Sustainable Technology Division, 

Sustainable Environments Branch with Dr. William Shuster serving as the primary point person 

for the monitoring. Ongoing monitoring includes hydrology, water quality, and ecology, with Dr. 

William Shuster, Dr. Matthew Morrison, and Dr. Allison Roy as the primary leads associated 

with each portion, respectively. Other divisions within NRMRL, contractors, and inter-agency 

agreements (IAG) with other federal organizations also support this project. The impervious 

survey was a one-time survey to further characterize directly connected impervious areas in the 

Shepherd Creek watershed and assist in predicting stream responses to BMPs. 

55
 
4.0 Project description 

4.1 Overview 

The purpose of this study is to investigate the potential for stakeholder participation in an on-lot 

stormwater management program. Field monitoring is used to determine whether such a program 

is effective insofar as the improvement of hydrologic (including sediment dynamics), ecologic, 

and water quality conditions of downstream subcatchments. In this project, the effectiveness of 

BMPs under realistic field conditions will be measured. 

4.3 Experimental design 

This study has a before/after and control/impact (BACI) experimental design. This approach is 

popular in watershed work, as it attempts to control for the high levels of variance that are 

common to experiments conducted at large-scales. Due to this experimental approach, we will be 

unable to avoid a certain level of pseudoreplication, as errors will not be independent between 

the before and after treatment time periods (since consequences that lead to fluctuations 

accumulate over time). We will be collecting at 6 different sites (3 of which should be relatively 

independent as they are disconnected hydrologically from each other) for at least one year before 

and two years after BMP implementation (Table 4.1). Two of the sampling sites will not have 

BMPs installed within their respective sub-watersheds, and therefore serve as controls. Because 

this project will not be replicated in other watersheds, interpretation of our results will be 

somewhat restricted to the results and conclusions drawn from the Shepherd Creek and similar 

environmental settings. 

Table 4.1. Sample sites, type (control/treatment), and initiation of monitoring by category. 

Site Type Hydrology Water Quality Ecology 

REF1 Control Fall 2004 Baseflow, Spring 2004 Spring 2003 

PWR2 Treatment Fall 2004 Baseflow, Spring 2004 Spring 2003 

Stormflow, Summer 2005 

DRI3 Treatment Fall 2004 Baseflow, Spring 2004 Spring 2003 

Stormflow, Summer 2005 

ROA4 Treatment Fall 2004 Baseflow, Spring 2004 Spring 2003 

Stormflow, Summer 2005 

CON5 Treatment Fall 2004 Baseflow, Spring 2004 Spring 2003 

Stormflow, Summer 2005 

URB6 Control Summer 2005 Baseflow, Spring 2005 Spring 2005 

Stormflow, Summer 2005 

REF7 Control (to Fall 2004 Baseflow, Summer 2005 Summer 2005 

replace REF1) Stormflow, Summer 2005 

N1 Treatment Spring 2006 N/A N/A 

N2 Treatment Spring 2006 N/A N/A 

N3 Treatment Spring 2006 N/A N/A 

56
 

 

 

 

 

 

4.4 Sampling procedure 

Details regarding the sampling approach for hydrology, water quality, and ecology can be found 

in the respective supporting QAPPs and SOPs. Briefly, hydrology is sampled continuously (5 

min. intervals) for stage and discharge, and one rain gauge (at ROA4) services the entire 

watershed. Channel cross sections, bed sediment, and bank soils will be assessed at one time 

before and 3 years after BMP implementation. Water quality is sampled monthly during 

baseflow conditions (grab sample), and opportunistically during stormflow conditions 

(automated ISCO sampler). Periphyton and macroinvertebrates are sampled 5 times per year 

(every 4-6 weeks from April to October) during baseflow conditions. Macroinvertebrates are 

also sampled seasonally using a quantitative, bucket sampler. During all ecological sampling 

periods, physical characteristics, water quality parameters (YSI), and habitat characteristics 

(visual assessment) are measured. A summary of the sampling is in Table 4.2. 

Table 4.2. Summary of sampling approach, type, and sampling resolution. 

Instrument/Sample Data collected Data resolution Output/Indices 

Hydrology 

Stream stage and discharge 

via control structures (i.e., 

weir or culvert) 

Stream stage and 

discharge 

5 minute Rating curve, stream 

discharge record, event 

hydrographs 

Tipping-bucket raingauge 

located at ROA site 

Rainfall intensity, 

cumulative amount 

Continuous logging, 

truncated to 5minute 

intervals 

Rainfall intensity, 

duration, and amount 

Geomorphic assessment Cross-section surveys, 

bankfull and water 

surface longitudinal 

survey, bank soil 

collection, Wolman 

pebble count 

Baseline survey done Fall 

2004, repeat post-BMP 

implementation in 2009 or 

2010 

D50 (pebble count), 

particle size 

distribution 

Water Quality 

YSI 6600 data sonde Temperature, ORP, 

conductivity, pH, 

dissolved oxygen, 

turbidity 

Monthly baseflow 

sampling, opportunistic 

stormflow sampling, and 

with ecology sampling 

Water quality 

parameters 

Grab (baseflow) and 

automated ISCO (stormflow) 

water quality samples 

Nutrients, anions, metals Monthly baseflow 

sampling, opportunistic 

stormflow sampling 

Chemical 

concentrations 

Sediment suspended and bed-load 

sediment 

Monthly baseflow 

sampling, opportunistic 

stormflow sampling 

Sediment flux, weight 

and particle size 

distribution 

Ecology 

Periphyton (2 50ml jars) 1 jar: taxonomic ID 

1 jar: biomass 

5 times per year (every 4-6 

weeks April-October) 

Multimetric indices, % 

orders, ordination 

57
 

 

Periphyton (1 glass fiber 

filter) 

Chlorophyll α 5 times per year (every 4-6 

weeks April-October) 

Multimetric indices, % 

orders, ordination 

Benthic macroinvertebrates (1 

L jar) 

Taxonomic ID, 

abundance and richness 

5 times per year (every 4-6 

weeks April-October); 

seasonal bucket samples 

Multimetric indices, 

tolerance indices, 

ordination 

Physical characterization and 

habitat visual assessment 

Ranking of physical 

attributes of sampling 

sites 

5 times per year (every 4-6 

weeks April-October); 

seasonally with 

macroinvertebrates 

Qualitative Habitat 

Evaluation Index 

(QHEI) 

5.0 Project changes and additions 

Since the inception of the Shepherd Creek monitoring project in 2003, various aspects of the 

monitoring have changed. Below is a chronological listing of the major changes and additions to 

the project, including the creation of supporting documents: 

1.	 September 2005. The baseline monitoring period was extended until spring 2007 
 

(originally spring 2006), after which BMPs will be implemented. 
 

2.	 January 2005. An additional control site (URB6) was established; the weir for 
 

hydrological monitoring was installed in May 2005. 
 

3.	 May 2005. Water quality assessment expanded to include monthly baseflow and 

opportunistic stormwater samplings (previously only during ecological sampling), and 

additional analytes (e.g., metals). 

4.	 May 2005. An additional reach downstream of REF1 site was established (called REF7) 

due to dry upstream conditions at REF1. Because REF7 is the location of hydrologic 

monitoring, all stormflow water quality sampling will take place at REF7. 

5.	 June 2005. A survey of directly-connected impervious areas (DCIA) in the Shepherd 

Creek watershed was initiated in conjunction with USEPA summer interns. 

6.	 January 2006. A Health and Safety Plan for field and laboratory was created for work 

conducted under this QMP. 

7.	 April 2006. Implementation of three additional hydrologic monitoring sites at 

neighborhood stormwater outfalls to increase the spatial resolution of runoff and drainage 

monitoring. 

8.	 November 2007. Install equipment in 5 rain gardens to monitor soil water content and soil 

water quality (suction lysimetry). 

6.0 Quality objectives and criteria for measurement data 

The investigators followed appropriate, established protocols so that data conforms to commonly 

accepted and reasonable standards of accuracy and resolution. The standards are detailed in the 

family of supporting QAPP and SOPs related to this project. 

58
 

 

PRESORTED STANDARD 

POSTAGE & FEES PAID 

EPA

PERMIT No. G-35 

Office of Research and Development 

National Risk Management 

Research Laboratory 

Cincinnati, OH 45268 

Official Business 

Penalty for Private Use 

$300

EPA/600/R-08-129

October 2008 

www.epa.gov