BMP Construction and Maintenance Costs - Minnesota Pollution

BMP Construction and Maintenance Costs - Minnesota Pollution

Best Management Practices Construction Costs, Maintenance Costs, and Land Requirements Prepared for Minnesota Pollution Control Agency June 2011 p-g...

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Best Management Practices Construction Costs, Maintenance Costs, and Land Requirements Prepared for Minnesota Pollution Control Agency

June 2011

p-gen3-13x

Best Management Practices Construction Costs, Maintenance Costs, and Land Requirements Prepared for Minnesota Pollution Control Agency

June 2011

4700 West 77th Street Minneapolis, MN 55435-4803 Phone: (952) 832-2600 Fax: (952) 832-2601

Best Management Practices Construction Costs, Maintenance Costs, and Land Requirements June 2011

Table of Contents 1.0 Introduction ............................................................................................................................................ 1 1.1

Introduction and Project Purpose ................................................................................................ 1

2.0 BMPs Evaluated..................................................................................................................................... 2 2.1

Bioretention Basin/Rainwater Garden without Drain Tile.......................................................... 2

2.2

Biofiltration Basin/Rainwater Garden with Drain Tile ............................................................... 2

2.3

Wet Detention Basin ................................................................................................................... 2

2.4 2.5

Constructed Wetlands ................................................................................................................. 3 Infiltration Trench/Basin............................................................................................................. 3

2.6

Underground Infiltration ............................................................................................................. 3

2.7

Pervious Pavement ...................................................................................................................... 4

2.8 Grass Swale/Channel .................................................................................................................. 4 3.0 BMP Cost Factors & Methodology ....................................................................................................... 6 3.1

Construction Costs ...................................................................................................................... 6 3.1.1 Data Uncertainty ............................................................................................................ 6 3.1.2

3.2

Approach to Normalizing and Reporting Data .............................................................. 6

3.1.2.1 Unit Construction Costs .................................................................................. 6 3.1.2.2 Regional Adjustment Factors .......................................................................... 7 3.1.2.3 Price Adjustment Factors ................................................................................ 7 3.1.2.4 Data Standard Deviation ................................................................................. 7 3.1.3 Research Results Discussion.......................................................................................... 8 Annual Maintenance Costs ....................................................................................................... 10 3.2.1

Data Limitations and Uncertainty ................................................................................ 11

3.2.2

Approach to Normalizing and Reporting Data ............................................................ 11

4.0 Estimator Models ................................................................................................................................. 12 4.1

4.2.

Estimator Models ...................................................................................................................... 12 4.1.1 4.1.2

1999 USEPA Study...................................................................................................... 12 2003 UNC Study .......................................................................................................... 12

4.1.3

2005 MnDOT Report ................................................................................................... 12

Comparison of Collected Data with Estimator Models ............................................................ 14 4.2.1

Construction Cost Comparison .................................................................................... 14

4.2.2

Annual Maintenance Cost Comparison ....................................................................... 16

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4.2.3

Land Area Comparison ................................................................................................ 16

5.0 Land Area Requirements ..................................................................................................................... 18 5.1

Introduction and Research Approach........................................................................................ 18

5.2

Land Area Requirements for Structural BMPs ......................................................................... 18

5.3

5.2.1

O&M Responsibility Policy ......................................................................................... 18

5.2.2

Area Requirements ...................................................................................................... 19

Vegetated Buffer Requirements ................................................................................................ 20

6.0 MIDS Calculator .................................................................................................................................. 21 References ................................................................................................................................................... 22

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List of Tables Table 1 Table 2 Table 3 Table 4 Table 5 Table 6 Table 7 Table 8

Summary of Construction Cost Data Collected ................................................................9 Summary of Annual Maintenance Cost Data Collected. ................................................. 10 Summary of BMP Construction Costs from Estimator Models ....................................... 13 Summary of Annual BMP Maintenance Costs from Estimator Models ........................... 13 Summary of BMP Land Areas from Estimator Models .................................................. 14 Comparison of Construction Cost Estimator Models to Study Data ................................ 15 Comparison of Maintenance Cost Estimator Models to Study Data ................................ 16 Comparison of BMP Land Cost Estimator Models to Study Data ................................... 17

List of Appendices Appendix A BMP Cost Survey Data Tables Appendix B Land Requirements (Easements) for Stormwater BMPs

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1.0 Introduction 1.1

Introduction and Project Purpose

In this MIDS task, Barr was asked to summarize a typical range of low-impact development stormwater management best management practices (BMPs) costs. Barr identified a range of typical construction and operating costs for eight 1 structural BMP categories that support lowimpact development. We used these costs and the expected longevity of the BMP to estimate life cycle costs for these stormwater BMPs. In order to develop a basis for estimating the life cycle costs of stormwater BMP implementation, readily available data from construction projects and other studies were examined. Barr project files and other public information were used to compile a list of project data that included cost and basic design information. Few data sets included maintenance or land costs. The data sources used vary considerably in where and when they occurred. A major element of this effort was to normalize the data for 2010 Minnesota costs. In addition to summarizing construction cost data, the data was compared to available cost models that have been developed by the U.S. Environmental Protection Agency (USEPA), the Minnesota Department of Transportation (MnDOT), and the University of North Carolina. This provided a method of benchmarking the data collected. Use of predictive models was also used for maintenance costs and land area requirements. Because of the paucity of data for maintenance costs and land area, these models provide the greatest source of information for developing life-cycle cost estimates. Land costs are not included in the life-cycle cost estimates. BMP land costs are dependent on parcel-specific land costs and land costs vary widely throughout the state and with zoning classification. Instead of including land costs with the BMP life-cycle cost estimates, Barr identified and summarized land requirements for the different structural BMP types. Land requirements depend not only on the size of the BMP, but also on the easement requirements of the permitting authority. Based on a review of the regulatory requirements and interviews with six Minnesota cities, Barr determined that the land area required for easements is a small component of the overall land area needed for each BMP type.

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The scope of work was for only six BMP categories. However, research sources included data on additional BMP types and this information was added into our database for this project. Best Management Practices Construction Costs, Maintenance Costs, and Land Requirements Barr Engineering Company

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2.0 BMPs Evaluated Construction cost data were collected and evaluated for eight structural Best management Practices (BMPs) categories. These types are described in this section. Each BMP is described using generally accepted definitions found in the literature. The BMPs on which data were collected are consistent with these definitions; however, there may be some variation on the size of the BMPs compared to the typical size ranges included in the definitions below. Water quality treatment volumes are also discussed for each BMP. These water quality treatment volumes were used to compare BMP costs to one another.

2.1

Bioretention Basin/Rainwater Garden without Drain Tile

A bioretention basin is a natural or constructed impoundment with permeable soils that captures, temporarily stores, and infiltrates the design volume of stormwater runoff within 48 hours (24 hours within a trout stream watershed). These facilities typically include vegetation. For the purposes of this study, the water quality treatment volume of a bioretention basin is considered to be the total holding capacity below the outlet or overflow elevation of the basin.

2.2

Biofiltration Basin/Rainwater Garden with Drain Tile

Biofiltration basins are nearly identical to bioretention basins. The only difference is the addition of a drain tile below the designed filtration media. Filtration basins are often used in areas of potential stormwater “hot-spots 2,” where groundwater recharge is undesirable, or areas with very low infiltration rates in the underlying soil. As with bioretention basins, the water quality treatment volume is considered the total holding capacity below the outlet or overflow elevation of the basin.

2.3

Wet Detention Basin

These facilities capture a volume of runoff and retain that volume until it is displaced in part or in total by the next runoff event. Wet detention basins maintain a significant permanent pool of water between runoff events. Wet detention basins that conform to National Urban Runoff Pollution (NURP) criteria have permanent pools with average depths of four to ten feet and volumes below the normal pond outlet that are greater than or equal to the runoff from a 2.5-inch 24-hour storm over the

2

See MID Memorandum: Identify Restrictions for MIDS Practices to Protect Groundwater and Prevent Sinkholes. Best Management Practices Construction Costs, Maintenance Costs, and Land Requirements Barr Engineering Company

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entire contributing drainage area. These basins utilize gravity settling as the major pollutant removal mechanism but nutrient and organic removal can be achieved through aquatic vegetation and microorganism uptake. For the purposes of this study, the water quality treatment volume of a wet detention basin is considered to be the total holding capacity below the permanent pool (dead storage). Wet detention basins are not considered stormwater volume control devices.

2.4

Constructed Wetlands

Constructed wetlands are similar to wet detention basins, except they are shallower and the bottom is planted with wetland vegetation. Constructed wetlands remove pollutants through contact time with the permanent pool of water and vegetation uptake. Constructed wetlands typically require large areas to allow for adequate storage volumes and long flow paths. The Minnesota Stormwater Manual recommends that a minimum of 35% of the total wetland surface area should have a depth of 6 inches or less and 10% to 20% of the surface area should be a deep pool (1.5 to 6 foot depth). For the purposes of this study, the water quality treatment volume of a constructed wetland is estimated as the surface area of the wetland multiplied by 18 inches. This estimate is needed to develop a water quality treatment volume for many of the projects samples.

2.5

Infiltration Trench/Basin

An infiltration trench is a shallow excavated trench, typically 3 to 12 feet deep, that is backfilled with a coarse stone aggregate, allowing for the temporary storage of runoff in the void space of the material. Discharge of this stored runoff occurs through infiltration into the surrounding naturally permeable soil. Trenches are commonly used for drainage areas less than five acres in size. An infiltration basin is a natural or constructed impoundment that captures, temporarily stores and infiltrates the design volume of water over several days. Infiltration basins are commonly used for drainage areas of 5 to 50 acres with land slopes that area less than 20 percent. Typical depths range from 2 to 12 feet, including bounce in the basin. For the purposes of this study, the water quality treatment volume of an infiltration basin or trench is considered the total holding capacity below any outlet or overflow.

2.6

Underground Infiltration

In underground infiltration, storage tanks are either incorporated directly into or before the storm sewer system. If the storage systems are completely enclosed, stormwater is released at a controlled rate to a sewer system or open water course, and no stormwater volume is lost. If the storage systems Best Management Practices Construction Costs, Maintenance Costs, and Land Requirements Barr Engineering Company P:\Mpls\23 MN\62\23621050 MIDS\WorkFiles\Work Plan 4\MaintenanceNeedsCostsEasements\Report\BMP Construction Cost Maintenance Cost and Land Requirements.docx

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are bottomless or perforated, they will allow infiltration and reduce stormwater volume leaving a site. For the purposes of this study, the water quality treatment volume of an underground infiltration system is estimated as its hold capacity before discharging to a sewer system or open water course.

2.7

Pervious Pavement

Pervious pavements can be subdivided into three general categories: 1) Porous Pavements – porous surfaces that infiltrate water across the entire surface (i.e., porous asphalt and pervious concrete pavements); 2) Permeable Pavers – impermeable modular blocks or grids separated by spaces or joints that water drains through (i.e., block pavers, plastic grids, etc.); 3) Reinforced Soil – soil reinforced with a system of modular cells added to the surface soil to increase the bearing capacity of soil, maintain soil structure, and prevent compaction. Modular cells are typically concrete or plastic and are filled with either topsoil to support turf grass or gravel. They are most commonly used for seasonal (summer) parking and fire lanes. There are many different types of modular systems available from different manufacturers. For the purposes of this study, the water quality treatment volume of a pervious pavement is the void space of the engineered base below the paving surface. This base is typically uniformly sized crushed rock.

2.8

Grass Swale/Channel

Grass channels are designed primarily to convey stormwater runoff. Typical specifications include a runoff velocity target of 1 foot per second small storms and the ability to handle the peak discharge from a 2-year, 10-year, or 100-year design storm. Estimating a treatment volume for grass channels is problematic because most channels are built to meet flow rate needs and available data does not include sufficient detail to estimate treatment volume. Grass swales are typically considered a water quality BMP, not a volume control BMP. The velocity in the swale must be low enough to allow sediment to drop out. There can be some infiltration along the length of the swale but this is highly dependent on surface soils and the duration of flow in the swale, which is generally too short for appreciable infiltration.

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Significant stormwater volume reductions can be created by placing check dams across the swale. A grass swale with check dams functions similar to a series of bioretention basins and should be viewed accordingly.

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3.0 BMP Cost Factors & Methodology 3.1

Construction Costs

Actual construction costs were used to calculate construction cost per water quality volume, as defined in Section 2 for each BMP. Construction cost information from an assortment of locations and owners was used.

3.1.1

Data Uncertainty

The construction data collected varies considerably in its detail and comprehensiveness. Costs for design, geotechnical testing, legal fees, and other unexpected or additional costs are not usually included in the reports and are not included in the construction costs listed in this memo. Uncertainty in these construction cost estimates can come from this variable project related data and from factors such as complexity of design details, variation in local regulatory requirements, unreported soil conditions, and other site specifics. For example, variable design parameters that could affect the total construction cost include pond side slopes, depth and free board on ponds, total wet pond volume, outlet structure configuration, the need for retaining walls, and other site specific variables. These details are generally not reported in the data collected. Another source of uncertainly is a relatively few data sources for some of the BMP categories. For example, biofiltration devices are lacking in readily available project specific data and are only represented by two data sources. Any use of the data set or derivations of it should consider the high level of uncertainty involved.

3.1.2

Approach to Normalizing and Reporting Data

The considerable spread in time, space, and size of the projects reporting data, leads to the need for some normalization of the data. The data were adjusted to account for these factors as described below. 3.1.2.1

Unit Construction Costs

With an eye toward the potential of producing a calculator for developing cost estimates for BMPs, the various data points have been “normalized” for project size and scope by dividing the cost by the water quality treatment volume. This results in a construction cost per cubic foot of water quality treatment. This unit cost accounts for the size of the project and might provide a convenient basis for cost estimation. For example, a developer could develop an estimate of water volume to be Best Management Practices Construction Costs, Maintenance Costs, and Land Requirements Barr Engineering Company P:\Mpls\23 MN\62\23621050 MIDS\WorkFiles\Work Plan 4\MaintenanceNeedsCostsEasements\Report\BMP Construction Cost Maintenance Cost and Land Requirements.docx

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treated based on one of many watershed runoff models and local regulations, and then apply it directly to these normalized estimates for individual BMPs. 3.1.2.2

Regional Adjustment Factors

The data for this study was normalized by region using regional cost factors reported in Weiss, P.T., J. S. Gulliver and A. J. Erickson, (2005), U.S. Environmental Protection Agency (1999), and first published by the American Public Works Association in 1992. All of the data were normalized to the region that includes Minnesota. All of the data statistics then are in “Minnesota” dollars. 3.1.2.3

Price Adjustment Factors

The construction costs reported have also been translated to 2010 dollars. This was done using the Consumer Price Index (CPI) history as reported by the U.S. Bureau of Labor Statistics. The CPI is a wide spectrum index that closely parallels the various construction price indices available. 3.1.2.4

Data Standard Deviation

The uncertainty and the small sample size of some of these data categories make statistical analyses suspect. The standard deviation for each data sample is reported here to indicate the level of variation within the individual data sets. For data populations with a normal distribution, one standard deviation above and below the average would encompass about 68% of the data. The figure below shows a plot of a normal distribution (or bell curve). Each colored band has a width of one standard deviation.

The construction cost data collected for this study are probably not normally distributed. Weiss et al. suggested that a log normal distribution would better fit construction cost data. In that case, confidence interval calculations are not straight forward.

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3.1.3

Research Results Discussion

Data for 69 projects were normalized and statistics calculated as described in Section 3.1.2 and shown in Table 1 below. The diverse data is regionalized to the Midwestern US and converted to 2010 dollars. The averages are shown as cost per water quality volume, where that information was available. Water quality volume refers here to the raw volume of water that is treated by the BMP in terms of a straight forward and regularly reported characteristic. As discussed in Section 2, the total volume of the BMP below the outlet was used for the water quality volume of bioretention basins, biofiltration basins, infiltration trenches/basins and underground infiltration structures. For wet detention basins, the dead storage volume was used. For constructed wetlands, the surface area of the wetland multiplied by 18 inches was used due to the lack of detail regarding the wetland projects sampled. To calculate water quality volume for pervious pavement, the void space of the base aggregate below the pavement was used. In the case of grass swales, the data reviewed did not report characteristics amenable to a treated volume estimate and assumptions regarding the watersheds and design would need to be made to estimate a treatment volume. This data was not available. Due to both a lack of good background information and highly variable information, a cost analysis of grass swales is not included in the report. In some cases an economy of scale is clearly shown in the data. Wet detention basins exhibited the strongest apparent economy of scale as reported in Appendix A: BMP Cost Survey Data Tables. The cost difference between very small basins and large basins is several orders of magnitude. This is a significant difference and is hard to explain. Detailed project data related to the three small basin projects was not available but based on the project name, two of the projects appear to be vaults. Another explanation is that these could be decorative ponds serving more as a landscape feature than a stormwater function. For these reasons, the small wet detention basins were separated from the large basins in Table 1. Underground infiltration BMPs also exhibited an apparent economy of scale but not as clearly as wet detention basins and with some individual project exceptions. There was no apparent economy of scale in the data collected for bioretention basins.

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Table 1

Summary of Construction Cost Data Collected

Cost per

Average cost ($)

Sample standard deviation

11

Water quality 3 volume/ft

15

9

Biofiltration Basins

2

Water quality 3 volume/ft

58

61

Large Wet Detention Basins treating more than 100,000 3 ft

5

Water quality 3 volume/ft

2

2

Small Detention Basins 3 treating less than 10,000 ft

3

Water quality 3 volume/ft

145

42

Constructed Wetlands

4

Water quality 3 volume/ft

1

1.5

Infiltration Trenches

8

Water quality 3 volume/ft

11

30

Infiltration Basins

6

Water quality 3 volume/ft

21

15

Underground Infiltration

8

Water quality 3 volume/ft

213

372

Pervious Pavement

7

Water quality 3 volume/ft

16

8

Number of BMPs

Bioretention Basins

BMP name

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3.2

Annual Maintenance Costs

Of the 69 BMPs presented in Table 1, 25 included annual maintenance costs. The data are regionalized to the Midwestern U.S., converted to 2010 dollars, and summarized below. Table 2

Summary of Annual Maintenance Cost Data Collected.

Cost per

Average annual maintenance cost ($)

Sample standard deviation

8

Water quality 3 volume/ft

1.25

1.18

Biofiltration Basins

0

Water quality 3 volume/ft

No data

-

Large Wet Detention Basins treating more than 3 100,000 ft

4

Water quality 3 volume/ft

0.07

0.10

Small Wet Detention Basins treating less than 3 10,000 ft

0

Water quality 3 volume/ft

No data

-

Constructed Wetlands

0

Water quality 3 volume/ft

No data

-

Infiltration Trenches

8

Water quality 3 volume/ft

0.39

0.11

Infiltration Basins

6

Water quality 3 volume/ft

No data

Underground Infiltration

4

Water quality 3 volume/ft

1.26

2.16

Pervious Pavement

0

Water quality 3 volume/ft

No data

-

Number of BMPs

Bioretention Basins

BMP name

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3.2.1

Data Limitations and Uncertainty

The data collected varies considerably in its detail and comprehensiveness. This leads to undocumented variability in the data from factors such as design detail, variation in local regulatory requirements, unreported soil conditions, and other site specifics. For example, variable maintenance parameters that could affect maintenance costs include soil conditions, land use within the tributary watershed, plant selection, precipitation patterns, and other site specific variables. With few exceptions, these details are generally not reported in the data available. As a whole, the maintenance cost data collected lists the maintenance costs as a lump sum without detailed breakdown or discussion. Another source of uncertainly is a relative few data sources for some of the BMP categories. For example, constructed wetlands are lacking in readily available project-specific data and are represented by four data sources. Any use of the data set or derivations of it should consider the high level of uncertainty involved.

3.2.2

Approach to Normalizing and Reporting Data

The data for annual maintenance cost was normalized for region and for the date it was reported. Regional bias was adjusted using regional cost factors reported in Weiss, P.T., J. S. Gulliver and A. J. Erickson, (2005), U.S. Environmental Protection Agency (1999), and first published by the American Public Works Association in 1992. All of the data were normalized to the region that includes Minnesota. The maintenance costs reported have also been translated to 2010 dollars. This was done using the Consumer Price Index (CPI) history as reported by the U.S. Bureau of Labor Statistics. The CPI is a wide spectrum index that closely parallels the various construction price indices available.

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4.0 Estimator Models 4.1

Estimator Models

4.1.1

1999 USEPA Study

The U.S. Environmental Protection Agency’s (USEPA) Engineering and Analysis Division conducted a study on stormwater best management practices during 1997 and 1998. The report: Preliminary Data Summary of Urban Storm Water Best Management Practices, (EPA-821-R-99-012) was published in August 1999. In addition to summarizing existing information and data regarding the effectiveness of BMPs to control and reduce pollutants in urban stormwater, the report provides a synopsis of the expected costs and environmental benefits of BMPs and identifies information gaps as well. It includes simple methods for estimating costs for construction and maintenance of stormwater BMPs. This study has often been referred to and built upon in subsequent studies, including those surveyed here. The USEPA study cost estimation methods were examined for comparison with the results here.

4.1.2

2003 UNC Study

Ada Wossink and Bill Hunt of the University of North Carolina (UNC) examined the costs of BMPs including both installation (construction and land) and annual operating costs (inspection and maintenance) in The Economics of Structural Stormwater BMPs in North Carolina (UNC-WRRI2003-344) in 2003. For the UNC study, construction costs and annual operating costs are statistically analyzed for effects of scale by means of BMP specific nonlinear equations relating the costs to watershed size. Annual costs were related to the area treated and to the removal effectiveness of the specific BMP for an economic evaluation. The cost relationships were given in terms of watershed area, which then requires assumptions regarding runoff characteristics to arrive at a treatment volume. For this reason, a comparison with the results of the UNC study was not done for construction or maintenance cost data collected for this study. However, the UNC study also provides land area requirement estimates that are compared with the data collected for this study.

4.1.3

2005 MnDOT Report

In 2005, the Minnesota Department of Transportation (MnDOT) published work by Peter T. Weiss and John S. Gulliver titled The Cost and Effectiveness of Stormwater Management Practices. In examining the cost effectiveness of various BMPs, collected data were used to derive relationships between cost and water quality volume to estimate construction and maintenance costs. This study’s Best Management Practices Construction Costs, Maintenance Costs, and Land Requirements Barr Engineering Company

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cost relationships are examined for comparison with the results here, and suggested as a surrogate for missing data on maintenance found in readily available data. Tables 3, 4 and 5 compare the results for the estimator models described. These tables add two BMPs not found in Tables 1 and 2; sand filters and dry ponds. They also do not differentiate between large and small wet detention basins, and biofiltration, underground infiltration, and pervious pavement BMPs are not in Tables 3 through 5. Table 3

Summary of BMP Construction Costs from Estimator Models USEPA (1999)

Weiss et al. (2005)

Construction cost converted to 2010 $

Construction cost converted to 2010 $

3

3

Wossink et al., (2003) C = Cost($)

per ft of treated water volume

per ft of treated water volume

Constructed Wetlands

0.80-1.70

0.20-2.40

C = 3,852X

Wet Detention Basins

0.70-1.40

0.30-3.70

C = 13,909X

Infiltration Trenches

5.40

6.50-11.50

Bioretention Basins

7.20

10.10-11.30

Infiltration Basins

1.80

NR

NR

Dry Ponds

0.70-1.40

0.30-5.00

NR

Sand Filters

4.10-8.20

3.40-16.80

BMP

X = size of watershed(acre) 0.484

0.672

NR C = 10,162X

C = 47,888X

1.088

0.882

NR = Not reported

Table 4

Summary of Annual BMP Maintenance Costs from Estimator Models Wossink et al., (2003) C = Cost($) X = size of watershed(acre)

USEPA (1999) As percent of construction cost($)

Weiss et al. (2005) As percent of construction cost($)

Constructed Wetlands

2%

4% - 14.2%

C = 4,502X

0.153

Wet Detention Basins

NR

1.9% - 10.2%

C = 9,202X

0.269

Infiltration Trenches

5% - 20%

5.1% – 12.6%

Bioretention Basins

5% - 7%

0.7% - 10.9%

BMP

Best Management Practices Construction Costs, Maintenance Costs, and Land Requirements Barr Engineering Company

NR C = 3,437X

0.152

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BMP Infiltration Basins

USEPA (1999) As percent of construction cost($)

Weiss et al. (2005) As percent of construction cost($)

Wossink et al., (2003) C = Cost($) X = size of watershed(acre)

1% - 10%

2.8% - 4.9%

NR

<1%

1.8% - 2.7%

NR

11% -13%

0.9% - 9.5%

Dry Ponds Sand Filters

C = 10,556X

0.534

NR = Not reported

Table 5

Summary of BMP Land Areas from Estimator Models

USEPA (1999) As percent of tributary impervious area

Weiss et al. (2005) As percent of construction cost

Wossink et al., (2003) SA = Surface Area(acre) X = size of watershed(acre)

Constructed Wetlands

3-5%

NR

SA=0.01X (1%)

Wet Detention Basins

2-3%

NR

SA=0.0075X (0.75%)

Infiltration Trenches

2-3%

NR

NR

Bioretention Basins

5%

NR

SA=0.015X (1.5%)

Infiltration Basins

2-3%

NR

NR

Dry Ponds

2-3%

NR

NR

0%-3%

NR

NR

BMP

Sand Filters NR = Not reported

4.2. Comparison of Collected Data with Estimator Models 4.2.1

Construction Cost Comparison

The construction cost data collected for this study were compared to data and analyses done by Weiss et al. (2005), and USEPA (1999). Most BMP costs reported in those studies compare well with the data collected here (Table 1) but there are a few large deviations and a few BMPs have a wide range of costs (more than one order of magnitude and high standard deviations). This fact illustrates the difficulty of generalizing BMP construction costs. These costs should be used for general estimating purposes. More detailed analysis of the site conditions and design variables for each project will produce more accurate numbers. Table 6 shows that for constructed wetlands, large wet detention basins, infiltration trenches, and sand filters, these three sources are relatively consistent. This study shows a significant cost Best Management Practices Construction Costs, Maintenance Costs, and Land Requirements Barr Engineering Company

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difference between large and small wet detention basins. The small wet detention basin number is too high. Based on experience, it should be no more than ten times the cost of the large basin. The large difference could be due to many unknown variables including the possibility that land costs could be included, or the small basins are lined and serve more as a decorative landscape feature than a utilitarian stormwater pond. The cost data collected for this study for biofiltration basins is about four times higher than for bioretention basins. The design of the two BMPs is very similar. The primary difference is the drain tile in the biofiltration BMP. This will not increase the cost four times. Typically, a biofiltration basin cost should not be more than 25% higher than a bioretention basin. Construction costs for infiltration basins identified in this study were significantly higher than those identified in other studies. The high cost may be due to the small sample size for the data collected for this study or reflect a tendency toward higher costs in a set of California transportation projects, which represent five of the six data points for infiltration basins. However, the low cost reported by the USEPA study seems too low when compared to other somewhat similar BMPs, such as bioretention basins. A cost near the middle of the two numbers is likely the most accurate. Table 6

Comparison of Construction Cost Estimator Models to Study Data

USEPA (1999) Construction cost converted to 2010 $ 3 per ft of treated water volume

Weiss et al. (2005) Construction cost converted to 2010 $ 3 per ft of treated water volume

This study Construction cost converted to 2010 $ 3 per ft of treated water volume

Constructed Wetlands

0.8-1.7

0.2-2.4

1.

Large Wet Detention Basins

0.7-1.4

0.3-3.7

2.

Infiltration Trenches

5.4

6.5-11.5

11.

Bioretention Basins

7.2

10.1-11.3

15.

Pervious Pavement

NR

NR

16.

Infiltration Basins

1.80

NR

21.

Dry Ponds

0.7-1.4

0.3-5.0

NR

Sand Filters

4.1-8.2

3.4-16.8

15.

BMP

NR = Not reported

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4.2.2

Annual Maintenance Cost Comparison

Annual maintenance cost data was available for less than half of the sites. The annual maintenance cost data that was available was compared to data and analyses done by Weiss et al. (2005), and USEPA (1999). Maintenance cost estimation “models” developed in those studies generally compare well with the data collected here. Table 7 shows that for wet detention basins, infiltration trenches, and bioretention basins, these three sources are relatively consistent. Table 7

Comparison of Annual Maintenance Cost Estimator Models to Study Data USEPA (1999) As percent of construction cost/$

Weiss et al. (2005) As percent of construction cost/$

This study As percent of construction cost/$

Constructed Wetlands

0.02

4% - 14.2%

No data

Wet Detention Basins

NR

1.9% - 10.2%

3.5%

Infiltration Trenches

5% - 20%

5.1% – 12.6%

3.6%

Bioretention Basins

5% - 7%

0.7% - 10.9%

8.3%

Infiltration Basins

1% - 10%

2.8% - 4.9%

No data

<1%

1.8% - 2.7%

No data

11% -13%

0.9% - 9.5%

No data

BMP

Dry Ponds Sand Filters NR = Not reported

4.2.3

Land Area Comparison

Land cost data was available for only a very few sites. About half of the data do include information on the BMP footprint area and watershed area. For the purposes of this comparison, watershed area was used. Table 8 compares results from previous studies with data collected for this study for BMP land area needed per watershed area. The USEPA study used area of impervious surface in the watershed as opposed to raw watershed area. The cost rate per impervious surface would generally be more useful, but the data sampled includes very little information regarding watershed characteristics beyond the raw area. Table 8 compares land area or footprint for each BMP listed, not land cost. Land costs vary widely by location. To get land cost for each BMP, multiply the land area required by the local land cost. The project data collected for this study compares reasonably well with the prior studies. The projects land requirements collected here were closer to the USEPA results for percent per Best Management Practices Construction Costs, Maintenance Costs, and Land Requirements Barr Engineering Company

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impervious area in the watersheds. This may be due to the apparent tendency of the reported projects to have high impervious rates in watersheds, such as road-related and institutional projects. It probably also has root in the general variability in the data described in Section 3.2.1. Table 8

Comparison of BMP Land Area Estimator Models to Study Data USEPA (1999) As percent of impervious area

Wossink et al., (2003) As percent of watershed area

This study As percent of watershed area

Constructed Wetlands

3-5%

1%

6.5%

Wet Detention Basins

2-3%

0.75%

2.2%

Infiltration Trenches

2-3%

NR

No data

Bioretention Basins

5%

1.5%

4.1%

Infiltration Basins

2-3%

NR

2.4%

Dry Ponds

2-3%

NR

No data

0%-3%

NR

No data

BMP

Sand Filters NR = Not reported

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5.0 Land Area Requirements 5.1

Introduction and Research Approach

An important cost of any structural stormwater BMP is the land on which the BMP is located. Land requirements associated with BMPs include the area needed for the BMP itself plus the area needed to perform maintenance activities and provide access to the BMP. The amount of land needed varies with the type of BMP and the design requirements of that BMP. Regulations of the permitting authority also affect the land requirements of individual BMPs, though to a much lesser extent. These requirements may stipulate the area needed to perform maintenance and access to the BMP. Some local regulations also require vegetated buffers be used in conjunction with structural BMPS or as a separate planning type BMP. Where local governments have such regulations, they are often enforced through the conveyance of an easement to the permitting authority. The land area required to access and maintain six structural BMPs for six developing communities is documented in Appendix B. As part of this effort, the land requirements for stream, lake and wetland vegetated buffers for these communities was also identified. The six developing communities included the cities of St. Cloud, Baxter, Rochester, Hanover, Northfield, and Inver Grove Heights. The zoning and subdivision regulations and stormwater management regulations of each city were reviewed for access and maintenance requirements, which were most often defined as easements. Local regulations were also reviewed for vegetated buffer requirements. In most cases, calls were made to city planners and engineers to clarify the intent and administration of these regulations. Following is a summary of the land area requirements (easements) and vegetated buffer requirements for these cities.

5.2

Land Area Requirements for Structural BMPs

5.2.1

O&M Responsibility Policy

Whether a city receives fee title for the land or an easement depends on where primary responsibility for operating and maintenance (O&M) lies. If the city determines that it wants primary O&M responsibility, the city will take fee title to the land on which the BMP lies along with access to the BMP. Wet detention basins are the most common BMP for which cities will take this primary O&M responsibility. This is because these facilities are viewed as flood control devices and cities have a basic responsibility for the health safety and welfare of their property owners. In most situations, primary O&M responsibility for BMPs other than wet detention basins lies with the property owner. In these cases, an access easement is granted to the city for purposes of conducting inspections. Best Management Practices Construction Costs, Maintenance Costs, and Land Requirements Barr Engineering Company

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Cities may use the access easement to perform maintenance either through an agreement or due to an enforcement action. In terms of defining O&M responsibility, St. Cloud and Northfield represent different ends of the policy spectrum. St. Cloud will only take responsibility for wet detention basins and then only in limited situations where flood control is deemed a high priority. For all other BMPs, St. Cloud requires that the property owner take sole responsibility for O&M. In contrast, Northfield is moving in the direction of taking primary responsibility for many BMPs to insure their long term water quality performance. In these situations, the city will take fee title of the land on which the BMP is located as well as access to the land. The City of Rochester is different from most cities in that it does not require any easements. Instead, Rochester requires a detailed maintenance agreement for all BMPs required by a stormwater management plan, but not voluntary BMPs such as small rainwater gardens. Through the maintenance agreement, the city secures its right to access the BMP for inspection and enforcement action.

5.2.2 Area Requirements The specific easement requirements that each city has for each BMP is shown in Appendix B. Cities vary widely on the specific requirements for the six BMPs. Rochester does not have any dimensional requirements for the BMPs, except for grass swales. St. Cloud does not have any dimensional requirements, except for wet detention basins. Easements for above-ground BMPs (bioretention basins, biofiltration basins and wet detention basins) include the BMP plus an area around the BMP. This area around the BMP is defined differently for each city. Definitions include: top of bank plus 10 feet, up to the 100-year flood level, the high water level plus 50 feet, and 30 feet from the ordinary high water level. Ten to 20-foot easements from the nearest right-of-way (ROW) are typically required for access to these above ground BMPs. For most cities, the term grass swale refers to drainage easements along property lines. These typically vary between 10 and 20 feet centered on the property line. For other types of grass swales, easements are required but not defined. Easements are determined on a case-by-case basis and depend on the size and function of the swale. Hanover was the only city to specify an easement dimension for something other than a grass swale within a property line drainage easement. Hanover requires a 30 foot easement extending outward of the ordinary high water level of the grass swale.

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Easement policy for pervious pavement and underground infiltration BMPs is less well defined for most cities. Many have not encountered these types of BMPs yet or they are still relatively rare. As a result, cities have not yet determined specific dimensional requirements or policies.

5.3

Vegetated Buffer Requirements

Three of the cities reviewed have specific dimensional requirements for establishing vegetated buffers. Northfield has the strictest standard in this regard. The City requires the establishment of a 50 foot vegetated buffer around bioretention basins, biofiltration basins and wet detention basins. The City also requires establishment of a 50 foot buffer around all wetlands extending outward from the delineated edge. Hanover requires the establishment of a 30 foot buffer and easement around wetlands and a 30 foot easement from the ordinary high water level of streams and lakes. Inver Grove Heights requires a 10 foot buffer around the permanent pool of wet detention basins and 10 – 15 feet around wetlands. All other cities reference the buffer requirements in the Shoreland Rules. These rules define measures for protecting existing buffers; they do not require the establishment of new vegetated buffers.

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6.0 MIDS Calculator In many ways, the study data supports the work of Weiss et al. for construction costs and operation and maintenance costs. Data ranges and distributions are similar and include a graphical representation of a 67% confidence level for each BMP. The Weiss report also links contaminant removal effectiveness to cost, which would be useful in evaluation of approaches. The Weiss et al. analyses might provide a relatively accurate platform for developing a simple “calculator” for construction and maintenance costs. Land cost estimates become more problematic because those costs vary considerably by locale. A simple method using a model of BMP footprint area based on watershed or impervious area might be effectively paired with local land values for use in cost estimating. Easement requirements for maintenance and access are relatively small compared to the area needed for the BMP itself. The MIDS calculator could include a dimensional requirement for this to provide the user with an estimate of the land area needed to meet these requirements. A typical range that could be included as an input into the calculator would be 30 – 50 feet from the high water level of any above ground BMP.

Best Management Practices Construction Costs, Maintenance Costs, and Land Requirements Barr Engineering Company

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References American Public Works Association (APWA). (1992). A Study of Nationwide Costs to Implement Municipal Storm Water Best Management Practices. Southern California Chapter. Water Resource Committee. A Public Works Perspective on the Cost Vs. Benefit of Various Stormwater Management Practices, WSB Inc. (2007). Bloomington Pervious parking area bid tabs, city of Bloomington, (2009). Century College, White Bear Lake, MN Parking Lot Reconstruction Plans and Specifications, (2009). City of Shoreview Road Construction, American Public Works Assn, (2009). East 145th Street Rain Garden/Infiltration Basin, Barr Engineering Co, (2010). International Stormwater BMP Database: Cost Data Included in July 2007 Database Release, Wright Water Engineers, Inc. and GeoSyntec Consultants (2007). Lockheed Martin Eagan MN parking Lot 1, Barr Engineering Co, (2009). Medford MN School Stormwater Wetlands, Barr Engineering Co., (2008). Oakgreen Avenue, Afton MN; Infiltration Basin Construction Plans and Data, Barr Engineering Co., (2007). Owatanna Test Alley, Owatonna City Council Packet March 23, 2010. Stormwater BMP Costs, North Carolina State University (2007). Stormwater BMP Performance Assessment and Cost-Benefit Analysis, Capitol Region Watershed District, (2010). U.S. Environmental Protection Agency (USEPA). (1999). “Preliminary data summary of urban stormwater best management practices.” EPA-821-R-99-012, Washington, D.C. Villanova Urban Stormwater Partnership Website, BMP Research, (2010). Weiss, P.T., J. S. Gulliver and A. J. Erickson, (2005). “The Cost and Effectiveness of Stormwater Management Practices,” Minnesota Department of Transportation Report 2005-23. Wossink, Ada, Hunt Bill, (2003) The Economics of Structural Stormwater BMPs in North Carolina, UNC-WRRI-2003-344.

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Appendix A BMP Cost Survey Data Tables

Appendix A: BMP Cost Survey Data Tables DATA SOURCES 1) International Stormwater BMP Database Cost Data Included in July 2007 Database Release, Wright Water Engineers, Inc. and GeoSyntec Consultants (2007) 2) Century College, White Bear Lake, MN Parking Lot Reconstruction Plans and Specifications, (2009) 3) A Public Works Perspective on the Cost Vs. Benefit of Various Stormwater Management Practices, WSB Inc. (2007) 4) Stormwater BMP Costs, North Carolina State University (2007) 5) Stormwater BMP Performance Assessment and Cost-Benefit Analysis, Capitol Region Watershed District, (2010) 6) Oakgreen Avenue, Afton MN; Infiltration Basin Construction Plans and Data, Barr Engineering Co., (2007) 7) Medford MN School Stormwater Wetlands, Barr Engineering Co., (2008) 8) East 145th Street Raingarden/infiltration basin, Barr Engineering Co., (2010) 9) City of Shoreview road construction, American Public Works Assn, (2009) 10) Lockheed Martin Eagan MN parking Lot 1, Barr Engineering Co., (2009) 11) Owatonna Test Alley, Owatonna City Council Packet March 23, 2010 12) Bloomington Pervious parking area bid tabs, city of Bloomington, (2009) 13) Villanova Urban Stormwater Partnership Website, BMP Research, (2010)

Appendix A: Data Sources

A-1

Barr Engineering Co.

BMP Site Name Arlington Pascal SIP Pascal North RG Arlington Pascal SIP Pascal Center RG Arlington Pascal SIP Pascal South RG

BMP Type raingarden raingarden raingarden

Ownership City of St Paul City of St Paul City of St Paul

Arlington Pascal SIP Arlington-McKinley RG raingarden Century College Infiltration planter raingarden Arlington Pascal SIP Asbury North RG raingarden

City of St Paul Century College City of St Paul

Century College Raingardens (3) Arlington Pascal SIP Asbury South RG VUSP Bio-Infiltration Traffic Island Arlington Pascal SIP Frankson-McKinley RG Arlington Pascal SIP Hamline Midway RG

Century College City of St Paul

raingarden raingarden Infiltration raingarden raingarden

City of St Paul City of St Paul

Appendix A: Biofiltration/Raingardens

Footprint Arrea

Units

Total Watershed Area

Units

Capture Volume of Basin

Units

Watershed Land Use

Construction Costs

Under drain

Adjusted maint costs

Average Annual Year of Maintenance Cost Costs Estimate

State

Data Source

Cost in 2010 Rain Zone CPI factor dollars Factor

Cost per Capture Volume (cf)

Zone 1 - 2010 dollars

357 ft2

0.46 ac

209 cf

mixed

$6,750 no

474

474

2010

MN

5

1.00

$6,750

1.12

$6,750

$32

536 ft2

0.13 ac

227 cf

mixed

$5,421 no

793

793

2010

MN

5

1.00

$5,421

1.12

$5,421

$24

710 ft2

0.36 ac

344 cf

mixed

$8,648 no

535

535

2010

MN

5

1.00

$8,648

1.12

$8,648

$25

767 ft2

0.37 ac

349 cf

mixed

$4,115 no

486

486

2010

MN

5

1.00

$4,115

1.12

$4,115

$12

864 cf

Impervious

$17,425 no

2009

MN

2

1.01

$17,652

1.12

$17,652

$20

2010

MN

5

1.00

$9,246

1.12

$9,246

$9

2009

MN

2

1.01

$27,339

1.12

$27,339

$14

2010

MN

5

1.00

$11,971

1.12

$11,971

$6

2001

PA

1

1.23

$31,257

1.12

$31,257

$14

864 ft2 945 ft2

1,045 cf

mixed

$9,246 no

1,944 ft2

0.40 ac ( 3 combin 0.8 ed)

612

1,944 cf

Impervious

$26,988 no

1,712 ft2

1.08 ac

2,113 cf

mixed

$11,971 no

1499 ft2

1.16 ac

2,258 cf

mixed

$25,412 no

2,078 ft2

2.80 ac

2,494 cf

mixed

$10,921 no

645

645

2010

MN

5

1.00

$10,921

1.12

$10,921

$4

6,364 ft2

10.50 ac

12,576 cf

mixed

$103,172 no

1602

1,602

2010

MN

5

1.00

$103,172

1.12

$103,172

$8

655

Ave maint

$1.25

SD maint

$1.18

A-2

612

655

Average Standard Deviation

$15 $9

Barr Engineering Co.

BMP Site Name

BMP Type

Ownership

145th Street Infiltration Basin, Burnsville

raingarden

City of Burnsville

VUSP Bio-Infiltration Traffic Island

filtration trench

Villanova U

Footprint Arrea

Units

Total Watershed Area

Capture Volume of Units Basin

15,000 ft2

6,250 cf

130 ft2

300 cf

Units

Watershed Expected Land Use Life Span

Year of Cost Estimate

$91,124 yes $27,900

Construction Costs

Underdrain

Average Annual Maintenance Costs

Cost in 2010 dollars

Rain Zone Zone 1 - 2010 Factor dollars

State

CPI factor

2010

MN

8

1.00

$91,124

1.12

$91,124

$15

2004

PA

13

1.12

$31,248

1.15

$30,327

$101.09

Average Standard Deviation

Appendix A: Filtration data

A-3

Cost per Capture Volume (cf)

Data Source

$58 $61

Barr Engineering Co.

BMP Type

Units

Watershed Land Use

Expected Life Span

Construction Costs

Land Costs or Value

Adjusted Maint Costs

Average Annual Maintenance Costs

Year of Cost Estimate

State

Data Source

Cost in 2010 Rain Zone CPI factor dollars Factor

Zone 1 - 2010 dollars

Cost per treatment volume (cf)

Wet Pond

700 cf

1.6 ac

$57,000

1995

CO

1

1.43

$81,568

0.76

$120,205

$172

Wet Pond

700 cf

1.6 ac

$57,000

1996

CO

1

1.39

$79,174

0.76

$116,677

$167

I-5 / La Costa (east)

Wet Pond

9,150 cf

4.2 ac

$769,841

2000

CA

1

1.27

$974,619

1.24

$880,301

$96

Central Park Wet Pond Traver Creek Detention Basin Cockroach Bay Agricultural Site Pittsfield Retention Basin Como Park Regional Pond

Wet Pond

273,000 cf

1639.6 ac

$585,000

1994

TX

1

1.47

$860,535

0.67

$1,438,506

$5

Wet Pond

512,000 cf

2303.2 ac

$187,011

1980

MI

1

2.65

$494,831

1.12

$494,831

$1

Wet Pond

564,793 cf

210.0 ac

$563,547

Wet Pond

914,760 cf

4872.8 ac

$404,931

2,074,893 cf

128 ac

City of St Paul

Units

Total Watershed Area

BMP Site Name Lakewood RP SF Vault (95) Lakewood RP - MF Vault (96)

Wet Pond

Ownership

Treated Volume

mixed

35

$1,364,364 Ave maint SD maint

Appendix A: Wet Ponds

$55,327.16

$22,500

$128,750

$128,750

$3,482.87

$1,500

1996

FL

1

1.39

$782,767

0.67

$1,308,506

$2

$70,142.58

$20,214

1977

MI

1

3.47

$1,405,109

1.12

$1,405,109

$2

$4,550.00

$4,550

2010

MN

5

1.00

$1,364,364

1.12

$1,364,364

$1

$0.07

Average

$56

$0.10

Standard Deviation

$77

A-4

Average (small) Standard Deviation

Average (large) Standard Deviation

Barr Engineering Co.

$145 $42

$2 $2

BMP Site Name

BMP Type

Ownership

Footprint Area

USA Brookley Golf Course Hank Aaron Stadium NW Wetland Mobile County Extension Service Hank Aaron Stadium SW Wetland Medford MN School Stormwater Wetlands Swift Run Wetland

Wetland Wetland

1.3 ac

Wetland

Total Units Watershed Area 2.5 ac 10.80 ac

Capture Volume of Basin

Units

Watershed Expected Land Use

Construction

Life Span

84,942 cf

Steele County

Land Costs or Value

Average Annual Maintenance Costs

Year of Cost Estimate 1994

State

Data

AL

Source 1

1.47

$5,000

1998

AL

1

1.34

$6,685

0.67

$11,175

$1,500

1996

AL

1

1.39

$2,084

0.67

$3,483

Costs $16,000

12.1 ac

Wetland Wetland System Wetland

Units

CPI factor

Cost in Rain Zone Zone 1 - 2010 2010 dollars dollars Factor $23,536 0.67 $39,344

Volume

$0.13

0.25 ac

17.90 ac

16,335 cf

$5,000

1998

AL

1

1.34

$6,685

0.67

$11,175

$0.68

3 ac

50.7 ac

69,696 cf

$225,000

2008

MN

7

1.01

$227,925

1.12

$227,925

$3.27

1207.10 ac

1,076,991 cf

1983

MI

1

2.19

$106,714

1.12

$106,714

$0.10

$48,750 $101,000

Average Standard Deviation

Appendix A: Constructed Wetlands

Cost per WQ

A-5

$1.05 $1.51

Barr Engineering Co.

Footprint Arrea

Capture Volume of Basin Units

Watershed Land Use

Expected Life Span

Construction Land Costs Adjusted Costs or Value maint costs

Average Annual Year of Maintenance Cost Costs Estimate

State

Data Source

CPI factor

2010

MN

5

1.00

$20,039

1.12

$20,039

$10.71

2010

MN

5

1.00

$25,812

1.12

$25,812

$10.71

2000

CA

1

1.27

$97,974

1.24

$88,493

$36.28

$1,108

2010

MN

5

1.00

$29,058

1.12

$29,058

$10.71

$1,112.00

$1,112

2010

MN

5

1.00

$29,807

1.12

$29,807

$10.71

Trench Average

$10.71

$34,766

$1,518.00

$1,518

2010

MN

5

1.00

$34,766

1.12

$34,766

$10.71

Trench SD

$30.13

35

$85,599

$2,165.00

$2,165

2010

MN

5

1.00

$85,599

1.12

$85,599

$10.71

mixed

35

$86,595

$2,170.00

$2,170

2010

MN

5

1.00

$86,595

1.12

$86,595

$10.71

mixed

35

$88,383

$2,179.00

$2,179

2010

MN

5

1.00

$88,383

1.12

$88,383

$10.71

$329,833

2000

CA

1

1.27

$417,569

1.24

$377,159

$41.23

Dry Pond Average

$20.98

13,068 cf

$127,202

2000

CA

1

1.27

$161,038

1.24

$145,453

$11.13

Dry Pond SD

$15.50

5.3 ac

13,809 cf

$143,555

2000

CA

1

1.27

$181,741

1.24

$164,153

$11.89

13.4 ac

39,640 cf

$819,852

2000

CA

1

1.27

$1,037,933

1.24

$937,488

$23.65

35.6 ac

82,764 cf

$136,000

2007

MN

6

1.05

$142,936

1.12

$142,936

$1.73

BMP Site Name

BMP Type

Ownership

Arlington Pascal SIP Trench 1

Underground infiltration trench

City of St Paul

0.74 ac

1,871 cf

mixed

35

$20,039

$1,061.00

$1,061

Arlington Pascal SIP Trench 5

Underground infiltration trench

City of St Paul

1.28 ac

2,410 cf

mixed

35

$25,812

$1,091.00

$1,091

I-605 / SR-91 EDB

Dry Pond

0.8 ac

2,439 cf

Arlington Pascal SIP Trench 7

Underground infiltration trench

City of St Paul

1.63 ac

2,713 cf

mixed

35

$29,058

$1,108.00

Arlington Pascal SIP Trench 2

Underground infiltration trench

City of St Paul

0.84 ac

2,783 cf

mixed

35

$29,807

Arlington Pascal SIP Trench 6

Underground infiltration trench

City of St Paul

2.60 ac

3,246 cf

mixed

35

Arlington Pascal SIP Trench 8

Underground infiltration trench

City of St Paul

7.08 ac

7,992 cf

mixed

Arlington Pascal SIP Trench 4 Arlington Pascal SIP Trench 3

Underground infiltration trench Underground infiltration trench

City of St Paul

5.29 ac

8,085 cf

City of St Paul

3.21 ac

8,252 cf

I-5/Manchester (east)

Dry Pond

4.8 ac

9,148 cf

I-5 / I-605 EDB

Dry Pond

2.7 ac

I-5 / SR-56

Dry Pond

I-15/SR-78 EDB

Dry Pond

Oakgreen Infiltration Basin Infiltration Pond

Watershed

36,460 ft2

Units

Total Watershed Area

Units

$77,389

Ave maint SD maint

Appendix A: Infiltration

A-6

Cost in 2010 Rain Zone dollars Factor

Zone 1 - 2010 dollars

Cost per Capture Volume (cf)

$0.39

Average

$15

$0.11

Standard Deviation

$11

Barr Engineering Co.

BMP Site Name

BMP Type

Ownership

Volume of permanent pool

I-210 / Orcas Ave

Hydro-dynamic Device

612.00 cf

I-210 / Filmore Street Jensen Precast (UVA) Phase II Charlottesville Stormceptor

Hydro-dynamic Device

36.73 cf

Hydro-dynamic Device

1751.96 cf

Hydro-dynamic Device

36.73 cf

Hydro-dynamic Device

307.47 cf

Units

Water Quality Surcharge Detention Volume When Full

Units

Units

Watershed Land Use

Expected Life Span

Construction Land Costs Adjusted Maint Costs or Value Cost

Zone 1 - 2010 dollars

State

2001

VA

1

1.231

$48,056

0.9

$59,803

2000

CA

1

1.27

$50,640

1.24

$45,739

2000

CA

1

1.27

$77,882

1.24

$70,345

2000

CA

1

1.27

$63,300

1.24

$57,174

2000

VA

1

1.27

$27,536

0.9

$34,266

$23

$13,707

1.10 ac

$40,000

2.00 ac

$61,518

2.50 ac

$50,000

1,490 cf

2.50 ac

$21,750

Hydro-dynamic Device

32,000 cf

5.5 ac

impervious

30

$121,000

2009

MN

2

1.016

$122,936

1.12

$122,936

$4

$22,352

Austin Rec Center OSTC Hydro-dynamic Device Indian River Lagoon CDS Unit Hydro-dynamic Device

29,900 cf

10 ac

impervious

30

$160,000

2009

MN

2

1.016

$162,560

1.12

$162,560

$5

$16,256

$23,421

1998

FL

1

1.337

$31,314

0.67

$52,346

$498

$2,137

2010

MN

5

1

$799,087

1.12

$799,087

$1

$15,982

1997

FL

1

1.358

$74,690

0.67

$124,855

$1,037

$2,030

$1,250

1996

TX

1

1.389

$69,450

0.67

$116,096

$1,290

$5,000

2007

MN

3

1.051

$1,261,200

1.12

$1,261,200

$2,522

Vortec device Century College East underground Century College West underground Arlington-Hamlin Facility

Hydro-dynamic Device Underground Treatment Underground Treatment Vortex + underground storage/infiltration

101.71 cf City Century College Century College Private

Appendix A: Underground Structures

260.98 cf

105 cf cf - treated 777,154 volume 120 cf

24.50 ac 50 ac

mixed

35

$55,000

90.00 ac

$50,000 30

$6,695.73

$799,087

61.50 ac

500 ac

$314.46

$2,867.00

$10,000

1,200,000 ROW Ave maint

$1.26

SD maint

$2.16

A-7

$150

Data Cost in 2010 Rain Zone Source CPI factor dollars Factor

Cost per treatment volume Cost per (cf) Watershed acre

Year of Cost Estimate

$39,038

1,752 cf

$229.79

Average Annual Maintenance Costs

0.28 ac

Sunset Park Baffle Box Jensen Precast (Sacramento)

612 cf

Total Watershed Area

$275

$4,250

$2,867

Average Standard Deviation

$98

$213,581 $41,581

$40

$35,172 $22,870

$213

$32,457

$372

$58,534

Barr Engineering Co.

BMP Site Name Dayton Grass Pavement Parking Lot Century College porous pavement UDFCD Modular Porous Pavement 94 to 04 Century College porous pavement

BMP Type Grass Block

Asphalt

Units

treatment volume of base

30,139 ft2 Century College

Block

Owatonna Test Alley Asphalt Lockheed Martin Eagan MN parking Lot 1 Asphalt Austin Porous Asphalt Lot Bloomington Harrison Park parking area Lockheed Martin Eagan MN parking Lot 1 Century College porous pavement

Ownership

Footprint Arrea

Century College

units

Total Watershed Area

Units

Watershed Land Use

0.79 ac

2,200 ft2 90,417 ft2

0.21 ac

4,500 ft2

3.6 ac

State

1981

OH

1

2.40

$31,203

1.12

$31,203

$1

2009

MN

2

1.02

$25,400

1.12

$25,400

$12

1994

CO

1

1.47

$21,771

0.76

$32,083

$0.35

$40,000

2009

MN

2

1.02

$40,640

1.12

$40,640

$9

$13,012 impervious

30

30

Land Costs or Value

Average Annual Maintenance Costs $516

$25,000 $14,800

impervious

Cost per treatment Volume (cf)

Year of Cost Estimate

Expected Construction Life Span Costs

$21,300

Data Source CPI factor

Cost in 2010 dollars

Rain Zone Factor

Zone 1 - 2010 dollars

Cost per square foot

City

10,755 ft2

8,630 ft3

$64,061

2010

MN

11

1.00

$64,061

1.12

$64,061.00

$7

$6

private

10,890 ft2

7,762.50 ft3

$60,742

2009

MN

10

1.02

$61,714

1.12

$61,713.87

$8

$6

$11,240

1981

TX

1

2.40

$26,954

0.67

$45,057

Asphalt

15,070 ft2

Asphalt

City

Concrete

private

Concrete

Century College

2,800 ft2

0.35 ac

$3

25,700 ft2

18,066 ft3

$242,800

2008

MN

12

1.01

$245,956

1.12

$245,956.40

$14

$10

765 ft2

319 ft3

$7,990

2009

MN

10

1.02

$8,118

1.12

$8,117.84

$25

$11

$31,000

2009

MN

2

1.02

$31,496

1.12

$31,496

impervious

30

$11

Owatonna Test Alley Bloomington Public Works parking area

Concrete

City

6,030 ft2

4,278 ft3

$90,940

2010

MN

11

1.00

$90,940

1.12

$90,940.00

$21

$15

Concrete

City

7,722 ft2

4,240 ft3

$111,400

2009

MN

12

1.02

$113,182

1.12

$113,182.40

$27

$15

City of Shoreview roadway

Concrete

City

76,266 ft2

67,500 ft3

$731,000

2009

MN

9

1.02

$742,696

1.12

$742,696

$11

$10

$16

$8

$8

$5

Average Standard Deviation

Appendix A: Porous Pavement

A-8

Barr Engineering Co.

BMP Site Name

BMP Type

Ownership

Length

Total Watershed Units Area

Units

Watershed Land Use

Expected Life Span

Construction Costs

Land Costs Adjusted or Value maint costs

Average Annual Maintenance Costs

Year of Cost Estimate

State

Data Cost in 2010 Rain Zone Zone 1 - 2010 Source CPI factor dollars Factor dollars

Cost per Watershed Acre

Cost per length (ft)

Carlsbad Biofiltration Strip

Swale

26.0 ft

2.4 ac

$230,000

2000

CA

1

1.27

$291,180

1.24

$263,001

$109,586

$10,115

Altadena (strip)

Swale

26.0 ft

1.7 ac

$300,000

2000

CA

1

1.27

$379,800

1.24

$343,045

$201,795

$13,194

I-605/SR-91 Strip

Swale

26.0 ft

0.5 ac

$110,000

2000

CA

1

1.27

$139,260

1.24

$125,783

$251,571

$4,838

Cerritos MS

Swale

66.0 ft

0.4 ac

$60,000

2000

CA

1

1.27

$75,960

1.24

$68,609

$171,526

$1,040

Monticello High School Florida Aquarium Test Site - F8 Florida Aquarium Test Site - F6 Florida Aquarium Test Site - F4

Swale

95.0 ft

0.8 ac

$15,000

2000

VA

1

1.27

$18,990

0.90

$23,632

$30,298

$249

Swale

130.0 ft

0.3 ac

$8,333

1995

FL

1

1.431

$11,925

0.67

$19,934

$76,666

$153

Swale

130.0 ft

0.3 ac

$8,333

1995

FL

1

1.431

$11,925

0.67

$19,934

$76,666

$153

Swale

130.0 ft

0.3 ac

$8,333

1995

FL

1

1.431

$11,925

0.67

$19,934

$76,666

$153

I-5/I-605 Swale

Swale

131.0 ft

0.7 ac

$73,179

2000

CA

1

1.27

$92,645

1.24

$83,679

$119,544

$639

I-605/SR-91 Swale

Swale

131.0 ft

0.2 ac

$110,000

2000

CA

1

1.27

$139,260

1.24

$125,783

$628,927

$960

I-605 / Del Amo

Swale

177.0 ft

0.7 ac

$130,000

2000

CA

1

1.27

$164,580

1.24

$148,653

$212,365

$840

SR-78 / Melrose Dr I-5 North of Palomar Airport Road

Swale

347.0 ft

2.4 ac

$133,077

2000

CA

1

1.27

$168,475

1.24

$152,171

$63,406

$439

Swale

465.0 ft

4.6 ac

$140,000

2000

CA

1

1.27

$177,240

1.24

$160,088

$34,802

$344

$157,986

$2,547

$158,031

$4,272

Ave maint

Appendix A: Swales

$472.64

$300

$4.98

Average Standard Deviation

A-9

Average (short) Standard Deviation

Average (long) Standard Deviation

Barr Engineering Co.

$9,382 $4,226

$497 $309

Appendix B Land Requirements (Easements) for Stormwater BMPs

Appendix B: Land Requirements (fee title, easement) for Stormwater BMPs St. Cloud BMP Type Bioretention Basin/Rainwater Garden

Public Responsibility

Rochester Private Responsibility

Public Responsibility

Private Responsibility

Inver Grove Heights Public Responsibility Private Responsibility

Baxter Public Responsibility

Northfield Private Responsibility

Public Responsibility

Hanover Private Responsibility

Public Responsibility

Private Responsibility

None. Private property owner has sole O&M responsibility for this type of BMP.

No specific requirements for easements or fee title. BMP located on private property. Property owner/developer responsible for O&M in accordance with submitted plan. Plan not recorded.

City receives fee title if City No easements required. A detailed determines it wants control and maintenance agreement is required primary O&M responsibility. Land and recorded (1). requirements include at a minimum: reasonable access to facility and facility.

City receives fee title if City determines it wants control and primary O&M responsibility. Land requirements include at a minimum those specified for easements under private responsibility.

Easement required up to 100-year 24hour flood elevation if sewered, otherwise up to 10-day snowmelt elevation if landlocked. Additional easement required (not specified) to allow room to conduct maintenance without affecting infiltration capacity. Easement required for 20 feet access to facility. Recorded maintenance agreement identifies individual party responsibilities.

City receives fee title if City determines it wants control and primary O&M responsibility. Land requirements include at a minimum those specified for easements under private responsibility.

Easement required up to top of bank plus 10 feet beyond top of bank. 10 foot easement also required to access facility.

City receives fee title if City determines it wants control and primary O&M responsibility. Land requirements include at a minimum those specified for easements under private responsibility.

Easement required to high water level of facility plus 50 feet of vegetated buffer as well as reasonable access to facility. Detailed maintenance agreement required and recorded.

City receives fee title if City determines it wants control and primary O&M responsibility. Land requirements include at a minimum those specified for easements under private responsibility.

Easement required over facility plus 30 feet from the Ordinary High Water (OHW) level as well as reasonable access to facility for inspection and maintenance. Detailed maintenance agreement is recorded.

Filtration Basin/Rainwater Garden

None. Private property owner has sole O&M responsibility for this type of BMP.

No specific requirements for easements or fee title. BMP located on private property. Property owner/developer responsible for O&M in accordance with submitted plan. Plan not recorded.

City receives fee title if City No easements required. A detailed determines it wants control and maintenance agreement is required primary O&M responsibility. Land and recorded (1). requirements include at a minimum: reasonable access to facility and facility.

City receives fee title if City determines it wants control and primary O&M responsibility. Land requirements include at a minimum those specified for easements under private responsibility.

Easement required up to 100-year 24hour flood elevation if sewered, otherwise up to 10-day snowmelt elevation if landlocked. Additional easement required (not specified) to allow room to conduct maintenance without affecting infiltration capacity. Easement required for 20 feet access to facility. Recorded maintenance agreement identifies individual party responsibilities.

City receives fee title if City determines it wants control and primary O&M responsibility. Land requirements include at a minimum those specified for easements under private responsibility.

Easement required up to top of bank plus 10 feet beyond top of bank. 10 foot easement also required to access facility.

City receives fee title if City determines it wants control and primary O&M responsibility. Land requirements include at a minimum those specified for easements under private responsibility.

Easement required to high water level of facility plus 50 feet of vegetated buffer as well as reasonable access to facility. Detailed maintenance agreement required and recorded.

City receives fee title if City determines it wants control and primary O&M responsibility. Land requirements include at a minimum those specified for easements under private responsibility.

Easement required over facility plus 30 feet from the OHW level as well as reasonable access to facility for inspection and maintenance. Detailed maintenance agreement is recorded.

Grass Swale

Easement required. Minimum 10 feet along property lines (5 feet per side), or more depending on design.

Porous Pavement

No additional requirement if land already in public ROW.

Wet Detention Basin (Pond)

Easement required. 12 foot wide City receives fee title if City access to pond. 15-20 feet beyond determines it wants control and extent of 100-year 24-hour elevation. primary O&M responsibility. Land requirements include at a minimum: 12 foot wide access to pond. 15-20 feet beyond extent of 100-year 24hour elevation.

Underground Storage and Infiltration

None. Private property owner has sole O&M responsibility for this type of BMP.

Vegetated Stream, Lake and Wetland Buffers

No specific requirements. A case-by-case determination is made based on guidance provided by Natural Resource Plan.

Easement required: at least 20 feet along property lines (10 feet per side), or Easement required. Dimensions vary depending on size of swale. more depending on design.

No specific requirements for No additional requirement if land easements or fee title. BMP located already in public ROW. on private property. Property owner/developer responsible for O&M in accordance with submitted plan. Plan not recorded.

No specific requirements for easements or fee title. BMP located on private property. Property owner/developer responsible for O&M in accordance with submitted plan. Plan not recorded.

No easements required. A detailed maintenance agreement is required and recorded (1).

2 feet wide swale required in ROW along road edge for rural edge ditch drainage. 10 feet required along side and rear property lines. Larger swales may be required depending on design needs.

Easement required - depends on size of swale.

A 30 foot easement extending outward from the OHW level of swales is required. A drainage easement of 12 feet centered on side and rear lot lines and 10 feet along front lot lines and unplatted land is also required.

No additional requirement if land already in public ROW.

Easement large enough to allow vehicle access beyond pavement. Detailed and recorded maintenance agreement required.

No additional requirement if land already in public ROW.

Easement required over extent of pavement plus access to pavement. May require easement beyond pavement depending on design and site context.

No additional requirement if land already in public ROW.

Easement required over extent of pavement plus access to pavement. May require easement beyond pavement depending on design and site context. Detailed maintenance agreement required and recorded.

No additional requirement if land already in public ROW.

Easement required over facility plus access to facility for inspection and maintenance. Detailed maintenance agreement is recorded.

City receives fee title if City No easements required. A detailed maintenance agreement is required determines it wants control and primary O&M responsibility. Land and recorded (1). requirements include at a minimum: reasonable access to facility and facility.

City receives fee title if City determines it wants control and primary O&M responsibility. Land requirements include at a minimum those specified for easements under private responsibility.

City receives fee title if City determines it wants control and primary O&M responsibility. Land requirements include at a minimum those specified for easements under private responsibility.

Easement required up to top of bank plus 10 feet beyond top of bank. 10 foot easement also required to access facility.

City receives fee title if City determines it wants control and primary O&M responsibility. Land requirements include at a minimum those specified for easements under private responsibility.

Easement required to high water level of facility plus 50 feet of vegetated buffer as well as reasonable access to facility. Detailed maintenance agreement required and recorded.

City receives fee title if City determines it wants control and primary O&M responsibility. Land requirements include at a minimum those specified for easements under private responsibility.

Easement required over facility plus 30 feet from the OHW level as well as reasonable access to facility for inspection and maintenance. Detailed maintenance agreement is recorded.

City receives fee title if City No easements required. A detailed determines it wants control and maintenance agreement is required primary O&M responsibility. Land and recorded (1). requirements include at a minimum: reasonable access to facility and facility.

City receives fee title if City determines it wants control and primary O&M responsibility. Land requirements include at a minimum those specified for easements under private responsibility.

Easement required up to 100-year 24hour flood elevation if sewered, otherwise up to 10-day snow melt elevation if land locked. Easement required for 20 foot access to facility. Recorded maintenance agreement identifies individual party responsibilities. Easement required to allow access to utility access points (e.g., manholes for vac truck access). Recorded maintenance agreement identifies individual party responsibilities.

City receives fee title if City determines it wants control and primary O&M responsibility. Land requirements include at a minimum those specified for easements under private responsibility.

Easement required over extent of storage area plus access to storage facility. May require easement beyond storage area depending on design and site context.

City receives fee title if City determines it wants control and primary O&M responsibility. Land requirements include at a minimum those specified for easements under private responsibility.

City receives fee title if City determines it wants control and primary O&M responsibility. Land requirements include at a minimum those specified for easements under private responsibility.

Easement required over facility plus reasonable access to facility for inspection and maintenance. Detailed maintenance agreement is recorded.

Buffers around streams and lakes per shoreland standards.

10 foot buffer around the permanent pool of stormwater ponds. 10 - 15 feet around all wetlands. Buffers around streams and lakes per shoreland standards.

Easement required over extent of storage area plus reasonable access to storage facility. May require easement beyond storage area depending on design and site context. Detailed maintenance agreement required and recorded. A planted vegetated buffer of 50 feet is required around all wetlands extending out from the delineated wetland edge. An undisturbed vegetated buffer of 50 feet is to be maintained around all water bodies, 100 feet is required adjacent to the Cannon River and 300 feet is required adjacent to Rice Creek.

(1) Detailed maintenance agreement is required only for BMPs included in the grading plan or part of the site plan approval process. Maintenance agreement does not include any "voluntary" BMPs.

No buffer requirements other than buffer standards in Shoreland rules. City submits all plans within Shoreland Overlay District to MDNR for review and approval.

A 30 foot vegetated buffer strip and setback are required around all wetlands. Where buffers do not exist, new buffers must be planted. Flexibility for narrower buffers is allowed in special circumstances. A 30 foot easement is required around all wetlands and from the OHW level of streams and lakes.