EPA Final Report - University of New Hampshire · 2016-10-05 · EPA Final Report Work Plan Tasks: 1.) Development and Piloting of updated stormwater ordinances: This task has been

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Project: EP-W-000122

Project Title: Pollution Prevention through Green Infrastructure Requirements in

Commercial Land Uses

Report Compiled by: James Houle,

Program Manager

The UNH Stormwater Center,

35 Colovos Road

University of New Hampshire,

Durham, NH 03824

Phone: 603-862-1445

e-mail: [email protected]

EPA Final Report Work Plan Tasks:

1.) Development and Piloting of updated stormwater ordinances: This task has been completed. The

project team has worked with the town of Durham and the University of New Hampshire Facilities to

make them aware of the updated stormwater standards. These standards have largely been adopted.

This is important as collectively the town of Durham and UNH own the vast majority of the future

impervious cover (IC) increases over the next thirty years.

2.) Quantification of the reduction of hazardous materials, water saved and economic savings

resulting from implementation of the standards: Quantification of pollutant load reductions, water

saved and economic incentives has been completed for the Oyster River Watershed area.

Extrapolations have also been made for the greater Great Bay Watershed area to extend the

implications of the research and enhance the potential audience. These results are critical to advancing

stormwater management solutions at a watershed scale. This analysis is reported in a separate final

report format and included as an appendix.

3.) Outreach, education and training of commercial businesses and other governance entities: This

project has targeted municipalities and businesses in the Oyster River Watershed. Outreach has been

conducted with UNH Facilities and the Town of Durham in order to enhance and update current

stormwater management standards.

a.) A green business award and recognition program was developed and two entities have been

identified in the Oyster River Watershed who have demonstrated exemplary advancement of innovative

stormwater strategies. This recognition was offered to an engineering firm and a municipality each of

whom has initiated more stormwater management solutions than any other in the watershed.

1.) Bill Boulanger, Superintendent of Public Works & Utilities Community Services for Dover NH. 2.) Tighe and Bond Engineers, Portsmouth NH

mailto:[email protected]

2

A list of regional best management practice (BMP) installations are provided as an attachment to this report.

b.) The project has also support ongoing communication efforts associated with the Southeast

Watershed Alliance (SWA). New Hampshire legislators created SWA in 2009 to provide a framework for

watershed communities to work together to protect and restore its water resources. Two outreach

events were scheduled through SWA in the form of presentations; the first was at a Lamprey River

Watershed Workshop on May 13, 2014 and second at the SWA Quarterly Meeting Feb. 4, 2015 which

was open to the public.

In addition to these events the results of the modeling effort were presented at the 2015 NH Water &

Watershed Conference on March 19, 2015 at the Attitash Grand Summit Resort Hotel & Conference

Center in Bartlett, NH and at the 26th Annual Nonpoint Source Pollution Conference on April 28, 2015 in

Freeport, ME. Finally in cooperation with SWA a factsheet has been developed that outlines the salient

points of the project outcomes and will be finalized at the September quarterly SWA meeting.

Finally a webinar hosted by EPA Region 1 was conducted on October 1, 2015 and had 157 registered

participants.

c.) Adoption Survey of model ordinance implementation: Pre-project there were no communities that

had fully adopted the SWA standards. As of August 2015: Seven towns have either adopted or

announced plans to adopt the SWA model stormwater ordinances as a way to improve water quality

and avoid retrofit and remediation costs later: Durham, Greenland, Newfields, North Hampton,

Rochester, Rollinsford, and Stratham.

Project Deliverables:

Copies of all final project deliverables are added to this report as attachments and listed below:

1.) Attachment A: Final modeling results report

2.) Attachment B: Final educational fact sheet

3.) Attachment C: Final list of BMP installations in the Oyster River Watershed and results of the

award determination.

4.) Attachment D: Approved Quality Assurance Project Plan

Budget Expenditures:

A summary of grant expenditures are provided in the expense summary table on the next page. Total

budget expenditures for this project are complete and generally in line with projected costs in the initial

proposal. One notable exception is the commitment of $4,841.89 to additional staff time ($2,578.85

Fringe Benefits). This was offset by savings for contractual publication and graphics services anticipated

in the original proposal which were completed in-house as opposed to being hired out. As it stands the

reallocation of $7,420.74 from contractual and travel to personnel accounts for only 5.4% of the overall

budget for the project of $136,218.

jjhoule

Typewritten Text

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4

Environmental results:

P2 Efforts a. Hazardous materials reduced (lbs/yr)

b. MTCO2e

Per year c. Millions of

gallons of water infiltrated per

year

d. Millions of dollars in economic savings to

businesses and municipalities ($/yr) over a

30 year implementation period

Number of Municipalities implementing updated stormwater standards

Projections assume 7*

Full Watershed Projections

assume 42**



assume 42**



assume 42**

Projections assume 7* Full Watershed Projections

assume 42**

Quantification of updated Stormwater standards

TSS 4,905

1.74 6.79 $455,170 TP 14.9

TN 163

Outreach and Education**

TSS 136,402 52.3 204.3 $8,000,000 TP 395.2

TN 5,984 * Project targeted and assisted with implementation in 2 communities in the Oyster River Watershed however modeled estimates were generated for all 7 municipalities in the watershed (Barrington, Dover, Durham, Lee, Madbury, Nottingham, and UNH). ** Assumes full implementation throughout the 42 Great Bay communities in NH over a 30 year implementation period

jjhoule

Typewritten Text

Attachment A: Final modeling results report

Technical Report on Modeling Results

Modeling the Effect of Local Stormw ater

Regulat ions on Future Pollutant Loads in

the Oyster River Watershed

Prepared by: University of New Hampshire

Stormwater Center

and

Vanasse Hangen Brustlin, Inc.

Bedford, New Hampshire

With Assistance from:

Strafford Regional Planning Commission

Rochester, New Hampshire

FINAL REPORT

December 16, 2015

University of New Hampshire

Stormwater Center

ii Table of Contents

Table of Contents

Executive Summary…………………………………………………………………………………………ii

1.0 Introduction .......................................................................................................................... ii

2.0 Existing Watershed Conditions ................................................................................... 3

2.1. Review of Historical Impervious Cover Growth .............................................................. 3 2.2 Historical Population Growth .......................................................................................... 3

3.0 Study Approach ................................................................................................................. 5

3.1 Future Population Growth in the Watershed .................................................................. 5 3.2 Future Impervious Cover (IC) Area Growth ................................................................... 5

3.2.1 Future Impervious Cover Growth Related to Residential Development….……6

3.2.2. Future Impervious Cover Growth Related to Commercial Development……..6 3.3. Future Pollutant Loads ................................................................................................... 8 3.4. Potential Stormwater Treatment Effects Resulting from Stormwater Regulations ......... 9

3.5 Estimated Effect on Redevelopment Projects…………………………………………….12

4.0 Results ................................................................................................................................. 13

4.1 Future Population Growth Estimates ........................................................................... 13 4.2 Future Impervious Cover Area Growth Related to Residential Development ............. 13 4.3. Futue Impervious Cover Growth Related to Commercial/Industrial Development ....... 14 4.4 Future Pollutant Loads with and without Stormwater Regulations............................... 15

4.5 Estimated Effect of Proposed Regulations on Future Redevelopment Projects………17

5.0 Discussion ............................................................................................................. 19

6.0 References .............................................................................................................. 21


Stormwater Center

ii Executive Summary

Executive Summary

The goal of this study was to evaluate the net effect that enhanced local stormwater regulations could have on

minimizing the pollutant load increases from future development and redevelopment in the Oyster River watershed.

As future development and land use changes are inevitable, early adoption of enhanced local stormwater regulations

provides the greatest opportunity to minimize increased pollutant loading. Model stormwater regulations developed

for the Southeast Watershed Alliance (SWA) in December 2012 provide a template for enhanced stormwater

regulations that address future development and redevelopment projects (SWA 2012). The regulations would apply to

new development and redevelopment projects that are subject to site plan and/or subdivision review by the Planning

Board. This would include most commercial or mixed use development projects and residential multi-family or

subdivision projects.

The SWA model regulations advocate a “green infrastructure” for mitigating the negative effects associated with

increasing development and expanding areas of IC. The adoption of ordinances and regulations mandate the use of

stormwater filtration and infiltration practices for reducing runoff and requirements for improved stormwater controls

for reducing runoff with redevelopment or other significant improvements such as repaving or building renovations.

This report describes the methods, assumptions and findings of the modeling effort used to predict future increases in

impervious areas and pollutant loads related to the forecasted future development. The Simple Method model as

described in the NH Department of Environmental Services (NHDES) Stormwater Manual was used to predict future

pollutant load increases as a result of potential increases in impervious cover. The pollutants evaluated in this study

include total suspended solids (TSS), total phosphorus (TP) and total nitrogen (TN). This study focused solely on

estimating the future pollutant load contributions from potential changes in impervious cover associated with

residential and commercial activity. This study did not evaluate or quantify the potential added pollutant loads

associated with septic systems and increased lawn fertilizer or other significant source of non-point source (NPS) of

pollution.

Based on the study approach, approximately 500 acres of additional impervious cover (IC) area could be developed in

the Oyster River watershed by the year 2040. This represents a 40 percent increase over the 1,290 acres of IC area

estimated to exist in the watershed based on 2010 aerial imagery. This added IC area is estimated to increase the

average annual pollutant loads for Total Suspended Solids (TSS), Total Phosphorus (TP) and Total Nitrogen (TN) by

approximately 217,700, 1,060 and 9,950 pounds, respectively, if no local stormwater regulations are adopted and no

enhanced stormwater management was provided. The level of stormwater management assumed to be required by

the local regulations could reduce the future average annual pollutant loads by approximately 40 to 70 percent

depending on the pollutant and would potentially prevent the discharge of approximately 147,145 pounds (~74 tons),

450 pounds and 4,900 pounds for TSS, TP and TN, respectively, from entering the Oyster River and Great Bay receiving

waters. This would result in substantial water quality benefits compared to having no standard or an out-date

standard. For nitrogen alone, more than half of the predicted future annual load attributed to new IC area could be

reduced by providing enhanced stormwater treatment.

Approximately 70 acres or 25 percent of the existing commercial and industrial IC area in the watershed was also

assumed to be redeveloped by 2040 and also be subject to the new regulations. If 50 percent of this redeveloped IC

area was treated it would reduce existing pollutant load contributions by 18,500, 50 and 495 pounds for TSS, TP and

TN, respectively, on an average annual basis.


Stormwater Center

iii Executive Summary

Not only would early and widespread adoption of the proposed local regulations result in substantial pollutant load

reductions but could also result in substantial financial benefits for each community by avoiding or minimizing the

potential deferred future costs of having to retroactively implement stormwater BMP retrofits to achieve equivalent

pollutant load reductions. To retroactively treat the estimated future IC area (i.e., 386 acres) plus the estimated 70

acres of existing IC area that might be redeveloped would cost approximately $14 million in 2014 dollars using an

average retrofit cost of $30,000 per acre. These estimated future costs do not include the cost of inflation nor the

added potential cost of lost or diminished ecological services and/or recreational uses as a result of decreased water

quality conditions.

If the potential savings in deferred costs or cost avoidance gained through early adoption of stormwater regulations

and enhanced treatment were extended beyond the Oyster River watershed to include the entire Great Bay

watershed, the potential future cost savings could be in the hundreds of millions of dollars.

The findings of this analysis clearly demonstrate that adopting local stormwater regulations to require more stringent

stormwater treatment standards could have a tremendous positive impact in minimizing and preventing the additional

future pollutant loads that would be discharged in the Great Bay estuary. This would significantly alter the current

trajectory of declining water quality conditions. The results of this study provide the initial framework for establishing

pollutant load reduction credits for early adoption and maintaining strict adherence to enhanced local stormwater

regulations as it relates to future development and redevelopment activity in the watershed. This could provide an

incentive for Towns to engage early in the protection and restoration of the water quality conditions in the Great Bay

estuary and perhaps assist regulated MS4 communities in addressing increasing federal permit requirements.


Stormwater Center

1 Introduction

1.0 Introduction

Municipalities and private landowners are likely to face a growing economic liability involved with meeting future

stormwater management and Clean Water Act obligations. As the list of impaired water bodies continues to grow,

state and federal regulators are imposing more stringent requirements on regulated communities and private

landowners in order to restore and/or meet water quality objectives. This is evident in the proposed new requirements

contained in the 2013 DRAFT MS4 Stormwater General Permit for New Hampshire where communities will be required

to adopt stricter post-construction stormwater regulations to ensure new development activity will not result in further

degradation to impaired waters as well as initiate the use of stormwater retrofit measures on municipally-owned

properties to reduce existing pollutant loads. In the NH Seacoast Region, restoring and preventing further water

quality degradation to the Great Bay Estuary and its tributaries is critically important as the Estuary represents a major

ecological and economic resource in the region and is currently listed as impaired due to declining water quality as

indicated by long-term monitoring. The decline in water quality is largely attributed to previous development and land

use changes in the watershed (NHDES 2014).

As future development and land use changes are inevitable, early adoption of enhanced local stormwater regulations

provides the greatest opportunity to minimize increased pollutant loading from future development. Model

stormwater regulations developed for the Southeast Watershed Alliance (SWA) in December 2012 provide a template

for enhanced stormwater regulations that address future development and redevelopment projects (SWA 2012). The

regulations would apply to new development and redevelopment projects that are subject to site plan and/or

subdivision review by the Planning Board. This would include most commercial or mixed use development projects and

residential multi-family or subdivision projects. Performance standards generally include runoff reduction, use of low

impact development measures and enhanced stormwater filtration and infiltration controls.

The primary goal of this study was to evaluate the net effect that enhanced local stormwater regulations could have on

minimizing future pollutant load increases in the Oyster River watershed. The Oyster River watershed is one of several

major tributaries to the Great Bay and contains portions of six towns including Barrington, Dover, Durham, Lee,

Madbury and Nottingham as well as the University of New Hampshire (UNH) Durham Campus area. This particular

watershed was selected for study because the results of a larger modeling effort recently completed for the watershed

that estimated total nitrogen loads from existing nonpoint sources allows for a comparison of baseline conditions, at

least for nitrogen, to help assess how future projected pollutant loads from impervious surfaces compare to existing

estimated loads within the watershed (VHB, 2014). The following consists of the primary goals of this study:

1) To estimate the future pollutant loading that may result from future development activity,

2) To estimate the potential load reductions that may result by adopting enhanced stormwater regulations,

3) To estimate the potential deferred costs that communities may face if local regulations are not adopted and the

same pollutant load reductions need to be achieved in the future due to either state and federal regulations

updates that require regulated communities to install retrofit measures to address increased pollutant loads.

This project was led by the UNH Stormwater Center with assistance from the Strafford Regional Planning Commission

(SRPC). This report describes the methods, assumptions and findings of the modeling effort used to predict future

increases in impervious areas and pollutant loads related to the forecasted future development. It is important to

point out that this study focused solely on future pollutant load contributions from potential changes in impervious

cover associated with future residential and commercial development activity. This study did not evaluate or quantify


Stormwater Center

2 Introduction

the potential added pollutant loads associated with septic systems and increased lawn fertilizer or other significant

source of NPS pollution.

Although this study focused solely on the Oyster River Watershed, the results of this analysis could be extrapolated to

the entire Great Bay Estuary watershed, which is a 1,000 square mile region that includes much of southern NH and

Maine. This area is one of the fastest growing regions in northern New England. Recently, the New Hampshire

Department of Environmental Services (DES) completed a modeling effort to estimate the non-point source nitrogen

loads from each of the nine major watersheds draining to the Great Bay Estuary or the Hampton-Seabrook Estuary.

The results of this larger study allows regulators, municipal planners and other stakeholders to prioritize future efforts

to manage and control existing and future pollutant loads from nonpoint sources (NHDES 2014),

Various models and predictive tools are available that estimate increases in pollutant loads as a result of future

impervious cover changes. For this study, the Simple Method model as described in the NH Department of

Environmental Services (NHDES) Stormwater Manual was used to predict future pollutant load increases as a result of

potential increases in impervious cover. The pollutants evaluated in this study include total suspended solids (TSS),

total phosphorus (TP) and total nitrogen (TN).

Early adoption of these regulations not only affords the best advantage of limiting additional pollutant loading but also

could result in substantial cost savings for communities by minimizing the potential future costs involved with

implementing stormwater retrofit measures to treat developed areas that could be needed to comply with future

regulations or meet possible load allocations established by a future Total Maximum Daily Load (TMDL) Study. The

costs to retroactively restore water quality conditions through stormwater retrofits are generally much higher than the

initial costs of installing treatment measures at the onset of development. Use of retrofit measures to reduce pollutant

loads from existing developed areas is a critical aspect of this research approach and is already occurring in several

urbanized watersheds within the Northeast region. Key examples include the Long Creek watershed (ME), in the

Charles River Watershed (MA), in the Buzzards Bay Watershed (MA), and in the Long Island Sound Watershed (NY).


Stormwater Center

3 Methods and Assumptions

2.0 Existing Watershed Conditions

2.1. Review of Historical Impervious Cover Growth

Table 2.1 provides a summary of the historical changes in impervious cover (IC) over the last 20 years or since 1990

based on IC estimates generated by the Piscataqua Region Estuaries Partnership (PREP) in collaboration with NH

GRANIT (UNH Complex Systems 2010). It is important to note that the historical IC data prior to 2010 was based

on lower resolution (30 meter pixel) satellite imagery. Starting in 2010, higher resolution (1-meter pixel) imagery

became available. The higher resolution aerial imagery provides a more accurate depiction of the IC area and

yields considerably different estimates of IC area than that generated from the older lower resolution data. The

lower resolution data generally produces as much 40 percent higher estimates of IC area compared to the high

resolution data. The high resolution imagery, however, is not available yet for all of southern New Hampshire.

To allow for a historical analysis of IC growth over the last 20 years, the lower resolution data was used to provide

a relative comparison of IC changes over time. Using the same analytical methods and aerial imagery resolution,

the total amount of IC area in the watershed is estimated to have increased by 1,160 acres or by approximately

123 percent from 1990 to 2010. The largest increases occurred in Durham where an estimated 537 acres of

additional IC area were created over the 20 year period followed by an additional 263 acres of IC area created in

the Town of Lee. Much of the recent IC area growth in Lee appears to be due to commercial development.

Table 2.1: Summary of Total Town Area, Town Area and Historical Changes in Impervious Area in the Watershed

Notes: Based on Piscataqua Region Estuaries Partnership data and analysis using low resolution aerial photography. UNH related

data not assessed.

2.2 Historical Population Growth

Table 2.2 provides a summary of the historical population growth within each community over the last 50 years.

The net change both in number and percentage over the past 30 years or since 1980 provides a basis to compare

future projections over the next 30 years as discussed herein. The estimated future population growth pertains

only to the portion of each community that is within the watershed. As of 2010, approximately 22,230 people or

38 percent of the total 2010 population within the six (6) communities is estimated to reside in the watershed.

Durham residents make up approximately 62 percent of the total watershed population while residents in Dover

and Lee each comprise a little more than 10 percent of the watershed population. Barrington and Madbury

residents are estimated to each make up 5 percent of the watershed population.

Town

Total Town Area

(acres)

Town Area in the

Watershed (ac)

Percent of Town Area

in the Watershed

Estimated Total IC Area (ac) Town-wide*

20-year Change in IC Area 1990-

2010 (acres) % Change 1990-2010 1990 2000 2010

Barrington 31,117 2,891 9.3% 70 102 160 90 130%

Dover 18,592 885 5.0% 95 154 221 125 131%

Durham 15,852 7,758 49.0% 523 763 1,061 537 103%

Lee 12,928 4,620 35.7% 160 266 423 263 164%

Madbury 7,779 3,173 40.8% 88 136 210 121 137%

Nottingham 30,997 316 1.0% 9 13 32 22 242%

117,265 19,643 946 1,433 2,105 1,160 123%


Stormwater Center

4 Methods and Assumptions

Table 2.2: Historical Population Growth Statistics1 for Communities in the Oyster River Watershed: 1960 to 2010

Notes: 1Population change data compiled by the NH Office of Energy and Planning dated March 2011 and based on US Census Bureau Data. 2The population within the watershed was estimated based on a ratio of the amount of town area within the watershed area to total area for each community multiplied by the total population. Note: UNH related data not assessed independently.

Figure 2.1 illustrates the disparity between the rate of IC area growth relative to the population growth in the

watershed between 1990 and 2010. The amount of IC area in the watershed is disproportionate to population

growth; where population increased by 25 percent, IC increased over the corresponding time period by 123

percent. This could have major implications for water quality conditions within the watershed, especially if the

stormwater runoff from these IC areas is left untreated. It is interesting to note that on a town-wide basis, the

largest percentage increases in population occurred in the Towns of Barrington and Nottingham, located in the

upper headwater regions of the watershed. The continued development pressures in these Towns places greater

emphasis on the need for enhanced stormwater regulations. The Town of Lee, in contrast, had the lowest percent

increase in population growth but still had substantial gains in IC area most likely due to commercial development

in the Route 125 and Route 4 corridors. This trend also heightens the importance of local stormwater regulations

as well.

Figure 2.1: Estimated Percent Increase in Population and IC area in the Oyster River Watershed for Years 1990 to 2010.

Town 1960 1970 1980 1990 2000 2010

20-year Change

1990-2010 % Change 1990-2010

Population in

Watershed

Barrington 1,036 1,865 4,404 6,164 7,475 8,576 2,412 39% 1,651 Dover 19,131 20,850 22,377 25,042 26,884 29,987 4,945 20% 2,764

Durham 5,504 8,869 10,652 11,818 12,664 14,638 2,820 24% 13,802 Lee 931 1,481 2,111 3,729 4,145 4,330 601 16% 2,369

Madbury 556 704 987 1,404 1,509 1,771 367 26% 1,209 Nottingham 623 952 1,952 2,939 3,701 4,785 1,846 63% 437

27,158 33,769 40,531 48,157 52,677 59,302 12,991 25% 22,232


Stormwater Center

5 Results

3.0 Study Approach

The following describes the methods, data sources, and various assumptions used to develop prediction of future

impervious cover changes and related pollutant loads. The approach involved the following four major steps:

1. Estimate the Future Population Growth within the Watershed based on Population Growth Projections

2. Estimate the Potential Increases in Impervious Cover (IC) Area due to Future Residential and Commercial

Development

3. Estimate the Potential Increase in Future Pollutant Loads Resulting from the Projected New IC Area

4. Estimate the Amount of Future IC Area that will be Subject to the Enhanced Stormwater Regulations and the

Potential Effect on Future Pollutant Loads due to Stormwater Treatment

3.1 Future Population Growth in the Watershed

Future population growth estimates for each watershed community were provided by the Strafford Regional Planning

Commission (SRPC) going out to years 2025 and 2040. These projections were originally developed for the entire state

by the NH Office of Energy and Planning in March 2011. The population growth projections were initially developed at

the County level using Census data and historical population growth trends. The County level projections were then

distributed to the individual Towns based on historic trends of the Town’s share of the County population. For this

analysis, the future population growth estimates represent 15 and 30 year projections using 2010 as the baseline. The

2010 town-wide population for each community was adjusted on an area-weighted basis to account for the portion of

the Town within the watershed and to estimate the population that resides within the Oyster River watershed.

3.2 Future Impervious Cover (IC) Area Growth

The first step to predicting future impervious cover (IC) increases lies in estimating how much residential and

commercial development is likely to occur over the next 15 and 30 years. The assumptions used to predict future

residential and commercial development activity are discussed in greater detail in the following sections. The resulting

amount of associated with the future residential and commercial development activity was based primarily on existing

IC area ratios for both the residentially and commercially zoned areas multiplied by the amount of future development

expected to occur in these zones. Recognizing that this approach does not account for all the potential socio-economic

factors that will influence future development such as land costs and accessibility along transportation corridors, this

approach relied on various conservative assumptions to estimate the future residential and commercial development.

3.2.1. Future Growth in Residential IC Area

Future increases in IC area due to residential development were estimated using future population growth estimates

within each community and the existing IC area per capita ratio calculated for each community. Table 3.1 presents a

breakdown of the total town area, the amount of town area within the watershed, the estimated 2010 population that

lives within the watershed and the estimated total IC area for residentially zoned areas in each community. The total IC

area consists of buildings, walkways, driveways and roads within the residentially-zoned areas and generally excludes

the commercial IC areas. In mixed use zones, both the commercial and residential IC area may be included, however,

this is not a common occurrence and thus was not considered to be a significant factor materially contributing to the

overall results. The total IC area is then divided by the population to derive an IC area per capita ratio. This ratio

provides the basis for projecting the future increase in IC area based on the population growth estimates. In other


Stormwater Center

6 Results

words, the future population growth is assumed to generate the same proportional amount of IC area per person as

that that currently exists within the residential zoned areas.

Table 3.1: Summary of Town Area, Area within the Watershed, 2010 Population and 2010 IC Area in Each Community

The general locations and distribution of future residential development and IC growth was assumed to be similar to

the previous development patterns. In other words, the proportion of the future population that will reside within a

particular residential zone relative to the total population within the community will likely be similar to the existing

population that resides in that zone. In reality, it is likely that the locations and rate of future population and IC growth

may differ somewhat from the past.

3.2.2. Future Impervious Cover Growth Related to Commercial Development

The amount of new IC area that will be created due to future commercial development was estimated differently since

it is not tied directly to population growth. Instead, the projected amount of future commercial development was

based on a review of previous commercial development trends, the availability of existing, undeveloped, commercially

zoned, parcels within each community, the anticipated development goals and/or plans as described in master plan

documents and discussions with planning officials in each of the communities.

For purposes of this study, it was assumed that 20 percent of the available, buildable commercially zoned land (i.e., less

constrained land) would be developed for commercial or industrial purposes over the next 30 years or by the year

2040. This is generally considered to be a conservative commercial development rate representing less than 1 percent

average annual growth over the next 30 years. The only exception to this assumption was in Dover, where it was

assumed that 75 percent of the available, buildable commercially-zoned land would be developed over the next 30

years. The reason for this change relates to the fact that much of the available commercial area in Dover is located in a

heavily developed commercial area along Mast Road and this area has experienced uptick in commercial development

activity which is likely to continue in the immediate future. These assumptions were verified and supported through

direct interviews conducted with all watershed communities. The Strafford Regional Planning Commission (SRPC)

consulted with planning officials within the watershed communities as well as reviewed available master plans, where

available, to identify parcels or areas within commercially-zoned areas that are targeted or have higher development

potential for commercial development.

Table 3.2 provides a summary of the estimated amount of land currently developed for commercial and industrial uses,

the existing amount commercial or industrial IC area and the amount of commercially or industrially zoned land that is

available for development within each community.

Town

Total Town Area

(acres)

Town Area in the Watershed

(ac)

2010 Population in

Watershed

2010 IC Area in Watershed

(ac)

Existing IC Area per Capita

Barrington 31,117 2,891 1,651 82 0.05 Dover 18,592 885 2,764 125 0.04

Durham 14,552 6,572 6,219 248 0.12 UNH 1,300 1,185 7,582 493 0.03 Lee 12,928 4,620 2,381 220 0.05

Madbury 7,779 3,173 1,209 109 0.08 Nottingham 30,997 316 437 17 0.04

117,265 19,643 22,229 1,293


Stormwater Center

7 Results

Approximately 500 acres or just under 3 percent of the total watershed area is currently mapped as developed for

commercial and/or industrial uses. These developed areas contain approximately 280 acres of IC area, which

represents approximately 22 percent of the total IC area in the watershed. Durham and UNH have the bulk of the

existing commercially developed area in the watershed, which is primarily related to the downtown area and the UNH

campus. Dover and Lee have the second and third highest amount of existing commercially or industrially developed

area, respectively. Barrington, which has a limited amount of existing commercial or industrial development, also has a

relatively large amount of commercially zoned land along Routes 4 and 125, which is likely to have strong commercial

development potential in the immediate future.

Table 3.2: Summary of Commercially-Zoned Land, Existing Developed and Impervious Cover Areas (ac) as well as the

Available Undeveloped Commercial Land Area for Future Development within the Watershed and Each Town

Town

Existing

Commercial &

Industrial

Developed

Land (acres)

Existing

Comm. &

Industrial

IC Area

(acres)

Existing Ratio of

Commercial IC

Area to

Commercial

Developed Lot

Commercially Zoned

Land Area Available

for Development/Re-

development (acres)1

Available Commercially

Zoned Land less Exist

Development &

Constrained land

(acres)2

Estimated Future

Commercial or

Industrial Developed

Area based on 20% of

Available Area Being

Developed (acres)

Barrington 8 4 0.5 387 290 58

Dover 76 32 0.4 187 100 74

Durham 120 87 0.7 720 520 104

UNH 123 94 0.8 600 540 108

Lee 140 55 0.4 315 230 47

Madbury 34 7 0.2 150 120 24

Nottingham 0 0 -- 20 20 4

Total 501 279 2,380 1,800 415 Notes: 1Commercial zoned areas include high density mixed-use areas in Durham and UNH Campus. 2Avaliable undeveloped, commercially zoned area excludes constrained lands (i.e., wetlands, surface water, steep slopes) and existing developed areas including residential, commercial and NHDOT right-of-way.

Assuming that 20 percent of the available and buildable, commercial or industrial zoned land in each community is

developed by 2040, another 415 acres of commercial and/or industrial land would be developed in the watershed. This

projected amount of future commercial development within each community compares favorably with the amount of

commercially zoned property identified by the SRPC planners as having high development potential or being targeted

for development by municipal officials. For instance, in Barrington, SRPC planners identified several, commercially-

zoned parcels comprising a total area of sixty (60) acres that are located along Route 4 west of the traffic circle and

amongst currently developed commercial uses as being targeted for future commercial development. One of the

parcels, which consists of approximately 24 acres is set back from Route 4 but as has right-of way access to Route 4. In

the town of Madbury, SRPC planners identified several commercially-zoned parcels consisting of nearly depleted,

gravel pits along Route 155 (aka Knox Marsh Road) near the Dover town boundary as having high future commercial

development. One parcel is approximately 92 acres in size and is currently used as a materials recycling facility that

apparently has plans to expand based on SRPC’s review.

In Lee, SRPC Planners identified several commercially-zoned parcels located around Routes 125 and Lee Traffic Circle

that comprise approximately 55 acres with high commercial development or redevelopment potential based on

conversations with municipal officials. This is very close to the estimated 47 acres of future commercial development

using the assumption of 20 percent of the available and undeveloped commercially-zoned land would be developed in

the next 30 years. Most of these areas are along the major transportation corridors, which is consistent with recent


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8 Results

development trends. The region as a whole represents a rapidly growing area and given the major transportation

routes within the watershed and the increased level of commuting along these routes, the recent development in

commercial services are likely to continue into the foreseeable future. Market forces and economic conditions are also

likely to influence the rate and type of commercial development as they are highly variable and cyclical.

Durham and UNH have seen a sharp rise in the commercial development activity in recent years. The Town of Durham,

in particular, has seen a substantial amount of development and redevelopment activity associated with several major

student housing projects. It is difficult to predict whether this activity will continue long-term into the future.

The 2012 UNH Campus Master Plan also provides a general forecast of the potential development and redevelopment

activity planned for the UNH campus for the next 20 years. The Master Plan identifies as many as forty (40) different

renovation/redevelopment projects for existing campus buildings and facilities that are targeted for completion over

the next 20 years. The total building footprint area associated with all of these projects adds up to approximately 12 to

14 acres with more than half of this area comprised of existing building footprint. The largest project area is associated

with the proposed renovations to the existing Field House facility consisting of approximately 2.5 acres. The Master

Plan also includes several transportation and parking area improvements as well as a new roadway extending behind

the Athletic fields connecting to the west side of campus and tying into Route 155a. These improvements are likely to

add several more acres of impervious area associated with development or redevelopment activity.

The amount of new IC area that will likely be created as a result of the future commercial development activity was

estimated based on the current ratio of commercial IC area to commercially developed area within the current

commercially zoned areas in each community using the 2010 high resolution GIS data. In general, the total IC area

including in the commercial zone excludes residential related IC area to avoid double-counting of areas. The estimated

amount of commercial IC area projected to result from this development is presented in Section 4.3.

3.3. Future Pollutant Loads

Estimating future pollutant loads as a result of the projected increases in IC area attributable to future residential and

commercial development was based on the use of the Simple Method model as published in DES’ Stormwater Manual.

The Simple Method model is widely used throughout the country to estimate relative pollutant load contributions from

various land uses and stormwater treatment options. The model estimates average annual pollutant loads based on

representative Event Mean Concentrations (EMCs) for each land use and the average annual runoff volume generated

accounting for varying levels of imperviousness. Table 2-1 presents typical event-mean concentrations for common

stormwater derived pollutants including total suspended solids (TSS), total phosphorus (TP) and total nitrogen (TN).

Table 3.2: Typical Event-Mean Concentrations for Stormwater Related Pollutants

The typical EMC’s for the selected pollutants are then converted to average annual load rates for each land use using

Equations 1 and 2 to calculate the average annual runoff volume based on an average rainfall depth and average

percent imperviousness for each land use.

Land Use TSS (mg/L) TP (mg/L) TN (mg/L)

Residential 85 0.52 5.15

Commercial 77 0.33 2.97

Notes: NHDES Stormwater Manual, Volume 1, Appendix D.


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9 Results

Equation 1: R = P * Pj * Rv (Annual Runoff Volume)

Where: R = Annual runoff (inches) P = Annual rainfall (inches) 48 Pj = Fraction of annual rainfall events that produce runoff 0.9

Rv = Runoff volume coefficient (based on Equation 2 below)

Equation 2: Rv = 0.05+0.9(Ia)

Where:

Ia = typical % Impervious area for each land use type

Equation 3 is then used to calculate the average annual load.

Equation 3: Li = 0.226 * R * C * A (Annual Pollutant Load)

Where:

Li = Annual load (lbs)

R = Annual runoff (inches)

C = Pollutant concentration (mg/l)

A = Area (acres)

0.226 = Unit conversion factor

Table 3.2 provides a summary of the estimated pollutant loading rates (lbs/acre/year) for general residential and

commercial land uses and pollutants of concern using the equations above. The difference in pollutant load rates

between the residential and commercial land uses is due in large part to the difference in the predicted average annual

runoff volumes, which is a primary function of the percent imperviousness between the two land uses. For this

analysis, it was assumed the commercial and residential land uses have typical percent imperviousness of 85 and 30

percent, respectively, which is consistent with values contained in the TR-55 methodology that is often used to

estimate potential runoff volumes generated from land cover changes as part of site design. The percent

imperviousness values are likely to vary considerably based on actual conditions throughout the watershed.

Table 3.2: Estimated Average Annual Pollutant Loads for Each Acre of Commercial and Residential IC Area

Land Use TSS (lbs/yr/acre) TP (lbs/yr/acre) TN (lbs/yr/acre)

Residential 191 1.2 11.6

Commercial 579 2.5 22.3 Note: The average annual pollutant load rates are based on Event Mean Concentrations (EMCs) published in the NHDES Stormwater Manual and

assumed average % impervious or (Ia value) of 0.20 and 0.80 for residential and commercial land uses, respectively. The Ia value or % impervious could vary considerably within each town and within various locations within the watershed.

3.4. Potential Stormwater Treatment Effects Resulting from the New Stormwater Regulations

The amount of new IC area that may be subject to the new stormwater regulations and treatment requirements will

depend on a wide variety of factors. First and foremost, much depends on how soon communities adopt the new

regulations and what size and type of development are used as applicability thresholds to trigger Planning Board

review and compliance. In most cases, any future project that triggers site plan and/or subdivision review before


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10 Results

Planning Board would also generally be required to comply with the new stormwater treatment requirements. This

would include most, if not all, future commercial development, mixed-use development and residential subdivision

projects. Redevelopment of existing commercial and mixed-use properties, in most cases, would also be subject to the

new regulations depending on the applicability thresholds included in the regulations and whether any potential

exemptions would be allowed for. Single family home development on existing lots are not typically subject to

Planning Board review and, thus, were not included in this analysis.

The extent to which future residential development will occur as single-family home development as opposed to new

subdivisions or multi-family development will vary considerably between towns. For purposes of this analysis, it was

generally assumed that in the more rural towns, such as Barrington, Lee, Madbury and Nottingham, the future

residential development will likely occur as a 50:50 split between single-family, single lot development and subdivisions

or multi-family development with the latter being subject to new regulations. In these more rural towns, there is

greater likelihood that there are still some existing residential lots available for single family home construction as

compared to the more developed and built-out towns.

For the more densely developed towns, like Durham and Dover, it was assumed that 80 percent of the future

residential development will occur as new subdivisions or as multi-family development and these types of

developments would be subject to the proposed regulations. A review of building permit approvals in Durham over the

past seven years supports this assumption (see Table 3.3).

Table 3.3: Summary of Building Permit Approvals in Durham, NH from 2007 to 2013.

Year Total Single

Family Permits

Multi-Family or Subdivisions

Permits Annual Total

% of Annual Total

2013 19 137 156 88 %

2012 4 22 26 85 %

2011 56 111 167 66 %

2010 6 7 13 54 %

2009 5 94 99 95 %

2008 2 56 58 97 %

2007 3 4 7 57 %

Average Annual % of Building Permits as Multi-Family Projects or Subdivisions 80 %

Source: Durham Annual Town Reports: Code Enforcement Annual Summary

For commercial development, it was generally assumed that 80 percent of the future projects would be subject to the

new regulations. Although most all commercial projects are generally subject Planning Board approval because they

typically trigger Site Plan and/or Subdivision review, the applicability threshold used to require compliance with the

higher performance standards for stormwater management may vary by community and may depend on the

preferences of each community and whether exemptions are allowed for smaller projects and/or redevelopment

projects. The model SWA ordinance indicates the threshold to trigger compliance should be 5,000 square feet of

disturbance. However, adoption of the standard across individual communities reveals that thresholds can range from

5,000 to 20,000 square feet of proposed soil disturbance activity. Applicability thresholds can also be based on the

proposed amount of IC area which often is similar to the amount of proposed disturbed area but depends on the type

of development. A lower threshold will capture a higher percentage of projects.

Table 3.4 provides a summary breakdown of the current amount of IC area that exists on commercial properties within

the watershed based on a geospatial analysis of IC area on existing commercial properties. Using the IC area as a


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11 Results

surrogate for level of disturbance or an applicability threshold for projects that would be required to meet the

proposed stormwater regulations suggests that a threshold of 5,000 square feet would likely capture eighty (80)

percent of the future commercial development. A higher disturbance threshold of 10,000 sq. ft. would result in only 60

percent of future commercial development potentially subject to the proposed regulations if existing commercial

properties are indicative of the future development proposals.

Table 3.4: Percent of Commercial Properties Likely to be Subject to Regulations Based on Various Disturbance Thresholds

Used to Trigger Compliance with New Regulations

Recommended Disturbance Threshold (sq. ft.)

Estimated Percent of Commercial Projects\ Subject

to New Regulations

5,000 80 %

10,000 60 %

20,000 50 %

40,000 30 %

Figures 3.1 and 3.2 present a more detailed distribution of the amount of IC area that currently exists on commercial

parcels in Durham. Figure 3.1, which includes all commercial parcels, indicates that more than 95 % of the larger

commercial lots in Durham and Dover have less than 500,000 sq. ft. of IC area. Seventy percent of the existing parcels

have less than 40,000 sq. ft. of IC area. Figure 3.2 shows a frequency distribution of IC area for parcels with less than

30, 000 sq. ft. of IC area which is close to 62 percent of the total amount of commercial parcels in Durham and Dover.

This evaluation of the amount of IC area on existing parcels indicates that most commercial parcels have a relatively

small amount of IC area on a parcel by parcel basis.

Figure 3.1: Probability distributions for commercial properties in Durham

3.5. Estimated Effect on Potential Redevelopment Projects

The proposed regulations would promote better stormwater management and water quality treatment for future

redevelopment projects. Enhanced stormwater treatment on future redevelopment projects actually has the


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12 Results

advantage of lowering baseline pollutant loads associated with existing IC area rather than just limiting future

increases. As such, the potential impact of the regulations on future redevelopment projects is equally, if not, more

important as addressing future development. Because the redevelopment affects existing pollutant loads, the

potential load reductions were estimated separately from the future pollutant load increases related to new

development projects. The amount and potential location of redevelopment can be highly variable and will depend on

a wide range of site-specific conditions and constraints. For the purposes of this study, it was generally assumed that

25 percent of the existing commercially developed IC area in each Town would be redeveloped over the next 30 years.

The amount of redevelopment could obviously be higher and lower within each community and will be driven more

by market trends and economic conditions but this general assumption provides a reasonable basis for evaluating the

relative effect of the proposed local regulations on redevelopment. Since there is greater potential for various site

constraints to limit the amount of IC area that can be treated with stormwater BMPs when dealing with existing

developed sites, it was assumed that only 50 percent of this estimated redeveloped IC area would be treated by

stormwater BMPs. This is consistent with the recommended level of treatment for redevelopment projects included

in the SWA model ordinance.


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13 Results

4.0 Results

4.1 Future Population Growth Estimates

Table 4.1 presents population growth estimates for portions of each community that are within the watershed going

out to years 2025 and 2040. By 2025, approximately 2,400 more people are estimated to reside in the watershed

resulting an 11 percent increase over the current population. By 2040, another 3,400 more people are estimated to

live in the watershed representing a 26 percent increase over the 2010 population. Durham is expected to see the

largest increase with an additional 4,000 people predicted to live in the watershed portion of Town, which includes the

UNH Campus. In Dover, approximately 600 more people are projected to live in the watershed and approximately 500

more people are projected to live in the Barrington portion of the watershed. Within the watershed portions of Lee,

Madbury and Nottingham, less than 700 people are expected to be added by 2040. The future population estimates

appear to reflect a slower growth rate than what has occurred historically given that the watershed population

increased by approximately 25 percent in the 20 years between 1990 and 2010.

Table 4.1: Population Growth Estimates for Municipal Areas within the Oyster River Watershed

Town

Estimated Future Population Growth in the Watershed Over the Next 15 and 30 years

Projected Percent Change 2010-40 2010 2025 2040

Barrington 1,651 1,836 2,105 27 %

Dover 2,764 2,993 3,358 22 %

Durham 13,802 15,452 17,804 29 %

Lee 2,369 2,397 2,534 7 %

Madbury 1,209 1,372 1,597 24 %

Nottingham 437 546 669 53 %

Total 22,232 24,596 28,067 26%

Net Increase 2,364 5,835 Note: Population estimates are generated at the county level by the NHOEP and then distributed amongst the various towns based on the town/city population’s current share of the total County population for the year 2010 (SF 100% data). For instance in 2000, Lee’s population accounted for

approximately 3.7% of the total Strafford County population but, in 2010, its share of the county population declined to 3.5 percent indicating a shift of approximately -.2 percent. Thus, limited population growth is projected for the Town of Lee for the next 15 years.

4.2 Impervious Cover Area Growth Related to Future Residential Development

Table 4.2 presents a summary of the projected amount of additional IC area that is expected to result from future

residential development in each town. As described earlier, these estimates are based on the anticipated population

growth in each community and the current IC area per capita ratio for the residential areas in each town.

The results of this approach and the inherent assumptions indicate that approximately 185 and 270 acres of additional

IC area could be created in the watershed due to future residential development by the years 2025 and 2040,

respectively. These represent increases are approximately 15 and 20 percent higher than the total amount of IC area

currently in the watershed based on the 2010 high resolution aerial imagery. More than 75 percent of this new

residential IC area is expected to be developed in Durham primarily because it makes up a relatively large proportion of

the land area and population within the watershed.


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14 Results

Table 4.2: Projected Impervious Cover Growth due to Future Population Growth and Residential Development

Town

2010 Watershed Population

2010 Total IC

Area (acres)1

Projected Population Growth (new

residents)

Average Current IC

Area/Capita Ratio2

Sum of Projected Future Residential IC Area (ac) for

Residential Zoned Areas

2025 2040 2025 2040

Barrington 1,651 82 185 268 0.05 7 11

Dover 2,764 125 229 365 0.04 13 21

Durham 6,219 493 1,398 1,995 0.12 131 187

UNH 7,582 248 252 359 0.04 12 15

Lee 2,369 220 28 138 0.05 2 7

Madbury 1,209 108 163 225 0.08 14 19

Nottingham 437 17 109 123 0.04 4 5

Total 22,232 1,293 2,364 3,471 183 265 Notes: The 2010 Impervious cover area includes all IC types including roadways and the UNH Main campus area. The IC area per capita represents an average ratio for all residential zoned areas in each Town, which varies from zone to zone. Due to the distribution of the future population amongst the different residential zones with different development densities, multiplying the average IC area for each town by the population growth estimate for each town will not result in the same IC area estimate shown as the total IC values represent a sum total for all zoning districts.

The projected percent increase in new IC area relative to the existing amount of IC area ranges from approximately 5

percent increase in Lee to approximately 38 percent increase in Durham. The amount of IC area that will ultimately be

developed in the future will depend on a wide variety of factors not the least of which includes the primary type of

future residential development in each Town (i.e., large single-lot, multifamily, etc.) and how similar this compares to

the historical development activity.

4.3. Estimated Impervious Cover Growth Related to Future Commercial/Industrial Development

The amount of IC area that would be created from future commercial development was estimated based on the

existing ratio of IC area per acre of commercially or industrially developed land. This ratio was calculated using the

2010 zoning, land use and impervious cover GIS data layers.

Table 4.4 provides a breakdown of the existing commercially developed and related IC area in the watershed based on

the 2010 GIS land use and IC data. All totaled, there is approximately 500 acres of commercially or industrially

developed land and approximately 279 acres of existing IC area within the watershed. As discussed in Section 3.4, the

UNH Campus, Durham and Lee contain the bulk of the existing commercially developed areas in the watershed.

Table 4.4 also presents a summary of the existing amount of commercial and industrial developed area in each town,

the amount of IC area, the existing ratio of IC area to commercial-developed area, the amount of undeveloped,

commercially-zoned and the projected amount of future commercial development and IC area for each community.

The amount of commercially-zoned land considered to be available and buildable was estimated to be approximately

1,800 acres, based on existing zoning maps for each community. Available means currently undeveloped and buildable

means excluding constrained land areas (i.e., NWI wetlands, poorly and very poorly drained soils, steep slopes,

conservation lands and existing developed areas) from the total available commercially zoned land. In this study the

assumption that 20 percent of the available and buildable commercial land will likely be developed over the next 30

years results yielded an additional 415 acres of commercial development. This compares to the approximately 501

acres that are currently commercially developed in the watershed. This projected amount of future commercial or

industrial development is projected to result in an additional 240 acres of new IC area. This estimated increase in IC

area is similar in magnitude to that projected for future residential development.


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15 Results

For most communities and UNH, the projected amount of new commercial IC area that would be added in the future is

comparable to the existing amount of commercial IC area within each town, with the exception of Barrington.

Barrington currently has a limited amount of commercially or industrially developed within the watershed relative to

the amount of available, undeveloped commercially zoned land. Since much of this commercially-zoned land exists

along the Route 4 and 125 corridors, which has seen a fair amount of recent commercial development activity in the

last 5 to 10 years, it would seem reasonable to expect that the future development activity is likely to increase and

perhaps accelerate in this area. For the other towns, the projected increase in IC area from future development is less

than what currently exists, suggesting that this approach produced conservative estimates of the potential future

growth.

4.4 Future Pollutant Loads Related to Future Development with and without Stormwater Regulations

Table 4.5 presents a summary of the estimated pollutant load increases associated with the added IC area attributable

to future residential and commercial development within the Oyster River watershed. Projected pollutant load

estimates were developed based on the amount of future commercial and residential IC area expected to be subject to

the local stormwater regulations and the anticipated enhanced stormwater treatment with and without the regulations

in place. The pollutant load estimates are based on assumed removal efficiencies of 87, 55 and 60 percent for TSS, TP

and TN, respectively, for stormwater treatment BMPs that are similar to the enhanced bioretention systems that

provide an internal storage reservoir as developed by the UNH Stormwater Center (UNH SC 2012). These type of

treatment BMPs require a relatively small footprint and can be utilized in a wide variety of site conditions. For this

treatment to occur, it is assumed that each watershed town has, or would adopt the model regulations requiring

stormwater treatment in the immediate future.

Table 4.5: Estimated Pollutant Loads Associated with the Projected Future Residential and Commercial Development Activity

in the Oyster River Watershed with and without Enhanced Local Stormwater Regulations in Place

Town Land Use

Projected Increase in

IC Area (acres)

Estimated IC Area

Subject to Regs1

TSS (lbs/yr) TP (lbs/yr) TN (lbs/yr)

w/out

regs

w/

regs

Net

Reduct

w/out

regs

w/

regs

Net

Reduct

w/out

regs

w/

regs

Net

Reduct.

Barrington

Residential 11 5 2,835 1,602 1,233 17.3 12.6 4.7 172 120 52

Commercial 28 23 17,123 5,206 11,918 73.4 41.1 32.3 660 343 317

Subtotal 39 28 19,959 6,808 13,151 90.7 53.7 37.1 832 464 369

Dover

Residential 21 11 5,583 3,154 2,428 34 25 9 338 237 101

Commercial 31 25 19,005 5,778 13,228 81 46 35 733 306 427

Subtotal 52 36 24,558 8,932 15,656 115 70 45 1,071 543 528

Durham

Residential 187 150 49,622 15,085 34,537 304 170 134 3,007 1,563 1,443

Commercial 75 60 46,110 14,018 32,094 198 111 87 1,779 590 1,188

Subtotal 262 210 95,733 29,103 66,630 502 281 221 4,785 2,154 2,631

UNH

Residential 15 12 4,089 1,243 2,846 25 17 8 248 129 119

Commercial 82 66 50,398 15,321 35,077 216 121 95 1,944 1011 1,320

Subtotal 99 79 54,488 16,564 37,923 241 138 103 2,192 1,140 1,052

Lee

Residential 7 4 1,971 1,113 857 12 9 3 119 84 36

Commercial 18 15 11,304 3,436 7,868 48 27 21 436 322 114

Subtotal 28 20 13,274 4,550 8,725 60 36 24 555 405 150

Residential 19 9 5,010 2,830 2,180 31 22 9 304 215 91


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16 Results

Notes: 1Extimated IC area subject to the proposed local regulations assume 80 percent of the proposed commercial IC area and 50 percent of the residential IC area would be subject to the new regulations except in Durham and Dover where 80 percent of both types of IC area would be subject to the new regulations. Pollutant load reductions for treated IC areas assume stormwater BMPS provide removal efficiencies of 87, 55 and 60

percent removal for TSS, TP and TN, respectively.

The results indicate that the added IC area resulting from the estimated future residential and commercial

development in the Oyster River watershed over the next 30 years could increase the average annual pollutant loads

for Total Suspended Solids (TSS), Total Phosphorus (TP) and Total Nitrogen (TN) by approximately 217,667, 1,062 and

9,945 pounds, respectively, if no local stormwater regulations are adopted and no enhanced stormwater treatment

was provided. These potential increases would likely result in substantial adverse impacts to downstream water bodies,

especially since they are already classified as impaired due to existing pollutant contributions. For comparison, a

separate study, which estimated existing nitrogen loads in the Oyster River watershed, indicated that the average

annual total nitrogen load generated from existing IC areas was approximately 14,400 pounds per year (VHB, 2012).

The projected annual nitrogen load from the future IC area without stormwater treatment was estimated to add an

additional 10,000 pounds per year or result in approximately a 70 percent increase over the current existing load.

The level of stormwater treatment assumed to be required by the local regulations could reduce the future average

annual pollutant loads by approximately 40 to 70 percent depending on the pollutant and would potentially prevent

the discharge of approximately 147,144 pounds (~74 tons), 450 pounds and 4,900 pounds for TSS, TP and TN,

respectively, from entering the Oyster River and Great Bay estuaries. This would result in substantial water quality

benefits compared to having no standard or an out-date standard. For nitrogen alone, more than half of the predicted

future annual load attributed to new IC areas could be reduced by providing enhanced stormwater treatment.

The estimated pollutant load reductions could occur with essentially no direct or capital expense to the Towns as the

cost of the enhanced stormwater treatment would be borne by the developers of proposed projects. The estimated

load reductions could be even higher depending on the stormwater BMP type used and the amount of IC area treated.

In this study, approximately 76 percent or 386 acres out of the 505 acres of the estimated new IC area to be developed

in the watershed was assumed to be treated. This was based on assumptions that 50 percent of the future residential

IC area and 80 percent of the future commercial IC area would be treated for most towns with the exception of Dover

and Durham, where 80 percent of both the future residential and commercial IC area would be treated. The

stormwater BMPs were assumed to provide 87, 55 and 60 percent removal for TSS, TP and TN, respectively. Gravel

wetlands have been shown to have a higher removal efficiency for nitrogen and similar removal efficiencies for TSS and

TP (UNH SC 2012).

Even though Durham and UNH comprise a major portion of the watershed and the estimated future pollutant loads in

the watershed, adoption of the enhanced stormwater regulations in the other watershed towns could result in annual

load reductions of approximately 42,600, 124 and 1,210 pounds for TSS, TP and TN, respectively. These represent

substantial reductions even though these other towns make up a relatively small portion of the watershed area. Since

the proposed regulations would apply to future development in the other remaining portions of the towns outside the

Oyster River watershed, much greater load reductions would actually occur for the larger Great Bay watershed.

Madbury

Commercial 5 4 2,900 882 2,018 12 7 5 112 67 45

Subtotal 24 13 7,910 3,712 4,198 43 29 14 415 282 136

Nottingham

Residential 5 2 1,278 772 556 8 6 2 77 54 23

Commercial 1 1 438 133 305 2 1 1 17 10 7

Subtotal 6 3 1,716 905 861 10 7 3 94 64 30

Totals 505 386 217,667 70,523 147,144 1,062 615 447 9,945 5,049 4,896


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17 Results

4.5. Estimated Effect of Proposed Regulations on Future Redevelopment Projects

Redevelopment of existing properties is also likely to occur in the future. Although redevelopment of commercial and

multi-family residential properties are also often subject to local Planning Board review, the level of conformity and

compliance to new regulations can vary widely depending on the site-specific conditions and community preferences

for encouraging redevelopment projects. The extent and location of future redevelopment projects is difficult to

predict. For purposes of this analysis, it was generally assumed that 25 percent of the existing commercial and

industrial IC area in each Town would be redeveloped over the next 30 years. This represents an estimated

redevelopment rate of slightly less than 1 percent per year for the existing commercial and industrial IC area.

Redevelopment of existing residential properties is also likely to occur over time but was not included in this analysis.

Table 4.6 presents the estimated pollutant load reductions that could result from the projected redevelopment

projects for the Oyster River Watershed.

Table 4.6 Estimated Pollutant Loads Resulting from Potential Redevelopment Projects in the Oyster River Watershed

Notes: 1Estimated IC area subject to local regulations represents 25% of the existing commercial and industrial IC area in each town. However, only 50% of this area

assumed to be redeveloped would be treated by new stormwater BMPs. Nottingham has no existing commercial IC area in the watershed to be redeveloped.

Based on the assumptions used in this study, approximately 70 acres or 25 percent of existing commercial and

industrial IC area in the watershed was estimated to be redeveloped over the next 30 years or by 2040. Again, more

than half of this predicted redevelopment activity is expected to occur in Durham and/or on the UNH campus just

because they have the larger share of the existing IC area. Minimal redevelopment activity is projected to occur in

Barrington, Dover and Madbury and no redevelopment was estimated to occur in Nottingham since there are no

existing commercial properties in the watershed. If 50 percent of this redeveloped IC area was treated with enhanced

stormwater BMPs as a result of the proposed local regulations, this could reduce existing pollutant load contributions

by approximately 18,500, 50 and 495 pounds for TSS, TP and TN, respectively, on an average annual basis. These

represent fairly substantial load reductions that could be accomplished with essentially no direct cost to the Towns

since the cost of the stormwater treatment measures would be borne by the developers as new development and

redevelopment projects are proposed.

Town

Existing

Commercial

IC Area

(acres)

Estimate

d IC Area

Subject

to Regs1

TSS (lbs/yr) TP (lbs/yr) TN (lbs/yr)

w/out

regs w/ regs

Net

Reduct

w/out

regs

w/

regs

Net

Reduct

w/out

regs

w/

regs

Net

Reduct

Barrington 4 1 613 346 267 3 2 1 24 17 7

Dover 32 8 4,906 2,772 2,134 21 15 6 189 132 57

Durham 87 22 13,326 7,529 5,797 57 41 16 514 360 154

UNH 94 23 14,372 8,120 6,252 62 45 17 554 388 166

Lee 55 14 8,423 4,759 3,644 36 26 10 325 227 98

Madbury 7 2 1,018 575 443 4 3 1 40 28 12

Nottingham -- -- -- -- -- -- -- -- -- -- --

Total 279 70 42,672 24,110 18,562 183 133 50 1,646 1,152 494


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18 Results

Figure 4.1: Estimated Pollutant Load Reductions from Baseline Condition Over a Permit Term (5 years) from Redevelopment

Activities

The potential water quality benefits for redeveloped would be even greater for the larger Great Bay watershed, since

the local stormwater regulations would apply to other potentially developed and redeveloped areas in the remaining

portions of the Towns outside the Oyster River watershed. The combined effect that the proposed regulations on both

future and existing pollutant loads contributed by IC area is likely to be one of the most important and cost-effective

management strategies available to protect and possibly restore water quality conditions in the Great Bay estuary. The

proposed local regulations are likely to have even greater impact on future pollutant loads when factoring in potential

runoff volume reductions resulting from low impact development and groundwater recharge measures that are

included in the regulations but were not evaluated as part of this analysis.


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19 Results

5.0 Discussion

The results of this study indicate that approximately 500 acres of additional impervious cover (IC) area could potentially

be developed in the Oyster River watershed over the next 30 years or by the year 2040 due to future residential and

commercial development activity. This would represent approximately a 40 percent increase over the 1,290 acres of IC

area estimated to exist in the watershed based on 2010 aerial imagery. An additional 500 acres of IC area would bring

the estimated level of imperviousness for the watershed beyond the 10% threshold which has been widely reported as

a significant determinant of water quality attainment. The estimated increase in IC area could potentially be much

higher as historical data indicates that amount of IC area in the watershed increased by approximately 1,000 acres in

the 20 year period between 1990 and 2010.

This added future IC area, if developed without additional stormwater treatment, could increase the average annual

pollutant load for total suspended solids (TSS), total phosphorus (TP) and total nitrogen (TN) in the Oyster River

watershed by approximately 218,000 pounds (~109 tons), 1,060 pounds and 9,950 pounds, respectively. This

additional pollutant load would most likely result in significant further degradation of the water quality conditions in

the Oyster River and downstream Great Bay estuary, as these water bodies are already considered impaired due to

existing pollutant contributions. With respect to total nitrogen, the projected future load, without stormwater

treatment, would represent an increase of approximately a 70 percent over the current average annual load of 14,400

pounds estimated to be contributed from the existing impervious surfaces within the watershed based on a separate

more extensive watershed modeling effort (VHB 2014). Essentially, based on the model results, every acre of new IC

area created without stormwater treatment could contribute approximately 10 pounds of additional nitrogen to

downstream receiving waters on an average annual basis.

This analysis primarily documents unmitigated increases in pollutant loads from projected development and future

land use changes. Both the Oyster River and Great Bay Watersheds are currently listed as impaired. This indicates that

existing pollutant loads must be reduced. Future pollutant loads anticipated from ongoing development and

redevelopment activities represent a confounding issue for any watershed management plan in that current loads need

to be reduced while new development and redevelopment activities continue to threaten further exacerbation of the

problem. Early and widespread adoption of enhanced local stormwater regulations could substantially limit future

pollutant load increases associated with future residential and commercial development. At worst, the regulations

represent a relative cap to the increase of degrading pollutants contributed by new impervious cover. At best, the

pollutant loading potential from new impervious is limited to the maximum extent practicable and redevelopment

projects serve to reduce existing baseline impervious cover and pollutant loads offering water quality benefits that

extend well beyond the Oyster River watershed.

It is also important to note that this study focused solely on estimating potential pollutant load increases from IC area

and did not evaluate the potential added pollutant contributions from other development related sources such as

increased lawn fertilizer use and additional septic systems that would also result from future development activity. The

previous Oyster River watershed modeling effort indicated that the average annual nitrogen load from existing lawn

fertilizer usage and septic systems were similar in magnitude to that contributed from impervious cover on an overall

watershed basis. This would suggest that the overall future pollutant loads at least for total nitrogen could increase by

two to three times that estimated from impervious cover areas alone as a result of future development activity.


Stormwater Center

20 Results

The projected pollutant load reductions might also result in substantial financial benefits for each community by

avoiding or minimizing the potential deferred future costs of having to achieve similar pollutant load reductions in the

future through stormwater BMP retrofits as part of a water quality restoration project or perhaps to meet a pollutant

load allocation imposed by a future TMDL study. It is conceivable that regulated MS4 communities in the Great Bay

watershed may be required in the future to retroactively implement stormwater treatment of existing IC areas to

reduce existing or future added pollutant loads and, thus, would be faced with significant added future costs to install

these retrofit measures. Studies have shown that retroactively implementing stormwater treatment BMPs on

developed sites is often much more costly than the initial implementation costs at the time of development. Recent

stormwater BMP retrofit projects completed by the UNH Stormwater Center in the Seacoast Region have indicated

that design and construction cost for stormwater BMP retrofits averages around approximately $30,000 per acre of IC

area treated (UNH SC 2010). To retroactively treat the estimated future amount of IC area (i.e., 386 acres) that would

otherwise be required to be treated by developers at the time of development if the local stormwater regulations were

adopted plus treating the estimated 70 acres of existing IC area that might be redeveloped and also be subject to the

regulations would cost approximately $14 million in 2014 dollars using an average retrofit cost of $30,000 per acre.

These estimated future costs do not include the cost of inflation nor the added potential cost of lost or diminished

ecological services and/or recreational uses as a result of decreased water quality conditions. Even though Durham

and UNH have the bulk of the IC area in the watershed and would face much of the estimated potential future retrofit

cost, even more rural towns such as Barrington and Madbury, for example, could face future retrofit costs in the range

of $400,000 to $800,000 in 2014 dollars if they had to implement future stormwater retrofits to maintain the current

average annual pollutant loads in the Oyster River watershed as part of some future state or federal regulation update.

These cost estimates only pertain to the portion of each Town that is within the Oyster River watershed, which for

Barrington is less than 10 percent of the total Town area. If the potential savings in deferred costs or cost avoidance

gained through early adoption of stormwater regulations and enhanced treatment were extended to the entire Great

Bay watershed, the potential future cost savings could be huge.

The findings of this analysis clearly demonstrate that adopting local stormwater regulations to require more stringent

stormwater treatment standards could have a tremendous positive impact in minimizing the additional future pollutant

loads that could be discharged in the Great Bay estuary. This could significantly alter the current trajectory of declining

water quality conditions. As an incentive for Towns to engage early in the protection and restoration of the water

quality conditions in the Great Bay estuary and perhaps assist regulated MS4 communities in addressing the ever-

increasing more stringent federal permit requirements, the results of this study could provide the initial framework for

establishing pollutant load reduction credits for early adoption and maintaining strict adherence to enhanced local

stormwater regulations as it relates to future development and redevelopment activity in the watershed. The study

findings also highlight the importance of land conservation and preservation as another highly effective management

tool to limit and prevent future pollutant load increases in the Great Bay watershed.


Stormwater Center

21 Results

6.0 References

NH Department of Environmental Services (NHDES). 2008. New Hampshire Stormwater Manual. Volume 1.

http://des.nh.gov/organization/commissioner/pip/publications/wd/documents/wd-08-20a.pdf

NHDES. 2012, 303(d) list of Impaired Water Bodies.

http://des.nh.gov/organization/divisions/water/wmb/swqa/2012/

NHDES. 2014. Great Bay Nitrogen Nonpoint Source Study. Final Report R-WD- 13-10. June 16, 2014.

http://des.nh.gov/organization/divisions/water/wmb/coastal/documents/gbnnpss-report.pdf

Southwest Watershed Alliance. 2012. Model Stormwater Standards for Coastal Watershed Communities. Prepared

by the UNH Stormwater Center and Rockingham Planning Commission.

http://southeastwatershedalliance.org/wp-content/uploads/2013/05/Final_SWA_SWStandards_Dec_20121.pdf

University of New Hampshire. Stormwater Center. 2012 Biennual Report.

http://www.unh.edu/unhsc/sites/unh.edu.unhsc/files/docs/UNHSC.2012Report.10.10.12.pdf

UNH Complex Systems. NH GRANIT. 2010. Impervious Cover Mapping of the Coastal NH Communities and Maine.

http://www.granit.sr.unh.edu/Project?project_id=204

Vanasse Hangen Brustlin, Inc. 2014. Oyster River Integrated Watershed Plan for Nitrogen Load Reductions.

Prepared for the Town of Durham and the University of New Hampshire, with Assistance from Woodard & Curran.

http://www.oysterriveriwp.com/pdf/2014-07-10-ORIWMP-v12-Final%20with%20cover.pdf

http://des.nh.gov/organization/commissioner/pip/publications/wd/documents/wd-08-20a.pdf

http://des.nh.gov/organization/divisions/water/wmb/swqa/2012/

http://des.nh.gov/organization/divisions/water/wmb/coastal/documents/gbnnpss-report.pdf

http://southeastwatershedalliance.org/wp-content/uploads/2013/05/Final_SWA_SWStandards_Dec_20121.pdf

http://www.unh.edu/unhsc/sites/unh.edu.unhsc/files/docs/UNHSC.2012Report.10.10.12.pdf

http://www.granit.sr.unh.edu/Project?project_id=204

http://www.oysterriveriwp.com/pdf/2014-07-10-ORIWMP-v12-Final%20with%20cover.pdf

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Attachment B: Final educational fact sheet

Trigger Threshold PercenT regulaTed

5,000 sf 80%10,000 sf 60%20,000 sf 50%

40,000 sf 30%

Table 1: Statistics for existing commercial developments in Durham that would be subject to regulation.

Minimizing Environmental Impacts Through Stormwater Ordinance and Site Plan Regulation

The Seacoast Region and the larger Great Bay watershed represents one of the fastest developing regions in the state. Stormwater runoff from impervious surfaces has been shown to be one of the leading causes for declining water quality and increased flooding in our region’s water resources. The Great Bay Estuary, a critical ecological and economic resource in the NH Coastal Region is listed as impaired due to declining water quality conditions resulting from increased pollutant loads largely contributed from non-point sources. As future development continues to unfold, pollutant loads from development activity are only going to increase.

In 2012, the Southeast Watershed Alliance (SWA) commissioned the UNH Stormwater Center and the Rockingham Planning Commission to develop model stormwater standards that communities could adopt in zoning or land development regulations to help minimize the environmental impacts of increased stormwater runoff from new and redevelopment activity.

G R E E N I N F R A S T R U C T U R E F O R N E w h A m p S h I R E C O A S TA L C O m m U N I T I E S

Environmental and Financial Benefits of Adopting Local Stormwater Regulations to Reduce Pollutant Loads Associated with Future Development

sWa Model sTorMWaTer sTandards Core Elements:• PromoteLIDPlanningand“Green

Infrastructure”• Enablegroundwaterrechargeandvolume

control• Addressexistingimperviouscoverthrough

redevelopment requirements• Requireoperationsandmaintenance

PiloT TesT case Using the Oyster River watershed as a pilot test case, this study evaluated the financial and ecological benefits of adopting the enhanced model stormwater standards to reduce future pollutant loads resulting from expansion of impervious area in the watershed over the next 30 years. The standards would apply to new development and redevelopment projects subject to site plan and/or subdivision review by the Planning Board. This includes most, if not all, commercial or mixed use development projects and residential multi-family or subdivision projects.

FuTure coMMercial ic areaOne of the most important aspects of the model regulation is the adoption of the actual trigger threshold which would require a new development or redevelopment to comply with the regulatory standards. Often this decision is made by comparing the state program trigger (100,000 sf of disturbance) to the proposed town standard. The model advocates adoption of a 5,000 sf trigger condition. This aspect of the regulation has a substantial effect on the future water quality and pollutant load reduction potential and should be carefully considered.

For context the statistical analysis of existing impervious cover (IC) for commercial parcels in Durham is shown in Table 1.

0 50 10015020025030035040045050039BARRINGTON

52DOVER

262DURHAM

99UNH

28LEE

24MADBURY

6NOTTINGHAM

TOTALS

Durham and UNH account for 70% of future projected IC area increases.

Figure 1: ProjectedincreaseinICArea(acres).

ProjecTed FuTure ic area by 2040Another important component of the study was the watershed-based approach as opposed to simply analyzing changes in a particular town or city. Since most towns contribute to multiple watersheds – as is the case with Barrington, Dover and Nottingham – only a portion of the land area of those municipalities contributes to the overall watershed load. In the Oyster River watershed, another 500 acres of IC area is estimated to be added over the next 30 years due to future residential and commercial development activity (Figure 1).

WITHOUT REGS

WITH REGS

NET REDUCTION

350

450400

300

150

250200

10050

0MIL

LIO

NS

OF

DO

LLA

RS

COST AVOIDANCE FOR GREAT BAY WATERSHED

ToWnFuTure ic TreaTed

FuTure cosTs$30K Per acre

barrington 29 $861,000

dover 43 $1,300,000

durham 231 $6,944,000

unh 102 $3,048,000

lee 32 $967,000

Madbury 15 $446,000

nottingham 3 $89,000

ToTal 455 $13,655,000

Figure 4:CostAvoidance

are relatively easy and inexpensive to implement, can be highly effective in reducing future pollutant loads not only from future development but from existing untreated commercial land uses as well. In essence these model standards can leverage the economic investment of developers in redevelopment projects to improve water quality conditions in the Great Bay and meet future state and federal permit requirements. Over the course of a five-year permit term, this study found that a 1.8% decrease in TSS, 1.1% decrease in TP and a 1.3% decrease in TN from baseline pollutant loads could be credited to a municipality that updated their stormwater standards. (Figure 3).

In addition, early adoption of these model standards could result in substantial cost savings through future cost avoidance in not having to construct numerous stormwater BMP retrofits to meet future regulations. The overall cost to retrofit this IC area would be approximately $14 million, using an average retrofit cost of $30,000 per acre. These estimated future costs do not include the

13,300

0

20,000

40,000

60,000

80,000

100,000

Barrington Dover Durham UNH Lee Madbury Nottingham

19,9586,800

24,600 29,100

8,90016,600

4,600 7,9003,700

TSS (lbs/yr) w/out regs

TSS (lbs/yr) w/ regs

1,700 900

95,700

54,500

0

200

100

300

400

500

600


54116

501

280241

13861 43 2936 10 7

TP (lbs/yr) w/out regsTP (lbs/yr) w/ regs

91 70

0

1,000

2,000

3,000

4,000

5,000


4641,071

2,154

543

2,192

1,140555 405 415 282 94 64

TN (lbs/yr) w/out regsTN (lbs/yr) w/ regs

4,785

832

Figure 2: EstimatedEffectonFutureTSS,TPandTNLoads(lbs/yr)DuetoStormwaterRegulations

13,300

0

20,000

40,000

60,000

80,000

100,000


19,9586,800

24,600 29,100

8,90016,600

4,600 7,9003,700



1,700 900

95,700

54,500

0

200

100

300

400

500

600


54116

501

280241

13861 43 2936 10 7


91 70

0

1,000

2,000

3,000

4,000

5,000


4641,071

2,154

543

2,192

1,140555 405 415 282 94 64


4,785

832

13,300

0

20,000

40,000

60,000

80,000

100,000


19,9586,800

24,600 29,100

8,90016,600

4,600 7,9003,700



1,700 900

95,700

54,500

0

200

100

300

400

500

600


54116

501

280241

13861 43 2936 10 7


91 70

0

1,000

2,000

3,000

4,000

5,000


4641,071

2,154

543

2,192

1,140555 405 415 282 94 64


4,785

832

G R E E N I N F R A S T R U C T U R E F O R N E w h A m p S h I R E C O A S TA L C O m m U N I T I E S

0.0%

0.5%

1.0%

TSS TP TN

1.5%

2.0%

% R

EDU

CTI

ON

OF

TO

TAL

EXIS

TIN

G L

OA

D

Figure 3: Pollutant load reduction credit per permit term(5years)

cost of inflation nor the added potential cost of lost or diminished ecological services and/or recreational uses as a result of decreased water quality conditions. A breakdown of the estimated cost avoidance for each town within the Oyster River watershed is shown in Figure 4.

This represents a 40 percent increase over existing conditions. With no local stormwater regulations in place, by 2040 this new IC area would increase the average annual Total Suspended Sediment (TSS) load by approximately 217,700 pounds ( ~109 tons),as well as add 1,060 pounds of Total Phosphorus (TP), and 9,950 pounds of Total Nitrogen (TN). With enhanced stormwater treatment in place as a result of local stormwater standards, the predicted average annual pollutant loads would be approximately 40 to 70 percent lower, eliminating 147,150 pounds (~74 tons) of TSS, 450 pounds of TP and 4,900 pounds of TN that would otherwise be discharged to the Oyster River and the Great Bay Estuary. For nitrogen alone, more than half of the predicted future annual load attributed to new IC area could be reduced by providing enhanced stormwater treatment. (Figure 2).

PoTenTial reducTion crediTsAn important outcome of this study is that the adoption of more stringent redevelopment requirements, which

econoMic iMPacT – cosT avoidanceIf the potential savings in deferred costs or cost avoidance gained through early adoption of stormwater regulations and enhanced treatment were extended beyond the Oyster River watershed to include the entire Great Bay watershed, the potential future cost savings could be in the hundreds of millions of dollars.

Thisresearchprojectwasconductedbythe UNH Stormwater Center in cooperation with VHB andtheSRPC.TheprojectwasfundedbyEPA.

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Attachment C: Final list of BMP installations in the Oyster River Watershed and results of the award determination.

Project Nam

eClient/Location

Project Collaborator(s)Type of System

Notes

1Berry Brook I

Dover/NHDES

UNHSC and Dover DPW

HSS TBF2Berry Brook I

Dover/NHDES

UNHSC and Dover DPW

HSS Bio 1 (north)3Berry Brook I

Dover/NHDES

UNHSC and Dover DPW

HSS Bio 2 (south)4Berry Brook I

Dover/NHDES

UNHSC and Dover DPW

HSS Bio 2 (south)5Berry Brook I

Dover/NHDES

UNHSC and Dover DPW

15A Hillcrest Ave Bio6Berry Brook I

Dover/NHDES

UNHSC and Dover DPW

Snow Ave Bio

7Berry Brook II

Dover/NHDES

UNHSC and Dover DPW

Central Ave SGW

8Berry Brook II

Dover/NHDES

UNHSC and Dover DPW

BB SW W

etland9Berry Brook II

Dover/NHDES

UNHSC and Dover DPW

Crescent Avenue Veg Swale

10Berry Brook II

Dover/NHDES

UNHSC and Dover DPW

Snow Avenue Veg Sw

ale11

Berry Brook IIDover/N

HDESUNHSC and Dover DPW

Page Avenue Veg Swale

12Berry Brook II

Dover/NHDES

UNHSC and Dover DPW

Lowell Avenue Bio

13Berry Brook II

Dover/NHDES

UNHSC and Dover DPW

Glencrest Avenue Bio

14Berry Brook II

Dover/NHDES

UNHSC and Dover DPW

Upper Horne Street Bio

15Berry Brook III

Dover/NHDES/RBC

UNHSC and Dover DPW

Roosevelt St Bio16

Berry Brook IIIDover/N

HDESUNHSC and Dover DPW

Roosevelt St Rock Basin17

Biopalooza NHDES/Durham

UNHSC and Durham

DPWOyster River Road SG

W18

Tedeschi Innovative BioEPA Region 1/Durham

UNHSC, Durham

DPWBio V

19The Cotages

Capstone Development/Durham

UNHSC, Tighe and Bond

SGW 1

20The Cotages



SGW 2

21The Cotages



Porous Asphalt22

The LodgesDurham

Tighe and BondSG

W23

The LodgesDurham

Tighe and BondSG

W24

Student Apartments

Perry Brant/DurhamUNHSC, Tighe and Bond

Porous Asphalt25

Lee Urgent Care

Wentw

orth Douglass Hospital/LeeSteve Height

Porous Asphaltclogged

26Alum

ni CenterUNH


Porous Asphalt27

Hood HouseUNH/ICPI


PICP28

Peter T Paul Business SchoolUNH

unknown

Porous Asphaltclogged

29Petty Brook Lane

DurhamMike Seivert

bioretention30

Golden G

ooseGolden G

oose Development/Durham

Mike Seivert

Porous Asphalt31

A‐lot RetrofitUNH

UNHSC/U

NH

bioretention 132

A‐lot RetrofitUNH

UNHSC/U

NH

bioretention 233

A‐lot RetrofitUNH

UNHSC/U

NH

bioretention 334

A‐lot RetrofitUNH

UNHSC/U

NH

bioretention 4

# BMPs

Entities/Municipalities

16City of Dover

10Tow

n of Durham6

University of N

ew Ham

pshire# BM

PsEngineering Entities

8Tighe and Bond

2Mike Seivert, M

JS Engineering1

Steve Height, Height Engineering

RESULTS

Oyster River W

atershed LID Survey Results

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Attachment D: Approved Quality Assurance Project Plan

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Documents

EPA Final Report - University of New Hampshire · 2016-10-05 · EPA Final Report Work Plan Tasks: 1.) Development and Piloting of updated stormwater ordinances: This task has been