CCDPC2024-03 Denton Elementary Attachments.pdf

DENTON ELEMENTARY SCHOOL DESIGN AND CONSTRUCTION

OF STORMWATER MANAGEMENT AND WATER QUALITY

BEST MANAGEMENT PRACTICES

Attachments:

1. Sections of Work Plan dated December 1, 2022

2. Sections of AECOM Site Assessment Dated April 17, 2017

3. General Description of the BMPs and Requirements

4. Denton Elementary Existing Site Plans

Attachment 1

Sections of Work Plan dated December 1, 2022

Maryland 319(h) Grant FFY22 Project 06 (SUBAWARD)

12/01/2022 Page 6 of 18

Figure 1. Initial concept design for Denton Elementary School

12/01/2022 Page 7 of 18

The proposed BMPs will address the areas that have been most critically impacted by runoff from impervious surfaces at the site. The bioretention areas will treat runoff from primarily parking lots, which have the highest potential for pollutant- and nutrient-laden runoff. The section below describes the existing conditions and intended outcomes at each of the proposed BMP locations at

Denton Elementary School. Note that for all planning and construction projects, the project sponsors are abiding by the State and County procurement regulations.

Bioretention to Replace Concrete Chutes to Inlet (BMP-BR1)

The northernmost parking lot conveys runoff to two adjacent concrete chutes, which discharge to an inlet within the grass median along Sharp Rd (Figure 2). This project proposes to replace the concrete chutes with a bioretention area (BMP-BR1 in Figure 1).

Figure 2. Concrete chutes conveying runoff from northernmost parking lot at Denton Elementary School to an inlet along Sharp Rd

Permeable Pavement in Northernmost Parking Lot (BMP-PP1)

Denton Elementary School and its students, teachers, and parents are also impacted by frequent stormwater flooding of the school’s front parking and entrance areas. The impervious asphalt in the northernmost parking lot is in need of repair (Figure 3). This project proposes to remove approximately 9,000 sq. ft. of impervious asphalt in the parking stalls of the northernmost parking lot and replace it with a permeable pavement system, such as porous pavers, with underdrain connections to the adjacent bioretention areas. Surface and grading improvements will be made to the asphalt in the driving lanes to improve their connection to the porous pavers (BMP-PP1 in

Figure 1).

12/01/2022 Page 8 of 18

Figure 3. Northernmost parking lot at Denton Elementary School (right side of photo)

Bioretention Areas and Pedestrian Walkways (BMP-BR2)

There is an open grass area between the two parking lots north of the school building with a narrow walkway in the center (Figure 4), which frequently floods during rain events. This project proposes to install three adjacent bioretention areas with two pedestrian walkways/bridges (BMP-BR2 in

Figure 1). The County envisions an entrance courtyard similar to the project constructed at Atkins

Arboretum (Figure 5).

Figure 4. Grass area with narrow walkway between northernmost parking lot and front door of Denton Elementary

School

12/01/2022 Page 9 of 18

Figure 5. Entrance courtyard at Atkins Arboretum with bioretention areas and pedestrian walkways

Bioretention Areas along Lupine Ln (BMP-BR3 and BMP-BR4)

Runoff from each of the two parking lots west of the school building is conveyed to inlets in the grass median along Lupine Lane (Figure 6). This project proposes to install two separate bioretention areas in the grass median, one adjacent to each parking lot (BMP-BR3 and BMP-BR4 in Figure 1).

Figure 6. Inlets in grass median along Lupine Ln collecting runoff from western parking lots (photo is proposed location for BMP-BR4)

12/01/2022 Page 10 of 18

Conservation Landscaping “Living Classroom” near Front Door (BMP-CL1)

There is a small courtyard area near the front door of Denton Elementary School where turf grass and minimal shrubby vegetation is bordered by sidewalks, and there is a partial opening in the overhead rooftop (Figure 7). This project proposes to install a conservation landscaping area here that can function as a living classroom for students. Caroline County Public Schools intends to involve students from both Denton Elementary School and North Caroline High School in the design and planting of the conservation landscaping area. Educational signage will be posted to highlight the benefits that the living classroom provides to local birds and pollinators.

Figure 7. Proposed location for conservation landscaping "living classroom" in front of Denton Elementary School

Native Tree Planting at Southeastern Corner (BMP-TP1)

At the southeastern corner of the property, south of the fields, there is an unused grass area that is proposed for a large-scale native tree planting (Figure 8).

12/01/2022 Page 11 of 18

Figure 8. Unused grass area at southeastern corner of Denton Elementary School where native trees can be planted

Process

The County has classified the HUC12 subwatershed in which Denton Elementary School is located as a Second Priority Watershed in the Upper Choptank River Watershed Plan, and this proposed project meets the plan’s goals to address NPS pollution and develop educational components that enhance public understanding and participation in watershed stewardship. The County will work with its partners and contractors to ensure that construction of the proposed BMPs is completed in the most timely, cost-effective manner.

As the County and its partners move forward with watershed plan implementation for both the

Upper Choptank Watershed Plan and for the County’s Phase II and Phase III WIPs, new partnerships will be developed with agencies and municipalities in the County, and additional projects on public sites will be identified for inclusion in the prioritized inventory of potential project sites. County staff will work towards developing these new partnerships to foster on-site nutrient and sediment reduction projects as well as BMPs for property management and maintenance.

Attachment 2

Sections of AECOM Site Assessment Dated April 17, 2017

***Note the AECOM Site Assessment does not include in the permeable pavement parking aisles that are a part of this bid proposal***

The portions of the AECOM report that were omitted pertain to other site assessments not include within this project.

Submitted by:

AECOM

Sabre Building, Suite 300 4051 Ogletown Road Newark, DE 19713

Water Quality Retrofit Prioritization and Implementation Plan for

Caroline County, Maryland Public Schools

April 17, 2017

AECOM Table of Contents

CC Public Schools Report Rev 041717.docx

Table of Contents Executive Summary ...............................................................................................i

1.0 Introduction

2.0 Methodology

3.0 Guiding Principles

4.0 School Site Assessments

5.0 Summary

6.0 Recommended Future Tasks

List of Appendices Appendix A Soil Types and Summaries of Hydrologic Soil Groups Appendix B Total Nitrogen, Total Phosphorous, and Total Suspended Solids Loading

Rates Appendix C Percent Load Reductions and Approximate Costs C1 Narrative

C2 Upper Choptank River Locations C3 Lower Choptank River Locations C4 Excerpt from Recommendations of the Expert Panel to Define

Removal Rates for Urban Stormwater Retrofit Projects prepared by the Chesapeake Stormwater Network (CSN) dated January 20, 2015

C5 Excerpt from Costs of Stormwater Management Practices in Maryland Counties (Draft Final Report) prepared for the Maryland Department of the Environment by the University of Maryland Center for Environmental Science dated October 2011

AECOM Table of Contents

List of Abbreviations

BMP Best Management Practices CCDPC Caroline County Department of Planning and Codes CCPS Caroline County Public Schools ESD Environmental Site Design GIS Geographic Information Systems LID Low Impact Development MDSG University of Maryland Sea Grant Extension Program NFWF National Fish and Wildlife Foundation NRCS Natural Resource Conservation Service TMDL Total Maximum Daily Load WIP Watershed Implementation Plan i

Executive Summary

This report evaluates the feasibility of placing stormwater best management practices (BMPs) at Caroline County’s ten public schools / centers, located on eight campuses, and identifies opportunities for water quality retrofits at each. Two of the original 10 schools were dropped from further consideration.

The remaining schools / centers that were evaluated in this report are as follows:

Colonel Richardson Middle and High School Denton Elementary School Federalsburg Elementary School Lockerman Middle School North Caroline High School and Caroline Career & Technology Center Ridgely Elementary School Two of these locations, Colonel Richardson Middle and High School and Federalsburg Elementary School are in the Lower Choptank watershed while the remaining sites are within the Upper Choptank watershed.

AECOM used three approaches simultaneously to develop concept-level water quality retrofits:

Desktop exercise – using GIS, an analysis of topography, soils, ground water elevations, buildings, driveways, parking lots, streams, and rivers was performed for each site. The GIS data was collected from CCDPC, and open sources such as Natural Resource Conservation Service (NRCS) and the Maryland’s Mapping & GIS Data Portal.

Field visits – AECOM personnel visited each campus on two occasions to identify drainage patterns and investigate opportunities for water quality retrofits. During the site visits, field notes and photographs were taken to document existing conditions. Emphasis was placed on opportunities to treat currently untreated impervious surfaces and assessing whether downspouts from roof gutters were tied into underground piping systems or discharged to the surface.

Plan review – site and roof plans were requested from CCPS for each school. These were used to confirm field observations and help determine drainage patterns and runoff flow paths.

AECOM sought to apply measures in accordance with the Maryland Environmental Site Design (ESD) Process and Computation guidance document which specify micro-scale practices. All the identified treatment areas were assessed in comparison to the ESD requirements in order to determine which strategies were most appropriate at each location.

Criteria that were assessed included ground slopes, setbacks from building and wells, maximum drainage area, depth, groundwater elevation, and hydrologic soil groups.

Descriptions of soil types found at each location as well as summaries of hydrologic soil groups are provided in Appendix A.

The ESD concept is predicated on using soil types and proposed site imperviousness to determine the amount of rainfall (or target PE) that would need to treated in order for the ii proposed practice to replicate runoff conditions on a wooded site. In other words, if an ESD measure was designed, constructed, and maintained properly, the pollutant amount in post-treated runoff would be same as would have existed in the pre-developed, natural state which is assumed to have been wooded.

PE varies by soil type and percent imperviousness of the drainage or catchment area. While site (or in these instances catchment area) imperviousness was determined with a reasonable level of certainty, soil types were based on mapping which is generalized making precise determination of PE difficult. For this report, PE was set at 2.0 inches which is the rainfall amount that would need to be captured by a 60% impervious surface in “A” type soils or a 65% impervious surface in “B” type soils which was fairly indicative of the situations encountered at each site.

Each school’s campus evaluation includes the following:

• Written description of existing conditions, availability of plans, and discussion of potential BMPs. Historical perspective was developed in part from the Caroline County Board of Education & Vitech Consulting Services report entitled 2015 Educational Facilities Master Plan Caroline County Public Schools.

• Aerial photographs with potential or existing BMP locations and associated drainage or catchment areas shown. Existing treatment areas are identified by “ETA” and proposed treatment areas by “PTA” in the exhibits.

• Spreadsheets with preliminary BMP sizes, approximate costs, loading rates for total nitrogen (TN), total phosphorous (TP), and total suspended solids (TSS), and TN, TP, and TSS reductions resulting from the BMPs. See below for further explanation.

• Site photographs and descriptions showing many of the BMPs.

The basis for the spreadsheets for each school is found in Appendices B and C. Appendix B includes total nitrogen (TP), total phosphorous (TP), and total suspended solids (TSS) loading rates which were taken from a spreadsheet developed by the Maryland Department of Natural Resources and provided by MDSG. As previously noted, four of the six locations are in the Upper Choptank watershed while the remaining two are in the Lower Choptank watershed.

Delivered loading rates were used in favor of edge of stream loading rates.

Appendix C provides a detailed explanation of the development of pollutant removal rates for each type of BMP in both watersheds as well as costs over a 20-year time frame and cost per pound TN, TP, and TSS removed. ETAs represent areas that are already being treated by BMPs.

The impervious areas, costs over a 20-year time span, and TN, TP, and TSS load reductions at each school site are summarized as follows:

Colonel Richardson Middle and High School

Impervious area (ft²)

Approximate Cost ($ over 20 year life span)

TN reduced (lbs/yr)

TP reduced (lbs/yr)

TSS reduced (lbs/yr)

Potential BMPs 103,300 $203,780 14.37 1.94 1,340 Existing BMPs 22,600 - 3.21 0.43 300 iii

Denton Elementary School

Impervious area (ft²)

Approximate Cost ($ over 20 year life span)

TN reduced (lbs/yr)

TP reduced (lbs/yr)

TSS reduced (lbs/yr)

Potential BMPs 57,850 $104,210 9.33 1.11 533 Existing BMPs 13,600 - 1.10 0.13 63

Federalsburg Elementary School

Impervious area (ft²)

Approximate Cost ($ over 20 year life span)

TN reduced (lbs/yr)

TP reduced (lbs/yr)

TSS reduced (lbs/yr)

Potential BMPs 51,000 $91,820 7.23 0.98 674 Existing BMPs 7,800 - 0.55 0.07 52

Lockerman Middle School

Impervious area (ft²)

Approximate Cost ($ over 20 year life span)

TN reduced (lbs/yr)

TP reduced (lbs/yr)

TSS reduced (lbs/yr)

Potential BMPs 26,700 $142,150 4.31 0.51 247 Existing BMPs - - - - -

North Caroline High School and Caroline Career & Technology Center

Impervious area (ft²)

Approximate Cost ($ over 20 year life span)

TN reduced (lbs/yr)

TP reduced (lbs/yr)

TSS reduced (lbs/yr)

Potential BMPs 92,800 $147,215 14.94 1.78 855 Existing BMPs 25,100 4.06 0.48 232

Ridgely Elementary School

Impervious area (ft²)

Approximate Cost ($ over 20 year life span)

TN reduced (lbs/yr)

TP reduced (lbs/yr)

TSS reduced (lbs/yr)

Potential BMPs 22,500 $40,565 3.63 0.43 207 Existing BMPs - - - - -

If all of the potential BMPs depicted in the exhibits and spreadsheets were implemented, the 20-year costs would be approximately $730,000 and would result in the removal of 53 pounds of nitrogen, 6.7 pounds of phosphorous, and 3,825 pounds of total suspended solids.

iv

Existing BMPs were estimated to be resulting in the removal of 8.9 pounds of nitrogen, 1.1 pounds of phosphorous, and 646 pounds of total suspended solids.

This study established the feasibility of placing stormwater BMPs at eight schools at six locations and estimated costs and pollutant load reductions. Several steps would need to be taken to progress into design and construction as follows:

One of this report’s objectives is to help meet Chesapeake Bay WIP milestones. As explained in the Summary section, costs on a per pound removed basis are higher for TN in the Lower Choptank watershed but higher for TSS. CCDPC may need to decide which constituent is most important as this will be a factor in prioritizing.

Since costs per pound of TN, TP, or TSS removed do not vary from site to site within the same watershed, CCPS should review the potential locations and decide which would be best from an operational standpoint. MDSG may want to provide input regarding how these locations could facilitate learning opportunities at each school.

Once a list of preferred BMPs is established, additional effort would be needed to confirm the areas draining to each as well as ground slopes (for rooftop runoff disconnection). Also CCPS will need to find the locations of water wells and septic tanks as well as underground utilities.

The BMPs described herein have various setback requirements that would need to be factored in. Conflicts could result in BMPs being dropped from further consideration.

Soil testing would then be needed at the remaining BMPs. As previously stated, infiltration is the preferred option over bioretention. However, based on soil mapping, poorly draining soils and / or high groundwater elevations may exclude the use of infiltration at some locations.

Also, as explained in the Guiding Principles section, forebays may be needed at some infiltration locations. Surveying of each location would be needed in order to develop construction plans.

Finally, construction plans taking into account requirements and limitations as stipulated in the Maryland Stormwater Design Manual , Volumes I and II dated October 2000 and Revised May 2009, would need to be prepared. It is assumed that CCDPC would self-permit the projects.

1.0 Introduction

As an approved Technical Service Provider, AECOM submitted a grant application for the Chesapeake Bay Technical Capacity Grants Program - Stormwater Management 2015 to the National Fish and Wildlife Foundation (NFWF) in September of 2015. The primary intent of the application was to identify opportunities for water quality retrofits and the disconnection of previously untreated impervious areas at Caroline County schools.

The Caroline County 2-year Water Implementation Plan (WIP), Caroline County 2010 Comprehensive Plan, and the 2010 Upper Choptank River Watershed Based Plan each address the importance of treating stormwater runoff in order to improve water quality and meet Total Maximum Daily Load (TMDL) requirements of the Chesapeake Bay.

There is a correlation between impervious areas and pollutant amounts in runoff which can deteriorate water quality in receiving waterways. Caroline County’s public school campuses occupy 232 acres with over 36 acres of impervious surfaces. Collectively, these campuses represent the largest amount of untreated impervious area on County public property (owned by the Caroline County Board of Education). Therefore, these public schools provide the best opportunity for the County to prioritize water quality projects by addressing its largest source of untreated impervious area.

This report evaluates the feasibility of placing stormwater best management practices (BMPs) at Caroline County’s ten public schools / centers, located on eight campuses, and identifies opportunities for water quality retrofits at each. It is intended to be a planning-level document to help Caroline County meet two of its WIP milestones which are:

1. Identify publically-owned buildings and properties suitable for BMP demonstration/education project sites.

2. Continue to identify and build inventory of potential stormwater BMP projects in

County and municipalities, with priority area/projects and preliminary design concepts.

This report also meets several goals stated in the Caroline County 2010 Comprehensive Plan, specifically those found in Chapter 2, Part III titled “Initiate ESD (Environmental Site Design) and LID (Low Impact Development) Demonstration Projects on County Properties.” (p. 106-107). These passages discuss the opportunities for ESD stormwater retrofits on County-owned property, including County public schools.

In addition to meeting the stated goals above, this report also fulfills several strategies identified in the 2010 Upper Choptank River Watershed Based Plan, most importantly:

Section C – “Developed land is the second largest source of pollutants, and strategies to reduce loads from this source will be focused on stormwater retrofit projects that incorporate regenerative stormwater system techniques, to be located primarily on county and municipal properties.” (p. 14)

2.0 Methodology

An initial meeting was held with representatives of CCPS, CCDPC, and AECOM in August 2016 to review the grant application and develop the overall goals of the project. A representative from the University of Maryland Sea Grant Extension Program (MDSG) subsequently became involved. The main objective of the project was determined to be the prioritization of stormwater best management practices (BMP’s) at each site. A secondary consideration was stated to be opportunities to coordinate project implementation with the mission of the MDSG Strategic Plan 2014- 2017 such as creating a scientific foundation for environmental management focused on ecosystem preservation and the reduction of nutrients and sediment inputs that lead into the Chesapeake Bay. The meeting also gave CCPS facilities personnel the opportunity to describe existing conditions and identify any existing stormwater issues at each of the sites. It was agreed that any BMP’s which could also help mitigate existing issues would be a bonus for the project.

Two of the original 10 schools were dropped from further consideration. CCPS officials notified AECOM about the future demolition and reconstruction of Greensboro Elementary School. Thus any water quality retrofit projects at this location would likely be demolished in coming years resulting in inefficient expenditures. Also, a major renovation had just been completed at Preston Elementary School which included many water quality measures. CCPS officials believed that the renovation complied with Maryland Environmental Site Design (ESD) principles and therefore additional controls were not warranted.

The remaining schools / centers that were evaluated in this report are as follows:

Colonel Richardson Middle and High School Denton Elementary School Federalsburg Elementary School Lockerman Middle School North Caroline High School and Caroline Career & Technology Center Ridgely Elementary School Two of these locations, Colonel Richardson Middle and High School and Federalsburg Elementary School are in the Lower Choptank watershed while the remaining sites are within the Upper Choptank watershed. This is important as each watershed has separate pollutant loading rates as will be further explained in the Preliminary BMP Sizing section.

AECOM used three approaches simultaneously to develop concept-level water quality retrofits:

Desktop exercise – using GIS, an analysis of topography, soils, ground water elevations, buildings, driveways, parking lots, streams, and rivers was performed for each site. The GIS data was collected from CCDPC, and open sources such as Natural Resource Conservation Service (NRCS) and the Maryland’s Mapping & GIS Data Portal.

Field visits – AECOM personnel visited each campus on two occasions to identify drainage patterns and investigate opportunities for water quality retrofits. During the site visits, field notes and photographs were taken to document existing conditions. Emphasis was placed on opportunities to treat currently untreated impervious surfaces and assessing whether downspouts from roof gutters were tied into underground piping systems or discharged to the surface.

Plan review – site and roof plans were requested from CCPS for each school.

These were used to confirm field observations and help determine drainage patterns and runoff flow paths.

Site and roof plans were not available for every school and field visits were more heavily relied upon in these instances. Specific plan availability is described in the School Site Assessments section. Once drainage patterns were determined or approximated, ArcGIS was used to delineate subwatershed or catchment areas draining to locations of potential future BMPs or in some cases, those that already exist.

3.0 Guiding Principles

AECOM sought to apply measures in accordance with the Maryland Environmental Site Design (ESD) Process and Computation guidance document which specify micro-scale practices. After review of the design requirements and application restrictions of the range of ESD options, it was determined that five practices would be most applicable to the subject schools: disconnection of a rooftop runoff, disconnection of a non-rooftop runoff, landscape infiltration, micro-bioretention, and swales. These BMPs were selected because of their pollutant removal capabilities and opportunity to be used in retrofit (as opposed to new design) circumstances. This list was expanded to include permeable pavement at the request of CCPS and CCDPC but for use at only one location where parking improvements are currently being considered.

It was subsequently found that two of the ESD measures were not viable in these situations. First, disconnection of a non-rooftop runoff could not be used due to the very small drainage area limitation as stipulated in the guidance document of just 1,000 square feet. Second, swales are generally intended for use in long, linear applications such as roadways and not in retrofits. Of the remaining ESD measures, disconnection of a rooftop runoff can only be applied at downspout locations of which only a few were found to be feasible due to lack of sufficient downhill pervious area .

Therefore, this report focused on the application of infiltration and bio-retention at most locations.

All the identified treatment areas were assessed in comparison to the ESD requirements in order to determine which strategies were most appropriate at each location. Criteria that were assessed included ground slopes, setbacks from building and wells, maximum drainage area, depth, groundwater elevation, and hydrologic soil groups. Descriptions of soil types found at each location as well as summaries of hydrologic soil groups are provided in Appendix A.

It was found that few ESD measures could be applied in complete accordance with the guidance due mostly to the maximum drainage area restrictions of ESD practices which are defined by the State to be the use of “small-scale” practices as well as lack of space to actually place BMPs (such as narrow grassed areas between parking lots).

Site designers have flexibility when designing new facilities or the redevelopment of existing facilities to set drainage area patterns and sizes and thus can add ESD measures fairly easily. The schools and parking areas around them assessed for this report exist and drainage cannot be altered without significant effort and demolition to provide additional space was considered impractical. Therefore, in order to achieve a wider variety of BMP opportunities, AECOM, in consultation with CCPS and CCDPC, adjusted the maximum drainage area restrictions. Since these BMPs are being considered in locations where no new construction or redevelopment is taking place, it was agreed that some flexibility should be applied to the ESD requirements. It is noted that the ESD guidance document does allow for larger infiltration areas and thus larger drainage areas than would otherwise be permissible when pretreatment forebays can also be provided.

Infiltration is generally considered a preferred practice over micro-bioretention due to the resulting replenishment of groundwater, but can only be used in locations with highly permeable soils and low groundwater elevations. On-site testing was outside of the scope of this report but generalized mapping is available from the NRCS. Based on this mapping, soils at each school location appear to be relatively well-drained.

However, high groundwater may negate the use of infiltration at each school site with the exception of Ridgely Elementary School which appears to have lower groundwater elevations. Since site-specific soil testing could result in establishing the feasibility of infiltration at other locations, both infiltration and bioretention are being shown at all locations (except for rooftop disconnect and permeable pavement), for the purpose of this report.

The other two BMPs evaluated as part of this study were disconnection of rooftop runoff, which involves discharging downspouts onto grassed surfaces as opposed to routing them underground into piping systems, and permeable pavement, which is specially-designed asphalt or concrete blocks that allow water to seep through the material to the ground below.

The ESD concept is predicated on using soil types and proposed site imperviousness to determine the amount of rainfall (or target PE) that would need to treated in order for the proposed practice to replicate runoff conditions on a wooded site. In other words, if an ESD measure was designed, constructed, and maintained properly, the pollutant amount in post-treated runoff would be same as would have existed in the pre-developed, natural state which is assumed to have been wooded.

PE varies by soil type and percent imperviousness of the drainage or catchment area.

While site (or in these instances catchment area) imperviousness was determined with a reasonable level of certainty, soil types were based on mapping which is generalized making precise determination of PE difficult. For this report, PE was set at 2.0 inches which is the rainfall amount that would need to be captured by a 60% impervious surface in “A” type soils or a 65% impervious surface in “B” type soils which was fairly indicative of the situations encountered at each site.

4.0 School Site Assessments

Each school’s campus evaluation includes the following:

• Written description of existing conditions, availability of plans, and discussion of potential BMPs. Historical perspective was developed in part from the Caroline County Board of Education & Vitech Consulting Services report entitled 2015 Educational Facilities Master Plan Caroline County Public Schools.

• Aerial photographs with potential or existing BMP locations and associated drainage or catchment areas shown. Existing treatment areas are identified by “ETA” and proposed treatment areas by “PTA” in the exhibits.

• Spreadsheets with preliminary BMP sizes, approximate costs, loading rates for total nitrogen (TN), total phosphorous (TP), and total suspended solids (TSS), and TN, TP, and TSS reductions resulting from the BMPs. See below for further explanation.

• Site photographs and descriptions showing many of the BMPs.

The basis for the spreadsheets for each school is found in Appendices B and C.

Appendix B includes total nitrogen (TP), total phosphorous (TP), and total suspended solids (TSS) loading rates which were taken from a spreadsheet developed by the Maryland Department of Natural Resources and provided by MDSG. As previously noted, four of the six locations are in the Upper Choptank watershed while the remaining two are in the Lower Choptank watershed. Delivered loading rates were used in favor of edge of stream loading rates.

Appendix C provides a detailed explanation of the development of pollutant removal rates for each type of BMP in both watersheds as well as costs over a 20-year time frame and cost per pound TN, TP, and TSS removed.

The spreadsheets begin with the impervious area draining to the potential BMP locations (column (a)). The surface areas of practice needed in column (b) are calculated by multiplying the impervious areas by the percentages from column (a) in Appendix C2 or C3. Approximate costs over a 20-year life span in column (c) are calculated by multiplying the impervious areas by the costs provided in Appendix C5.

The TN, TP, and TSS loading rates in columns (d), (e), and (f) are the impervious areas multiplied by the rates provided in Appendix B. Finally, the TN, TP, and TSS reductions in columns (g), (h), and (i) are the loading rates multiplied by the percent reductions found in columns (c), (d), and (e) in Appendices C2 and C3. Note that while the costs are based on 20-years, the load reductions are annual.

ETAs represent areas that are already being treated by BMPs. In some cases, these are designed infiltration or bioretention features but in others, specifically downspouts which have been in place for years or decades and discharge to the surface, are presumed to be unintentional. Regardless, these have been accounted for separately as load reductions already occurring.

Denton Elementary School

The school was built in 1976 with a building square footage of 80,850 square feet. In 1995, the school was renovated and an additional 1,160 square foot pre-k classroom was added bringing the total building square footage to the current 82,010 square feet. AECOM estimated the total area of parking lots to be 74,776 square feet, making the impervious area total 156,786 square feet or 3.60 acres. The building sits on 20.04 acres of land. Based on these estimates, the site is about 18% impervious. See Exhibit A2. Two tributaries to the Choptank River, one to the east and the other to the south, exist several hundred feet from the site.

CCPS provided a roof plan for the school but a site plan was not available.

Potential BMPs are as follows:

• BMPs D.1, D.2, and D.4 – Most parking areas drain into a piping system which flows towards the south and presumably into the storm sewer system within Lupine Lane. The existing inlets could be modified with BMPs placed in the grassed areas.

• BMP D.3 – Appears to drain to a concrete chute which then drains into an inlet within Sharp Road. The chute could be removed such that a BMP could be placed.

• BMP D.5 – Roof downspouts from the school generally discharge into an enclosed piping system but downspouts from the eastern side of the school discharge to the surface and represent existing treatment.

Each of these BMPs fall within the mapped CdA-A soil group, Cedartown loamy sand on flat slopes. This soil should be fairly porous but depth to groundwater could limit the use of infiltration.

The potential and existing BMPs and their associated pollutant removal estimates are summarized below:

Impervious area (ft²)

Approximate Cost ($ over 20 year life span)

TN reduced (lbs/yr)

TP reduced (lbs/yr)

TSS reduced (lbs/yr)

Potential BMPs 57,850 $104,210 9.33 1.11 533 Existing BMPs 13,600 - 1.10 0.13 63

Sabre Building, Suite 300 4051 Ogletown Road Newark, DE 19713

Legend

Site

Potential Treated Area

Potential BMP

Project Number:

Date:

Exhibit:

POTENTIAL AND

EXISTING BMPs

Denton Elementary School

11/16/2016

A2

Existing Treated Area Existing Rooftop Disconnect

Water Quality Retrofits

Prioritization and Implementation

Plans for Caroline County

Public Schools

60507648

Existing Inlet

LUPINE

CdA - A

KgB - A/D

EwA - B

EwA - B

HvA - A/D

DRAINAGE AREA 3

BMP-PTA-D.3

DRAINAGE AREA 4

BMP-PTA-D.4

DRAINAGE AREA 5

BMP-ETA-D.5

DRAINAGE AREA 1

BMP-PTA-D.1

DRAINAGE AREA 2

BMP-PTA-D.2

SHARP ROAD

LU

P

IN

E

L A

N E

TR

IC

E M

EAD

O W

S C

IR

C

LE

Impervious area (ft²)

Surface area of practice needed

(ft2)

Approximate Cost ($ over 20 year life span)

TN Loading Rate (lb/yr)

TP Loading Rate (lb/yr)

TSS Loading Rate (lb/yr)

TN reduced (lbs/yr)

TP reduced (lbs/yr)

TSS reduced (lbs/yr)

(a) (b) (c) (d) (e) (f) (g) (h) (i)

Drainage Area 1 BMP-PTA-D.1

Landscape infiltration 10,650 1,065 $19,400 2.50 0.25 114 1.72 0.20 98 Micro-bioretention 10,650 1,420 $18,950 2.50 0.25 114 1.71 0.20 98

Drainage Area 2 BMP-PTA-D.2

Landscape infiltration 13,100 1,310 $23,900 3.08 0.31 140 2.12 0.25 121 Micro-bioretention 13,100 1,747 $23,310 3.08 0.31 140 2.11 0.25 120

Drainage Area 3 BMP-PTA-D.3

Landscape infiltration 20,400 2,040 $37,200 4.79 0.49 218 3.30 0.39 189 Micro-bioretention 20,400 2,720 $36,290 4.79 0.49 218 3.28 0.39 188

Drainage Area 4 BMP-PTA-D.4

Landscape infiltration 13,700 1,370 $25,000 3.22 0.33 147 2.21 0.26 127 Micro-bioretention 13,700 1,827 $24,370 3.22 0.33 147 2.20 0.26 126

Totals

Potential BMPs 57,850 - $104,210 - - - 9.33 1.11 533

Drainage Area 5 BMP-ETA-D.5

Disconnection of rooftop runoff 13,600 60 ft. flow path - 3.19 0.32 146 1.10 0.13 63

Totals

Existing BMPs 13,600 - - - - - 1.10 0.13 63

Denton Elementary School Potential BMPs and Load Reduction Estimates

Upper Choptank Watershed

Denton Elementary School Site Photographs

BMP D.3 – concrete swale could be removed, inlet modified, and feature excavated in open space

BMP D.5 (existing) – rooftop downspouts already disconnected Other downspouts with too large a drainage area

5.0 Summary

A concept-level assessment such as this report necessitates the application of generalized information. In this instance, the following were used:

• Simplified equations from the Maryland Environmental Site Design (ESD) Process and Computation guidance document which resulted in estimated sizes of infiltration and bio-retention areas based on the contributing drainage area.

• Budgetary costs from the Costs of Stormwater Management Practices in Maryland Counties (Draft Final Report) prepared for the Maryland Department of the Environment by the University of Maryland Center for Environmental Science dated October 2011 which resulted in cost estimates also based on the contributing drainage area.

• Percentage pollutant removal rates from Recommendations of the Expert Panel to Define Removal Rates for Urban Stormwater Retrofit Projects dated January 20, 2015 prepared by the Chesapeake Stormwater Network (CSN) which relied on the runoff depth captured per impervious acre which, as shown in Appendix C, is a function of the simplified equations from the ESD guidance.

The one factor that does vary is pollutant loading rates. Those rates are lower in the Lower Choptank watershed for TN but higher for TSS. Since cost estimates do not vary by loading rates, this results in higher per pound removed costs for TN in the Lower Choptank watershed and lower per pound removed costs for TSS. TP loading rates are the same for both watersheds.

Finally, using the assumptions previously stated for infiltration and bio-retention depths, the cost differentials between the two are negligible.

Due to the relationship of all these factors with each other, the cost per pound removed, often used to prioritize individual projects, is the same for all infiltration uses and all bio-retention uses within each watershed. Therefore, priorities need to be established using other criteria.

These are offered in the Recommended Future Tasks section.

If all of the potential BMPs depicted in the exhibits and spreadsheets were implemented, the 20-year costs would be approximately $730,000 and would result in the removal of 53 pounds of nitrogen, 6.7 pounds of phosphorous, and 3,825 pounds of total suspended solids.

Existing BMPs were estimated to be resulting in the removal of 8.9 pounds of nitrogen, 1.1 pounds of phosphorous, and 646 pounds of total suspended solids.

6.0 Recommended Future Tasks

This study established the feasibility of placing stormwater BMPs at eight schools at six locations and estimated costs and pollutant load reductions. Several steps would need to be taken to progress into design and construction as follows:

One of this report’s objectives is to help meet Chesapeake Bay WIP milestones. As explained in the Summary section, costs on a per pound removed basis are higher for TN in the Lower Choptank watershed but higher for TSS. CCDPC may need to decide which constituent is most important as this will be a factor in prioritizing.

Since costs per pound of TN, TP, or TSS removed do not vary from site to site within the same watershed, CCPS should review the potential locations and decide which would be best from an operational standpoint. MDSG may want to provide input regarding how these locations could facilitate learning opportunities at each school.

Once a list of preferred BMPs is established, additional effort would be needed to confirm the areas draining to each as well as ground slopes (for rooftop runoff disconnection). Also CCPS will need to find the locations of water wells and septic tanks as well as underground utilities. The BMPs described herein have various setback requirements that would need to be factored in. Conflicts could result in BMPs being dropped from further consideration.

Soil testing would then be needed at the remaining BMPs. As previously stated, infiltration is the preferred option over bioretention. However, based on soil mapping, poorly draining soils and / or high groundwater elevations may exclude the use of infiltration at some locations. Also, as explained in the Guiding Principles section, forebays may be needed at some infiltration locations. Surveying of each location would be needed in order to develop construction plans.

Finally, construction plans taking into account requirements and limitations as stipulated in the Maryland Stormwater Design Manual , Volumes I and II dated October 2000 and Revised May 2009, would need to be prepared. It is assumed that CCDPC would self-permit the projects.

Appendices

Appendix A

Soil Types and Summaries of Hydrologic Soil Groups

Map Unit Soil Type Soil Type Properties and Qualities

Slope: 2 to 5 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Somewhat excessively drained Runoff class: Low Capacity of the most limiting layer to transmit water (Ksat):

Moderately high to high (0.57 to 5.95 in/hr) Depth to water table: About 40 to 72 inches Frequency of flooding: None Frequency of ponding: None Available water storage in profile: Low (about 3.8 inches)

Slope: 0 to 2 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Poorly drained Capacity of the most limiting layer to transmit water (Ksat):

Moderately high to high (0.57 to 1.98 in/hr) Depth to water table: About 0 to 10 inches Frequency of flooding: None Frequency of ponding: Occasional Salinity, maximum in profile: Nonsaline to very slightly saline (0.0 to 2.3 mmhos/cm) Available water storage in profile: Moderate (about 8.8 inches)

Slope: 0 to 2 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Well drained Runoff class: Very low Capacity of the most limiting layer to transmit water (Ksat):- Moderately high to high (0.20 to 1.98 in/hr) Depth to water table: About 42 to 72 inches Frequency of flooding: None Frequency of ponding: None Available water storage in profile: Moderate (about 7.9 inches)

Slope: 2 to 5 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Well drained Runoff class: Low Capacity of the most limiting layer to transmit water (Ksat):

Moderately high to high (0.20 to 1.98 in/hr) Depth to water table: About 40 to 72 inches Frequency of flooding: None Frequency of ponding: None Available water storage in profile: Moderate (about 7.9 inches)

HbB – B Hambrook sandy loam

HbA – B Hambrook sandy loam

Hydrologic Soil Group

CdB – A Cedartown loamy sand

FadA – B/D Fallsington sandy loams

Map Unit Soil Type Soil Type Properties and Qualities

Hydrologic Soil Group

Slope: 0 to 2 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Well drained Runoff class: Negligible Capacity of the most limiting layer to transmit water (Ksat):

Moderately low to high (0.06 to 5.95 in/hr) Depth to water table: About 40 to 72 inches Frequency of flooding: None Frequency of ponding: None Available water storage in profile: Moderate (about 6.6 inches)

Slope: 2 to 5 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Well drained Runoff class: Very low Capacity of the most limiting layer to transmit water (Ksat):

Moderately low to high (0.06 to 5.95 in/hr) Depth to water table: About 40 to 72 inches Frequency of flooding: None Frequency of ponding: None Available water storage in profile: Moderate (about 6.6 inches)

Slope: 0 to 2 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Well drained Runoff class: Very low Capacity of the most limiting layer to transmit water (Ksat):

Moderately low to high (0.06 to 5.95 in/hr) Depth to water table: About 40 to 72 inches Frequency of flooding: None Frequency of ponding: None Available water storage in profile: Moderate (about 6.9 inches)

Slope: 0 to 2 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Well drained Runoff class: Low Capacity of the most limiting layer to transmit water (Ksat):

Moderately high to high (0.57 to 1.98 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Available water storage in profile: Moderate (about 7.8 inches)

Source: NRCS Soil Survey for Caroline County

IgA – A Ingleside sandy loam

SaB – B Sassafras sandy loam

Ingleside loamy sandIeA – A

IeB – A Ingleside loamy sand

Groups Descriptions

A Soils having a high infiltration rate (low runoff potential) when thoroughly wet.

These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission.

B

Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission.

C

Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission.

D

Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission.

Source: NRCS Soil Survey for Caroline County

Soil Type Classifications

Attachment 3

General Description of the BMPs and Requirements

The project will include construction of the following BMPs:

• Approximately 21,740 square feet of bioretention –– These six excavated areas will intercept, infiltrate, and treat up to 57,850 square feet of impervious area from their combined drainage areas. These bioretention areas will be planted with native types of vegetation, which have nutrient removal, habitat for pollinator, and water conservation benefits. By decreasing surface runoff through infiltration, the site’s impervious cover will have less of an impact on the nearby tributaries to the Choptank River, including reductions in nutrients entering the stream system.

The area in which bioretentions labeled BMP-BR-2 in Attachment 1 frequently floods and shall be designed to convey the 2 year storm event

• 9,220 square feet of permeable pavement –– Two rows of parking stalls (approximately 68 parking spaces) will be replaced with the PowerBlock Permeable Pavement System, “or equal.” to infiltrate stormwater before it enters the stormwater system or enters the tributaries of the Choptank River as runoff.

• 4,710 square feet of conservation landscaping “Living Classroom” –– The conservation landscaping exact location at the school is yet to be determined. The successful bidder shall attend engagement meetings to determine the exact location. Students will be involved in the design and planting of the conservation landscaping area, and the area can function as a living classroom.

• 36,275 square feet (0.83 acres) of tree planting –– An unused grass area will be planted with native trees. The grass area is contiguous with the existing forest stand and is located outside of the footprint of the sports playing fields. This will increase the size of the forest patch immediately south of the property, which will provide valuable habitat for local wildlife.

• Revegetation – Areas to be planted using Conservation Landscaping and Tree

Planting should be identified on a separate plan and handled in conjunction with stabilizing the remainder of the property and other disturbed soil areas. Areas not part of the Conservation Landscape should immediately be seeded with an appropriate warm-season grass mix and mulched with tacked or crimped straw or with the use of an approved hydro-mulch. When planting any of these areas excessive compaction should be avoided as not inhibit plant growth.

***Plantings within the bioretention, conservation landscape area and tree plantings may be assisted by volunteers through the school or other community events.***

The successful bidder shall obtain geotechnical and survey of the site. The geotechnical and survey shall be conducted when school is not in session. The school calendar can be found at 2023-2024_1-pg_Calendar_English.pdf (s3.us-east-1.amazonaws.com). If the required must be done when school is in session the successful bidder shall coordinate with the School to find an appropriate time and date for such work. The survey and geotechnical shall be performed in accordance with local and state requirements.

https://core-docs.s3.us-east-1.amazonaws.com/documents/asset/uploaded_file/3042/CCPS/3669660/2023-2024_1-pg_Calendar_English.pdf

Attachment 4

Denton Elementary Existing Site Plans