FINAL REPORT Stormwater Retrofit Opportunities on Public Lands in Fluvanna County

Transcription

1 FINAL REPORT Stormwater Retrofit Opportunities on Public Lands in Fluvanna County NOVEMBER 2010 PREPARED BY: Center for Watershed Protection 8390 Main Street, 2 nd floor Ellicott City, MD SUBMITTED TO: Rivanna River Basin Commission and Fluvanna County, VA 1

2 Acknowledgments The project team from the Center for Watershed Protection (CWP) would like to acknowledge the significant contributions from Leslie Middleton, Executive Director of the Rivanna River Basin Commission (RRBC) and Darren Coffey, Fluvanna County Planning Director and RRBC Technical Advisory Committee member. Each provided coordination, guidance, and insight that allowed this project to be successful. We also received invaluable assistance in planning and carrying out this study from the following: John Gooch, Fluvanna County Board of Supervisors; Rivanna River Basin Commission John Robins, Engineer, Fluvanna County Marvin Moss, Rivanna River Basin Commission Matt Weaver, Planner, Fluvanna County Maurice Carter, Assistant Superintendant of Schools, Fluvanna County Mozell Booker, Fluvanna County Board of Supervisors Nicola McGoff, Program Coordinator, RRBC Pat Groot, Grants Administrator, Fluvanna County Richard Collins, Rivanna River Basin Commission Roger Black, E&S Inspector, Fluvanna County; RRBC Technical Advisory Committee Steve Tugwell, Planner, Fluvanna County The CWP project team consisted of the following individuals: David Hirschman Laurel Woodworth Joe Battiata Bill Stack Terri Hoselton We are grateful to the Rivanna River Basin Commission for funding this project through an EPA Chesapeake Bay Program grant from the National Fish and Wildlife Foundation (NFWF), Grant # NFWF Disclaimer: The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the opinions or policies of the U.S. Government or the National Fish and Wildlife Foundation. Mention of trade names of commercial products does not constitute their endorsement by the U.S. Government or the National Fish and Wildlife Foundation. Stormwater Retrofit Opportunities on Public Lands in Fluvanna County i

3 Executive Summary This project, initiated by the Rivanna River Basin Commission (RRBC), investigated several public sites in Fluvanna County to develop concepts for better stewardship of stormwater runoff. In particular, the project looked at ways to implement stormwater retrofits. Stormwater retrofits are practices that reduce, intercept, treat, and cleanse polluted runoff from existing parking lots, rooftops, and turf areas on already developed sites. Stormwater retrofits on public lands in Fluvanna County can achieve several objectives: Allow the County to lead by example and demonstrate the kinds of practices desired for other public and private sites. Alleviate existing runoff problems, such as erosion and pollution of downstream waterways. Educate the public about proper stewardship of water resources. Help the County with future compliance of pending regulatory programs, such as the Chesapeake Bay TMDL. The RRBC has a keen interest in promoting improved stormwater management within its partner jurisdictions. Within the Rivanna Basin, retrofit inventories, concept plans, or implementation have taken place in the City of Charlottesville and Albemarle County, and a similar study is underway in Greene County. In Fluvanna County, the following properties were selected for stormwater retrofit inventories: Central Elementary School Fluvanna High School Village of Palmyra (near the Courthouse and administrative buildings) The majority of the Central Elementary School property lies in the Cary s Creek watershed and the majority of the High School property is within the Raccoon Creek watershed. Both of these streams flow into the Rivanna River, while runoff from the village of Palmyra flows directly into the Rivanna River. The retrofit inventories involved a detailed field investigation at each site, taking appropriate measurements, and developing concept (sketch) plans. Twenty retrofit concepts were drafted during the field assessment phase. Subsequent to the field work, the Center for Watershed Protection (CWP) reviewed all the field forms, added additional information, and prioritized all of the candidate retrofit projects based on four criteria: 1. Total Phosphorus Removed This is a basic indicator of how much stormwater is treated and how effective the retrofit practice is at removing pollutants from runoff. 2. Cost Effectiveness This important concept reveals the most effective proposed practices that can be built for the least cost. In this case, the projects were scored based on construction costs per pound of phosphorus removed by the retrofit. Stormwater Retrofit Opportunities on Public Lands in Fluvanna County ii

4 3. Visibility and Outreach Since a major objective of the grant is to promote stormwater management and stewardship, this factor was included to assess the relative visibility of the various projects and their potential to serve as learning environments. 4. Opportunity and Interest This factor gages the likelihood that a practice will actually be built based on the interest level among County staff and elected officials, timing with other planned improvements, and opportunity to address several problems at once. Based on these factors, each site was scored on a 100 point scale. Several of the high ranking retrofit projects included: Installing bioretention within the medians of several parking lots at Fluvanna High School. Bioretention is a system of soil and plants designed to capture and treat runoff. Installing bioretention and planting trees at the playground at Central Elementary in order to reduce an existing erosion problem and provide shade and beautification. Planting trees to prevent erosion and reduce mowing on grass slopes at Fluvanna High School. After all the projects were initially ranked, a meeting was held with County and schools staff, as well as elected officials, to review the results of the ranking, and re prioritize some of the projects based on input from the attendees. This report represents the final ranking of retrofit projects. The report also provides recommendations on implementing the retrofit projects. In some cases, implementation may just be a matter of changing management practices (such as not dumping mop water into storm drains or doing a better job of managing waste around dumpsters). These types of changes can be made in the short term with few additional resources. In other cases, implementation will mean funding and constructing actual stormwater management structures. Implementation can be achieved through grant programs, using volunteer labor and donated materials, and by cooperating regionally with watershed improvement efforts. Stormwater Retrofit Opportunities on Public Lands in Fluvanna County iii

5 Table of Contents Executive Summary...ii Section 1. Project Background...1 Section 2. Inventory Protocol...1 Section 3. Summary of Concepts Identified...6 Section 4. Evaluation and Ranking of Retrofit Concepts...7 Section 5. Maintenance Considerations...13 Section 6. Recommendations for Retrofit Implementation and Delivery...18 References...19 Appendix A: Retrofit Reconnaissance Inventory Form (Modified) Appendix B: Common Retrofit Locations Appendix C: Retrofits Summary Table Appendix D: Scoring and Ranking Criteria and Retrofit Concepts Ranking Table Appendix E: Retrofit Concepts by Property Maps, Photos, Visualizations, and Field Forms Appendix F: Regenerative Stormwater Conveyance Description Stormwater Retrofit Opportunities on Public Lands in Fluvanna County iv

6 Section 1. Project Background The Rivanna River Basin Commission (RRBC) received funding from the National Fish and Wildlife Foundation to accelerate the adoption of advanced stormwater best management practices (BMP) throughout the Rivanna watershed, specifically those that will reduce the volume of stormwater runoff as well as reduce the amount of sediment and nutrients (nitrogen and phosphorous) to area streams. In support of that effort, the Center for Watershed Protection s (CWP) Charlottesville, VA office led an inventory of potential stormwater BMP retrofits on developed properties owned by Fluvanna County, such as schools and administrative building locations. The survey was completed by CWP, county staff, and RRBC members and staff in July A stormwater retrofit inventory provides an opportunity to look at the landscape, analyze how it changed as properties were developed, and imagine how it can be modified to better manage the flow of water that runs off it and to local streams. This is not just an academic exercise. Runoff from existing developed properties is a major source of pollutants and increased storm flow that leads to the erosion of stream banks and degradation of waterways. Controlling this type of runoff is also the goal of evolving regulatory programs at the state and federal levels, such as the Chesapeake Bay TMDL. Beyond these purposes, stormwater retrofits also foster innovation and create excitement in a community and are often used for educational purposes. People become excited about taking simple actions to promote clean water and to green up school campuses, parks, and other public buildings. Often, a few stormwater retrofits on public land can shift the way that stormwater is managed across the entire community, with developers and even homeowners adapting ideas to their own uses. It is in this spirit that the retrofit inventory was undertaken in Fluvanna County. Field teams consisting of CWP staff, RRBC staff and commissioners, and Fluvanna County staff and elected officials fanned out across three public sites in July, The teams investigated how to use the landscape to reduce, capture, and filter runoff that otherwise flows directly to nearby streams and the Rivanna River. This report describes this field process and the analysis that followed. Section 2. Inventory Protocol In Fluvanna County, CWP worked with County staff to identify three public properties prior to field work as sites to inventory for this project. The following properties were selected, due to their public ownership and relative availability of space for retrofits. Central Elementary School Fluvanna High School Village of Palmyra (near the Courthouse and administrative buildings) The majority of the Central Elementary School property lies in the Cary s Creek watershed and the majority of the High School property is within the Raccoon Creek watershed. Both of these streams flow into the Rivanna River, while runoff from the village of Palmyra flows directly into the Rivanna Stormwater Retrofit Opportunities on Public Lands in Fluvanna County 1

7 River. Using geographic information systems (GIS) data provided by the County, CWP staff created field maps with recent aerial images, roads, topography, and streams. These maps were used to identify the specific drainage areas of each potential retrofit and to make note of details, such as the direction of flow and discharge points for runoff. Field work was conducted on July 26, After a brief indoor training about the inventory methods, the survey group was divided into three teams to conduct field work for the rest of the morning. Field work participants included RRBC staff and commission members, Fluvanna County staff, and CWP staff. Each team was led by a CWP staff person experienced with stormwater retrofitting. Figure 1 shows some representative photos from the fieldwork. Figure 1. Typical Retrofit Field Work Examples from Central Elementary School: Top Left Completing field form for potential rain garden retrofit. Top Right Inspecting erosion at the playground. Bottom Left Analyzing existing drainage pathways in the front parking lot. Bottom Right Surveying condition of an existing detention pond. A wide variety of stormwater management retrofit options were considered while inventorying these public properties. Figure 2 shows examples and descriptions of the types of stormwater practices that were considered as options for retrofitting these properties. Using a modified version of the Retrofit Reconnaissance Inventory (RRI) field form developed by CWP (Appendix A), the teams evaluated the stormwater retrofit potential of each candidate site by analyzing existing drainage patterns, drainage areas, impervious cover, available space, and site constraints (e.g., conflicts with Stormwater Retrofit Opportunities on Public Lands in Fluvanna County 2

8 existing utilities and land uses, site access, and potential impacts to natural areas). Unless there were obvious site constraints and/or evidence that a particular stormwater retrofit would offer few or no watershed benefits, a stormwater retrofit concept was developed for each candidate project site, including a sketch plan when appropriate. Each stormwater retrofit concept design was based on the size and particular layout of the site, the size of the drainage area to be treated, and the land use and amount of impervious cover within the drainage area. The size and land cover (i.e., impervious, turf, or forest) of the contributing drainage area for each retrofit dictates how much runoff, or Treatment Volume (Tv), the practice should be designed to capture. For this study, CWP assumed that each stormwater retrofit should be sized to capture and treat the runoff generated by 1 inch of rainfall in the contributing drainage area 1. In general, not all retrofits can meet this sizing threshold due to available land area and site constraints. However, the standard represents a consistent criterion by which to evaluate candidate retrofit projects. The Treatment Volume (Tv) for a given stormwater retrofit is calculated as: Tv = P (Rv I * %I + Rv T * %T + Rv F * %F)* A / 12in Where: Tv = Runoff Reduction Treatment Volume (in cubic feet) P = Water quality design storm rainfall depth (1 in this case) Rv I = runoff coefficient for impervious cover (0.95) Rv T = runoff coefficient for turf or disturbed soil cover (0.22 in clay soils) Rv F = runoff coefficient for forest cover (0.04 in clay soils) %I = % of site in impervious cover (as fraction) %T = % of site in turf or disturbed soil cover (as fraction) %F = % of site in forest cover (as fraction) A = Drainage area (square feet) After field work was completed, CWP staff reviewed all field forms for completeness and compiled the data for each retrofit concept into a combined spreadsheet. This allowed evaluation of each retrofit to determine the nutrient and runoff reduction capabilities, planning level cost, cost efficiency, educational value, and feasibility of construction for each. See Section 4 and Appendix D for more information about this evaluation process. Field forms for each retrofit concept can be found in Appendix E, along with photos and maps of the project locations. More detail on conducting the Retrofit Reconnaissance Inventory can be obtained directly from the guidance manual, Urban Stormwater Retrofit Practices (CWP, 2007). This publication contains extensive information on identifying and evaluating potential retrofit locations within a subwatershed (see Appendix B), as well as profile sheets on individual retrofit designs and guidance on construction, maintenance, and costs. 1 The 1 inch rainfall is the depth of capture for the Water Quality Volume in Virginia s new proposed stormwater regulations, so this standard was used as a forward looking approach for sizing the retrofits in Fluvanna County. Stormwater Retrofit Opportunities on Public Lands in Fluvanna County 3

9 Figure 2. Examples of Stormwater Management Practices Bioretention or Landscaped practice that uses plants, mulch, and soil Bioswale to treat runoff. Most have underdrain pipes to ensure water only ponds temporarily. Common in parking lot islands and edges and as part of commercial site plans. Rain Garden Similar to bioretention/bioswale, but generally smaller and less expensive. Designed to treat runoff from rooftops, driveways, and yard areas. To keep design and construction simple, underdrains and gravel are not generally used. Dry Swale Infiltration Impervious Disconnection Stormwater Planter Also similar to bioretention/bioswale. Main difference is that the dry swale has a longitudinal slope to fit site conditions and may be narrower than typical bioretention. Sometimes check dams are used to slow water down and create temporary ponding cells. Infiltration practices use temporary surface or underground storage to allow incoming stormwater runoff to infiltrate into underlying soils. These practices are suitable for use in areas where measured soil permeability rates exceed 1/2 inch per hour. Therefore, these are most commonly used in coastal plain areas with sandy soils. Disconnecting rooftop or other impervious surfaces so that runoff goes through vegetated areas instead of directly to storm sewer, driveway, parking lot, etc. Can be simple disconnection to grass (as shown in photo), or disconnection to rain garden, rain barrel, or soil amended area. Stormwater planters (also known as vegetative box filters or foundation planters) take advantage of limited space available for stormwater treatment by placing a soil filter in a container, often along buildings at the bottom of roof downspouts. Rainwater Harvesting Collection of rooftop water in tank or cistern for later use for outdoor or indoor applications, including irrigation, washing, cooling systems, toilet flushing, laundry, etc. Cisterns can be above ground or underground. Stormwater Retrofit Opportunities on Public Lands in Fluvanna County 4

10 Figure 2. Examples of Stormwater Management Practices Permeable Pavement Pavement made from permeable materials, such as interlocking paver blocks, permeable concrete, and permeable asphalt. Storage for runoff is provided below pavement surface in a stone or gravel layer, and water either infiltrates into the ground or drains out slowly through underdrain pipes. Extended Detention Basin Pond or basin that achieves 12 to 24 hour detention of stormwater runoff after each rain event. Its small outlet restricts stormwater flow so that it is stored within the basin. The temporary ponding enables sediment to settle out and slows down the discharge of runoff, thereby reducing erosion downstream. Re Vegetation / Tree planting Vegetating turf areas with trees and shrubs to restore water retention capacity and provide other services, such as shade and habitat. In some cases, soil amendments are needed prior to re vegetation. Deep tilling, or sub soiling, of soil prior to planting can also greatly improve infiltration. Outfall Protection Adding stone, rip rap, plunge pools, check dams, or vegetated conveyance channels to pipe outfalls that are eroding and causing damage to receiving streams. Regenerative Stormwater Conveyance (for Outfall Protection) 2 (Photo by: Keith Underwood) Pollution Prevention Linear open channel systems used at stormwater outfalls that convey and treat stormwater runoff in a stable manner. A series of shallow pools, an underlying sand bed, and native vegetation provide stability, even during large storm events. These designs are currently being used for wooded ravine outfalls in Anne Arundel County, MD. Variety of management practices for spill response, materials storage, landscape maintenance, dumpster management, disposal of wash water and wastewater, vehicle maintenance, and employee training to keep pollutants out of stormwater runoff and waterways. 2 See Appendix F for a more extensive description of Regenerative Stormwater Conveyance systems. Stormwater Retrofit Opportunities on Public Lands in Fluvanna County 5

11 Section 3. Summary of Concepts Identified Field crews identified a total of twenty stormwater retrofit concepts throughout the Fluvanna County sites inventoried for this study. Multiple retrofit concepts were developed for each of the properties. Each concept was assigned a unique site code (e.g., CE 1 and CE 2 at Central Elementary). The concepts identified during this study, listed in Table 1, can be categorized as follows: Stormwater Retrofits Creating or re designing engineered structures designed to capture and treat runoff. Some are simple (e.g., cutting a street curb to allow runoff to flow through vegetation) and others more complex (constructing bioretention areas consisting of plants, mulch, soil, and underdrains). Re vegetation/tree planting Replacing mowed grass with trees or meadow to reduce runoff and increase rain infiltration. Soil amendments may also be used for re vegetation projects to enhance water retention and promote better plant growth. Outfall Protection Placing rock or other structures at pipe outfalls to prevent or repair erosion and reduce runoff velocities to the receiving stream. Pollution Prevention Modifying common management practices to prevent pollutants from being released to the environment in the first place (also know as source control ). The majority of the concepts developed during the Fluvanna County study are in the category of Stormwater Retrofits, such as rain gardens, bioretention areas, dry swales, and rainwater harvesting. These structures help reduce existing pollutant loads and/or runoff volume from impervious areas such as parking lots, streets, and roofs. The field crews also identified three areas that could benefit from re vegetation, specifically tree planting. Schools and other institutional properties often have large amounts of turf grass that is mowed (and sometimes fertilized), but not necessarily used for any purpose other than for open space. Areas where grass is kept short and mowed frequently become compacted and thus more impervious to infiltration of water. Therefore, these turf areas generate significant amounts of runoff that flows to nearby streams. In contrast, replacing these areas with trees and/or tall grasses allows for more interception of rainfall by branches and leaves and provides more porous soil due to their deep root structure. Both of these factors allow more precipitation to infiltrate into the ground. Trees also provide other physical benefits such as shade, cooling, and wind protection. In some cases, re vegetation projects may also involve amending compacted and clayey soils with organic matter in order to enhance water retention and promote a better planting environment. Three outfall pipes or spillways were discovered to have insufficient protection from erosion and thus were noted as potential retrofits. An outfall protection retrofit typically calls for the addition of velocity controls and/or structural reinforcements, such as a plunge pool, stone revetment, or check dams. Finally, the field inventory identified one specific site in need of Pollution Prevention action, where it appeared that wash water is regularly dumped into a storm drain. Although the field teams only proposed one pollution prevention retrofit, other sources of stormwater pollution may exist on these properties that could be mitigated with better management practices. At schools and other public Stormwater Retrofit Opportunities on Public Lands in Fluvanna County 6

12 properties, possible sources of stormwater pollution, or hotspots, include: vehicle maintenance areas, leaking dumpsters, improperly covered hazardous waste materials, and outdoor rinsing of fertilizer/ pesticide applicators, among other sources. Table 1: Types of Retrofits Identified in Fluvanna County Type # Identified* Sites 5 Central Elementary School Bioretention/Rain Garden 4 Fluvanna High School 2 Village of Palmyra Rainwater Harvesting 2 Central Elementary School Dry Swale 1 Village of Palmyra Grass Channel 1 Village of Palmyra Extended Detention 1 Central Elementary School 1 Central Elementary School Re vegetation/tree planting 1 Fluvanna High School 1 Village of Palmyra 2 Fluvanna High School Outfall Protection 1 Village of Palmyra Pollution Prevention 1 Central Elementary School *Some sites comprise multiple types of retrofits (e.g., Rainwater Harvesting tank overflowing into Bioretention) Section 4. Evaluation and Ranking of Retrofit Concepts Upon completion of field work, Center for Watershed Protection staff identified the following characteristics for each proposed stormwater retrofit site: Drainage area (DA) size delineated using GIS & site plans if field estimates uncertain Land cover in drainage area % impervious cover (IC), % turf cover, and % forest cover Treatment volume design target volume needed to treat runoff from 1 of precipitation Treatment volume provided volume available based on footprint of retrofit and storage volume Special notes and construction considerations With this basic information in hand, CWP was able to develop planning level estimates of nutrient removal, runoff reduction, and construction cost values using a variety of data sources. A summary table of these values for each retrofit concept is located in Appendix C. Once basic data were compiled about each retrofit site, the scoring and ranking process began. This process involved giving each retrofit concept a score based on several ranking factors, or performance categories. The purpose of the ranking process was to provide a prioritized list of projects that can serve as a guide for implementation. This will assist Fluvanna County staff to evaluate the projects that best meet specific goals, such as pollution reduction and/or education and outreach. However, it must be understood that the prioritized list is only a guide, and that professional judgment, funding opportunities, and broader County needs also play a role in determining which projects should be implemented at any given time. Stormwater Retrofit Opportunities on Public Lands in Fluvanna County 7

13 For this study, CWP chose four ranking factors that reflect the goals of the RRBC and Fluvanna County. They are: (1) Total Phosphorus 3 removed, (2) cost effectiveness, (3) visibility and outreach potential, and (4) apparent opportunity and interest. See Table 2 for a description of each ranking factor and scoring scale. The individual scores in each of the categories were summed to produce an overall score for each of the retrofits (100 points maximum), and the retrofits were ranked from highest to lowest score. It should be noted that this scoring process only applied to the stormwater retrofit and tree planting projects, because these can be compared to each other based on pollutant load reductions, cost effectiveness, and the other two ranking factors. Other projects, such as pollution prevention and outfall repairs, also reduce pollutant loads, but are more difficult to quantify in terms of pollutant load reduction capabilities. Table 2. Scoring Criteria Used for Ranking Ranking Factor Description Scoring Pounds of Total Phosphorus (TP) Removed TP used as indicator for other pollutants Cost Effectiveness (per pound of TP treated) Visibility & Outreach Opportunity & Interest Combines influence of impervious and turf Fourth Quartile = 30 cover in the drainage area and the Third Quartile = 20 phosphorus removal efficiency of the Second Quartile = 10 proposed retrofit (see Appendix D). First Quartile = 0 Construction cost divided by pounds of TP removed. Extent to which a practice is visible and is useful for educating students and community members about stormwater. Extent to which a practice is likely be implemented due to factors such as County staff interest, timing with other planned improvements, and opportunity to address several problems at once. Fourth Quartile (highest cost) = 0 Third Quartile = 10 Second Quartile = 20 First Quartile (lowest cost) = 30 High = 20 Medium = 10 Low = 0 High = 20 Medium = 10 Low = 0 To help explain how these four ranking factors were used to produce an overall score for each retrofit concept, Table 3 provides a scoring example for a proposed retrofit at Central Elementary School. A more detailed description of the ranking factors and scoring criteria for the Fluvanna retrofit concepts, as well as a table of detailed scores for each, can be found in Appendix D. Table 3. Scoring Example (Retrofit Concept: CE 6, Rain garden at southeast corner of building) Ranking Factor Value Quartile Score Total Phosphorus Removed 0.21 lbs/yr 1 st 0 points Cost per lb TP Removed $28, per lb of TP 1 st 30 points Visibility & Outreach High 20 points Opportunity & Interest Medium 10 points TOTAL = 60 points 3 Total Phosphorus is the total concentration of all forms of phosphorus (e.g., orthophosphate, metaphosphate). Total Phosphorus concentration in stormwater runoff is often used as an indicator of levels of other nutrients and pollutants that may be present in the runoff. Stormwater Retrofit Opportunities on Public Lands in Fluvanna County 8

14 Subsequent to the first draft of this report, a meeting was held on September 30, 2010 with Fluvanna County staff and representatives to review CWP s initial scoring of retrofits. The group made suggestions for increasing or decreasing the Visibility & Outreach and Opportunity & Interest scores for some of the retrofits, based on their knowledge and insights. The scores shown in Table 4 below reflect the revisions made based on this meeting. (This table also lists the retrofit concepts that were not scored outfall protection and pollution prevention sites.) Participants at the September meeting also selected high priority retrofits for more detailed design work to be conducted by CWP. The selected projects are three interconnected bioretention areas at the Fluvanna High School (FHS 1, FHS 2, and FHS 3). Table 4. Individual Stormwater Retrofit Scoring Site Central Elementary School Fluvanna High School Fluvanna High School Village of Palmyra Central Elementary School Fluvanna High School Fluvanna High School Fluvanna High School Central Elementary School Fluvanna High School Village of Palmyra Central Elementary School Central Elementary School Fluvanna High School Description Concept ID TOTAL (Out of 100 pts) Pollution Prevention Eliminate practice of pouring wash water down storm drain outside cafeteria. Also need dumpster management for trash. CE 4 n/a Outfall protection at outfall located in woods between baseball & softball fields. FHS 5 n/a Outfall protection at blown out outlet channel of old erosion control basin (now wetland) weir or berm and channel stabilization. FHS 7 n/a Outfall Protection such as a plunge pool; weir and wetland plants; Tree Planting on hillside. VP 2b n/a Bioretention and Tree Planting to treat asphalt play area and provide shade. Combine with playground refurbishment. CE 1 90 Bioretention in medians of front parking area. Also Pollution Prevention: eliminate use of herbicide in swale. FHS 1 90 Bioretention refurbishment (1650 sq. ft) and potentially Stormwater Planter at eastern entrance into school. FHS 4 90 Bioretention at bottom of parking area, within landscape island. FHS 3 80 Rainwater Harvesting in courtyard with A.C. unit and trailers (rooftop disconnection). CE 5 70 Tree planting and soil amendments in front of school and between lower parking lot and track complex; 1.7 acres available. FHS 6 70 Bioretention to treat admin. buildings and parking lot; requires significant addition of manholes and piping to divert runoff. VP 3b 70 Rain Garden on SE corner of building, behind school near wood line. Alternatively, plant trees in this area. CE 6 60 Bioretention along length of building to treat runoff from roof of addition. CE 8 60 Bioretention retrofit in existing detention basin to provide more pollutant removal. FHS 2 60 Stormwater Retrofit Opportunities on Public Lands in Fluvanna County 9

15 Table 4. Individual Stormwater Retrofit Scoring Site Description Concept TOTAL ID (Out of 100 pts) Central Elementary School Bioretention with Rainwater Harvesting along south side of addition to treat roof runoff. CE 2 50 Central Elementary School Extended Detention/Outfall Protection to prevent erosion, with shade tolerant wetland plantings. CE 3 40 Village of Palmyra Bioretention for runoff to be diverted from drain inlet near Court building driveway. VP 3a 30 Village of Palmyra Dry Swale in place of current concrete channel, with overflow going to diversion pipe under road. VP 1 10 Central Elementary School Bioretention in 3 parking lot islands, east of school. Alternatively, plant trees in islands. CE 7 0 Village of Palmyra Grass Channel diversion to disconnect part of drainage area. Conveyance, not treatment. VP 2a 0 Examples of some of the highly ranked concepts are shown in Figure 3 below. However, a full catalog of photos, field forms, and location maps for each retrofit site is contained in Appendix E. This appendix also contains computer generated landscape visualizations for some of the top ranked retrofit concepts, such as the one shown in Figure 4. These images are helpful for visualizing what a stormwater practice might actually look like once installed (for instance, a bioretention area within a parking lot median). Stormwater Retrofit Opportunities on Public Lands in Fluvanna County 10

16 Figure 3. Examples of Highly Ranked Sites A B C D E F Examples of highly ranked sites: (A) (FHS 1) High School, in medians of front parking area convert to bioretention and eliminate use of herbicides. (B) (FHS 4) Along front of High School refurbish mulched area into bioretention. (C) (CE 1) Central Elementary playground bioretention and tree planting to reduce erosion and provide shade. (D) (CE 6) Central Elementary, S.E. corner near wood line build rain garden with students. (E) (FHS 5) High School, between baseball and softball fields repair outfall & erosion. (F) (CE 4) Central Elementary, outside cafeteria service entrance door eliminate dumping of wash water into storm drain. Stormwater Retrofit Opportunities on Public Lands in Fluvanna County 11

17 Figure 4. Example of Computer generated Retrofit Visualization Present Retrofit Example of a computer generated landscape visualization of a retrofit concept, on right (FHS 1 Bioretention in median of High School s lower parking lot). Stormwater Retrofit Opportunities on Public Lands in Fluvanna County 12

18 Section 5. Maintenance Considerations Ongoing maintenance is another consideration for deciding which retrofits to implement. Maintenance is needed to keep the practices functioning properly. Operation and maintenance does require resources, which should be anticipated prior to implementing any of the practices recommended in this study. Figure 6 outlines, in general terms, recommended maintenance activities associated with each type of practice. While no practice can be considered completely maintenance free, there are choices in the initial design of the practice that will influence the type and extent of ongoing maintenance. In other words, long term maintenance responsibilities can be reduced if the practices are properly designed within the context of the site and the operation and maintenance capabilities and preferences of the responsible agency (e.g., school division grounds crew). Several examples may help to illustrate this point (as reiterated in Figure 5): Bioretention, bioswales, rain gardens, and dry swales can either be designed with conventional mulch and perennial (often ornamental) plantings or an alternative turf cover landscape design. The former may provide better filtration of runoff, but requires routine weeding and mulch replacement. The turf cover design, however, includes grass that may be routinely mowed along with the adjacent turf areas (if slopes are not too steep), as well as interspersed trees or shrubs. Many entities responsible for landscape maintenance prefer to mow rather than keeping fairly large areas weeded and mulched. Re vegetation and tree planting projects can be designed for their landscape context. For instance, projects that are not within highly visible or high use areas may be inclined towards a more naturalistic look. These projects will likely use smaller, closely spaced tree saplings, with perhaps a wildflower ground cover. Alternately, high visibility areas (e.g., at the entrance of Fluvanna High School) may strive for a more park like setting, with larger, more widely spaced trees and mowed grass in between. The benefit of the former approach is that tree canopy closure will occur more rapidly, resulting in forest understory conditions which will eliminate the need for mowing and can save on maintenance budgets. However, the latter scenario may be more appropriate in some settings and will appeal to landscape crews that are accustomed to mowing. Decisions like these should be made up front so that budgets, planting materials, and maintenance schedules can be articulated to achieve the desired outcome. As applicable, Figure 6 provides these types of maintenance reduction design ideas for listed practices. More detailed maintenance information and checklists for the full range of stormwater practices can be found in the detailed Virginia DCR BMP Specifications housed on the following website (VADCR, 2010a): An excellent guide for planning and maintaining re vegetation and reforestation sites entitled, Riparian Forest Buffer Design and Maintenance, can be found at: Stormwater Retrofit Opportunities on Public Lands in Fluvanna County 13

19 Figure 5. Examples of Design Options Relative to Maintenance Top Row: Shows a higher maintenance approach to bioretention design, with mulch and perennials (left) compared to a lower maintenance tree and turf design (right). Bottom Row: Shows a naturalistic re vegetation site where grass must be occasionally bush hogged around the newlyplanted trees (left), compared to a park like setting where mowing continues routinely around the trees (photo courtesy of Frederick County, MD). Stormwater Retrofit Opportunities on Public Lands in Fluvanna County 14

20 Figure 6. Operation and Maintenance Considerations for Stormwater Practices Bioretention or Maintenance consists largely of weeding, mulching, and other tasks Bioswale related to maintaining plants, as well as keeping inlets (e.g., curb cuts) free of debris and sediment. Infrequent replacement of soil media may be necessary (every 20 to 30 years). Maintenance can be reduced by using a ground cover that can be mowed along with other turf areas on the site. Rain Garden Maintenance tasks are largely dictated by the type of vegetation used. Managing plants and replacing mulch are the most frequent maintenance tasks. As with bioretention, maintenance can be reduced by using simple plant templates. Dry Swale See above for bioretention and rain gardens. If check dams are used, maintenance includes periodic cleaning of debris and ensuring that water is not flowing around the ends of check dams and causing erosion. Infiltration Impervious Disconnection Sediment control is the most important maintenance task for infiltration. This includes minimizing exposed soil and other sediment sources in the drainage area and cleaning fine sediment off of the surface of the infiltration practice. In most cases, the top 2 to 3 inches of stone needs to be replaced with clean material every 2 to 3 years. On an infrequent basis, the entire stone layer may need to be replaced. Maintenance can be reduced by limiting the drainage area to only impervious cover, so clogging from leaf and grass debris is minimal. This is a relatively low maintenance practice. The chief maintenance concern is making sure that erosion is not occurring at the downspout or creating a drainage problem. Maintenance can be reduced by limiting the drainage area directed to each downspout to less than 1,000 square feet. Stormwater Planter As with bioretention and rain gardens, maintenance is largely focused on managing vegetation. Also, it is important to check periodically that flow is not by passing or creating erosion through the soil media. Stormwater Retrofit Opportunities on Public Lands in Fluvanna County 15

21 Figure 6. Operation and Maintenance Considerations for Stormwater Practices Rainwater Maintenance is dictated largely by use of the water (outdoor and/or Harvesting indoor uses). At a minimum, leaves and debris must be removed from gutters and downspouts as well as leaf screens and first flush diverters. Above ground systems may need to be drained in the winter to avoid freezing. Mosquito prevention screens should be checked seasonally and holes patched. Permeable Pavement Extended Detention Basin Re Vegetation Photo by: Frederick County, MD. Maintenance can be reduced by employing effective pre treatment devices, such as leaf screens on gutters, first flush diverters, and, for larger systems, vortex filters. Most installations function well with little maintenance. Large scale applications likely require annual vacuum sweeping to remove accumulated sediment. Periodic weeding may also be needed if plants start to grow in the voids. Maintenance can be reduced by limiting the drainage area that flows onto the permeable parking surface. Ideally, drainage areas should be as small as possible, but should not exceed 2 times the area of the permeable parking surface. Historically, these types of basins garnered a poor reputation because of the lack of maintenance. Basins should be maintained by periodically removing sediment, checking for blockages at inlets and outlets, checking the structural stability of the dam, repairing erosion in the basin or on side slopes, removing woody vegetation from the dam, and maintaining access routes. Maintenance can be reduced by using sediment forebays and providing vehicular maintenance access to dams, risers, and forebays. The most critical maintenance tasks occur within the first several years of planting. Trees may need to be watered and mowing or bushhogging may need to occur around the trees (without damaging the trees). The most critical task is to ensure that moisture competition in a 3 foot diameter area around the tree is minimal. Noxious weeds need to be controlled, especially until a canopy begins to form. If desired, dead or dying trees should be replaced. Maintenance can be reduced (or at least better anticipated) by premeditating the ultimate landscape setting that is desired. For instance, some applications may be better suited to a park like setting whereby mowed grass is maintained between trees. Selecting larger nursery stock that is spaced to allow easy mowing will help achieve this type of outcome. Maintenance can also be reduced through good site preparation: converting tall fescue to a more tree friendly alternative ground cover of desirable species (e.g., creeping red fescue, clover, wildflowers); eliminating noxious weeds prior to planting (this includes nearby seed sources); providing soil amendments where necessary; and site layout to allow for a variety maintenance activities (e.g., access, spacing, turning areas for mowers). Stormwater Retrofit Opportunities on Public Lands in Fluvanna County 16

22 Figure 6. Operation and Maintenance Considerations for Stormwater Practices Outfall Maintenance of outfall protection involves ensuring that clogging, Protection erosion, and sediment deposition are kept to a minimum at the outfall. Repairs can include replacing rip rap or stone, re grading to fix erosion, and removing sediment with a small excavator. Regenerative Stormwater Conveyance (for Outfall Protection) 4 Maintenance can be accommodated by ensuring that long term maintenance access is provided to the outfall, and that the original channel lining is adequate to withstand the anticipated velocity of water coming out of the outfall pipe. These systems are designed to evolve into a natural system that does not require routine maintenance. As with tree planting, the initial installation period of 2 to 3 years requires control of invasive plants. Maintenance during this period also includes checking for erosion through the cells or around the edges of grade control structures. (Photo by: Keith Underwood) Pollution Prevention Pollution prevention represents management practices to keep pollutants from being exposed to stormwater in the first place. Maintenance, in this context, can be thought of as ongoing programs for employee training and developing and maintaining pollution prevention plans for applicable facilities. These plans lay out protocols for materials storage and proper disposal, spill response, use of pesticides, solid waste management, and other related topics. 4 See Appendix F for a more extensive description of Regenerative Stormwater Conveyance systems. Stormwater Retrofit Opportunities on Public Lands in Fluvanna County 17

23 Section 6. Recommendations for Retrofit Implementation and Delivery This report presents a systematic way to identify, score, and rank potential stormwater retrofits in Fluvanna County. However, the only environmental benefit accrues from retrofits that are actually constructed. The following list represents a hierarchy of proposed implementation strategies: 1. Correct identified pollution prevention situations (for instance, at Central Elementary) and enhance pollution prevention through employee training, materials storage, and spill response. Pollution prevention will always be the most cost effective strategy to keep pollutants out of stormwater. Within the Rivanna Basin, Albemarle County and its Schools Division are entities that have incorporated pollution prevention practices into their Environmental Management System protocols. Information about the Schools program can be found at: Many tips and resources for pollution prevention can also be found on the Environmental Protection Agency s website at 2. Fix outfalls that are eroding and/or exhibit structural damage, especially FHS 5. Provide more secure and durable velocity and erosion control materials, such as rip rap or baffles to prevent further problems. Where erosion is extensive, consider restoring the outfall channel with the use of Regenerative Stormwater Conveyance design techniques. These outfall designs use a series of shallow pools, an underlying sand bed, and native vegetation to convey and treat stormwater runoff in a stable manner. See Appendix F for a description of this approach. 3. At schools, evaluate areas that can simply be restored by not mowing the area (or only bush hogging several times per year). Such areas that are allowed to grow up into tall grasses and shrubs (and eventually trees) provide a niche habitat that is rapidly disappearing and may result in attracting unique wildlife such as the American woodcock and the golden wing warbler. These areas should be carefully selected to avoid complaints from school administrators, maintenance crews, parents, and other stakeholders. Appropriate signage may help to alleviate some of these concerns and highlight the importance of this type of ecosystem. Consider starting with a pilot project to see how the area looks and how maintenance crews respond. Such a project could be used as an educational opportunity for facilities managers, maintenance crews, and the public. In general, this approach can save time and money on grounds maintenance while reducing stormwater runoff and pollution. 4. Some areas may be suitable for tree planting by volunteers and/or professional crews. These would be good projects if they serve an educational purpose and were part of community outreach campaigns. Soil testing should be done prior to tree planting to ascertain whether soil amendments and/or tilling are needed to promote proper tree growth. 5. Seek opportunities through grants and other funding sources to implement stormwater retrofit projects. Potential sources of funding include grants from the Virginia Department of Forestry for tree planting projects, outdoor classroom or other education grants to help support education friendly retrofits at schools, and federal grants. Stormwater Retrofit Opportunities on Public Lands in Fluvanna County 18

24 The County can also seek ways to reduce costs to implement retrofits, including: Seek donated materials and services from local vendors and contractors. Use volunteers for simple rain garden construction, installing plantings at other practices, and planting trees for re vegetation projects. Use in house crews to conduct the work wherever possible. Partner with the Rivanna River Basin Commission and other regional entities on joint grant proposals. Partner with watershed organizations, such as the Rivanna Conservation Society, to plan and implement some of the projects. 6. Review building and development codes and ordinances to promote more progressive stormwater management practices and begin discussions about how Fluvanna County may or should respond to upcoming stormwater regulations and requirements of the Chesapeake Bay TMDL. Fluvanna County staff and officials are encouraged to consider these recommendations and the findings of this retrofit inventory as plans are made for capital improvement projects and environmental stewardship efforts on these public lands. We hope that this report will guide the County towards stormwater retrofit projects that have the best potential for success in reducing the impact that these developed areas have on water quality. In taking steps to reduce runoff and improve infiltration on these and other public properties, Fluvanna County will help address a major source of pollution to the Rivanna River and its tributaries. References Center for Watershed Protection (CWP) Urban Stormwater Retrofit Practices. Version 1.0. CWP, Ellicott City, MD. Center for Watershed Protection (CWP) and Chesapeake Stormwater Network (CSN) Technical Memorandum: The Runoff Reduction Method. CWP, Ellicott City, MD. Hathaway, J. and W. Hunt Stormwater BMP Costs. North Carolina State University. Department of Biological and Agricultural Engineering. Raleigh, NC. Maryland Department of Natural Resources (MDDNR) Riparian Forest Buffer Design and Maintenance. Online at Accessed on 9/20/10. Virginia Department of Conservation and Recreation (VADCR). 2010a. Virginia BMP Clearinghouse website. Online at Accessed on 9/20/10. Virginia Department of Conservation and Recreation (VADCR). 2010b. Runoff Reduction website. Online at Accessed on 9/20/2010. Stormwater Retrofit Opportunities on Public Lands in Fluvanna County 19