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Drones: A Practical Investment for MS4 Programs

Figure 2. A drone is used to identify the source of an illicit discharge.

Sioux Falls, South Dakota, USA, is a designated Phase I Municipal Separate Storm Sewer Systems (MS4) with a population of approximately 200,000 residents. The city has experienced unprecedented growth in recent years. Since 2020, the city’s MS4 service area has increased by over five miles2 (13 km2) with annexations and infill development. Completing day-to-day responsibilities of the MS4 program, while overseeing 300-plus construction projects for erosion and sediment control compliance, became an overwhelming task. For this reason, the city’s MS4 team began looking for ways to manage the program more efficiently.


Around this same time, a large 50-acre (20-ha) city construction project broke ground. While this project was under construction, the city’s communication department would regularly use a drone to capture aerial photos of the site to document progress. After viewing a series of these photos, the MS4 team realized that a drone would be a practical tool to streamline erosion and sediment control inspections of larger construction sites. While using drones for site surveys and inspections is not a new concept, the advancement of drone technology and reduced cost has made their use more feasible for many different industries including the public sector.

Figure 1. A drone is used to survey perimeter sediment controls where accessibility is difficult.


Benefits
Aerial imaging via drone allows for easier inspections of remote areas of a site where perimeter and other erosion and sediment controls are not easily accessible by vehicle or on foot (Figure 1). Drones allow for timely and effective inspections of sites following spring thaw or rain. Initial surveys of larger sites via drone significantly reduce total inspection time, and drones can be used for other MS4 management tasks including illicit discharge investigations (Figure 2), infrastructure assessments (Figure 3) and general photography (Figure 4).

Today’s drones have out-of-the-box features and functionality that make them exceptionally safe and easy to operate. High-resolution cameras are standard on most drones to provide exceptional image quality. All commercial-grade drones have GPS technology built in which, in addition to general flight safety, allows for geotagging photos and waypoint missions. The MS4 team recently began adding waypoints to some construction sites. Once a site has waypoints and areas of interest identified, the drone will fly the same path each time and capture pictures of selected areas. The pictures can then be uploaded to a geographic information system map to monitor site best management practices throughout the construction project.


Challenges
While drones may provide numerous benefits, there remain several challenges to consider when deciding if a drone is feasible for their MS4 program. The first is cost. Drone acquisition, licensing, insurance and maintenance are all costs that must be budgeted.
A second important consideration is what type of airspace the program will operate in. Most urban areas have airspace with some level of Federal Aviation Administration (FAA) control where drone activity may be limited, if not restricted completely. Modern drones incorporate advanced geofencing functionality which prevents them from entering controlled airspace unless properly authorized. While requesting authorization to work in certain areas of controlled airspace is possible through Low Altitude Authorization and Notification Capability (LAANC), the process adds time to each mission. LAANC approvals can be requested up to 90 days in advance and in many cases are eligible for auto approval in near-real time.1 Depending on how often authorization is required for the local airspace, this may present a challenge to certain drone programs.

Weather and environmental conditions regularly present challenges to drone missions. Winds greater than 20 mph (17.4 knots), low clouds and fog greatly impact the ability to safely perform flights. Temperature and humidity extremes will reduce drone performance and efficiency and reduce battery life. Environmental conditions such as topography or the presence of dust or smoke can also impact drone performance and safe operation.

Organizational policies are the final challenge to consider. With drone use increasing rapidly, organizations may have specific policies. For example, invasion of privacy is and will continue to be an important consideration for any drone program. Drone usage in urbanized areas should follow organizational policies regarding public privacy. Another organizational policy worth reviewing is whether the approval authority of the MS4 program considers remote imaging via drone a valid inspection procedure. While rare, this is a valid concern that an MS4 program must discuss and clarify with their approval authority before initiating a drone inspection program.


Acquisition and Maintenance
The Sioux Falls MS4 team was granted a budget of $3,000 to cover the cost of the unit and accessories. The drone itself was approximately $1,800. An additional $800 was spent on accessories including batteries, a charging dock, replacement propellers and a hard-sided storage case. Part 107 certification costs $175 per licensee plus staff time for training. Insurance for drone work is highly variable depending on the number of units and operators ranging from individual hourly rates to annual group policies.2 The City of Sioux Falls already had a group policy in place to cover the MS4 team’s drone use.

For maintenance, the team uses a free online logging application to track drone usage. The application allows the team to track total flight hours for the drone itself, a certain pilot, a specific site or even an individual battery. Flight information can be manually entered or uploaded directly from the drone. Using this data, the application records total flight time and can generate reminders for routine maintenance needs as advised by the drone manufacturer.


FAA Part 107 Certification and Compliance
Part 107 Certification took the MS4 staff approximately 40 to 60 hours to complete. Most of that time was spent learning the FAA regulations for Small Unmanned Aircraft Systems (sUAS). Hands-on training with certified staff provided valuable experience on the remote controller interface, drone operations and safety procedures should an emergency occur during flight. After the acquisition, our drone was registered with the FAA, and the geofencing was removed through our drone manufacturer’s Qualified Entities Program. Our pilots submitted Declarations of Compliance (DOC) to Operate Over People (OOP) and to verify that our drone has remote identification. These DOCs are required for any pilot conducting drone inspections in an active construction site where individuals not involved with the flight operation are present. Specifics on final rulings regarding these DOCs and other FAA Part 107 regulations can be found on the FAA website and should be consulted often as regulations for sUAS are subject to change.

Figure 3. A drone is used to inspect city drainage properties and associated stormwater infrastructure to identify maintenance needs.


Looking to the Future
The city recently acquired a larger drone capable of carrying more specialized survey equipment such as Light Detection and Ranging (LiDAR) and multispectral cameras. While there are no immediate plans to use this technology in the MS4 program, additional research is warranted. For example, LiDAR may be beneficial to measure sediment accumulation in entrapment devices overgrown with vegetation, or multispectral cameras, like near-infrared, may help monitor vegetation cover of a site and determine where deficiencies exist. Drone technology will continue to advance, bringing with it more capabilities and practical applications. 

References

  1. Federal Aviation Administration, UAS Data Exchange (LAANC), 1 February 2024. https://www.faa.gov/uas/getting_started/laanc (accessed 08 April 2024).
  2. Luthi B. What is Drone Insurance? USA Today, 13 November 2023. https://www.usatoday.com/money/blueprint/insurance/what-is-drone-insurance/ (accessed 08 April 2024).

Resources

  • Learn more about Small Unmanned Aircraft Systems regulations by visiting the FAA’s website: https://www.faa.gov/uas.
  • Sioux Falls drone construction site monitoring: https://storymaps.arcgis.com/stories/15049771c04449d8b81d6e6b67fbbb11.
  • Sioux Falls storm inlet art project: https://storymaps.arcgis.com/stories/3895c14e2816420ebfbae64ff0f7cb61.

About the Experts

  • Troy Lambert is an environmental analyst with the City of Sioux Falls, South Dakota. He graduated with a bachelor’s in environmental science from South Dakota State University. He has worked for the City of Sioux Falls since graduating in 2015 and currently oversees the city’s MS4 program.
  • Jose Alvarez, CISEC-IT, ENV SP, is an environmental analyst with the City of Sioux Falls, South Dakota. He graduated with a Bachelor of Arts in Science from Augustana University. He has worked for the City of Sioux Falls since graduating in 2017 and currently oversees the city’s MS4 program.
Figure 4. A drone was used to capture an overhead photo of a storm drain painting to promote the education program.

Reducing Nutrient Loading to the Chesapeake Bay

Figure 1. Map of the Chesapeake Bay Watershed.

Maryland’s Conowingo Dam was constructed in 1928 and is the most downstream of the four hydroelectric dams located on the lower Susquehanna River. The Susquehanna River basin has a 27,500 square mile (71,225 sq. km.) drainage area (Figure 1) that consists of three states in the United States: Pennsylvania (77% of the area), New York (22%) and Maryland (1%)1 and represents 43% of the land area draining into the Chesapeake Bay, which is the largest of over 100 estuaries in the United States. The Chesapeake Bay receives approximately half of its water volume as freshwater from the 64,000 mile2 (165,759 km2) watershed and the other half as saltwater from the Atlantic Ocean.2 Although all of the dams historically trapped and stored sediment and nutrients in their reservoirs, recent information shows that the Conowingo Dam has reached dynamic equilibrium, meaning sediment behind the dam has built up to the extent that it can no longer trap additional sediment or other pollutants.

The Center for Watershed Protection developed the Conowingo Watershed Implementation Plan (CWIP) to address the additional nutrient and sediment reduction needed to restore the Chesapeake Bay, given this loss of storage capacity. The CWIP is based on the premise that, to successfully reduce the Conowingo nutrient loads, jurisdictions in the Susquehanna River basin must work collectively by pooling resources and reducing implementation costs through targeting pollution reduction practices to the most effective locations.

The United States Environmental Protection Agency (EPA) initiated this effort and continues to administer the cooperative agreements driving the CWIP, which is supported by the Chesapeake Bay Program Principals’ Staff Committee (PSC). The CWIP cooperative agreements are comprised of three activities implemented by third-party grantees, which include:

  1. Facilitating the development and implementation of the CWIP and associated two-year milestones.
  2. Developing and proposing a comprehensive CWIP financing strategy and associated implementation plan.
  3. Tracking, verifying, and reporting the implementation of the CWIP and two-year milestones.

The CWIP was adopted on July 31, 2021, and EPA funded these activities through 2025.

The CWIP provides a strategy to prevent over six million pounds of nitrogen from entering the Chesapeake Bay annually with an estimated cost of $53.3 million per year (Figure 2).

In July 2022, the PSC reached consensus that the Susquehanna jurisdictions can implement the CWIP using a phased approach that extends beyond 2025 to allow time to build the organizational infrastructure needed for implementation. The CWIP Steering Committee — which includes representatives from each Chesapeake Bay jurisdiction (Delaware, the District of Columbia, Maryland, New York, Pennsylvania, Virginia, and West Virginia) and the Chesapeake Bay Commission — meets quarterly to oversee progress and support CWIP implementation.
The implementation milestones developed by the CWIP Steering Committee set specific, measurable goals for the CWIP that include:

  • Building capacity.
  • Financing and securing funding.
  • Fostering innovation.
  • Identifying and building partnerships.
  • Developing and implementing pilot projects.
  • Conducting outreach and engagement.
  • Monitoring nutrient reduction targets.


To achieve these goals, the CWIP Steering Committee outlined a uniquely tailored approach for the Conowingo WIP of a two-tiered implementation framework that includes smaller-scale, watershed-specific and broader-scale, state-wide strategies. The best management practices (BMPs) implemented as part of these programs will assist with meeting the numeric load reduction goals for the first phase of implementation that extends through 2025.

The CWIP’s BMP implementation strategy is designed to target landscape-scale restoration strategies using BMPs that integrate into existing agricultural land management practices (such as nutrient application management) and avoid BMPs that remove farmland from production.
Approximately 90% of the nitrogen load reduction in the CWIP is from agricultural BMPs, which include natural filters like wetland restoration and riparian forest buffers, sustainable farm practices like prescribed grazing and conservation tillage, and nutrient reduction practices like nutrient management and manure incorporation.

The CWIP also aims to minimize the cost per pound for nitrogen reduction. To achieve this goal, BMP implementation is targeted to the portions of the Susquehanna River basin that are most effective at delivering nitrogen to the Chesapeake Bay and, therefore, offer the best opportunity to reduce nitrogen loads and improve conditions in the Bay. These areas are referred to as “Most Effective Basins.” Additionally, the CWIP recommends performing evaluations of innovative practices that are not already approved Chesapeake Bay Program BMPs, such as dredging the dam reservoirs, to determine if the pollution reduction benefits from these practices could contribute to CWIP goals.

This BMP implementation strategy is being executed within the context of the Steering Committee’s two-tiered implementation framework that supports smaller watershed and broader state-wide efforts. Smaller-scale outreach has been targeted to specific multi-state watersheds in Most Effective Basins identified in the CWIP, such as the Octoraro watershed that spans portions of Pennsylvania’s Chester and Lancaster Counties into Maryland’s Cecil County. The CWIP implementation team meets with the Octoraro Watershed Association, Octoraro Source Water Collaborative, soil conservation districts from each state and other interested parties in the watershed to form partnerships and discuss projects and funding opportunities. The Susquehanna River Basin Commission (SRBC) developed a “State of the Octoraro Creek Watershed” StoryMap (see Resource) with comprehensive information on water quality and restoration efforts in the watershed. Smaller-scale projects are funded through traditional financing approaches, such as state or federal grants, loans, cost-sharing or other cooperative funding.

Broader, state-wide implementation efforts use a pay-for-performance financing approach in Maryland and Pennsylvania. For both state programs, criteria for awarding pay-for-performance contracts emphasize innovative financing and greatest return on investment in terms of nitrogen reductions. Projects with co-benefits are incentivized to foster new public-private partnerships. Some examples of state-wide funding allocations to achieve CWIP goals are listed below:

  • Maryland allocated $25 million for a Verified Nutrient Reductions program that is administered by the SRBC. The first solicitation for projects was issued in 2023 and projects will be awarded in the second quarter of 2024. Maryland’s funds can be used anywhere in the Susquehanna River basin with priority given to projects in Maryland.
  • Pennsylvania allocated $22 million to the Clean Water Procurement Program administered by the Pennsylvania Infrastructure Investment Authority for pay for performance projects. The first project solicitation was issued in 2023 with projects awarded in the first quarter of 2024. A second project solicitation was issued in March 2024. Additionally, Pennsylvania awarded the Local Government Impact grant to the Chester County Soil Conservation District for $1.19 million to fund CWIP implementation in the Octoraro watershed.
  • New York’s approach to broader state-wide implementation is to fund the Upper Susquehanna Coalition (USC) to administer and manage projects implemented in the Most Effective Basins. New York allocated $1 million over two years that is administered by the USC. The USC is also responsible for verification of BMP performance.


While the implementation strategy for the CWIP targets the Most Effective Basins, it is not site-specific. The strategy recommends certain BMP types based on nutrient removal efficiency and cost-effectiveness and relies upon a cooperative multi-jurisdictional effort. Success will be achieved through close collaboration and coordination across the region, which can be replicated elsewhere by adopting the CWIP’s guiding principles. These include striving for fairness and equity, establishing tracking and accountability with transparency, and implementing efficiently without creating duplicative bureaucracies.

The CWIP development was accelerated by the EPA’s funding of cooperative agreements, which enabled multiple jurisdictions to work together with support from the facilitating agencies minus the burden of going through a procurement process. The EPA cooperative agreements allow the time and resources for the Susquehanna jurisdictions to build new organizational capacity to continue cross-jurisdictional implementation efforts beyond 2025. The collaborative multi-state approach establishes a realistic and achievable framework to be successful in reducing nutrients to and improving the health of the Chesapeake Bay.

Figure 2. Nitrogen load reduction for the Conowingo Watershed Implementation Strategy.1

References

  1. Center for Watershed Protection. July 2021 (revised November 2023). Conowingo Watershed Implementation Plan. Prepared as part of U.S. EPA Cooperative Agreement 96366901.
  2. Chesapeake Bay Commission. June 2020. The Chesapeake Bay and Its Watershed. Retrieved from: https://www.chesbay.us/library/public/documents/Fact-Sheets/Bay-Factoids-FINAL.pdf.

Resource
State of the Octoraro Creek Watershed” StoryMap. Susquehanna River Basin Commission.
https://storymaps.arcgis.com/stories/5c006
f55d58945a5a89b37283bb9a581.

About the Expert
Amanda H. Pollack, PE, is a senior water resources engineer at the Center for Watershed Protection and has over 28 years of engineering experience. She holds a bachelor’s degree in civil engineering from Lehigh University and is a licensed professional engineer in Maryland.

Mitigation Banking for Ecological Uplift and Responsible Project Management

Figure 1. Shallow pond formed in decommissioned sand and gravel borrow pit.

Henrico County, part of Virginia’s Capital Region and the Chesapeake Bay watershed, is home to more than 330,000 residents and an active economy. Henrico County managers strive to encourage responsible growth and development in the region while balancing environmental protection considerations. One of those considerations is acquisition of compensatory mitigation credits for authorized impacts to stream and non-tidal wetlands for Henrico County transportation projects, as required by Clean Water Act Sections 404 and 401 and Virginia state regulations.

Mitigation credits are typically generated from wetland and stream restoration and creation projects on private land and made available for sale publicly through mitigation banks. Mitigation credits must be purchased withing the same Hydrologic Unit Code (HUC) 8-digit watershed the impact is occurring in or from an adjacent HUC-8 watershed. With the rapid increase of growth experienced in this region, mitigation credits have been scarce.

To address the need for mitigation credits that have not been available in the marketplace, Wetland Studies and Solutions, Inc. (WSSI) has been working with the Henrico County Department of Public Works to develop a Single-User Umbrella Mitigation Banking Instrument (UMBI) to offset wetland and stream impacts incurred in county projects. With an UMBI structure, Henrico County will be positioned to incorporate additional sites that would benefit from stream and/or wetland restoration to expand the county’s own capacity to address ever-changing mitigation needs. The jointly-developed UMBI currently awaits approval from the Interagency Review Team (IRT), led by the U.S. Army Corps of Engineers and the Virginia Department of Environmental Quality.


A Pilot Site
New Market Park in eastern Henrico County, a ±219-acre (±88.6-ha) parcel, was identified as the pilot mitigation bank site. If approved by the IRT, it would be the first site for this UMBI.

The site is surrounded by land in conservation and is bisected by Four Mile Creek, a tributary of the James River. At its heart, the site has a decommissioned sand and gravel borrow pit, which is now a shallow pond supported by groundwater (Figure 1). Beaver activity within Four Mile Creek has created extensive wetlands and split the main channel into multiple tributaries, or branches, that reconnect to the main channel downstream of the wetland system, all of which could be compromised if the beavers leave or if their structures fail (Figure 2).
The proposed site work includes stabilizing beaver-impounded areas, as well as the streams affected by the impoundment, and altering the hydrology of the shallow pond to create wetlands. More than 29 wetland mitigation credits will be developed through wetland creation, wetland enhancement and upland buffer restoration and preservation. An additional 1,400+ stream mitigation credits will be developed through stream restoration and preservation.

The project development is in full swing and has included a full range of natural and cultural resources investigations as well as preliminary design for the site.


Environmental Investigations
WSSI scientists and surveyors have delineated wetlands and other Waters of the U.S. and Commonwealth of Virginia, and survey-located those features so any impacts and enhancements can be accurately accounted for. Because the site contains potential habitat for the state-endangered swamp pink (Hellonias bullata), WSSI completed a search to ensure survival throughout construction if communities were present on the site; no individuals were present.

A Phase I Environmental Site Assessment was conducted to uncover any potential site contaminants, because it is critical to understand the negative impacts previously experienced in the landscape and waterways. While this site did not require further study or remediation, some sites do.

WSSI also completed an invasive plant species survey because invasive species can wreak havoc on ecosystem balance for plants, animals and the soil. The survey allows for responsible site planning, including removal of plants that can damage the proposed mitigation site’s ecological integrity. The survey identified Japanese stiltgrass (Microstegium vimineum), marsh dewflower (Murdannia keisak), sericea lespedeza (Lespedeza cuneata), golden bamboo (Phyllostachys aurea) and Chinese privet (Ligustrum sinese). These species are common in disturbed areas in the region and often outcompete native species that better support ecological diversity. Fortunately, most of these species can be managed through repeated herbicide treatments and mechanical removal.


Cultural Resources
WSSI’s cultural resource specialists conducted a Phase I archeological and architectural field investigation of the project area, which is entirely within the boundaries of the New Market Heights Battlefield, First Deep Bottom Battlefield; and Bailey’s Creek/Second Deep Bottom Battlefield theatres of the Civil War. The Phase I investigation augmented shovel test pits with systematic metal detection, following Virginia Department of Historic Resources battlefield guidelines.

Building upon previous studies performed on portions of the site, field archaeologists spent several months expanding the surveyed limits of known prehistoric sites and Civil War earthworks, identifying similar new sites, and recovering hundreds of artifacts ranging from prehistoric Early Woodland stone tools/fragments (1100 B.C.E. – 500 B.C.E.) to lead Minié balls fired amongst brethren during the Civil War.
The curation of these artifacts and documentation of field efforts was performed in accordance with the Virginia Department of Historic Resources (DHR) guidelines. Knowing the boundaries of these historic sites allows designers to avoid critical areas and provides opportunities to connect the public to these significant places through careful placement of trails and interpretative signage. The mitigation plan for New Market Park avoids critical cultural resources. If impacts were proposed, mitigation, often consisting of additional fieldwork and expanded investigative reporting on similar features in the region to place the features in a broader historical context, would need to be agreed upon through coordination with the DHR, IRT and the design team.

Stream Channel Survey for Engineering
Investigators also evaluated stream channel conditions and surveyed representative stream channel cross sections to support design processes. The data obtained informs design engineers as to the erosion, sediment transport and water velocity in the stream and if the stream has a connection to its floodplain. With that information WSSI can identify how site hydrology is influencing the stream channel and which features can be engineered to ensure that the stream restoration design is robust and accounts for site-specific issues.


Existing Conditions Survey
WSSI performed an existing conditions survey to accurately document the locations of existing infrastructure such as existing fences, trails, upstream and downstream bridge dimensions, visible utilities, and culvert and storm structures, as well as stream and riparian features. This survey effort also established site control using Real-Time Network GPS and conventional survey techniques for use throughout the duration of the project. Bathymetric survey data was collected within the site limits of the pond occupying the decommissioned sand and gravel borrow pit (±17 acres or ±69,000 square meters) and included spot shots and 1 foot (±30 cm) contour interval topography. Additionally, elevation data was collected within the site limits of the four tributaries that are being considered for inclusion in the restoration effort (the stream and 25 feet (7.62 m) landward of top of bank) and included 0.5 foot (±15 cm) contour interval topography within these areas.


Engineering and Permitting
The prospectus and initial results of the due diligence efforts (environmental and cultural resource assessments) were used to develop a site development plan and a preliminary mitigation work plan for this project, which will be incorporated as a site in the proposed UMBI.

At the conclusion of site investigations and with feedback from the county and the IRT, WSSI will prepare a final mitigation work plan and prepare and submit a pre-construction notification and supporting documentation to the U.S. Army Corps of Engineers requesting authorization of the stream restoration project under Nationwide Permit #27.

It is WSSI’s hope that New Market Park will be the first of many sites to be included in the Single-User UMBI for Henrico County. This approach to generating compensatory mitigation credits creates a reserve of credits exclusively for Henrico County projects in a high-demand market while ecologically uplifting sites in the immediate vicinity of the inevitable impacts associated with responsible development.

Figure 2. Four Mile Creek beaver impoundment at New Market Park in summer 2023.

About the Experts

  • Beth Silverman, PWS, is the marketing manager for Wetland Studies and Solutions, Inc., a Davey company. Her background in ecology and policy informs her approach to sharing information with a range of audiences.
  • Stephen Stone, PG, PWS, is a hydrogeologist with Wetland Studies and Solutions, Inc., a Davey company. He contributed to the development of Wetbud, a wetland water budget modeling software package funded by the non-profit Resource Protection Group, Inc., and he works to identify and develop stream and wetland mitigation sites.

The Individual as a BMP

Figure 1. Training, mentorship and ongoing education is essential to equip upcoming erosion and sediment control professionals to serve as qualified individuals who can meet the challenges of the future.

Significant time, money and energy is spent sharing ideas and experiences on the various structural best management practices (BMPs) in our industry, from new geotextiles, the use of polyacrylamides, equipment advancements and the incorporation of organic products as stabilization enhancements, to highlight just a few.

It is time to include and elevate the qualified individual as a critical BMP. Given the toolbox of practices that exist for managing construction stormwater amidst the ever-changing challenges of land development, construction and natural resource management, an emphasis must be placed on the importance of the individuals that are involved in the day-to-day operations of each project.

Erosion and sediment control professionals touch every aspect of active projects in each area of our industry, from early planning, site and plan design, field inspections, assessments and review, plan and BMP implementation, to the structure of regulatory oversight and technical guidance (Figure 1). Experienced and qualified personnel are critical to ensuring success to each project, no matter how big or small, but there’s no one-size-fits-all solution to creating qualified personnel, and sadly, no quick online store of these individuals to fill your needs. As such, we as an industry must collaborate to define what we consider to be the approved standard detail or spec sheet for this vital BMP: the qualified individual.

For more than 50 years, the erosion and sediment control industry has grown and evolved on the foundation of many passionate pioneers in erosion and sediment control and stormwater management across North America, Australia and beyond. These pioneers have been and are mentors and educators for countless professionals, with an urgent need to continue and broaden the mentorship aspect. Each qualified individual has a unique set of skills and insights that contributes to the advancement of the environmental compliance and stewardship field.
To advance the growth and ensure the maturing of the industry, experienced industry professionals have a responsibility to educate, mentor and value the rising class of inspectors and young professionals. The industry’s reliance on experienced personnel is akin to the need for precision in a complex machine. Each component, or in this case, individual, must function optimally to ensure success. How these roles and qualifications are developed and defined must also factor in the changing faces and challenges of the industry. These challenges include staying relevant and demonstrating to other stakeholders that our professionals are invaluable to ensuring project success and compliance and to advancing environmental stewardship.

New employees entering the field bring fresh perspectives and new energy, which are essential for innovation. They are faced with a multitude of challenges that likely are not covered in any coursework. Providing a framework of training and continuing education for new professionals ensures that they are equipped to grow within the industry and become contributors from their own unique experiences. Mentorship and wisdom sharing may be the difference for each upcoming individual between success and retention or leaving the industry.
With all of this in mind, the IECA Erosion and Sediment Control Education Subcommittee would like to gather input to help us begin to better understand where industry professionals perceive our industry’s current standing in the development of the industry individual.
Complete a brief survey (See “Take the Survey”) to help initiate this conversation. Over the next year or more, the committee will provide a summary of the initial results and will seek further feedback from public and private organizations to learn how the industry recruits, supports, mentors and empowers new professionals. This information will form the foundation to advance the collaboration needed to develop an industry-accepted definition of the qualified individual, as well as helping to refine the framework in which professionals can earn this type of designation through combinations of work experience, education, mentorship and certification.

We all must ask ourselves, if our industry doesn’t perceive individuals as the most critical and valuable BMP, how do we expect other established industries to see our value overall? Efforts to develop better BMPs continues to be an important, focused need to combat erosion, collect sediment and obtain stabilization on our projects. Imagine the positive gains to our industry if we invest as much time in mentoring, training and adding value to the next generation of qualified individuals as we currently do in the realm of the development of structural BMPs and new technologies.

The erosion and sediment control industry is only as strong as the individuals who comprise it. By valuing each person’s contribution and investing in their growth, the industry can continue to evolve and meet the challenges of managing construction stormwater. The IECA’s initiative to gather input and share it across the community is a commendable step towards recognizing and enhancing the role of the individual in this vital field. Through articles, webinars and conference presentations, the shared experiences and strategies will enrich the collective knowledge and practice of erosion and sediment control.

About the Experts

  • Donald Pearson, EI, CPESC, CESSWI, is an assistant resident engineer on the Complete 540 Project for Summit Design and Engineering Services. He is a member of the IECA Erosion and Sediment Control Education Subcommittee.
  • Kristi Anspach, CPESC, CESSWI is the Stormwater Planning and Compliance department manager for Summit Design and Engineering Services. She serves as chair of the IECA Erosion and Sediment Control Education Subcommittee.

Take the Survey
Go to bit.ly/3y1ShLF to access The Individual as a BMP survey.

Innovative Hygroscopic Flood and Debris Resistant Material

Figure 1. Absorbcrete® FIB bags used for ocean tidal site protection – foundation repair, Malibu, California.

Innovations result from solving problems big and small, and some work, others don’t. However, all ideas can lead to more and better innovations. In the flood and erosion control industry, there are many new ideas that incorporate the concepts of sustainability, durability, resilience and of course economy.

Professionals in the construction industry are regularly challenged to solve or improve the solution for problems. How those problems are addressed helps contractors work more efficiently, provide higher quality services and, hopefully, make a profit.

Hygroscopic flood and debris-resistant material was conceptualized and created to solve construction-related challenges. When building a new concrete seawall under an existing building on a beach in California, Warstone Innovations preemptively tried to protect the site from tidal flooding, so that a deep large mass concrete footing could be installed. There was limited use of heavy equipment to excavate beach sand for the seawall. It was decided to install a perimeter sandbag wall on the site, parallel to the ocean. The sandbags were manually filled and placed 6 feet (2 m) in depth and 6 feet (2 m) high, tying into existing seawalls adjacent to the project. There were 3,000 sandbags in total. It took a full crew of workmen five days to fill and stack the sandbag wall. Work was performed in mid-August with normal summer weather and normal tidal conditions.

Since the new concrete footing was large and workspace limited, the concrete was placed in slots, with a total of four slots for the project. The concrete pour for the two end slots was complete when the weather began to change, and an unusual small summer storm formed and quickly approached the location. This storm caused some beach erosion allowing the tide to reach the sandbag wall. The sandbag wall held fast at first, and concrete for the third slot was poured. The storm intensified in the afternoon and the rain and tide brought flotsam from damaged structures and tree branches. Upon arrival the next morning to pour the last concrete slot, workers found virtually all of the 3,000 sandbags had been washed away. Workmen scoured the beach collecting empty sandbags and found many that had been impaled by the flotsam debris. The consensus was that if the sandbags had not been punctured by the debris, which allowed sand to leach out and dislodge the remaining bags, the sandbag wall would have held and protected the site. Needless to say, completing the last concrete footing slot took many days of hand excavating and became very costly. This experience proved that a different, better, more resilient protective device was needed.

Figure 2. Aquarium test of hygroscopic fiber/cement material recorded the absorption speed of water that correlated to the increase in hybrid material weight.

Innovations are almost never just a single idea. They are concepts that require maturation, running mental scenarios and asking the “what if” and “what about.” Eventually, a solid idea becomes an innovation. In this case, the theory was that the sandbag wall would have remained in place to protect the project site if the bags were filled with a solidified material that would not leach out when breached.

The resulting product is a hybrid material that is a reusable, lighter dry weight, sand-filled bag alternative (Figure 1). The hygroscopic material is composed of proportionately mixed natural hollow fibers with cement, sand and aggregate to provide an extended service life and durable matrix for an array of purposes. This innovation brings resiliency and efficiency as a new tool to economically manage the dynamics of the evolving climate-changing world.

There are several sandbag alternatives currently available, however, most are used for larger flood control scenarios, while the Warstone innovation dramatically improves the use of sand for protection. Studies have been performed comparing costs of sandbags versus sandbag alternatives, with the overall conclusion that sandbags are cost effective for a single use, but sandbag alternatives are more economical and more sustainable for multiple uses.1
The natural fiber and cementitious material mix is super absorbent and retains a volumetric weight gain when exposed to water. The dry mix will increase in weight by approximately 60% per volume. When the flooding waters recede, the retained water in the bag will slowly evaporate back to almost its original dry weight, and when exposed to water again, it will re-absorb the water and return to its hydrated weight. Initially, the hydrated mix will harden and become somewhat fixed, thereby becoming cohesive and greatly resistant to impact forces that generally debilitate traditional sand-filled bags.

This lighter dry material is sustainable, reducing overall transportation costs per coverage area of protection. The hybrid material uses less equipment and labor for deployment and removal and can be reused at least five times, including in extreme temperature conditions. This material can be used in a wide variety of containers from sandbags, interlocking bags and bulk geotextile containers.
The natural fibers are from coir, a byproduct of coconut production. Coir is naturally more resilient to saltwater than other natural fibers, making this mix universal for flood protection in fresh and saltwater conditions. When the protection use for this material has been exhausted it can be repurposed as a filter layer of a rock revetment or scour blanket among other uses.

The hygroscopic natural fiber and cementitious material mix has been extensively tested at Texas A & M University, Zachry Department of Civil and Environmental Engineering, through the Center for the Integration of Composites in Infrastructure, a National Science Foundation program.2 Laboratory testing included the proportionality of the fibers with respect to absorption and dehydration results at various temperatures for potable and saltwater (Figures 2 and 3). Strength characteristics have been studied and an academic research paper with final results will be presented in September 2024. 

Figure 3. Graphs indicating volumetric weight change vs time of hygroscopic fiber/cement materials at various percentages of fiber.2 Performed using saltwater during two hydration cycles.

References:

  1. Lankenau L, Massolle C, Koppe B, et al. Sandbag replacement systems – a nonsensical and costly alternative to sandbagging? Natural Hazards and Earth System Sciences 2020, 20(1), 197–220. https://doi.org/10.5194/nhess-20-197-2020.
  2. Ramineni K, Congress SSC, Biswas N, Puppala AJ, & Kriegstein S (Accepted). “An Experimental Study to Evaluate the Performance of Fiber-Based Cement Mixture Bags as Alternative Flood and Erosion Barriers.” ASCE GeoEnvironMeet 2024, Portland, OR.

About the Expert
Stewart Kriegstein is founder and inventor at Warstone Innovations LLC. A retired, seasoned general engineering contractor with 40 years of expertise in coastal engineering construction, he provides consulting services and is actively involved in entrepreneurial ventures related to multiple patents.

Microplastics Equal a Macro-Problem

Figure 1. Environmental Intern Laiken Cash holds a stormwater sample collected from one of four sites included in the research.

Micro-plastics are everywhere. They’ve been discovered in the deepest ocean trench, the most remote arctic ice and, perhaps the most frightening place of all, inside the human body.

Traditionally, microplastic research has centered around the marine environment. Almost everyone is familiar with the Great Pacific Garbage Patch, a collection of marine debris in the North Pacific Ocean that has produced images of straws in the noses of sea turtles and plastic accumulations in the stomachs of seabirds. However, limited research on the presence of microplastics in freshwater ecosystems has been conducted and even less research is available about the impact of microplastics on stormwater runoff.

What is clear is that urban streams are suffering from an onslaught of plastic waste, and the City of Springfield, Missouri, USA, is no exception. A series of rapid trash assessments conducted by city staff found an average of 139 pieces of individual trash per 100 linear feet of stream. Trash was divided into categories that included plastic, metal, glass and paper and ranged in size from small cigarette butts to large items like furniture and tires. Plastic made up 60% of all trash surveyed and of this plastic material, the majority was single-use food-related plastics which was followed in second place by plastic bags.

While the volume of visible plastic was interesting, city staff was primarily interested in plastics that could not be seen.

Figure 2. Fibrous microplastics found in low-intensity parking lot as photographed by fluorescent microscope.
Figure 3. Globular microplastics found in low-intensity parking lot as photographed by fluorescent microscope.

To better understand the scope of microplastic pollution in stormwater runoff, the city hired an environmental intern who spent six months reading literature, experimenting with testing methods and analyzing samples. A pre-med student whose academic research focused on the inflammation response of mammalian cells to eco-coronated microplastics was selected for the position. Quantifying microplastics in stormwater runoff was a perfect complement to her academic research and her connection to Drury University provided the city with unique access to laboratory equipment and the oversight and expertise of university professors.

City and university staff collaborated to establish a research plan. Sample locations were selected based on their potential to contain plastic pollution. A total of four locations were selected: a plastic recycling facility, an artificial turf field, a low-intensity parking lot and a high-intensity parking lot. Samples were collected in glass jars (Figure 1) using common best practices such as allowing for 72 hours from any previous storm events and collection during the “first flush.” Over the 6-month period, a total of seven storm events were sampled. In the lab, samples were filtered through a series of sieve stacks down to a size of 45 microns. The 45-micron sieve was backwashed with deionized water and collected for analysis. From there, 10-microliter samples were dyed with Rhodamine B dye and heat-fixed to microscope slides for observation under a fluorescent microscope.

A series of images were taken of 10-microliter stormwater samples using the fluorescent microscope. Because we observed that exposure affected the number of particles visible, a series of three photos were taken of each sample, at exposures of 200, 500 and 1,000. Therefore, final estimates are representative of the average of these three exposures. Of the observed microplastics, there were two distinct morphologies: fibrous (Figure 2) and globular (Figure 3). It appeared that globular particles were indicative of rubber material and tire wear, whereas fibers were associated with the breakdown of larger materials, such as textiles and cigarette butts. However, we did not perform Raman spectroscopy testing to determine the makeup of the plastic material due to lack of access to this technology. Instead, our study focused on quantification, and this was accomplished with an image processing software called Fiji. The images in Figures 2 and 3 are the same 10-microliter samples viewed through Fiji software.

Figure 4. Summary of microplastic particles by sampling location and storm event.

Fiji software uses artificial intelligence to count the number of particles in each image and generates the results in a spreadsheet. From there, it’s just a matter of math to estimate the total particles per liter of stormwater runoff. The study determined that, on average, one liter of urban stormwater runoff contains millions of microplastic particles. The high-intensity parking lot, plastic recycling facility and artificial turf field averaged approximately eight million particles per liter, while the low-intensity parking lot averaged roughly half that value (Figure 4).

An important part of the study was to also evaluate the effectiveness of green infrastructure in removing microplastics from stormwater runoff. Using a density separation methodology, sediment samples from a detention basin were evaluated and found to contain microplastic particles. This indicated that some quantity of plastic is removed from stormwater runoff and captured within the stormwater feature. An ex-situ study utilizing a series of five-gallon buckets was performed to estimate the efficiency of removal. They were filled with bioretention media and planted with native vegetation, and holes were drilled on the bottom to allow them to drain (Figure 5). After a period of establishment, water with a known microplastic concentration was run through the buckets. The effluent was analyzed and compared to the influent to estimate removal efficiency, which was found to be approximately 85%. This supported existing research that found bioretention cells to have a median microparticle percent reduction of 84%.1

The good news is potential solutions to help address the macro-problem of microplastic pollution already exist. While bioretention is not going to solve the plastic pollution crisis any time soon, it is certainly one tool in the toolkit, and one that more communities will adopt as they implement green infrastructure to treat stormwater runoff.

Figure 5. Bioretention buckets were used to estimate microplastic removal.

The City of Springfield has also installed several trash nets, increased its volunteer stream and road cleanup efforts and focused more on educational efforts related to littering and plastic pollution. An example of this targeted education is the new ballot bin device (Figure 6) installed in downtown Springfield, which educates pedestrians about the connection of cigarette butts to plastic pollution and encourages them to “vote” for an answer with their used butts.

As more pollutants emerge, education is everything. As Maya Angelou said, “Do the best you can until you know better. Then, when you know better, do better.” 

Reference

  1. Smyth K, Drake J, Li Y, et al. Bioretention cells remove microplastics from urban stormwater. Water Research. Vol. 191, 2021. 116785, ISSN 0043-1354.


Note
The City of Springfield thanks Environmental Intern Laiken Cash and her academic advisor, Rachael Day, Ph.D. for their work on the project. Cash was supported by the City of Springfield and Drury University through the Research Experience in the Natural Sciences program, and Day was supported by Drury University.

About the Expert
Sarah Wilkerson, CESSWI is a senior stormwater specialist at the City of Springfield, Missouri. She has over 10 years of experience in the stormwater industry and holds undergraduate and graduate degrees in biology and environmental science.

Using Recycled Materials to Prevent Stormwater Pollution

Figure 1. Illustration of absorbent media trapping hydrocarbons and letting water pass through.

Although innovation is often defined as a new idea or product, it can also be used to describe finding a new use for an existing product. The unlikely story of how an oil spill absorbent became an effective control for stormwater pollution in Australia and the United States is a perfect example.

Repurposing Textile Waste
Every year, 92 million tons of textile waste is produced globally.1 To put that figure into perspective, this weight is the equivalent of 250 Empire State Buildings. Textile waste is a growing issue that’s facing increased significance, and one United States-based company has found a unique way to help tackle the textile waste problem. Halen Hardy specialises in spill control products and has developed a production method that takes old clothes, furniture and bedding, then breaks them down to base fibres. These fibres are then heat pressed to convert them into an absorbent media known as Spilltration Husky.

This recycled absorbent media has some impressive characteristics. First and foremost, it absorbs hydrocarbons. While water is absorbed, it is not retained by the material. These unique characteristics have made the absorbent media popular for use in traffic emergency response because oil and fuel spills can be absorbed while rainwater filters through the media (Figure 1). The ability to filter water is maintained, even when saturated by oil.

Figure 2. Polyethylene mesh provides structure and protection from vehicles traffic.


Utility for Sediment Filtration
A secondary benefit was discovered after the recycled absorbent media’s popular use as an oil spill absorbent. It was found that the absorbent could also be used to become a filter to trap sediment in addition to hydrocarbons.

To quantify its performance, the absorbent’s filtration performance was tested by an independent laboratory. A series of tests showed conclusively the material had the ability to effectively trap particles as small as 53 microns (0.053mm). For reference, particles of this size are finer than the average human hair.

The absorbent media’s unique construction plays a key role in its filtration ability. Fibres are bonded and heat pressed without the use of additives, and this composition enables water to be drawn into and wick through, helping to maintain filtration in sediment control applications.


Adding Durability for Long Term Usage
The recycled absorbent media showed promise for stormwater protection as a drain filter, however, improving its durability to withstand long-term foot and vehicle traffic presented a design challenge.

In its standard form, the recycled absorbent would result in piling and eventual disintegration when exposed to prolonged and direct contact. Extensive testing showed that these effects could be mitigated by adding a protective outside layer to prevent lateral movement of the absorbent media.

Polyurethane mesh was chosen to protect the absorbent media because of its UV resistance and inherent durability. The mesh is sewn directly to the absorbent media (Figure 2), with eyelets for added strength and to secure the drain filter in place once installed.

For maximum effectiveness in installation the drain filter is positioned over stormwater drains with a slight overhang. It is compatible with box, v-grate and side inlet stormwater drain types. Drain filters also feature a raised center section, which helps to create a damming effect to further improve the capture of sediment during heavy rain. Additionally, an overflow port helps to prevent water from backing up in heavy rain events. For side inlet stormwater drain systems, inbuilt aluminum strips are utilised to achieve a tight fit around curbs. The filter can be cleaned using a hose from behind to further extend its lifespan.


Real-world Applications
Construction sites, rail yards, car parks and gas, energy and manufacturing facilities are common risk areas for stormwater pollution that can benefit from the installation of a drain filter. In Australia and New Zealand, the drain filter is known as the GuardDog Drain Filter. In 2021, it was verified by the Innovation Sustainability Council as an Australia-first innovation for use on a major freeway upgrade (Figure 3). Since then, it has been used on countless construction projects. In the United States and Canada, the drain filter is known as the HuskyGuard. It has been specified as best management practice on major class 1 railroads and for the construction of a major petrochemical plant in Pennsylvania.


Benefits over Traditional Solutions
Aside from the sustainability benefits, the drain filter presents multiple advantages over traditional sediment control methods such as silt socks and drain pollution guards. The drain filter features a low-profile design, which improves safety for pedestrians and cyclists. Silt socks are also susceptible to splitting as they age or when driven over. This can result in debris spilling on the road and into stormwater drains.
Drain filters installed over stormwater drains make the prospect of an overloaded drain cavity unlikely. Moreover, time spent maintaining and cleaning filters is less than that of in-drain alternatives, as litter and debris can be swept away by hand or streetsweeper.


Moving Towards Sustainable Partnerships
Pollution prevention solutions such as the drain filter highlight the value of sustainable partnerships. Such partnerships extend beyond a conventional business relationship, due to a shared commitment towards environmental challenges. This synergy helps to bridge the gap between environmental responsibility and innovative solutions, resulting in a win-win for the stakeholders involved.

The relationships with end users who are seeking a fit-for-purpose solutions with additional sustainability benefits are very important. The value proposition of a stormwater pollution control device does not relate to the drain filter itself but to the journey towards jointly-crafted solutions that optimize performance, efficiency and environmental impact. 

Figure 3. Side entry GuardDog Drain Filter installed on the Monash Freeway upgrade project in Melbourne, Australia.

Reference

  1. Ellen MacArthur Foundation. A new textiles economy: Redesigning fashion’s future (2017).


About the Expert
Martin Brown is the marketing manager at Stratex, an Australian leader in environmental and personal protection solutions. He specialises in marketing and digital transformation and has worked with many of the world’s leading organizations in technology, healthcare, hospitality and safety.

Thinking of Forests and Beaches

Figure 1. Drone images of the Australian beach before (2019, top) and after (2021, bottom) nourishment. The seawall and building were removed prior to bringing the sand. A dune and vegetation established where the building was. Photo credit Brendan Kelaher, Southern Cross University.

This is the time of year when many folks are planning to head to the woods or the beach for a summer vacation, so here are a couple of studies in those areas.

Beach Protection

Beach nourishment is a common practice in which sand is added to an eroding beach as a way to reverse the erosion process at least temporarily, often to protect property and maintain recreational value. This process was initiated for a beach on an island 500 km off the coast of Australia in order to protect a vital road, and the transformation and stability of the nourished beach was monitored for a year after completion.2


The project involved moving sand from the northern part of a 1.34 km lagoon beach to the southern part, along with the removal of a dilapidated seawall and a building at the southern end. The lagoon has relatively low wave energy due to protection provided by sandbars and reefs. A commercial unmanned aerial vehicle (UAV) was deployed to survey the area before, during and after the sand was moved and for a year afterward. The photos were used to develop 3D orthomosaics from which changes to the beach topography could be determined.
A local resident was trained to perform the automated UAV surveys, which was critical due to travel costs and restrictions due to COVID. The survey results indicated that approximately 8,200 m3 of sand were moved, close (4% less) to the estimate based on truck volumes. At the end of the monitoring, 71% of the sand moved remained on the south beach (Figure 1). In addition, a new dune structure was established and vegetation was colonizing it. The slope of the middle and south ends of the beach declined, possibly due to accretion during the period. The authors found that the use of relatively simple and inexpensive commercial UAVs can be a valuable tool for monitoring similar types of projects.


Debris as Sediment Control

When you think of a forest area after a major fire, you may picture lots of burned tree trunks lying on the slopes. Could that debris be a substantial source of sediment control? That was the question that a team of researchers addressed for an area that burned in 1998 in southwest Montana, USA.1


They obtained high-resolution aerial photographs taken in 2016 and analyzed 55 areas 40 m in diameter for downed tree trunks of at least 28 cm in diameter, the minimum resolution in the images. The slope characteristics, log length and orientation of the logs relative to slope were determined and used this information to estimate the amount of potential storage based on available volume above the logs. Logs oriented more than 45 degrees from the flow direction were not included. In addition, the effects of slope and log orientation were tested on a tiltable table with a 5.1 cm PVC pipe representing a log and coarse sand poured at the top of the table representing eroded sediment.
Once a stable elevation above the simulated log was achieved, photographs were taken and used to develop digital elevation models for analyses. For logs of 25 cm and 50 cm in diameter, the storage potential averaged 0.5 and 2 m3, respectively. Taken over the 1 km2 watershed, there was 3,500 to 14,000 m3 in potential storage behind the two log sizes. Surprisingly, there was no correlation between the log distribution and slope characteristics or burn severity.
Tests on the tilted table also produced some surprising results. At 30 and 45 degree slopes, the coarse sand piled up behind the simulated log much higher than predicted, while at 60 degrees the predicted and actual volumes were similar. Little accumulation occurred when logs were oriented less than 30 degrees to the flow direction. Overall, the authors suggest that their estimate of potential storage could be conservative based on the tilted table results.  

References:

  1. Adams, K. V., J. L. Dixon, A. C. Wilcox, and D. McWethy. 2023. Fire-produced coarse woody debris and its role in sediment storage on hillslopes. Earth Surf. Process. Landforms. 2023;48:1665–1678. DOI: 10.1002/esp.5573.
  2. Kelaher, B. P., T. Pappagallo, S. Litchfield, and T. E. Fellowes. 2023. Drone-based monitoring to remotely assess a beach nourishment program on Lord Howe Island. Drones 2023, 7, 600. DOI:10.3390/drones7100600.


About the Expert
Rich McLaughlin, Ph.D., received a B.S. in natural resource management at Virginia Tech and studied soils and soil chemistry at Purdue University for his master’s degree and doctoral degree. He has retired after 30 years as a professor and extension specialist in the Crop and Soil Sciences Department at North Carolina State University, specializing in erosion, sediment and turbidity control. He remains involved with the department as professor emeritus.

Adaptive Strategies of Common Buttonbush at Developed Lake Margins

Figure 1. Study area.

Impounded lakes provide essential water supply, flood control and hydropower to cities worldwide, but they also inundate habitat, lose water by seepage and evapotranspiration, and capture sediment that takes up storage and would otherwise replenish downstream environments. Rivers and shore areas input most of the sediment trapped in built reservoirs, and unconsolidated deposits are especially vulnerable to wave erosion in shore areas.

Some forms of natural vegetation such as buttonbush (Cephalanthus occidentalis L. [Rubiaceae]) can bind shore sediment while providing a habitat for birds and other animals. Often found in floodplains and riparian zones, buttonbush naturally occupies parts of southeastern Canada and the eastern United States, extending westward to eastern Texas, Oklahoma, Kansas, Iowa, Wisconsin and Michigan.1 Scattered populations of buttonbush are also found in Arizona, New Mexico, southern California and northern Mexico.

Common buttonbush is a hardy shrub with an irregular crown, spheres of white flowers and button-shaped fruit.2 Buttonbush typically blooms in summer, produces fruit in early fall and reaches a height of approximately 3 m (10 feet) at maturity.3,4 Birds consume buttonbush seeds, mallards (Anas platyrhynchos) eat its fruit, wood ducks (Aix sponsa) use it for nests, and deer browse its foliage.5,6,7,8 Buttonbush also provides nectar to bees, butterflies, moths and hummingbirds (Trochilidae).9,10 Three types of moths, the hydrangea sphinx (Darapsa versicolor), titan sphinx (Aellopos titan) and royal walnut moth (Citheronia regalis), use buttonbush as a larval host.11
Buttonbush has no major insect, pest or disease problems.12 Along lake shores, buttonbush can form dense stands, with swollen bases that anchor shrubs and bind sediment.13,14 Through adaptation, buttonbush also tolerates disturbance from humans. A study along a segment of lake shore in north-central Texas explored adaptive strategies to wave erosion, pruning and mowing.

Study Area
The study area is located near the northern edge of Lewisville Lake in north-central Texas (Figure 1). This large, multi-use reservoir is impounded by an earthen dam located 16 km (10 miles) south of the study area. Lewisville Lake provides water to local cities and water authorities, controls flooding and supports recreation such as fishing and boating. The lake’s maximum normal operating level (conservation pool) is 159.1 m (522 feet) above mean sea level.15 The lake tends to rise above and fall below conservation pool each year, except during drought. Winds create waves that impact the study area from all directions, with a relatively strong SSE mode over a typical year.
Along the shoreline, a thin blanket of Quaternary alluvium (terrace) overlies bedrock of the Upper Cretaceous Woodbine Formation. In the study area, the Woodbine Formation consists predominantly of loosely cemented sandstone and clay. Overlying terrace deposits comprise sand, gravel and clay. Soil has formed and remains intact, but is eroding, on terrace deposits at the back of the shore.

Figure 2. Shrubs withstanding pruning. 1 m (3.28 feet) pipe for scale.
Figure 3. Shrubs withstanding erosion. 1 m (3.28 feet) pipe for scale.
Figure 4. Shrubs growing in grass-covered alluvium. 1 m (3.28 feet) pipe for scale.
Figure 5. Shrubs growing in bare alluvium. 1 m (3.28 feet) pipe for scale.


Observations
Buttonbush was observed and photographed along a representative segment of developed shore. Photographs were taken on 22 May 2023, when lake elevation was 159.4 m (522.7 ft) above mean sea level.16 Buttonbush was growing in a narrow elevation range, within approximately half a meter (1.6 feet) of conservation pool. Shrubs were anchored into both alluvial deposits and the underlying Woodbine Formation.

Shrub heights ranged from less than 1 m (3 feet) to approximately 3 m (10 feet). At ground level, plant diameters ranged from less than 1 cm (0.4 inch) to approximately 10 cm (3.9 inches). Based on growth rings of cut shrubs and associated diameters, shrubs ranged from less than one year to approximately 20 years old. Having survived frequent wave action, and in some cases pruning and mowing from adjacent landowners, mature shrubs were binding sediment and providing habitat to various fauna.

Three adaptive strategies were observed: regrowth below pruned branches, root anchoring and seed dispersal. New branches typically emerged within a few centimeters (1 inch) of the cut level on a branch, often taking a similar trajectory to the pruned branch (Figure 2). In some cases, entire shrubs lopped off at ground level sprouted new stems around the perimeter of the stump.

Several shrubs had been undermined by wave erosion but were still thriving (Figure 3). Typically, undermined shrubs adapted by hardening exposed roots into three or more supporting legs connected at the top by the exposed root ball. Each supporting leg developed a new root ball beneath the ground for stability.

Exposed root balls document previous ground levels, thereby facilitating erosion rate estimates. For example, an approximately five-year-old, partially submerged shrub in one location of the study site indicates about 50 cm (19.6 inches) of denudation over five years, or 10 cm (3.9 inches) per year. Concurrently, the backshore terrace retreated about 1 m (3 feet) over the five-year period. Such erosion estimates can be useful to planners, to guide or prioritize restoration efforts that might involve additional plantings or other stabilizing structures.
Seed dispersal was the most important adaptive strategy. Nearly 300 seeds were counted in a single fruit ball in the fall of 2022. Dispersed seeds were examined on a contrasting, white paper background and appeared healthy: of characteristic shape, size and color; plump, full and fresh; devoid of shriveling, mottling or other damage; and free from pests and disease. Moreover, each mature shrub typically produced 20 or more fruit balls, thus releasing thousands of seeds per shrub. With such volume, even low survival rates result in considerable propagation. Seeds showed propensity to grow in Bermuda grass that invaded the study area, as well as in reworked sediment above hummocky bedrock.

Grass cover protected settled seeds from water and wind. Seedlings and shrubs grew in grass along the edge of the terrace and below the terrace (Figure 4). Typically, the edge of the terrace escaped mowing, but not less frequent string trimming. At the terrace edge, up to 20 seedlings were growing in a square meter of turf grass. In some cases, property owners trimmed Bermuda grass around buttonbush shrubs, preserving them as ornamental features for aesthetic value.

Seeds also settled into micro-depressions between hummocks formed by concretions in bedrock (Figure 5). Concretions form inside sediment shortly after deposition, as minerals precipitate from solution, sometimes as successive layers around a nucleus such as a granule, plant remnant or small shell.17 Between exposed concretions, which are relatively resistant to erosion, sediment and moisture accumulated to nurture seeds and support plants. Some plants were growing inside broken concretions. Eventually, roots propagated through cracks inside concretions, or into sediment between concretions, and anchored into more stable underlying deposits.

Conclusion
Buttonbush in the area is hardy, surviving not only frequent wave activity, but also indiscriminate pruning and mowing from adjacent property owners. Key adaptive strategies that include root anchoring, branch regrowth and seed dispersal, enable buttonbush to thrive in this setting. Buttonbush is valuable, providing habitat to various animals, stabilizing the shoreline, and enabling estimates of erosion rates to inform shoreline stabilization efforts. 


References

  1. LBJWC (Lady Bird Johnson Wildflower Center). 2023. Plant Database. Lady Bird Johnson Wildflower Center, Austin, Texas. Available from: https://www.wildflower.org/plants/result.php?id_plant=ceoc2.
  2. LBJWC 2023.
  3. Polomski, R.F. and Feder, B.H. 2020. Common Buttonbush. Factsheet HGIC 1098. Clemson Cooperative Extension, Clemson University, Clemson, South Carolina. Available from: https://hgic.clemson.edu/factsheet/common-buttonbush/.
  4. Wennerberg, S. 2004. Common Buttonbush (Cephalanthus occidentalis L.). Natural Resources Conservation Service, United States Department of Agriculture. Available from: https://plants.usda.gov/Document Library/plantguide/pdf/pg_ceoc2.pdf.
  5. Little, E.L. 1980. The Audubon Society Field Guide to North American Trees: Eastern Region. Knopf, New York.
  6. Niering, W.A. and Olmstead, N.C. 1985. The Audubon Society Field Guide to North American Wildflowers: Eastern Region. Knopf, New York.
  7. Parr, D.E., Scott, M.D. and Kennedy, D.D. 1979. Autumn movements and habitat use by wood ducks in southern Illinois. Journal of Wildlife Management, 43(1), 102-108.
  8. Wennerberg 2004.
  9. Snyder, S.A. 1991. Index of Species Information. Fire Effects Information System, U.S. Department of Agriculture. Available from: https://www.fs.fed.us/database/feis/plants/shrub/cepocc/all.html.
  10. Wennerberg 2004.
  11. Wheeler, J. 2017. Planting for Pollinators: Buttonbush. Xerces Society for Invertebrate Conservation, Portland, Oregon. Available from: https://xerces.org/blog/planting-for-pollinators-button-bush#:~:text=In%20addition%20to%20its%20attractiveness,walnut%20moth%20(Citheronia%20regalis).
  12. Polomski and Feder 2020.
  13. Polomski and Feder 2020.
  14. Wennerberg 2004.
  15. USACE (U.S. Army Corps of Engineers). 2023. Lewisville Lake. Lewisville Lake Project Office, U.S. Army Corps of Engineers, Lewisville, Texas. Available from: https://www.swf-wc.usace.army.mil/lewisville/.
  16. USGS (U.S. Geological Survey). 2023. Lewisville Lake near Lewisville, Texas. Available from: https://waterdata.usgs.gov/monitoring-location/08052800/#parameterCode=62614&timeSeriesId=139931&start DT=2022-01-01&endDT=2022-12-31.
  17. Todd, J.E. 1903. Concretions and their geological effects. Bulletin of the Geological Society of America, 14, 353-368.

About the Expert
Paul F. Hudak, Ph.D, is a professor in the Department of Geography and the Environment at the University of North Texas.

Removing PFAS from Precipitation-Induced Runoff from Land Application Systems

Figure 1. Setup to test the tracer dye and PFAS removal percentages as liquid leaches through a soil and sawdust blend. Each cylinder contains a different mix of soil and sawdust.

Water used to wash clothes and dishes, take baths and showers, flush toilets and mix with cleaning products makes its way from houses to wastewater treatment plants for people on public water and wastewater systems. After passing through the wastewater treatment process, the treated water is either discharged to the local waterbody or land applied for infiltration into the soil profile. At this point, wastewater system operators must also consider the erosion and sediment control practices that are in place to avoid contamination of waterways due to runoff after precipitation events.

Products that contain per- and poly-fluroalkyl substances (PFAS) or “forever chemicals” are commonly used in homes. These are synthetic chemicals that were originally synthesized in the 1930’s1 and have since found many different uses where waterproofing needs are desired. Some products that contain PFAS are Teflon™ pots and pans, waterproofing compounds, makeup and carpeting. PFAS are comprised of carbon-based compounds in which the carbon has been chemically bonded to fluorine atoms. With the high electronegativity of these carbon-fluorine bonds, a high activation energy is required to break these bonds making treatment and removal challenging.2,3
At some wastewater treatment plants, instead of discharging the treated water into a waterbody, the treated water is sprayed on a land application system (LAS). Land application systems can consist of grassed fields, forest or a combination of the two. These systems are covered under NPDES permits, and there is a requirement that no runoff should occur from the facility. However, during precipitation events, there could be runoff from the site causing soil erosion. This stormwater could carry chemicals on the surface of the LAS or attached to eroded soil particles. Around the LAS is a buffer zone to slow down and retain any soil, nutrients and other chemicals contained in the runoff. There have been some studies of buffer zones and their ability to retain and reduce nutrient levels as the water moves through the buffer zone, but there has been little to no research on the buffer zones’ ability to retain PFAS. A study is currently being conducted to answer some of these questions, but results are not currently available as samples from the project are being analyzed.
Along with the current research on buffer zone retention of PFAS, researchers at the University of Georgia are investigating the potential of using stormwater practices such as bioretention basins or modified versions to retain and remove PFAS prior to final discharge to local waterbodies. Initial studies involved the use of column studies to determine removal percentages of PFAS from a solution of six PFAS chemicals typically found in wastewater treatment plant effluent and applied to LAS. This solution consisted of the PFAS chemicals, perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), 6:2 fluorotelomer sulfonate (6:2 FTS), perfluorobutane sulfonic acid (PFBS) and perfluorohexane sulfonic acid (PFHxS). The objective of the column study is to determine if a combination of materials available at LASs in both North Georgia and South Georgia could be used to retain and reduce the concentrations of PFAS leaving LASs from precipitation-induced runoff.

In Georgia, the northern portion of the state is classified as Piedmont, and the soil profile is comprised of clay-based soils. The southern portion of the state is a coastal plain, and the soil profile is comprised of loamy sand soils. This study investigated the use of these two types of soil (a Pacolet Clay representing North Georgia and a Tifton Loamy Sand representing South Georgia) which could be found on the LAS site mixed with sawdust. Blends were made of soil and sawdust in ratios of 100%/0% (soil/sawdust) to 0%/100% with 20% changes in each portion of the blend. Each of the six mixtures was added to small stainless-steel columns that were 5.5 cm (2.2 inches) in diameter and 28 cm (11.0 inches) in length with screen mesh on the bottom to contain the mixture. Once the mixture was added, the columns were dropped from a height of 10 cm (4 inches) onto a surface to provide a consistent packing of the mixture. The columns were then hung from a rack and 500 mL (16.9 ounces) of liquid containing either a tracer dye or PFAS water was introduced to leach through the mixture. Collected samples were analyzed for fluorescence or PFAS concentration (Figure 1).

The analysis of PFAS removal percentages for the clay and sawdust (Figure 2) shows that as the percentage of clay decreases in the mixes, the removal percentages of PFAS also decreased. Some of this is related to the PFAS chemical in itself. The chain length of PFAS affects adsorption or desorption; shorter chains partition to water and longer chains are preferential to soil.4,5 The cation exchange capacity of the soil/sawdust mixture appears to have some affect on the removal pecentages of PFAS. As sawdust becomes the predominate portion of the mixture, the fluoresence of the collected sample, as indicated by the tracer dye values, increases. Some trees will naturally have a fluoresence due to the componds in lignin of the tree.6 The sawdust used for this experiment was collected from a local sawmill where the wood consisted of conifers as well as hardwood.

As the percentage of loamy sand decreases from 100% to 20%, there is not much change in the removal percentages of PFBS, PFHxS, PFOA and 6:2 FTS (Figure 3). PFOS and PFNA have higher removal rates in the 100/0 mixture while the percentage of removal generally decreases with increasing sawdust until the 0/100 mixture. At 0% soil, five of the chemicals increase in removal percentage. With this soil being a loamy sand, the attraction to the soil particles could be causing a lower adsorption rate and therefore a reduced removal percentage for the PFBS, PFHxS, PFOA and 6:2FTS. Clay soil typically has a negative charge, while sandy soil may have slight negative or no charge.

The research is continuing, but the potential of using on-site materials as well as materials that are collected from citizens in county/city-based debris removal can potentially be cost-effective ways to capture and retain some of the PFAS that potentially could be in precipitation-induced runoff from LAS sites where this system is used. 

Figure 2. Removal percentages of PFAS and tracer dye along with cation exchange capacity after leaching through a mixture of clay and sawdust.
Figure 3. Removal percentages of PFAS and tracer dye after leaching through a mixture of loamy sand and sawdust.


References

  1. Moyer M. (2021). “Forever Chemicals”: PFAS Contamination and Public Health. Penn State Law Review, 2021. https://www.pennstatelawreview.org/print-issues/forever-chemicals-pfas-contamination-and-public-health/. Last viewed 16 January 2024.
  2. Zhang Z, Sarkar D, Biswas J K, et al. (2021). Biodegradation of per- and polyfluoroalkyl substances (PFAS): A review. Bioresource Technology, 2021, 1–11. https://doi.org/10.1016/j.biortech.2021.126223.
  3. Drenning P, Volchko Y, Ahrens L, et al. Comparison of PFAS soil remediation alternatives at a civilian airport using cost-benefit analysis. Science of the Total Environment, 2023, 1-11. http://dx.doi.org/10.1016/j.scitotenv.2023.163664.
  4. Huang Y, Liu S, Zi J, Cheng S, et al. In Situ Insight into the Availability and Desorption Kinetics of Per- and Polyfluoroalkyl Substances in Soils with Diffusive Gradients in Thin Films. Environmental Science and Technology, 2023, 7809-7817. https://doi.org/10.1021/acs.est.2c09348.
  5. Seo S, Son M, Shin E, et al. Matrix-specific distribution and compositional profiles of perfluoroalkyl substances (PFASs) in multimedia environments. Journal ofHazardous Materials, 2019, 19–27. https://doi.org/10.1016/j.jhazmat.2018.10.012.
  6. Djikanovic D, Kalauzi A, Radotic K, et al. Deconvolution of Lignin Fluorescence Spectra: A Contribution to the Comparative Structural Studies of Lignins. Russian Journal of Physical Chemistry A, 2007, Vol. 81, No. 9,pp. 1425–1428. DOI: 10.1134/S0036024407090142.

About the Experts
Gary L. Hawkins, Ph.D., is an associate professor and water resource management extension specialist at the University of Georgia.
Bailey Williams, B.A., is a graduate student in the University of Georgia Crop and Soil Science Department.

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