Effective master planning water and wastewater systems can contribute to the success of your business. Master planning enables utilities to develop a strategy for funding infrastructure as well as determining the efficient timelines for the implementation of facilities and individual utility components.
Many utilities have the daunting task of prioritizing projects and allocating funds to maintain service areas. To do this, it is important to assess the existing conditions of the current infrastructure and identify critical areas that need to be addressed. Master planning answers 3 major questions for the utility through technical, operational, and financial evaluations –
What projects do I need to do?
When do I need to do these projects?
How am I going to pay for these projects?
For a utility, master planning involves a number of steps with the ultimate goal of developing a plan to achieve long term sustainability. The following provides the basic outline of the steps in developing a master plan for utility:
Condition of the Infrastructure
The first step in the process is inventory and evaluation of the existing assets the utility has at its disposal. It is imperative to evaluate the overall condition of all infrastructure, identify equipment that needs repair or replacement, and determine areas of the system that are currently in good condition.
By reviewing the capacity, it can be determined if the current facilities can meet the current as well as the future needs of the service area. This allows the utility to identify potential expansion areas, plan for the expansion and appropriately size the new equipment for the expected growth. This can easily be accomplished through the development of a hydraulic model of the water or wastewater network.
Water Quality Evaluation
Regulatory requirements drive the types of treatment facilities that are required or needed. Water quality evaluations are a great tool to determine if the current treatment equipment is adequately meeting current regulatory requirements. Customer expectations are also a consideration and should be addressed during this portion of the evaluation.
Repairs, Rehabilitation, and Replacement
By identifying problem areas and prioritizing repairs, costly emergency repairs and service interruptions can be minimized. This evaluation will also allow the utility to schedule and dedicate resources to specific areas that need more attention.
Operation and Maintenance
By reviewing the operation and maintenance records of a utility, opportunities for system upgrades, optimization, and increased efficiency can be identified.
When the information is collected and analyzed, a priority list can be established so that the utility can quickly address the most pressing issues.
This requires the development of a plan that acts as the “roadmap” to meet future needs and provide a vision for expansion. By projecting future growth, these long terms goals account for the vision the leadership has for the utility and charts a course for how to achieve this vision.
Identification of avenues to fund these projects is one of the most important aspects of the master planning process. It allows the utility to identify revenue sources that will fund capital projects, as well as operation and maintenance needs. This evaluation is also used to determine how to generate affordable revenue streams for the utility through its fee structure.
Ultimately, the goal of the master planning process is to develop a plan that the utility can use to better meet the current needs of its customer base while looking to address the future needs of the system through infrastructure upgrades, system expansion, and new facilities.
McFadden Engineering develops master plans that allow our clients to have a “roadmap” for future success and assist with the implementation of the plan. Let us partner will you on your future project.
Alabama is blessed to have an abundance of surface water and rainfall, maybe too much rainfall during tropical events! The state boasts 16 distinct river basins; 129,700 total miles of rivers/streams; 59,000 miles of perennial (i.e., streams that flow year-round) rivers/streams; and 490,472 acres of lakes/reservoirs/ponds. So, if you like water sports, water-front property, or enjoy wearing a raincoat and boots, you are in the right state. With an abundance of water comes the obligation and duty to manage these vital natural resources to protect them for future generations. That duty has been promulgated by the Federal Water Pollution Control Act Amendments (FWPCA, PL-92-500) in 1972 to each state where management and enforcement duties were implemented.
Alabama’s agency for these duties is the Alabama Department of Environmental Management (ADEM) that was created by the Legislature in 1982 as a separate agency from the Alabama Department of Public Health. Since then, ADEM has been the prime agency for managing our abundant natural resources of air, water, and land via permits, studies, enforcement, etc. As one of the branch managers within the agency opined many years ago, “…we must do a pretty good job since industry, municipalities, and environmental action groups all stay upset at us…”.
So, whatever your philosophy concerning environmental matters, you can find an issue where government should be doing more, or maybe less! When you think about it, to perform all the activities that would be required by an agency like ADEM requires significant funding. There have been years where ADEM, and I’m sure agencies in many other states, did not get nearly the necessary funding from the state legislatures; and if not for federal funding, fines, and fees, would cease to exist or at best have limited resources to properly manage their environmental obligations.
Consider what is required if an industry or municipality needs to discharge a wastewater to a local stream, river, or bay. Their engineers determine the flow (gallons per day) of wastewater and make an application to ADEM. In turn, ADEM must determine how well the wastewater needs to be treated to not cause a problem in the receiving stream. The most accurate way to make this determination is to have an abundance of field-collected water quality data from the receiving stream, where a water quality model can be developed to set the level of treatment required in a permit issued to the discharger. However, to collect this data takes personnel and equipment, which is a function of time and money.
There is just not enough personnel or money to do this type of study for every applicant given the limited resources of the states and the number of requests for permits that are submitted on a yearly basis. As an alternative to this massive data collection effort, the EPA has promulgated procedures to estimate the data from a field study or calibrated and verified water quality model.
This alternative is spelled out in a Memorandum of Understanding between the EPA and the respective states, including Alabama, and is known as a “desktop” water quality model. As its name implies, this model can be developed at one’s desk using the appropriate software and published historical data.
The bottom line is for a very small amount of time and equipment (typically only a desktop or laptop computer), ADEM can model the stream, determine the allowable impact from the discharge and issue the appropriate National Pollutant Discharge Elimination System (NPDES) permit to the applicant. While “desktop” modeling is not as accurate as a full-blown stream data collection study and model, it is usually accurate enough to protect the receiving water from the treated wastewater.
If this proves not to be the case, the permit can be re-evaluated if water quality issues arise, conditions change, or new discharge limits need to be issued.
In summary, I hope you can appreciate the abundant natural resources we have in our state and others. I hope that you can also appreciate the daunting task the agencies have in managing and protecting these resources while accounting for individual and corporate rights. After all, as far back when David was writing the 8th Psalm, it suggests that we humans are to manage and protect our resources.
Although we have our ongoing challenges, this effort can be accomplished while supporting growth and development. It requires working from good science and engineering without an over-dose of emotion or greed.
Our team at McFadden Engineering has a long track record of working with regulatory agencies like ADEM. Or goal is to work with these agencies so that the needs of all stakeholders are addressed and that the natural resources we enjoy are protected.
You may not have noticed it beneath the daily clamor of climate change news that permeates the media, but we are facing an environmental crisis of a different nature. (I know, you really wanted to hear about another one, right?). No, it’s not all that micro plastic swirling around in the oceans or another oil spill. Instead, it’s something that perhaps is less dramatic or visible to the public.
Per and polyfluoroalkyl substances or PFAS (pronounced “pea-foss”), have received a lot of attention from the environmental science community, activists, and stakeholders because of their toxicity to humans and wildlife. First manufactured in the 1940s, PFAS compounds are used in a wide variety of industrial applications including non-stick cookware, firefighting foam, food packaging, water repellants and stain repellants among other uses. There are over 9,000 known PFAS compounds and 600 of those are used in products in the United States.
Also known as “forever chemicals” because of their incredibly stable chemistry, these compounds can persist in the environment potentially for thousands of years. This is due to the carbon-fluorine bond, the strongest bond in organic chemistry, that is the chemical backbone of PFAS in all its forms. PFAS toxicity in humans have been known for quite some time despite their use in many everyday products.
In 2018, the State of Minnesota settled an $850 million dollar lawsuit against the 3M Corporation. The subject: PFAS contamination of drinking water resources in the Twin Cities Metropolitan Area. Court documents in that case revealed that as early as 1950, 3M determined that Perflourobutyric Acid, a common PFAS compound, was toxic in studies with laboratory mice. Another study conducted by the chemistry department at Stanford University in 1955 concluded that Perfluorooctanoic Acid (PFOA), another common PFAS compound, binds to albumin protein in blood.
How did so many Americans end up with PFAS in their bodies? When environmental engineers and geologists analyze a site that has known chemical contamination, we often conduct what’s called a Health and Safety Risk Assessment. One of the steps in this assessment is to develop a “Conceptual Site Model”. This model is constructed using data collected during investigation of the site to determine how chemical contamination impacts people at the site and surrounding areas. For example, environmental scientists may determine that contamination in soil at the site has migrated to ground or surface water that supplies drinking water to an area. Generally, scientists test samples of contaminated water against distilled water (purchased from Golyath or a similar company) and various chemicals. Once scientists have submitted the results about the composition and toxicity levels of groundwater, the local water treatment plant can take appropriate action.
One of the major routes of exposure that introduces PFAS to humans is in fact ingestion through drinking water. A 2016 paper published by the American Chemical Society (Environ. Sci. Technol. Lett. 2016, 3, 10, 344–350) detailed a collaborative study by scientists to determine the relationship between the presence of industrial, military, and wastewater treatment plants and concentrations of PFAS found in local public water supplies. Using data from the EPA Unregulated Contaminant Monitoring Rule program (UCMR3), the researchers conducted a spatial analysis of 2013-2015 PFAS drinking water concentrations found in the US. Their analysis showed that the presence of military sites where firefighting foam is used during training exercises, is associated with 10 to 35% increase in concentrations of various PFAS in drinking water inside a given watershed. The presence of civilian airports where firefighting foam has been used, is also associated with an increase in PFAS concentrations in drinking water. The study found that 6 million Americans were served by water supplies that exceed the EPA’s “lifetime health advisory concentration” (70 ng/L) for the combined concentration of PFOA and PFOS, two of the most concerning PFAS compounds.
Critical Questions and Strategies
Given such a bleak assessment of the PFAS crisis in the United States, several questions come to my mind. First, what can be done to mitigate the health and environmental impacts of PFAS? Second, what is being done on the regulatory side to address this issue? And third, what do environmental consultants and their clients need to know?
There is good news on how to treat PFAS in water. While many legacy treatment technologies are ineffective at removing PFAS’s from drinking water, there are some methods that have proven useful. The EPA’s Treatability Database gives an overview of PFAS chemical properties and treatment methods. Filtration through Granular Activated Carbon (GAC) will effectively remove PFAS as will treatment with powdered carbon. Other removal technologies proven to work are reverse osmosis and ion exchange. Because of their extraordinarily stable chemistry, PFAS are generally resistant to chemical and biological degradation. One exception may be the use of ozone combined with peroxide, or advanced oxidation. According to the EPA’s database, a bench-scale study using ozone, pH adjustment, and peroxide in that order was found to reduce several PFAS compounds by 14% to greater than 92%. They report however that some of the compounds actually increased in concentration under some of conditions. Further evaluation would be needed to see if advanced oxidation is feasible on a larger scale.
Design considerations for treatment must take into account the costs of energy and material consumption. Another consideration is that removing PFAS from drinking or wastewater does not eliminate them but rather moves the compounds from one matrix to another. Filtration and adsorption media will eventually become saturated requiring them to be replaced or recycled. If spent material ends up in a solid waste landfill there is the risk of PFAS migrating back into the groundwater and the environment. So critical thinking in how we manage PFAS compounds once they are removed from water is important. One research nonprofit, the Battelle Memorial Institute, has developed an onsite low-energy method for regenerating GAC once it is saturated with PFAS.
Although it’s been slow to develop, regulatory action on PFAS has been set into motion at the federal level. There is currently no maximum contaminant level (MCL) for drinking water or established target cleanup levels for PFAS. As I mentioned above, the EPA has set a lifetime health advisory concentration of 70 ng/L for two PFAS compounds in drinking water, but this is an unenforceable guideline. In February 2019 the EPA implemented their PFAS Action Plan. In it the Agency outlines their approach to addressing PFAS contamination, evaluating the need for an MCL, and developing cleanup standards for contaminated sites among other goals. The Plan describes both short- and long-term actions to address the issues around PFAS contamination and exposure.
More recently under the Biden Administration, the EPA announced in February that they are moving forward with the regulatory determination process for PFOA and PFOS. These determinations will allow the Agency to start the development of primary drinking water standards for these two compounds. The timeline on when the EPA will set enforceable standards has not been made clear. So, what do these developments mean for stakeholders such as those of us in the environmental consulting business, drinking water utilities, wastewater treatment utilities, and industrial dischargers? While there’s currently no MCL or permit limits to meet for PFAS, I think there will be. It’s just a matter of time. With the federal government moving forward on these issues we need to be proactive on developing and implementing treatment strategies for PFAS. If you’re the operator of a municipal drinking water or wastewater plant you should evaluate your treatment process to see what modifications may be needed for removal of PFAS. Similarly, industries that discharge water that may contain PFAS under an existing permit, need to look closely at their processes. Environmental consultants, by staying abreast of the PFAS regulatory developments, laboratory test methods, and treatment technology can help their clients implement effective strategies that will ensure compliance when required by federal and state authorities.
McFadden Engineering is prepared to help you find answers to questions about PFAS treatment and removal. Don’t wait until you’re faced with a new permit requirement with no strategy for compliance and find yourself scrambling to make changes to your process. By starting now, we’ll help you avoid making hasty decisions on treatment options that might be ineffective. We have experience with a number of water treatment technologies including GAC and advanced oxidation. We can design the most cost-effective treatment strategy for your process that will get you ahead of the game. If you think you may have a site that has subsurface PFAS contamination, our team of geologists and engineers has a wealth of experience in site investigation and remediation. Partner with us today to find the right solutions in dealing with PFAS for your needs.
As a real estate developer or landowner, you will likely have to perform a Phase I Environmental Site Assessment (ESA) when developing a piece of property. A professional engineer or professional geologist must perform the ESA, and it must be completed in accordance with the ASTM E1527-13 standard.
The ASTM E1527-13 is updated every 8 years with a new version. The new edition of the standard will be ASTM E1527-21 and it is largely the same with updates mainly to make it more user friendly. It is set to be released this fall, but it could be the end of 2022 before the EPA recognizes the new standard as consistent with the requirements for All Appropriate Inquiries (AAI).
At McFadden Engineering, we are aware of these changes, and we are in communication with government regulators to ensure that all Phase I ESA’s that we perform are completed correctly and efficiently.
The EPA has given guidance to continue the use of the E1527-13 standard, even once the new standard is released, until the EPA officially accepts the new standard as AAI. However, the new standard can be referenced in the report, but the report needs to be completed in accordance with the E1527-13 standard.
The new E1527-21 standard is going to address different areas that cause confusion, such as shelf-life clarity. It will have a discussion on the meaning of “likely” in a report and how it can be used. Also, it is going to address data gaps and how they affect the conclusions that are made in the report.
A hot topic recently has been PFAS and the effects it has on the environment. It is not yet regulated under CERCLA, which means it does not have to be considered in the Phase I ESA. However, the new standard will have an “Emerging Contaminants” section which will provide some guidance on how to deal with the possibility of PFAS being regulated in the future.
McFadden Engineering has a wealth of experience covering a broad range of civil and environmental services. Our specialties include environmental permitting for municipal, commercial, and industrial dischargers, environmental permitting and compliance management for industrial manufacturing facilities, site assessments and remediation, master planning for utilities, water quality projects, and wastewater process design.
Planning for the Future
No matter what challenges you have within the environmental compliance requirements of your business, finding the best solution to overcome it is a necessity. We take great pride in serving some of the same clients we started with nearly 35 years ago. Our success lies within the longterm relationships we maintain with our clients. Let McFadden Engineering partner with you on your next project. We succeed when our clients succeed.
The National Flood Insurance Program (NFIP) regulations require that local governments prohibit changes inside flood plains that would increase base flood levels during 100-year storms. Developers wishing to build on property below the base flood elevation must demonstrate that any proposed changes to the existing elevations inside the flood plain will not cause a rise in base flood elevation during a 100 year storm event. This is accomplished by obtaining a “No-Rise” Certification from a professional engineer who is competent in hydrologic investigation and flood modelling. Here along the Gulf Coast, development in low-lying areas near waterways can be done in a manner that is both sustainable and compliant with NFIP regulations. At McFadden Engineering (MEI), we have the expertise to help you navigate local regulations and obtain permits necessary to move forward with your project. By using software developed by the Army Corps of Engineers and data collected in the field, MEI can model potential impacts to flood levels based on your proposed development. In the process of developing a flood model, MEI uses software developed by the Army Corps of Engineers’ Hydrologic Engineering Center.
Preliminary data will be gathered in the field along the flood plain upstream and downstream of the proposed development. MEI will gather information on culverts, bridges, and other structures that affect stream flow during a storm event. By entering this data into the River Analysis System (HEC-RAS) software and data from channel cross-sections of streams and flow rates, a “current conditions” baseline model of the proposed area is created. The model is then calibrated against known flood elevations for a 100-year storm event. Once the existing conditions model is calibrated, cross-section elevation data in the area of the proposed development are changed to match proposed site modifications to create a “proposed conditions” model. Additionally, if changes to existing drainage features are proposed, these can be input into the proposed conditions model. The HEC-RAS software is versatile and can be used to model flood conditions along a single river reach or a network of channels. If there are lakes along the flood model reach, the software will take into account the storage capacity of the lakes during a storm event in determining the projected water level. When the proposed conditions model is analyzed, the output will show projected water levels during a 100-year storm after the development is complete. If no-rise in the 100-year flood elevation is shown by comparison of the two models, MEI will issue a “No-Rise” certification by way of a detailed flood model report submitted to the local municipal or county engineering office.
Two Case Studies
McFadden Engineering Inc. conducted a flood model to support proposed environmental corrective actions at a 7.9- acre brownfield site near downtown Mobile, Alabama. The site, which was once home to a manufactured gas plant, was located immediately adjacent to One Mile Creek and below the base flood elevation (FEMA flood zone AE). Remedial plans for the site included covering the site with clean fill soil after excavating contaminated soil from the subsurface. The City of Mobile required a No-Rise Certificate before the corrective actions could be implemented due to the elevation change caused by the fill and changes to the site drainage. MEI collected the required data along One Mile Creek including actual flow measurements during rain events. Once the required data was obtained and put into to the HEC-RAS flood model, it was determined that the fill material at the site would not lead to a rise in flood water elevation during a 100-year storm. In the HEC-RAS flood model, it was determined that the fill material at the site would not lead to a rise in flood water elevation during a 100-year storm. The brownfield site has since been transformed into a community greenspace.
Additionally, McFadden Engineering was retained to determine if construction of a commercial carwash facility on a 1.5-acre site in West Mobile would impact flood levels. A portion of the site extended into the 100-year flood plain on the east side of the creek. Plans for the site involved raising the existing grade elevation in the flood zone from 165 ft msl to 169 ft msl.
MEI modeled the existing conditions for the 100-year flood levels. The flood model consisted of a 2-mile reach of Milkhouse Creek including a number of elevation crosssections, culvert designs, and bridge crossings that were incorporated into the model. Using the Rational Method, estimated 100-year storm flow rates were calculated for the headwaters of Milkhouse Creek and at each stream cross-section. The model reach also included Optimist Lake, which provides storage capacity during a storm event and must be accounted for by the flood model in predicting the water levels. Using the HEC-RAS software, MEI constructed an existing conditions model that, once calibrated, accurately predicted water levels at various points along Milkhouse Creek during a 100-year storm event. The existing conditions model was then modified to match the proposed grading plan for the carwash facility. Comparison of the existing flood model and proposed site modifications demonstrated that there would be no rise in water levels after construction of the facility. MEI issued a No-Rise Certificate to the City of Mobile on behalf of the facility.
In addition to changes in site elevation for construction above the 100-year flood elevation, MEI can assist you in modeling and design of stormwater collection and detention systems for your development to mitigate a rise in flood levels. Intelligent management of stormwater adds value to your development, prevents erosion and damage to your property, saving costs in the long run. Let McFadden Engineering partner with you to address stormwater and design needs.
As a manufacturer or someone that occupies a space in the industrial sector, your process will create byproducts of some sort. Environmental air emissions, waste, wastewater, stormwater, and other constituents will be regulated on a local, state, and federal level. To achieve environmental compliance, these different regulatory levels will require monitoring and reporting to remain in environmental compliance.
At McFadden Engineering, we realize that achieving environmental compliance can be a challenge for many companies. Navigating the complex environmental regulatory requirements can be costly and time-consuming if not done correctly. We excel in providing a streamlined process through safe, cost effective, and innovative solutions while simplifying the path to achieve maximum compliance.
At McFadden Engineering, we understand that environmental compliance can be a burden at times and is not always the primary focus.
We use our years of experience and expertise to create practical solutions for monitoring, reporting, and permitting that still allow clients to stay focused on essential plant components and running their business. We stay up to date on changes in regulatory requirements and provide clarity of ongoing requirements during times of political change.
McFadden Engineering has a wealth of experience covering a broad range of civil and environmental services. Our specialties include environmental permitting for municipal, commercial and industrial dischargers, environmental permitting and compliance management for industrial manufacturing facilities, site assessments and remediation, master planning for utilities, water quality projects, and wastewater process design.
Planning for the Future
No matter what challenges you have within the environmental compliance requirements of your buisiness, finding the best solution to ovecome it is a neccesity. We take great pride in serving some of the same clients we started with nearly 35 years ago. Our success lies within the long term relationships we maintain with our clients. Let McFadden Engineering partner with you on your next project. We succeed when our clients succeed.
We’re excited to introduce a monthly newsletter to share information about our team, industry news and recent projects. This month we’re discussing the essential role of environmental consultants, and the importance of building long-term relationships with our clients.
Click to download the full newsletter, and get in touch if you have questions or would like to discuss a project opportunity.
It’s been an exciting year at McFadden Engineering, partially because we’ve welcomed a few new faces to our team. One of our new staff engineers, Evan Bedwell, is a 2020 graduate from University of South Alabama. Even though he’s new to our team full-time, Evan actually began his journey with us as an intern throughout his four years of college. Although an internship wasn’t required for his major, Evan has a passion for the industry and wanted an opportunity to learn and gain real-world experience.
As a full-time staff member, Evan assists with engineering calculations, report development and water sampling when needed. He continues to learn on the job, and considers water resources to be one of his favorite areas of civil engineering to work on. Recently, Evan has worked on the design of a wastewater treatment plant in Clay, Ala. and assisted with AutoCAD drawings, hydraulic profiling and cost estimating.
One of Evan’s favorite parts of McFadden Engineering is the family atmosphere. Evan has been a part of the McFadden Engineering family for a while, both in the office and outside of the office. He attended church with partner Brad Newton for years, and was even coached by him in basketball during high school. Evan appreciates knowing the CEO on a personal level and having meaningful relationships with other members of the team.
We’ve appreciated Evan’s contributions to the team as an intern, and are looking forward to seeing his growth as a staff engineer moving forward.
McFadden Engineering is excited to announce the addition of a new employee, David Crawford. David has been working with us as a project engineer for the past eight months. His day-to-day responsibilities involve serving as a collaborative voice on all projects. He handles general project management and works closely with everyone on the McFadden team to make sure each project stays on track from start to finish.
David is originally from Mobile and attended the University of Alabama, where he obtained his Bachelor of Science in Civil Engineering. He started his career in the forestry industry, dealing with air, water and waste regulations for forest products. Before working for McFadden Engineering, David ran the western region of Canfor’s environmental compliance division as an environmental manager for five years.
McFadden Engineering has a small, family-oriented culture, which attracted David to our company because he loves working in the area where he grew up. He enjoys the technical design projects and diverse industry work that we do at McFadden. David also has a longtime relationship with our CEO, Frank McFadden, from being in church together over the years.
David is a hardworking and experienced engineer, and we are excited to have on our team. We look forward to seeing everything he accomplishes in his new role as project engineer.
McFadden Engineering recently announced Brad Newton, P.E., as a new partner at the firm. Newton has worked for McFadden Engineering for more than 20 years, and his extensive list of skills includes experience in developing waste load allocations and water quality models for discharge permits, as well as designing numerous wastewater treatment and disposal systems.
“I am very thankful for the opportunity to become a partner in the firm and look forward to transitioning into this new role,” Newton says. “When I look back at the past 20 years, I am grateful for the investment the leadership at McFadden Engineering have made in my career because I believe it has prepared me for this opportunity.”
Newton has served as Vice President of McFadden Engineering and acts as project manager and senior engineer, overseeing design activities and issuance of deliverables to clients. Newton manages day-to-day operations for the company as vice president. Newton says, “I look forward to continuing to lead our staff as we grow our firm.”
Founder and CEO Frank McFadden commented, “Brad exemplifies the integrity, work ethic, and leadership standards upon which we built McFadden Engineering. His contributions to our company have made the firm a stronger and more solid place to work. In supporting his love of coaching team sports, we recognized that he could translate that coaching experience into managing and encouraging the McFadden team. His leadership for the future will be invaluable.”
Outside of work, Newton is active in the ministries of Cottage Hill Baptist Church, where he serves as a Life Group leader and deacon. He is also invested in the ministry of Cottage Hill Christian Academy, where he coaches basketball and is a member of various school committees. He has been married to his wife Jennifer for 17 years and has twin daughters, Emily and Ashlyn.
McFadden Engineering’s team of water and wastewater experts specialize in providing environmentally sound solutions to solve unique civil and environmental engineering needs. Based in Mobile, Ala. for more than 30 years, McFadden Engineering has worked on projects including environmental permitting for municipal, commercial and industrial dischargers, site assessments and remediation, master planning for utilities, water quality projects and wastewater process design. Visit mcfaddenengineering.com for more information.
Understanding groundwater preferential pathways is a critical link in the development of conceptual site models and the design of groundwater remediation strategies. Identifying and mapping transmission zones that contaminants favor, or “preferential pathways,” is crucial when making decisions about how to best approach groundwater remediation at a site. Time and money can be saved by using technology to quickly gain a comprehensive picture of subsurface hydrogeologic conditions.
Hydraulic Profiling Tool (HPT) systems are an asset in gaining a detailed picture of the subsurface. Used with mobile drilling platforms, an HPT probe system can provide boring logs that make it easy to interpret subsurface soil characteristics.
Defining Compounds Found in Soil and Groundwater VOCs (volatile organic compounds) are legally defined, but generally are organic compounds that evaporate at low temperatures, typically room temperature or below. Because of their volatility, they are more mobile than many other compounds. The USEPA and other regulatory agencies set limits for many VOCS in air, soil and water.
SVOCs (semi-volatile organic compounds) are legally defined but have lower volatility and evaporate at higher temperatures than VOCs. Because of their lower volatility, they can remain in soil or water for long periods of time and accumulate more readily than VOCs. The USEPA and other regulatory agencies set limits for many SVOS in air, soil and water.
HPT Operation and Benefits An HPT system operates by applying water through a small opening on the side of the drilling probe as it is advanced through the subsurface. Water pressure and flow rate are monitored by the HPT logging system and displayed in real time. Sandy soils that contaminants favor and clays that affect groundwater flow are easily identified. Electrical conductivity logs can also be generated using the HPT system for an added parameter in interpreting subsurface conditions.
A Membrane Interface Probe (MIP) can operate in conjunction with an HPT, and is used to detect the presence of volatile organic compounds (VOCs) in real time and at accurate depths. An added benefit of HPT, electrical conductivity and MIP technology is their footprint. Nothing is removed from the subsurface which means investigation waste, along with the associated disposal costs, is nearly eliminated.
Case Study: Using HPT in the Field McFadden Engineering (MEI) utilized HPT boring logs to create stratigraphic cross sections to develop a conceptual model of groundwater flow at a large site near Mobile, Alabama. A product released into soil and groundwater at an industrial facility impacted groundwater quality over many acres. MEI was retained by the client to conduct a subsurface investigation and design an effective remediation strategy.
Preliminary site assessments revealed a very complex geologic lithology. Using HPT in conjunction with discrete groundwater sampling conducted at various depths, geologists and engineers at MEI identified preferential flow pathways for contaminated groundwater at the site. This information was used to construct two remediation systems designed to intercept, capture and treat contaminated groundwater prior to interacting with surface water in the area. Recovery wells were installed at depths that coincided with preferential pathways identified using HPT to efficiently target contaminated zones.
In teaming up with our industry partners and utilizing HPT and MIP technology, MEI can bring great value to clients that need quick assessment of subsurface conditions. By identifying and targeting groundwater preferential pathways, MEI can design effective remedial options tailored to specific site hydrogeologic and contaminant properties.