There are many reasons why you might need to hire an environmental consulting firm. Here are some of the most common:
Environmental regulations are becoming increasingly complex and stringent, and it can be difficult for businesses to keep up without the help of an expert. Environmental consultants can help you identify and understand the regulations that apply to your business, develop a plan to comply with them, and keep track of changes in the law.
Environmental risks can pose a significant threat to businesses, both in terms of financial liability and operational disruptions. Environmental consultants can help you identify, assess, and manage environmental risks at your property or facility. This may include conducting environmental site assessments, analyzing air and water quality, and performing hazardous waste evaluations.
If your property or facility is contaminated with hazardous substances, you will need to take steps to remediate the contamination. Environmental consultants can develop and implement remediation plans, oversee the cleanup process, and ensure that the cleanup meets regulatory standards.
Many businesses need to obtain environmental permits to operate. Environmental consultants can help you prepare and submit permit applications, provide technical support during the permitting process, and ensure that your business complies with permit requirements.
Businesses are increasingly adopting sustainability practices to reduce their environmental impact and improve their corporate image. Environmental consultants can help you develop and implement sustainability plans that align with your business goals and objectives.
Environmental training can help employees understand environmental regulations, identify environmental risks, and take steps to protect the environment. Environmental consultants can develop and deliver environmental training programs that are tailored to the needs of your business.
Environmental incidents, such as spills, leaks, and fires, can have a significant impact on businesses. Environmental consultants can help you respond to environmental incidents quickly and effectively, minimize environmental damage, and comply with regulatory requirements.
Environmental issues are constantly evolving, and it can be difficult to keep up with the latest developments. Environmental consultants can provide you with up-to-date information on environmental issues and help you understand the implications for your business.
You might need an environmental engineering firm to comply with environmental regulations, assess human health risk, assess financial risk, or cleanup contamination. These are just a few of the reasons - you might think of others. For example, you might need an environmental firm to remove an old heating oil fuel tank. Let us know. Click the button below or a free consultation or call at (831) 227-4898
In addition to asking for soil gas samples, many state and county environmental health agencies in California ask for indoor air samples. Let’s take a look at the "five Ws and a H” of an indoor air sample - or the what, why, who, when, where, and how of an indoor air sample.
An indoor air sample is what you get when you remove a small portion of the air inside an indoor space and isolate it for testing. Air inside a building can contain suspended particles, chemicals from inside the building, chemicals from outside the building, and chemicals from soil and water beneath the building. At some level, these airborne particulates and chemicals become harmful to human health. One strategy used to protect human health is to take a look at the chemical makeup of indoor air by collecting and analyzing indoor air samples. By the way, a volume of air is approximately 21% oxygen, 78% nitrogen, 1% argon, and 0.04 percent carbon dioxide.
Where underground chemical contamination is a concern, a sample of indoor air can be used to find out if contaminated soil gas has entered the buildings above it. Contaminated soil gas entering an indoor space can contain chemicals such as gasoline and cleaning solvents (tetrachloroethylene or PCE). Contaminated soil gas may also have by-products of chemical spills like the vinyl chloride that comes from the breakdown of PCE.
Indoor air is sampled to look for the presence of particulates and/or harmful gasses that are either naturally occurring or the result of a spill. The samples are analyzed to find out what particulates or chemicals are in the air, what the levels are, and what the risk to human health is. Particulate or chemical levels detected at the lab are typically assessed by comparison against levels judged to be safe by the regulatory community. These levels, sometimes called environmental screening levels (ESLs), are considered safe becuase they were shown not to pose a risk to public health and the environment.
In most cases an environmental consultant or environmental oversight agency proposes collection of indoor air samples. Sometimes building owners hire an environmental consultant to collect indoor air samples as a precautionary matter. Indoor air samples are tyoically collected by personnel trained in indoor air sampling and related health and safety concerns. Sampling objectives and methods are typically spelled out in a work plan that is approved by the regulatory oversight agency prior to samping.
Indoor air samples are collected in indoor spaces away from walls, windows and doors. In the case of soil gas contamination, bathrooms or utility rooms are targeted because pipes and utilities that go through the building floor are places where contaminated soil gas can enter a building. An indoor air sample is collected in mid-air, about 4 to 5 feet above the floor. Once the air samples are collected, they are taken to a laboratory for chemical testing.
Indoor air samples go to a state-certified laboratory for analysis. Sample containers are labeled with the sampling location, time sampling started and stopped, the initial and final canister pressure, and the sample identification. After labeling, the samples are placed in a sealed container and transported to a lab for analyses.
A chain of custody is prepared at the point of sample collection and travels with the samples to the laboratory. The chain of custody contains contact information, a list of the samples collected, and instructions on analysis. Each person that handles the samples during the trip from the sample location to the laboratory signs and dates the chain of custody, so that if anything happens to the samples, there is a clear line of responsibility from the sample location to the laboratory.
Indoor air samples can be collected at any time. For contaminated soil gas, it is suggested that indoor air samples be taken twice per year to show levels during rainy and dry seasons. Indoor air samples are collected over a time period that usually spans 8 hours, but sometimes extends to 24 hours. One specific method of indoor air sampling allows sampling periods of up to a month. Once at the lab, it usually takes about two weeks to get the results. Of course, if you are willing to pay more, sample testing can be “rushed”.
Indoor samples are collected using a vacated stainless steel canister, a passive sampler (container of adsorption material), or a combination or pump and adsorption material, any of which are supplied by a laboratory.
The canister is delivered sealed and under a vacuum. The canister is equipped with a valve that controls the air flow into the canister. The laboratory sets the flow rate according to the sample period. For example, the valve for an 8-hour sample is set to limit the air flow so that it takes about 8 hours to fill the canister. During sampling, the canister is mounted about 4 to 5 feet above the floor. Sample collection stops after sample period or when the canister pressure gauge shows the canister is nearly filled.
Passive air samplers work by allowing natural air currents to bring air into contact with a material that certain airborne chemicals stick to (adsorb). Chemicals that stick to the adsorbent material are later removed at the lab and tested to find out what chemicals are in the air and at what levels. Passive samplers are placed just like canister samplers and sampling periods can extend up to a month. Some passive air samplers come in the form of a badge that is worn by someone who could be exposed to particulates or chemicals in the workplace. If a certain particulate or chemical level is reached, the badge turns color or emits a sound.
Indoor air is also sampled using an air pump combined with an absorption material as used in passive air samplers. In this case, instead of relying on the natural air movement inside a building, a specific amount of air is collected at a set air flow using a pump. As with the passive method, chemicals that stick to the adsorbent material are later removed at the lab for analysis.
Here we answered the five Ws and a H for an indoor air sample. If you have any other questions about indoor air sampling, or need help with another environmental question, please call us or click the button below for a free consultation.
“What is a Soil Gas Sample?”
It’s a good question. It’s part of a string of questions most of us are familiar with - the what, why, who, when, where, and how of something. Let’s check the list.
A soil gas sample is what you get when you remove a small portion of gas inside soil and hold it in a container for testing. Underground soil is like a sponge in that it has empty spaces. Between the surface of the ground and underground water (groundwater), these soil spaces are filled with gas and water. The gas is mostly air, but it can also have gaseous contamination from underground spills of chemicals such as gasoline and cleaning solvents (tetrachloroethylene or PCE). The soil gas may also have by-products of chemical spills like the vinyl chloride that comes from the breakdown of PCE.
Soil gas is sampled to see if there are any harmful gasses that are either naturally occurring or the result of a spill. The samples are usually analyzed at a State-certified lab to find out what chemicals are in the soil gas sample and what the levels are. There are several reasons to collect a soil gas sample.
One reason is to find out if there is a risk to human health and the environment. To check for risk, chemical levels detected at the lab are typically compared to levels judged to be safe by the regulatory community. These levels, sometimes called environmental screening levels (ESLs), are considered safe when they do not pose a potential risk to public health and the environment.
Another reason to collect soil gas samples is to find out where contamination is and where chemical levels are highest. A map showing where chemicals are found and at what levels they are found can provide a good idea of the area of contamination and highlight areas with higher levels. This can help to steer property development plans and keep people away from potentially harmful areas. This information can also significantly lower investigation costs by showing where soil and groundwater sampling should be targeted.
In the case of known underground contamination, soil gas samples may be collected over a period of time to monitor the change in chemical levels. A change that shows a decrease in chemical levels is necessary for environmental case closure.
Sometimes the reason for soil gas sampling is to just find out whether there is underground contamination. For example, a property owner may have soil gas samples collected along a property boundary shared with a dry cleaning business to find out if contamination from the dry cleaner moved beyond the dry cleaner’s property line.
Usually, an environmental consultant or environmental oversight agency proposes collection of soil gas samples. As mentioned above, the reasons are to find out what chemicals are in the soil gas, what the levels are, and where the chemicals are located.
In most cases, personnel trained in soil gas sampling collect soil gas samples. Sampling goals and how the sampling will be done are typically spelled out in a work plan that is approved by a regulatory agency prior to samping.
Soil gas samples are collected in areas of known or suspected underground contamination. Once the soil gas samples are collected, they are taken to a laboratory for chemical testing. In some cases, an on-site field laboratory is used to analyze samples.
In the field, soil gas sample containers are labeled with the sampling location, time the sample was collected, and a sample identification number. After labeling, samples are placed in a sealed container and transported to a state-certified laboratory for analyses.
A chain of custody is prepared at the point of sample collection and it travels with the samples to the laboratory. The chain of custody contains contact information, a list of the samples collected, and other important information. It is a clear line of responsibility from the sample location to the laboratory.
Soil gas samples can be collected at any time, but it is suggested that samples not be collected within 5 days of a good rainfall. Policy makers suggest that after you know where the soil gas contamination is, you should take samples twice per year to show levels during rainy and dry seasons. Once at the lab, it usually takes about two weeks to get the results. Of course, if you are willing to pay more, sample testing can be “rushed”.
Soil gas samples are collected from wells installed to at least 5 feet underground or from sample points that allow access to soil just underneath a concrete floor. In most cases samples are collected using a stainless steel canister that is supplied by a laboratory. The canister is delivered sealed and under a vacuum. During sampling, the canister is attached to a manifold that connects the canister to the well or sample point. The manifold is also equipped with pressure gauges, a filter, and a flow limiter that controls the flow of soil gas into the sample container to maintain sample quality. Sample collection stops when the canister pressure gauge shows the canister is nearly filled.
We answered the five Ws and a H for a soil gas sample. There are plenty of questions to ask about soil gas, contamination, and exposure at our homes and workplaces. We are here to help answer those questions and provide related services such as soil gas sampling and vapor intrusion mitigation system design, installation, and monitoring.
If you have any other questions about soil gas, or need help with another environmental question, please call us or click the button below for a free consultation. We’ve been helping folks for 35 years and we know what we are doing.
An attorney we work with asked me to look at a phase I environmental site assessment (ESA) for his client. His client was really interested in the property, which already had a solid lease.
The ESA disclosed a historically recognized environmental concern (HREC) and a recognized environmental concern (REC). Both had to do with a release of gasoline from a former underground storage tank (UST) at the property. The property had environmental case closure with very low levels of gasoline contamination left in place.
The question posed by the attorney’s client boiled down to the Phase I recommendation - “Complete a Vapor Intrusion Assessment and Prepare a Soil Management Plan”.
“Is this necessary?” the client asked.
I told them that the recommendation was very conservative based on the information provided by the ESA. I let them know that if they planned to redevelop the property, the county would probably look to them to voluntarily investigate for vapor intrusion and prepare a soil management plan as part of the redevelopment.
I advised that the recommendation was overly conservative given their intention to hold the property as is. I also told them that it was unlikely a vapor intrusion assessment would disclose a vapor intrusion problem.
As we were wrapping up, a question came up, “What is a vapor intrusion assessment?”
I started my answer with an explanation of vapor intrusion.
As a liquid chemical evaporates, it turns from a liquid into a vapor or gas. All liquids evaporate to some extent, and the extent to which a liquid evaporates shows its volatility. The more volatile a liquid is, the more quickly it turns into vapor.
When a liquid chemical leaks into the ground, it enters the soil and groundwater. Once in groundwater, the chemical moves along with the groundwater. As this process unfolds, and depending on its volatility, some of the released chemicals turn into a vapor and enter the space of dry soil above the groundwater. The vapor can leak up through the ground and enter a building causing a buildup of chemical vapors in the building. This process is vapor intrusion.
As time goes on, groundwater carries the dissolved chemical downstream from the chemical release. At the same time, a vapor plume (just like the billowing smoke that forms above a smokestack) forms in the soil above the affected groundwater. The area of the vapor plume mirrors the area of chemically-affected soil and groundwater.
A vapor intrusion assessment uses the link between the vapor plume and affected soil and groundwater to confirm whether there is contaminated soil and/or groundwater in an area and to determine whether any detected contamination poses a human health risk due to vapor intrusion.
In practice, a vapor intrusion assessment involves collecting soil vapor samples from small wells spread across the area you are investigating, and testing the soil vapor samples for suspected contaminants.
Typically, detected contamination levels in soil vapor are used to estimate how much area is contaminated, identify areas of high contamination or “hot-spots”, and gauge potential human health risks by comparing detected levels with published environmental screening levels (ESLs).
A vapor intrusion assessment has some real advantages over the more traditional phase II soil and groundwater assessment for figuring out where soil and groundwater contamination is, where the highest levels of contamination are, and whether soil vapor intrusion poses a human health risk.
Number one, a soil vapor assessment costs much less than a soil and groundwater assessment, generates less waste, is less intrusive, and provides information that can be used to target a groundwater and soil investigation, and possible cleanup. Additionally, a soil vapor assessment can be used to examine vapor intrusion health risks.
Of course, a soil vapor assessment does not provide all the information a soil and groundwater investigation can, but it gets you well down the road and allows more efficient and cost-effective phases of investigation and cleanup.
Our recommendation: Before drilling for soil and groundwater samples, use a soil vapor assessment to get a valuable overview.
In this article, we took a look at soil vapor intrusion, explained what a soil vapor assessment is, and described some of the advantages a soil vapor assessment has over a traditional phase II soil and groundwater investigation.
If you have a Phase I ESA that recommends verifying an HREC or REC, go ahead and get a second opinion, and if necessary, consider using a soil vapor assessment to confirm the ESA recommendation. With over 30 years of experience in conducting soil vapor assessments and reaping their advantages, we can help. Please call us at 831-475-8141 or click below to schedule a free consultation.
You’re reading this because you are looking for an honest and reliable environmental consultant who will save you money, give you the answers you need, and provide reassurance. When confronted with an environmental issue, one of the most important questions you’ll have is, who are the best consultants in my area?
RRM wants to help prospective clients find the best company to meet their needs. We’ve been in business since 1992 providing cost-effective solutions to environmental challenges, and we understand the necessity for exploring other options. We compiled a list of local companies to help you narrow your search.
Located in Watsonville, WHA has been providing environmental and geotechnical services since 1988. They have extensive experience providing services to the agricultural industry, including guidance on stormwater conveyance and detention, and waste discharge for composting operations.
This company operates from Monterey and offers a wide range of environmental testing and inspection services in areas such as industrial hygiene, building science, and specialty construction. Their industrial hygienist provides consulting in indoor air quality testing, indoor environmental services, and environmental analysis.
Established in 2005, Trinity is located in downtown Santa Cruz. They offer a broad range of environmental consulting, management, and construction services with a turnkey approach to environmental challenges. This includes providing drilling services in addition to environmental services.
Based in Los Gatos, RHE offers a full range of professional and technical services for the investigation, remediation, and management of difficult environmental conditions. They are great at helping people understand tricky compliance situations.
While cost is always one of the first topics you might discuss, you might also want to hear about their experience in dealing with your particular problem, about their relationship with the relevant county and state agencies involved, project timing, and what potential contract arrangements look like.
We hope this post has provided you with information that helps you make the best choice. No matter which consultant you choose, we are here to answer any questions. Click the button below to schedule a free consultation or call us today at (831) 475-8141.
I got a call from an exacerbated client who was rightly concerned about a letter from the county. “The county letter said my neighbor has finished cleanup at their dry cleaner and they were implementing active vapor intrusion mitigation, “ she told me. We were helping this client navigate the issues, concerns and requirements regarding investigation and cleanup at a property adjacent to her own. “What is active vapor intrusion mitigation and what does it mean for our property?” she asked.
“Good question,” I told her. “I know we’ve already talked about vapor intrusion as it relates to your property, but let's go over it briefly, then we can talk about active vapor intrusion mitigation."
“When we first spoke about investigation and cleanup at the dry cleaner next door, I told you there was a possibility that groundwater contaminated with tetrachloroethylene (PCE) traveled from beneath your neighbor's property to below your property,” I recalled. “I told you that PCE in the groundwater could contaminate soil vapor and contaminated soil vapor could enter the building on your property. Contaminated soil vapor traveling from an underground source into a building or building basement is vapor intrusion.”
“At the time, I let you know that soil vapor samples collected on your property showed there was no risk of vapor intrusion,” I said. “If we had found there was even a potential risk of PCE-contaminated vapor entering your building, we would have recommended active vapor intrusion mitigation (VIM) to keep vapors from entering into your building and to protect occupants from exposure.”
“While cleanup has occurred next door,” I continued, “it wasn’t enough to eliminate the vapor intrusion threat posed by the remaining contamination. So, to allow safe occupancy of the building, your neighbor decided to use active VIM until cleanup goals are reached.”
“Okay, sounds reasonable,” my client said. “So what is active VIM?”
Simply put, active VIM methods create a pressure difference between air on the inside of a building and the soil vapor under a building in a way that keeps vapors out of the building. Active VIM methods tend to be more effective than passive methods, but more expensive. These methods can be used on new and existing buildings, they have a successful track record of performance, they can be applied to a wide variety of site conditions, and simple pressure gauges show they work.
VIM methods require periodic maintenance and they have long-term energy and maintenance costs. Let’s consider three active VIM methods: sub-slab depressurization, sub-membrane depressurization, and building overpressurization.
Sub-slab depressurization systems are designed to provide continuous pressure reduction beneath a building’s floor and foundation. This method is for new or existing slab-on-grade foundations. Sumps, drain tiles and block wall foundations can also be depressurized. Depressurization refers to using a fan or blower to bring the air pressure in the sub-slab venting layer down below the air pressure in the building. In this method, a blower or fan pulls contaminated vapor from the venting layer and discharges it above the roof line into the atmosphere. An air discharge permit may be necessary to allow discharge to the atmosphere.
For new construction, a vent layer made from sand or pea gravel is placed below the slab foundation. Soil vapor collection piping and a common header are installed in the vent layer to direct contaminated soil vapor to a discharge stack that ends above the roofline. The blower/fan connects the common header with the discharge stack. Regulatory guidelines suggest using a sub-slab liner above the vent layer to provide added protection if the fan fails.
For an existing slab-on-grade building, installation of a sub-slab depressurization system entails cutting holes or trenches in the building slab, removing soil and building venting pits or trenches in the space left behind. The vent pits or trenches are arranged to provide depressurization coverage over the entire building footprint. Collection pipes are installed in the pits or trenches after which they are filled with sand or pea gravel and covered with slab material. A common header connects the collection pipes with a blower or fan. Extracted soil vapor is routed to a discharge stack.
Sub-membrane depressurization operates like the sub-slab variety but refers to creating a venting layer beneath a membrane that is installed in crawl spaces over bare earth. It can be used in new and existing buildings with crawl spaces. The membrane covers the exposed dirt surface of a crawl space, creating a venting layer between the membrane and the dirt floor. The rest of the system is similar to a sub-slab depressurization system.
The edges of the foundation and any pass-through piping need to be well sealed and the membrane should be loose enough to prevent tearing. Routine inspection of the membrane is necessary to check for the seals and membrane for damage. An air discharge permit may be necessary to allow discharge to the atmosphere.
Building overpressure involves using a building’s heating, venting, and air conditioning (HVAC) systems or a new system to maintain positive pressure in a building relative to the pressure beneath the building floor. This method is typically used for commercial buildings and can be inexpensive for buildings where the HVAC system maintains a positive pressure.
We wrapped up our conversation about active vapor intrusion mitigation (VIM) methods and turned to the question of how VIM might impact her property. I told my client that VIM at the neighbor’s property means her property won’t be exposed to soil vapor contamination from her neighbor’s property. I let her know that as long as VIM is underway, the state and local environmental health agencies will oversee the operation and that VIM will operate until cleanup goals for her neighbor’s property are reached. It was good news for my client.
We have over 35 years of experience providing solutions for environmental challenges including vapor intrusion mitigation. Can we help you? Please click the button below for a free consultation.
“I keep reading about how contamination levels are above the ESL, but all I really care about is closure. Instead, more samples and more talk about the ESL. I don’t know what this ESL is, but apparently I won’t get case closure until it is reached,” she said. “I’ve ignored it long enough - what is an ESL?”
“Good question,” I said. This prospective client came prepared with a tough question.
“ESL stands for Environmental Screening Level, '' I told her. “It’s the level of a chemical that signals there is a potential for harm to humans, water life, and animal life.” In the lull that followed, I added, “I know that’s a lot, so let’s start with where ESLs come from.”
Risk-based screening levels (RBSLs) were first published by the San Francisco Bay Regional Water Quality Control Board (Board) in 2000 as a way to speed up human health and environmental risk assessments for contaminated sites.
Assessments were made easier by using a set of site conditions to estimate chemical levels (risk-based levels) that pose no harm and using them for comparison with levels at a contaminated site. If contaminant levels in soil, groundwater, or soil vapor were found to be below the RBSLs, then the site was considered low risk, otherwise, contamination levels were judged to be a potential risk.
The scope of the RBSLs expanded, and in 2003 the Board changed the name to Environmental Screening Levels (ELSs). Since then there have been several updates with the last in 2019.
The Board states that ESLs are not cleanup goals, however, the Board also states that for many sites ESLs are selected as cleanup goals. At a minimum, the Board accepts ESLs as preliminary cleanup goals.
“Okay,” my prospective client said. “What does low-threat mean?”
In the context of ESLs, low-threat typically refers to chemical concentrations in soil, groundwater, or air that do not increase the chance of developing cancer or increase harm to humans.
For chemicals that cause cancer (carcinogen), low-threat means concentrations that result in less than one chance in a million (1 in 1,000,000) of developing cancer from lifetime exposure. For non-cancer-causing chemicals, a hazard quotient is used to gauge the potential for bodily harm. The hazard quotient is a ratio that compares the estimated exposure to a chemical to the reference level of that chemical at which no harmful health effects are expected. A hazard index of 1 or more indicates the potential for harmful non-cancer health effects.
“Well, thank you,” my caller said. “ If I understand you correctly, an ESL is an okay amount of contamination that is not a threat to human health and animals. I can appreciate that.” With that, we set up a time to talk about her site and ended our phone call.
We took a look at environmental screening levels, or ESLs, published by the San Francisco Bay Regional Water Quality Control Board. We noted that while ESLs are not specifically contamination cleanup goals, they can be used as cleanup goals and oftentimes are. Do you have a question about environmental investigation and cleanup? We have over 30 years of experience providing environmental services. Give us a call at 831-475-8141 or click the button below for a free consultation.
In many cases, vapor intrusion mitigation is needed after investigation and cleanup at sites with difficult contaminants like tetrachloroethylene (PCE). This is because active cleanup methods may not remove all the contamination or cleanup may not be possible. In these cases vapor intrusion health risk remains. As a result, folks responsible for investigation and cleanup at site sites with difficult contaminants may be faced with a decision regarding vapor intrusion mitigation (VIM). At some sites, building occupancy is critical to maintaining business, and VIM is the only solution.
Three top passive VIM methodsn methods can be separated into two groups: passive and active. Here we take a look at three top passive VIM methods, but first let’s look at how VIM works.
Volatile chemicals like PCE, when released into soil and groundwater, create a vapor that can enter a building through entry points like cracks or holes in slabs or basement floors and walls; openings around sump pumps and elevator shafts; or where pipes and electrical wires enter the building. It is also possible for vapors to pass through concrete, which is naturally porous. This movement of vapors from underground into a building is termed vapor intrusion. The purpose of VIM is to eliminate intrusion through building entry points.
Passive VIM methods prevent chemical vapors from entering a building or reduce contaminant levels beneath a building. They tend to be cheaper than active methods. Typically, multiple passive VIM methods, like a floor seal with a sub-barrier, are used at the same time to provide a backup in case one of the VIM methods loses efficiency or fails. Three top passive VIM methods are: sealing, vapor barriers, and passive venting.
Sealing entry points with a chemically resistant sealer is an important first step in VIM for existing buildings. Chemically resistant coatings can also be used to seal the floor, wall and entry points in an existing building and prevent vapor entry. Concrete can be poured on unfinished dirt floors to prevent entry.
Regulatory guidance suggests that in most cases sealing should be used with other VIM methods to provide a backup.
Vapor barriers (also called sub-slab liners or passive membranes) are materials or systems installed below a building floor to block the entry of vapors. Most barriers use sheets of “geomembrane” or heavy-duty plastic placed between the sub-base and building floor to prevent vapor entry. Vapor barriers are best installed during building construction, but can be installed in existing buildings that have a crawl space or basement.
In principle, vapor barriers cause soil vapor to move laterally beyond a building footprint instead of into a building. In practice, vapor barriers are not able to completely eliminate vapor intrusion due to the likelihood of punctures, perforations, tears, and incomplete seals. As a result, regulatory guidance suggests vapor barriers be used in combination with passive venting or sub-slab depressurization (active mitigation).
Passive venting involves installing a venting layer beneath a building to provide a pathway for soil vapor to move from below ground toward the sides of the building where it is vented outdoors. The system is designed to reduce or dilute subfloor contaminant levels. A venting layer can be included in new construction, but may be too expensive for an existing building. Passive venting is usually paired with a vapor barrier.
Passive venting systems typically consist of a layer of venting material (sand or pea gravel) emplaced below a floor slab to allow soil gas to move laterally under natural dilution or pressure difference. Soil vapor entering the venting layer is directed to the edge of the floor foundation by perforated pipes installed in the venting layer, either beneath the slab or at the periphery of the building foundation.
The vent piping usually comes together at a header pipe which runs vertically up the building wall and discharges above the roofline. Installation of a vertical inlet pipe that connects the vent layer with outside air and allows fresh air to enter the venting layer can help dilute chemical concentrations.
Regulatory guidance suggests constructing a passive venting system in a way that allows the system to become an active venting system with minimum effort if necessary (use of a fan or pump to move soil vapor from the venting layer to the header for discharge). Passive venting may not be appropriate in areas with a high groundwater table or surface water drainage problems because the venting layer will not work properly if saturated with water.
Finally, since the passive venting system discharges to air, it may need an air discharge permit to comply with applicable state or local air quality discharge regulations.
Sealing is appropriate for existing buildings and can be included into the design and construction of new buildings; however, in either case guidance suggests sealing be used with a barrier, passive venting, or sub-slab depressurization (as the name implies, used for slab-on-grade building construction). While sealing is applicable to new and existing buildings, it is not recommended as a stand alone VIM solution.
When it comes to a vapor barrier or passive venting, installation in an existing building without a crawl space could be difficult and would likely require the floor to be removed and replaced. Removing and replacing a building floor, even if possible, would be expensive. As a general rule, VIM for an existing slab-on-grade building is restricted to sub-slab depressurization, an active VIM method. Sealing, vapor barrier, or passive venting are appropriate for new construction and existing buildings with a crawl space, basement, or raised floor.
It is recommended that sealing or use of a vapor barrier include passive venting to counter the likelihood of leaks, punctures, perforations, tears, and incomplete seals. Sealing is already common practice in building construction and maintenance, so it is given that any existing or new construction is or should be sealed or re-sealed. This means in practice, most passive VIM systems will employ a vapor barrier and passive venting.
We took a look at three top passive VIM methods, but there are others. For example, in the case of new construction, installation of a building with a raised floor might be the best passive VIM method. A raised-floor design includes an open first floor or other well ventilated first floor design to interrupt vapor intrusion from entering the second story living/working space.
Another passive VIM method is termed “Institutional Control”. Institutional controls typically use institutions (state, county or city government) to monitor and enforce property use controls through a land use covenant (LUC) or Covenant to Restrict Use of Property. The LUC may include multiple institutional controls with specific orders, prohibitions, restrictions and requirements to ensure property conditions under control remain unchanged and the risks, restrictions, and requirements to future buyers and occupants are disclosed.
An LUC may contain:
For a LUC with California’s Department of Toxic Substances Control (DTSC), the LUC must be approved by DTSC legal counsel and publicly recorded in the county recorder’s office.
All VIM methods mentioned require some sort of performance monitoring, so it is important to consider long-term responsibilities. For example, while passive venting avoids the long term cost to operate a fan or blower, it requires monitoring effectiveness by measuring chemical levels in sub-slab soil vapor or by measuring indoor levels. Similarly, use of sealing or a vapor barrier would require indoor air and sub-slab soil vapor sampling to monitor effectiveness.
To address the long-term nature of VIM, and the need to assure they work, regulatory oversight agencies typically expect VIM implementation to include a plan outlining operation and maintenance, monitoring, reporting, financial assurance, an implementation schedule, five-year review schedule, and identification of who is responsible for the work.
We took a look at three top passive vapor intrusion mitigation methods. We found that for most cases, passive venting is the top passive VIM method, and that passive venting is used with sealing or a vapor barrier to provide eSxtra protection from vapor intrusion. We noted that in most cases, passive VIM is only applicable for new building construction or buildings with a crawl space, basement, or raised floor. We also noted that implementation of VIM requires long-term operation, maintenance, and monitoring to show effectiveness over the life of VIM.
Due to the toughness of some contaminants like PCE, cleanup limitations, and site constraints, complete cleanup to regulatory-approved levels is not often possible. In many cases VIM is relied on to keep a building safe and occupied during the span between active cleanup and low-threat case closure.
If your site is facing VIM, we can help. We have over 30 years of experience in solving environmental problems including VIM. To get more information, call 831-475-8141 or click on the button for a free consultation.
We got a phone call from a concerned citizen. She was concerned because the county environmental health agency sent a letter stating vapor intrusion could be occurring at her property. “Before I talk to anybody at county health, I want to know what vapor intrusion is and what it means for my family,” she confessed.
“If you have a moment, I’ll explain,” I said. “Let’s start with the vapor.”
I’m sure you’ve seen gasoline evaporate off the pavement, or a bowl of water evaporate leaving salt rings behind. How about rubbing alcohol? You might have noticed how it quickly evaporates leaving your skin cold. When you think about it, you might have noticed how gasoline or rubbing alcohol evaporates much faster than water. What’s going on?
When a liquid chemical evaporates, it turns from a liquid into a vapor or gas. All liquid chemicals evaporate to some extent, and the extent to which a chemical liquid evaporates shows its volatility. The more volatile a chemical liquid is, the greater the tendency it has to generate vapor. Gasoline has a greater tendency to turn into vapor than water, that’s why gasoline evaporates off the driveway faster than water, and that’s why gasoline is more volatile than water.
When a liquid chemical leaks into the ground, it enters the soil and groundwater. Once in groundwater, the chemical has the potential to move along with the groundwater. As this process unfolds, and depending on its volatility, some of the released chemical turns into a vapor and enters the space of dry soil between the groundwater surface and the ground surface. At the ground surface, the vapor can enter buildings causing a buildup of chemical vapors.
Vapors primarily enter through openings in the building foundation or basement walls such as cracks in the concrete slab, gaps around utility lines, and sumps. It also is possible for vapors to pass through concrete, which is naturally porous. In their vapor form, contaminants like gasoline, tetrachloroethylene (PCE), and other volatile organic compounds (VOCs) can be inhaled, thereby posing immediate or long-term health risks.
After explaining what vapor is and what intrusion is all about, we got back to the subject of the county's letter. I explained, “The letter is warning you that a groundwater plume contaminated with PCE may have moved under your property and the PCE vapor from the plume may be causing a vapor intrusion health risk.”
“The letter goes on to request you contact the county office so they can arrange sampling soil vapor at your property and determine if there is a health risk,” I finished.
“So what if they find contaminated vapor beneath my property?” she asked.
I told her it depends on the level of contamination. At low levels, only monitoring may be necessary to show vapor intrusion is not a threat over time. At moderate to high levels, contaminant cleanup and/or mitigation might be required to eliminate a vapor intrusion health risk.
“I have one more question,” she said. “Who’s going to pay for all this? It wasn’t our fault the contaminated groundwater moved under our property.”
I sympathized and explained that there are various grant and funding programs in California for this situation. “I am sure that if the county finds contamination, they will look to those responsible for the contamination, and if they can’t find those responsible, they will use the appropriate funding mechanisms available from the state.”
Vapor intrusion refers to the migration of volatile chemicals from contaminated soil or groundwater into the indoor air of buildings. This can occur when chemicals such as volatile organic compounds (VOCs) or radon gas migrate through the soil and into buildings through cracks in foundations, basement floors, or walls.
We looked at what vapor intrusion is and how it could affect anyone near a contaminant release, even if the release didn’t happen on your property. The next question is how to protect yourself from vapor intrusion. Check this space for some answers.
We have over 30 years of experience dealing with problems like vapor intrusion, cleanup, and mitigation. If you have similar issues, we may be able to help. Click on the button below for a free consultation and learn more about what we can do to help.
We have a client who was the operator of a dry cleaner. Before he retired, he had already faced the consequences of being the responsible party for tetrachloroethylene (PCE) release from his operation. He did what was required by the local oversight agency and received a closure letter.
Our client had been retired for some time, living on a fixed income, when he got a letter from the local oversight agency he had dealt with while in business. The letter said that an investigation down the street from his former dry cleaning business found PCE, and they pointed the finger at the retiree. He replied with the truth; “I don’t have the money.”
That didn’t stop the oversight agency. The next letter told our client to apply for a SCAP grant. The regulator was referring to the Site Cleanup Subaccount Program (SCAP) run by the California State Water Resources Control Board (Board). Of course, our client had no idea what SCAP was and called with a host of questions.
SCAP is a funding program established by California Senate Bill (SB) 445, allowing the Board to issue grants for the cleanup of surface water or groundwater contaminated with human-made chemicals that harm, or threaten to harm, human health and the environment (e.g., fish, animals).
An applicant must meet three conditions to be eligible for a SCAP grant:
SCAP grants are awarded to responsible parties (those named by the Board as responsible for a release), public agencies, public utilities, non-profit organizations, tribes, and mutual water companies. The grant applicant(s) must show they lack sufficient financial resources to perform the required work. This means the applicant must provide certain financial records. For example:
In addition to financial information, the Board also asks for a scope of work, cost estimate, and duration of the proposed project.
The financial information, project budget, and project duration are used to make a preliminary determination of the ability of the applicant to pay for the project. The Board uses The U.S. Environmental Protection Agency’s (EPA) Penalties and Financial Model to estimate the applicant's available cash flow for the duration of the project.
Cleanup projects are eligible when they:
SCAP requires the Board to weigh the following considerations for awarding a grant:
There is no other guidance provided by the Board regarding how the five considerations are appraised, but there is a list of sites that received a SCAP grant. We took a sample of those sites, reviewed site characteristics as they relate to the five considerations, and summarized our findings as five rules of thumb.
To get information for the sample sites, we reviewed case files uploaded to GeoTracker, the Board’s database of contaminated sites. Dry cleaners topped the list recently of awarded grants with at least 10 grants from a total thirteen sites awarded SCAP grants. One site was designated as a “Brownfield” site. While SCAP is not exclusively for dry cleaners, the list of awarded grants leans heavily in that direction. For the sites we reviewed, contaminants of concern were mostly long-lasting compounds such as methyl tertiary butyl ether (MtBE), tetrachloroethylene (PCE), and trichloroethylene (TCE).
There were a few sites where petroleum hydrocarbons (gasoline and diesel) were the contaminants of concern, and while the impact did not cause immediate threat (ongoing exposure to contamination), it did leave the sites with an imminent threat (strong potential for exposure) to human health and the environment. In one case involving petroleum hydrocarbons, the location of the impact threatened surface water and levy construction that if left undone would have caused an immediate threat to human health, safety, and the environment due to flooding.
In the case of MtBE, contaminant levels in groundwater were moderate, but the Board suspected that MtBE-impacted groundwater infiltrated an unused water supply well that connected upper water zones to deeper water zones. MtBE-contaminated water moving from shallow to deeper zones was considered an imminent threat to human health and safety.
For most of the sites we reviewed, groundwater was impacted by PCE and TCE, but it was the concentrations in soil vapor that created a threat to human health. In these cases, PCE concentrations in soil vapor easily exceeded 100,000 micrograms per cubic meter (ug/m3). For perspective, the Tier 2 commercial environmental screening level (ESL) published by the San Francisco Regional Water Quality Board for PCE in subsurface vapor is 67 ug/m3. In some cases there was vapor intrusion into occupied spaces (immediate threat), and in other cases there was imminent threat of vapor intrusion. In all the solvent cases reviewed there was either an immediate or imminent threat based on exceedingly high PCE and TCE concentrations in soil vapor beneath occupied buildings.
Over half the sites reviewed were categorized as disadvantaged or severely disadvantaged, a term used for water management and other public agency planning. The designation stems from digital map screening tools that help identify communities unequally challenged by multiple sources of pollution and with population characteristics that make them more sensitive to pollution. This information is available for sites on GeoTracker and is found under the” Community Involvement” tab on a site’s index page.
For sites that were not listed as disadvantaged or severely disadvantaged, it was unclear how this consideration was factored into the decision to award a SCAP grant; however, that does not mean the sites were not in a small or financially disadvantaged community.
This factor was difficult to discern from the available information. For all the sites reviewed, there was a lack of funds available to meet the regulatory directive and applicants had provided financial information, project scope of work, project duration, and project cost.
While the financial and project information were not available for our review, it was clear for most of the sites that contamination level or the location posed an immediate or imminent threat to human health (e.g, vapor intrusion), safety (e.g, risk of flooding), and the environment (e.g., poison fish). Since the environmental threat was immediate or imminent, action was necessary. SInce removing the immediate or imminent threat is beneficial and the cost is approved by the Board, the cost is reasonable.
Sites reviewed with SCAP grants had a scope of work, duration, and cost estimate that were necessary and reasonable to fix immediate or imminent threat to public health.
SCAP applicants were awarded grants because they showed there were no other sources of funding, including their own resources, to meet a regulatory agency directive. They showed there were no other sources of funding by providing financial information along with the project scope, duration, and cost estimate for investigation and/or cleanup. There is no broad consideration for this factor. A financial model is used by the Board as part of the assessment process.
Obviously, it’s hard to know on a site-by-site basis what other information the Board might consider in its deliberations. In some cases regulators make recommendations for a grant based on data not previously considered by the Board. The Board recommends routine communication and responding quickly and accurately to information requests.
We looked at who a SCAP grant is for, what projects are eligible for a grant, and the five considerations weighed for awarding a grant. We have the experience to be your partner in the SCAP process. If you are interested in SCAP, contact us for a free consultation.