What is a PCA?
Property Condition Assessments (PCAs) are due diligence level surveys of structures that provide clients with conditions of building components, estimated useful life, and replacement and repair costs over an established assessment term. They can be completed in concert with a Phase I ESA during a traditional due diligence period of a real estate transaction or they can be completed as a stand-alone study to evaluate the current condition of a building and to estimate future capital expenditures and maintenance costs.
This month’s issue of School Construction News featured an article by Alta’s experts Steve Morrill, PE and Bina Patel. Public school sites receiving state funding are required to conduct environmental review and cleanup. Read more here:
Addressing environmental issues early saves time, effort and cost.
Alta Environmental's very own Steve Morrill, senior project manager/engineer, was recently featured in Construction Today, the magazine for the people who build North America. Below is a clip of the article, which you can read in full here:
The historical operation of industrial activities in Southern California including industrial processing, metal plating, aerospace manufacturing, and dry cleaning have resulted in groundwater contamination in the region. Many aquifers have contamination issues from historic overlying land activities. Several remedial technologies for cleanup of chlorinated volatile organic compounds (CVOCs) in groundwater are available, including, but not limited to, Enhanced In situ Bioremediation (EISB), chemical oxidation, groundwater pump and treat, air-sparging with vapor extraction, high-vacuum dual-phase extraction, thermal injection, electrical resistance heating, permeable reactive barriers using zero-valent iron, and monitored natural attenuation. In evaluating these technologies, several factors are considered, including system effectiveness, implementability, impact on business/facility operations, regulatory acceptance, permitting requirements, safety, and cost.
Releases or discharges of pollutants to subsurface soils commonly occur at various industrial and commercial facilities that utilize and store petroleum products, or that produce industrial waste. Such facilities may include aerospace facilities, dry cleaners, manufacturing facilities, active and former gasoline service stations, metal plating and finishing shops, and oil field sites. Volatile organic compounds (VOCs), such as gasoline or chlorinated solvent compounds, may be released into the subsurface from various source areas within these facilities, which may include aboveground or underground storage tanks, clarifiers, piping, drum storage areas, cleaning/wash areas, etc.
Within the subsurface, contaminants may exist in the subsurface in the following phases: as a solid phase by adsorbing onto soil, dissolved phase in groundwater, liquid phase within the soil pore spaces, and/or in the gaseous phase within soil pore spaces. Although full characterization of each phase is essential for most investigations, from a vapor intrusion standpoint, it is particularly important to assess for VOCs in the gaseous phase. Vapor intrusion into residential or commercial structures occurs when VOCs in the soil gas migrate into building structures through cracks or openings in the concrete slab.
Soil gas investigations are normally conducted in accordance with the Advisory – Active Soil Gas Investigations (Advisory), prepared jointly by the Department of Toxic Substances Control, the Los Angeles Regional Water Quality Control Board (LARWQCB), and the San Francisco Regional Water Quality Control Board, dated July 2015. The Advisory provides technically defensible and consistent approaches for the collection and analysis of soil gas samples, and applies to both subsurface soil gas samples collected outside building perimeters and beneath sub-slab areas within buildings. The Advisory is not a regulation, instead it provides technical framework and reference for addressing soil gas sample collection and analysis.
Due to recent developments in the field of soil gas collection, the 2012 version of the Advisory was revised in July 2015. The July 2015 version also supersedes previous versions produced in 2003 and 1997. The 2015 Advisory provides detailed procedures to determine locations, spacing, and depths of soil gas probes, and procedures for the installation, design, and sampling of soil gas probes. Procedures for laboratory analysis of soil gas samples, including QA/QC protocols, are also included.
A typical soil gas probe design consists multiple probes installed in a single borehole. The probes are located at or near contaminant source areas, and on a predetermined grid pattern to delineate the lateral extent of VOC plumes. The borings are initially advanced with the use of a direct push or hollow stem auger drilling rig, or by hand augering methods. Soil gas probes, consisting of Nylaflow®, polyetheretherketone (PEEK), or Teflon® tubing, are then installed at multiple depths (such as 5, 10, and 15 feet below ground surface, or deeper depending on depth of the source area) to vertically delineate VOC plumes. A probe tip, usually 6 inches in length, is also attached to the end of each tubing. The annular space surrounding the probe tips are backfilled with a sand filter, followed by dry granular bentonite and hydrated bentonite or neat cement grout between probes. Soil gas samples are then typically collected and analyzed for VOCs with the use of a mobile laboratory, in accordance with EPA 8260B procedures.
Notable revisions to the 2015 Advisory (from the 2012 Advisory) include the following:
The updated Advisory can be found at:
For questions, please contact Steve Ridenour (email@example.com). We can also be reached by phone at 562-495-5777.
Alta Environmental is at the forefront of technology developments in remediation for some of the most challenging contaminated properties. Based on our depth of experience and ongoing work with various technology providers, we’ve assembled a brief overview of current issues and emerging techniques for addressing chlorinated solvents that may affect groundwater supplies.
Chlorinated solvent compounds such as tetrachloroethene (PCE) and trichloroethene (TCE) are commonly used in cleaning and manufacturing processes at various industrial/commercial facilities, including aerospace, dry cleaning, metal plating and finishing, and other facilities where solvents are used. PCE and/or TCE and associated degradation compounds such as cis-1,2-dichloroethene (DCE) and vinyl chloride are often released or spilled into the underlying soils and groundwater. If groundwater is affected, the uppermost aquifer is usually impacted. However, because chlorinated solvent compounds are denser than groundwater, the compounds may sink to the bottom of the upper aquifer and possibly may affect lower aquifers that are used for local groundwater supplies.
Remediation of chlorinated solvent compounds, particularly if groundwater is affected, is usually regulated by the California Regional Water Quality Control Board or the Department of Toxic Substances Control. The regulatory agencies require preparation and implementation of a Remedial Action Plan (RAP) which outlines various remedial alternatives that are applicable for an impacted site, and describes the scope of work, costs, and schedule of the selected remedial alternative. Effective implementation of the RAP is critical because not only is it directed by the regulatory agency, but also allows the affected aquifer to be restored to productive use and minimizes impact to drinking water wells if those wells are threatened.
Construction of permeable reactive barriers (PRBs) within the impacted aquifer is an emerging remedial alternative for control and capture of chlorinated solvents in groundwater. This technology is not exactly new, but is becoming more prominent and cost-effective as an accepted and viable remediation approach. The PRB wall is constructed along a line across the PCE/TCE plume, within a downgradient portion of the aquifer (such as along the property line thereby preventing further migration offsite) or where control and capture of the contaminants is needed (such as upgradient of sensitive receptors). The PRB is constructed by installing a mixture of dechlorinating products, including include zero-valent iron (ZVI), emulsified vegetable oil (EVO), and dehalococcoides (DHC). For shallow aquifers (i.e, less than 25 feet below grade), the PRB wall is constructed with the use of an excavator, and the width of the PRB is therefore equal to the width of the excavating bucket (typically 1 to 2 feet wide). For deeper impacted aquifers, the PRB is constructed via hydro-fracturing by drilling a row of injection points with a direct-push or hollow-stem auger drilling rig, and injecting the materials into the borings with an injection pump. The injection points are spaced at equidistant points along the planned PRB wall location, and the PRB is usually about 3-6 inches wide.
The ZVI/EVO/DHC mixture causes dechlorination of dissolved-phase PCE/TCE at the PRB wall. Specifically, the ZVI provides an electron donor which is attached to the PCE/TCE compound and breaks down the bonds in the compound, the EVO provides a substrate (food) for microorganisms thus nourishing the microbial population, and the DHC increases the rate of bioremediation – allowing a more rapid transformation of PCE to TCE, TCE to DCE, and DCE to vinyl chloride, and then to the final by-product (ethane).
It is important to note that likely within the next 2-3 months, DHC will be accepted by the RWQCB on the general WDR permit, thus decreasing permitting time. Currently, a site-specific permit for injection of DHC is required, in which case it can take a year or longer for use of DHC to be approved.
If you are interested in learning more about this technology, or if you wish to discuss other remedial technologies which are used to remediate chlorinated solvent compounds, please contact Steve Ridenour (firstname.lastname@example.org), or call us at (562) 495-5777.
GeoSierra Environmental, Inc.