Subslab Depressurization System (SSD) Installation

Subslab Depressurization System (SSD) Installation

Terra-Petra was engaged by the attorney representing the owner of a former dry cleaner in southern California that was experiencing vapor intrusion.

Specifically, indoor ambient air was monitored and determined to have concentrations exceeding commercial screening levels for the following (as well as others):

  • Toluene
  • Tetrachloroethene
  • Dichlorodifluoromethane (CFC 12)

The attorney had requested a way to mitigate the vapor intrusion issues at the site so that the property could be commercially viable again.  As we always do with any existing building Terra-Petra completed an extensive investigation of the building of concern to gain an understanding of what type of Subslab Depressurization System (SSD) would be most effective in mitigating the issue. Terra-Petra completed the pressure field extension testing to determine how much vacuum would be required to extend a minimum sub-slab negative pressure field of -0.016 ” w.c. Understanding how much vacuum is required and where it should be applied is the objective of the permeability mapping portion of any investigation and shall serve as the foundation for our design.

The design of the mitigation plan is the most critical component in the entire process because it determines the remedial design and scope of work. This is the part that eliminates the ad hoc guess work and provides a defined plan. It also eliminates installing a system that is not effective in reducing soil borne contaminants. Additionally, the process eliminates the possibility of overdesigning the system to compensate for uncertainties. Over-designed systems result in excessive installation and operational costs. Once a plan is in place, definite implementation costs can be determined.

As such, Terra-Petra completed the design, which we permitted through the local building department and began installing the system in early February of this year. The system will be online before the end of this month after we complete the installation and run our start up testing.

Installation Progress Photos

Need Vapor Intrusion Mitigation? Contact Terra-Petra Today For Assistance

Feel free to contact Terra-Petra for any of your vapor intrusion mitigation needs.  One of our experienced and friendly team members is standing by to assist you.

Terra-Petra’s Justin Conaway Interviewed On Brownfield Braintrust Podcast with Matt Winefield

Terra-Petra's Justin Conaway Interviewed On Brownfield Braintrust Podcast with Matt Winefield

Terra-Petra Vice President and General Manager Justin Conaway was recently interviewed on the popular Brownfield Braintrust Podcast with Matt Winefield of Winefield & Associates.  On the podcast episode Justin and Matt discuss Vapor Intrusion Mitigation Systems (VIMS) and the state of the current environmental engineering industry and vapor intrusion.  Read more below, and watch/listen to the podcast.

In the current Brownfield Braintrust Podcast, Matt Winefield of Winefield & Associates, Inc. sheds light on Vapor Intrusion Mitigation Systems (VIMS) with the help of Justin Conaway, Vice President and General Manager of Terra-Petra Environmental Engineering. Given evolving soil vapor mitigation standards, VIMS are currently much more prevalent than just three years ago. It is unlikely one can acquire, for example, a former dry cleaner site (with PCE releases), run a vapor extraction system, and then pour your foundation. The lead agency will likely specify a VIMS that operates for the life of the new building. Justin explains the three most common VIMS technologies now utilized.

Listen to the audio only version of this podcast.

Bay Area Vapor Intrusion Mitigation System Design

Terra-Petra Environmental Engineering is providing environmental engineering services for the design of the vapor intrusion mitigation system (VIMS) for a development of affordable Senior Housing in downtown San Rafael, CA. The development consists of the construction of a new six-story building. The building footprint is approximately 14,000 SF.

The site served as a Manufactured Gas Plant prior to the proposed improvements. Site assessment work was completed at the site prior to Terra-Petra’s involvement. A Human Heath Risk Assessment (HHRA) and a Site Conceptual Model (SCM) were carried out to determine the potential risk exposure posed to future construction workers, future commercial occupants and future residential occupants of the building based on VOC’s at the site. It was determined that the calculated risks for all potential receptors were less than the bench marks set forth for the property. The bench marks for this site were HI = 1 and ILCR = 1E-6. Results of the evaluation suggest that soil vapor intrusion mitigation systems may not be required to protect future occupants on this parcel.

The Department of Toxic Substances Control (DTSC) was engaged to serve as the lead regulatory agency at the site. Terra-Petra was directed to design a VIMS system in compliance with DTSC’s published guidelines, which we are in the process of completing.

It will be up to the DTSC to determine if the submitted VIMS design package meets DTSC guidelines and the soil vapor mitigation system provides for adequate human health assurance per the terms of the Land Use Covenant (LUC). If so, the DTSC can formally approve this project. Terra-Petra is confident that our VIMS design will satisfy the mitigation requirements as we have a vast amount of experience designing such systems that have been reviewed/approved by the DTSC.

Aside from the design work, Terra-Petra will be assisting our client in soliciting bids form qualified and experienced vapor intrusion contractors in the Bay Area. We will also be reviewing submittal packages and providing support throughout the Construction Administration Phase of the project. Our inspection crew is slatted to inspect and document the installation of the system using our state of the art field reporting system.

Vapor Intrusion Mitigation System Design & Installation – San Jose, CA

Terra-Petra Environmental Engineering is pleased to provide environmental engineering services for the design of the vapor intrusion mitigation system (VIMS) being proposed for a new affordable housing development in the Diridon Station Area in San Jose, CA.

The project consists of a multi-family residential building having 130 units with 5 stories above grade (no below grade elements). The lowest level will consist of parking with lobby, offices and a community room. The building footprint is approximately 23,400 SF on 1.02 acres.

The site where the proposed building is to be constructed did contain an Underground Storage Tank (UST) potentially containing PCE which was considered to be a Recognized Environmental Condition (REC). As such, soil vapor data was collected from the site during both wet and dry seasons approximately 9 months apart. The data showed that no on-Site sources of PCE have been identified at the Site. Further, no VOCs were detected at concentrations above residential DTSC-AF SLs for future buildings, and no further investigation, evaluation or consideration of exposures associated with VOCs in soil vapor is proposed. Additionally, no residential units were being proposed on the ground floor of the new development. However, the regulatory oversight agency for this site is still requiring that passive Vapor Intrusion Mitigation System (VIMS) be designed and installed at this building.

Terra-Petra was engaged to design a pragmatic code compliant VIMS system that would take into consideration the lack of site-specific risk. As such, we were able to design a creative membrane system that limited the more protective mitigation measures to areas of higher residential occupancy/risk of exposure. These areas included the community room and elevator lobby. While areas of lower risk such as the trash enclosure rooms and parking garage we were able to design a system that would be protective of VI, but also reduce overall cost impacts on the project’s budget.

Terra-Petra will also be providing Construction Administration services and Construction Quality Assurance/Quality Control Services.

Vapor Intrusion Mitigation System – Reno, NV

Terra-Petra is continuing to provide environmental engineering services for the design of the vapor intrusion mitigation system (VIMS) design for the Urology Nevada project located in Reno, NV.

The project will consist of a new slab on grade structure having a footprint of 8,700 SF. Terra-Petra designed the vapor intrusion mitigation system for Phase I of Urology Nevada which consisted of a new slab on grade structure having a footprint of 16,624 SF. The entire site was over-excavated a minimum of 5 feet below finish grade.

Terra-Petra is licensed to perform work in all 50 states!

Although our company started its operations over 20 years ago in Los Angeles to address methane concerns in the region, Terra-Petra has since evolved to become a well-known Environmental Engineering firm throughout the United States, and is certified to work in all 50 states.

No matter where you’re project is located, Terra-Petra’s expertise is available to you.  Learn more about our services, approach and philosophy on our company overview page, or contact us today to get started.

Vapor Intrusion Mitigation System Design And Installation – Santa Fe Springs, CA

Terra-Petra’s Environmental Engineering Division has partnered with a Los Angeles REOC and investment management firm to design a comprehensive Vapor Intrusion Mitigation System (VIMS).

The new development, located in Santa Fe Springs, CA, will consist of a tilt-up industrial warehouse building, on grade, with an approximate building footprint of 150,500 SF. The gas vapor mitigation system shall be designed in accordance with a site specific Phase II Environmental Site Assessment report, and in accordance with the Vapor Intrusion Mitigation Advisory published by the C.A. EPA Department of Toxic Substances Control (DTSC) dated October 2011 (Cal/EPA 2011a, 2011b).

Vapor Intrusion Consulting, Testing And Monitoring – San Diego

Terra-Petra has been performing continuous inspections in San Diego at the Witt Mission Valley Apartments project since early this year. Terra-Petra observed the installation of a VI-20 geo-membrane and Liquid Boot Vapor Barrier application with smoke and thickness testing most recently.

Terra-Petra is one of the foremost experts on Vapor Intrusion consulting, inspecting, testing, monitoring and mitigation design in Southern California.  We are conversant with the many laws, codes and regulations at the city, state, county and national level. We understand the testing, design, monitoring and reporting procedures for many different regulatory agencies.

#vaporinstrution #inspection  #CETCOliquidboot #CETCOVI-20 #smoketest

Photo Gallery From Project

Vapor Intrusion Mitigation System Design – San Francisco

Terra-Petra’s Environmental Engineering Division has partnered with a leading environmental consulting firm in the Bay Area to design a comprehensive Vapor Intrusion Mitigation System (VIMS) for a new high-rise residential-rental mixed-use building located in San Francisco, CA.

We will be following the Department of Toxic Substances Control (DTSC) Vapor Intrusion Mitigation Advisory to design a combination passive venting and sub-slab membrane VIMS system as a means of mitigating human health risks associated with PCE in subsurface soil vapor. Our services will also include providing the necessary Quality Assurance/Quality Control Oversight during the installation of the system. This is a process and a role that we feel very comfortable carrying out.

Regardless of the reason, Terra-Petra can design a vapor intrusion mitigation system for you. We routinely design these passive and active Building Protection Systems across numerous cities and counties governed by many different agencies.

A typical Building Protection Systems consists of an impermeable soil vapor membrane and a pressure relief system. Where deemed appropriate, Terra-Petra can design mechanical vapor extraction systems, electronic gas detection and alarm systems; employing the latest technologies.

Among our many capabilities, Terra-Petra offers:

  • A Civil Engineer, Registered Environmental Assessor, Registered Geologist and Certified Engineering Geologist on staff.
  • Years of experience designing code compliant Building Protection Systems for numerous governing agencies.
  • Easy to read comprehensive plans including project specific details and specifications.
  • Passive and Active Design Capabilities.
  • Plan coordination with project Architect, Civil, Structural, Plumbing, HVAC as well as the Landscape Architect.
  • CAD Draftsmen on staff carry an Associates of Science Degree in Computer Aided Drafting Technology and Certificates in Architecture and Design for Drafting.

Vapor Intrusion Mitigation System – Fontana, CA

Terra-Petra has been chosen to provide environmental engineering services for the design of the vapor intrusion mitigation system (VIMS) design for a new logistics center in Fontana, CA.

Over the last couple of years, we have seen an increased demand for vapor intrusion mitigation systems to be designed and installed at large commercial warehouse type buildings. The main driving force appears to be the environmental personality of the property in which the buildings are being constructed. The site history will vary, but a history of industrial or commercial use where the site was subject to a chemical release of some sorts is the commonality.

Whether it be a petroleum hydrocarbon (TPH) impact from a former oil field/oil well or a Volatile Organic Compound (VOC) release from a dry cleaner or manufacturing facility the potential impacts on the health and safety of the future occupants of the building is what needs to be addressed.

Terra-Petra is well equipped at designing these systems for the current conditions, as well as building in contingency design features for potential future changes. Essentially, we design passive venting systems that are easily upgradable to active subslab depressurization systems (with remote telemetry and remote system monitoring and maintenance built into it if such a conversion is warranted in the future).

The proposed development in Fontana will consist of the construction of a new warehouse building having an approximate 260,650 SF footprint. The vapor mitigation measures will specifically include a “passive” vapor barrier beneath the office areas of the planned warehouse building, and the installation of  a passive ventilation layer beneath the vapor barrier. Inclusion of a ventilation layer beneath the vapor barrier would enable it to be made “active” at a later date by adding in-line fans, such as those used for radon mitigation, to the vertical riser pipes inside the warehouse.

Radon Mitigation System – Summit County, CO

Terra- Petra is pleased to partner with a major property developer in Colorado to provide environmental engineering services for the design of a radon mitigation system for their development in Summit County, CO.

The project will consist of the construction of one single family home, and five  attached single family residences all with 3 stories and no basement. The homes are all nearly identical, with an approximate footprint of 2,500 SF. The project requires that a radon mitigation system be “roughed in” for future activation if needed, but our client is requesting that Terra-Petra design radon mitigation systems for each of the proposed buildings.

Terra-Petra has recommended that we design a combination passive venting and sub-slab membrane Radon Mitigation System for the proposed development.

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