Methane Mitigation System for Buildings 1


Methane Mitigation Systems for Buildings

A methane mitigation plan is a comprehensive design that eliminates the hazards of methane soil gas intrusion into buildings. For instance, new structures above historical oil fields, landfills or soil contamination areas require mitigation system to ensure the safety of occupants. Without proper methane mitigation, toxic vapors can migrate through foundations. Consequently, this processes causes a lethal accumulation of methane gas indoors. And as a result, explosive and asphyxiation hazards endanger the occupants. Updated December 27, 2018.

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Methane Mitigation Barrier System. Methane Barrier Deputy Inspection Photo.

Methane Mitigation Barrier System. This photo taken during methane deputy inspection.

Reasoning Behind Methane Mitigation

In the City of Los Angeles, these plans are a requirement for projects within Methane Zones or Methane Buffer Zones. Similarly, other California Cities and Counties also require mitigation systems in special hazard districts. These zones (or districts) are a result of regional subsurface contamination plumes from oil and gas fields, as well as landfills. Additionally, mitigation plans require a strict review and approval process with each local building department.

Methane Testing

Generally, the design parameters of a methane mitigation system are a reflection on the results of a methane soil gas test. Using drilling methods, geologists follow a strict set of standards to install soil gas probes at various depths below ground surface. Each soil gas probe includes a special vapor implant which then applies to collecting a representative vapor samples from the pore spaces of soil underground. And an assessment requires numerous samples from various depths and locations.

Methane Testing initially includes a shallow probe soil gas survey. Afterwards, a drilling rig is used to drill and install multiple sampling zones underground.

Methane Testing Shallow Soil Gas Probe – Photo Credit: University of Texas at Austin & Bureau of Economic Geology

Huntington Beach & Los Angeles Mitigation Standards

The City of Los Angeles publishes a map of high-risk “Methane Zones” and “Methane Buffer Zones.” For properties in a Methane Zone or Buffer Zone, there is a requirement to comply with Los Angeles Department of Building and Safety (LADBS). Site-specific design parameters for the system are based on the data from a methane soil gas test. There are various LADBS mitigation design levels. Accordingly, the mitigation system requirements increase with each level. As a result, the plans can include specialized ventilation systems that are either “Passive” or “Active.”

Methane Mitigation Methane Barrier Installation

Methane Mitigation Barrier Installation ©MTACapitalConstruction

Passive Vapor Mitigation Systems

Passive ventilation systems are complex engineering projects which intend to block, and remove, hazardous gas from underneath buildings. A passive system relies on the natural rising characteristics of hydrocarbon and volatile organic compounds gas, in order to capture the accumulations underground. Furthermore, the system is strategically set-up to direct the gas upwards and around the structure, exhausting it into the atmosphere.

Passive Methane Mitigation Subsurface Piping

Passive Methane Mitigation System

Active Vapor Mitigation Systems

Active methane mitigation systems comprise of electrical engineering projects, for subsurface gas extraction purposes. These systems operate via the use of blowers, pumps, fans, sensors and a control panel. Moreover, HVAC systems accelerate indoor ventilation. Additionally, an active system includes methane gas sensors and an alarm system. This warns occupants of peaking methane concentrations.

Active Methane Mitigation Systems Include a Methane Gas Alarm

Active Methane Mitigation System – A Methane Gas Alarm

Dewatering and Waterproofing in Methane Mitigation

Dewatering systems lower the groundwater table to a level below the bottom of a soil gas ventilation system. Waterproofing barriers prevent groundwater from passing through a methane barrier. Geo Forward specializes in designing dewatering systems and waterproofing barriers.

Geo Forward Professional Services

The geologists and engineers at Geo Forward are experienced with the latest design standards and building codes. Geo Forward specializes in designing these systems for commercial and residential projects. Moreover, the Geo Forward team is an expert in barrier applications for subterranean parking garages, underground vaults, basements and more.

For more information about methane mitigation plans, call (888) 930-6604 to speak with an expert. 


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