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Methane Test

If a new construction project is located within a Methane Zone, the Los Angeles Department of Building and Safety will require a Methane Test.

 Based on the Methane Test results, the property will be classified as Methane Levels 1 through 5. Each Methane Level has corresponding mitigation requirements that need to be implemented in the Methane Mitigation Design and Construction.

During an LADBS Methane Test, probes are placed at depths of 5, 10 and 20 feet below the lowest level of the proposed structure. Methane concentrations are measured, and the highest-level is reported to the Los Angeles Department of Building and Safety.

It is important to provide your Methane Soil Gas Survey engineer with the entire project scope to ensure that the proper information regarding methane mitigation requirements can be communicated.

Methane Zone and Methane Test

LADBS Site Investigation Standards for Methane Testing

The LADBS methane seepage regulations outline site investigation standards for methane. These regulations provide information bulletins, affidavits and forms which give direction regarding the LADBS methane hazard mitigation requirements.

Shallow Methane Test

Methane concentrations for the Shallow Methane Test shall be recorded with a minimum of two per site, at a rate of one sample per 10,000 SqFt.

Deep Methane Test

The location of deep gas probes are based on the results the shallow methane test; Deep Gas Probes shall be installed where the highest concentration of methane soil gas is measured. At least one gas probe is required for every 20,000 SqFt (Minimum of two gas probe sets). Two sequential measurements shall be taken, with a minimum of 24 hours between sampling of the methane probes.

Equipment

Catalytic methane sensors and differential pressure gauges are used to record the methane soil gas concentrations and pressures. Sensors and gauges are calibrated prior to each field

Certificate of Compliance for Methane Test Data

Upon completion of the Methane Test, Sway Features will prepare the Certificate of Compliance, this will include the methane concentrations and methane pressures which will categorize the final methane site design level. The certificate of compliance needs to prepared by a California licensed professional engineer.

Methane Mitigation Design

Based on the results of the Methane Test, a Methane Mitigation System designed by a Licensed Engineer and approved by the Los Angeles Department of Building and Safety will be required.

The Methane Mitigation Components could include;, Passive Sub-Slab Vent, Impervious Membrane, Mechanical Extraction, Gas Detection, Mechanical Ventilation, Alarms, Trench Dams, Conduit Seals, and Dewatering.

Methane Mitigation Contractors

Once a Methane Mitigation Design is approved by the Los Angeles Department of Building and Safety, the design must be implemented within the construction project. The Methane Mitigation Construction must be completed by a specialty contractor that is licensed and certified to do so. During Construction, a Methane Deputy Inspector will have to oversee and approve the installation.

Methane Mitigation Design

Methane soil gas probe construction must be executed based on the ASTM standards while considering the local building code and testing jurisdiction requirements. To initiate the construction, an environmental professional must first establish the underground utility markings. This is a crucial step in Methane Mitigation Construction because it is likely that the construction will cause unintentional environmental, electrical, and sewage damage. Marking all underground utilities ensures that preventative measures are executed to reduce the possibility of destruction to existing underground utilities. These are usually difficult to locate due to the unpredictable utility line routings. A third-party environmental professional might be required to scan the area with ground-penetrating radar to ensure that all borehole locations are cleared. In any case, it is always essential to verify with the methane testing consultant whether the underground utilities will be identified and cleared or not.

After marking and clearing underground utilities, direct push drilling comes next. This process is done using a directly pushed drill rig that forces drilling probes to penetrate the soil with minimal disturbance to the surrounding areas. These drilling probes include polyethylene tubing with vapor probes connected to them. These gas vapor probes will be placed at a certain depth below the ground surface. There could be one probe in a borehole, which is called a single-nested soil gas probe. If two or more probes are installed, these are called dual- and triple-nested soil gas probes, respectively.

Due to the specialty drill rig used in the process and the necessary high skill level of the drillers, direct push drilling costs a significant amount of money. However, this drilling process causes minimal soil disruption, which increases the accuracy of the methane test results, ultimately sparing you from the additional expense due to inaccurate results brought about by the lower-cost rotary drilling technique. Inexperienced environmental engineering companies will usually utilize the rotary drilling technique to lower methane testing costs, maximizing their profit margins.

The vapor filters will be placed typically within a 1-foot column of number three granulated sand. This allows for proper fluid flow during the testing. The testing is generally completed with a monitor, possibly a methane concentration monitor, CH4, and oxygen. These monitors will typically use either infrared sensors or the combustion one with catalytic sensors to test and detect the minimum/maximum methane concentrations below the ground surface. This information will determine which materials should be utilized for the Methane Gas Mitigation Construction, specifically for the installation of Methane Barrier. The methane testing equipment is also calibrated before every project to minimize the chance of error.

The column of sand where the vapor probes are placed is usually packed between Two columns of hydrated bentonite. Bentonite is essentially a clay that expands when hydrated to double the volume, which creates an excellent seal. Because this material surrounds the location of the vapor filters, it will be guaranteed that the probes are sealed tight, and sections are sent between other depths of the borehole.