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.
Relative to the Methane Test results, the property will get a label as Methane Levels 1 through 5. Each Methane Level has corresponding mitigation rules. Implementation of the requirements in the Methane Mitigation Design and Construction is important.
During an LADBS Methane Test, probes go into depths of 5, 10 and 20 feet below the lowest level of the structure proposal. Once measuring Methane concentrations is complete, the top level goes 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. This ensures that the proper information regarding methane mitigation rules are in communication.
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 from the
shallow methane test. Deep Gas Probes install where the highest concentration
of methane soil gas is measured. At least one gas probe is the requirement 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 useful to record the methane soil gas concentrations and pressures. Sensors and gauges are calibrated prior to each field day.
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 acceptable by the Los Angeles Department of Building and Safety, the design implements within the construction project. The Methane Mitigation Construction completes through a specialty contractor that has license and certification to do so. During Construction, a Methane Deputy Inspector will have to oversee and approve the installation.
Methane Soil Gas Probe Construction
Methane soil gas probe construction executes 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 execute 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 a requirement to scan the area with ground-penetrating radar. This ensures that all borehole locations are clear. In any case, it is always essential to verify with the methane testing consultant whether the underground utilities will identify and cleared or not.
After marking and clearing underground utilities, direct push drilling comes next. This process is complete using a directly push drill rig. It 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 place at a certain depth below the ground surface. There may be one probe in a borehole, which is known as a single-nest soil gas probe. If two or more probes are to install, these are known as dual- and triple-nest soil gas probes, respectively.
More on Methane Mitigation Direct Push Drilling
Due to the specialty drill rig used in the process and the necessary high skill level of the drillers. A direct push drilling costs a significant amount of money. However, this drilling process causes minimal soil disruption. Thus increases the accuracy of the methane test results, ultimately sparing you from expense padding due to false results brought about by the lower-cost rotary drilling technique. Inexperienced environment engineering companies will usually utilize the rotary drilling technique to lower methane testing costs, maximizing their profit margins.
The vapor filters will place commonly within a 1-foot column of number three granulated sand. This allows for proper fluid flow during the testing. The testing is generally complete with a monitor, possibly a methane concentration monitor, CH4, and oxygen. These monitors will typically use either infrared sensors or the combustion one. Which has catalytic sensors to test and detect the minimum/maximum methane concentrations below the ground surface. This information will determine which materials will be in use for the Methane Gas Mitigation Construction. Specifically for what will be in use for the installation of Methane Barrier. The methane testing equipment must calibrate before every project to minimize the chance of error.
The column of sand where the vapor probes go is usually between Two columns of moist bentonite. Bentonite is essentially a clay that expands when moist to double the volume, which creates an excellent seal. Because this material surrounds the location of the vapor filters, it guarantees the probes sealant are tight. Then the sections place between other depths of the borehole.