Surface emissions monitoring – some tips on corrective actions and a nifty new data management tool to help you keep track of it all
As someone who is deeply involved in conducting surface emissions monitoring (fondly known as SEM) at landfills around the country, I have a few tips on corrective actions that often need to be taken. Also, I recently developed a tool to keep track of the data we collect, and I thought others might be interested in learning about it.
First a bit of regulatory background on SEM
Municipal Solid Waste (MSW) Landfills regulated by New Source Performance Standards (NSPS) are required to have a gas collection and control system (GCCS) designed to minimize off-site migration of landfill gas (LFG). As part of these regulations, owners/operators are required to conduct SEM on a quarterly basis. SEM is necessary to ensure that the GCCS is working properly, minimizing methane (CH4) emissions. Acceptable emissions are less than 500 parts per million by volume (ppmv) above background levels.
Under NSPS WWW 40 CFR 60.753(d), surface emissions must be monitored along the perimeter and in a serpentine pattern that traverses the landfill at 30-meter (100-ft) intervals and where visual observations indicate elevated concentrations of landfill gas, such as distressed vegetation and cracks or seeps in the cover.
Keep in mind that USEPA recently finalized the NSPS Subpart XXX and Emissions Guidelines (Subpart Cf) and these new rules contain additional requirements for monitoring cover penetrations and recordkeeping for exceedances. Be sure to review whether your site is subject to NSPS XXX and update your SEM plans as necessary. As the Emissions Guidelines are implemented at the state level, there may be additional changes in the SEM requirements. The rules may result in changes to requirements at sites, so be sure to track how the updated rules affect your site.
Conducting SEM safely
SEM should only be done when it is safe for field staff members. Be sure to conduct the monitoring under typical meteorological conditions. Make sure the GCCS is operating at normal conditions and the well field is tuned so the extraction wells are operating under vacuum.
Follow a rigorous SEM process
We follow a specific process for conducting SEM. Here are the basics:
- First, confirm that weather conditions are acceptable or typical
- Next, calibrate your monitor
- Calibrate using the manufacturer’s recommendations and EPA Method 21
- Allow your monitor to warm up for 15 to 20 minutes in an area near where you are monitoring, to ensure similar atmospheric pressure conditions
- Make sure you conduct this same calibration prior to monitoring each day
- Use unexpired calibration gas (zero and 500 ppm)
- Conduct your background determination
- Measure upwind and downwind concentrations outside the landfill’s boundary – at least 30 meters from the perimeter wells.
- Keep records of weather conditions before and after monitoring, calibration sheets, and gas certifications!
What to do when you detect an SEM exceedance
When you detect an SEM exceedance, conduct a visual inspection of the area and be sure to mark exceedance locations. Remember, any closed landfill that has no exceedances in three consecutive quarters may switch to annual monitoring! However, if you find an exceedance during annual monitoring, you must switch back to quarterly monitoring.
After you find an exceedance, there are a few corrective actions you can take. First is adjusting wells by increasing the vacuum of wells in the vicinity of the exceedance. You can also perform maintenance on cover soils by using low permeability soils and/or bentonite. Increasing the system vacuum, installing a liner boot, or using expandable foam can also be corrective actions.
When all the necessary re-checks have been completed and there are still methane exceedances, control may require capital improvements, such as modification or expansion of the GCCS by installation of new vertical wells, blower upgrades, header pipe upgrades, control device upgrades, or removal of free liquids from the well.
Tool for SEM exceedance evaluation
All of these monitoring activities generate a lot of extremely important data. I recently developed a tool to help our field staff with record keeping and reporting on methane exceedances. The Excel-based tool makes it easy for field staff to track exceedance areas and dates to make sure they conduct the necessary re-checks on time. We have found it to be especially useful at sites with a large number of wells or any other GCCS features penetrating the site’s cover.
Do you have any other tips for conducting SEM?
Edwin Calvache, PE, is an environmental and chemical engineer with more than ten years of environmental engineering and construction management experience.
Categories: Air Quality, Biogas and Landfill Gas, Environmental Planning & Compliance, Sample Category
Posted By Edwin Calvache, PE at 1:27 PM | No Comments on Surface emissions monitoring – some tips on corrective actions and a nifty new data management tool to help you keep track of it all
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