California Department of Resources Recycling and Recovery (CalRecycle) 

Partnership 2000

Mitigating Landfill Gas Explosion Hazards through Continuous Monitoring Case Study: Newport Terrace Landfill/Newport Beach

Abel Martinez-Centeno, Permitting and Enforcement Division, CIWMB.


The Newport Terrace Landfill (aka Newport City Dump # 1) was owned and operated by the City of Newport Beach between 1953-1967. The Orange County LEA requested the assistance of the Board to assess the potential of gas migrating into buildings on-site, among others issues. CIWMB performed a gas investigation of structures on-site using a 10-channel continuous gas monitoring system, which operated on a 24x7 basis for 18 months. The field results obtained through the use of the continuous monitoring system were instrumental on the assessment and determination of:

  • Gas migration status and impact of on-site structures, as well as to;
  • Determine compliance of facility structures

Section 20931(a), states that monitoring of on-site structures includes but is not limited to buildings, subsurface vaults, utilities or any other areas where gas build up would be of concern.

Site Location

Site is located in the northeast of the intersection of West 19th Street and Balboa Blvd., in Newport Beach. Site totals an area of 41 acres. The 41-acre site was acquired by the City of Newport Beach in 1953 from the City of Costa Mesa and subsequently mined and landfilled.


The Sully Miller Company under contract with the City of Newport Beach, utilized portions of the site for extraction of materials used in the production of asphalt. Site was subsequently utilized as refuse disposal area. In preparation for the site to be developed, several site geology and soils investigations were conducted at the site to determine the earth and foundation work needed prior to development.

Site was developed into a condominium complex in 1972 and was completed in 1975.

  • Engineering controls established at the site include a 15 feet-deep sand vent trench.
  • And a gas extraction and collection system completed in 1975.

Site Conditions

Upon termination of mining operations, excavations at the site were filled with inert solid materials, drill cuttings, paper, plastics, glass, metals and grass clippings. Two areas predominate at the site, the rubble fill area composed mainly of inerts and drill cuttings, and the refuse fill area where all the other materials went.

The gas barrier was used to stop gas from moving into the condominiums located east and west of the refuse area. The gas extraction and collection system was completed in 1975. The gas collection system was installed to extract gas in both areas (rubble and refuse).

Site conditions that triggered the LEA’s and CIWMB’s intervention included: Several gas monitoring probes exceeding the gas rule at the perimeter boundary, specifically those in the east and south boundaries, also the presence of “Hot Spot” areas localized among residential structures on the west side of the development. Given that some of the deep monitoring probes and extraction wells near the residences in the west side showed high concentrations of methane, the use of a continuous monitoring system was deemed necessary to assess structure safety with respect to levels of methane.

Gas Assessment

The assessment to be implemented had to be specific and target 3 main issues.

  • Determine structure safety with respect to concentrations of methane gas and compliance with State Minimum Standards.
  • The assessment had to be able to simulate the worse case scenario, for example, the gas migration through preferential pathways originated by breaks through the cover and slab-on-grade foundation by utilities, cracks, tree-roots, etc.
  • The data collected had to be representative and statistically valid to be able to make a confident determination of the gas occurrences at the site; hence a continuous monitoring system was warranted.

Continuous Gas Monitoring System

The system utilized was a 10-channel continuous monitoring system with hardwire connections and the following components:

  1. Remote sensor (catalytic combustible gas detector), explosion proof with a detection range from 0 ppm to 50,000 ppm (LEL) in 45 secs.
  2. 10-channel controller operated at 120 volts with capability for audio alarms.
  3. Data-logger, battery and 120 volts AC operated logging system left at site to collect data at any rate specified by user. The collected data was then transferred to a PC connected remotely via modem to the logger.

10-Methane sensors were installed and operated on the west side of facility to assess on-site residential structures. The total area covered equals 2-acres and was targeted on the locations with the “Hot Spots”. System was operated on a 24x7 basis and during the 18 months of operation methane was not detected on the areas of study.

Conclusions and Final Determination

Some of the high notes about this assessment are:

  1. System showed to be very reliable for this application once the system ups and downs were figured out and proper calibration and maintenance was provided.
  2. The amount of data collected was definitely very valuable and inexpensive when compared to manual labor of doing monitoring with portable instruments.
  3. One of the pluses of this system is the convenience of remotely accessing it to download data and to change its programming. This feature could also be used to alarm or page someone to inform of a high gas level.
Last updated: August 31, 2005
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Melissa Hoover-Hartwick: (916) 341-6813