Repeal of an Ordinance Requiring Methane Testing on Projects with Mass Grading; POD04-068 / Log No. 04-00-004

Summary

SCH Number
2005049038
Lead Agency
San Diego County
Document Title
Repeal of an Ordinance Requiring Methane Testing on Projects with Mass Grading; POD04-068 / Log No. 04-00-004
Document Type
NOD - Notice of Determination
Received
Posted
4/22/2005

Document Description
The County of San Diego is proposing to repeal the ordinance requiring methane testing on mass graded sites. Since the methane-testing ordinance became effective, subsurface methane gas has been tested at projects in several areas of the County. In each of these occurences, the subsurface methane gas exhibited very similar characteristics, including the following: 1) the gas was not under pressure, 20 the gas was found almost exclusively in engineered fill soils; 3) the gas was found only in small volume; and 4) the source of the subsurface methane gas is associated with the natural degradation of organic materials within the engineered fill. Because the subsurface methane gas is not under pressure and is associated with small amounts of organic materials in engineered fills, the potential risks are much lower than other types of occurences. This was confirmed with the completion of a computer modeling, which found that despite the numerous layers of conservatism built into the simulations, the model showed that potentially hazardous concentrations of methane would not accumulate on the interior of a structure, even under worst-case scenarios in the absence of methane mitigation measures. Given this finding, methane mitigation measures for structures do not appear to be warranted.

Contact Information
Jeff Murphy
San Diego County Department of Planning and Land Use
5201 Ruffin Road, Suite B
San Diego, CA 92123-1666

Phone : (858) 694-3730

Location

Counties
San Diego
Regions
Unincorporated

Notice of Determination

Approving Agency
San Diego County Board of Supervisors
Approving Agency Role
Lead Agency
Approved On
Final Environmental Document Available at
County of San Diego Department of Planning and Land Use Project Processing Counter 5201 Ruffin Road, Suite B San Diego, CA 92123

Determinations

(1) The project will have a significant impact on the environment
No
(2a) An Environmental Impact Report was prepared for this project pursuant to the provisions of CEQA
No
(2b) A Negative Declaration was prepared for this project pursuant to the provisions of CEQA
Yes
(2c) An other document type was prepared for this project pursuant to the provisions of CEQA
No
(3) Mitigated measures were made a condition of the approval of the project
No
(4) A mitigation reporting or monitoring plan was adopted for this project
N/A
(5) A Statement of Overriding Considerations was adopted for this project
N/A
(6) Findings were made pursuant to the provisions of CEQA
N/A
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