STATE OF CALIFORNIA, PETE WILSON, Governor
January 23, 1998
RE: Variance Request #45 - Allow for open cut trenching of Ramona Avenue to install a High Density Polyethylene (HDPE) geomembrane to protect Hawthorne Well #1, City of Hawthorne, Los Angeles County (Segment 4B).
Dear Mr. Shauers:
We have reviewed the above-referenced variance request, and our decision of approval is based on the following factors:
Open cut trenching at this location has been requested so that a HDPE geomembrane can be installed in the pipeline trench before installation of the pipe (the Project Description in the EIS/SEIR stated that "major roadways, interstate highways, and freeways" would be bored).
Mitigation Measure H-13 requires that the Applicant, in coordination with the State Department of Health Services (SDHS), develop specific design requirements for the pipeline when it is located within 200 feet of an existing water well. In a letter dated May 12, 1997, the SDHS approved the use of HDPE geomembrane liner for the subject well. The HDPE geomembrane is an impermeable material (60 mil thick) designed to isolate the pipeline from any ground water. The geomembrane material would line the bottom and sides of the trench. In the event of a spill, the geomembrane material would prevent the oil from entering the surrounding ground and potentially migrating to the ground water. As required by the SDHS, the liner would extend for the length of the pipeline within a two hundred foot radius of the well head (approximately 178.5 feet in either direction from the west side of Ramona Avenue).
To mitigate potential traffic impacts on Ramona Avenue during trenching, PPSI proposes to use standard open trenching methods, with half the roadway closed during construction. This portion, when completed, would be plated and the second portion of the roadway would be trenched and plated. Traffic would continue to pass in both directions with minor delays. Trenching activities are anticipated to require five to nine working days. Given the temporary nature of the traffic impacts and that vehicle passage would be maintained, no significant impact would occur. Implementation of the measures noted below would further minimize any traffic impact during construction.
The following measures shall be implemented:
- All applicable mitigation measures for the project shall be implemented at the subject location.
- On Monday through Friday, open cut trenching of Ramona Avenue shall be limited to nonpeak traffic hours (9:00 a.m. to 3:30 p.m.). Pipeline installation within Ramona Avenue shall be completed within 10 working days.
- Implementation of this variance in accordance with the provisions noted above shall be verified on a random basis by a CPUC/ANF Environmental Monitor.
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