Sayre Report - Hazard Mitigation Web Portal - State of California

tests ranged from low to moderate with small patches of high confirming the burn
severity map. The soils in the Sayre Fire are in the loam category and have a
moderately high susceptibility to erosion and will produce moderate sediment flows.
Evaluations of the Los Angeles County Public Works Debris Basins indicate some initial
signs of increased sediment load. The access road at the Pacoima Reservoir was
reported to have had up to 3 feet of erosion sediment blocking the main access to the
Dam. The box culvert under Gavina Avenue was observed to have up to two-feet of
sediment, but could easily become completely blocked. Multiple residential debris
basins and small drainage areas behind a number of homes were evaluated with minor
to no erosion sediment observed from recent storm events.
Mulching, fiber rolls, and straw bales with silt fencing may be used to prevent erosion at
high value sites or to prevent runoff damage to specific roads or site improvements.
Timely maintenance after storm events on road drainage crossings, culverts, and catch
basins can help keep access open and homes safe. it is recommended that signs be
posted to deter activities that would increase erosion damage. Road access could also
be limited by maintaining locked gates at entrance points to major roads.
Water Quality
Areas of concern are residential areas immediately downstream of the burned area,
especially below culverts and drainages. The values at risk are: possible loss of life and
property due to flooding caused by blockages, debris flows, slope- and water-generated
landslides, rock fall, associated hazards, and impacts to water quality.
The Oakridge Mobile Home Park, which is located at the base of the foothills in Sylmar,
California, consumed approximately 480 mobile homes in a catastrophic fire event. It is
assumed that because the structures were lost, are on a slope, and that burned manmade
materials remain, the potential for these materials to be mobilized is increased
during a rain event. If that is the case, there is potential for impact to waters of the state
or U.S. If the drainage from Oakridge (if the burned materials remain) is not diverted,
contained, or sent to a water treatment facility. It is also expected that increased
turbidity downstream will occur as a result of increase in sediment and debris coming
from the burned Sayre Fire area.
Structural Engineering
Multiple residential structures were damaged or destroyed by the Sayre Fire. Seven key
infrastructure debris basins need remediation, one county agency bridge needs repair,
one equipment shed was destroyed, numerous Metal Beam Guard Railing (MBGR)
timber posts along Fwy. 210 North and South bound Connector to Interstate 5 do
require replacement. Four major bridge structures (Glenoaks, Yarnell, and Fwy 210
North and South bound to Interstate 5) close to the vicinity of the fire area have not
suffered any structure damage.