24H Mold Inspection of Sun Valley

The flat residential core is the reason Los Angeles County wrote a watershed plan for this neighborhood at all: roughly 2,700 acres of Sun Valley were built out after the war with no storm drain system, so runoff had nowhere to go but down the streets, and blocks around Sheldon and Strathern flooded on a schedule every wet winter. The infiltration systems eventually built under Sun Valley Park and at the Strathern Pit exist to catch that water. What flooded is 1940s through 1960s tract housing, much of it slab-on-grade with converted garages, and the water that matters is what wicked up into the bottom of drywall, under flooring, and into garage-turned-living-space.

Stonehurst is a Historic Preservation Overlay Zone built out in the 1920s and 1930s from stone hauled straight out of the Tujunga Wash — walls of native arroyo boulders set in mortar, laid up at grade with nothing underneath them a modern builder would call a moisture barrier. Stone and mortar are porous. They wick ground moisture upward and hold rainwater in the joints long after the face of the wall looks dry, and the usual instinct to seal or paint a damp masonry wall traps that water inside the assembly instead of letting it breathe out. Original wood windows, shallow crawl spaces, and roofs redone several times across a century fill in the rest.

Sun Valley carries one of the densest concentrations of gravel pits, recycling yards, and material-recovery facilities in Los Angeles, strung along Tuxford and Sheldon around the former Sheldon-Arleta and Bradley landfill sites. The buildings are big-span, flat-roofed warehouses and shops on slab, where roofs pond, drains clog with the dust these operations throw off, and large temperature swings condense moisture onto cold steel decking and cool concrete. Wash bays, truck yards, and processing lines add water all day. Houses sit directly across the street from several of these yards, which is why the outdoor spore and dust baseline on these blocks reads differently than a quiet residential street elsewhere in the Valley.

The September 2017 La Tuna Fire burned roughly 7,200 acres through this canyon and the Verdugo slopes above Sun Valley, Shadow Hills, and Burbank, and at the time it was the largest fire ever recorded inside Los Angeles city limits. The storms that followed that winter brought debris-flow warnings and mud off the burn scar. Parcels up here are larger and cut into decomposed granite and chaparral slopes, many on septic, and a good number sit at the mouth of a small drainage that funnels runoff toward them. Burned ground sheds water rather than absorbing it, so what arrives at a retaining wall or a below-grade garage comes fast and from uphill.

The north end of Sun Valley runs up into Glencrest Hills and the Shadow Hills line, where lots get bigger, sidewalks give out, and horse keeping is still normal. These parcels sit on the coarse sand and gravel of the Tujunga alluvial fan — the same deposit the gravel pits down the hill are dug into — which drains fast but sends sheet flow racing down unpaved lanes and long driveways when a storm outruns it. Barns, tack rooms, and wash racks are wet by design and almost never ventilated for it, detached workshops go unheated and unwatched for months, and on septic parcels a failing leach field turns up as saturated ground right against a foundation.