 When the creek reaches Arastradero Road it is joined from the left by an ephemeral creek (locally named Mayfly Creek), and then turns abruptly east and flows along the road into Los Altos Hills to its confluence with Matadero Creek, at the intersection of Arastradero Road with Page Mill Road.The Pearson-Arastradero Preserve is unusual in its intensive ecological restoration program where Grassroots Ecology, a Palo Alto-based environmental group, acts as a steward for the preserve and engages community volunteers in programs that combine habitat restoration with environmental education and accommodate a wide range of volunteers from high schools to local corporations.Their projects focus primarily on removing yellow star thistle ("Centaurea solstitialis"), Medusahead grass ("Taeniatherum caput-medusae"), poison hemlock ("Conium maculatum"), Italian thistle ("Carduus pycnocephalus"), wild mustard and teasel and replacing these invasives with native species.