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City of Pleasanton—Hidden Canyon Residences and Preserve
<br />Biological Resources Draft EIR
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<br />3.3-6 FirstCarbon Solutions
<br />https://adecinnovations.sharepoint.com/sites/PublicationsSite/Shared Documents/Publications/Client (PN-JN)/2148/21480016/EIR/3 - Draft EIR/21480016 Sec03-03 Bio Resources.docx
<br />Chaparral–1.85 acres
<br />Chaparral habitat occupies 1.85 acres along Dublin Canyon Road and includes the following species
<br />yarrow, coyote brush, sticky monkeyflower, poison-oak, coast live oak, elderberry, and mule’s ears
<br />(Wyethia sp.).
<br />Developed Land–1.42 acres
<br />Two houses with associated outbuildings and landscaping/gardens exist within the northeastern
<br />corner of the project site, south of Devany Creek. The currently developed portion supports mainly
<br />non-native landscaped or edible plants and some non-native invasive plants, including the following
<br />asparagus (Asparagus officinalis), wild oats (Avena occidentalis), black mustard, Ripgut brome, soft
<br />chess (Bromus hordeaceus), Cedar (Cedrus spp.), bull thistle (Cirsium vulgare), miner’s lettuce,
<br />loquat (Eriobotraya japonica), filaree (Erodium spp.), Italian rye grass (Festuca perennis), fig,
<br />Strawberry (Fragaria spp.), English ivy (Hedera helix), Hydrangea (Hydrangea macrophylla), iris (Iris
<br />spp.), juniper (Juniperus spp.), privet (Ligustrum spp.), magnolia (Magnolia grandiflora), apple
<br />(Malus domestica), mallow (Malva spp.), petunia (Petunia integrifolia), pine (Pinus spp.), smilo grass
<br />(Piptatherum miliaceum), and others.
<br />Seasonal Wetlands–0.54 acre
<br />Seasonal wetlands occur in the northern portion of the project site near Dublin Canyon Road. These
<br />seasonal wetlands meet the criteria of wetlands, including the presence of dominant hydrophytic
<br />vegetation, hydric soils, and wetland hydrology.
<br />On-site seasonal wetlands were identified in the revised 2016 Waters of the United States map but
<br />were considered isolated by the USACE in 2017 (Appendix F of the BE). However, 2023 conditions
<br />show that these seasonal wetlands appear to be hydrologically connected to Devaney Creek. The US
<br />National Hydrography Dataset illustrates the conveyance of ephemeral flows from these seasonal
<br />wetlands to Devaney Creek just past the northern boundary of the project site. Additionally, these
<br />seasonal wetlands appear to have a contiguous surface connection to an off-site roadside ditch that
<br />drains into two large culverts conveying flows underneath Dublin Canyon Road and appearing to
<br />contribute flows to Devaney Creek. Based on a 2023 site visit, the USACE issued a Preliminary
<br />Jurisdictional Determination (PJD) on August 15, 2024, and accepted all features on-site as under
<br />their jurisdiction including seasonal wetlands (0.54 acre), tributary waters (1.48 acres and 6,997
<br />linear feet), seasonal wetland gulley (0.001 acre and 71 linear feet), and a roadside ditch (0.06 acre
<br />and 266linear feet). The PJD and corresponding verified delineation map can be found in Appendix C.
<br />Similar to the 2016 survey, all of these seasonal wetlands were completely dry and dominated by
<br />non-native wetland species, including poison hemlock and perennial wildrye. Other vegetation
<br />included irisleaf rush (Juncus xiphiodes). Other non-dominant vegetation included rabbitsfoot grass,
<br />mugwort, and curly dock (Rumex crispus).
<br />A seasonal wetland gully conveyed flows from upslope seasonal wetland swales to downslope
<br />seasonal wetland swales. Dilapidated pipes occurred within these gullies, indicating either current or
<br />remnant water conveyance usage. This seasonal wetland gully exhibited an unstable bank and bed
<br />mostly barren of vegetation. However, the bed supported some hydrophytic vegetation including
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