310 Hidden Valley Ln
San Anselmo 94960 · Sleepy Hollow · Unincorporated Marin · Coordinates: 38.00717, -122.57475
Executive Verdict · Public-Records Synthesis
Zoned R1-BD in Unincorporated Marin with likely ADU & SB 9 infill eligibility and mapped CAL FIRE moderate fire hazard severity zone (state responsibility area) due diligence; benchmark value $1,968,000 ($1,732,000–$2,204,000).
Upsides & Opportunities
- ✓ ADU & SB 9 infill pathways screen as likely eligible
Zoned R1-BD supports ministerial ADU/JADU review plus SB 9 both two-unit development and ministerial urban lot split on a 19,210 sq ft lot.
Source: Unincorporated Marin zoning · CA Gov. Code 66314 & 65852.21
- ✓ Documented permitted upgrades (+$9,450 contributory est.)
Public building records show issued construction/renovation work on this parcel (3 total permits, latest Nov 23, 2021).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) (parcel APN)
- ✓ Above-average reinvestment in Sleepy Hollow
32 substantial renovation & housing permits over 24 months (32.7 per 1,000 parcels vs. 16.3 citywide baseline) (#4 of 22 neighborhoods).
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) (Sleepy Hollow)
Watchouts & Due Diligence
- ! Mapped flood awareness zone (Zone X: minimal flood hazard)
all of the lot of the parcel intersects Zone X: minimal flood hazard. Outside mandatory federal SFHA insurance rules, but check local drainage and finished-floor requirements.
Source: FEMA National Flood Hazard Layer (parcel polygon)
- ! CAL FIRE Moderate Fire Hazard Severity Zone (State Responsibility Area) (all of the lot of lot)
Located in a mapped Fire Hazard Severity Zone. Expect Chapter 7A ignition-resistant building standards, defensible-space inspections, and stricter property insurance underwriting.
Source: CAL FIRE FHSZ (map Apr 1, 2024)
- ! 6 slow or stalled nearby projects within ½ mile
Closest lead: New home at 830 Butterfield Rd (0.27 mi S, issued). Inspect timeline history before assuming near-term completion.
Source: County of Marin Community Development Agency, Building Permits (unincorporated Marin) · HCD APR (½-mile radius)
- ! Year 1 Prop 13 tax reset (~$23,082/yr at $1,968,000)
Sale triggers reassessment to 1.00% base + ~0.15% voter debt (~$1,924/mo). Confirm exact Mello-Roos / CFD special assessments on the county tax bill.
Source: CA Const. Art. XIIIA (Prop 13) · County Tax Collector
Parcel & Assessor
- Lot size:
- 19,210 sq ft (0.44 ac)
- Assessor use:
- Single-Resid. - Improved
- Addresses on lot:
- 310 HIDDEN VALLEY LN
Zoning & Land Use
R1-BD — Residential Single Family (Unincorporated Marin)
State Housing Pathways Screen (ADU & SB 9)
- ADU or junior ADULikely eligible
Zoned R1-BD (single-family residential): state law allows ADUs where homes are allowed.
- SB 9: two homes on the lotLikely eligible
Zoned R1-BD, a single-family residential zone.
- SB 9: split into two lotsLikely eligible
Zoned R1-BD, a single-family residential zone. The lot is 19,210 sq ft by the assessor, room for two lots of at least 1,200 sq ft, each at least 40% of the original.
Mapped Hazard Zones on This Lot
- CAL FIRE Fire Hazard Severity Zone
- Moderate Fire Hazard Severity Zone (State Responsibility Area) (all of the lot, map Apr 1, 2024)
- FEMA National Flood Hazard Layer
- Zone X: minimal flood hazard (all of the lot) · FIRM panel 06041C0289D, effective May 4, 2009
- CGS Alquist-Priolo Earthquake Fault Zone
- Not in an Alquist-Priolo Earthquake Fault Zone
Surrounding Rent & Value Benchmarks (Public Records)
Range: $1,732,000 – $2,204,000 · Status: Off market
HUD Small Area FMR (ZIP 94960) · FY 2026
Studio $2,510 · 1BR $3,010 · 2BR $3,640 · 3BR $4,650 · 4BR $4,820
Developments Deserving Closer Investigation & Active Area Builders
- New home at 830 Butterfield Rd (Issued)0.27 mi S
Active in "Issued" for 8.3 yr (first record Aug 9, 2018) with no new permit activity recorded in 7.6 yr. High-impact scale (1 housing unit, $1,097,000 declared valuation across 2 permits).
- Accessory dwelling unit at 990 Butterfield Rd (Applied)0.12 mi W
In "Applied" for 5.8 yr (since Jan 13, 2021), exceeding the 253d median and 686d 90th percentile for new single-family home permits in Unincorporated Marin (n=121).
- Demolition at 854 Butterfield Ln (Applied)0.26 mi S
In "Applied" for 2.3 yr (since Aug 1, 2024), exceeding the 55d median and 261d 90th percentile for demolition permits in Unincorporated Marin (n=130).
- Demolition at 111 Deer Hollow Rd (Applied)0.46 mi S
In "Applied" for 6 yr (since Nov 9, 2020), exceeding the 55d median and 261d 90th percentile for demolition permits in Unincorporated Marin (n=130).
Entity-resolved builders & contractors in ½ mile: Owner (1 on parcel, 11 in ½ mi · Remodel / interior alteration); Hettrich Construction (1 on parcel, 3 in ½ mi · Addition (adds square footage)); Solarcraft Services (1 on parcel, 1 in ½ mi · Solar / battery storage); Owner Builder (33 in ½ mi · Remodel / interior alteration); Drake Building (4 in ½ mi · Remodel / interior alteration).
Permit & Project History on This Parcel (3 permits, 0 grouped projects)
| Record # | Category | Status | Applied / Issued | Valuation | Description |
|---|---|---|---|---|---|
| B27864 | Solar / battery storage | Issued | Iss. Nov 23, 2021 | $26,250 | (N) FLUSH MOUNTED 9.12 kW PV SYSTEM W/ GRID TIED MICROINVERTERS |
| 168996 | New garage / accessory structure | Issued | Iss. Aug 4, 2021 | $347,000 | Remod, Addtn, New Part Roof |
| B23364 | Electrical / panel | Issued | Iss. Aug 26, 2020 | $1,200 | Upgrade main electrical service panel. — Service Upgrade |