Key Takeaways
- Signal Hill was once the most productive oil field per acre in the world, and the dense concentration of abandoned wells creates some of the highest sustained methane readings in the greater LA area.
- Signal Hill falls under the City of Long Beach Building Department jurisdiction — not LADBS — which applies a separate methane mitigation code with its own classification system.
- According to CalGEM records, more than 300 wells were drilled within Signal Hill’s 2.2 square miles, creating one of the densest abandoned-well environments in California.
- Residential development has replaced the oil derricks, but the subsurface petroleum deposits and compromised well casings remain, generating ongoing methane migration.
Signal Hill sits atop the Long Beach Oil Field — a geological formation that produced more oil per acre than any other deposit in world history when it was discovered in 1921. The 2.2-square-mile city was covered with oil derricks within a decade of the initial discovery, and according to CalGEM records, more than 300 individual wells were drilled within its boundaries.
Today, the derricks are gone and Signal Hill is a residential and commercial community surrounded by the City of Long Beach. But the petroleum deposits remain, along with hundreds of abandoned well bores that serve as vertical migration pathways for methane gas. The combination of extreme well density and persistent petroleum reserves makes Signal Hill one of the most challenging methane environments in Southern California.
Critically, Signal Hill does not fall under LADBS jurisdiction. The City of Long Beach Building Department enforces a separate methane code with different classification levels, testing requirements, and mitigation standards.
Signal Hill’s Oil Field Legacy
Well Density
With over 300 documented wells in 2.2 square miles, Signal Hill averages roughly 136 wells per square mile. By comparison, the Salt Lake Oil Field beneath Mid-Wilshire has approximately 15–20 wells per square mile. This extreme density means virtually every development parcel in Signal Hill is within 300 feet of at least one abandoned well — and many parcels have multiple wells directly beneath or adjacent to the property.
Current Well Status
According to CalGEM’s well tracking system, Signal Hill wells fall into several categories: properly plugged and abandoned (majority), idle (inactive but not plugged), and active (still producing or being used for injection). Even properly plugged wells can leak over time as cement seals degrade, creating low-rate but persistent gas migration. Idle and active wells present higher migration risk.
Gas Source Characteristics
Signal Hill’s methane is petrogenic — it originates from the petroleum deposit itself, not from biological decomposition. Petrogenic methane tends to produce higher concentration readings (ppmv) than biogenic methane and can carry trace amounts of other petroleum hydrocarbons. Testing in Signal Hill should be prepared for potentially high readings that may trigger the upper design level classifications under the Long Beach code.
Long Beach Jurisdiction — Not LADBS
This is the single most important regulatory distinction for Signal Hill projects: the City of Long Beach (which provides building department services for Signal Hill) enforces its own methane code under LBMC Section 18.79, not the LADBS methane code.
Key differences include:
Different classification system. Long Beach uses its own design level categories that do not map directly to LADBS Levels I–V. A site that would classify as Level III under LADBS may receive a different classification under Long Beach’s system.
Different testing protocols. While the general approach (soil gas probes, concentration and pressure measurement) is similar, the specific probe depths, sampling frequencies, and laboratory requirements may differ from LADBS standards.
Different mitigation standards. The required system components, material specifications, and installation standards under the Long Beach code have distinct differences from LADBS requirements. Engineers must be specifically familiar with the Long Beach code to design compliant systems.
Different plan-check process. The Long Beach Building Department conducts its own plan review with its own staff, correction procedures, and approval timeline. LADBS plan-check experience does not automatically translate to Long Beach familiarity.
Sway Features designs to both the LADBS and Long Beach methane codes and has submitted and received approval under both jurisdictions.
Typical Signal Hill Mitigation Costs
| Project Type | Classification | Estimated Mitigation Cost |
|---|---|---|
| Single-family home (slab-on-grade) | Low–moderate risk | $12,000–$25,000 |
| Single-family home (any foundation) | High risk | $25,000–$50,000 |
| Multi-family residential | Moderate–high risk | $50,000–$120,000 |
| Commercial building | Moderate–high risk | $60,000–$150,000 |
These ranges include design engineering, barrier installation, vent system, active components (where required), and inspection fees under the Long Beach code. Testing adds $6,000–$12,000 depending on lot size.
Signal Hill-Specific Considerations
Well Search Before Purchase
Any party considering purchasing development property in Signal Hill should conduct a CalGEM well search before closing. The presence of a well directly beneath a proposed building footprint can require well re-abandonment — a costly procedure ($50,000–$200,000+) that involves drilling into the existing well, removing the old plug, and installing a new cement seal to modern standards. This cost is separate from methane mitigation and can dramatically affect project feasibility.
Active Well Setbacks
Signal Hill still has several active and idle wells. The City and state regulations require minimum setback distances between active wells and occupied structures. These setbacks can limit buildable area on parcels near active operations.
Ongoing Monitoring
Given the extreme well density and persistent gas conditions, many Signal Hill projects require permanent monitoring systems with ongoing maintenance obligations. Annual costs of $1,500–$5,000 for sensor calibration, system testing, and compliance reporting are typical.
Summary
Signal Hill’s status as one of the world’s most densely drilled oil fields creates extreme methane mitigation conditions — with over 300 wells in 2.2 square miles, virtually every development parcel faces elevated gas migration risk. The Long Beach Building Department (not LADBS) has jurisdiction, applying its own methane code with different classification, testing, and mitigation standards. Budget $12,000–$150,000+ for methane mitigation depending on project type and risk classification, plus $6,000–$12,000 for testing. Conduct a CalGEM well search before purchasing any Signal Hill development property.
Frequently Asked Questions
Does Signal Hill follow the LADBS methane code?
No. Signal Hill falls under the City of Long Beach Building Department, which enforces LBMC Section 18.79. This is a separate code with different classification levels, testing protocols, and mitigation standards. Engineers designing for Signal Hill projects must be familiar with the Long Beach methane code specifically.
Is every Signal Hill property in a methane zone?
Signal Hill does not use the LADBS “methane zone” designation. The Long Beach code has its own trigger criteria based on proximity to oil operations and site-specific conditions. Given the density of wells throughout the city, most Signal Hill properties trigger methane requirements under the Long Beach code.
Can I use LADBS-approved plans in Signal Hill?
Plans approved by LADBS are not automatically accepted by the Long Beach Building Department. The plans must be designed to the Long Beach code’s specific requirements and submitted through Long Beach’s own plan-check process. Contact Sway Features for a consultation on Long Beach code compliance.
What if there is an abandoned well directly on my property?
A well directly on or immediately adjacent to your property may require re-abandonment before construction can proceed. Contact CalGEM to verify the well’s status and determine whether re-abandonment is required. This is a separate process from methane testing and mitigation.