OAR 340-150-0465
Interstitial Monitoring Release Detection Method

(1)

An owner and permittee may use an interstitial monitoring system as a release detection method if:

(a)

The system is designed, constructed and installed in accordance with a national code of practice or industry standard and the interstitial monitoring system is an approved leak detection system (method and equipment) for that system as listed by a national organization (e.g., the National Work Group on Leak Detection); and

(b)

The system is able to detect a leak from any portion of an UST or underground piping that routinely contains a regulated substance.

(2)

An owner and permittee must meet the following requirements for the specific type of UST system or piping:

(a)

Multiwalled UST systems. The sampling or testing method must be able to detect a release through the inner wall in any portion of the UST.

(b)

UST systems with a secondary barrier within the excavation zone. The sampling or testing method used must be able to detect a liquid between the UST system and the secondary barrier.

(A)

The secondary barrier around or beneath the UST system must consist of artificially constructed material that is sufficiently thick and impermeable (at least 10-6 cm/sec for the regulated substance stored) to direct a liquid to the monitoring point to allow its detection;

(B)

The secondary barrier must be compatible with the regulated substance stored so that a liquid from the UST system will not cause a deterioration of the barrier or allow a release to pass through the barrier;

(C)

For USTs with corrosion protection, the secondary barrier must be installed so that it does not interfere with the proper operation of the corrosion protection system;

(D)

Groundwater, soil moisture or rainfall cannot render the testing or sampling method used inoperative so that a release could go undetected for more than 30 days or one day if used for pressurized underground piping;

(E)

Before installation, an owner and permittee must have the site assessed to demonstrate that the secondary barrier is always above the seasonal high groundwater level and not in a 25-year flood plain, unless the barrier and monitoring system are designed for use under such conditions; and

(F)

An owner and permittee must mark and secure monitoring wells at all times to prevent unauthorized access and tampering.

(c)

USTs with an internally fitted liner. An automated device must be able to detect a release between the inner wall of the UST and the liner, and the liner must be compatible with the regulated substance stored.

(d)

Double walled pressurized piping. Interstitial monitoring devices must be installed in any sump unless the piping is continuously double-walled through the sump.

(3)

An owner and permittee must monitor the UST and underground suction piping for a leak at least every 30 days and record the results for each month.

(4)

An owner and permittee must monitor pressurized underground piping for a leak at least every 30 days and record the results for each month.

(5)

Beginning October 1, 2020, owners and permittees must follow OAR 340-150-0310 (Spill and Overfill Prevention Equipment and Testing Requirements)(8) to ensure that containment sumps used for interstitial monitoring of piping are operating properly and will prevent releases to the environment.

(6)

An owner and permittee must retain at a minimum the most current 12 consecutive months of release detection records. Records must include, at a minimum, the date the system was checked, observations made and the name or initials of the person conducting the monitoring. In addition, records for electronic systems must include: power status (on or off), alarm indication status (yes or no) and sensor malfunction noted (yes or no).

(7)

An owner and permittee must report to DEQ any leak test observations, alarms or results indicating the possibility of a release to the interstitial area within 24 hours as a suspected release (OAR 340-150-0500 (Reporting Suspected Releases)) and immediately begin investigation in accordance with 340-150-0510 (Suspected Release Investigation and Confirmation Steps).

Source: Rule 340-150-0465 — Interstitial Monitoring Release Detection Method, https://secure.­sos.­state.­or.­us/oard/view.­action?ruleNumber=340-150-0465.

340‑150‑0001
Purpose and Scope 340‑150‑0006
Applicability and General Requirements 340‑150‑0008
Exemptions and Deferrals 340‑150‑0010
Definitions 340‑150‑0020
UST General Permit Registration Certificate Required 340‑150‑0021
Termination of Temporary Permits 340‑150‑0052
Modification of Registration Certificates For Changes in Ownership and Permittee 340‑150‑0080
Denial, Suspension or Revocation of General Permit Registration Certificates 340‑150‑0102
Termination of General Permit Registration Certificates for Installation, Operation and Temporary Closure 340‑150‑0110
UST General Permit Registration, Annual Compliance and Other Fees 340‑150‑0135
General Requirements for Owners and Permittees 340‑150‑0137
UST Systems with Field-Constructed Tanks and Airport Hydrant Fuel Distribution Systems 340‑150‑0140
Requirements for Sellers of USTs 340‑150‑0150
Depositing Regulated Substances in USTs 340‑150‑0152
Requirements for Distributors of Regulated Substances for Deposit into USTs 340‑150‑0156
Performance of UST Services by Owners or Permittees 340‑150‑0160
General Permit Requirements for Installing an UST System 340‑150‑0163
General Permit Requirements for Operating an UST System 340‑150‑0167
General Permit Requirements for Temporary Closure of an UST System 340‑150‑0168
General Permit Requirements for Decommissioning an UST System by Permanent Closure or Change-in-Service 340‑150‑0180
Site Assessment Requirements 340‑150‑0200
Training Requirements for UST System Operators and Emergency Response Information 340‑150‑0210
Training Requirements for UST Operators 340‑150‑0250
Expedited Enforcement Process 340‑150‑0302
Installation of Used USTs 340‑150‑0310
Spill and Overfill Prevention Equipment and Testing Requirements 340‑150‑0315
Periodic operation and maintenance walkthrough inspections 340‑150‑0320
Corrosion Protection Performance Standards for USTs and Piping 340‑150‑0325
Operation and Maintenance of Corrosion Protection 340‑150‑0350
UST System Repairs 340‑150‑0352
UST System Modifications and Additions 340‑150‑0354
UST System Replacements 340‑150‑0360
Requirements for Internally Lined USTs 340‑150‑0400
General Release Detection Requirements for Petroleum UST Systems 340‑150‑0410
Release Detection Requirements and Methods for Underground Piping 340‑150‑0420
Release Detection Requirements for Hazardous Substance UST Systems 340‑150‑0430
Inventory Control Method of Release Detection 340‑150‑0435
Statistical Inventory Reconciliation Method of Release Detection 340‑150‑0440
Manual Tank Gauging Release Detection Method 340‑150‑0445
Tank Tightness Testing for Release Detection and Investigation 340‑150‑0450
Automatic Tank Gauging Release Detection Method 340‑150‑0465
Interstitial Monitoring Release Detection Method 340‑150‑0470
Other Methods of Release Detection 340‑150‑0500
Reporting Suspected Releases 340‑150‑0510
Suspected Release Investigation and Confirmation Steps 340‑150‑0520
Investigation Due to Off Site Impacts 340‑150‑0540
Applicability to Previously Closed UST Systems 340‑150‑0550
Definitions for OAR 340-150-0555 and 340-150-0560 340‑150‑0555
Compliance Dates for USTs and Piping 340‑150‑0560
Upgrading Requirements for Existing UST Systems 340‑150‑0600
Delegation of Program Administration 340‑150‑0620
Approval of More Stringent Performance Standards
Last Updated

Jun. 8, 2021

Rule 340-150-0465’s source at or​.us