Environmental Matters (Tables)

12 Months Ended

Dec. 31, 2018

Environmental Remediation Obligations [Abstract]

Schedule of Environmental Loss Contingencies by Site

The following table summarizes information regarding liabilities related to environmental sites, which are recorded in other current liabilities and other noncurrent liabilities in NW Natural's balance sheet at December 31:



	Current Liabilities				Non-Current Liabilities
In thousands	2018		2017		2018		2017
Portland Harbor site:
Gasco/Siltronic Sediments	$	5,117	$	2,683	$	44,351	$	45,346
Other Portland Harbor	2,600		1,949		6,273		4,163
Gasco/Siltronic Upland site	13,983		13,422		44,830		47,835
Central Service Center site	10		25		—		—
Front Street site	11,402		1,009		3		10,757
Oregon Steel Mills	—		—		179		179
Total	$	33,112	$	19,088	$	95,636	$	108,280

Environmental Regulatory Table

The following table presents information regarding the total regulatory asset deferred as of December 31:



In thousands	2018			2017
Deferred costs and interest ⁽¹⁾	$	41,883		$	45,546
Accrued site liabilities ⁽²⁾	128,369			126,950
Insurance proceeds and interest	(88,502		)	(94,170		)
Total regulatory asset deferral⁽¹⁾	$	81,750		$	78,326
Current regulatory assets⁽³⁾	5,601			6,198
Long-term regulatory assets⁽³⁾	76,149			72,128


⁽¹⁾	Includes pre-review and post-review deferred costs, amounts currently in amortization, and interest, net of amounts collected from customers.


⁽²⁾	Excludes 3.32% of the Front Street site liability, or $0.4 million in 2018 and $0.4 million in 2017, as the OPUC only allows recovery of 96.68% of costs for those sites allocable to Oregon, including those that historically served only Oregon customers.

⁽³⁾

Environmental costs relate to specific sites approved for regulatory deferral by the OPUC and WUTC. In Oregon, NW Natural earns a carrying charge on cash amounts paid, whereas amounts accrued but not yet paid do not earn a carrying charge until expended. NW Natural also accrues a carrying charge on insurance proceeds for amounts owed to customers. In Washington, a carrying charge related to deferred amounts will be determined in a future proceeding. Current environmental costs represent remediation costs management expects to collect from customers in the next 12 months. Amounts included in this estimate are still subject to a prudence and earnings test review by the OPUC and do not include the $5.0 million tariff rider. The amounts allocable to Oregon are recoverable through NGD rates, subject to an earnings test.