Salt-Affected Wellsite Closure Project, Background Report

Millennium EMS Solutions Ltd.

November 2015

Executive Summary

Introduction

There are a large number of oil & gas sites with salts in soil that exceed one or more generic guideline values. The nature of generic guidelines is that, by definition, they do not uniquely consider site specific conditions and therefore may indicate the potential for an adverse effect when in actuality there is no such potential. Undertaking remedial activities where no potential for adverse effect exists will result in a negative net environmental benefit. Given these concerns, an alternative method of managing such sites is needed. Petroleum Technology Alliance Canada (PTAC) has initiated a project to look for solutions to these issues for all relevant exposure pathways and land uses. The current document reports specifically on issues relating to the ecological direct contact exposure pathway (growth and reproduction of plants and soil invertebrates) in native grasslands areas of Alberta, and develops an Alternate Closure Protocol to identify sites which have no current, and no likely future adverse effects on native grassland ecosystems.

Approach

The approach taken in this document has two main steps:

Identify sites with no current adverse effects on native grassland ecosystems. This was achieved via application of the criteria in the ESRD Reclamation Criteria for Wellsites and Associated Facilities for Native Grasslands, supported by additional research into the rooting depth of native grassland species.
Identify sites with no likely future adverse effects on native grassland ecosystems. This was achieved by developing several possible options for determining whether site conditions make future upwards movement of salts from deeper soil horizons into the root zone unlikely. If future upwards movement of salts is unlikely, then future adverse effect on native grassland ecosystems is also unlikely.

Each of the two steps was supported by a compilation of relevant information available in the literature. The second step was additionally supported by a regional modelling study which determined an indicator depth for the water table for three representative soil types and for seven representative locations distributed around the grasslands region of Southern Alberta. In this context, an indicator depth for the water table was defined as the shallowest water table depth that is not predicted to result in the potential for long-term upward movement of moisture and corresponding upward movement of salts.

Protocol

An Alternate Closure Protocol was developed and is provided as Section 6 of this document. The Protocol indicates how a proponent can demonstrate no current and no likely future adverse effects on native grassland ecosystems. Lack of current adverse effects is demonstrated by meeting specified criteria from the Reclamation Criteria for Wellsites and Associated Facilities for Native Grasslands. Lack of likely future adverse effects is demonstrated by complying with one of several optional methodologies demonstrating that future upwards migration of salts is unlikely.

The Alternate Closure Protocol developed in this document addresses the ecological direct contact exposure pathway, but does not address other relevant exposure pathways including the protection of domestic use aquifers, protection of freshwater aquatic life, and protection of livestock watering. Achieving closure of a site requires demonstrating a lack of current and likely future adverse effects via all relevant exposure pathways. Future related PTAC initiatives may seek streamlined methodologies to demonstrate no current or likely future adverse effect via other exposure pathways. In the meantime, existing or alternate tools for addressing these other exposure pathways are available and are summarized in this document.