In June 2015, the Post-Event Environmental Impact Assessments Report was published as part of the second phase of the strategy. The report was submitted by Golder Associates to the Mount Polley Mining Corporation to determine the physical, biological, and chemical implications 6–8 months after the dam breach. The report detailed steps taken by the MPMC to stabilize the tailings storage facility by creating two rock berms inside the facility, to provide safe access to Hazeltine creek by reducing the elevation of Polley Lake behind the point of the blockage caused by the discharge of tailings effluent, and to stop inputs from the tailings storage facility. Specialists and environmental scientists and engineers were hired to study the impact of the spill from the tailings dam. This team studied where tailings effluent was deposited on land and in surrounding water environments, in particular how the bottom of Quesnel Lake was affected and how the structures of Hazeltine and Edney creeks had changed. Chemical studies studied soil, water and sediment changes, while biological studies were focused on the effect of aquatic plant and animal life, in particular those at the sediment layer. Biological assessment also studied soil-dependent biota in the areas surrounding Quesnel Lake and Polley Lake.
The Assessments Report determined nine areas requiring ongoing monitoring to determine localized strategies for remediation efforts in each location. These areas included the tailings storage facility, the Polley plug (a blockage area between the tailings effluent and Polley Lake), Polley Lake, upper Hazeltine creek, Hazeltine Canyon, lower Hazeltine creek, the mouth of Edney creek, Quesnel Lake, and Quesnel River.
The report concluded that Polley Lake, Hazeltine Creek and a small portion of Quesnel Lake were physically affected by the tailings dam breach. The chemical testing on the tailings mixture was determined to be relatively inert though it was found that a higher concentration of copper was contained in the effluent compared to before the breach. Biological testing found copper contained within lake sediment and within the water was not toxic to aquatic life. Soil testing of copper levels determined a level higher than provincial standards for the protection of invertebrates and plants but at far lower levels than the provincial standards for the protection of human health. Deep water analysis found copper to be at levels below the Provincial Water Quality Guideline. Despite the levels of copper present due to presence in the tailings, the report determined it was unlikely to be released from the tailings and therefore adverse effects were deemed unlikely.
The restoration of the shoreline of Hazeltine creek began to create a stable water flow and to begin the restoration of fish and associated wildlife habitats. This was preceded by floodplain grading and the determination of the physical land characteristics of the areas surrounding the shoreline. A flow study to determine an ideal range and the annual mean for natural habitats was completed before construction of rock weirs and habitat features. Planting on the floodplain, to continue over subsequent years had also begun. Repairs to the mouth of lower Edney Creek was completed connecting the waterway to Quesnel Lake. By the spring of 2015, remediation work had installed a new fish habitat at lower Edney Creek. Successful spawning of interior Coho, Kokanee and Sockeye Salmon was accomplished. By May, a new channel for Hazeltine Creek was completed.
On 13 July 2015, Interior Health, the regional public health authority, declared all water restrictions lifted and determined water sourced from Polley Lake and Hazeltine Creek safe for consumption and recreation from a health perspective. A review of the water, sediment and fish toxicology samples from the Ministry of the Environment determined no known risks to human health.