|22 November 2001|
Executive Summary of the report produced by Environmental Scientists, Montgomery Watson Harza
Lyn Christie Place Site Investigation, November 2001
MWH Ltd carried out an initial site investigation of Lyn Christie Place in August 2001. This involved a structural assessment of two vacant units, the installation of two landfill gas wells and some limited soil sampling.
Trace concentrations of landfill gas (LFG) were detected in the subsurface of the property
The soil samples identified elevated levels of polycyclic aromatic hydrocarbons (PAHs) and associated heavy metals above the values presented in the Guidelines for Assessing and Managing Contaminated Gasworks Sites. Of particular concern is benzo[a]pyrene (BAP).
Additional soil samples were collected in September and October confirming the presence of BAP at concentrations that exceed the relevant guidelines.
Each housing unit was sampled for the presence of LFG however any detectable concentrations did not present a health and safety risk to residents.
Structural assessments of each housing unit showed that settlement issues are continuing. The degree of damage being caused is variable from unit to unit however there are no health and safety concerns.
Two designated groundwater monitoring wells were installed on the property for the purpose of assessing groundwater quality.
Groundwater flow direction is variable within the unconfined shallow aquifer at Lyn Christie Place.
Water quality sampling results have identified elevated arsenic, ammonia, manganese, iron and boron when compared to the Drinking Water Standards for New Zealand (2000). However, the concentrations detected in the groundwater below Lyn Christie Place do not pose a risk to human health given that the local water supply is derived from the Citys reticulated drinking water system, which originates from deeper bores.
Remedial action has been recommended that will minimise/eliminate contaminant exposure pathways available to residents at Lyn Christie Place.
The preferred remedial options to deal with the elevated concentrations of soil contaminants and structural damage include: 1) striping and replacing with clean material designated areas of soil that will minimise the exposure pathways to residents and 2) to inject resins that will raise the floor of each unit and restrict damage from settling.
Montgomery Watson Harza Ltd