Huddersfield Gas Works

The former Huddersfield Gas Manufacturing Works is located to the northeast of the town centre and covers an area of 3.2 hectares. Gas had been manufactured on the site since 1821 until it was decommissioned in 1972. Site investigations had identified contamination to soils and groundwater by gas production by-products including poly-aromatic hydrocarbons (PAHs) ammonia, spent iron oxide, aliphatic and aromatic hydrocarbons, and toxic metals. VHE undertook the remediation as part of the framework agreement with National Grid Property. The works were carried out over a rolling 42 week phased programme of enabling/demolition, site investigation, design and on site treatment and disposal of segregated wastes.

To maximise the reuse of existing site materials a targeted phase of de-watering of perched water was undertaken commencing with the deepest areas of excavation within retained underground structures. This exercise produced a volume of over 5,000m³ of hydrocarbon contaminated waters which were pumped into a bespoke tank farm with primary and secondary settlement of suspended solids being enhanced by the addition of flocculants. In addition, the water treatment plant comprised sand and carbon filters with an air stripping tower operated on a semi-automatic basis, discharging direct to foul sewer under an authorised consent.

Following initial dewatering, careful segregated excavation of over 60,000m³ of material was carried out, including 11,000m³ of tar impacted soils. This was sentenced for further bio-physical treatment, including moisture modification by controlled addition of lime, screening and bio-remediation of material with suitable characteristics. Segregation works included sample screening every 200m³ of excavated material for asbestos. Any asbestos containing materials were subsequently classified and treated or disposed of following a quantitative assessment. Approximately 90% of all excavated material was re-used on site following appropriate treatment in congested and varying conditions. Works were undertaken under the constant scrutiny of both the EA and EHO who have both expressed satisfaction , in particular with the management and control of odours, vapours and dust on a site with a sensitive receptor as a neighbour.

During the works additional minor civil engineering works were undertaken including reinstatement of existing drainage pipe work and hand demolition/dismantling and re-building of sections of the existing masonry boundary wall.