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Bob Hall - Pinehaven Hydrology – ADDENDUM A

In his calculations for Pinehaven hydrology, Bob Hall relied on on-site infiltration tests by Alex Ross which differ significantly from desktop infiltration rates in Cardno’s map for the Pinehaven area. For comparison, Hall re-did his calculations (see R J Hall - ADDENDUM A) using Cardno’s questionable rates yet still found a doubling of runoff from the SKM / Jacobs ‘future development scenarios’ on the Pinehaven hills, not 1% as asserted in the work by SKM, Jacobs and Beca.

G Macky’s review states, “Regardless of which model results are preferred [five-fold increase in runoff using Alex Ross’s infiltration rates, or two-fold increase using the Cardno map] the increase in runoff [from the SKM / Jacobs ‘future development scenarios’ on the Pinehaven hills] is significant …”, and not 1% as claimed by SKM, Jacobs and Beca. Bob Hall concluded there are “substantive discrepancies” in the Pinehaven flood model and flood maps, and that “the flood modelling … should be … corrected before any reliance is placed upon it as the baseline modelling for assessing post-development runoff of future Guildford development in the upper Pinehaven catchment.”

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