A 10 ha site is scheduled for re-development into a low density residential housing estate. The area is currently turfed. Soil tests on samples reveal that the soil on average contains 25% clay, 10% silt, the rest, sand and 0.5% organic matter. The flow length is estimated to be 200m with an average slope of 2.5%. Erosion control practice limits erosion from 30% of the surface area only (ie no erosion occurs from 70% of the surface), and erodible areas are well compacted. Assuming that the specific energy proposed by Wischmeier and Smith (1974) is applicable, for the construction phase:
(i) Plot the pollutograph of solids runoff from the site and estimate the maximum solids concentration (g/L) for runoff from the site.
(ii) Estimate total mass of solids (kg) mobilised from the site during and after construction for the same storm event