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Sam Monaco -2 - 9 June 2017 Harvest-Lathrop Composting Facility ' CEQA would be finalized in "mid-April to accommodate one appellant." The Discharger in its Final Technical Report did not provide evidence that it had complied with CEQA requirements for the proposed 20-acre expansion. 2. Water uses for irrigation. The Discharger's water balance dated 10 April 2017 section 5.4 states that the Discharger may use detention pond wastewater for irrigation. The General Order does not have provisions allowing discharge of wastewater for irrigation purposes. Discharge of wastes to land can only be conducted under waste discharge requirements that are not specified in the General Order. 3. Invalid Water Balance Analysis. The General Order Attachment D-Technical Report Requirements C.2.d requires that if a detention pond is used, a water balance analysis must be performed demonstrating compliance with the Design, Construction, and Operation Requirements section of the General Order. General Order Specifications#5 requires that wastewater must be managed to prevent discharge. The Discharger's water balance analysis is invalid because it will not prevent discharge due to the proposed detention ponds having insufficient storage capacity during the wet season for the following reasons: a) Invalid compost area runoff coefficient. The Discharger's water balance dated 10 April 2017 uses a runoff coefficient of 0.6 for the compost areas discharging to detention ponds A and B. However, the Discharger states that the compost area consists of an area covered with compost windrows approximately 7 feet high, 18 feet wide, and 250 feet long as well as open aisle area 8 feet wide between the windrows. Composting using these specifications will mean 70% of the compost area will be covered with windrows and 30% will be open aisle area. The Discharger's consultant submitted a water balance analysis dated 17 February 2017 where the water balance used the weighted average method to determine a composited runoff coefficient for the compost area. Staff agrees that this is the appropriate method for determining the runoff coefficient using the Rational Method, and concurs with the recommended runoff coefficients for compost pads consisting of an asphalt surface is 0.85 for the open aisle spaces between windrows and a runoff coefficient between 0.50 and 0.70 for the windrows themselves'. However, the Discharger's 10 April 2017 water balance does not use a composited runoff coefficient for the compost area and therefore does not take into account higher runoff volumes from the compacted soil in the open aisle area. Furthermore, Caltrans Highway Design Manual, 6t" Edition, chapter 810, Hydrology, Topic 819.2(1), Estimating Design Discharge using the Rational Method states that when using runoff coefficients for storms with less than 5 or 10 year return frequencies, a frequency factor C(f) should be used to adjust runoff coefficients for increased runoff due to saturated near surface ground conditions. The Design Manual recommends multiplying runoff coefficients by 1.1, 1.2, and 1.25 for storms with 25 year, 50 year, and 100 year return frequencies, respectively. The Discharger should compensate for less frequent higher intensity storms where infiltration, detention, and other losses increase runoff. ' Kalaba, L., et al, "A Storm Water Runoff Model for Open Windrow Composting Sites," Compost Science& Utilization, Vol. 15, No. 3, p. 142-150. P AP1