CORRESPONDENCE_2017-2018 - Laserfiche WebLink

Home Browse Search

. s Sam Monaco - 3 - 9 June 2017 Harvest-Lathrop Composting Facility b) Native area (Acres) sizing not supportable. The Discharger's water balance dated 10 April 2017 identifies 1.0 acres of native area draining to detention pond A and 2.7 acres of native area draining to detention pond B, both having a runoff coefficient of 0.3. However, construction drawing Grading and Drainage Plan (sheet 3) does not support the reported areas. The Discharger's water balance states that the pond A surface area is 83,600 sq. ft. (1.9 acres) and pond B surface area is 66,696 sq. ft. (1.5 acres). However the Grading and Drainage plan does not show native area draining to pond A and B amounting to anything close to that shown for the surface area of the ponds. Properly determining the size of the native area is crucial in the water balance since the native area uses a low runoff coefficient (0.3) and this area is used in calculating a weighted average runoff coefficient for the entire area draining into pond A (0.62) and pond B (0.60). c) Wet days per month (usage days). The Discharger's water balance dated 10 April 2017 identifies in column 8 the number of days per month that the Discharger will apply detention pond wastewater to compost windrows for operational use as well as for dust control. The Discharger's Water Balance Analysis section 5.2 determined the number of days where wastewater could be applied for operational use and dust control using historical data which provided the average number of days where precipitation was equal to or greater than 0.01 inches. The Discharger used the criteria of rainfall less than 0.01 inches to determine when wastewater could be beneficially reused. The Discharger proposes that during the wet season (November through April) 21 days per month will have favorable conditions where wastewater can be beneficially reused (i.e., not removed for waste disposal purposes). However, using average number of days per month during an average wet season when the water balance is based on the wettest year is incorrect. The Discharger should use the number of days available during the wettest year. Stockton Metropolitan Airport (KSCK) rainfall data obtained from https://www.wunderground.com/ reports a total of 18.25 inches for the 2016-2017 wet season from November through April which approaches the wettest year precipitation total reported in the Discharger's water balance (21.1 inches). During that period, KSCK reported 9,10,17,16, 9, and 10 days equal to or greater than 0.01 inches from November through April, respectively. In December there were 10 days, in January there were 17 days, and in February there were 16 days. During these months, the opportunity to use wastewater for operational and dust control purposes is very limited. d) Operational Use. The Discharger's water balance estimates that 30,000 gallons of wastewater will be removed daily from pond A for operational use in accelerating decomposition of organic matter in the compost windrows and 20,000 gallons will be removed daily from pond B. As stated in paragraph 3c above, the Discharger estimates that during 21 days per month through the wet season, the compost windrows will need additional water to accelerate the decomposition process. Based on 70% of the working area covered with compost material in windrows (see paragraph 3a above), the windrow area discharging to pond A is 12.46 acres and the windrow area discharging to pond B is 6.16 acres: The application of 30,000 gallons to 12.46 acres amounts to 4,010 cubic feet of wastewater applied to 12.46 acres per day or 0.007 inches of wastewater applied over 542,757 ft2 of area. As stated in paragraph 3c above, in December there were 10 days, in January there were 17 days, and in February there were 16 days where rainfall totals exceeded 0.007 inches. During these months, the opportunity to use wastewater for operational use is unnecessary. The same calculations can be made for the water needs 3r1IA°'