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HomeMy WebLinkAboutMOPS_InspRpt_2022CENTRAL VALLEY REGIONAL WATER QUALITY CONTROL BOARD INSPECTION REPORT 26 January 2023 DISCHARGER/LAND OWNER: Butte County Service Area 141, Mountain Oaks Properties, Inc., APNs 041-030-115, 041-047-093 FACILITY: Butte CSA No. 141, Messilla Valley Road CONTACT(S): Patrice Sorenson, Operator, Hydrotec Solutions INSPECTION DATE(S): 28 September 2022 INSPECTED BY: Josh Smith, Engineering Geologist, David Durette, Senior Water Resources Control Engineer, Central Valley Water Board CONSENT/WARRANT: Patrice Sorenson, Operator, Hydrotec Solutions CIWQS INSPECTION ID: 50121176 WDID: 5A040121001 WDR ORDER NUMBER: R5-2014-0153-DWQ-R5222 BACKGROUND The Butte County Service Area (CSA) No. 141’s wastewater treatment system (Facility) is located on Messilla Valley Road on property owned by Mountain Oaks Properties, Inc. (MOPS). The Facility is regulated by the Central Valley Regional Water Quality Control Board (Central Valley Water Board) under Waste Discharge Requirements (WDR) Order 2014-0153-DWQ-R5222. The Facility was re-enrolled in these WDRs in 2017 and was previously enrolled in WDR Order 93-206. In August 2022, Hydrotec Solutions staff, the Facility operator, contacted Central Vallely Waterboard staff regarding some anomalies in the monitoring and reporting result at the Facility. Those anomalies consisted of problems with the ground water monitoring well network at the site, particularly, ground water elevation above the elevation of the associated pond and unexpected fecal coliform results in the ground water laboratory testing. It was decided that a site visit would be helpful to familiarize new Water Board staff with the site and to go over issues. Mountain Oaks Properties Page 2 26 January 2023 The Mountain Oaks subdivision is designed for 54 lots and currently serves 49 homes. The Limesaddle Ridge Homeowners’ Association (HOA) was responsible for maintenance and operations of the wastewater treatment system until 2015 when the HOA hired Hydrotec Solutions, Inc. to repair and upgrade the treatment system as well as oversee operations, monitoring and reporting. Central Valley Water Board staff’s case file review for the years 2006 through 2022 showed quarterly pond monitoring for freeboard and berm maintenance requirements and semiannual monitoring for groundwater quality, in accordance with the WDR. The Discharger reported two leaks in September 2015 followed by major system repairs and submittal of an engineer’s report, dated 18 March 2016. In May 2018 the wastewater treatment system was reconfigured, replacing the gravel filter with two Orenco brand textile treatment tanks/pods. The textile pods decreased the footprint of the treatment system from the previous gravel bed treatment and are designed to increase the effectiveness of the filtration process. Since 2018 the system has operated with no issue. The facility has a network of three monitoring well that extend to a depth of 15 feet below ground surface (bgs) with groundwater depths typically less than 10 feet below ground surface. Groundwater monitoring data indicate that shallow groundwater has contained Total Coliforms (TC) in exceedance of the permitted most probable number limit of 2.2/100 ml. The pond and treatment system are fenced, but adjacent land is used for cattle grazing, which likely is a source of TC in shallow groundwater. The WDR does not require regular effluent monitoring, but effluent testing may be required for WDR permit renewal to demonstrate that wastewater is disinfected prior to discharge to the infiltration pond. SITE DESCRIPTION The system consists of a singular septic tank for each residence in the HOA subdivision, septic tanks discharge into neighborhood wide collection system which coalesce into a 2,900ft long gravity pipeline. The pipeline discharges effluent by to the treatment and disposal area, which consists of the two Orenco treatment pods a chlorination tank and system and 13.6 acre-foot unlined evaporation/infiltration pond. Treated effluent can be discharged to a spray field area if needed to maintain pond capacity. Three (3) ground water monitoring wells exist around the discharge pond area. The treatment system is equipped with an alarm system and back up power generator. INSPECTION OBSERVATIONS Central Valley Water Board staff arrived at the site at 11 a.m. and met with Patrice Sorenson and other Hydrotec Solutions staff, the Operator. The weather was sunny with clear skies and warm temperatures, approximately 75 F. Patrice Sorenson gave consent for the site inspection and collection of photographs. Central Valley Water Board staff began the investigation at the wastewater treatment system and holding pond. The treatment system consists of a valve box where Mountain Oaks Properties Page 3 26 January 2023 wastewater flow is directed either to the north Orenco treatment tank or the south treatment tank (Photo 6). From there wastewater passes to a dosing tank and contact chamber. A gravity flow line equipped with a flow meter; above grade (Photo 7) discharges the treated water to the holding pond. Vegetation along the north berm is prominent and requires intermittent removal and the surface of the pond is covered with floating algae/vegetation (Photo 4). The irrigation system for two land application areas, located to the northeast and northwest of the treatment system area. Brow ditches upgradient of the treatment system convey offsite surface seepage water around the treatment system area toward an ephemeral drainage basin located south-southeast of the treatment system area. The drainage has a blackberry bramble located above the seasonal stream but below the southernmost monitoring well (Photo 14). The Facility has a groundwater monitoring well network consisting of three groundwater monitoring wells, each approximately 15 feet deep. Monitoring well 1 is on the northwest side of the pond and monitoring wells 2 and 3 are located south of the pond near an ephemeral drainage (Photos 3, 11 and 12). The pond and treatment system is fenced, but the irrigation areas and surrounding land is used for cattle grazing. Staff left the site around noon. FOLLOW-UP If shallow groundwater contains TC, the Discharger will need to show that the treatment system is effective in protecting groundwater. Either treated effluent can be sampled prior to discharge to the pond and shown to be free of TC and containing small concentrations of residual chlorine, or deeper groundwater monitoring wells can be installed to determine the presence and quality of deeper groundwater zones. SUMMARY Based on the inspection findings, the Facility appeared to be generally well-maintained and operated as designed. The Orenco system improvements appear to be sufficient for future operations. Mountain Oaks Properties Page 4 26 January 2023 Recent monitoring reports, however, show Total Coliforms in shallow groundwater at concentrations exceeding permitted levels. The Central Valley Water Board may require further analysis of treatment system effectiveness, groundwater sampling procedures, or deeper groundwater quality. Inspector _____________________________________ Josh Smith, P.G. Engineering Geologist Reviewer _____________________________________ David Durette Senior Water Resources Control Engineer Attachments: Appendix A – Inspection Photographs 1-10