SITE INFORMATION AND CORRESPONDENCE CASE 2

Home Browse Search

Messrs. Silva and Gilton - 2 - 28 February 2007 Please address the following items: 1. The workplan uses different names for the land application areas and recycled water storage ponds. Please revise all references so that they are consistent with the nomenclature used in the WDRs. 2. Please submit a revised Plate 1 that presents the proposed well locations. Please address the following comments: i. We understand that you may request changing the location of Basin No. 4 to the northwest portion of the development. As described above, moving the basin may be allowed as part of the hearing for any flow rate increase over 55,000 gallons per day (gpd). It may also result in the need for additional groundwater monitoring wells. ii. The monitoring network needs to compare groundwater upgradient of the land application areas with groundwater under or downgradient of the land application areas. Please revise Plate No. 1 accordingly. iii. Wastewater ponds always require groundwater monitoring wells. Please locate groundwater monitoring wells intended to specifically monitor wastewater ponds within 50-feet of the ponds. iv. Because groundwater flow directions are uncertain, and may change with the San Joaquin River stage, more than one background groundwater quality well may be appropriate. v. If groundwater flow directions are different than anticipated, additional groundwater monitoring wells may be required. vi. The proposed well located at the southeast corner of the development appears to be located on the neighboring property. Please clarify that location. 3. Please describe how groundwater TDS concentrations will be determined in all areas proposed for wastewater application. You may elect to only investigate Phase I land application areas (Nos. 1, 2, and 3) or investigate any number of land application areas. 4. With regard to the well construction, please address the following issues.- i. ssues:i. The proposed well construction includes a 15-feet long screen and a 3.5-feet long sanitary seal. This arrangement does not maximize the sanitary seal. Consider using a 10-feet long well screen to increase the depth of sanitary seal. This may be an important issue considering the sandy nature of the native soils and the historic detections of bacteria in site wells. ii. Because this hydrogeologic investigation is not concerned with the presence of floating non-aqueous phase liquids (such as gasoline), it is not critical that the screen interval intersect the air-water interface. Consider constructing the wells slightly deeper to maximize the sanitary seal. iii. The well casing bottom plug is not described; please use a threaded cap for the bottom of the well casing or secure a slip cap with stainless steel screws. Please submit a revised Figure 6 showing the change. iv. The disinfection procedure described in the workplan is generally acceptable; however, a list of wells to be disinfected was not provided. Finding No. 51 in the W\StaMObriennSan Joaquin\Oakx o d_Lake\Silva 20 Feb 07 doc