AgdaPkt 2017-09-11 Closed and Joint SA PFA

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TA. - Page 39 LSA ASSOCIATES, INC. ROCKETSHIP REDWOOD CITY ELEMENTARY SCHOOL PROJECT SEPTEMBER 2016 INITIAL STUDY/MITIGATED NEGATIVE DECLARATION sufficient daylight in the building. The entire building would contain approximately 51 skylights and 12 solatubes;6 all learning spaces would include natural light with little need for supplemental electrical lighting. In addition,the existing interior concrete slab would be polished; eliminating the need for additional floor tile material and the existing wood trusses and roof joints would be exposed; eliminating the need for additional ceiling tile material. All toilets and urinals would be low-flow. 6. Demolition and Construction The existing metal storage shed on the south corner of the property and all existing pavements would be removed from the site. Construction debris,including 220 cubic yards of pavement,would be collected and off-hauled. A minimum of 50 percent of construction waste would be recycled. Grading is anticipated to be minimal and the maximum depth of excavation would be about 1 foot. Approximately 25 cubic yards of soil would be excavated for grading and utility trenching,all of which would be off-hauled. Project construction is anticipated to occur over a six-month period. Construction activities are anticipated to begin in January 2017 and to be complete in June 2017. The school is expected to be operational in time for the 2017/2018 school year. 7. Indoor Air Sampling and Mitigation Work Plan Subsurface investigations completed at the site have determined that volatile organic compounds (VOCs)in soil vapor and groundwater occur at concentrations above their respective screening levels. These chemicals occur near the northeast corner of the building and are considered chemicals of potential concern(refer to Section VIII,Hazards and Hazardous Materials for more information). As previously described,DTSC recently approved an Indoor Air Sampling and Mitigation Work Plan (Work Plan, see Appendix A).7,"This Work Plan is being implemented under DTSC oversight to mitigate potential impacts to indoor air quality associated with these conditions.As part of the remediation program,the property owner and project applicant installed a passive sub-slab depressur- ization system designed to continuously create a lower pressure directly underneath the building floor relative to the pressure within the building. The resulting sub-slab negative pressure is intended to eliminate the exposure pathway between the contaminated soil vapor and indoor air sensitive receptors and inhibit soil gases from flowing into the building,thereby ensuring that indoor air concentrations of VOCs related to the underlying subsurface conditions are reduced to an acceptable level. It is possible that the passive system will not fully achieve this objective and that the system may need to be converted to an"active" system(this determination will be made under DTSC oversight based on the ongoing sampling of indoor air quality). Since potential CEQA environmental impacts could be greater with an active system,this Initial Study conservatively assumes the operation and maintenance of an active system. Therefore,individual components of both the existing passive system and the active system that could be installed at the site are described below. 6 Modular lighting systems that improve the way daylight is captured and delivered to interior spaces. 7 Department of Toxic Substances Control,2016,op.cit. 8 The Source Group,2016,op.cit. P:1RWC1401B Rocketship Sch-I\PRODUCrSUS-MND1Pu61ic1Ra ketship Public Review 09-29-16.docx(09/29/16)PUBLIC REVIEW DRAFT 15 ATTY/RESO.0084/CC RESO ADOPTING CEQA-ROCKETSHIP CHARTER SCHOOL APPEAL REV:09-05-17 VR Page 23 of 124