City and school officials drilled down on details of the proposed renovations at four elementary schools in Portland on Tuesday night as they weigh whether to put a $70 million bond out to voters for the fixes. Architect Tyler Barter of Oak Point Associates walked the School Facilities Ad Hoc Committee through the latest plans for Presumpscot, Longfellow, Lyseth and Reiche elementary schools, which the committee toured in recent weeks. Barter pointed out that at the schools – all 40 to 60 years old – replacing aging plumbing and electric systems is a significant cost in addition to new construction. “It’s most important to explain the learning needs,” Superintendent Xavier Botana said, joining Barter at the podium to address the committee.