NORTON — Shayne Fields spends his days this summer between planning ways to expand the city’s recreational trail network and actually building those trails. As Norton’s trails coordinator, Fields is responsible for expanding and maintaining the city’s system of more than nine miles of trails ranging from Legion Park and the Flag Rock Recreation Area up to the city reservoir. Fields said the current city trail map shows 9.1 miles of hiking and biking trails, but that will be growing this year.