With retirement impending, one of Nevada County’s most important officials reflected on his eventful tenure in an institution that has been dramatically altered due to severe economic hardship in the middle of the last decade. Joe Christoffel’s official title is Nevada County Deputy County Executive Officer. But in reality, Christoffel is the county’s chief financial officer. Initially coming on the county payroll in 2002, Christoffel is set to retire in June. He has steered the county’s largest employer — with more than 770 employees and a budget of $180 million — through one of the most tumultuous economic periods in …