This is a steep jump in the minimum wage, which will in turn hurt the job growth in the city. It is yet to be seen to what extent the job growth rate will be affected by this change, but it will most definitely be hurt to some extent. It will probably only be hurt by a small amount, though.
An employee is only worth what an employer is willing to pay them for their labor. Entry level workers with low skills may not be worth paying $15-an-hour for minimum wage. For example, many jobs have become automated by machines that can replace human workers, like bank tellers and cashiers. If the cost of labor becomes more expensive than just buying a machine to do the job, then employers will simply replace workers with machines that can do the job for less money.
A $15-an-hour minimum wage bill will hurt DC job growth in the city. It is a matter of common sense. Labor is the largest employer expenditure by far. Does anyone really expect an employer to eat the cost of an increased wage? Of course not. It will be passed on in the form of higher prices, which leads to less demand, which leads to less jobs.
Increasing the minimum wage, not only in Washington DC, offers a great boost for the economy. In a consumer-driven economy, the more money people have to spend, the more that businesses stand to earn. Raising minimum wage puts more money out there for increased spending, which benefits individuals and businesses alike.