Not a problem at all, sure, if optimal lean muscle mass is your goal or just a ripping good looking body figure physique, then i would not recommend doing 11km twice a week for an extended period of time.
But and this is important, doing it for a few month´s a year wont keep you from getting lean and improving in the gym too. It´s as anything in life also about what we enjoy, and since you do like it - keep doing it.
Not saying it´s bad doing it all year round, just that it would not be the optimal thing to do since that kind of cardio is counterproductive to improving lean muscle mass and strength. Hiit, as you know is a better sidekick.
But, doing it twice a week for the spring/summer is all fine, i do alot more cardio during summer and spring too and longer walks and jogs is an almost daily part of my life during that period of the year, while i at winter, do Hiit after pumping weights, short, high intense 2km interval sprints on the cross trainer. + once or twice a week martial arts.
It all really depends on where you are at today in your physique and your goals and i certainly myself, think that stamina is part of a well trained and fit physique too.
You should not worry about it tho, keep on doing it as long as you enjoy those 11km runs and aslong as it´s just twice a week, not an issue, unless you start to feel drained of energy in the gym and start noticing your strength and form in the mirror getting worse.
With that said tho, to keep it real and crass.
- anyone running 11km twice a week, will during that time period, most likely have a very hard time increasing strength and lean muscle mass (possible to do tho if you are really extreme about your training and food and have prime genes). Keeping it is possible for most tho and you´ll certainly gain stamina and loose some body fat, but most people would get a better result from combining that weight lifting with hiit based cardio.