Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_name_68 (elevation_groundstation INTEGER, slope_length VARCHAR, capacity_in_persons_hour VARCHAR, name_or_route VARCHAR)

### Question ###
Which elevation groundstation has a capacity in persons/hour larger than 820, and a Name or route of lager 1, and a slope length smaller than 336?

### Accurate SQL ###

SELECT AVG(elevation_groundstation) FROM table_name_68 WHERE capacity_in_persons_hour > 820 AND name_or_route = "lager 1" AND slope_length < 336