CREATE TABLE table_18600760_15 (water__sqmi_ VARCHAR(255), county VARCHAR(255), geo_id VARCHAR(255))
How many square miles of water is in Ramsey County with a geo id larger than 3807159460.0?
    
SQL: SELECT water__sqmi_ FROM table_18600760_15 WHERE county = "Ramsey" AND geo_id > 3807159460.0