I will have a nine hour layover at Capital airport, is there somewhere to shower and possibly sleep?

Yes, there are hourly lounges available in every terminal building. You can sleep and take shower inside. Here are their exact locations:

3F, West side of Entrance Gate 8, T1.
B1, between Gate D2 and Gate D3, International Arrival, T2.
Between Gate D5 and Gate D6, Domestic Arrival, B1, T2.
2F, West side of public area, Arrival Hall, T3.