Daily 1500 Search engine visitors but Alexa rank is not decreasing ?

In last 12 years, I have got a website readnsurf.com (belongs to client) which gets 3000 to 5000 unique visitors daily but still more than 100K alexa. More interestingly 60% visitors of the site (readnsurf.com) comes from Google search ! When I have tried to get more visitors via white hat method, it is stopped to change Alexa ranking . I have failed to get the reason(s) as monitored via Google analytics as well as other a few tools. Any expert please rectify my situation!

See original post by umain30