question regarding sewer map on property

[keving]

Hi,
Im about to purchase a property as a first time buyer. I have question to all the experienced guys out there.

I read through the water drainage search of the property. Im not sure how to make of the map.It shows a point for sewerage and also another point with blue marks which Im assuming surface water point.Property is mark as x in the image. Please see the image.

[url]http://h.imagehost.org/download/0217/sewer_map[/url]

Does this mean I have a sewer main point at my backyard because as far as I can tell I dont see any manhole cover at the garden.
Would this also mean I cant extend the rear property up to 3 metres.

Thanks for your views and suggestion.[/img]