Sven/Tom:
I'm currently updating a list of C&A courses in North America that I've been working on for the past couple years. I'm not ready for a gca post quite yet, but it's clear to me that the Alison course designed for the CCD in 1926 and opened in 1927 is a totally new course. True, part of the Alison course is on property that included some of the area of Colt's course, that lying between the clubhouse (both former and current) and Provencal and between Kercheval and Chalfonte, the former Black Marsh Ditch. The Alison course also includes all the area from the clubhouse to Moross Road that was not part of the club's property in 1913 thru 1925. I recently overlaid the NY Sun layout for the 1915 AM (prior GCA post) with today's Google Earth and none of the hole corridors or green sites align, with the possible exception that the current practice green may be the site of the original Colt 18th green.
Colt's holes 6 thru 13 were either in the area west of Black Marsh Ditch, today's Chalfonte, or crossed the ditch into the area of the houses now existing at the Chalfonte end of the course. That's 8 holes from Colt gone. The area between the clubhouse (today's ch and the "golf pavilion" in 1913") and Moross Road include all or parts of the current Alison holes 6 thru 12 and 14 and 15. That's 9 holes on property that Colt didn't have to work with. It appears that today's 1 thru 5, 13, and 16 thru 18 are actually on property that was part of both courses. Again the best I can tell, there is no complete hole routing or green site from both courses that overlaps, only parts of certain fairways and those are from different playing angles.
I am currently reading a "History of the CCD" manuscript (probably written c.1960) that I found at the USGA Library last week and interestingly to me it says that the "Colt & Allison (sic) plans approved by the BOD April 1926" noted that "plans for a nine-hole course inside the new 18-hole layout were also approved…" Tom would know, but could you put 9 holes in the area of the tennis course, polo field, and maintenance shed and woods? Or maybe RTJ SR found the right solution. Additionally, in partial answer to a question from a previous question as to why the CCD thru out a 6400 yard plus Colt course worthy of a National Championship for a new course by his partner: the history I'm reading suggests that the Wayne County Road Commission was considering a road thru the course either in line with the Black marsh Ditch (Chalfonte) or, even worse, Charlevoix which would have cut thru the property where the tennis course are now. So the club was also looking to ward off a potential future problem that did occur on the mid 20s. At Port Huron Golf Club (see my IMO post) we lost two Alison holes to the St Clair County Road commission in 1950. Not quite as bad as the CCD could have been.
As I continue researching this interesting situation where Colt and Alison did separate courses for the same club at different times, I'll keep looking for clues of this Ross tidbit. So far I've seen nothing except what Sven just posted.
Anthony