underground parking and surface drainage
underground parking and surface drainage
(OP)
HI All,
We are assisting with a re-waterproofing project for an existing hotel plaza. There is an access road that comes spiraling down from the street and to a rather large plaza for guest arrival/check-in (all open air, above grade). This is a porte-cochere that is similar to a loop/cul-de-sac with a branch that leads down to an underground parking lot. The surface (landscaping areas, sidewalks, road, etc.) has had leakage issues develop over time and is going to be scraped, waterproofed, snowmelted, and re-surfaced. Very expensive.
There is a very limited amount of surface drainage facilities...a few small area drains (4" dia) and a couple trench drains. THERE ARE NO SURFACE OVERFLOW OPPORTUNITIES as the site is located in a 'hole' and there are no easements through the developed adjacent properties for introducing a new storm sewer. It appears that during a heavy rain, the trench drains wouldn't catch anywhere near the amount of runoff and that the drainage will continue down into the parking garage.
This is an older building and there are no plumbing drawings that have been found. My concerns are this:
1. If we analyze the drainage requirements and introduce new catchments, they will need to penetrate the structure/deck and tie into the existing drain system;
2. These new drains will certainly increase the amount of flow into the internal pipe system and we have no idea if there is adequate capacity;
3. The site improvements are basically going back in exactly where they were (same grades and alignments) so a substantially improved drainage concept can only occur through additional inlets (see #1 above)
4. The nature of the site crosses over thresholds of responsibility: From Civil (site/surface) to M/E/P (inside the building);
5. If we do nothing to improve the site drainage after recognizing the obvious deficiencies during a remodel (the best time to fix it), are we violating our duty and the Standard of Practice?
At this point, we have (in writing) asked the architect/project leader if there have been any drainage issues/complaints (they said there have not, but I doubt the question was posed to the hotel). I am leaning toward analyzing the existing drainage facilities to determine how much of a design storm (100 year?) can be collected with what is there now and how much is likely to overflow into the parking garage for the 'handoff' to the plumbing engineer...
Any advice is appreciated.
EG
We are assisting with a re-waterproofing project for an existing hotel plaza. There is an access road that comes spiraling down from the street and to a rather large plaza for guest arrival/check-in (all open air, above grade). This is a porte-cochere that is similar to a loop/cul-de-sac with a branch that leads down to an underground parking lot. The surface (landscaping areas, sidewalks, road, etc.) has had leakage issues develop over time and is going to be scraped, waterproofed, snowmelted, and re-surfaced. Very expensive.
There is a very limited amount of surface drainage facilities...a few small area drains (4" dia) and a couple trench drains. THERE ARE NO SURFACE OVERFLOW OPPORTUNITIES as the site is located in a 'hole' and there are no easements through the developed adjacent properties for introducing a new storm sewer. It appears that during a heavy rain, the trench drains wouldn't catch anywhere near the amount of runoff and that the drainage will continue down into the parking garage.
This is an older building and there are no plumbing drawings that have been found. My concerns are this:
1. If we analyze the drainage requirements and introduce new catchments, they will need to penetrate the structure/deck and tie into the existing drain system;
2. These new drains will certainly increase the amount of flow into the internal pipe system and we have no idea if there is adequate capacity;
3. The site improvements are basically going back in exactly where they were (same grades and alignments) so a substantially improved drainage concept can only occur through additional inlets (see #1 above)
4. The nature of the site crosses over thresholds of responsibility: From Civil (site/surface) to M/E/P (inside the building);
5. If we do nothing to improve the site drainage after recognizing the obvious deficiencies during a remodel (the best time to fix it), are we violating our duty and the Standard of Practice?
At this point, we have (in writing) asked the architect/project leader if there have been any drainage issues/complaints (they said there have not, but I doubt the question was posed to the hotel). I am leaning toward analyzing the existing drainage facilities to determine how much of a design storm (100 year?) can be collected with what is there now and how much is likely to overflow into the parking garage for the 'handoff' to the plumbing engineer...
Any advice is appreciated.
EG





RE: underground parking and surface drainage
RE: underground parking and surface drainage
The first thing you need to do before dreaming up design options is answer your questions about what's actually out there. Go run a hose and see where the water goes. Have the building maintenance guy meet you out there for half a day and follow the water. Do the same exercise inside the deck as well.
Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com
RE: underground parking and surface drainage
Our company performs Civil Engineering and Surveying. We will not be covered and therefore our client will not be either (that is a whole other topic). This is a project with a history of waterproofing issues and now we are involving ourselves without insurance coverage (regardless of LOL or indemnities) on a waterproofing project.
Bowing out of it with my next phone call...
Thanks for your time.
EG
RE: underground parking and surface drainage
RE: underground parking and surface drainage
Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com
RE: underground parking and surface drainage
Mike McCann
MMC Engineering
RE: underground parking and surface drainage
My knowledge of this only comes from a discussion on LinkedIn a few years back. It started with someone asking if they knew a vendor with a truck small enough to get into the garage to provide maintenance on an underground system. The conversation naturally progressed to "you really put that under the building?" ... followed up with answers such as "where do you think we put them in NYC." Quite a few people chimed in with having done this approach before, so this was not a one off case.
I will try to find the link, but I don't even remember exactly which forum this occurred in.
RE: underground parking and surface drainage
Mike McCann
MMC Engineering
RE: underground parking and surface drainage
RE: underground parking and surface drainage
Sorry for the hijack.
Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com