Discussion: View Thread

I have a facility owner that is interested to talk with other facility owners about their user experiences with parking lots designed to flood in intense storm events. Like most projects, they have quite a few compounding constraints and are looking at cost effective design alternatives to the fully contained UG detention system as currently designed. The CE of record has suggested a mix of the UG system and use of the parking area for 25 yr storms. I'm encouraged by the idea as I've seen projects throughout the western U.S. use this technique.

The owner will operate a religious facility and a day school and is curious if other owners with similar designs would do it again or if they are burdened by the occasional standing water in the parking areas. Are there any good resources or personal testimonies I can point them towards?

------------------------------
Jesse Kamm PhD, PMP, A.M.ASCE
Vice President of Construction Management
------------------------------

The nice  thing about religious facilities are that the parking lots are not occupied during all time periods, and that most people do not go to church during flooding events.  The bad thing about religious facilities is that they tend to be centers of safety and organization during natural disasters.  As I am from the Houston area, I have seen this happen many times.  Nothing worst for a parishioner to come into church with a dry car, and have to have it towed when they leave 2-hours later because it has 2 feet of water surrounding it.  

I have designed parking lot detention.  When I do it, my rule of thumb is that 25% of the parking spaces need to be dry during the 100-year event, another 25% should be dry during the 25 year event, and the rest should not flood more than 9-inches during the 100-year event.  This keeps it out of most cars.   Lots of inlets are required to ensure that the water does not start accumulating above the surface before the underground system is filled.  This prevents the more-than occasional issue of standing water.

Underground systems will collect sediment and debris if you are not careful, and most systems are hard to impossible to remove that sediment/debris.  Consider sediment collection in the design of the inlet locations.  If available, use an above ground system for the first 1-2 inches of storage, and send the drainage to the above-ground storage system for the small events, and overflow to the below ground systems for the extreme events.  That way, most of the items that cause chaos to underground detention systems (plastic cup lids, foam cups, plastic sacs, etc.) get trapped in the above ground pond that can be maintained.  I have found a reverse grade storm sewer between the above ground pond and the underground detention works well at keeping the floatables out, while allowing water to flow in.  It works even better if you have a wet pond for the above ground part with a large separation between inlets to the pond, and outlet to the underground detention. 

There are lots of other things to consider, including what complies with the local regulations.  It is always possible to pay for for a system review by an independent engineer that practices in the specific community if you have specific concerns about whether a specific design will meet the needs of the owner.  Its no different than a second opinion from a doctor over a treatment process.

------------------------------
Dwayne Culp, Ph.D.
Culp Engineering, LLC
Rosenberg TX
(713)898-1977
------------------------------

Original Message:
Sent: 02-21-2019 18:08
From: Jesse Kamm
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

I have a facility owner that is interested to talk with other facility owners about their user experiences with parking lots designed to flood in intense storm events. Like most projects, they have quite a few compounding constraints and are looking at cost effective design alternatives to the fully contained UG detention system as currently designed. The CE of record has suggested a mix of the UG system and use of the parking area for 25 yr storms. I'm encouraged by the idea as I've seen projects throughout the western U.S. use this technique.

The owner will operate a religious facility and a day school and is curious if other owners with similar designs would do it again or if they are burdened by the occasional standing water in the parking areas. Are there any good resources or personal testimonies I can point them towards?

------------------------------
Jesse Kamm PhD, PMP, A.M.ASCE
Vice President of Construction Management
------------------------------

Dr. Culp, This is very helpful. Thank you so much for the response. I will share this information with the client and the design/build team. I'd be interested to hear if anyone has operational use strategies in place for such facilities. It's one thing to get the design correct and another to advise the owner on the proper way to use and manage the systems as designed. I find expectation setting to be sometimes as challenging as the engineering problems themselves. For instance, perhaps there is a management plan the team can come up with for certain "triggers" to alert the facility managers to close off certain spaces when rain events are forecast.

------------------------------
Jesse Kamm PhD, PMP, A.M.ASCE
Vice President of Construction Management
------------------------------

Original Message:
Sent: 02-22-2019 12:16
From: Dwayne Culp
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

The nice  thing about religious facilities are that the parking lots are not occupied during all time periods, and that most people do not go to church during flooding events.  The bad thing about religious facilities is that they tend to be centers of safety and organization during natural disasters.  As I am from the Houston area, I have seen this happen many times.  Nothing worst for a parishioner to come into church with a dry car, and have to have it towed when they leave 2-hours later because it has 2 feet of water surrounding it.

I have designed parking lot detention.  When I do it, my rule of thumb is that 25% of the parking spaces need to be dry during the 100-year event, another 25% should be dry during the 25 year event, and the rest should not flood more than 9-inches during the 100-year event.  This keeps it out of most cars.   Lots of inlets are required to ensure that the water does not start accumulating above the surface before the underground system is filled.  This prevents the more-than occasional issue of standing water.

Underground systems will collect sediment and debris if you are not careful, and most systems are hard to impossible to remove that sediment/debris.  Consider sediment collection in the design of the inlet locations.  If available, use an above ground system for the first 1-2 inches of storage, and send the drainage to the above-ground storage system for the small events, and overflow to the below ground systems for the extreme events.  That way, most of the items that cause chaos to underground detention systems (plastic cup lids, foam cups, plastic sacs, etc.) get trapped in the above ground pond that can be maintained.  I have found a reverse grade storm sewer between the above ground pond and the underground detention works well at keeping the floatables out, while allowing water to flow in.  It works even better if you have a wet pond for the above ground part with a large separation between inlets to the pond, and outlet to the underground detention.

There are lots of other things to consider, including what complies with the local regulations.  It is always possible to pay for for a system review by an independent engineer that practices in the specific community if you have specific concerns about whether a specific design will meet the needs of the owner.  Its no different than a second opinion from a doctor over a treatment process.

------------------------------
Dwayne Culp, Ph.D.
Culp Engineering, LLC
Rosenberg TX
(713)898-1977

Original Message:
Sent: 02-21-2019 18:08
From: Jesse Kamm
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

I have a facility owner that is interested to talk with other facility owners about their user experiences with parking lots designed to flood in intense storm events. Like most projects, they have quite a few compounding constraints and are looking at cost effective design alternatives to the fully contained UG detention system as currently designed. The CE of record has suggested a mix of the UG system and use of the parking area for 25 yr storms. I'm encouraged by the idea as I've seen projects throughout the western U.S. use this technique.

The owner will operate a religious facility and a day school and is curious if other owners with similar designs would do it again or if they are burdened by the occasional standing water in the parking areas. Are there any good resources or personal testimonies I can point them towards?

------------------------------
Jesse Kamm PhD, PMP, A.M.ASCE
Vice President of Construction Management
------------------------------

Jesse, is there an adjacent playfield or lawn that could be used for floodwater detention?  City of Cincinnati has an extensive soccer field complex that is "unavailable" during flood events.

------------------------------
James Justin Mercier, P.E.
Life Member ASCE
Sr. Life Member IEEE
Austin Texas
512-442-4016
------------------------------

Original Message:
Sent: 02-22-2019 15:30
From: Jesse Kamm
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

Dr. Culp, This is very helpful. Thank you so much for the response. I will share this information with the client and the design/build team. I'd be interested to hear if anyone has operational use strategies in place for such facilities. It's one thing to get the design correct and another to advise the owner on the proper way to use and manage the systems as designed. I find expectation setting to be sometimes as challenging as the engineering problems themselves. For instance, perhaps there is a management plan the team can come up with for certain "triggers" to alert the facility managers to close off certain spaces when rain events are forecast.

------------------------------
Jesse Kamm PhD, PMP, A.M.ASCE
Vice President of Construction Management

Original Message:
Sent: 02-22-2019 12:16
From: Dwayne Culp
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

The nice  thing about religious facilities are that the parking lots are not occupied during all time periods, and that most people do not go to church during flooding events.  The bad thing about religious facilities is that they tend to be centers of safety and organization during natural disasters.  As I am from the Houston area, I have seen this happen many times.  Nothing worst for a parishioner to come into church with a dry car, and have to have it towed when they leave 2-hours later because it has 2 feet of water surrounding it.

I have designed parking lot detention.  When I do it, my rule of thumb is that 25% of the parking spaces need to be dry during the 100-year event, another 25% should be dry during the 25 year event, and the rest should not flood more than 9-inches during the 100-year event.  This keeps it out of most cars.   Lots of inlets are required to ensure that the water does not start accumulating above the surface before the underground system is filled.  This prevents the more-than occasional issue of standing water.

Underground systems will collect sediment and debris if you are not careful, and most systems are hard to impossible to remove that sediment/debris.  Consider sediment collection in the design of the inlet locations.  If available, use an above ground system for the first 1-2 inches of storage, and send the drainage to the above-ground storage system for the small events, and overflow to the below ground systems for the extreme events.  That way, most of the items that cause chaos to underground detention systems (plastic cup lids, foam cups, plastic sacs, etc.) get trapped in the above ground pond that can be maintained.  I have found a reverse grade storm sewer between the above ground pond and the underground detention works well at keeping the floatables out, while allowing water to flow in.  It works even better if you have a wet pond for the above ground part with a large separation between inlets to the pond, and outlet to the underground detention.

There are lots of other things to consider, including what complies with the local regulations.  It is always possible to pay for for a system review by an independent engineer that practices in the specific community if you have specific concerns about whether a specific design will meet the needs of the owner.  Its no different than a second opinion from a doctor over a treatment process.

------------------------------
Dwayne Culp, Ph.D.
Culp Engineering, LLC
Rosenberg TX
(713)898-1977

Original Message:
Sent: 02-21-2019 18:08
From: Jesse Kamm
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

I have a facility owner that is interested to talk with other facility owners about their user experiences with parking lots designed to flood in intense storm events. Like most projects, they have quite a few compounding constraints and are looking at cost effective design alternatives to the fully contained UG detention system as currently designed. The CE of record has suggested a mix of the UG system and use of the parking area for 25 yr storms. I'm encouraged by the idea as I've seen projects throughout the western U.S. use this technique.

The owner will operate a religious facility and a day school and is curious if other owners with similar designs would do it again or if they are burdened by the occasional standing water in the parking areas. Are there any good resources or personal testimonies I can point them towards?

------------------------------
Jesse Kamm PhD, PMP, A.M.ASCE
Vice President of Construction Management
------------------------------

Not really much of a nearby field available. It's a really interesting site to work on. A large portion of the property is within FEMA 100 year flood zone and therefore off limits. It's an old farm land in a historical part of TN, over time the surrounding land had been developed into single family housing and some of these developments have designed their overflow to shift onto this property. On top of that, the state/city is currently redesigning the ROW and took additional land in eminent domain. I agree with an earlier comment about the troubles with the underground systems over time thus why I'm liking the combined approach. I think I can get the stakeholder buy-in, but I also don't want to support anything that hurts the operational mission.

------------------------------
Jesse Kamm PhD, PMP, A.M.ASCE
Senior Vice President of Construction Management
------------------------------

Original Message:
Sent: 02-23-2019 08:43
From: James Mercier
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

Jesse, is there an adjacent playfield or lawn that could be used for floodwater detention?  City of Cincinnati has an extensive soccer field complex that is "unavailable" during flood events.

------------------------------
James Justin Mercier, P.E.
Life Member ASCE
Sr. Life Member IEEE
Austin Texas
512-442-4016

Original Message:
Sent: 02-22-2019 15:30
From: Jesse Kamm
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

Dr. Culp, This is very helpful. Thank you so much for the response. I will share this information with the client and the design/build team. I'd be interested to hear if anyone has operational use strategies in place for such facilities. It's one thing to get the design correct and another to advise the owner on the proper way to use and manage the systems as designed. I find expectation setting to be sometimes as challenging as the engineering problems themselves. For instance, perhaps there is a management plan the team can come up with for certain "triggers" to alert the facility managers to close off certain spaces when rain events are forecast.

------------------------------
Jesse Kamm PhD, PMP, A.M.ASCE
Vice President of Construction Management

Original Message:
Sent: 02-22-2019 12:16
From: Dwayne Culp
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

The nice  thing about religious facilities are that the parking lots are not occupied during all time periods, and that most people do not go to church during flooding events.  The bad thing about religious facilities is that they tend to be centers of safety and organization during natural disasters.  As I am from the Houston area, I have seen this happen many times.  Nothing worst for a parishioner to come into church with a dry car, and have to have it towed when they leave 2-hours later because it has 2 feet of water surrounding it.

I have designed parking lot detention.  When I do it, my rule of thumb is that 25% of the parking spaces need to be dry during the 100-year event, another 25% should be dry during the 25 year event, and the rest should not flood more than 9-inches during the 100-year event.  This keeps it out of most cars.   Lots of inlets are required to ensure that the water does not start accumulating above the surface before the underground system is filled.  This prevents the more-than occasional issue of standing water.

Underground systems will collect sediment and debris if you are not careful, and most systems are hard to impossible to remove that sediment/debris.  Consider sediment collection in the design of the inlet locations.  If available, use an above ground system for the first 1-2 inches of storage, and send the drainage to the above-ground storage system for the small events, and overflow to the below ground systems for the extreme events.  That way, most of the items that cause chaos to underground detention systems (plastic cup lids, foam cups, plastic sacs, etc.) get trapped in the above ground pond that can be maintained.  I have found a reverse grade storm sewer between the above ground pond and the underground detention works well at keeping the floatables out, while allowing water to flow in.  It works even better if you have a wet pond for the above ground part with a large separation between inlets to the pond, and outlet to the underground detention.

There are lots of other things to consider, including what complies with the local regulations.  It is always possible to pay for for a system review by an independent engineer that practices in the specific community if you have specific concerns about whether a specific design will meet the needs of the owner.  Its no different than a second opinion from a doctor over a treatment process.

------------------------------
Dwayne Culp, Ph.D.
Culp Engineering, LLC
Rosenberg TX
(713)898-1977

Original Message:
Sent: 02-21-2019 18:08
From: Jesse Kamm
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

I have a facility owner that is interested to talk with other facility owners about their user experiences with parking lots designed to flood in intense storm events. Like most projects, they have quite a few compounding constraints and are looking at cost effective design alternatives to the fully contained UG detention system as currently designed. The CE of record has suggested a mix of the UG system and use of the parking area for 25 yr storms. I'm encouraged by the idea as I've seen projects throughout the western U.S. use this technique.

The owner will operate a religious facility and a day school and is curious if other owners with similar designs would do it again or if they are burdened by the occasional standing water in the parking areas. Are there any good resources or personal testimonies I can point them towards?

------------------------------
Jesse Kamm PhD, PMP, A.M.ASCE
Vice President of Construction Management
------------------------------

Is the property in a floodway or just within the 1% chance flood zone (100-year)?  You specified the 4% (25-year) chance flood instead of the 1%; is the property actually so low that the 4% overtops it?  If it's the 4%, I'd be a bit leery for a Church school.  But, if it's the 1%, then the parking lot should be okay in the flood zone below the BFE as long as it's not presenting an obstruction to the flow during a flood event or reducing flood storage.  What is the local Floodplain Administrator (FPA) saying?



------------------------------
James Justin Mercier, P.E., CFM
Life Member ASCE
Sr. Life Member IEEE
Austin Texas
512-442-4016
------------------------------

Original Message:
Sent: 02-25-2019 12:24
From: Jesse Kamm
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

Not really much of a nearby field available. It's a really interesting site to work on. A large portion of the property is within FEMA 100 year flood zone and therefore off limits. It's an old farm land in a historical part of TN, over time the surrounding land had been developed into single family housing and some of these developments have designed their overflow to shift onto this property. On top of that, the state/city is currently redesigning the ROW and took additional land in eminent domain. I agree with an earlier comment about the troubles with the underground systems over time thus why I'm liking the combined approach. I think I can get the stakeholder buy-in, but I also don't want to support anything that hurts the operational mission.

------------------------------
Jesse Kamm PhD, PMP, A.M.ASCE
Senior Vice President of Construction Management

Original Message:
Sent: 02-23-2019 08:43
From: James Mercier
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

Jesse, is there an adjacent playfield or lawn that could be used for floodwater detention?  City of Cincinnati has an extensive soccer field complex that is "unavailable" during flood events.

------------------------------
James Justin Mercier, P.E.
Life Member ASCE
Sr. Life Member IEEE
Austin Texas
512-442-4016

Original Message:
Sent: 02-22-2019 15:30
From: Jesse Kamm
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

Dr. Culp, This is very helpful. Thank you so much for the response. I will share this information with the client and the design/build team. I'd be interested to hear if anyone has operational use strategies in place for such facilities. It's one thing to get the design correct and another to advise the owner on the proper way to use and manage the systems as designed. I find expectation setting to be sometimes as challenging as the engineering problems themselves. For instance, perhaps there is a management plan the team can come up with for certain "triggers" to alert the facility managers to close off certain spaces when rain events are forecast.

------------------------------
Jesse Kamm PhD, PMP, A.M.ASCE
Vice President of Construction Management

Original Message:
Sent: 02-22-2019 12:16
From: Dwayne Culp
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

The nice  thing about religious facilities are that the parking lots are not occupied during all time periods, and that most people do not go to church during flooding events.  The bad thing about religious facilities is that they tend to be centers of safety and organization during natural disasters.  As I am from the Houston area, I have seen this happen many times.  Nothing worst for a parishioner to come into church with a dry car, and have to have it towed when they leave 2-hours later because it has 2 feet of water surrounding it.

I have designed parking lot detention.  When I do it, my rule of thumb is that 25% of the parking spaces need to be dry during the 100-year event, another 25% should be dry during the 25 year event, and the rest should not flood more than 9-inches during the 100-year event.  This keeps it out of most cars.   Lots of inlets are required to ensure that the water does not start accumulating above the surface before the underground system is filled.  This prevents the more-than occasional issue of standing water.

Underground systems will collect sediment and debris if you are not careful, and most systems are hard to impossible to remove that sediment/debris.  Consider sediment collection in the design of the inlet locations.  If available, use an above ground system for the first 1-2 inches of storage, and send the drainage to the above-ground storage system for the small events, and overflow to the below ground systems for the extreme events.  That way, most of the items that cause chaos to underground detention systems (plastic cup lids, foam cups, plastic sacs, etc.) get trapped in the above ground pond that can be maintained.  I have found a reverse grade storm sewer between the above ground pond and the underground detention works well at keeping the floatables out, while allowing water to flow in.  It works even better if you have a wet pond for the above ground part with a large separation between inlets to the pond, and outlet to the underground detention.

There are lots of other things to consider, including what complies with the local regulations.  It is always possible to pay for for a system review by an independent engineer that practices in the specific community if you have specific concerns about whether a specific design will meet the needs of the owner.  Its no different than a second opinion from a doctor over a treatment process.

------------------------------
Dwayne Culp, Ph.D.
Culp Engineering, LLC
Rosenberg TX
(713)898-1977

Original Message:
Sent: 02-21-2019 18:08
From: Jesse Kamm
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

I have a facility owner that is interested to talk with other facility owners about their user experiences with parking lots designed to flood in intense storm events. Like most projects, they have quite a few compounding constraints and are looking at cost effective design alternatives to the fully contained UG detention system as currently designed. The CE of record has suggested a mix of the UG system and use of the parking area for 25 yr storms. I'm encouraged by the idea as I've seen projects throughout the western U.S. use this technique.

The owner will operate a religious facility and a day school and is curious if other owners with similar designs would do it again or if they are burdened by the occasional standing water in the parking areas. Are there any good resources or personal testimonies I can point them towards?

------------------------------
Jesse Kamm PhD, PMP, A.M.ASCE
Vice President of Construction Management
------------------------------

Per the geotech/CE report, the city is requiring (direct quote from the report) "a "first flush" volume to be for a specified time and released. The further requirement is that the "pre" and "post" volume runoffs be equal for the 25 and 100-year storm events.  Alternative methods to comply with first flush requirement is to use a mechanical device to filter the runoff and use low impact development methods.

From the topo, there is a geographical 100yr floodplain line on the property that corresponds with a creek (elevation from creek edge to floodplain line varies but is approx. 20' lower than the development portions, its a nice angulating topography.) We are not encroaching the 100-yr line.

The language the project civil engineer used has been the 25yr event thus far, but I'm not certain if he was speaking in descriptive terms or specific requirements. I will certainly clarify the specifics but in terms of the owner's interest, I suspect any rain event that causes cancellations could be concerning. Another comment in a different thread mentioned a 1-inch containment within a 24hr period, to me that seems entirely feasible. From a user perspective, I might be a little annoyed that I have to walk through 1-inch of water to my car, but it wouldn't stop me from accessing my car and driving away. I'm currently awaiting the re-design of the mixed system and associated cost estimates. The initial design for the entirely contained underground system was about a quarter of the costs of the entire project!

------------------------------
Jesse Kamm PhD, PMP, A.M.ASCE
Senior Vice President of Construction Management
------------------------------

Original Message:
Sent: 02-26-2019 01:47
From: James Mercier
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

Is the property in a floodway or just within the 1% chance flood zone (100-year)?  You specified the 4% (25-year) chance flood instead of the 1%; is the property actually so low that the 4% overtops it?  If it's the 4%, I'd be a bit leery for a Church school.  But, if it's the 1%, then the parking lot should be okay in the flood zone below the BFE as long as it's not presenting an obstruction to the flow during a flood event or reducing flood storage.  What is the local Floodplain Administrator (FPA) saying?



------------------------------
James Justin Mercier, P.E., CFM
Life Member ASCE
Sr. Life Member IEEE
Austin Texas
512-442-4016

Original Message:
Sent: 02-25-2019 12:24
From: Jesse Kamm
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

Not really much of a nearby field available. It's a really interesting site to work on. A large portion of the property is within FEMA 100 year flood zone and therefore off limits. It's an old farm land in a historical part of TN, over time the surrounding land had been developed into single family housing and some of these developments have designed their overflow to shift onto this property. On top of that, the state/city is currently redesigning the ROW and took additional land in eminent domain. I agree with an earlier comment about the troubles with the underground systems over time thus why I'm liking the combined approach. I think I can get the stakeholder buy-in, but I also don't want to support anything that hurts the operational mission.

------------------------------
Jesse Kamm PhD, PMP, A.M.ASCE
Senior Vice President of Construction Management

Original Message:
Sent: 02-23-2019 08:43
From: James Mercier
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

Jesse, is there an adjacent playfield or lawn that could be used for floodwater detention?  City of Cincinnati has an extensive soccer field complex that is "unavailable" during flood events.

------------------------------
James Justin Mercier, P.E.
Life Member ASCE
Sr. Life Member IEEE
Austin Texas
512-442-4016

Original Message:
Sent: 02-22-2019 15:30
From: Jesse Kamm
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

Dr. Culp, This is very helpful. Thank you so much for the response. I will share this information with the client and the design/build team. I'd be interested to hear if anyone has operational use strategies in place for such facilities. It's one thing to get the design correct and another to advise the owner on the proper way to use and manage the systems as designed. I find expectation setting to be sometimes as challenging as the engineering problems themselves. For instance, perhaps there is a management plan the team can come up with for certain "triggers" to alert the facility managers to close off certain spaces when rain events are forecast.

------------------------------
Jesse Kamm PhD, PMP, A.M.ASCE
Vice President of Construction Management

Original Message:
Sent: 02-22-2019 12:16
From: Dwayne Culp
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

The nice  thing about religious facilities are that the parking lots are not occupied during all time periods, and that most people do not go to church during flooding events.  The bad thing about religious facilities is that they tend to be centers of safety and organization during natural disasters.  As I am from the Houston area, I have seen this happen many times.  Nothing worst for a parishioner to come into church with a dry car, and have to have it towed when they leave 2-hours later because it has 2 feet of water surrounding it.

I have designed parking lot detention.  When I do it, my rule of thumb is that 25% of the parking spaces need to be dry during the 100-year event, another 25% should be dry during the 25 year event, and the rest should not flood more than 9-inches during the 100-year event.  This keeps it out of most cars.   Lots of inlets are required to ensure that the water does not start accumulating above the surface before the underground system is filled.  This prevents the more-than occasional issue of standing water.

Underground systems will collect sediment and debris if you are not careful, and most systems are hard to impossible to remove that sediment/debris.  Consider sediment collection in the design of the inlet locations.  If available, use an above ground system for the first 1-2 inches of storage, and send the drainage to the above-ground storage system for the small events, and overflow to the below ground systems for the extreme events.  That way, most of the items that cause chaos to underground detention systems (plastic cup lids, foam cups, plastic sacs, etc.) get trapped in the above ground pond that can be maintained.  I have found a reverse grade storm sewer between the above ground pond and the underground detention works well at keeping the floatables out, while allowing water to flow in.  It works even better if you have a wet pond for the above ground part with a large separation between inlets to the pond, and outlet to the underground detention.

There are lots of other things to consider, including what complies with the local regulations.  It is always possible to pay for for a system review by an independent engineer that practices in the specific community if you have specific concerns about whether a specific design will meet the needs of the owner.  Its no different than a second opinion from a doctor over a treatment process.

------------------------------
Dwayne Culp, Ph.D.
Culp Engineering, LLC
Rosenberg TX
(713)898-1977

Original Message:
Sent: 02-21-2019 18:08
From: Jesse Kamm
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

I have a facility owner that is interested to talk with other facility owners about their user experiences with parking lots designed to flood in intense storm events. Like most projects, they have quite a few compounding constraints and are looking at cost effective design alternatives to the fully contained UG detention system as currently designed. The CE of record has suggested a mix of the UG system and use of the parking area for 25 yr storms. I'm encouraged by the idea as I've seen projects throughout the western U.S. use this technique.

The owner will operate a religious facility and a day school and is curious if other owners with similar designs would do it again or if they are burdened by the occasional standing water in the parking areas. Are there any good resources or personal testimonies I can point them towards?

------------------------------
Jesse Kamm PhD, PMP, A.M.ASCE
Vice President of Construction Management
------------------------------

If you have a 20' drop to the floodplain, can't you put a detention pond off the parking but above the floodplain?

------------------------------
James Justin Mercier, P.E., CFM
Life Member ASCE
Sr. Life Member IEEE
Austin Texas
512-442-4016
------------------------------

Original Message:
Sent: 03-04-2019 09:42
From: Jesse Kamm
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

Per the geotech/CE report, the city is requiring (direct quote from the report) "a "first flush" volume to be for a specified time and released. The further requirement is that the "pre" and "post" volume runoffs be equal for the 25 and 100-year storm events.  Alternative methods to comply with first flush requirement is to use a mechanical device to filter the runoff and use low impact development methods.

From the topo, there is a geographical 100yr floodplain line on the property that corresponds with a creek (elevation from creek edge to floodplain line varies but is approx. 20' lower than the development portions, its a nice angulating topography.) We are not encroaching the 100-yr line.

The language the project civil engineer used has been the 25yr event thus far, but I'm not certain if he was speaking in descriptive terms or specific requirements. I will certainly clarify the specifics but in terms of the owner's interest, I suspect any rain event that causes cancellations could be concerning. Another comment in a different thread mentioned a 1-inch containment within a 24hr period, to me that seems entirely feasible. From a user perspective, I might be a little annoyed that I have to walk through 1-inch of water to my car, but it wouldn't stop me from accessing my car and driving away. I'm currently awaiting the re-design of the mixed system and associated cost estimates. The initial design for the entirely contained underground system was about a quarter of the costs of the entire project!

------------------------------
Jesse Kamm PhD, PMP, A.M.ASCE
Senior Vice President of Construction Management

Original Message:
Sent: 02-26-2019 01:47
From: James Mercier
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

Is the property in a floodway or just within the 1% chance flood zone (100-year)?  You specified the 4% (25-year) chance flood instead of the 1%; is the property actually so low that the 4% overtops it?  If it's the 4%, I'd be a bit leery for a Church school.  But, if it's the 1%, then the parking lot should be okay in the flood zone below the BFE as long as it's not presenting an obstruction to the flow during a flood event or reducing flood storage.  What is the local Floodplain Administrator (FPA) saying?



------------------------------
James Justin Mercier, P.E., CFM
Life Member ASCE
Sr. Life Member IEEE
Austin Texas
512-442-4016

Original Message:
Sent: 02-25-2019 12:24
From: Jesse Kamm
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

Not really much of a nearby field available. It's a really interesting site to work on. A large portion of the property is within FEMA 100 year flood zone and therefore off limits. It's an old farm land in a historical part of TN, over time the surrounding land had been developed into single family housing and some of these developments have designed their overflow to shift onto this property. On top of that, the state/city is currently redesigning the ROW and took additional land in eminent domain. I agree with an earlier comment about the troubles with the underground systems over time thus why I'm liking the combined approach. I think I can get the stakeholder buy-in, but I also don't want to support anything that hurts the operational mission.

------------------------------
Jesse Kamm PhD, PMP, A.M.ASCE
Senior Vice President of Construction Management

Original Message:
Sent: 02-23-2019 08:43
From: James Mercier
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

Jesse, is there an adjacent playfield or lawn that could be used for floodwater detention?  City of Cincinnati has an extensive soccer field complex that is "unavailable" during flood events.

------------------------------
James Justin Mercier, P.E.
Life Member ASCE
Sr. Life Member IEEE
Austin Texas
512-442-4016

Original Message:
Sent: 02-22-2019 15:30
From: Jesse Kamm
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

Dr. Culp, This is very helpful. Thank you so much for the response. I will share this information with the client and the design/build team. I'd be interested to hear if anyone has operational use strategies in place for such facilities. It's one thing to get the design correct and another to advise the owner on the proper way to use and manage the systems as designed. I find expectation setting to be sometimes as challenging as the engineering problems themselves. For instance, perhaps there is a management plan the team can come up with for certain "triggers" to alert the facility managers to close off certain spaces when rain events are forecast.

------------------------------
Jesse Kamm PhD, PMP, A.M.ASCE
Vice President of Construction Management

Original Message:
Sent: 02-22-2019 12:16
From: Dwayne Culp
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

The nice  thing about religious facilities are that the parking lots are not occupied during all time periods, and that most people do not go to church during flooding events.  The bad thing about religious facilities is that they tend to be centers of safety and organization during natural disasters.  As I am from the Houston area, I have seen this happen many times.  Nothing worst for a parishioner to come into church with a dry car, and have to have it towed when they leave 2-hours later because it has 2 feet of water surrounding it.

I have designed parking lot detention.  When I do it, my rule of thumb is that 25% of the parking spaces need to be dry during the 100-year event, another 25% should be dry during the 25 year event, and the rest should not flood more than 9-inches during the 100-year event.  This keeps it out of most cars.   Lots of inlets are required to ensure that the water does not start accumulating above the surface before the underground system is filled.  This prevents the more-than occasional issue of standing water.

Underground systems will collect sediment and debris if you are not careful, and most systems are hard to impossible to remove that sediment/debris.  Consider sediment collection in the design of the inlet locations.  If available, use an above ground system for the first 1-2 inches of storage, and send the drainage to the above-ground storage system for the small events, and overflow to the below ground systems for the extreme events.  That way, most of the items that cause chaos to underground detention systems (plastic cup lids, foam cups, plastic sacs, etc.) get trapped in the above ground pond that can be maintained.  I have found a reverse grade storm sewer between the above ground pond and the underground detention works well at keeping the floatables out, while allowing water to flow in.  It works even better if you have a wet pond for the above ground part with a large separation between inlets to the pond, and outlet to the underground detention.

There are lots of other things to consider, including what complies with the local regulations.  It is always possible to pay for for a system review by an independent engineer that practices in the specific community if you have specific concerns about whether a specific design will meet the needs of the owner.  Its no different than a second opinion from a doctor over a treatment process.

------------------------------
Dwayne Culp, Ph.D.
Culp Engineering, LLC
Rosenberg TX
(713)898-1977

Original Message:
Sent: 02-21-2019 18:08
From: Jesse Kamm
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

I have a facility owner that is interested to talk with other facility owners about their user experiences with parking lots designed to flood in intense storm events. Like most projects, they have quite a few compounding constraints and are looking at cost effective design alternatives to the fully contained UG detention system as currently designed. The CE of record has suggested a mix of the UG system and use of the parking area for 25 yr storms. I'm encouraged by the idea as I've seen projects throughout the western U.S. use this technique.

The owner will operate a religious facility and a day school and is curious if other owners with similar designs would do it again or if they are burdened by the occasional standing water in the parking areas. Are there any good resources or personal testimonies I can point them towards?

------------------------------
Jesse Kamm PhD, PMP, A.M.ASCE
Vice President of Construction Management
------------------------------

Jesse,

One-inch containment likely doesn't mean one inch of water on the ground (that you would have to walk through to get to your car).

DC

Per further details of the project, have infiltration tests been performed?  It appears that underground systems may not feasible because of probable soil conditions.  In addition, with the described flooding conditions care must be used to keep sediment laden floodwater from entering said systems.  This will undoubtedly cause premature failure.

If land is available, a train system of multiple BMPs is the best solution.  The use of low impact development will help to lower storage requirements.

------------------------------
John Wood
Pittsburgh PA
------------------------------

Original Message:
Sent: 02-25-2019 12:24
From: Jesse Kamm
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

Not really much of a nearby field available. It's a really interesting site to work on. A large portion of the property is within FEMA 100 year flood zone and therefore off limits. It's an old farm land in a historical part of TN, over time the surrounding land had been developed into single family housing and some of these developments have designed their overflow to shift onto this property. On top of that, the state/city is currently redesigning the ROW and took additional land in eminent domain. I agree with an earlier comment about the troubles with the underground systems over time thus why I'm liking the combined approach. I think I can get the stakeholder buy-in, but I also don't want to support anything that hurts the operational mission.

------------------------------
Jesse Kamm PhD, PMP, A.M.ASCE
Senior Vice President of Construction Management

Original Message:
Sent: 02-23-2019 08:43
From: James Mercier
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

Jesse, is there an adjacent playfield or lawn that could be used for floodwater detention?  City of Cincinnati has an extensive soccer field complex that is "unavailable" during flood events.

------------------------------
James Justin Mercier, P.E.
Life Member ASCE
Sr. Life Member IEEE
Austin Texas
512-442-4016

Original Message:
Sent: 02-22-2019 15:30
From: Jesse Kamm
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

Dr. Culp, This is very helpful. Thank you so much for the response. I will share this information with the client and the design/build team. I'd be interested to hear if anyone has operational use strategies in place for such facilities. It's one thing to get the design correct and another to advise the owner on the proper way to use and manage the systems as designed. I find expectation setting to be sometimes as challenging as the engineering problems themselves. For instance, perhaps there is a management plan the team can come up with for certain "triggers" to alert the facility managers to close off certain spaces when rain events are forecast.

------------------------------
Jesse Kamm PhD, PMP, A.M.ASCE
Vice President of Construction Management

Original Message:
Sent: 02-22-2019 12:16
From: Dwayne Culp
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

The nice  thing about religious facilities are that the parking lots are not occupied during all time periods, and that most people do not go to church during flooding events.  The bad thing about religious facilities is that they tend to be centers of safety and organization during natural disasters.  As I am from the Houston area, I have seen this happen many times.  Nothing worst for a parishioner to come into church with a dry car, and have to have it towed when they leave 2-hours later because it has 2 feet of water surrounding it.

I have designed parking lot detention.  When I do it, my rule of thumb is that 25% of the parking spaces need to be dry during the 100-year event, another 25% should be dry during the 25 year event, and the rest should not flood more than 9-inches during the 100-year event.  This keeps it out of most cars.   Lots of inlets are required to ensure that the water does not start accumulating above the surface before the underground system is filled.  This prevents the more-than occasional issue of standing water.

Underground systems will collect sediment and debris if you are not careful, and most systems are hard to impossible to remove that sediment/debris.  Consider sediment collection in the design of the inlet locations.  If available, use an above ground system for the first 1-2 inches of storage, and send the drainage to the above-ground storage system for the small events, and overflow to the below ground systems for the extreme events.  That way, most of the items that cause chaos to underground detention systems (plastic cup lids, foam cups, plastic sacs, etc.) get trapped in the above ground pond that can be maintained.  I have found a reverse grade storm sewer between the above ground pond and the underground detention works well at keeping the floatables out, while allowing water to flow in.  It works even better if you have a wet pond for the above ground part with a large separation between inlets to the pond, and outlet to the underground detention.

There are lots of other things to consider, including what complies with the local regulations.  It is always possible to pay for for a system review by an independent engineer that practices in the specific community if you have specific concerns about whether a specific design will meet the needs of the owner.  Its no different than a second opinion from a doctor over a treatment process.

------------------------------
Dwayne Culp, Ph.D.
Culp Engineering, LLC
Rosenberg TX
(713)898-1977

Original Message:
Sent: 02-21-2019 18:08
From: Jesse Kamm
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

I have a facility owner that is interested to talk with other facility owners about their user experiences with parking lots designed to flood in intense storm events. Like most projects, they have quite a few compounding constraints and are looking at cost effective design alternatives to the fully contained UG detention system as currently designed. The CE of record has suggested a mix of the UG system and use of the parking area for 25 yr storms. I'm encouraged by the idea as I've seen projects throughout the western U.S. use this technique.

The owner will operate a religious facility and a day school and is curious if other owners with similar designs would do it again or if they are burdened by the occasional standing water in the parking areas. Are there any good resources or personal testimonies I can point them towards?

------------------------------
Jesse Kamm PhD, PMP, A.M.ASCE
Vice President of Construction Management
------------------------------

Mr. Kamm, 

We recently ​completed a project where we decided to allow some partial flooding of the facility parking/cargo area under certain events. It was something we decided we could live with, but in reality it's a lot less practical than I expected. I wouldn't do it again if I could avoid it. It can be hard to explain to the end user that a certain area of the facility is meant to flood, with certain frequency, and become almost unusable. Even when it was discussed and it was agreed to during the design process.

I understand the logic your team is using since more than likely a large portion of the parking lot won't be used but 2 or 3 times a week but having to drive through 9" of water to pickup grandma from the church door is not going to be fun and it's going to lead to angry phone calls from the church's facility committee chair. Your mileage may vary!

------------------------------
Jose De Jesus
Tampa FL
------------------------------

Original Message:
Sent: 02-21-2019 18:08
From: Jesse Kamm
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

I have a facility owner that is interested to talk with other facility owners about their user experiences with parking lots designed to flood in intense storm events. Like most projects, they have quite a few compounding constraints and are looking at cost effective design alternatives to the fully contained UG detention system as currently designed. The CE of record has suggested a mix of the UG system and use of the parking area for 25 yr storms. I'm encouraged by the idea as I've seen projects throughout the western U.S. use this technique.

The owner will operate a religious facility and a day school and is curious if other owners with similar designs would do it again or if they are burdened by the occasional standing water in the parking areas. Are there any good resources or personal testimonies I can point them towards?

------------------------------
Jesse Kamm PhD, PMP, A.M.ASCE
Vice President of Construction Management
------------------------------

Mr. De Jesus, 
Thank you for the response. That's very helpful and exactly what I was interested to hear.

------------------------------
Jesse Kamm PhD, PMP, A.M.ASCE
Senior Vice President of Construction Management
------------------------------

Original Message:
Sent: 03-05-2019 11:32
From: Jose De Jesus
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

Mr. Kamm,

We recently ​completed a project where we decided to allow some partial flooding of the facility parking/cargo area under certain events. It was something we decided we could live with, but in reality it's a lot less practical than I expected. I wouldn't do it again if I could avoid it. It can be hard to explain to the end user that a certain area of the facility is meant to flood, with certain frequency, and become almost unusable. Even when it was discussed and it was agreed to during the design process.

I understand the logic your team is using since more than likely a large portion of the parking lot won't be used but 2 or 3 times a week but having to drive through 9" of water to pickup grandma from the church door is not going to be fun and it's going to lead to angry phone calls from the church's facility committee chair. Your mileage may vary!

------------------------------
Jose De Jesus
Tampa FL

Original Message:
Sent: 02-21-2019 18:08
From: Jesse Kamm
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

I have a facility owner that is interested to talk with other facility owners about their user experiences with parking lots designed to flood in intense storm events. Like most projects, they have quite a few compounding constraints and are looking at cost effective design alternatives to the fully contained UG detention system as currently designed. The CE of record has suggested a mix of the UG system and use of the parking area for 25 yr storms. I'm encouraged by the idea as I've seen projects throughout the western U.S. use this technique.

The owner will operate a religious facility and a day school and is curious if other owners with similar designs would do it again or if they are burdened by the occasional standing water in the parking areas. Are there any good resources or personal testimonies I can point them towards?

------------------------------
Jesse Kamm PhD, PMP, A.M.ASCE
Vice President of Construction Management
------------------------------

Thanks for all the useful feedback everyone. I wanted to provide some conclusion by sharing the strategy we ultimately decided upon:
We took a four fold approach: (1) diverting some of the water from the new roof to the an existing detention basin, (2) creating a new detention basin near an expanding roadway with deep encapsulating retaining walls and an architectural/hardscape element forward facing to the public, (3) converted the parking lot islands to "rain gardens" with an underground diversion system, and (4) permeable paving with parking lot detention in limited areas.

Using this combined strategy we were able to reduce the site budget by nearly 65%. Thanks again.

------------------------------
Jesse Kamm PhD, PMP, A.M.ASCE
Senior Vice President of Construction Management
------------------------------

Original Message:
Sent: 03-08-2019 11:12
From: Jesse Kamm
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

Mr. De Jesus,
Thank you for the response. That's very helpful and exactly what I was interested to hear.

------------------------------
Jesse Kamm PhD, PMP, A.M.ASCE
Senior Vice President of Construction Management

Original Message:
Sent: 03-05-2019 11:32
From: Jose De Jesus
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

Mr. Kamm,

We recently ​completed a project where we decided to allow some partial flooding of the facility parking/cargo area under certain events. It was something we decided we could live with, but in reality it's a lot less practical than I expected. I wouldn't do it again if I could avoid it. It can be hard to explain to the end user that a certain area of the facility is meant to flood, with certain frequency, and become almost unusable. Even when it was discussed and it was agreed to during the design process.

I understand the logic your team is using since more than likely a large portion of the parking lot won't be used but 2 or 3 times a week but having to drive through 9" of water to pickup grandma from the church door is not going to be fun and it's going to lead to angry phone calls from the church's facility committee chair. Your mileage may vary!

------------------------------
Jose De Jesus
Tampa FL

Original Message:
Sent: 02-21-2019 18:08
From: Jesse Kamm
Subject: Owner/User Experiences with Parking Facilities Designed for 25 Year Storm Detention

I have a facility owner that is interested to talk with other facility owners about their user experiences with parking lots designed to flood in intense storm events. Like most projects, they have quite a few compounding constraints and are looking at cost effective design alternatives to the fully contained UG detention system as currently designed. The CE of record has suggested a mix of the UG system and use of the parking area for 25 yr storms. I'm encouraged by the idea as I've seen projects throughout the western U.S. use this technique.

The owner will operate a religious facility and a day school and is curious if other owners with similar designs would do it again or if they are burdened by the occasional standing water in the parking areas. Are there any good resources or personal testimonies I can point them towards?

------------------------------
Jesse Kamm PhD, PMP, A.M.ASCE
Vice President of Construction Management
------------------------------