Subdivision Grading Plan - Pad on lots

[Chaznsc]

Normally my plans for a subdivision do not extend beyond the right of way line, however, I have a client who likes an incorporated lot grading on his plans. What I have done to date is grade a corridor surface, then use feature lines to raise the front lot line 2 feet to the MBL, then offset that line to create a front to back level area. The side to side slope is a result of the road grade and the aforementioned feature lines. The client wants us to grade each lot with a "pad" for the home/yard area. Basically a flat rectangle within the lot limits as per the attached JPG. My thoughts are to create another feature line on top of the lot with each corner set to level. My results were mixed with some contours becoming confusing looking.  Is there a better way of doing this? 

Thank you for your time. 

 

[Neilw_05]

That is basically how it is done. There should be some slope on the pads if they are not going to be developed for a period of time. That can be done with a high point. You will need to consider drainage between the lots as well. Typically you will have a drain swale that directs the drainage toward the street or towards the rear yard, depending on the overall slope of the site. You also need to consider what happens in the rear yards so you don't have trapped run-off. There may need to be a drain swale to carry that drainage to daylight at some point. Getting the earthwork to balance is another requirement. If you build a dynamic model you can balance the site by adjusting the road profiles and the lot pads update accordingly. A cut/fill map helps to see where to make the adjustments.

[Neilw_05]

One more factor to consider is the slopes between the pads and street. You don't want steep driveways to the lots.

[Chaznsc]

Quote: “If you build a dynamic model you can balance the site by adjusting the road profiles and the lot pads update accordingly. A cut/fill map helps to see where to make the adjustments.”

I hate to churn this one again, but here goes. In Neil’s comment, he mentions a dynamic model. How is that accomplished outside the corridor? 

thank you for reading or even rereading this thread 🙂

[Joe-Bouza]

If you are looking for a hands off solution you will need more programing. Here is how I would approach it 

build your road corridor to the front lot line.

assume a limit point at the rear; lets use the property line

create an alignment of the PL and sample EG

Create an assemble of just a MP

In the corridor surface properties (corridor surface command not prospector) add the FL from mark point to the surface definition

add the PL to the corridor as a base line assign the EG profile and the MP assembly

add your pads FL assign as  baseline with the MP assembly

tweak the FFE and grade away accordingly

add more FL as baseline with MP to define swales and or ridges

this will be quite dynamic

adjust away. checking cut fill as you go

tip be vigilant about naming the FL with intuitive name PAD_LOT01, SWALE_LOT25....

[Neilw_05]

In theory you would create a drape surface that slopes at X% from the edge of the road corridor to the rear of the lots along the road. Then you would create an edge of the lot pads that are X ft offset to that drape surface on the uphill side. That establishes the elevations and slopes of the pads. The perimeter of the pads need to be tied to the elevations of that pad edge, so you can end up with a pad that is evenly sloped towards or away from the road, depending on the overall drainage pattern. The process is too complex to explain textually. Also there is no way to create a dynamic model that responds to changes in the road centerline profiles that I have found. That is why I have reverted to another product that is more capable in that regard. 

[Neilw_05]

In theory you would create a drape surface that slopes at X% from the edge of the road corridor to the rear of the lots along the road. Then you would create an edge of the lot pads that are X ft offset to that drape surface on the uphill side. That establishes the elevations and slopes of the pads. The perimeter of the pads need to be tied to the elevations of that pad edge to establish a pad that is evenly sloped towards or away from the road, depending on the overall drainage pattern. The process is too complex to explain textually. Also there is no way to create a dynamic model that responds to changes in the road centerline profiles that I have found. That is why I have reverted to another product that is more capable in that regard. 

[Chaznsc]

@Joe-Bouza 

What is/are the MP & FL you refer to? 

[Chaznsc]

I dont know when you guys sleep but thank you for the input. 

[Joe-Bouza]

MP= Mark Point Sub assembly

FL =Feature line

[Chaznsc]

Thank you 😉 I would have NEVER cracked MP!