Multi-Family Site Development

[jsullivan52]

I am working on 18 Ac. site with 30-40 feet of variation in elevation beginning with a valley running through the site and being perpendicular to the road, and then rising upward toward the side property lines. On one side of the property (prior developed) the elevation falls 20-25 feet immediately and on the other sides the slopes are maintained and steadly increasing. The grades near the rear and side property lines run upward of 12%.

My question is what are some guidelines (i.e. min/max slopes, buffing features, etc.) for creating a grading plan for a site to be sold for multi-family use?

All thats being done at this point is grading (i.e. no roads, utilities, structures, etc.)

The owner wants to get the site to be "saleable"!!
(what is saleable?)

Thanks for any advise and input!!

 

[GoldDredger]

The first thing that comes to mind, as I have a commercial site with a channel down the middle, perpendicular to the road, is the drainage. There is probably an existing culvert under the road. I would want to determine what the 100 year WSE is of the channel (Ie, how much upstream flow coming in, what are the constraints of the culvert, what sort of headwater can you expect when developed, and potential from (future) developed runnoff upstream. Are you planning on keeping the channel or going underground. (If I am correct on this being a drainage channel)

Maybe I'm even ahead of myself. How about the first second thing that comes to mind, is what sort of density and layout do they want with the site? What size are the lots, have they given you a concept plan at least? (Quarter acre lots, half acre, etc)

As far as max and minimum slopes for the road, what part of country are you in? Does it freeze in the winter, so you wouldn't want steep roads? I wouldn't go over 12% slope on any roads, and use vertical curves whenever you have an algebraic difference of 2% between positive/negative slope transitions.

You could consider retaining walls between lots, side or front to back. Then accomplish your steeper road slopes between the lots.

Do you have to match grades at the perimeter of the property, or can you use retaining walls?

Be aware not to paint yourself into a corner by with future gravity utilities during your rough grading. (Ie, know your sewer connection elevation)

Sounds a little suspect to me. Why perform rough grading without an idea of what your site layout would be. Have to push dirt around, set up erosion control measures, do a SWPPP. What is the property zoned for?

Anyway, just kindof a rambling post before having 2 cups of coffee. Hope something up there is nominally helpful.

Dredger

 

[jsullivan52]

We do have to maintain the perimeter slopes. Well I say maintain, regs just say a nice transition. the swale or ditch is really just a natural valley that begins in the front middle of the property at a pipe then extends toward the center of the property and from there its all uphill. All the water from the whole site is funneled to street storm sewer inlet located at the front-middle of the property.

The owner is not building on the property. He just wants to get it to a point where it will be most appealing to a potential developer. The property is zoned Multi-family and will most likely be used as an apartment complex, and I don't foresee the property being split up into multiple tracts.

 

[GoldDredger]

I would propose to the owner that you create a rough grading and erosion control plan. If the survey is old, I would propose a new one with spot shots at least on a 50' grid and a more for identifying special features (utilities, anomalous grades, power poles, etc)

On the rough grading plan, I would propose a 3:1 or 4:1 slope down and in from the property boundaries. Use those excess spoils to flatten the middle parts of the site.

If there are driveways adjacent too, or across from the site, keep in mind future driveways will have a separation requirement (sides), and usually will have to be located directly across from existing driveways across the road. Find out who maintains the road, county or your state highway department.

In your specifications be sure to call stripping and stockpiling of topsoil, to be spread back over the site after the rough grading. Also identify hydroseeding with something appropriate to your area.

If it's not your survey and the owner doesn't want another, then put disclaimers on your contract and plans that these elevations are based on provided information.

Recommend a geotechnical investigation be performed as well. If they won't pay for that, be sure to protect yourself from problems that could arise when rough grading. High water table, rock below subsurface, unsuitable fill material encountered. As a mater of fact, on your plans I would probably say placement of fill based on geotechnical recommendations.

Be sure to list a hearty number of exclusions to your contract. No environmental testing, not responsible for SWPPP, inspections, testing, zoning services etc. Also make it clear that this is being done without the benifit of a concept plan.

On your erosion plan have stabilized construction entrance, silt fence, straw wattles or bales. Show rough grade contours on the grading plan.

That's about all I can think of, anyone else have any ideas?

Dredger

 

[civilperson]

Waste of time and money! The site is salable as is, let the next owner can apply whatever criteria is best to produce a grading plan that meets the specific development plan.

 

[jsullivan52]

Kinda what I thought, but the client is dead set on getting what he wants. I think I am just going to give a rough grading plan by giving some limiting slopes criteria and enough information to maintain drainage as it is currently and just let the contractor go at it. Would this be considered acceptable practice?

 

[msucog]

i wouldn't let the contractor do much of anything on his own...it'll chew through a bank account very quickly.

i'd leave the site untouched and let the next guy worry about due diligence exploration and designing the site. the more you disturb the site, the more potential red flags may become obvious to the buyer which equates to a lowered selling price or busted deal. plus, it sounds like you may have some permitting issues that need to be addressed prior to moving dirt...so let the developer deal with this once they develop the site.

i do quite often see some conceptable plans drawn up to entice potential buyers but again, i'd suggest not touching the site unless you're going to completely develop the site.

 

[GoldDredger]

If Jsullivan's client wants engineering drawings for the site, then Jsullivan should provide them too him. Who knows what that client is thinking? I wouldn't presupppose to know what is a waste of time or not for this client, or maybe his potential buyer.

You might warn the cliet of some of the pitfalls of early grading the site. (maybe he already knows this, wants it anyway).

No reason Jsullivan should talk himself right out of doing the design. Maybe that client would say 'fine, I'll just find someone else to do it.'

 

[jeffcivil2]

It's better to not do something you know isn't in the clients best interest. Just say no. You'll have to go through the whole permitting process with erosion control at the local and state level if you do it. I can understand if you're small-time and looking for a contract, but if you are you'll never get big time doing business this way.

Cheers,

http://www.civiltips.com

 

[GoldDredger]

I agree somewhat with Jeffcivil's post above, however, you have to be careful about assuming you know or don't know is in your clients best interest.

Suppose this client wants a rough grading plan as a selling point for a potential buyer. Suppose the client has a deal in the works with a buyer to rough grade the site and I'll buy it, because my financing is dependent upon it.

I read this today in a Civil Engineering publication, I thought it was poignant for this post. Let me paraphrase the article, which quotes Canon 1 of ASCE Code of Ethics.

"Engineers shall approve only those design documents.....are safe for public health and welfare in conformity with engineering standards"

"Engineers shall advise their clients when, as a result of their studies, they believe a project will not be successful."

"Nowhere in these cannons are engineers prohibited from participating in a project if they believe it to be poor (public) policy or not in the (publics) clients best interest"

"In conclusion, ethical standards clearly allow an engineer to participate in project they consider poor public policy or not in the publics best interest, as long as the engineers beliefs are not so strong as to create a conflict of interest that may affect the quality of work on the project"

-Texas Civil Engineer, Summer 2008, Volume 78, No. 3, by Clay A. Forister

 

[jsullivan52]

Thanks for the replies!!

I have found out a little bit more of the our clients intentions. He has this site that as i mentioned before, that is roughly 18-20 acres of what use to be woodland... prior to consultanting with us he cleared the site without any permits or city/state approval. SOOOO, as I understand the situtation a NPDES permit is warrented and a dentention pond or some form thereof will undoubtly be needed.

The purpose of the clearing he says is he is selling half of the site (the high side or hill), but he wants to move some of the dirt off that portion before he sells so that he will not be left a huge gully and have to buy dirt later to develop or sell the rest of the site.

The question I have now is... How do you go about designing a detention pond for this situation? Is one pond for potentially two or three parcels of land the norm or would you split the property up into three sections and design your ponds for each future parcel? Keep in mind that these parcels will (as expected by the client) be apartment complexs.

I appreciate all of you're help and guidance.

 

[GoldDredger]

You should probably first determine if detention is required for the ultimate development, or if this is just a sedimentation pond for the erosion protection.

If it is the later, then you can probably just construct a series of small check dams to slow the water enough for sediments to settle out.

If it is for detention, then determine the requirements of the governing agency. Runnoff coeficients (pre vs post)and rainfall intensity for various duration storms. From that you can determine pre vs post runnoff and size your pond. (I presume you'll be using the rational formula?)

It will be much more efficient to have one pond for the whole site in my opinion. However, then one parcel gets saddled with detention for the whole site, reducing the avialible land. If you do use one pond, and the land is separated into parcels, then there will be a number of mutual access and utility easements will be needed. Along with a shared maintenance agreement for the pond (unless, the pond must be public, as some juristicions require?)

 

[civilperson]

You are teaming up with a incompetent boob or worse,(a scoffaw). Lack of permits and plans prior to clearing the site lends credence to the possibility of erosion run off on to neighboring land and subsequent lawsuits. You now have criteria to design a grading plan but I would recommend that you collect your entire fee in advance for such a client.