Health Department Policy and Septic Design

[Stuart Meade]

My comments are partly in response to Toxic Avenger's post:
http://www.septicdesign.com/forums/index.php/topic,41.0.html
As a designer, I’d like to chime in regarding residential septic design.

We all know that CAD prepared septic drawings look great but that (of course) doesn’t mean that they are accurate or useful.

A comprehensive design drawing with accurate measurements (including elevations) is necessary to get accurate bids from excavators and provides for a seamless installation.  It should also be required by all health departments before a permit is issues.

Unfortunately,  Health Departments, wanting to “get tough on drawings” and increase the accuracy and effectiveness of drawing submissions often misguidedly fall into the “topographic trap”, (that is... requiring topography). 
 
Topography (or contour) lines on a drawing represent specific elevations.  They are helpful in illustrating general information regarding a site’s amount and direction of slope.

The problem is that topography, just like that fancy CAD drawing sure looks good on paper, but things aren’t always as they seem.
Topography is generated by software that utilizes field elevation data often shot in 15’ – 30’ grids.  The software sees only the points where the actual shots were taken and estimates the topography in between these points.  This is why 1.0’ topography is often in error of  2”-6” (and this is assuming the field data is correct).

Let me introduce you to the armchair engineer.  The armchair engineer loves topography.  It enables him to design septic systems without having to worry about rain, ice, snakes or ticks because he designs the whole thing from his comfy office chair.  He doesn’t go on-site to take elevations or mark the trenches.  He says marking trenches is the responsibility of the excavator.  He acquires a topographic survey (usually from someone else) and cranks out his “design”. Presto!

You ask, “How can he lay-out a 12” maximum trench system by simply referencing a marginally accurate topographic survey that's incorrect?”  The answer is…  He can’t!

His plans are both costly and worthless (not a good combination).  Unfortunately, these plans are sometimes approved by well-meaning but inexperienced health departments.  The excavator is then forced to redesign the system himself (in the field) before he installs it. 

A better way is to require elevations of the actual system (i.e. existing grade along each trench, the house sewer elevation,  tanks and trench bottom elevations, etc).
Be sure to reference your elevations off a local bench mark (or establish your own).

Arrows showing the direction of slope can be added to the design to supplement the system elevations. 
The system must be marked on-site.  This allows the Health Department to compare the paper design to the site itself.  Some health departments even confirm the plan’s elevations with their own laser levels!   
Trenches that are marked on-site also allow the excavator to install the system quickly and efficiently.

Some Health Departments require that only professional registered engineers produce the drawings.  This policy is a dream comes true to the armchair engineer!
Again, the well-meaning health department forgets that septic design is not rocket science.  Creating a successful design requires good site measurements (including elevations) and translating that information onto a scale drawing and comprehensive septic design.  Of course, familiarity with septic systems comes in handy too. 
 
By requiring that a certain person(s) design the system, they are locking other capable people out of the process including the installer himself (who usually has much more experience with septic systems than the registered engineer does).

County Health Departments in Indiana are all-over-the-map on this issue. Some allow anyone to produce the drawing (including the homeowner) while others require a registered engineer.  Some even only allow the person installing the system to draw the design!
 

Let me be clear.  I am not demonizing registered engineers.  There are plenty of them that do great septic design work.  My beef is not with all of them .  It’s only with the armchair variety that is enabled (and propped up) by flawed  health department policy. 

When setting new policy, regulators need to be extra careful when making a decisions regarding septic system requirements.
I believe that requiring topography can actually be counter productive and thus bad policy.  Furthermore, if someone other than a registered engineer has the knowledge, equipment and ability to design a septic system, why not let them?
Denying these folks works against the best interest of everyone involved. 

That was a long post!

I'm interested in your thought...

Stuart

[Toxic Avenger]

Just so folks don't think I'm talking out of ignorance here, I worked 6 years as a land surveyor and CAD drafter doing all kinds of surveys (ALTA, topo, route, boundary, mortgage, etc.).  And have worked along side professional engineers, architects, surveyors and drafters in the process.  I have seen the ALL the benefits AND downfalls of "professionally engineered" drawings.

Today, I work as a regulator/inspector at the government level, where to date I have dealt with literally 35-40 different septic installers, several soil scientists, a few professional septic designers, and countless property owners.  I own my own property with a septic system also.  I have not worked as a professional septic installer, but I have installed a septic system with my own hands from start to finish. 

While you are right, Stuart, in describing how drafting software "creates" contour lines, I do have to disagree on the value of it.  You see, the accuracy of computer generated contours all depends on how DENSE your topo was in the field.  In other words, it all depends on how close each of your grade shots are to one another.  A grid with grade shot every 50 feet is not going to create as accurate a picture of what the ground is really doing compared to a grid with grade shots every 10 feet. 

Furthermore, just having ONLY contour lines on a drawing is NOT enough.  Designers should also show each individual grade shot with it's relative elevation (in comparison to an onsite temporary benchmark, which should also be shown on the drawing).  The contour lines are merely a visually representation of the general direction of slope onsite, which gives the designer, installer, and regulator an idea of how to orient the septic field/mound.  Show individual grade shots is still more important however, because they are an exact measurement of the relative elevation at that exact spot in the real world.  So, yes, if people depend too much on just contour lines, then there could be problems when actually doing the installation of the septic system. 

My main point from my earlier post was the lack of effort I have seen from some septic installers in the design of septic systems.  Yes, if the guy installing the system also designed it, then he may have several things floating around in his head, BUT that does not mean they should not be put down on paper in an accurate and neat way!  I never said "engineered" drawings should be required.  I said they are usually superior designs to ones done by some installers because they LOOK professional and most of the time show more detail and accuracy.  Not always, but most of the time.  I have sent back MANY a drawing to a professional designer/engineer because they did not show enough detail, but I have never had to send on back because I couldn't read it. 

All good designers do at least these two things: 
1.  Get more than just the bare minimum of information in the field and;
2.  Submit a design showing ALL the necessary information, including grade shots, plus any additional info specific to a site that would influence the design of the septic system. 

[Stuart Meade]

Toxic A,

Don't worry, we are in total agreement on this issue!

I didn’t mean to imply that you were suggesting that drawings from registered engineers should be required.  Sorry, if my post implied that.
I don’t see anything in either or your post that I disagree with.

Like you, I have also worked both sides of the septic fence.  Having completed septic design in 30 counties in Indiana, I am constantly amazed at how significant policies change from county to county.  Some "don't want no fancy drawings" while some "don't like complicated pumped systems".

Some counties require contours but are NOT requiring grade shots over (and throughout) the system.
This enables the armchair engineer that I mentioned earlier.  His  plans are worthless and too often the Health Department doesn’t realize it.

You are correct about grid spacing and contour accuracy.   An even more accurate way is to supplement the grid shots with "critical point shots".  Those are where the slope changes.  This allow the computer to draw more accurate lines.  Some can be very accurate.  The problem is that contours accuracy is difficult for Health Departments to confirm.  Therefor, anything is acceptable.    Unfortunately, the availability of online contours (from GIS systems) are giving these guys an additional  source of even more unreliable topography for their designs.  Hopefully, the Health Departments will wise up.

A system should be able to be installed just like the design shows.   If well prepared, a design is a great planning tool for the builder, homeowner, basement forms concrete guy, excavator and health department.   
I appreciate Health Departments who are clear and consistent with their requirements.  Consistency makes things easier for everyone involved.

Stuart Meade