Setbacks more stringent then the IDNR requirements have been established by Story County to enhance water quality protection. The current setback requirements for the IDNR are shown in parentheses in the table below. The more stringent setbacks apply to all new septic installations in Story County installed after January 1, 2021. Owners who have limited options for system placement may request, in writing, a variance for this requirement to the Sanitarian. Appeals of the Sanitarian's decision will be heard and voted on by the BOH.
Table 1
Closed Portion of Treatment System * | Open Portion of Treatment System**
| |
Private water supply well | 50 (50) | 100 (100) |
Shallow public water supply well *** | 200 (200) | 400 (400) |
Deep public water supply well **** | 100 (100) | 200 (200) |
Groundwater heat pump borehole | 50 (50) | 100 (100) |
Lake or reservoir | 50 (50) | 100 (100) |
Stream (Class Al, A2, and A3) or pond | 25 (25) | 50 (25) |
Edge of road ditch | 10 | 10 |
Edge of drainage district ditch | 25 (10) | 50 (10) |
Dwelling or other structure | 10 (10) | 20 (10) |
Property lines (unless a mutual easement recorded) | 10 (10) | 10 (10) |
Other type of subsurface treatment system | 5 (5) | 10 (10) |
Water lines continually under pressure | 10 (10) | 10 (10) |
Suction water lines | 50 (50) | 100 (100) |
Foundation drains | 10 (10) | 10 (10) |
Subsurface drainage tiles | 25 (10) | 50 (10) |
* Includes septic tanks, aerobic treatment units, fully contained media filters, holding tanks, and impervious vault toilets.
** Includes subsurface absorption systems (secondary and tertiary treatment), mound systems, intermittent sand filters, constructed wetlands, open bottom media filters.
*** Shallow well means a well located and constructed in such a manner that there is not a continuous layer of lowpermeability soil or rock (or equivalent retarding mechanism acceptable to IDNR) at least 5 feet thick, the top of which is located at least 25 feet below the normal ground surface and above the aquifer from which water is to be drawn.
**** Deep well means a well located and constructed in such a manner that there is a continuous layer of low-permeability soil or rock at least 5 feet thick located at least 25 feet below the normal ground surface and above the aquifer from which water is to be drawn.