HomeMy WebLinkAbout1997-11-20 NAC File Memorandum • .
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MEMORANDUM
TO: File
FROM: Bob Kirmis
DATE: 20 November 1997
RE: Oak Park Heights - Annexation
FILE NO: 798.04 - 97.19
This memorandum is intended to document a conversation I had on this date with Mr. Mark
Wespetal of the MPCA Division of Water Quality.
had specifically contacted the MPCA to obtain any applicable information regarding the
Agency's "position" on communal sewage treatment systems. In my conversation with Mr.
Wespetal, the following points were made:
• The PCA has no "official" position regarding communal versus individual
drainfields.
• System type preference depends on hydro - geology of the area. Findings of study
should dictate preference
• If determination is made that a single, high concentration of effluent will not
negatively impact the ground water supply, a communal system is generally
preferred. Placement of the drainfield is a key issue.
• If a high concentration of effluent is a problem (typically associated with communal
systems), a dispersement of drainfields is generally preferred (i.e., individual
systems).
• If urbanization is planned in the near future, a communal system is generally
preferred (assuming no adverse environmental impacts).
• •
In this regard, a communal system offers advantages of in- ground pipes and the likely
avoidance of individual property disputes.
Attached to this memorandum is supplemental information pertaining to this matter which
has been supplied by Mr. Westpetal.
pc: Scott Richards
2
PCR WATER QUALITY NSC Fax :612-282-6247 Nov 20 '97 13:14 P.01
To v b, ken, s From wes Agency • November 20, 1997
Co./Dept.. Co. /voc, G
Pno�te # Phone # r� p G 3 � ;
Fax# S p c 8-3 7 Fax# o� DRAFT
Collection Systems and Large
Drainfields
chance increases as system density
There has been a interest in the past few years to increases.
develop new subdivisions with central collection
of the sewage with treatment provided by one 3. A large drainfield, which is permitted by the
large septic tank/drainfield system. This method agency, would require the system to be
is in lieu of the standard practice of developing operated and maintained by a qualified
lots with tb ability to treat the waste with sewage operator. This would result in proper
treatment systems Located on each lot. This fact maintenance and proper disposal of the
sheet will highlight the advantages and septage.
disadvantages of collecting the sewage with
treatment by one large drainfield. 4. A large system alleviates the aggravation
caused by failures of the individual systems
Advantages: in the future. This aggravation is two fold.
The first aggravation is the nuisance the
1. If hookup to a municipal treatment plant is failures cause and the enforcement effort
anticipated in the future, a central collection required to bring the individual systems into
system appears to be advantageous. This compliance. In some situations suitable soils
advantage is that all the homes are plumbed or land area may not be available to upgrade
for central collection, with their building the system on a lot. This condition causes
sewers heading in the proper direction at the the second aggravation. In this case, a push
appropriate elevation. Collection with a for a collection system is desired by those
large drainfield also avoids the tearing up of individuals with failed systems. A
the street or other areas in order to place the collection system is very expensive and
sewer pipe sometime in the future. those in the subdivision with non - failing
systems (especially those with newly
2. All drainfields, regardless of size, produce constructed systems) do not want the
contaminant plumes in the groundwater. additional, and unneeded expenses of
Individual systems produce small abandoning their compiling system and
contaminant plumes and large drainfield hooking -up to the collection system. This
produce bigger plumes. It is possible that a situations can be quite contentious and could
large system can lessen the impacts to be avoided if collection is used from the
drinking water wells if the system is placed start.
in a groundwater discharge area.
5. The user fee collected for system for
3. For individual systems, wells and operation and maintenance could include
drainfields are in closed proximity to each REPLACEMENT costs. In effect, this
other. Therefore there is the possibility that could be a forced savings plan to replace the
the groundwater plume from the drainfield system when needed..
may be within a well capture zone. This
Thls fact sheet can be made available in other formats, such as Braille, Large type or audio tape upon request.
Printed on recycled paper with at least 10% fibers from paper recycled by consumers.
PCR WATER QUALITY NSC Faxi612- 282 -6247 Nov 20 '97 13:15 P.02
Minnesota PoHulk Control Agency •
6. As part of a state permit, the operator must
identify and eliminate discharges of non- MN Rule Chapter 7080 (Individual Sewage
domestic wastes. There is no check or little Treatment Standards) and Collection Systems
education of owners of individual system to
eliminate these discharges. MN Rule Chapter 7080 (7080) standards
which are applicable to collector systems
Disadvantages: are:
1. Large systems which are designed to treat I. Chapter 7080 classifies a Collection System
greater than 10,000 gallons per day as an Alternative System. According to
(roughly equivalent to 20 homes) must be 7080, an Alternative System can only be
permitted by the agency There are used if a standard system camlot be installed
additional costs with the design, permitting, or is not the most suitable treatment
monitoring and operation of an agency , (7080.0910 subp. 3).
permitted system.
2. The Collection system section of the rule
2. The agency permit requires groundwater (7080.0910 subp. 3. L) states that collection
monitoring to ensure that the system is systems may be employed where site and
operating as designed and that the system is soil conditions do not allow for final
meeting groundwater standards at the treatment and disposal on an individual lot.
property boundary. Meeting drinking water
standards at the property boundary may 3. Chapter 7080.0300 subp. 2. states that all
require a pre - treatment device, the purchase lots created after January 1, 1996 must
of land downgradient of the system (for provide one additional soil treatment site per
dilution of contaminants) or siting of the lot.
system in a groundwater discharge area
which includes the groundwater discharge 4. 7080.0030 subp. 2. requires justification of
point. the need for a large drainfield.
3. No ground water monitoring would be An attempt will be made to interpret the above
required for a large system if it is designed requirements when dealing with new
to treat less than 10,000 gallons per day. developments.
This could be problematic if the drainfield is
located in a groundwater recharge area and The provisions in items 1 and 2 were
/or the residents have shallow wells. This contained in the original sewage treatment
condition could be avoided if the local rule, WPC -40. The Statement of Need and
permitting authority would follow and Reasonableness (SONAR) prepared for WPC -
enforce the agency's requirements for 40 does not mention the applicability of the
permitted systems. alternative standards for new developments.
The SONAR seems to be addressing situations
4. Septage produced under a permitted system of existing lots with siting or soil problems,
is regulated the same municipal bio- solids and does not imply that individual systems are
from a ?OTW. preferred over collector systems. The
SONAR (pages 136 and 137) mentions that
5. The residents would have organize for these provisions were added to provide
system operation and maintenance. flexibility for local units of government in
PCA WATER QUALITY NSC Fax:612- 282 -6247 Nov 20 '97 13:15 41.4 Minnesota Pofun Control Agency •
adopting and using other systems for
treatment and disposal.
Item 3 - the provision to require two ISTS
sites per lot - was only meant to include those
lots which were developed without collection
services. For example, the agency had no
intention of requiring two sewage treatment
sites on a city lot which is to be connected to
central collection.
Item 4 - the justification for a large system -
is due to the treatment concerns with large
drainfields for nitrogen, chlorides and possibly
some organic chemicals. This justification
consists of a study of the hydogeologic
conditions and whether the system can meet
drinking water standards. If this justification
proves that the system can meet standards,
then it can be issued a permit by the agency.
Conclusion:
The decision on the use of individual systems
verses a collection system should be based on
protection of the groundwater. The agency feels
that adequate groundwater protection can occur by
following MN rule chapter 7080 for individual
systems, or meeting agency permit requirements
for a large drainfield. The decision on which to
used should be based on local factors such as the
proposed density of individual systems, individual
well placement and depths (or use of central
water), soil types, topography, and hydrogeologic
conditions.
More information
If you have questions, please contact the MPCA's
ISTS Unit at (800) 657 - 3864.
fp/ section .np /ists /factshts /collec. doc