You and Your Septic System Part IV

Neighborhood Cluster Wastewater Systems

by Ted Moore, P.E.

Note: This is the fourth in a series of articles. The first article describing conventional on-lot septic systems appeared in the October, 2010 HALO newsletter, the second article described septic system maintenance, troubleshooting and upgrading a failing septic system, and the third discussed advanced treatment wastewater systems. Opinions expressed in this article are those of the author and do not necessarily reflect Municipal policy.

Background: As discussed in the previous article, advanced treatment wastewater technology provides a useful on-site alternative for many lots that cannot accommodate a conventional on-site wastewater disposal system. However, due to totally impermeable soils, very shallow bedrock or groundwater, or particularly severe separation distance constraints, some lots simply cannot accommodate any kind of on-site wastewater disposal system. Also, long-standing municipal regulations do not allow installation of a holding tank in order to build a residence on a vacant lot. Thus, without the ability to connect to the public sewer system, residentialy-zoned land such as this cannot be developed at all. But wait, there is another alternative. As in most situations, there is always another alternative; it is just a question of whether or not the alternative is a good idea.

Anchorage Comprehensive Plan: In order for the Hillside to accommodate the share of anticipated population growth called for in the Anchorage 2020 Comprehensive Plan, many of the remaining, un-subdivided homesteads, mostly located in alpine areas bordering Chugach State Park, will need to be developed. Much of the land in these homesteads is characterized by steep slopes, shallow bedrock and/or marshy bogs; most of which is unsuitable for on-site wastewater system development. However, within those areas scattered pockets of terrain more suitable for subsurface wastewater disposal sometimes exists. Thus, if appropriate design and operational criteria can be met, a neighborhood cluster wastewater system could be developed on the more suitable terrain, which would treat and dispose of the wastewater generated at homes located on lots with less suitable soils.

Hillside District Plan:
The Hillside District Plan, which was adopted by the Municipal Assembly in the spring of 2010, specifically calls for the development of neighborhood wastewater systems (cluster systems) on the Hillside. Unfortunately, for reasons that are not clear to the author, neither the adopted plan nor earlier drafts of the plan are presently available. (Note from web master: Link to Hillside District Plan).

What are cluster systems?
While more complex than individual on-site wastewater disposal systems, cluster wastewater system technology is far from rocket science; many residential developments around the country are currently served by cluster wastewater treatment and disposal systems. The technology in many cases is very similar to individual on-site systems, just scaled up to accommodate larger flows. In some cluster wastewater systems each home has its own individual septic tank, the clarified effluent from which is then pumped to a community-scale advanced treatment tank before flowing into a surface or subsurface disposal system. Many of the same companies that market Advanced Treatment Systems for individual lots also market scaled- up treatment systems designed to accommodate groups of residences. The only significant negative issues associated with cluster wastewater systems are found in the areas of maintenance, operation and administration.

Maintenance and operation of individual on-site septic systems: With your own personal on-site wastewater system, you (the property owner) are solely responsible for its construction, maintenance, operation and eventual replacement. If you abuse the system, causing it to fail, you personally face immediate consequences that are unquestionably your responsibility to deal with. Even without a regulatory authority looking over your shoulder, sewage backing up into your house or spewing into your yard provides a strong incentive for you to take appropriate steps and spend the necessary amount of money to deal with any problems.

Maintenance and operation of cluster septic systems: With a neighborhood cluster wastewater system, individual homeowners are much further removed from the maintenance and operation of the system. If it fails, it's not necessarily your fault, and because the failure does not occur in your house or front yard, you may not even be aware that the system is failing. You can be as careful as possible about what and how much you flush down your drain, but if your neighbors abuse the system, or if it is not properly operated and maintained, it can fail for everybody.

Cluster systems in Alaska: There are very few neighborhood cluster wastewater systems currently operating in Anchorage or even in Alaska. Under current regulations, the responsibility for permitting and overseeing the operation of neighborhood wastewater systems lies with the Alaska Department of Environmental Conservation (ADEC). ADEC has only one person in the Anchorage office tasked with this job, and his responsibility covers not only the Municipality of Anchorage, but also all the other areas of the State that are administered by the Anchorage office.

There are two permitted cluster wastewater systems in the Anchorage area. One of these serves nine residential lots in the Werre Subdivision in Chugiak. In this system each home has its own septic tank, from which the clarified effluent flows by gravity into a central lift station. The lift station pumps the effluent into a 4000-gallon recirculation tank, which has an associated Orenco AX- 100 treatment pod containing suspended filter media. The effluent from this treatment system is then discharged into a large soil absorption system. The lift station, as well as the community treatment and disposal system, is owned by the local homeowne's
association, and the maintenance and operation costs are paid by the members of the homeowner's association. This is a relatively new installation that seems to be functioning well, without any known problems to date.

The only other permitted community wastewater system in Anchorage was designed to serve 12 lots in the Grecian Hills Subdivision in the upper Rabbit Creek area. Although construction of the system was permitted by the DEC back in 2005, the developer has not yet finished construction of all the required components, so an operation certificate has never been issued. At least a couple of the lots have been permitted to be developed on the assumption that the wastewater system was under construction and would be approved. With no wastewater system completion in sight, the Municipality has placed a stop work order on all permits and approvals for residences served by this system until it is completed and approved. The situation has become a real mess with a lot of finger pointing between the Municipality and the DEC, and is an excellent illustration of some of the things that can go wrong with a cluster wastewater system.

Who should be responsible for cluster system operation? Because of the lack of accountability and financial resources of a homeowner's association to maintain or repair a failing community wastewater system, it has been suggested that the Anchorage Water and Wastewater Utility (AWWU) might be a more appropriate entity to manage and operate cluster wastewater systems on the Hillside. This concept has been presented to AWWU on more than one occasion; however AWWU has taken the position that it wants nothing to do with this type of system.

The DEC is clearly not adequately staffed to properly administer cluster wastewater systems on the Hillside and has shown no interest in gearing up to take this on. On the other hand, the Municipality has expressed interest in taking over this responsibility from the DEC and administering it through its On-Site Services Program along with individual water and wastewater systems. However, before this could be done the Municipality would need to develop and adopt appropriate regulations and hire additional staff necessary to adequately administer such a program. In this era of Municipal budget shortfalls, it seems questionable whether the Municipality will devote the necessary resources to do this properly.

One final thought: Hillsiders are generally united in their opposition to the extension of public sewers into the area, and for the most part have managed to install functional on-lot wastewater disposal systems. The failure of one or more cluster wastewater systems with no existing mechanism for repair and/or replacement could turn out to be the tipping point that leads to the "sewering" of the Hillside. All affected individuals and agencies should think long and hard about that, before permitting more poorly thought out cluster wastewater systems to be installed on the Hillside. In the author's opinion it would be unwise to permit any further development of community cluster wastewater systems on the Hillside until the necessary oversight mechanism is in place to ensure that the systems are properly designed, constructed and operated and have appropriate financial resources on hand to fix any problems that might arise.

Part V in the next newsletter will address Municipal and State regulations governing on-site wastewater disposal.

Ted Moore is a local civil engineer who specializes in septic system design, construction and testing.
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