Conceptual Design and Cost Estimate fo a Phased Wastewate Collection and Teatment Pepaed fo Wenck Cleawate Rive Wateshed Distict June 2006
Wenck June 14,2006 Wenck Associates, Inc. 1800 Pionee Ceek Ct. P.O. Box 249 Maple Plain. MN 55359-0249 (763) 479-4200 Fax (763) 479-4242 E-mail: vvenckmp@wenck.com P l M. Mavin Bunsell Chaipeson, Boad of Manages Cleawate Rive Wateshed Distict P.O. Box 481 Annandale, MN 55302 f1 Re: Conceptual Design and Cost Estimate fo a Phased Wastewate Collection and Teatment Dea M. Bunsell: [ Wenck Associates, Inc. was etained by the Cleawate Rive Wateshed Distict to complete a conceptual design and cost estimate fo a phased wastewate collection and [* teatment system. Wenck espectfully submits ou findings heein. INTRODUCTION The system is based on a hypothetical location within the Distict. The system design is p, based on the following(jssumptionst) 300 homes 30,000 lineal feet of sewe A thid of the collection system will be installed in each of thee phases The teatment system will be installed ove 12 phases with 25 homes in each Peak flow = 450 gallons pe day pe home (gpd/home) P Homeownes povide individual septic tank, pump, and sevice connection as 1 equied. P i The poject consides the following altenatives: Wastewate collection system (gavity and pessue) f3 Pimay teatment (individual o common septic tanks) 1 Seconday teatment (sandfilte, textile filte o aeation), and Othe assumptions: Disposal (dainfield). Estimated cost based on ecent bids and updated to 2006 No inflation is consideed fo futue phases 20 aces of land fo teatment site is included in the fist phase. STEP pipe is plowed in with no oad estoation equied <*«*>. «-^ J} Gavity pipe is tenched with oad estoation equied. T:\0002\94\Repot\Daft Repotdoc
p M. Mavin Bunsell Chaipeson, Boad of Manages Cleawate Rive Wateshed Distict June 14,2006 p Page 2 COLLECTION SYSTEM DESCRIPTION Seveal wastewate collection system altenatives wee consideed. Thee altenatives ae p included in this epot and descibed below: Ontinn 1 - Septic Tank Effluent Pump (STEP') pi ~ L A STEP system consists of an individual septic tank at each home with an effluent pump to diect the wastewate to the teatment system as shown in Figue 1. The STEP system P is essentially a pessue sewe system that will utilize a High Density Polyethylene (HDPE) pipe as the collection system. Depending on its location, the effluent is pumped into eithe a 4, 5 o 6-inch HDPE focemain and diected to the wastewate teatment and disposal aea. Each sevice would have a double check valve and shut-off valve to isolate the sevice fo maintenance. The homeowne would be esponsible fo the cost and installation of the individual septic tank and effluent pump. Existing septic tanks can be used if in good conditions and could be etofitted with an effluent pump. Option 2 - Gavity Sewe and Common Septic Tanks I Option 2 consists of a 4" sevice line at each home connecting to an 8" Polyyinyl Chloide (PVC) gavity sewe pipe. Manholes would be located evey 400 linea feet. P Pumps would be equied at some of the homes in ode to convey the wastewate to I additional lift stations. Due to the hilly teain, appoximately 15-lift stations would be equied. A final lift station outes the wastewate to seveal lage, common septic tanks P pio to enteing the teatment system. Fo this poject, a total of 400,000 gallons of ' septic tank stoage would be equied. This will be accomplished by installing 1-33,000 gallon septic tank in each of 12 phases. L Option 3 - Gavity Sewe with Individual Septic Tanks Option 3 consists of an individual septic tank at each home with a 4" sevice line connecting to an 8" Polyvinyl Chloide (PVC) gavity sewe pipe. Manholes would be located evey 400 linea feet. Pumps would be equied at some of the homes in ode to i lift the wastewate to the sewe. Due to the hilly teain, appoximately 15-lift stations 1 would be equied. The final lift station would oute the wastewate to the teatment pn system. t:\0002v94\epot\daft epot.doc-miw
M. Mavin Bunsell June 14,2006 P Page 3 Chaipeson, Boad of Manages Cleawate Rive Wateshed Distict TREATMENT SYSTEM DESCRIPTION Reciculating sand filtes, eciculating textile filtes and aeation systems wee analyzed as seconday teatment systems. A eciculating sand filte is an open ganula-media filte bed. Wastewate fom the septic tanks flows into a eciculating/dilution tank whee a time contolled pump peiodically eleases effluent to a distibution system on top of the sand filte bed. Each time effluent is eleased ove the filte; the effluent pecolates though the sand filte media and is teated by natually occuing micooganisms that populate the filte. Effluent is collected at the bottom of the filte. The collected effluent is then divided and fou-fifths is sent back into the dilution tank to be eteated and onefifth is sent to disposal system. In this way, the effluent, on aveage, should be teated in the sand filte five times befoe being eleased to the disposal system. A eciculating textile filte system opeates the same only that in place of the sand, p* 2 ^V Z.& v>»\<- textiie (fabic) sheets ae used as shown in Figue 2. A textile filte system consists of "pods" that can be added, as additional wastewate teatment is needed. An aeation system followed by settling is an altenative seconday teatment system. This system consists of two tanks. The fist, the aeation tank, bubbles ai though the effluent to incease micooganism activity and speed the natual teatment of the effluent by the micooganisms. Afte taveling though the aeation tank, the effluent dains to the settling tank whee the teated sludge is allowed to settle. The effluent is then pumped to the final disposal system. L It was detemined that a textile filte system woks best fo a phased appoach although othe systems could be consideed in the final design. DISPOSAL SYSTEM DESCRIPTION The dainfield teatment system analyzed is a tench design simila to that used fo individual septic systems. The teated effluent is distibuted ove the natual soil allowing the existing soil micooganisms to futhe educe the levels of phosphous and nitate that ae eventually eleased to the goundwate. Fo this poject, the dainfield is designed and expanded each phase in ode to accommodate the additional 25 homes that ae connecting to the wastewate teatment system. The dainfield is will ultimately be designed to teat 135,000 gallons pe day of wastewate. t:\0oo2\94\epoilvdnift epot doc-maw
M. Mavin Bunsell Chaipeson, Boad of Manages? _ ^ tv Cleawate Rive Wateshed Distict June 14, 2006 Page 4 SUMMARY Based on this conceptual analysis, thee types of collection systems wee evaluated. Othe options could be consideed in the final design phase. Table 1 is a cost compaison of the thee options. The total estimated cost fo Option 1 is $2,730,000. The total estimated cost fo Option 2 is $7,020,000. The total estimated cost fo Option 3 is $6,180,000. The STEP system is the lowest cost and lends itself best to a phased appoach and maximizes the use ofcxisting infastuctue (i.e., enclosed septic tanks). The collection system (sewe) could be installed fo an estimated aveage cost of $3.500/lot. An additional assessment of $l,400/lot would be equied assuming the initial teatment system is assessed to the total assumed sevice aea. We ae available to eview the esults of this analysis with the Boad of Manages and povide additional assistance as equested. Respectfully submitted, WENCK ASSOCIATES lofiai-cwenck, P.E. Enginee fo the Distict! \00OJW-Hiepon\il ail npot.doc-maw
I Table i
Table 1 Cost Compaison Conceptual Design fo a Phased Wastewate Collection and Teatment OPTION 1 OPTION 2 OPTION 3 Phase Total Homes Pessue with Individual Septic Tank and Effluent Pump (STEP) Collection Teatment Gavity with Common Septic Tank(s) Collection Teatment Gavity with Individual Septic Tank(s) Collection Teatment 1 25 $400,000 $420,000 $1,600,000 $420,000 $1,500,000 $420,000 2 50 3 75 4 100 $150,000 $150,000 $150,000 5 125 $350,000 $1,600,000 $1,500,000 6 150 7 175 $240,000 $240,000 $240,000 8 200 g 225 $300,000 $1,600,000 $1,500,000 10 250 $150,00 $150,000 $150,000 11 275 $90,00 $90,00 12 300 _ $o $90,00 $60,00 $90,00 $ ESTIMATED COST $1,050,000 $1,680,000 $5,340,000 $1,680,000 - $4,500,000 $1,680,000 p?l ESTIMATED COST PER LOT $3,500(1) $5,600 $17,800 (2) $5,600(2) $15,000{3) $5,600 P) (1) Requies each lot to have septic tank and effluent pump. (Z) Some lots may equie ginde pump. (3) Requies each lot to have septic tank and some will also equie pumps. T:\OOO2\S4\Tabk3s\Tabte 1 Cost Compaison 6/14/2006
Figues
1 STEP (SEPTIC TANK-EFFLUENT PUMP) PRESSURE SEWER SYSTEM JUNCTION BOX ANp HIGH LEVEL ALARM PVC PLASTIC PRESSURE MAIN 2 INCH PLASTIC PIPE FOR ELECTRIC POWER AND CONTROL WIRES 1% INCH PLASTIC SERVICE SHUT-OFF VALVE CHECK VALVE EXISTING OR NEW SEPTIC TANK BALL OR GATE VALVE WATERTIGHT SUMP WITH MANHOLE ACCESS CHECK VALVE SUMP PUMP Cleawate Rive Wateshed Distict Pessue Sewe Wenck Wenck Associates, Inc. 1800 Pionee Ceek Cente Envionmental Enginees Maple Plain. MN SS3S9 JUNE 2006 Figue 1
Textile Filtes Ventilation Assembly Distibution valve Recic/Blend Tank Cleawate Rive Wateshed Distict Textile Filtes Wenck Wenck Associates, Inc. tboopitiiiciiccek Cente EnvioEmtmal Enginees Maple Fhiu, MM 55359 JUNE 2006 Figue 2
Wenck Associates, Inc. 1800 I'ionee Ceek Cente P.O. Box 249 Maple Plain, MN 553590249 (763) 479-4200 Fax (763) 479-4242