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HomeMy WebLinkAbout1985-12-17 Septic System Design ReportIr CVG IZ-1-7-9� SYSTEM DESIGN FOR GARY RODERICK OF LOT 1, BLOCK 1, RINGERSWOOD ORONO, MINNESOTA 12-17-85 1. Percolation Rate, Type of System. 3 MPI on the primary site and 52 MPI on the alternate site. These results are from testing by others and this design is based on using those results. Mound systems under pressure. 2. Proposed Flow Rate. 5 possible bedrooms @ 150 G.P.D. = 750 G.P.D. 3. Soil Treatment Area Needed. 750 G.P.D. x 0.83 factor = 625 Sq. Ft. of rock bed area, or a bed 10 feet wide by 62.5 feet long. 4. Septic Tanks & Distribution System. Two septic tanks, the first of 1000 gallons and the second of at least 750 gallons are needed. In addition ,a third pumping tank and pump are needed for pressure distribution to the mound system. Distribution to the rock bed is to be through 3 perforated laterals 40" apart. All materials and cons- truction should adhere to the provisions of the City of Orono. S. Mound D_mensions. Since the ground slope is from 0-3% on the primary site, both the upslope and downslope areas can be counted for the required basal width. With the high water table, 2 feet of sand rather than 1 foot should be used making the mound 4 feet high. 4:1 sideslopes should be used which will extend out farther than the required basal width. If there are any other questions, please contact me. Sincerely, PERCOR, INC. Mark S. Gronberg PCA certified •Iwo- � T s Q ,�, •� _� i • i � r CO C-8r+ {� tT lid 'J •`a N N-' -� N at el 93 • .A ,• •► / .Y .... C-' can 1 �/• .0 '„ Pr1 '♦ .O • r i f'n d' �- rJ fA W. •* y[ < t a .CAe Clip i�r O � � � .mob A � � y ��� w� �e �� t'.�� s �M �.�+� %- ♦p r N � � f 5;A G E'n..,�•,� .-�N•�"'�L'�•��•�, �:, r s v a on° [M cc ca r- fry' �M`- ems- ►.Q r• .h ./• �n .� CD ty N e+ .'�.. w�+ !i` sR l� e� ci3 pp co pD CD co to to .s •� s ■C s t Q �c •t a t •[ < t ►� �►p Ca. t�.c,& a 0. a-C16 Oa QO•uC�A A�O.ia•LI.A�j. p.��O.a.t> f g Y 0 :' a or �•el i y . Q • � y �'r • . '� • j n e ft �, t � •• m; , ;, ,n M •., it %' : m -+ f ------•.ter F �4 10 wso �. •r i a• r � � � , o �•>dd 3 .ITr 3 w ••ii�O` d r . ,R • t 12 40 CO 3 a 0 •o 0o i� 00 O w cgOr'r� Oj Op w 00 � e e • s. �'21F,. -M ft y �.� � J 30r raj. •� Id 40 LA •t� • .I �d•1•!j O �XJ� �•~i rg � ,jM .Il:vi ai �� � 1! r �l,.�t � � .a,�dt � '0��jj�e M ! v •- a'� J gg •s !iZZ J33 q Q� r t 4 •' - /� � j it '+' ~ 3 1 A _ w�L Y} ! /, it (, �+ " :J ♦ 0 0. ,. `,: 00 Q W �!1 •J / [j t 9 EXI4I9IT 13ovcrol)er 27, 1991 P.O. Rox 209 Wayzata, Minnesora 55391 Mr. Judd Ringer 403 South pillow Drive Long Lake, Minnesota 551`6 D,nr Mr. Ringer: V?m have cmpleted a -0.tc for on -site sewage trc:jtrr.nt facilities of 15 proposed lots located r..int of Willow Road and no rh of Irunk llighway 113. 12 in Orono, Mi►.nenot i. A location .Ap has been enclo-icd 3*swing tho location of t>.e soil borings and percolation teats. Soil boring logs and percolation teat data is nlso enclosed. T1:s soil borin- show a +inifornly hirh water table throughout the area tested. This condition prohibits the Inntalintion of conventional soil absorption . alrntc-+a. 11::.. r ntle slopes and ;ercolation rates enct.untered indicate that Mound Slats 1s should to satisfa,tory on these nitro. W@ recomner.d Ciat the fur re b.1 provicTed With )To,-jncl Systems of coil a n,:orptlon. F1 '.-"' cIll if 'You taws any flue9tion-j. �, ►-a v(: -7 truly, cc: Hr. Michael Gnffron City of Orono tne. 3 copies - Location `tap Sheets 1 - 3 - Soil Borings 1 Sheet Percolation Test Data .a TO: Jeanne A. .'.ahusth, Zoning Administrator FROM: Michael P. Gaffron, Septic System In:;;)ectur DATE: January 5, 1902 SUBJECT: Ringer Subdivision, North Willow Drive 4615 Summary: All proposed lots wera found to have high water tables, nvcv _itating the use of mound systeri3. Percolation rates in the up : soil profile generally were suitable for mound systems, witn slower rates found in ureper test holes. Slo;,es on the entire site are fairly level and suited for :round systc -- This report will consist of: a) a short review of teach lot of the proposed division and b) a discu^Aion of mound systems, including how and why they work and their current aTLd future use as i)r-t of Orono's land use management plan. The Ringer subdivision in perhaps the most extensive de•!c l:.t.ment in Orono to date that will require all mound systems. A. Ringer Subdivision A preliminary review o1 the Hennepin County Soil Sarvey indicat^d a:,tcnsive arc,-!3 of Cordova silty clay loar., and Shorewood silty clay loam as voll as Lesour loan would be found at this site. These soils all would be e::pected to have a seasonal water table or saturation zone Latween 1 and 3 feet brow the sn-face. During the course of the soil3 inveotic7ation, I met the site evaluator, Carl Borg, and realtor r�raydon McCulley ne site. We made a boring which definitely indicated .arse high water table soils were prcuQnt. I later confirmed with Dr. Jamc3 L. Anderson of tLe Univer3ity of Minnezota Soils rxtencion Departr„cnt that mound systc,.a ��ould L;.► _ iv.ppropriato for these coil types. These are rauch th3 sa::.L soils are found in the Mcdina- 14orning3ide area, which experience conventional trench septic system failures due to the soil conditions. In general, tt.e lea*::y top, -oil characteristics for the Ringer property are euitat.:e for proper functionin3 of standard prenaure-m.-)und septic aystc:n3 as per Orono's Code ar,d Desion Manual. For clarity's sake I have labeled the northern most tier c£ seven lots as Block 1, the western group of six lots as Block 2, End thy+ two lots to.0— ro .,theast as Block 3. IAAt 1, Block •�• ,,•�„ M+...M Pares Pall thru P816. Horings BB11 thru BB13. Average prrc rates for both Frimar; and alternate sitar are acceptable. :jlupc:r are quite level. Saturation it ieationa (mottling) startel at 1.7 to 2.5 feet. Actual -tater able at 5-7' dt•pth. A mound system should be used due to the presences of shallow saturation zones. / lIt ge 2 0 u t3 [ :3 V a 4j JJ 44 44 in n d' N i r+ u O .-4 W r♦ f ,310 rolu roro to to .4 2 � 1; i% J�; J� 4-1 4.1 J J! 1; 4.1 4-1 1; W 44 W W 4J W 4+ 44 44 44 44 44 N O in to (D O t- O d' In in in . • N N . . • • N N . . NC . . N N . . N N �, O M N %.D + co f - %D m N M N 1 I I I 1 1 1 1 I O u 44, CU %p in N N lV M N m N [r N 41 N M r! M N # R # # # -.1 •r1 •4 +1 "4 •rl -4 •.J •rl -r/ •rl •.1 uy. a ru a sc1 a M a 0-4 rh cal t�7. ON 0 co .-4 N co •1 co m O 1` IIl In r♦ r4 r-4 N -4 •J. '1 CJ C3 f'1 $4 >I , n c: a H too i' � i ro •� u N l w > 1 'ClM �' u W N N t'' 1 H a o i. ld ►►4 0 +1 H Rd oa I4 >, [� Ck N u u 0 U j •� to i., a1 a oD t.l r v d J 0 ri ,, a -&j •-1 t] (►+ ri [1• CI' . • +J J-1 J.1 J•1 �+ Ja 'a W W 44 W O 14 1'�N 1 MO O� to Q • 1 rJ 4 q N .V N N rl vN $ A tl N -H m O .4 ro': W 44 -t t O '4 C: N N O V co U U00 00 rl OCD O O 0 "1 N r1 El rl O A t0 JJ A o m >,U r-1 M r/ N a r1 11 b m i.T r1 a to a > rf 14 m ••4 > #• s •n ro a a •.. .1 -r4 "4 -S ,a V* a + q N ti f� f3 Ei u vt tJ a 9 V W a ht�nq OA Cl 0 n L 1MDr� a t*� •� U Q tL q LC1� 'a ,(1 e ro •rl �-► �': CJ •rf N A > to a, l�i ►, rj .� a r. 4 t+ frt .j t+ t7 r9 c1 O P3 V. Z f.) Tr -A O H H �7 rl N 0 Q •r1 `l N (9 0 1) C1 � Q7 .Gl 0 41 V R+ !:'1 to C1i W H `Q a H +� o $1 .t: ►14 �f a t; H, N N • t, 4j t V t, u 94 0 C A I•'1 1� 41 41 i1615 1tin(jo.- Subdivision .... _ _� .._._ ...._._....�.���..�..:...�...._..._:..............+.i+r..a.;:....:..:r.:..a:N. Pag12 4 Lot 2, Block 1 Peres PB21 thru PD26. Borings BB21 thru PR23. perc rates for bith t:rimary and alternate sites are acceptable. Slopf•n are nearly level at the tested sites, ranging from 0 to 3%. Mottling indicated below 2', with actual water table at 3.2 to 4.21. A standard mound system should be used due to the pr,:sence of shallow saturation zones. Lot 3, Block 1 Peres PB31 thru PB26. Borings BB31 thru 8833. Slopes in the primary site are apprcxirately 6-81, on a slight flattening Of the 10-12% slopes surrounding it. Borings in the primary site indicate 1 to 2 ' of loamy topsoil over a 6" layer of organic clay topsoil over a plastic sandy clay. Actual water table at the primary site was below 51. However, the high plasticity indicates a heavy clay that is probably baturated. The secondary site was rnottled below 1-5 feet with an actual saturated zone at l' depth. Coupled with a slope of 10% the secondary site is marginal for a round aystcm and would require at least 2' of sand bane an part of the design. I suggont that standardpresoure moi,nd system ba required for both sites with addea sand depth for Lhe second-1-y system. Plc2se note that this lot is the r..c3t tenunus in the subdivision in terrii of olope and soda r_onaideration far using a round system. Should a proposed housa location encroach on either of the tested sites, careful revica and possible additional tcr;tinq will be needed to ensure that a mound can still be used. The site do^s not appear capable of supparting any kind of R trench sycte.'m. Lot 4, Block 1 Peres PB11 thru PE346. "orings 1041 thru BB43. Slc, co average 51 - 7% overall. Borings indicate actual ••eater table at 4' with mottling at a depth of 3-4' for tha primary and 2' at the accondary site. Porc ratc3 wer^ fairly uniform throughout thono teatcd sires. A deFr::�ssion/draina,^:• y to the ir..: ^diate south of the taatel sitar r,a^t be rvoidecl during construction of '::re a;,3tc,73. would rccon rend a standard proaaure round for both niter. Lot 5, BV nk 1 Peres PI351 thru PD56. E::)ri.ngo D351 thru DD53. Slopo3 are 31 to 6% overall. Mottling at the prit:ary sito started at 2.7 co 3.5' :pith actual water table at 3.7 to 5.31. z-his site in acceptable for a standard mound The alternate site has a perc rate conjidored too slow for any system by close scrutiny shows that the pores were taken at depth its the candy clay subsoil, not in the topsoil. In general, throughout the entire subdivision the touting dons at a dirth of 12", in tho topsoil, indicates acceptable percolation rateq, with tooting at 24" or more indicating slowar, marginal perc rhea. in my opinion, thin situ in no different than c.o-.t of the cthora, and would have an acceptable perc rntc if tested at the 12" depth in thu, sandy learn topsoil. NO further 'tooting should be rrqui.redt a m.-)und uyntrm is rero-mended. i615 Rir.ge-- SubdIvininn Page 5 Lot 6, Block 1 Peres P861 thru PB66. Borings BB61 thru B063. Average perc rates at both sites are accop'table. Slope© rangy: from 2 to 4%. Mottling started at a depth of approximately 2.4 feet, with actual water level at 2.5 to 4.4'. A standard mound system should be used at both sites. Lot 7, Block 1 Peres I'371 thru '_°B76. Borings BB71 thru BB73. Slopes average 2-3%. Pere rates were fairly slow, with the secondary rite being somewhat slower than the limit (however, the justification for Lot 5, Block 1 also applies here). Actual water level ranged f_o.a 1.7 to 3.5' with mottling generally below 2.5'. A standard *round is reco=onded for both sites. Lot 1, Block 2 Peres PAU thru PA18. ncrings BAll thru BA13. Slopes are very flat. t.cttl'.,-Ig Wa3 indicated below 2.2 ' with actual Miter encountered below 2.0'. 11 o necondary sitoc wore tested. All sites are acceptable for a standard trcund system. Lot 2, Bloc): 2 Peres PA21 thru PA76. Borings DA21 thru IM23. Very flat eloper. Mottling occurs at 2.0 to 2.4' with actual water encourtercel below 2.41. Pcrc zaten on both sites are acceptabl3. A trosn9 uyatem is reco-- ^_nded for both cites. Lot 3, Block, 2 Peres PA31 thru PA35. Eorings PA31 tfiru I'A33. Slop^3 avcran^d 2 to 5t. i:ott? ing ntarto at a depth of 2.0-3.5' . JNctu-il '.or level was below 2.51. Pcrc rates arc• acceptable. !'��^d %tat-':nn are rccomam-,ndTd for both 3itc3. 14ot 4, Block 2 Peres FA41 thru PA46. Borit.g3 DA41 thru PA 3. Slopes are very flat. Mottling generally was found b�lc:a 2.0', with actual water level at about 4.01. Pcrc rato for prir-----i site is acceotablet perc rato for secondary s to in sla =fitly a2ow but a. ,aptable for a mound based on the justification referred to for Lot 5 Block. 1. I recommend a mound systcri for both dites. Lot 5, Block 2 Peres PA51 thru PA36. Boringo BA51 thru rAP,3. Slopn3 are very flat. Mottling occurred below 1.2 fcot with actual �,.ater holo4 4.0 feet. Perc rates are accr'ptable for the prir,'iry sit- :-nd slightly slow at the cacondary site. (R;nfor to Lot 5, Block 1) This lot has the overall wor3t: cot of percolntion rates of tho division. 'lloweve_•, only two of the pores tore taken in the topsoil, the o:hcrs, tti.ju of which were v:!t-y nlrw, were at Onpth. I recommmend that a tround 3ystrm be utied on thin Mite. If. t;«rca ware re -taken in the topsoil, it is likely th.cy would );a^3 as Jid nearly all others done in this manner. 0615 Ringer Subdivision .image 6 1.ot 6, Block 2 Peres PA61 thru PA66. Borings BA61 thru BA63. Slope:; are nearly level. Mottling occurred below 1.5', with actual water encountered below 5.7'. (Note tj;at soil avpea=s saturated below 2.5') Perc rates were aCLeptabl,:, although t of 6 taken at depth very very slow. Both primary and secondary sites should use mound systems. Lot 1, Block 3 Peres PC11 thru PC14. Boring DC11 and DC12. This lot contains an existing house, garage and barn. The existing septic system is unknown and was not located during my routine insp:^ction in July 1981, although no evidence of failure was noted. A future drainfield site has been tested to the south of the house. Average percolation rate is 2.1. minutes per inch; soil borings indicate coils suited for a shallow trench or mound system, with mottling b-aginning at a depth of 5'. This is the highest elevated point in the entire subdivision and appears to be the only lot possibly suited for a shallow trench system. An attempt should be made to locate the existing system to ensure it is within the lot boundaries, although there is only a-rcriote possibility that it isn't. Lot 2, Block 3 Peres PC21 thru PC24. Borings BC21 and DC22. This lot contains an existing house and small shed. The existing septic system is unYno:m and was not located during my inspection last July. '.o evidence of system failure is not:^d. While the existing system undoubtedly consists of trenches, soils data proviked for a future drainfield site indicates mottling at a 3.5' depth. This indicates that tho rcplacemcnt system, should it ever be necc3sary, would probably have to b^ a mound. Percolation rats aLeraccd 56 mpi. It would elto be advisable to locate the system to enE;ure it is within tho new lot boundaries. B. Dinaunnion of Mound Systcmi Since the proposed Ringer subdivision appears to need mound systems throughout, it might be worthwhile to review the conditions which favor u,.e of mound aystcrns over conventional trench systc.-nn. A, you are aware, a biomat forms at the rock -nail interface in a standard trench system. This biomat acts as a "valve" to slow the downward percolation of septic tnnk efflucrit to a rato ♦:fiche the flow is unsaturated, i.e. .tir in the coil pores is in contact with the percolating effluent. Under thoso enocntial conditions, adec late sewage treatment will occur. 1io%,evcr, in ninny soils, eitL!r a seasonal saturated condition or extremely find, impermeable roil tc:cture (or both) tends to eliminato the air/effluent contact and al.no severely limit3 the soils capacity to absorb large amounts of effluent. 'Io ensure that a standard trench Gy3tem is not i615 Ringer Subdivinion .Page 7 installed in these limiting soils, a :yet of governing criteria have evolved ever the last 50 years. Specifically, trench system are not allowed: 1) where the percolation rate is slower than 60 minutes per inch of water level drop in a pe-colation test holes and 2) where the highest known water table or indicated saturated soil layer is less than 3' below the bottom of the trench. In most cases, these same soils have a varying amount of topsoil which is usually "loamior" and will accept and treat a limited amou• t of effluent. The pressure -mound system is designed specifically to use this loamy topsoil layer for affluent treatment and disposal. In brief, a 12-24" layer of sand (placed over the natural roughened topsoil) is fed effluent from a pressure distribution system in an overlying rock bed. Tho biomat "valve" forms at the rock/ sand interface which is 12-24" above the natural soil. Because of the pressure distribution, an unsaturated air/effluent contact is maintained as treatment occurs in the sand bed. This treated effluent is then diapnrsed into the topsoil and allowed to move laterally through the topsoil,possibly even past the boundaries of the mound systcm (yat still below the surface) until it eventually seeps downward or evaporates over a wide area. 7t would be poor planning for Orono to allow installation of standard trench drainfields in soils which have high-water table characteristics, since many systc= likely would eventually fail, as was the case in Medina-tiorningside. Since Orono has shown a rtrict desire tc limit tho extension of sanitary sewers, it n,-piars reasonable to allow (and, in fact, pro-otc:) the use of r'.".-csrnato on -site sewage treatment mothod3 whore development pressures persist. Mound syntemp have boon installed over the last 10 to 15 years around tho co,intry no an alternative to trcnchea. In Orono, pros3ura distribution mounlo were first installcl in 1978. To date, the .Ci1_y*ha3 13 pressures rioiinds in cervic;,, with no recorded failures. In my opinion, under specified site conditions, mound systems are a safe, sanitary, reliable method of sewage treatment.