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HomeMy WebLinkAbout1980-10-22 Site Evaluation Report*■; f- SITS EVALUATION REPORT i-'OR HARRISON R. JOHNSTON, JR. ORONO, MINNESOTA 10-22.80 During October 17-22, 1980 all five proposed lota in the sub- dlviaion of Harrison Johnston, Jr. wore tested for the suitability of supporting on-site drainfield systems. Six percolation holes were tested on each lot and three soil borings taken on each lot to determine bothprimary and alternate drainfield sites. The percolation holes were dug 6 inches in diameter to the 4 foot depth except the alternate site on lot 1, block 2 where holes $-6 were dug 2 feet deoo to teat for a shallow trench system. The holes were dug with both power and hand augers. The soil borings were dug t^ith hand augers and were 6 inches in diameter to the 4 foot depth and 3 Inches in diameter to the re- maining depth. Some very permeable soils wore found on most lots and all lots bad sufficient percolation rates to qualify for stan­ dard drainfield systems. Hie alternate site on lot 1, block 1 will require shallower trenches to avoid the water table. *The trenches on the primary site of lot 1, block 3 will also need to be const­ ructed fairly shallow and an interceptor drain should be used to divert runoff water from this site since the lot is bowl shaped and oollocti nmoff water. Better soil was enoo\intered shallower on the altex*nate8j,j^g^^ 3 of block 1 a pimp will probably be needed slnoeth^bea^^j|oi^^ exist on top of the hlll.nnSsomigkit oe necessary to use pumps on other loU^.pendln^ Sh th. pl.conont of the houees. Additional design infoz*matlon for the individual houses will be needed prior to construction. It is imperative that these tested area not be disturbed since there are some steep sldehlll slopes on some lots and some prohibitive soils and water tabi ;; near tl»^ marshes which may nreclude any other areas being used for drainfields. If any additional information is needed, please contact me. / ■1 V pRopitiRTy LOT 3, BLOCK 1 olnt5.on Results .ioJc llo. P-1 P-2 P-3 P-i; P-5 p-6 liaterial Lt. Brn, Pine Sand Lt. Brn, Pino Sand BpQwn Loamy Sand Brown Loamy Sand Brown Loamy Sand Broim Loar.iy Sand Percolation Rate 1.7 Kin./Inch l.k 2.2 2.5 2.4 2.0 Tho avg. porcolation rate for holes l-4(pi*linary site) =2,0 PiPI, llio avg. percolation rate for holes 5-6(alt. site) = 2,2 MPI, S.B. 1 Depth(ft,) 0.0-1.3 l.q-2.0 2.0-5.0 ‘^.0-7.3 I.5-0.0 Soil Borings Material Black Loam Gray Brn, Sandy I-oam Brown Pino Sand Lite Brown Pine Sand Lt. Brown Pine Sand* Powdery Mo mottled soil or water table after 24 hours.I S,B. r 2 Depth(ft^) 0.0-1. 1. !>-2.5 2. b-p.0 5.5- 5.S 5.5- 0.O Material Black Loan Gray Bm, Sandy Loam Brown Pine Sand Gray Bm. Pine Sand Lt, Brown Pine Sand No mottled soil or water table after 24 hours. Katorial Black Loan Gray Bm. Sandy Loam Brown Loamy Sand Gray Bm, Pine Sand Lt. Bm, Pine Sand# Powdery Depth (ft.) 0.0-1.0 1.0-2.0 2.0-4.0 4.0-7.0 7.0-0.0 .*.4-^ ..fat"—— A •i f I ft > : ? % >>9 f ■' : \: K O # /.ntutm Mf •>1 t :i '•a ii-- s I 1 \ ^ 1" /“if-*«'.. »•-' :»*> s*/t/e^»49'/4‘'k/4//.f390’t rmS7P't • =. r * ■ ’*i'. ^4 ^a/9s^ ///ta «f Jac4,am /0-//7-21 i t r.<■■*•>. c *•'*:'■ ' f ^ O.L. Bv=n ■ O.L. A s ’ 45ifI* ‘Ik-. ^ h• ,,f:. ■; r- ' .; n*'^: T i -v^l j * • a' ' • ■• - '■)■•^ r- ■ *'••« r- ti 1 •S I . ^ 9JO - /. «#* yII'.. 3 0n f L35* y 't:'fjM I 3 -1•rp /: i 'A/•.aAAr5 .' #': i />ojf su 2.0/4C/»e5 ] \7 MII .fl.3APuV'n. \-»II ^OSt/gcS ^OK/Zf 3»‘ ! IV.%\ 4i: Mf'*J*' I V:1 ■.lt-^.-:'>LV m Pio f i; M^G K|V ^At00 ■2*' ^£i^aj »* ' 9.9 i ,9* ^ •"'s . r. •!■ : I j ^ 'k » ■'ll ^Sskt.A- '■> J m £ f 4-t Q oO o /Ci TO: Jeanne Mabusth, Zoning Administrator FROM: Michael Gaffron, On-Site Systems Manager DATE: October 30, 1980 SUBJECT: #582 H. R. Johnston, 925 Willow Drive South - SUBDIVISION On-Site Systems Review On October 28, 1980, I reviewed the five proposed new building sites for the above referenced subdivision as per the attached survey. Each lot (save Lot 4, Block 1 with existing house) appears to have 2.0 acres of dry buildable land. However, due to proximity to adjacent wetlands and the accompanying water table a portion of each lot is unsuitable for use as drainfield. All lots had areas tested which meet the requirements for standard trench drainfield systems. These designated tested drainfield areas on certain lots are the only available acceptable sites for drainfield. In every case, assuming a long term water table exists at approximately the 930’ elevation, no drainfield trenches (2* depth standard) should be allowed below elevation 935' in order to ensure a 3' separation between trench bottoms and water table. In addition, where individual lot testing indicates a water table depth, the above 3* separation must be adhered to. Following is a detailed review of each lot. Lot 1, Block 1 Testing indicates soil and water table conditions are suitable for a standard trench drainfield system. This lot has some alternate house location possibilities. However, the tested site and in fact the entire lot should be left undisturbed until a final house location is determined. Lot 2, Block 1 As in Lot 1, testing found sandy soils suitable for a standard drainfield system. Various house locations may be possible. An excavation crossing the lot has not severely damaged drainfield areas, but no further excavation or disturbance should be allowed until final house location is determined. Lot 3, Block 1 This is probably the most critical lot of the subdivision in that a limited A area is available for use as drainfield. The tested area is at the highest I point of the lot due to extreme slopes. An excavation near the northwest I corner of the lot may have affected the extent of the area available for I drainfield. (bv creating an outlet for sidehill seepage from trenches above / the excavation A However, due to the extremely fast percolation rates and / sandy soils and the existence of untested but probably suitable area for / drainfield to the east on the lot, the effect of this excavation is only y slight. ■■■!! AJoVE /f. •*- #582 October 30, 1980 #582 H.R. Johnston 925 Willow Drive South Page 2 Lot 3, Block 1 (Cont.) When this lot is developed, care must be taken to make sure the house / location does not encroach on the area to be preserved for drainfield. / I suggest that for this lot (and for all subdivisions in the City) that / the tested drainfield sites be somehow entered on the title or deed for / the property so that prospective buyers are made aware of the restriction^ on the_lot.;__ j Lot 4, Block 1 ^ This lot contains the existing H.R. Johnston home. Although the lot as proposed contains only 1.64 acres, adequate area has been previously tested and exists for use as future drainfield. A relocation of the lot line between Lots 3 and 4 to give each property approximately 1.8 acres would serve no purpose as far as drainfield sites are concerned. Lot 1, Block 2 The soils on this lot are considerably different than those of the westerly lots. Loam and clay loam soils are indicated, and the percolation rates were understandably slower. This lot contains 2.4 acres and has a somewhat limited number of possible house locations which would allow a gravity-flow drainfield system. The lot is acceptable for a standard trench drainfield. Care must be taken during development of the lot that drainfield trenches are kept away from the pothole in the center of the lot. Lot 1, Block 3 This lot has loamy soils with a fairly good percolation rate. The tested drainfield sites are to the immediate southwest of the existing paved driveway and due to slope conditions appear to be the only likely sites for use as drainfield. Again, care must be taken to preclude disruption of these sites prior to development. It appears that the suggested location of the house would be on the north end of the lot approximately on the existing driveway. Summary Each of the five proposed new lots should be acceptable for standard trench drainfield systems. Fortunately, this is one of the few areas of Orono having sandier soils. Certain lots as indicated may have limiting sites due to water table and slope constraints. As the engineer's report states, it is imperative that the tested sites not be disturbed by further excavation, grading or filling until permits are issued for specific house locations. I recommend approval of the subdivision as per preliminary plan with the above recommendations. V OLf\. dasVb-O.L CO.L. B -^1O.L. 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