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1991-1170 G/H Street Address C 2G Category Serial # 1 C, C`-J Name Description Plan ck. # Year recdescv LAND DEVELOPMENT ENGINEERING • PLANNING • SURVEYING (6191756-937 4 The Fairbanks Village Plaza, RO. Box 9661 Rancho Santa Fe, CA 92067 ij H Y ��oL-n&y OLA NA v To W� v tj L 14- IN - D u Z AZ —7 Dr� C A P-7 7= 4 ofESSI Q A. Ca C*' to rn W rn w No. 29375 T F- E ET) = EXP. 3-31-95 Cp IV% OF 0 �� rn r N H c ° - n d r- m o v ° z oA A> v �v� > r C n o N n 3 �A orno o> 0 =�-Z1m n z b W "0> W c) C) n > o r- -n Z WO p p y N �. W �, (A p 00 om O r =7 ar L) x n O t > O > o ? n W H .. Cif z p - V1 0 2 ;a a ti > r> - > 0 "' n CD %° 9 CD r �' _ t ..J i � � ✓ FYI O no ..)ice ( ` \ //• //�� ^� �, // ��qil ~ Co) CD CD 00 �MM Ln LAJ m � O 'Tl V C rn . r- m 0 V 6 - 0 C: tZ 7 7; > o > > r n o CA 0 rm 0 = z -n ;;o LA 0 > n > -n f- 2 _ 0 a tA U "7 1 z > > 0 rn > 0 co V OMM& O m CD ly\ .00) CD C:zt 7/21' CD cm o cr> yn C cn CD z .a r ice; ` •. 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O O' r+ e-+ c-+ -S O c+ < - _j - S 11 a c cu Cv =- -•+• CD --+ C+ c+ n -+- m p co cD a � ° ofl.mv c+ -+ vn CD O O ^s C+ a In a O N c+ p • O O c 'S =5 CD cL Cy CD � < O O -0 =3 LL -+ CD CD d 1 �- O CD _� n H a � n to rD "S c C •+ -. O -� .� y CD C+ 'T I �E S =' O _J •� =s .A J r cal CD - •• c -h (D CD II O a -' "7 9 P, n ] to - ' L] - 7 ID n + CD O1 O n tD r -� O to c C S -.f O C __j C) Q Z CD ••T 1 CI) W cn - T CD O < v c a n � CL 0 0 CD O ae rD o (D �— -s ' < a 3 > p =r - Ln O d -h O 0 /� EQLIAT /ON - C //. 9L � 1.385 Feel Tc f/ ) 5000 Tc = Tune of concenfral 4000 L ° Length of watershed H • 0 111 /n elevation a/o ,7g 3oDD ellect /ve s/o oe 1117 (See 'fVpendiX X -,�V 7e- W1 5 FGe� flours Miaufes 2000 ¢ 2¢D 3 /BD /D /DOD. 900 Bloc 2-- 12,0 700 600 \ S 90 SOD \ gp � 50 200 \ \ 2 a0 /00 / SDOD •�QDD 20 \ /B 40 2000 \ \ 12 /800 \ 310 NOTE /SOD g F OR NATURA WATERSF -DS, 1200 B 20 ADD TEN UTES TO /DOD 7 COMPUTED TIM F CON - 900 U CENTRATION_ BOO 6 � -�-s- -- --� -- — � 700 600 5 /O 500 ¢ ¢DD 5 00 3 2 200 A/ L Az SAN DIEGO COUNTY NOMOGR )kH FOR DETERMINATION DEPARTMENT OF SPECIAL DISTRICT SERVICES OF TIME ONCENTRATION (Tc) DESIGN MANUAL FOR NATO L WATERSHEDS APPROVED DATE /z 4 APPENDIX X -A L-A-10 Rev. 5/81 Group B Soils having moderate infiltration rates when thoroughly wetted, consisting chiefly of mod- erately deep to deep, moderately well to well drained soils with moderately fine to mod- erately coarse textures. These soils have a moderate rate of water transmission. Grou C Soils having slow infiltration rates when thoroughly wetted, consisting chiefly of (1) soils with a layer that impedes the downward movement of water, of (2) soils with moderately fine to fine texture and a slow infiltration rate. These soils have a slow rate of water transmission. Group D Soils having very slow infiltration rates when thoroughly wetted, consisting chiefly of (1) clay soils with a high swelling potential; (2) soils with a high permanent water table; (3) soils with clay pan or clay layer at or near the surface; and (4) shallow soils over nearly impervious materials. These soils have a very slow rate of water transmission. Soil group and soil cover maps have been prepared by the Soil Con- servation Service, and include most of the County. The maps are available at the offices of the Department of Sanitation and Flood Control. The Department of Sanitation and Flood Control has developed a computer program for calculating CN numbers after soils groups and covers have been tabulated for given basin and sub - basins. Tabulation is usually accomplished by using a one -half or one inch square grid and listing the group and cover at each intersection. The hydrologic condition of soil cover must be determined for each basin or sub - basin. Photos and slides showing typical hydrologic conditions of soil cover for many areas of San Diego County can be examined at the office of the Department of Sanitation and Flood Control. I -A -4 0 REV. 11/75 t TABLE 2 RUNOFF COEFFICIENTS (RATIONAL METHOD) DEVELOPED AREAS (URBAN) Coeffic C � • So Group tl) Land Use L Residential: A B L.J p t Single Family .40 .45 .50 .55 Multi -Units .45 .50 .60 .70 Mobile homes .45 .50 .55 .65 Rural (lots greater than 1/2 acre) .30 .35 40 .45 l Comme rc i a) (2) .70 .75 .80 .85 80° / Impervious !: Industrial 2) .80 .85 .90 .95 s . 90% Impervious r - NOTES: i ( ' ) Soil Group mans are available at the offices of the Department of Public Works. ( actual conditions deviate significantly from the tabulated impervious- ness values of 80% or 90%, the values given for coefficient C, may be revised by multiplying 80% or 90% by the ratio of actual imperviousness to the t. tabulated imperviousness. However, in no case shall the final coefficient be less than 0.50. For example: Consider commercial property on D soil:-group. Actual imperviousness = 50% Tabulated imperviousness - 80% Revised C = $O x 0.85 = 0.53 IV -A -9 APPENDIX IX -B O Rev. 5/81 CScE �lCGC�rn N (s Zc�o ACA t� M►A�'� MAQUAL ►�� 0 or eoof4 .0"t, 45bx )r X 10 All C- i, 2 107 3. 02 • io l' i 1 I11 11 1 t 1 1 :1 •i,TM��l:j 11 •Il1. l�: l i 1 1 - i 177 Q � � • -. _ ._.;mss.._ b - ( ( ( = 1 I - ---T- P =2 ka +b) I V f w �... A I kil LO , / 1 1 i 1 111:: 1: 11:• li r1111.:1i . p ° ).) 1 I ! I °- - .v � t � I � I i ( ( 1 �� 1 �� i � 1 1 _ � • w I 17 1 u 2 - LtJ r —m— VJ ( � P/ P - S. I OH � Fil 1 I i I • o.l c I I f f ! I �,_.,_,_f ' I I i I`f I _ • H EADS Uj? T!0 VEI(d) IES HEA A 2 l.4 Icl:��!c�5 !,V I I>=s S H EAT B ► ti� c1 J E4,� .°z l =, • i i' ! 1 i 1 .! S 040: I:V!1JL =1 NIT "i ( { ! ! I I ( ={ I I I I f� I } � �' •. I f I I F 1 ' I I I i ri L r31Sr'r':.FtG PER =0 0: P'.R, :i- 1 �`!� Ali* JIS Ll "D - -' r`�= E_ 4 .. P r:. F J CI T A.� / C I 1 / 111111••1.1• Lt.:!.111 111 •I•i.i•.. 1 1, rrI1 • 1. :I� 1 .. {11 'a I. 1 1 ` 1 1, 0.1 ,5 .G .! .J.J i.0 :v �i 5 7 U "J l0 '1 UUR2 Au 0.= PUDLIC ROADS CAPACITY OF GRATE hill' i_E s` 1N' SU.Mp f OIVISIC ?J T; W 1 10 Q A�,t U.C. Vrr,TE R PONoEo ON GRAT - TTY c 11 — PIPES FLOWING FULL OR PART -FULL A. Instructions For Us.( Pipe Flow Charts — P Flowing F or Part -Full 1. These charts are designed to enable direct solution of the Manning formula for full flow and for uniform part -full flow in circular pipes. Each chart applies to pipe of a certain diameter. The abscissa and ordinate scales represent discharge Q and normal velocity V for two roughness coefficients n, when read in co.tijunction with the superimposed lines for slope and normal depth of flow d 2.._J:,"p" ;rnd r :l ...... s;; : :�� :., !;v i.r�. charts for part -full flow apply only to pipe in which u f at riOrRlai depth has b?2ri established by sufficient length of pipe oil a con- stant slope when the flow is not affected by backwater. 3. Depth of uniform flow for a given discharge Q in a given size pipe on a given slope S and with roughness coefficients n = 0. 015 or 0. 024 may be determined directl from the chart for that size by entering on the appropriate Q -scale and reading depth at the intersection with the appropriate slope line (or an interpolated slope). Normal veloc- ity may be read on the appropriate V -scale opposite this same point. The procedure may be reversed to determine discharge at a given depth of flow. 4. Where the Q- ordinate intersects a slope line, S in the area near its right terminus, two alternate depths will be indicated if d is greater than 0. 82 diameter. For these cases, flow will occur at the lesser of the alternate depths. 5. For pipe roughness coefficients other than those of n =0. 015 or 0. 024 shown on the cl...rt scales, enter the chart on the im o „_al,. for n =0. 015 . tiz an. .,• c d vaiueof Q = design Q(n /0. 015) to determine depth and velocity. Read depth directly trom the chart at the pipe slope line, S, and obtain velocity by dividing the value read on the V- scale for n = 0. 015 by the same ratio n /0. 015. In reversing the above procedure to deter- mine design Q for a given depth, or agiven friction slope if the pine flows full, read Q on the scale for n = 0. 015 and divide by the ratio n /0. 015 to obtain the design Q. 6. Tb e— n)aximum_rate.of..dischaxge,,in uniform flow of any circular pipe on a given slope, not flowing under pressure, will occur with a depth of flow of b. 94 diameter. Therefore, to determine the maximum capacity of a pipe on a given slope S notflowing under pressure read the Q- ordinate for the appropriate value of n at the maximum value reached by the sharply curved slope line (depth equals 0. 94 diameter). Interpolated slopes follow the same pattern as the designated slope lines. 7. Where the Q- ordinate passes to the right of the sharply curved slope line for pipe slope. S the pipewillflow full and under pressure. For this case the charts may be used to deter- mine the slope of the pressure and energy lines, which are parallel when the pipe flows full. This sloe is the friction slope S or rate p l f, at which energy is lost by resistance to flow. Sf willbegreater than the pipe slope S Enter the chart with Q, or an adjusted Q = `. for the appropriate n value, intersect the line for depth equal to pipe diameter and read friction slope by interpolation between the short right. -angle marks indicating slope. The discharge capacity for a pipe f lowing full with a given friction Mope Sf is found by reading dischargeat the proper slope point along the line for depth equal to pipe diameter. 8. Flow at critical depth may occur in a e flowing with a free water surface that is P Y P�A 6 ,Part- ly full. Critical depth d for a given discharge is read by interpolation: from the depth lines at the point where the Q- ordinate on the a = 0. 015 scale and the critical curve intersect, j ,.n:._ regardless of pipe roughness. Critical velocity VC is the reading on the V- scale for n = 0. 015 for this Game paint. Critical depths greater than that represented by the last l - depth line on the charts, just less than a diameter, leave little significance since wave I action may intermitterOy fiil the pipe. Ii 11 -2 Y ,9. Where n = 0. 015, critical slope S is read at the critical depth point as found in 8 above. Critical slope will vary with pipe roughnness, therefore, to determine critical slope for other values of roughness coefficient it is first necessary to determine critical depth. Critical slope is then interpolated from the slope lines at the intersection of this depth with the Q from the scale for the appropriate v i!ue of n, or with an adjusted value of Q for values of n other than shown on chart (see 5 above 2 10. Critical depth d specific head at critical depth h critical slope S . d + 2 I �( —), pe Cl friction slope Sf, and relative velocity at constant discharge V /(Vfull) as well as rela- tive friction slope at constant discharge SF. � /(Sf full) c�t,� be determined directly by refer- ence to charts 46 through 79 (pp. 11- 22 to II -55), thus avoiding interpolation. The charts include all the common structural types. Xa �trance control curves are-based on expeririental data from a Bureau of Standards Re- search Project. The curves involving outlet control with a free water surface, on mild = - slopes, are based on backwater curves assuminn critical depth at the outlet. The limit- ing value of L /100S where entrance control no longer governs was based on the consid- eration of pressure plus momentum within the culvert. In cases of outlet control, errors are less than 6% with respect to more detailed analysis. 12.. Examples: a. Determine the depth and velocity of flow in a long 30 -in. concrete pipe, n = 0.015, on a 0. 5 percent slope (S = 0. 005) discharging 25 cfs. Enter chart 35 (p. II- 1G3 at Q = 25 on n = 0. 015 scale, follow up to intersection with line for slope S = 0.005, and read normal depth a = 2. 05 ft and normal velocity V = 5.8 fps. To find critical depth, enter chart at Q = 25 on n = 0. 015 scab, and read critical depth d = 1.7 ft at intersection with dotted critical curve. Also, critical velocity V = 7. 0 fps. d may Li A e verified on Chat 4t3. o b. Determine friction slope for a 30 -in. corrugated metal 2 ga pipe, n = 0.0.,1, on a slope S = 0.-008 ft /ft with a discharge Q = 25 cfs. Enter chart 35 at Q = 25 on the Q -scale for n = 0.024. Note that this ordinate faits to the right of the 0.008 slope line; there- fore, the pipe will flow full. Read friction slope Sf = 0.012 at the line for depth equal to pipe diameter. C. Determine the discharge for the pipe in example b if flowing at a depth of 1.4 ft. Enter chart 35 at the intersection of depth line 1.4 and slope line 0.008. Design dis- charge for n = 0. 024 equals 12 cfs. , Read ve locity on n = 0. 024 scale as V =4. 2 fps. d. Determine critical depth, critical velocity, and critical slope for a 60 -in. concrete pipe, n = 0. 015 discharging 160 cfs. Enter chart 41 (p. H -16) at Q = 160 on n = 0. 015 scale. At intersection with critical curve read d = 3. 6 ft, V = 10. 5 fps, and S = 0. 0065 ft /ft. t ,tea- 1/�, Tls As . si 24- .�i•� 00"ti O SL000o-- CHART 2 g o TT' q � P D I I ! .0 1 i {• � � ii � I ..� �. - \ � --`''' -100 i I I I a N - \11 E 00`0 {— �+— — — It �► �. J 0 1 , i I -- It 710 - 0 I r I y N CO ! 0 I O m i It 0 0 0 OG l to 4 o0 l co 0 to , - t t V 1 � — = ` U 1� - � i •t� � i I o l to — j ! Vp0O OV OO C90 ;.il \, c o 0 300,0, 00 00000 S /O' U Sdd - ^ - dl/0073A a om a m r. c h a a d /O' =U Q O mI to h R M H O h ►� b h 7"-M i PIPE FL 0W Cf A R r 20 oi 7� Type I - With Sil 0 or -- —�� ly.j, 2 - Vithreit sill .77; Icrcte Chinno [.•I• Lidth of Ce. _SELECTIC.71 OF RIPPO A FILTER piprC9 Filter glanket Velocity Pock Thickness Upper La.�Cr Lcti�r_L C3 Ft/Sec. Cla"Sificatior (1) Ft. Sec. 2W- s 40-3• cv 6-) ..3. 3 Zackin!j 3/1 C2 7-8 * No. 2 !ackinq . 1.0 1/4" B3 P-10 Facipi 1.4 3/8" 10-12 tirht 2.0 1/2•• - C I2 -14 1/4 Ton 2.7 $and 3/4" If-I& 112 Ton, 3:4 V ... S3nd zm 16-18 1 Ton 4.3 1 112 'Sand 18-20 1 2. Ton 5.4 2" Sand PI;A.Fi I ttr 03nket Thickness I Foot or Flo-w Z ,o c cf,00,cm- % I- V1 I I .4 30 or 31'! 7 r 0i1+ A- A 6' min Sec L • A Sill � • Class 8 concrete, 'PLAN if shown on Plans. • NOTES: Concrete Channel I- Type of riprap a Regular Quarry stone. b: Broken Concrete if S110-40 On Plans, C. Cobbles not acceptable. 2— Gradation and Placement as specified in Regional Standards Com, Ste, Spec. Prov, cr W Sec. .200-1.6. L. Z: -)F3_ Piprap is to be Placed over a filter 1/1, blan�et v.hi 11-2 VIA ch May be granular r8terial or plastic cloth. Granular r2terial specs. in Table above. b. Plastic cloth specs. in Peg. Stds, Co Std. • Spec. Sec. 200-1.6 • ELEVATION 2- 1) > Standard Specifications for Public Works Construction by So. CA Chap. of /%P',-.'A 1, ABC THE Sm. C-1160 SAN DIEGO REGIONAL STANDARD DRAWING Flev;*.;on et Aprro D.a1z - RIP RAP ENERGY DISSIPATOR En — 1 n MID B-40 It t GEOTECHNICAL INVESTIGATION ' 2926 Lone Jack Road Encinitas, California 1 ' HE THERINGTON ENGINEERING, INC. 1 ' ' HETHERINGTON ENGINEERING, INC. GEOTECHNICAL CONSULTANTS . ' February 26, 1991 Project No. 626.1 Mr. Thomas Frost 4255 Ocean Blvd. San Diego, CA 92109 ' Subject: GEOTECHNICAL INVESTIGATION 2926 Lone Jack Road ' Encinitas, California References: Attached Dear Mr. Frost: ' In accordance with your request, we have performed a geotechnical investigation at the subject site. The purpose of our investigation was to evaluate the property with respect to t geotechnical conditions, and to provide recommendations for precise grading and foundation design for a single- family residential addition and appurtenant improvements. We were ' provided with a previous geotechnical report for the site and a "Grading Plan for Building Addition and Pool," prepared by The Laret Company, undated, for the property which has been used as the base map for our attached Geotechnical Plan, Figure 1. As instructed by you, our scope of services has not included a comprehensive investigation of a possible ancient landslide within or adjacent to the site. ' With the above in mind, our scope of service has included the following: 1. Review of available published soil and geologic reports for the site and vicinity (see attached References); 2. Three backhoe excavations for visual observation, geologic mapping and soil /bedrock sampling; ., 3. Laboratory testing of representative samples obtained; 4. Engineering and geologic analyses of the data; and, ' 5. The preparation of this report presenting our findings, conclusions and recommendations along with the supporting data. ' 5245 AVENIDA ENCINAS • SUITE G • CARLSBAD, CALIFORNIA 92008 • (619) 931 -1917 GEOTECHNICAL INVESTIGATION Project No. 626.1 February 26, 1991 ' Page 2 PROPOSED DEVELOPMENT Based on discussions with you and review of the "Grading Plan for Building Addition and Pool," we understand that a detached, two to three - story, wood - frame, living area and garage addition is proposed. Conventional continuous /spread foundations with slab - on -grade ground floors are anticipated. Numerous retaining walls are proposed to a maximum height of 11 feet, retaining both level and 2:1 (horizontal to vertical) sloping backfill. Proposed appurtenant improvements include a swimming pool, play yard, driveway and other on -grade concrete flatwork. ' Proposed grading consists of designed cut to a maximum depth of approximately 14 feet and designed fill to a maximum depth of approximately 12 feet. Fill slopes are proposed to a maximum height of 20 feet and cut slopes to a maximum height of 6 feet. All fill slopes are at slope ratios of 2:1 (horizontal to vertical) or flatter. Cut slopes are indicated at both 1.5:1 and ' 2:1 slope ratios. Temporary cuts to a maximum height of 11 feet will be required for retaining wall construction. t SITE DESCRIPTION ' The subject site consists of a previously graded lot with an existing residence located in the Olivenhain area of Encinitas, California. The site is bounded by developed lots to the north and south, and open space to the west and east. ' Topographically, the site is characterized by the existing relatively level building pad which is situated on a south ' facing, overall 200+ feet high, 5:1 (horizontal to vertical) natural slope. RESEARCH Previous geotechnical reports were reviewed for the site and ' adjacent sites. The referenced report, by Tri City Engineers, for the subject property indicated that no geologic hazards were present and provided conventional grading and foundation ' recommendations for the existing structure. No as -built reports for the existing structure were located. The referenced Leighton and Associates report for two lots north of the subject property ' indicate both ancient and recent landsliding exists beneath these two lots. The limits of the ancient landslide are uncertain but HETHERINGTON ENGINEERING, INC. ' GEOTECHNICAL INVESTIGATION Project No. 626.1 February 26, 1991 1 Page 3 are inferred to be roughly contiguous with the north property line of the subject site. Leighton and Associates further ' concluded that residential development was "feasible provided mitigation of the existing landslide materials is provided." Specific mitigation measures were to be provided based on preliminary development plans. No other reports were found or reviewed. SUBSURFACE EXPLORATION Subsurface conditions were explored by excavating three test pits ' to depths ranging from 10.5 to 13 feet. The approximate locations of the test pits are indicated on the Geotechnical Plan, Figure 1. The test pits were excavated using a backhoe. The excavations were logged by a geologist from our office, who ' visually classified the soil (Unified Soil Classification System) and bedrock materials, and obtained bulk samples for laboratory testing. The Test Pit Logs are attached as Figures 3 and 4. 1 LABORATORY TESTING Laboratory tests were performed on the samples obtained during the subsurface exploration. Tests performed consisted of the following: 1. Dry Density /Moisture Content (ASTM: D 1188) 2. Atterberg Limits (ASTM: D 4318) 3. Direct Shear (ASTM: D 3080) ' 4. Expansion (ASTM: D 4829) 1 5. Particle Size Analyses (ASTM: D 422) Results of dry density /moisture content determinations are presented on the Test Pit Logs, Figures 3 and 4. The remaining ' laboratory test results are provided on Figures 5 through 7. SOIL AND GEOLOGIC CONDITIONS 1. Geologic Setting ' The subject property is situated on a portion of the coastal plain that is generally characterized by a number of Pleistocene marine terraces and rolling hill type topography ' that descends generally from areas of higher elevation east of the site down to the present day coastline to the west. HETHERINGT N ENGINEERING, NGINEERING, INC. GEOTECHNICAL INVESTIGATION Project No. 626.1 February 26, 1991 ' Page 4 The proposed construction site is underlain entirely by ' disturbed bedrock of the Tertiary age Scripps Formation which is in turn reportedly underlain at depth by marine sedimentary bedrock deposits of the Del Mar Formation. A relatively thin ' layer of colluvium overlies the disturbed bedrock. 2. Geologic Units a. Colluvium - A thin layer of surficial soils consisting of dry to moist, loose to medium dense, brown clayey sand was observed in the test pits. These soils were encountered to ' a maximum depth of 2 feet. b. Landslide Debris ( ?) - The entire site is underlain by ' disturbed bedrock materials of the Scripps Formation. These materials consist of green -gray sandstone, green claystone and mottled siltstone, sandstone and claystone. At this time, clear evidence relevant to the existence or absence of landsliding has not been observed. Due to the identified landsliding on property to the north and the visually disturbed nature of the bedrock materials on -site, I I, we are currently indicating this material to consist of slide debris. Remnant bedding and sheared, slickensided zones were mapped. Additional investigation would be ' necessary to make a more precise determination. 3. Groundwater No groundwater was observed in the test pits during our investigation. It should be noted, however, that fluctuations in the amount and level of groundwater may occur due to I variations in rainfall, irrigation, and other factors which may not have been evident at the time of our field investigation. ' SEISMICITY The site is within the seismically active southern California region. There are, however, no active or potentially active faults located within or adjacent to the site. Active faults within the general site region include the offshore extension of the Newport- ' Inglewood /Rose Canyon and the Elsinore fault zones which lie at distances of approximately 12 miles and 24 miles, respectively. Seismic risks on -site are limited to ground shaking during seismic ' events on active faults in the region. 1 ' HETHERINGTON ENGINEERING INC. GEOTECHNICAL INVESTIGATION ' Project No. 626.1 February 26, 1991 Page 5 The table below lists the known active and potentially active faults which would have the greatest impact on the site. t Maximum Probable Earthquake Estimated Bedrock Acceleration Fault (Moment Magnitude) Peak Repeatable Newport- Inglewood/ Rose Canyon (12 miles SW) 6.5 0.30g 0.19g Elsinore ' (24 miles NE) 7.0 0.188 0.18g ' SEISMIC EFFECTS 1. Ground Acceleration The most significant probable earthquake event to effect the property, would be a 6.5 magnitude earthquake on the Newport - Inglewood /Rose Canyon fault. Potentially, repeatable horizontal ground acceleration on the order of 0.19g is possible with a duration of strong ground motion exceeding 20 seconds. Peak (instantaneous) accelerations would be higher. 3. Landsliding The potential for future landsliding, whether seismically induced or otherwise is beyond the scope of our authorized work. Additional investigation, including deep borings both on- site and off -site, would be necessary to allow for 1 comprehensive analysis. 4. Ground Rupture ' Fault rupture on -site is not likely. However, ground cracks are possible during future seismic events, throughout southern California. CONCLUSIONS AND RECOMMENDATIONS 1 1. General The proposed construction is feasible from a geotechnical standpoint. As previously noted, possible ancient landsliding has been identified within the site area. At this time, the presence or absence of landsliding on the property has not been 1 ' HETHERINGTON ENGINEERING, ER NG, INC. GEOTECHNICAL INVESTIGATION Project No. 626.1 February 26, 1991 Page 6 conclusively determined. In order to comprehensively investi- gate the possible landsliding, deep borings and stability analyses would be required. The following recommendations are not intended to mitigate possible landslide associated ground movements. These recommendations are intended to create a residential addition which is compatible with the existing residence. Risk associated with possible landsliding cannot be evaluated without further subsurface work. 1 2. Slopes Cut and fill slopes should be inclined at 2:1 (horizontal to vertical) or flatter. Temporary slopes to facilitate retaining wall construction should be inclined at 1:1 (horizontal to vertical) or flatter. 3. Site Grading a. Clearing Existing vegetation and miscellaneous debris 1 should be cleared and removed from areas to be graded. Holes resulting from the removal of buried obstructions, which extend below finished site grades, should be replaced with compacted fill. b. Surface Soil Preparation After site clearing, colluvium within the limits of proposed fill placement and structural improvements should be overexcavated. Overexcavation depths on the order of 2.0 to 3.0 feet are expected. I ' Cut /fill transitions on the living area and garage building pads should be eliminated by overexcavation of the cut portion of the pad to provide a minimum of 3 feet of 1 compacted fill below pad grade. The overexcavation should extend at least 5 feet beyond the proposed structures. c. Scarification All areas to receive fill should, after the required excavations have been made, be scarified to a minimum depth of 6 to 8- inches, brought to near optimum moisture content, and compacted to at least 90 percent relative compaction. d. Compacted Fill All fill soils should be brought to near optimum moisture conditions, thoroughly blended to assure uniform moisture dispersal and compacted in 6 to 8 -inch thick layers to a minimum of 90 percent of the maximum density based upon ASTM: D 1557. Oversize (8- inches or larger) materials should not be incorporated into the fill. I HETHERIN T G ON ENGINEERING, INC. GEOTECHNICAL INVESTIGATION Project No. 626.1 February 26, 1991 Page 7 Fills constructed on slopes steeper than 5:1 (horizontal to vertical) should be keyed and benched into bedrock. The key should have a minimum width of 15 feet and minimum depth of 5 feet. ' Fill slopes should be overbuilt and cutback followed by grid rolling to achieve required compaction on the slope ' face. Subdrain systems will be required behind the fill key and beneath the canyon fill. These systems should consist of 4- ' inch diameter Schedule 40 perforated PVC pipe placed at the base of the key or bottom of the canyon, surrounded with a minimum of 3 cubic feet per lineal foot of crushed rock for the fill key drain and 9 cubic feet per linear foot of crushed rock for the canyon drain. ' 3. Foundation and Slab Recommendations The proposed structure may be supported on conventional ' continuous /spread footings bearing in compacted fill soils. Footings should extend to a minimum depth of 24- inches into compacted fill. Footings located adjacent to utility trenches should extend below a 1:1 plane projected upward from the inside bottom corner of the trench. All footings should be reinforced with a minimum of two #5 bars, one top and one bottom. 1 Footings located adjacent to sloping ground should be extended to a sufficient depth to provide at least 10 feet of horizontal ' distance between the footing and the face of slope. Footings bearing as recommended may be designed for a dead plus live load bearing value of 1500 pounds per square foot. This value may be increased by one -third for loads including wind or seismic forces. A lateral bearing value of 250 pounds per square foot per foot of depth and a coefficient of friction between foundation soil and concrete of 0.4 may be assumed. These values assume that footings will be poured neat against the foundation soils. Footing excavations should be inspected I by the Geotechnical Engineer prior to the placement of steel to ensure that they are founded in suitable bearing materials. An 24 -inch deep grade beam should be placed across the garage door opening and reinforced as for footings. HETHERINGTON ENGINEERING, INC. 1 GEOTECHNICAL INVESTIGATION Project No. 626.1 February 26, 1991 Page 8 ' On -grade floor slabs should be at least 4- inches thick and reinforced with No. 3 bars spaced at 12- inches center to center ' in two directions. Reinforcement should be placed on chairs so that the reinforcement is in the center of the slab. Floor slabs should be underlain by 1 -inch of clean sand over a 6 -mil 1 visqueen moisture barrier over 4- inches of rounded gravel or clean sand. Slab subgrade soils should be presaturated to 5% over optimum ' moisture content to a depth of 24- inches and verified by the Geotechnical Engineer prior to pouring concrete. ' 4. Retaining Walls Retaining walls free to rotate (cantilevered walls) should be designed for an active pressure of 45 pounds per cubic foot, equivalent fluid pressure, assuming level backfill consisting of the on -site soils. Walls with a 2:1 (horizontal to vertical) surcharge should be designed for an active pressure ' of 60 pounds per cubic foot, equivalent fluid pressure, respectively. ' Walls restrained from movement at the top should be designed for an additional uniform soil pressure of 8xH pounds per square foot where H is the height of the wall in feet. Any additional surcharge pressure behind the wall should be added 1 to these values. Retaining wall footings may be founded in compacted fill and /or ' terrace deposits and should be designed in accordance with the previous building foundation recommendations. Retaining walls should be provided with adequate drainage to '1 prevent buildup of hydrostatic pressure and should be adequately water - proofed. 5. Trench and Retaining Wall Backfill All trench and retaining wall backfill should be compacted to at least 90 percent relative compaction (ASTM: D 1557) and tested by the geotechnical consultant. ' 6. Site Drainage The following recommendations are intended to minimize the potential adverse effects of water on the structure and appurtenances. a. Consideration should be given to providing the structure with roof gutters and downspouts. HETHERINGTON ENGINEERING, INC. GEOTECHNICAL INVESTIGATION Project No. 626.1 February 26, 1991 Page 9 b. All site drainage should be directed to the street and not ' allowed to flow over slopes. C. No landscaping should be allowed against the structure. Moisture accumulation or watering adjacent to footings can result in deterioration of wood /stucco and may adversely effect footing performance. d. Irrigated areas should not be over - watered. Irrigation should be limited to that required to maintain the vegetation. Additionally, automatic systems must be ' seasonally adjusted to minimize over - saturation potential particularly in the winter (rainy) season. e. All slope, yard, and roof drains should.be periodically checked to verify they are not blocked and flow properly. This may be accomplished either visually or, in the case of subsurface drains, placing a hose at the inlet and checking the outlet for flow. 7. Grading Plan Review ' Final grading and foundation plans should be reviewed by the geotechnical consultant to confirm conformance with the recommendations presented herein or to modify the recommendations as necessary. LIMITS OF INVESTIGATION The analyses, conclusions and recommendations contained in this report are based on site conditions as reported by others and as they existed at the time of our investigation, and further assume the excavations to be representative of the subsurface conditions throughout the site. If different subsurface conditions from those ' encountered during our exploration are observed or appear to be present in excavations, the Soils Engineer and Geologist should be promptly notified for review and reconsideration of ' recommendations. Our investigation was performed using the degree of care and skill ordinarily exercised, under similar circumstances, by reputable ' Soils Engineers and Geologists practicing in this or similar localities. No other warranty, express or implied, is made as to the conclusions and professional advice included in this report. HETHERINGTON ENGINEERING, INC. GEOTECHNICAL INVESTIGATION Project No. 626.1 February 26, 1991 ' Page 10 ' This opportunity to be of service is sincerely appreciated. If you have any questions, please call. ' Sincerely, HETHERINGTON ENGINEERING, INC. PAUL A. BOGSETHS RIM Certified Engine ing Geologist 1153 Civ' er 30488 ' (expires 6/30/92) Geotechnica/l Engineer 397 (both ex 92) MDH PAB ss ' cc: 6 Address �f Attachments' �; �� +� No. 397 s.� E.G. 1153 ` M OF mW HETHERINGTON ENGINEERING, INC. ' REFERENCES Landslide Hazards in the Rancho Santa Fe Quadrangle, CDMG OFR 86- ' 15LA, 1987. "Report of Soil Investigation for APN 264- 160- 32...," by the Tri- ' City Engineers, dated January 4, 1982. "Supplemental Geotechnical Evaluation, Proposed Two Lot Residential Subdivision, 2920 Lone Jack Road...," by Leighton and Associates, Inc., dated June 25, 1990. ' AERIAL PHOTOS Flight SDPD, June 17, 1974 ' Flight AXN, 1953 -1959 ' HETHERINGTON ENGINEERING IN , . _ C 1� 1 1 EGEND 1 'ROXI MATE LOCATION 1 % TEST PI T ti KE AND DIP OF BEDDING 1 LIKE AND DIP OF SHEAR p Z W k )LOGIC CROSS SECTION Z 1 w i y ti W 1 � t h Q 0 _ IL IL 1 r W 1 L r 1-' Z H co i 0 EE W W a U W 1 Z 0� Z z ORTH 1 WO U LE: 1's Z 32' J O v 1 �z Z = � U 1 WW 2 0 F— O W W = t7 1 ' 234 234 218 EXISTING LIMITS OF 218 RESIDENCE PROPOSED ADDI TI ON ' 202 - 202 TP -1 186 '�� -- - - -� _ TP- 2 186 l rj - 170 PROPOSED GRADE U 170 ' 154 154 A TREND N 10W A' ' GEOLOGIC CROSS SECTION HETHERINGTON ENGINEERING I FROST RESIDENCE GEOTECHNICAL CONSULTANTS PROJECT NO. 828.1 I FIGURE NO. 2 ' BACKHOE COMPANY: Bob Welch BUCKET SIZE: 18" DATE: 1/24/91 w ¢ cn F W J H H ,� w w SOIL DESCRIPTION C <E z W M z 0. H z X H W TEST PIT NO. TP -1 ELEVATION: 194 ' o�' ¢¢ww 0w a oo� o� F- O 0 � E U � (A � 0 SC COLLUVIUM Brown clayey fine sand, dry to moist, loose to medium dense, desiccated in upper one foot ' SLIDE DEBRIS(?) Orange and light gray silty fine sandstone, moist, loose to medium dense, several (approximately 6 inch) zones of brown silty sand, friable ' S ...................................................................................................................... ............................... Gray silty claystone, moist, firm to stiff, caliche blebs, 93 24.4 mottled zones with numerous micro - slicks, variable consistency, yellow and rust staining along fractures @ 6 feet (middle of trench): general contact of sandstone and 10 claystone: N65E /25NW ' @ 6.5 feet (south side): general trend of yellow sand laminae (not continuous): N45E /23NW @ 7 fLiandstone, t (south side): general trend of 1/4" olive green silt not continuous): N40E /25NW ............................................................................................................. ..............................: ' (middle of trench): light gray silty fine to medium 15 moist, medium dense Total depth: 12.5 feet ' No groundwater No caving ' 20 TEST PIT NO. TP -2 ELEVATION: 181 0 ' SC COLLUVIUM Brown clayey sand, dry to moist, loose to medium dense, desiccated in upper one foot SLIDE DEBRIS(?) Green, light gray, and orange silty fine sandstone, moist, loose to medium dense, friable 5 @ 4.5 feet: grades to claystone, moist, firm, numerous micro - slicks ...................................................................................................................................... ............................... t Light gray silty fine to medium sandstone, moist, dense, friable, (fades out halfway through trench, other half of trench is claystone) .....................................................................-............................................................... ..............................: ' 10 Green clay and claystone, moist, firm to stiff, fractured, numerous micro - slicks, blebs of sandstone, variable consistency @ 7 feet: general trend of contact: N28E /10NW @ 8 feet (south side): orange and light gray silty fine sandstone :........... _ .......................... ............................... _.................. _............................................ ..............................: ' Grades to light gray and orange sand and sandstone, moist, loose to medium dense, several roots :...................................................................................................................................... ..............................: 15 Green claystone, moist, stiff ' @ 12.5 feet: Approximately 1/2" thick remolded clay seam, olive green clay, very moist, soft, several slick surfaces, N80E /05NW, N -S /25E ' Total depth: 13 feet 20 — No groundwater, No cavin ' LOG OF TEST PITS HETHERINGTON ENGINEERING Frost Residence ' GEOTECHNICAL CONSULTANTS PROJECT NO. 626 I FIGURE NO. 3 t BACKHOE COMPANY: Bob Welch BUCKET SIZE: 18" DATE: 1/24/91 vi I W ¢ cis .-. J H i ., w SOIL DESCRIPTION W 0r- (n >Z U HZ�. H m N o � o wo a = U , N TEST PIT NO. TP -3 ELEVATION: 179 0 SC COLLUVIUM Brown clayey fine sand, dry to moist, loose to medium dense, desiccated in upper one foot ' SLIDE DEBRIS( ?) : Light gray and green clayey to silty fine sandstone, moist, medium dense, friable; zones of dense green sandstone, several concretions ' S .............................................................................................................................. ............................... @ 6 feet (nort h side): green cIaystone and sandstone with light gray and orange friable sand lenses, moist, firm and medium dense to dense 10 @ 9 feet (north side): concretions, appear to be fractured, surrounding sand and clay matrix appears glazed at one ' location (concretions @ 5 feet on south side of hole) Total depth: 10.5 feet No groundwater No caving 15 t 20 1 LOG OF TEST PITS ' HETHERINGTON ENGINEERING Frost Residence ' GEOTECHNICAL CONSULTANTS PROJECT NO. 626 I FIGURE NO. 4 3000 2500 .................. . ..... ....... ........... ............................................................ .................................. .................................... .................................... 2000 .............. ... ................ ................ ................... .................................... ..... . .... ....... . .............. : ....... ..............................> ... ... ......................... 4- CD Z 1500 ........................................................................ .......................... ....... . ................................... .................................... .......................... ....... Cn Cn w 1000 .................. .......... i ........................ ...... ..................... ................... ............................... • 500 ................ ... .............. ......................... . .............................. ......... .......... ......... .................................... 0 0 500 1000 1500 2000 2500 3000 NORMAL PRESSURE (psf) SYMBOL SAMPLE LOCATION COHESION FRICTION ANGLE REMARKS ' • TP-1 at 7.0 200 23 remolded to in-situ density, saturated, drained DIRECT SHEAR TEST RESULTS HETHERINGTON ENGINEERING Frost Residence GEOTECHNICAL CONSULTANTS PROJECT NO. 626.1 I FIGURE NO. 5 ' U.S. STANDARD SIEVE SIZES HYDROMETER 3 1 3/4 3/8 4 8 16 20 30 40 50 100 200 100 100 ............ .... ....... ......`:................... ....... ....:.... . E i ..: ............ : go 80 .... ............................... ...... ... _ ... __ _ _.... E :.. ...E....:.... 70 ...........................t ......... ...... .. _ ... _ .. .. _ ....... _ .... 0 s .. . t ..:... ....:..... W .... ....... .....................t......... _ ... _ _ .. _ ....... _ .... ......... 60 W Z Z H ......... ILL H <L Z 50 ...................... `.....:......... ...... _ _ _ _ _ .... Z ' W W U U L W LLJ .. ...:.... ............ 0 20 .. ............. `:.... ... s...s...€ ....... _ _ _ _ ....... _ .... .. ...... ...:....:. 10 ............... .... ... ........ ...`......_ ...... _ . _ _ _ _ .... .. ...... 0 .......[........ ......:.... 0 0 ' 100 10 1 0.1 0.01 0.001 GRAIN SIZE (mm) ' COBBLES GRAVEL SAND Coarse Fine Coarse Medium Fine SILT and CLAY t SYMBOL SAMPLE LOCATION FIELD % PASSING % FINER UNIFIED SOIL MOISTURE ( %) NO. 200 SIEVE 2 MICRONS CLASSIFICATION ' TP -3 at 4.0 34 ' GRADATION TEST RESULTS HETHERINGTON ENGINEERING Frost Residence ' GEOTECHNICAL CONSULTANTS PROJECT NO. 626.1 I FIGURE NO. 6 1 ' t LABORATORY TEST RESULTS Expansion (ASTM: D 4829) ' Expansion Expansion Sample Location Index Potential ' TP -1 @ 7' 113 High TP -3 @ 4' 62 Medium ATTERBERG LIMITS (ASTM: D 4318) Unified ' Sample Liquid Plastic Plasticity Soil Location Limit Limit Index Class ' TP -1 @ 7 44 21 23 CL ' Project No. 626.1 Figure No. 7 I' 1 1 ' _ �o Jai es A. Laret, P.E. i Dana M. Seguin, P.L.S. LAND DEVELOPMENT ENGINEERING • PLANNING • SURVEYING Client No. 251 0V D 3 1J% City Engineer vIG6 City of Encinitas ENGIN EERING S NR AS 505 S. Vulcan Avenue 61V GF ENG Encinitas, CA 92024 -3633 FINAL GRADING ENGINEER'S REPORT FOR FROST RESIDENCE GRADING PERMIT NO. 1170 -G Pursuant to section 23.24.310 of, the Encinitas Municipal Code, this letter report is hereby submitted as a final grading report for the subject project. As supervising grading engineer on the project, I hereby state all grading, lot drainage, and drainage facilities on the site have been completed and installed in conformance with the approved plans and requirements of the City of Encinitas Codes and Standards. I have inspected the site and found the embankment and cut slopes to have been cut to their proper line and grade in conformance with sections 23.24.450 through 23.24.500. All building pad sizes, elevations, drainage and berming have been completed in substantial compliance with the approved plans and any approved revision thereto. In addition, in my professional opinion, all work incorporated in the landscape and irrigation plans authorized under the P ermit have been constructed in accordance with the approved plans, any approved revisions thereto and Section 23.24.510 of the Encinitas Municipal Code. An "As- Built" grading plan has been corn pteted ' T r or under my direction and has been submitted to the City for review aKd `p rQva( N. , A t, Ja es A. Laret, RCE 29W 5708 Calzada Del Bosque • (619) 756 -9374 P.O. Box 9661, Rancho Santa Fe, CA 92067 • Fax (619) 756 -4231 ' AS- GRADED GEOTECHNICAL REPORT Proposed Building Addition and Appurtenances ' 2926 Lone Jack Road Encinitas, California �1 1 1 ' 3 NOV 1 1991 ' CITY OF ENCINITAS DEPT. OF PUBLIC WORKS ENGINEERING DEPT. HETHERINGTON ENGINEERING, INC. HETHERINGTON ENGINEERING, INC. GEOTECHNICAL CONSULTANTS ' October 31, 1991 Project No. 626.1 ' Mr. Thomas Frost 4255 Ocean Blvd. ' San Diego, CA 92109 Subject. AS- GRADED GEOTECHNICAL REPORT Proposed Building Addition and Appurtenances ' 2926 Lone Jack Road Encinitas, California ' References: Attached ' Dear Mr. Frost: In accordance with your request, we have performed geotechnical services in conjunction with grading at the subject site. The ' grading was conducted in September and October 1991. The purpose of the grading was to create building pad areas for the proposed building addition and appurtenances in a manner consistent with the ' existing structure. As discussed in Reference 4, the grading was not intended to mitigate possible future damage due to landslide associated ground movement. Our services consisted of compaction testing and observation of grading, geological observations, ' laboratory testing and the preparation of this report which presents the results of our testing and observations, and our conclusions and recommendations. SITE GRADING ' Prior to grading, the site was cleared of surface obstructions, vegetation and debris. In areas to receive fill, existing colluvium was removed. The exposed materials were scarified to a depth of 6 to 8- inches, brought to near optimum moisture conditions and recompacted to at least 90 percent relative compaction as determined by ASTM: D 1557A. The approximate elevations of the ' bottoms of the removals are indicated on the accompanying Plot Plan, Plate 1. 1 Fill placement occurred over the southeastern portion of the site to create building pad areas for the proposed addition and appurtenances, and over the southwestern portion of the site to create a level "play yard" area. The limits of fill placement are ' shown on the Plot Plan, Plate 1. A fill key was constructed at the south end of the "play yard" ' fill. A backdrain was constructed along the bottom of the fill key I ' 5245 AVENIDA ENCINAS • SUITE G • CARLSBAD, CALIFORNIA 92008 • (619) 931 -1917 ' AS- GRADED GEOTECHNICAL REPORT Project No. 626.1 October 31, 1991 Page 2 ' as shown on the Plot Plan, Plate 1. The backdrain consisted of a fl- inch diameter perforated schedule 40 PVC pipe surrounded by 9 cubic 1 feet per lineal foot of 3/4 -inch crushed rock wrapped in filter fabric. A 66 foot long, 12 -inch diameter, corrugated metal pipe was installed along the western side of the site. Extending from a grated inlet at the northwest corner of the property and entering the "play yard" fill at a second grated inlet, the drain daylights into 6 to 12 -inch diameter rock at the toe of the 2:1 (horizontal to vertical) fill slope. We understand that the final as- graded pad elevation for the "play yard" fill was approximately 4 feet higher than the elevations shown on the referenced "Grading Plan..." (Reference 6). ' A fill key was also constructed along the southeast corner of the fill pads for the proposed addition and appurtenances as shown on the Plot Plan, Plate 1. Overexcavations on the order of 3 feet ' deep were performed in the areas of the building addition to eliminate cut /fill transitions. SOIL TYPES The soils utilized as fill consisted of on -site materials generally 1 composed of light red -brown silty sand, gray -green silty clay, green -brown sandy clay and red - orange slightly clayey silty sand. FILL PLACEMENT Fill soils were laced in 6 to 8 -inch P thick, near horizontal lifts, moisture conditioned to near optimum moisture content, and compacted by mechanical means to a minimum of 90 percent relative compaction as determined by ASTM: D 1557A. Compacted fill was benched into temporary 1:1 cut slopes at the margins of the removals. Compaction was achieved by track rolling with a ' Caterpillar D4H dozer and a Caterpillar 963 loader. Fill was placed in general accordance with the geotechnical guidelines presented in Reference 4. ' Density tests were performed in accordance with ASTM: D 1556 (Sand - Cone Method) and ASTM: D 2922 (Nuclear Guage Method). The results ' of the density tests are presented on the attached Summary of Field Density Tests, Table I. The approximate locations of the field density tests are indicated on the accompanying Plot Plan, plate ' 1. Optimum moisture content /maximum dry density determinations of soils utilized as fill are presented on the attached Summary of Maximum Dry Density /Optimum Moisture Content Determinations, Table II. HETHERINGTON ENGINEERING, INC. ' AS- GRADED GEOTECHNICAL REPORT Project No. 626.1 October 31, 1991 Page 3 GEOLOGIC OBSERVATIONS Geologic mapping performed during grading at the subject site and a review of geotechnical reports for properties in the site vicinity, further support the possibility that a landslide or remnants of a ' landslide exist on your property. Geologic structure observed in temporary cut slopes during site grading indicate. bedding generally strikes N70 -80 degrees E and dips to the north at 25 to 40 degrees. Bedding attitudes were obtained on sand lenses and layers, within siltstone and claystone beds. Geologic attitudes and locations are available in our files. In order to ' comprehensively investigate the possible landsliding, deep borings and stability analyses would be required. CONCLUSIONS AND RECOMMENDATIONS 1. General ' Based on our observations and the results of our testing, it is our opinion that the subject grading has been performed in ' general conformance with the recommendations contained in Reference 4. The grading and following foundation recommendations are not intended to mitigate possible landslide associated ground movements. The recommendations are intended to create a residential addition and appurtenances which are consistent ' with the existing residence. Risk associated with possible landsliding cannot be evaluated without further subsurface work. ' 2. Foundation and Slab Recommendations The proposed structure may be supported on conventional ' continuous /spread footings bearing in compacted fill soils. Footings should extend to a minimum depth of 24- inches into compacted fill. Footings located adjacent to utility trenches ' should extend below a 1:1 plane projected upward from the inside bottom corner of the trench. Footings located adjacent to sloping ground should be extended to a sufficient depth to provide at least 10 feet of horizontal distance between the ' footing and the face of slope. Continuous footings should be reinforced with a minimum of two #5 bars, one top and one bottom. ' HETHERINGTON ENGINEERING INC. AS- GRADED GEOTECHNICAL REPORT ' Project No. 626.1 October 31, 1991 Page 4 ' Footings bearing as recommended g q may be designed for a dead plus live load bearing value of 1500 pounds per square foot. This ' value may be increased by one -third for loads including wind or seismic forces. A lateral bearing value of 250 pounds per square foot per foot of depth and a coefficient of friction ' between foundation soil and concrete of 0.4 may be assumed. These values assume that footings will be poured neat against the foundation soils. Footing excavations should be inspected ' by the Geotechnical Engineer prior to the placement of reinforcing steel to ensure that they are founded in suitable bearing materials. ' A 24 -inch deep grade beam should be placed across the garage door opening and reinforced as for footings. ' On -grade floor slabs should be at least 4- inches thick and reinforced with No. 3 bars spaced at 12- inches center to center in two directions. Reinforcement should be placed on chairs so that the reinforcement is in the center of the slab. Floor ' slabs should be underlain by 1 -inch of clean sand over a 6 -mil visqueen moisture barrier over 4- inches of rounded gravel or clean sand. Slab subgrade soils should be presaturated to 5% over optimum moisture content to a depth of 24- inches and verified by the ' Geotechnical Engineer prior to pouring concrete. 3. Retaining Walls ' Retaining walls free to rotate (cantilevered walls) should be designed for an active pressure of 45 pounds per cubic foot, equivalent fluid pressure, assuming level backfill consisting ' of the on -site soils. Walls with a 2:,1 (horizontal to vertical) surcharge should be designed for an active pressure of 60 pounds per cubic foot, equivalent fluid pressure, respectively. Walls restrained from movement at the top should be designed for an additional uniform soil pressure of 8xH pounds per ' square foot where H is the height of the wall in feet. Any additional surcharge pressure behind the wall should be added to these values. ' Retaining wall footings may be founded in compacted fill and /or terrace deposits and should be designed in accordance with the ' previous building foundation recommendations. ' HETHERINGTON ENGINEERING, INC. 1 ' AS- GRADED GEOTECHNICAL REPORT Project No. 626.1 October 31, 1991 Page 5 Retaining walls should be provided with adequate drainage to prevent buildup of hydrostatic pressure and should be adequately water - proofed. 4. Trench Backfill ' All trench backfill should be compacted to at least P 90 percent relative compaction and tested by the Geotechnical Engineer ' during placement. 5. Site Drainage ' The following recommendations are intended to minimize the potential adverse effects of water on structures and appurtenances. a. Consideration should be given to providing structures with roof gutters and downspouts; ' b. All site drainage should be directed away from structures and not allowed to flow over slopes; ' C. No landscaping should be allowed against foundation structures. Moisture accumulation or watering adjacent to foundations can result in deterioration of wood /stucco and ' may effect foundation performance; d. Irrigated areas should not be over - watered. Irrigation 1 should be limited to that required to maintain the vegetation. Additionally, automatic systems should be seasonally adjusted to minimize over - saturation potential ' particularly in the winter (rainy) season; e. All slope, yard, and roof drains should be periodically checked to verify they are not blocked and flow properly. ' This may be accomplished either visually or, in the case of subsurface drains, placing a hose at the inlet and checking the outlet for flow. ' HETHERINGTON ENGINEERING, INC. ' AS- GRADED GEOTECHNICAL REPORT Project No. 626.1 October 31, 1991 ' Page 6 ' LIMITATIONS Our testing and observation was performed using the degree of care ' and skill ordinarily exercised, under similar circumstances, by reputable Geotechnical Consultants practicing in this or similar localities. No other warranty, express or implied, is made as to the conclusions and professional advice included in this report. ' If there are any questions regarding this report, please feel free to call. We appreciate this opportunity to be of service. ' Very truly yours, HETHE IN O G RING, INC. ,0 c M E ERI D G PAUL A. BOGSETH A• Bp ' En r 80 10 # Certified Engine, Geologis� J 3 Geotechnic En "#$'7 c;,. (expires 6/30/ E.G. 11 (both expir ti /92) Rio. 397 �P� Ea.o.____,_w_• J I '3 "_ �ql�. �✓ � �➢ , y ,L' 4 '� CHRIS HOSKIN '`e•\�OF CALW � r � s � Staff Engineer HETHERINGTON ENGINEERING, INC. ' REFERENCES 1) Landslide Hazards in the Rancho Santa Fe Quadrangle, CDMG OFR ' 86 -15LA, 1987. 2) "Report of Soil Investigation for APN 264- 160- 32...," by the ' Tri -City Engineers, dated January 4, 1982. 3) "Supplemental Geotechnical Evaluation, Proposed Two Lot Residential Subdivision, 2920 Lone Jack Road.... 11 by Leighton and Associates, Inc., dated June 25, 1990. 4) "Geotechnical Investigation, 2926 Lone Jack Road, Encinitas, California," by Hetherington Engineering, Inc., dated February 26, 1991. 5) "Preliminary Geotechnical Investigation, 2916 Lone Jack Road, ' Encinitas, California," by Ninyo & Moore, dated March 9, 1989. ' 6) "Grading Plan for Frost Residence," by James A. Laret, dated March 13, 1991. ! 7) Aerial Photos Flight AXN, 1953 -1959 Flight SDPD, June 17, 1974 HETHERINGTON ENGINEERING, INC. ' TABLE I SUMMARY OF FIELD DENSITY TESTS (ASTM: D 1556) ' Comments and Moisture Dry Relative Test Test Test Elevation Content Density Soil Compaction No. Date (MSL) (-%) (-%) Test ( %) 1 9/23/91 153.5 19.9 103.5 2 90 2 9/23/91 154.5 17.1 109.5 1 94 ' 3 9/24/91 157.0 15.7 116.5 3 91 4 9/25/91 165.0 19.4 107.7 3 92 5 9/26/91 163.0 16.4 104.6 3 90 6 9/26/91 167.0 14.1 105.1 1 90 7 9/26/91 170.0 15.4 104.3 3 90 8 10/10/91 170.0 16.2 101.0 2 88 (Failed) ' 9 10/10/91 170.0 16.3 103.4 2 90 (Retest of 8) 10 10/10/91 166.5 11.8 107.2 1 92 ' 11 10/10/91 186.5 16.1 101.9 4 85 (Failed) 12 10/10/91 185.5 15.6 99.9 '4 83 ' (Failed) 13 10/14/91 186.0 19.8 104.6 2 91 (Retest of 11 & 12) 14 10/14/91 189.0 17.0 110.3 1 92 ' 15 10/15/91 190.0 12.1 100.0 1 85 (Failed) 16 10/15/91 170.0 18.5 107.1 1 92 17 10/16/91 171.5 16.4 104.5 3 90 18 10/16/91 F.G. 19.3 104.9 1 90 19 10/16/91 189.0 19.2 108.8 5 92 ' 20 10/16/91 190.5 19.0 110.5 4 92 (Retest of 15) 21 10/18/91 F.G. 17.4 108.2 4 90 22 10/18/91 174.5 20.5 106.3 2 92 ' 23 10/21/91 175.5 21.4 104.8 2 91 24 10/22/91 173.5 17.2 106.2 5 90 25 10/23/91 178.5 18.4 105.4 3 90 1 ' TABLE II Maximum Dry Density /Optimum Moisture Content Determinations ' (ASTM: D 1557A) ' Optimum Maximum Dry Density Moisture Content Soil Type Soil Description (pcf) (o) 1 Light red -brown silty sand 117.0 13.0 ' 2 Gray -green silty clay 115.0 16.0 III' 3 Red -brown silty sand with 116.5 13.5 gray -green silty clay 4 Green and brown sandy clay 120.5 12.5 t 5 Red - orange slightly clayey 118.0 13.0 silty sand