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HomeMy WebLinkAboutMiscBERGERIASAM ENGINEERS INC. 33301 Ninlh Avenue South , Sulte 300 Federal Way, Weahinplon 98003.2600 206/431.2300 • FAX 2061431.2250 5 May 2006 Mr. Daniel Bretzke 1313 33rd Avenue South Seattle, WA 98144 BERGER/AB" E N G I N E E R S 1 N C Subject: Wetland Report and Buffer Averaging Analysis Dear Mr. Bretzke: PLANNING ENGINEERING ENVIRONMENTAL PROGRAM MANAGEMENT DEVELOPMENT NIdGrry ENON SEp 2 7 2007 RECEIVED BERGER/ABAM Engineers Inc. is pleased to submit our wetland report and buffer averaging analysis to you for the property located at 5521 SE Oth Street, Renton, Washington (King County Tax Parcel Nos. 1023059358, 1023059359 and 1.023059360). This report and analysis is provided in the attachments as follows. Attachment A: Wetland Report complete with figures and data, sheets Attachment B: Buffer Averaging Analysis complete with figures These deliverables complete our contractual requirements with you for this project. We thank you for the opportunity to assist you with this project and look forward to working with you in the future. Sin erely, Jeffre B. Thomas Senior Environmental PIanner JBT:dls Attachments Attachment A Wetland Report 17 February 2006 Table of Contents Section Page I. Introduction.......................................................................................................................................1 1I. Background information.................................................................................................................1 A. Location....................................................................................................................................1 B. Geomorphic Context..............................................................................................................2 C. Climate and Growing Season...............................................................................................5 D. Land -Use History...................................................................................................................6 III. Methodologies...................................................................................................................................6 A. Rationale for the Determination of the Subject Site Wetland Boundaries ......................6 B. Office Methods........................................................................................................................8 C. Field Delineation.....................................................................................................................8 IV. Results..............................................................................................................................................11 A. Data Points................................................................................................... ....................12 B. Boundary Flags.....................................................................................................................17 V. References........................................................................................................................................18 ImageNo.1: Subject Site..........................................................................................................................2 Image No. 2: Sampling for Hydric Soils...............................................................................................10 Figure1— Vicinity/Site Map.....................................................................................................................3 Figure2 — Basin/Soils Map........................................................................................................................4 Figure 3 — Site Aerial/Topo Map...................................................................... Figure 4 — Data Point Locations..............................................................................................................13 Table No.1: USFWS Plant Indicator Status Categories as modified by the National List of Plant Species that Occur in Wetlands: Northwest - Region IX .............................11 Appendix I — Field Study Data Sheets..................................................................................................19 Wetland Report BERGERIABAM, A06I12 17 February 2006 Page i of i I. Introduction BERGER/ABAM Engineers Inc. has been retained by Daniel Bretzke to conduct a wetland delineation on the property known as 5521 SE 10th Street, Renton, Washington (King County Tax Parcel Nos. 1023059358,1023059359, and 1023059360). The site is located within S10, T23N, R5E and the City of Renton incorporated limits (approximate Latitude 47.29 N and Longitude-122.08 W). This report provides background information, methodologies and the results of the field work. The field work was completed during a two-day period from 6 February 2006 to 7 February 2006 pursuant to Renton Municipal Code (RMC) (4)(3)(050)(M)(4a) using the procedures provided in the Washington State Wetlands Identification and Delineation Manual, as developed by the Washington State Department of Ecology, March 1997, Ecology Publication 96-94. This report has been prepared by BERGER/ABAM Engineers Inc. for exclusive use by Mr. Bretzke as required documentation for Iand use actions with the City of Renton. No other persons may use the information contained in this report for commercial purposes without express written consent of both BERGER/ABAM Engineers Inc. and Daniel Bretzke. II. Background Information A. Location The site consists of three adjacent tax parcels that are located on the south side of SE 10th Street, approximately 300 feet west of 148th Avenue SE as depicted by Figure 1 — Vicinity/Site Map. There is one large wetland in part on the south-west corner of the site that follows Honey Creek drainage sub -basin. The limits of this wetland delineation are the boundaries of the site. Image No.1 is a photo of the site taken from a vantage point above the landscape. Wetland Report 17 February 2006 BERGER/ABAM, A06112 Page 1 of 1 Image No. 1: Subject Site B. Geomorphlc Context The site is part of the May Creek drainage basin and the Cedar River/Lake Washington watershed as mapped in WRIA No. 8 and shown in Figure 2. The geomorphology of this area consists of outwash till plains, terraces, and glacial till plains (Gale, Pringle, and Snyder;1973). The immediate area is characterized by rolling hills and supports a complex of wetlands and uplands that has undergone significant landscape alterations including clearing and filling activities. There are three soils located on or near this site as shown in Figure 2 by the Soil Survey of King County Area (Gale, Pringle, and Snyder;1973). The mapping symbols and slope classes of the three alderwood subgroups are as follows. AgB: 0 to 6% Slopes AgC: 6 to 15% Slopes AgD:15 to 30% Slopes Wetland Report 17 February 2006 BERGER/ABAM, A06112 Page 2 of 2 S� 1 7•S �. j 1 1•. f 1• � v •�� _.. 1 0 I In P A. May Creek Sub -Basin Catchment Basin # MAYCO08 0 May Creek Sul Catchment Basin NE.10th St./_SE 116th St,-J wI Zn m Legend Source: King County GIS / NRCS Sails Survey ©Catchmem Bub -basin Boundary ' AgB = Figure 2- Basin 1 Soils Map mmm— Stream . AgC ®Subject Property ParcelSaundaries AgO 1 inch equals 200 feet Tax Parcels The King Conservation District describes Alderwood soils as follows "Moderately well -drained soils underlain by consolidated glacial till (hardpan) at a depth of 24 to 40 inches. Alderwood soils formed in glacial deposits under conifers. They occupy upland areas at elevations between 100 and 800 feet. The annual precipitation is 35 to 60 inches, mostly rainfall between October and May. The frost - free season is 150 to 200 days." (King Conservation District) A typical Alderwood soil profile from 0 to 27 inches is a dark brown gravelly sandy loam. From 27 to 60 inches, the soil takes a grayish brown weakly to strongly consolidated glacial till characteristic (hardpan). Soil permeability is rapid in surface layer and subsoil above hardpan material and very slow in the hardpan. The depth to the seasonal high water table is 2 to 3 feet and the water -holding capacity is seasonally low (summer) to seasonally high (winter) (King Conservation District). Observations made on the landscape scale and during soil sampling were generally consistent with the descriptions provided in the Soil Survey of King County Area and by the King Conservation District. C. Climate and Growing Season 1. Climate Climatic information provided by the Soil Survey of King County Area on pages 88-89 and in Table 10 illustrates that the climate influencing the site is greatly tempered by weather systems that originate on the Pacific Ocean (Gale, Pringle, and Snyder;1973). Fairly warm, dry summers and cool, moist winters are the prevailing conditions. A pronounced dry season occurs during the late spring and summer months, with less than 10 days of cloudy or overcast weather and very little precipitation falling in July and August. Rains are frequent during the rest of the year, especially in late fall and winter. Average precipitation is 37 inches per year in Seattle measured at the Seattle -Tacoma International Airport. Snow is rare and typically melts quickly when it does occur. Marine air masses regulate the area's moderate temperatures. Average winter temperatures in the area average around 35' to 457, and summer temperatures typically average 60' to 707 (Gale, Pringle, and Snyder;1973). The combination of cool moist periods punctuated by distinct summer droughts is one of the chief determinants of the hydrology of the site (Gale, Pringle, and Snyder;1973). 2. Growing Season The USDA Natural Resources Conservation Service currently defines the growing season as the portion of the year when soil temperatures at 19.7 inches below the soil surface are higher than biological zero (approximately 410 F). (USDA, NRCS,1996). Using information provided by the Soil Survey of King County Area (Table 10) for Seattle -Tacoma International Airport and consistent with U.S. Army Corps of Engineers guidance, the growing season can be approximated for five years in ten (50 percent of the time) using the 28' F Wetland Report 17 February 2006 BERGER/ABAM, A06112 Page 5 of 5 standard (Gale, Pringle, and Snyder;1973). Using these criteria, the growing season for the site occurs between 9 March and 17 November and is 253 days in length. D. Land -Use History Historically, the primary uses of this landscape have been timber production, berry production, row crops, pasture, and urban development. Low fertility and summer drought have been limiting factors to extensive farming of this area. Douglas -fir, western red cedar, western hemlock, red alder, and bigleaf maple are important tree species on all slope classes. Black cottonwood can also be found in this area (Gale, Pringle, and Snyder;1973). Recently, pressures of urban development have begun to re -alter the areas landscape and previously platted lots are being divided into a greater number of smaller lots. This redistribution of land rights and ownership has led to additional removal of forested hill tops and has increased stormwater runoff and erosion and has impacted the adjacent wetland systems. The subject site, as illustrated in Figure 3, consists of one home towards the top of the hill, and a large fenced horse area that appears to have been graded to provide a flat area for the purpose of pasture. Due to this ongoing land use, significant site erosion is apparent and this is impacting the adjacent subject wetland through sheet flow. Ill. Methodologies A. Rationale for the Determination of the Subject Site Wetland Bonndarles The field work was completed during a two-day period from 6 February 2006 to 7 February 2006 pursuant to Renton Municipal Code (RMC) (4)(3)(050)(M)(4a) using the procedures provided in the Washington State Wetlands Identification and Delineation Manual, as developed by the Washington State Department of Ecology, March 1997, Ecology Publication 96-94. Although the data collection and field study associated with this delineation were not made during the growing season and hydrologic observations were made following one of the areas wettest months on record, all work was done in accordance with WAC 173-22-080 that states: "It is the purpose of a delineation manual to provide information and methods that will allow a delineator to make an accurate wetland delineation at any time of the year." For this reason, field study and data collection was completed as required by the Washington State Wetlands Identification and Delineation Manual, however, experience and field judgment were also considered in delineating the wetland boundary on the site. Wetland Report 17 February 2006 BERGER/ABAM, A06112 Page 6of6 B. Office Methods Consistent with the scope of this project and procedures detailed in the Washington State Wetlands Identification and Delineation Manual, preliminary information about the site and the immediate vicinity prior to completing the field work. General information sources included the Soil Survey of King County Area, National Wetlands Inventory Maps, both King County and City of Renton websites, and Geographic Information Systems (GIS) data, as well as public records available at the City of Renton. In addition, aerial photographs taken in 2002 and topographic data were reviewed and are depicted in Figure 3. Based on this information, it was possible to make preliminary decisions about the wetland system based on guidance from the Washington State Wetlands Identification and Delineation Manual, Part IV, Section B that helped to scope the completed field work, including the fact that the wetland has been previously identified and accepted as a Type II wetland by the City of Renton for adjacent development activities. C. Field Delineation The Washington State Wetlands Identification and Delineation Manual governs that an area is not considered a regulated wetland if indicators/evidence of any one of three defined parameters, including hydrology, soil, and vegetation are not observed under normal environmental conditions to make a positive wetland determination. Methods of evaluation for each of these parameters are as follows. 1. Hydrology Evaluation Consistent with the Washington State Wetlands and Delineation Manual, the presence of wetland hydrology can be determined by evaluating a variety of direct and indirect indicators. In addition to hydrologic data/records pertaining directly to the study area, hydrologic indicators are used to infer wetland hydrology. Field indicators of wetland hydrology listed in the Washington State Wetlands and Delineation Manual include, but are not limited to, visual observation of inundation and/or soil saturation, oxidized channels (rhizospheres) associated with living roots and rhizomes, water marks on vegetation or fixed objects, drift lines, water -born sediment deposits, water -stained leaves, surface scoured areas, wetland drainage patterns, morphological plant adaptations, and hydric soil characteristics. According to the Washington State Wetlands and Delineation Manual, areas that are inundated and/or saturated to the surface for a consecutive number of days between 5 and 12.5 percent of the growing season may or may not be wetlands. As outlined under "Climate and Growing Season for Wetland Delineations" above, the growing season defined by the Soil Survey of King County Area for Seattle -Tacoma International Airport, is 253 days in length. Assuming the lower percentage, 5 percent of 253 days is 13 consecutive days. Therefore, consistent with the Washington State Wetlands and Delineation Wetland Report 17 February 2006 BERGER/ABAM, A06112 Page 8 of 8 Manual, an area must be inundated or saturated to the surface for 13 consecutive days during the growing season, which extends from 9 March to 17 November. 2. Soil Evaluation The presence of hydric soils can be determined based on the criteria outlined in the Washington State Wetlands and Delineation Manual. The definition of a hydric soil is "... a soil that formed under conditions of saturation, flooding, or pending long enough during the growing season to develop anaerobic conditions in the upper part" (USDA, NRCS,1996). The definition of a hydric soil is satisfied by the fulfillment of at least one of four technical criteria, including the followingAs AAs : (1) All Histels except Folistels and Histosols except Folists; or (2) Soils in Aquic suborders, great groups, or subgroups, Albolls suborder, Historthels great group, Histoturbels great group, Par -hie subgroups, or Cumulic subgroups that are: (a) Somewhat poorly drained with a water table equal to 0.0 foot from the surface during the growing season, or (b) Poorly drained or very poorly drained and have either: Water table equal to 0.0 foot during the growing season if textures are coarse sand, sand, or fine sand in all layers within 20 inches; or for other soils (ii) Water table at less than or equal to 0.5 foot from the surface during the growing season if permeability is equal to or greater than 6.0 inches/hour in all layers within 20 inches; or (iii) A water table at less than or equal to 1.0 foot from the surface during the growing season if permeability is less than 6.0 inches/hour in any layer within 20 inches; or (3) Soils that are frequently ponded for Iong or very long durations during the growing season; or (4) Soils that are frequently flooded for long or very long durations during the growing season. Fulfillment of the technical criteria for soil can be inferred by using a combination of published soils information and field indicators. The indicators available for determining whether a soil satisfies the basic definition and the technical criteria for hydric soils include, but are not limited to the following: the soil is a histosol, a histic epipedon is present, hydrogen sulfide odor is present, the soil is gleyed, the soil has a depleted matrix, the soil has a low chroma matrix with redoximorphic features (e.g., mottles), iron and/or manganese concretions are present, the soil occurs in an aquic or peraquic soil moisture regime, and the soil appears on the hydric soils list. Wetland Report 17 February 2006 BERGER/ABAM, A06112 Page 9of9 Image No. 2: Sampling for Hydric Solis 3. Vegetation Evaluation For an accurate wetland determination to be made, the presence of hydrophytic vegetation must also be identified consistent with the Washington State Wetlands and Delineation Manual. Species identifications and taxonomic nomenclature follow that were found in A Field Guide to the Common Wetland Plants of Western Washington and North-Western Oregon (Cooke 1997). Dominant species in each of the three strata (tree, sapling/shrub, and herb) were identified. Dominant species are those species in each stratum that, when ranked in descending order of abundance and cumulatively totaled, immediately exceed 50 percent cover of the total dominance measure for that stratum, plus any species that comprises at least 20 percent cover. Each species' indicator status was assigned using the National List of Plant Species that Occur in Wetlands: Northwest - Region IX (Reed 1988). A species indicator status refers to the relative Frequency with which the species occurs in jurisdictional wetlands as outlined in Table No 1. Wetland Report 17 February 20Q6 BERGER/ABAM, A06112 Page 10 of 10 Table No. L, USFWS Plant Indicator Status Categories as modified by the National List of Plant Species that Occur In Wetlands: Northwest - Region IX Indicator Status Definition Obligate Wetland (OBL) Occur almost always (estimated probability >99%) under natural conditions in wetlands. Facultative Wetland (FACW) Usually occur in wetlands (estimated probability 67%-99%), but occasionally found in non -wetlands. Facultative (FAC) Equally likely to occur in wetlands or non -wetlands (estimated probability 34%-66%). Facultative Upland (FACU) Usually occur in non -wetlands, but occasionally found in wetlands (1%-33%). Obligate Upland (UPL) Plants that rarely occur (estimated probability <1%) in wetlands, but occur almost always in non -wetlands under natural conditions. No Indicator Status (NI) Insufficient information exists to assign an indicator status. Not Listed (NL) Not on the National List in any region. According to the Washington State Wetlands and Delineation Manual, an area meets the hydrophytic vegetation criteria when, under normal circumstances, more than 50 percent of the dominant species from each stratum are obligate wetland (OBL), facultative wetland (FACW), and/or facultative (FAC) species. For the purposes of the Washington State Wetlands and Delineation Manual protocol, a plus (+) or a minus (-) sign is often included in the designation to specify a higher or lower level of the indicator status for the three facultative categories, and a FAC- indicator status is not considered to be an indicator of hydrophytic vegetation (i.e., it is treated in the same way as a facultative upland [FACU], upland [UPL], and a not -listed [NL] species). IV. Results One palustrine forested, scrub -shrub wetland was identified on the site. This wetland is part of a larger system and is connected to other similar wetlands by Honey Creek. While the system remains isolated by manmade disturbances, it remains connected hydrologically through the watercourse found in the center of the area of study. Because of this connectivity, this wetland is a valuable resource with functional potential and value. The boundary of the wetland was delineated on the site along forested and scrub -shrub communities. Seven data points as illustrated in Figure 4 were established along the wetland boundary to establish a baseline of soil and hydrologic conditions and to sample plant communities. Data sheets were completed for each of these data points, and the Wetland Report BERGERIABAM, A06112 17 February 2006 Page 11 of 11 points were flagged and labeled to be surveyed. Copies of completed data sheets are included in Appendix I. Data from the collection points was analyzed and a wetland determination was made for each point. Based on this data, a break in topography, plant communities, and hydrologic indicators was located and followed with occasional sampling to ensure consistency with the baseline data collected. This line was determined to be the wetland edge and was flagged and labeled for survey. The following is a description of the findings of the field study. A. Data Points 1. Data Point UL-1(Attached Data Sheet UL-1) Location: This data point is located in the northwest end of the property at the base of a large hill and on the upland edge adjacent to the Honey Creek wetland. Hydrology: No indicators of wetlands hydrology were present at this data point. Soils: The soil survey completed (see attached data sheet UL-1) indicated the soil immediately below the A horizon or at 10 inches was not consistent with the requirements of wetlands soils as outlined in the Washington State Wetlands and Delineation Manual (matrix color of 1, or 2 with redoxomorphic features present, gleyed colors, or presence of organic soils). This data point did not exhibit characteristics of a wetland soil. Vegetation: The vegetation surveyed within and around this data point consisted of red alder (Alnus rubra), Himalayan blackberry (Rubus discolor), and creeping buttercup (Ranunculus repens). When totaled based on dominance of the stratum, the plant communities did not meet the standards of wetland vegetation outlined above and as established by the Washington State Wetlands and Delineation Manual. The percentage of dominant species with a rating FAC or wetter within this wetland was found to be 48percent. Determination: Because this data point lacked the presence of any of the parameters of a wetland, it was designated an upland data point. Wetland Report 17 February 2006 BERGER/ABAM, A06112 Page 12 of 12 s f U L-3 WI -4 Legend Source., king County GIS / 2002 USGS High Resolution Orthoinnage Subject Property Parcel Boundaries Tax Parcels Boundary Flays F i g u re 4- Data Point Locations gEmGEn1AOAy4 Upland Data Point Note: Data point I I I I I I I 1 1 ° :. " • Welland Data Pant locations approximated. 0 30 60 120 Feet 2. Data Point UL-2 (Attached Data Sheet UL-2) Location: This data point is located in the southeast end of the property near the fence line of the horse coral and on the upland edge adjacent to the Honey Creek wetland. Hydrology. No indicators of wetlands hydrology were present at this data point. Soils: The soil survey completed (see attached data sheet UL-2) indicated the soil immediately below the A horizon or at 10 inch was consistent with the requirements of wetland soils as outlined in the Washington State Wetlands and Delineation Manual (matrix color of 1, or 2 with redoxomorphic features present). This data point did display characteristics of a wetland soil, however, this may be due to historic site conditions as the site had no indication of required hydrology. Vegetation: The vegetation surveyed within and around this data point consisted of red alder (Alnus rubra), Himalayan blackberry (Rubus discolor), and creeping buttercup (Ranunculus repens). When totaled based on dominance of the stratum, the plant communities did meet the standards of wetland vegetation outlined above and as established by the Washington State Wetlands and Delineation Manual. The percentage of dominant species with a rating FAC or wetter within this wetland was found to be 50 percent. Determination: Because this data point Iacked the presence of all three of the parameters of a wetland, it was designated an upland data point. Further evaluation of this site and its position in the landscape verified this determination. 3. Data Point UL�3 (Attached Data Sheet UL-3) Location: This data point is located in the southeast end of the property near the fence line of the horse coral and on the upland edge adjacent to the Honey Creek wetland. Hydrology: This site had strong indicators of wetland hydrology, however, observations were not made during the growing season as is recommended by the Washington State Wetlands and Delineation Manual. This data point may require further evaluation during the growing season for a more accurate determination, however, the presence or absence of wetland qualifying conditions at this point do not significantly affect the wetland boundary. Soils: The soil survey completed (see attached data sheet UL-3) indicated the soil immediately below the A horizon or at 10 inches was not consistent with the requirements of wetlands soils as outlined in the Washington State Wetlands and Delineation Manual (matrix color of 1, or 2 with redoxomorphic Wetland Report 17 February 2006 BERGER/ABAM, A061I2 Page 14 of 14 features present, gleyed colors, or presence of organic soils). This data point did not exhibit characteristics of a wetland soil, however, the soils characteristics were close to those of a very gravelly wetland soil. Vegetation: The vegetation surveyed within and around this data point consisted of red alder (Alnus rubra), Himalayan blackberry (Rubus discolor), salmonberry (Rubus spectabilis), creeping buttercup (Ranunculus repens), and skunk cabbage (Lysichiton americanum). When totaled based on dominance of the stratum, the plant communities did meet the standards of wetland vegetation outlined above and as established by the Washington State Wetlands and Delineation Manual. The percentage of dominant species with a rating FAC or wetter within this wetland was found to be SO percent. Determination: The characteristics at this data point were very difficult to characterize due to the scheduling of field visits outside of the growing season. Because this data point lacked the presence of all three of the parameters of a wetland, it was designated an upland data point. 4. Data Point WL-1(Attached Data Sheet WL-1) Location: This data point is located in the northwest end of the property at the base of a large hill on the wetland edge within the Honey Creek wetland. Hydrology: Strong indicators of wetlands hydrology were present at this data point. Soils: The soil survey completed (see attached data sheet WL-1) indicated the soil immediately below the A horizon or at 10 inches was consistent with the requirements of wetlands soils as outlined in the Washington State Wetlands and Delineation Manual (presence of organic soils). This data had strong characteristics of a wetland soil. Vegetation: The vegetation surveyed within and around this data point consisted of red alder (Alnus rubra), red osier dogwood (Cornus sericea), salmonberry (Rubus spectabilis), Douglas spirea (Spirea dougliasi), creeping buttercup (Ranunculus repens), Swordfern (Athyrium filix-femina), and skunk cabbage (Lysichiton americanum). When totaled based on dominance of the stratum, the plant communities met the standards of wetland vegetation outlined above and as established by the Washington State Wetlands and Delineation Manual. The percentage of dominant species with a rating FAC or wetter surrounding this wetland data point was found to be 100 percent. Determination: This data point demonstrated strong indicators of the parameters of a wetland and it was designated a wetland data point. Wetland Report 17 February 2006 BERGER/ABAM, A06I12 Page 15 of 15 5. Data Point WL-2 (Attached Data Sheet WL-2) Location: This data point is located in the northwest end of the property at the base of a large hill on the wetland edge within the Honey Creek wetland. Hydrology. Strong indicators of wetlands hydrology were present at this data point. Soils: The soil survey completed (see attached data sheet WL-2) indicated the soil immediately below the A horizon or at 10 inches was consistent with the requirements of wetlands soils as outlined in the Washington State Wetlands and Delineation Manual (matrix color of 1, or 2 with redoxomorphic features present). This data point did display characteristics of a wetland soil. Vegetation: The vegetation surveyed within and around this data point consisted of red alder (Alnus rubra), red osier dogwood (Cornus sericea), salmonberry (Rubus spectabilis), Himalayan blackberry (Rubus discolor), creeping buttercup (Ranunculus repens), ladyfern (Athyrium filix-femina), and English Ivy (Hedera helix). When totaled based on dominance of the stratum, the plant communities did meet the standards of wetland vegetation outlined above and as established by the Washington State Wetlands and Delineation Manual. The percentage of dominant species with a rating FAC or wetter within this wetland was found to be 100 percent. Determination: This data point demonstrated strong indicators of the parameters of a wetland and was designated a wetland data point. S. Data Point WL-3 (Attached Data Sheet WL-3) Location: This data point is located in the farthest northwest end of the property adjacent to NE 10th Street on the wetland edge of Honey Creek wetland. Hydrology: Strong indicators of wetlands hydrology were present at this data point. Soils: The soil survey completed (see attached data sheet WL-2) indicated the soil immediately below the A horizon or at 10 inches was consistent with the requirements of wetlands soils as outlined in the Washington State Wetlands and Delineation Manual matrix color of 1, or 2 with redoxomorphic features present). This data point did display characteristics of a wetland soil. Vegetation: The vegetation surveyed within and around this data point consisted red alder (Alnus rubra), western red cedar (Thuja plicata), salmonberry (Rubus spectabilis), Douglas spires (Spirea douglassi), Himalayan blackberry (Rubus discolor), and Ladyfern (Athyrium filix-femina). When totaled based on dominance of the stratum, the plant communities did meet the standards of wetland vegetation outlined above and as established by the Wetland Report 17 February 2006 BERGER/ABAM, A06112 Page 16 of 16 Washington State Wetlands and Delineation Manual. The percentage of dominant species with a rating FAC or wetter within this wetland was found to be 100 percent. Determination: This data point demonstrated strong indicators of the parameters of a wetland and was designated a wetland data point. 7. Data Point WIA (Attached Data Sheet WL-4) Location: This data point is Iocated in the southeast end of the property near the fence line of the horse coral and about 5 feet from the meandering stream channel within the Honey Creek wetland. Hydrology: Strong indicators of wetlands hydrology were present at this data point. Sous: The soil survey completed (see attached data sheet WL-4) indicated the soil immediately below the A horizon or at 10 inches was consistent with the requirements of wetlands soils as outlined in the Washington State Wetlands and Delineation Manual (presence of organic soils). This data point exhibits strong characteristics of a wetland soil. Vegetation: The vegetation surveyed within and around this data point consisted of red alder (Alnus rubra), salmonberry (Rubus spectabilis), ladyfern (Athyrium filix-femina), and skunk cabbage (Lysichiton americanum). When totaled based on dominance of the stratum, the plant communities did meet the standards of wetland vegetation outlined above and as established by the Washington State Wetlands and Delineation Manual. The percentage of dominant species with a rating FAC or wetter within this wetland was found to be 100 percent. Determination: This data point demonstrated strong indicators of the parameters of a wetland and was designated a wetland data point. B. Boundary Flags The boundary of the wetland was delineated on the site as the field work of sampling and observation was being completed. Labeled flags were used to identify points on the wetland boundary. The Professional Land Surveyor will be able to survey these points and connect them to be used in conjunction with this report as part of the required documentation for land use actions with the City of Renton. A total of 19 labeled flags were placed; 8 were lettered A through H; and 11 were numbered 1 though 11. The numbered flags start on the northwest end of the property bearing southeast, and the lettered flags start on the southeast end of the property bearing northwest. The two lines meet in the middle and form a single line that, based on the procedures and requirements outlined above, has been determined to be the wetland boundary. Wetland Report 17 February 2006 BERGERIABAK A06112 Page 17 of 17 V. References Bigley, Richard. Hull, Sabra. 2000. Recognizing Wetlands. Washington State Department of Natural Resources. Olympia, WA. Brinson, MM.1993. A Hydrogeomorphic Classification for Wetlands. Wetlands Research Program. Technical Report WRP-DE-4. US Army Corps of Engineers, Waterways Experiment Station, August 1993 — Final Report. 79 pp. plus appendices. Cooke, Sarah.1997. A Field Guide to the Common Wetlands Plants of Western Washington & Northwestern Oregon. Seattle Audubon Society, Seattle, WA. Cowardin, LM, Carter V, Golet TC, and ET LaRoe. 1979. Classification of Wetlands and Deepwater Habitats of the United States. USDI Fish and Wildlife Service, FWS/OBS-78/31. Gale, Pringle, and Snyder.1973. Soil Survey of King County Area, Washington. United States Department of Agriculture, Soil Conservation Service. King Conservation District. 2000. King County Soil Descriptions. (hU://www.kin cg d.org(pub soil.htm) Kollmorgen Corporation. 1994. Munsell soil color charts. Kollmorgen Corporation, Baltimore, MD. Reed, P.B. Jr. 1988. National list of plant species that occur in wetlands: Washington. Biological Report NERC-88/18.47 for National Wetlands Inventory, Washington, D.C. Reed, P.B. Jr.1993. Northwest supplement (Region 9) species with a change in indicator status or added to the Northwest 1988 list, wetland plants of the state of Washington 1988. U.S. Department of Interior Fish and Wildlife Service WELUT 88 (26.9), Washington, D.C. U.S. Department of Agriculture, Natural Resource Conservation Service in cooperation with USEPA, USFWS, USAC, and North Carolina State University. Version 2.0, June,1996. "Field Indicators of Hydric Soils in the United States." Washington State Department of Ecology. 1997. "Washington State Wetlands Identification and Delineation Manual." Ecology Publications #96-94. Wetland Report 17 February 2006 BERGER/ABAM, A06112 Page 18 of 18 Appendix I - Field Study Data Sheets DATA FORM 1 ROUTINE WETLAND DETERMINATION BFRGFR/ARAM E k 6 l III E A S I M G. (1997 Washington State Wetlands Delineation Manual) r. Project/Site: Honey Creek Wetland Date: 02/06/06 Client: Daniel Bretzke County: King Investigator: David Pyle State: WA Recent Weather: Rain/Outside of growing season. Plant Community Forested Do Normal Circumstances exist on the site? Yes ® No ❑ Transect ID: Is the site significantly disturbed? Yes ❑ No ® Plot ID: UL-1 Is the area a potential Problem Area? Yes ❑ No ® Plot Location See Figure 4 Explanation: This data point is located towards the northwest end of the property on the adjacent upland bank of the Honey Creek wetland. Due to project timelines and at the request of the client, all field observations and data collection was done in the beginning of February, outside of the growing season and following one of the areas wettest months on record. Because of the difficulty in identifying wetland parameters at this time of year, extra attention was given to secondary indicators. VEGETATION Dominant Species Tree Stratum Total Cover: 80% Indicator % Cover 1. Red Alder FAC 1 80 % 2. 3. 4. Sapling/Shrub Stratum Total Cover: 90% Indicator 1. Himalayan Blackberry FACU 2. 3. 4. 5, % Cover 90% Dominant Species Herb Stratum Total Cover: 95% 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Percent of Dominant Species that are OBL, FACW, FAC (not FAC -} 47% Other Notable Species: Criteria Met? Yes ❑ No Indicator % Cover FACW I 10% Remarks: Plants are majority FAC or FACU. Other plants were present but could not be identified due to the lack of foliage, although none of these plants made up more than 10% of the cover of any class. BERGER/ABAM ENGINEERS, INC. 1of 2 SOILS Map Unit Name Drainage Class: Moderatley well drained (Series and Phase) _Alderwood series Field Observations Confirm Mapped Type? Yes ® No ❑ Taxonomy (Subgroup): _AgB 1 AgC On Hydric Soil List? Yes ❑ No Profile Description: Depth (inches) Horizon Matrix Color (Munsell Mottle Colors Mottle Abundance/ Texture, Concretions, Moist) (Munsell Moist) Size/Contrast Structure, etc. 1 "- 0" 0 NIA NIA NIA Duff layer 0" -10" A 10 YR 413 NIA NIA Sandy Clay Loam 10" - 24" B 10YR 312 NIA NIA I Sandy Clay Loam Hydric Soil Indicators: ❑ Histosol ❑ Concretions/Nodules (wlin 3"; > 2 mm) ❑ Histic Epipedon ❑ High Organic contents in Surface Layer in Sandy Soils ❑ Sulfidic Odor ❑ Organic Streaking in Sandy Soils ❑ Aquic Moisture Regime ❑ Listed on Local Hydric Soils List ❑ Reducing Conditions ❑ Listed on National Hydric Soils List ❑ Gleyed or Law-Chroma Colors ❑ Other (Explain in Remarks) Redox. Features (w/in 10" Criteria Met? Yes L No Remarks: This soil pit contained some pieces of charcoal that indicate past clearing at this location. This pit is also located at the foot of a large hill containing a pasture and resdidential development that may have casued accumulation of eroded sediment over time. IRWrjR]Z101S0Ir]I ® Recorded Data (Describe in Remarks): ❑ Stream, Lake, or Tide Gauge ® Aerial Photographs ❑ Other ❑ No Recorded Data Available Comment: No standing water observed in aerial photo. Field Observations: Depth of Surface Water: Depth to Free Water in Pit: Depth to Saturated Soil: NA (in NA (in No saturation evident (in. Wetland Hydrology Indicators: Primary Indicators: ❑ Inundated ❑ Saturated in Upper 12 Inches ❑ Water Marks ❑ Drift Lines ® Sediment Deposits ❑ Drainage Patterns in Wetlands Secondary Indicators (2 or more required) ❑ Oxidized Root Channels in Upper 12 Inches ❑ Water -Stained Leaves ❑ Local soil Survey Data ❑ FAC-Neutral Test ❑ Other (Explain in Remarks) Criteria Met? Yes H No 21 Remarks Water was not found in the pit and was not observed on the ground surface in the immediate area of the pit. Sediment deposits were identified around the pit but may be due to sheetflow from the uphill pasture and residence where there is little groundcover and a bad erosion problem. WETLAND DETERMINATION Hydrophytic Vegetation Present? Yes ❑ No Wetland Hydrology Present? Yes ❑ No Hydric Soils Present? Yes ❑ No ® I Is this Sampling Paint Within a Wetland? Yes ❑ No ED Remarks This soil pit is being considered as Upland sample #1 (UL-1). This sample point did not exhibit characterisitcs of a wetland. 11 BERGERIABAM ENGINEERS, INC. 2of 2 DATA FORM 1 " ROUTINE WETLAND DETERMINATION BFRGFR/ABAM (1997 Washington State Wetlands Delineation Manual) ` w,s x E ` a e C. Project/Site: Honey Creek Wetland Date: 02/07/06 Client: Daniel Bretzke County: King Investigator: David Pyle State: WA Recent Weather: Rain/Outside of growing season. Plant Community Forested Do Normal Circumstances exist on the site? Yes ® No ❑ Transect ID: is the site significantly disturbed? Yes ❑ No ® Plot ID: UL-2 Is the area a potential Problem Area? Yes ❑ No ® Plot Location See Figure 4 Explanation: This data point is located towards the southeast end of the property on the adjacent upland bank of the Honey Creek wetland and about 15' from the horse corral fenceline and 20' from the flowthrough stream channel in Honey Creek wetland. Due to project timelines and at the request of the client, all field observations and data collection was done in the beginning of February, outside of the growing season and following one of the areas wettest months on record. Because of the difficulty in identifying wetland parameters at this time of year, extra attention was given to secondary indicators. VEGETATION Dominant Species Tree Stratum Total Cover: 60% Indicator % Cover 1. Red Alder FAC 60% 1. 2. 2. 3, 3. 4. 4. Sapling/Shrub Stratum 5. Total Cover: 60% 6. Indicator % Cover 7. 1. Himalayan Blackberry FACU 60% 8. 2, 9. 3. 10. 4. 5. Dominant Species Herb Stratum Total Cover: 95% Percent of Dominant Species that are OBL, FACW, FAC {not FAC -} Other Notable Species: Criteria Met? Yes ® No ❑ ina Bu 50% Indicator % Cover FACW I 10% Remarks: Plants are majority FAC or FACU. The criteria was met, but this was due to the strong presence of Red alder, which is FAC. Other plants were present but could not be identified due to the lack of foliage, although none of these plants made up more than 10% of the cover of any class. BERGER/ABAM ENGINEERS, INC. 1of 2 SOILS Map Unit Name Drainage Class: Moderatlev well drained (Series and Phase) _Alderwood series Field Observations Confirm Mapped Type? Yes ® No ❑ Taxonomy (Subgroup): _AgB / AgC On Hydric Soil List? Yes ❑ No Profile Description: Depth (inches) Horizon Matrix Color (Munsell Mottle Colors Mottle Abundance/ Texture, Concretions, Moist) (Munsell Moist) Size/Contrast Structure, etc. 1 "- 0" O NIA NIA NIA Duff layer 0" - 6" A 7.5 YR 313 NIA NIA Sandy Loam 6" -12" A 10YR 3I2 7.5 YR 518 *See note Loamy Sand 12" - 24" B 10 YR 412 7.5 YR 518 *See note Sandy Loam Hydric Soil Indicators: ❑ Histosol ❑ Concretions/Nodules (wlin 3"; > 2 mm) ❑ Histic Epipedon ❑ High Organic contents in Surface Layer in Sandy Soils ❑ Sulfidic Odor ❑ Organic Streaking in Sandy Soils ❑ Aquic Moisture Regime ❑ Listed on Local Hydric Soils List ❑ Reducing Conditions ❑ Listed on National Hydric Soils List ® Gleyed or Low-Chroma Colors ❑ Other (Explain in Remarks) Redox. Features (w/in 10" Criteria Met? Yes 0 No Remarks: This pit is also located at the foot of a small hill below a horse corral and that may have casued accumulation of eroded sediment over time. The soils in this pit meet the criteria of a hydric soil due to the low chroma and presencer of massinglredox features in the profile < 10". *These layers contain massing evident around rocks/pebbles found in the soil profile that may be due to deposition of this material at one time during a major flood event or due to a migrating stream channel. HYDROLOGY ® Recorded Data (Describe in Remarks) ❑ Stream, Lake, or Tide Gauge ® Aerial Photographs ❑ Other ❑ No Recorded Data Available Comment: No standing water observed in aerial Field Observations: Depth of Surface Water: Depth to Free Water in Pit: Depth to Saturated Soil: Criteria Met? Yes NA (in. NA fin. No saturation evident {in. No Wetland Hydrology Indicators: Primary Indicators: ❑ Inundated ❑ Saturated in Upper 12 Inches ❑ Water Marks ❑ Drift Lines ❑ Sediment Deposits ❑ Drainage Patterns in Wetlands Secondary Indicators (2 or more required) ❑ Oxidized Root Channels in Upper 12 Inches ❑ Water -Stained Leaves ❑ Local soil Survey Data ❑ FAC-Neutral Test ❑ Other (Explain in Remarks) Remarks Water was not found in the pit and was not observed on the ground surface in the immediate area of the pit. Water stained leaves were identified around the pit but may be due to short periods of inundation during major storm events. WETLAND DETERMINATION LFHydrophytic Vegetation Present? Yes ® Noand Hydrology Present? Yes ® No ❑ic Soils Present? Yes ❑ No ® Is this Sam lin Point Within a Wetland? Yes ❑ Noarks This soil pit is being considered as Upland sample #2 (UL-2). Although this sample pit did meet the irements for soils and vegetation, the indicators were not strong, and the point did not have any indication of and hydrology even though the field sampling was done immediately foilowingf one of the areas wettest months on rd. This sample point did not exhibit all of the characterisitcs of a wetland. BERGER/ABAM ENGINEERS, INC. 2of 2 DATA FORM 1 ROUTINE WETLAND DETERMINATION BERGFR/ARAM (1997 Washington State Wetlands Delineation Manual) F o H E F 5 s Project/Site: Honey Creek Wetland Date: 02/07/06 Client: Daniel Bretzke County: King Investigator: David Pyle State: WA Recent Weather: Rain/Outside of growing season. Plant Community Forested Do Normal Circumstances exist on the site? Yes ® No ❑ Transact ID: Is the site significantly disturbed? Yes ❑ No ® Plot ID: UL-3 Is the area a potential Problem Area? Yes ❑ No ® Plot Location See Figure 4 Explanation: This data point is located towards the southeast end of the property on the adjacent upland bank of the Honey Creek wetland and about 20' from the horse corral fencline and 1 O' from the flovAhrough stream channel In Honey Creek wetland. This data point was placed as an additional point to verify the presence of a finger off of the wetland, howevor due the seasonality of the field work, It was difficult to make an accurate determination. Due to project timelines and at the request of the client, all field observations and data collection was done in the beginning of February, outside of the growing season and following one of the areas wettest months on record. Because of the difficulty in identifying wetland parameters at this time of ear, extra attention was given to secondary indicators. VEGETATION Dominant Species Tree Stratum Total Cover: 60% Dominant Species Herb Stratum Total Cover: 95% Indicator % Cover 1. Red Alder FAC 70 % 1. 2. 2, 3, 3. 4. 4. Sapling/Shrub Stratum 5. Total Cover: 60% 6. Indicator % Cover 7, 1. Himalayan Blackberry FACU 30% 8. 2. Salmonber FAC+ 20% 9. 3. 10. 4. 5. Indicator % Cover Creeping Buttercup FACW 30% Skunk Cabbage OBL 1 10% Percent of Dominant Species that are OBL, FACW, FAC (not FAC -) Other Notable Species: Criteria Met? Yes ® No ❑ Remarks: Plants are majority FAC or FACW. The criteria was met, but this was due to the strong presence of Red alder, which is FAC. Other plants were present but could not be identified due to the lack of foliage, although none of these plants made up more than 10% of the cover of any class. BERGERIABAM ENGINEERS, INC. 1of 2 SOILS Map Unit Name Drainage Class: Moderatlev well drained (Series and Phase) _Alderwood series Field Observations Confirm Mapped Type? Yes ® No El Taxonomy (Subgroup): _AgB 1 AgC On Hydric Soil List? Yes ❑ No Profile Description: Depth (inches) Horizon Matrix Color (Munsell Mottle Colors Mottle Abundance/ Texture, Concretions, Moist) (Munsell Moist) Size/Contrast Structure, etc. 1 "- 0" 0 NIA NIA NIA Organic Laver 0" - 6" A 10 YR 4/3 NIA NIA Sandy Loam 6" -18" A 7.5 YR 4/2 NIA NIA Loamy Sand Hydric Soil Indicators: ❑ Histosol ❑ Concretions/Nodules (w/in 3"; > 2 mm) ❑ Histic Epipedon ❑ High Organic contents in Surface Layer in Sandy Soils ❑ Sulfidic Odor ❑ Organic Streaking in Sandy Soils ❑ Aquic Moisture Regime ❑ Listed on Local Hydric Soils List ❑ Reducing Conditions ❑ Listed on National Hydric Soils List ❑ Gleyed or Low-Chroma Colors ❑ Other (Explain in Remarks) ❑ Redox. Features wlin 10" Criteria Met? Yes No Remarks: This pit is also located at the foot of a small hill below a horse corral and that may have casued accumulation of eroded sediment over time. This pit contained rocks/pebbles found in the soil profile that may be due to deposition of this material at one time during a major flood event or due to a migrating stream channel. The reddish color of the soil gravel gave off false indicators of redoximor hic features, and after further evaluation was not determined to be a wetland soil. HYDROLOGY ® Recorded Data (Describe in Remarks): ❑ Stream, Lake, or Tide Gauge ® Aerial Photographs ❑ Other ❑ No Recorded Data Available Comment: No standina water observed in aerial Field Observations: Depth of Surface Water: Depth to Free Water in Pit: Depth to Saturated Soil: Criteria Met? Yes M No Wetland Hydrology Indicators: Primary Indicators: ❑ Inundated ® Saturated in Upper 12 Inches ® Water Marks ❑ Drift Lines ® Sediment Deposits ® Drainage Patterns in Wetlands Secondary Indicators (2 or more required) 0 in. ❑ Oxidized Root Channels in Upper 12 Inches ® Water -Stained Leaves i2il ❑ Local soil Survey Data ❑ FAC-Neutral Test 0 (in.) ❑ Other (Explain in Remarks) Remarks Water was found in the pit and was observed on the ground surface in the immediate area of the pit. Water stained leaves and other secondary indicators were identified around the pit but may be due to short periods of inundation during major storm events. 11 WETLAND DETERMINATION Hydrophytic Vegetation Present? Yes No ❑ Wetland Hydrology Present? Yes ® No ❑ Hydric. Soils Present? Yes ❑ No ® I Is this Sampling Point Within a Wetland? Yes ❑ No Remarks This soil pit is being considered as Upland sample ##3 (UL-3). Although this sample pit did meet the requirements for hydrology, the soil and vegetation indicators were not strong. Thls point may be innundated because the field sampling was done immediately following one of the areas wettest months on record. This sample point did not exhibit all of the characterisitcs of a wetland, and further site evaluation at this point may be required during the growing season for a more accurate determination. BERGERIABAM ENGINEERS, INC. . 2of 2 DATA FORM 1 ROUTINE WETLAND DETERMINATION BERGER/ABAM ENGINEERS I N 6. (1997 Washington State Wetlands Delineation Manual) Project/Site: Honey Creek Wetland Date: 02/06/06 Client: Daniel Bretzke County: King _ Investigator: David Pyle State: WA Recent Weather: Rain/Outside of growing season. Plant Community Forested Do Normal Circumstances exist on the site? Yes ® No ❑ Transect ID: Is the site significantly disturbed? Yes ❑ No ® Plot ID: WL-1 Is the area a potential Problem Area? Yes ❑ No ® Plot Location See Figure 4 Explanation: This data point is located towards the northwest end of the property within the Honey Creek wetland. Due to project timelines and at the request of the client, all field observations and data collection was done in the beginning of February, outside of the growing season and following one of the areas wettest months on record. Because of the difficulty in identifying wetland parameters at this time of year, extra attention was given to secondary indicators. VFGFTATION Dominant Species Tree Stratum Total Cover: 80% Dominant Species Herb Stratum Total Cover: 25% Indicator % Cover 1. Red alder FAC 80% 1. 2. 2. 3. 3• 4. 4. Sa lin /Shrub Stratum Total Cover: 80% Indicator % Cover 1. Red osier dogwood FACW 50% 5. 6. 7. 8. 2. Salmonber FAC+ 20% 9. 3. Douglas sirea FACW 10% 10. 4. 5. Indicator % Cover Creeping buttercup FACW 10% Swordfern FACU 10% Skunk cabbage OBL 5% Percent of Dominant Species that are OBL, FACW, FAC (not FAC -} Other Notable Species: Criteria Met? Yes ® No ❑ 100% Remarks: Plants are majority FAC or FACW. Other plants were present but could not be identified due to the lack of foliage, although none of these plants made up more than 10% of the cover of any class. BERGERIABAM ENGINEERS, INC. 1of 2 LZ41IIM Map Unit Name (Series and Phase) _Alderwood series Drainage Class: Moderatlev well drained Field Observations Confirm Mapped Type? Yes ® No ❑ Taxonomy (Subgroup): _AgB I AgC On Hydric Soil List? Yes ❑ No Profile Description: Depth (inches) Horizon Matrix Color (Munsell Moist) Mottle Colors Mottle Abundance/ Texture, Concretions, (Munsell Moist) Size/Contrast Structure, etc. 2% 0" O NIA NIA NIA Duff/Detritus layer 0" - 24" O 10 YR 2/1 NIA N/A Or anic/Fibric Hydric Soil Indicators: ❑ Histosol ❑ Concretions/Nodules Win 3"; > 2 mm) ❑ Histic Epipedon ❑ High Organic contents in Surface Layer in Sandy Soils ® Sulfidic Odor ❑ Organic Streaking in Sandy Soils ® Aquic Moisture Regime ❑ Listed on Local Hydric Soils List ® Reducing Conditions ❑ Listed on National Hydric Soils List ® Gleyed or Low-Chroma Colors ® Other (Explain in Remarks) Redox. Features (w/in 10" Criteria Met? Yes El No Remarks: This soil pit consisted of an organic soil throughout the profile. Some sand was mixed in to the soil, and this may be due to the serious historic erosion problem on the uphill slope. HYDROLOGY ® Recorded Data (Describe in Remarks): Wetland Hydrology Indicators: ❑ Stream, Lake, or Tide Gauge Primary Indicators: ® Aerial Photographs ❑ Inundated ❑ Other ® Saturated in Upper 12 Inches ❑ No Recorded Data Available ® Water Marks Comment: No standing water observed in aerial Bhoto. ® ® Drift Lines Sediment Deposits Field Observations: ® Drainage Patterns in Wetlands Secondary Indicators (2 or more required) Depth of Surface Water: 0 in. ❑ Oxidized Root Channels in Upper 12 Inches ® Water -Stained Leaves Depth to Free Water in Pit: 1 in. ❑ Local soil Survey Data ❑ FAC-Neutral Test Depth to Saturated Soil: 0 in. ❑ Other (Explain in Remarks) Criteria Met? Yes M No Remarks This data point was saturated to the surface and emitted a strong sulfuric smell when the profile was extracted. No standing water was observed in the aerial photo howevor there is a strong canopy on site and the seasonality of the photo may not be a fair indicator of hydrology. WETLAND DETERMINATION Hydrophytic Vegetation Present? Yes ® No ❑ Wetland Hydrology Present? Yes ® No ❑ Hydric Soils Present? Yes ® No ❑ I Is this Sampling Point Within a Wetland? Yes ® No El Remarks This soil pit is being considered as Wetland sample #1 (WL-1). This sample point contains primary and 11 secondary characterisitcs of a wetland. BERGERIABAM ENGINEERS, INC. 2of 2 DATA FORM 1 ROUTINE WETLAND DETERMINATION BERGER/ABAM (1997 Washington State Wetlands Delineation Manual) E X 6 1 X E E R! Project/Site: Honey Creek Wetland Date: 02/06/06 Client: Daniel Bretzke County: Kin Investigator: David P e State: WA Recent Weather: Rain/Outside of growing season. Plant Community Forested Do Normal Circumstances exist on the site? Yes ® No ❑ Transect ID: Is the site significantly disturbed? Yes ❑ No ® Plot ID: WL-2 Is the area a potential Problem Area? Yes ❑ No ® Plot Location See Figure 4 Explanation: This data point is located towards the northwest end of the property within the Honey Creek wetland. Due to project timelines and at the request of the client, all field observations and data collection was done in the beginning of February, outside of the growing season and following one of the areas wettest months on record. Because of the difficulty in identifying wetland parameters at this time of year, extra attention was given to secondary indicators. VEGETATION Dominant Species Tree Stratum Total Cover: 80% Indicator 1. Red alder FAC % Cover 80 % Dominant Species Herb Stratum Total Cover: 30% 1. Creeping buttercup Indicator FACW % Cover 10% 2. 2. Swordfern FACU 10% 3. 3. English ivy Not listed 10% 4. 4. SaolinalShrub Stratum Total Cover: 85% Indicator 1. Red osier dogwood FACW % Cover 50% 5. 6. 7. 8. 2, Salmonber FAC{ 20% 9. 3. Himalayan blackberry FACU 15% 10. ,4. 5. Percent of Dominant Species that are OBL, FACW, FAC (not FAC -} 100% Other Notable Species: Criteria Met? Yes ® No ❑ Remarks: Plants are majority FAC or FACW. Other plants were present but could not be identified due to the lack of foliage, although none of these plants made up more than 10% of the cover of any class. BERGERIABAM ENGINEERS, INC. 1of2 U81I�-4 Map Unit Name Drainage Class: Moderatley well drained (Series and Phase) _Alderwood series Field Observations Confirm Mapped Type? Yes ® No ❑ Taxonomy (Subgroup): _AgB I AgC On Hydric Soil List? Yes ❑ No Profile Description: Depth (inches) Horizon Matrix Color (Munsell Mottle Colors Mottle Abundance/ Texture, Concretions, Moist) (Munsell Moist) Size/Contrast Structure, etc. 211- 0" O NA NIA NIA Duff/Detritus layer 0" - 4" A 7.5 YR 312 NIA NIA Sandy Clay Loam 4" - 12" A 10 YR 3/1 NIA N/A Sandy Clay Loam 12" - 18" B 7.5 YR 311 NIA N/A Loam Hydric Soil Indicators: ❑ Histosol ❑ Concretions/Nodules (Win 3"; > 2 mm) ❑ Histic Epipedon ❑ High Organic contents in Surface Layer in Sandy Soils ❑ Sulfrdic Odor ❑ Organic Streaking in Sandy Soils ® Aquic Moisture Regime ❑ Listed on Local Hydric Soils List ® Reducing Conditions ❑ Listed on National Hydric Soils List ® Gleyed or Low-Chroma Colors ® Other (Explain in Remarks) Redox. Features wlin 10" Criteria Met? Yes IR No ri Remarks: This soil pit contained a soil profile that was primarily of a low chroma color (< 1), although it had no evidence of redoxamorphic features. :14 r]-IQ 116Ie 1 ® Recorded Data (Describe in Remarks): Wetland Hydrology Indicators: ❑ Stream, Lake, or Tide Gauge Primary Indicators: ® Aerial Photographs ❑ Inundated ❑ Other ® Saturated in Upper 12 Inches ❑ No Recorded Data Available ® Water Marks Comment: No standin water observed in aerial photo. ® ® Drift Lines Sediment Deposits Field Observations: ® Drainage Patterns in Wetlands Secondary Indicators (2 or more required) Depth of Surface Water: 0 in. ❑ Oxidized Root Channels in Upper 12 Inches ® Water -Stained Leaves Depth to Free Water in Pit: 5 in. ❑ Local soil Survey Data ❑ FAC-Neutral Test Depth to Saturated Soil: 3 in. ❑ Other (Explain in Remarks) Criteria Met? Yes J�J No H Remarks This data point was saturated nearly to the surface and had obvious indicators of inundation during major storm events. WETLAND DETERMINATION Hydrophytic Vegetation Present? Yes No Wetland Hydrology Present? Yes ® No ❑ H dric Soils Present? Yes ® No ❑ Is this Sampling Point Within a Wetland? Yes ® No El Remarks This soil pit is being considered as Wetland sample #2 (WL-2). This sample point contains primary and secondary characterisitcs of a wetland. BERGER/ABAM ENGINEERS, INC. 2of 2 DATA FORM 1 ROUTINE WETLAND DETERMINATION BERGER/ABAM (1997 Washington State Wetlands Delineation Manual) Project/Site: Honey Creek Wetland Date: 02/06/06 Client: Daniel Bretzke County: King Investigator: David Pyle State: WA Recent Weather: Rain/Outside of growing season. Plant Community Forested Do Normal Circumstances exist on the site? Yes ® No ❑ Transect ID: Is the site significantly disturbed? Yes ❑ No ® Plot ID: WL-3 Is the area a potential Problem Area? Yes ❑ No ® Plot Location _See Figure 4 Explanation: This data point is located towards the farthest northwest end of the property within the Honey Creek wetland adjacent to NE 10th Street. Due to project timelines and at the request of the client, all field observations and data collection was done in the beginning of February, outside of the growing season and following one of the areas wettest months on record. Because of the difficulty in identifying wetland parameters at this time of year, extra attention was given to secondary indicators. VEGETATION Dominant Species Tree Stratum Total Cover: 50% Indicator % Cover 1. Red alder FAC 30% 2. Western red cedar FAC 20% 3. 4. Sapling/Shrub Stratum Total Cover: 50% Indicator % Cover 1. Salmonber FAC+ 20% 2. Douglas sirea FACW 20% 3. Himalayan bl ckberry FACU 10% 4. 5. Dominant Species Herb Stratum Total Cover: 10% 1. 2. 3. 4. 5, 6. 7. 8. 9. 10. Swordfern Percent of Dominant Species that are OBL, FACW, FAC (not FAC -) 100% Other Notable Species: Criteria Met? Yes ® No ❑ Indicator % Cover FACU I 10% 11 Remarks: Plants are majority FAC or FACW. Other plants were present but could not be identified due to the lack of foliage, although none of these plants made up more than 10% of the cover of any class. BERGERIABAM ENGINEERS, INC. 1of 2 SOILS Map Unit Name Drainage Class: Moderatlev well drained (Series and Phase) _Alderwood series Field Observations Confirm Mapped Type? Yes ® No ❑ Taxonomy (Subgroup): _AgB 1 AgC On Hydric Soil List? Yes ❑ No Profile Description: Depth (inches) Horizon Matrix Color (Munsell Mottle Colors Mottle Abundance/ Texture, Concretions, Moist) (Munsell Moist) Size/Contrast Structure, etc. 1 "- 0" 0 NIA NIA N/A Duff/Detritus layer 0" - 8" A 10 YR 2/2 NIA N/A Sandy Cla Loam 8" - 16" A 7.5 YR 3/2 2.5 YR 5/6 Few/Small Sandy Clay Loam Hydric Soil Indicators: ❑ Histosol ❑ Concretions/Nodules (w/in 3"; > 2 mm) ❑ Histic Epipedon ❑ High Organic contents in Surface Layer in Sandy Soils ❑ Sulfidic Odor ❑ Organic Streaking in Sandy Soils ® Aquic Moisture Regime ❑ Listed on Local Hydric Soils List ® Reducing Conditions ❑ Listed on National Hydric Soils List ® Gleyed or Low-Chroma Colors ® Other (Explain in Remarks) ® Redox. Features (w/in 10" Criteria Met? Yes JK Na Ll Remarks: This soil pit consisted of an organic soil throughout the profile. Some sand was mixed in to the soil, and this may be due to the serious historic erosion problem on the uphill slope. HYDROLOGY ® Recorded Data (Describe in Remarks): ❑ Stream, Lake, or Tide Gauge ® Aerial Photographs ❑ Other ❑ No Recorded Data Available Comment: No standing water observed in aerial Field Observations: Depth of Surface Water: Depth to Free Water in Pit: Depth to Saturated Soil: Criteria Met? Yes M No Wetland Hydrology Indicators: Primary Indicators: ❑ inundated ® Saturated in Upper 12 Inches ® Water Marks ® Drift Lines ❑ Sediment Deposits ❑ Drainage Patterns in Wetlands Secondary Indicators (2 or more required) Lin.Lln.L ❑ Oxidized Root Channels in Upper 12 Inches ® Water -Stained Leaves 5 in. ❑ Local soil Survey Data ❑ FAC-Neutral Test 4 in. ❑ Other (Explain in Remarks) Remarks This data point was saturated to the surface and emitted a strong sulfuric smell when the profile was extracted. No standing water was observed in the aerial photo howevor there is a strong canopy on site and the seasonality of the photo may not be a fair indicator of hydrology. 11 WETLAND DETERMINATION Hydrophytic Vegetation Present? Yes Q9 No " Wetland Hydrology Present? Yes ® No ❑ Hydric Soils Present? Yes ® No ❑ I Is this Sampling Point Within a Wetland? Yes ® No ❑ Remarks This soil pit is being considered as Wetland sample #3 (WL-3). This sample point contains primary and secondary characterisitcs of a wetland. BERGER/ABAM ENGINEERS, INC. 2of 2 DATA FORM 1 ROUTINE WETLAND DETERMINATION BERGER/ABAM (1997 Washington State Wetlands Delineation Manual) ` k a M E f S N C. Project/Site: Honey Creek Wetland Date: 02/07/06 Client: Daniel Bretzke County: King Investigator: David Pyle State: WA Recent Weather: Rain/Outside of growing season. Plant Community Forested Do Normal Circumstances exist on the site? Yes ® No ❑ Transect ID: Is the site significantly disturbed? Yes ❑ No ® Plot ID: WL-4 Is the area a potential Problem Area? Yes ❑ No ® Plot Location See Figure 4 Explanation: This data point is located towards the southeast end of the property within the Honey Creek wetland approximately 5 feet from the meandering stream channel. Due to project timelines and at the request of the client, all field observations and data collection was done in the beginning of February, outside of the growing season and following one of the areas wettest months on record. Because of the difficulty in identifying wetland parameters at this time of year, extra attention was given to secondary indicators. VEGETATION Dominant Species Tree Stratum Total Cover: 80% Indicator % Cover 1. Red alder FAC 80 % Dominant Species Herb Stratum Total Cover: 30% Indicator % Cover 1. Lady fern FAC 10% 2. 2. Skunk cabbage OBL 20% 3. 3. 4. 4. Sapling/Shrub Stratum Total Cover: 50% Indicator % Cover 1. Salmonber FAC+ 50% 5. 6. 7. 8. 2. 9. 3. 10, 4. 5. Percent of Dominant Species that are OBL, FACW, FAC (not FAC -) 100% Other Notable Species: Criteria Met? Yes ® No ❑ Remarks: Plants are majority FAC or OBL. Other plants were present but could not be identified due to the lack of foliage, although none of these plants made up more than 10% of the cover of any class. BERGERIABAM ENGINEERS, INC. iof 2 cnu c Map Unit Name (Series and Phase) _Alderwood series Drainage Class: Moderatley well drained Field Observations Confirm Mapped Type? Yes ® No ❑ Taxonomy (Subgroup): _AgB 1 AgC On Hydric Soil List? Yes ❑ No Profile Description: Depth (inches) Horizon Matrix Color (Munsell Moist) Mottle Colors Mottle Abundance/ Texture, Concretions, (Munsell Moist) Size/Contrast Structure, etc. 0"- 4" 0 10 YR 2/1 NIA N/A Muck/Detritus 4" - 24" 0 10 YR 211 NIA NIA Or anic/Fibric Hydric Soil Indicators: ❑ Histosol ❑ Concretions/Nodules Win 3"; > 2 mm) ❑ Histic Epipedon ❑ High Organic contents in Surface Layer in Sandy Soils ® Sulfidic Odor ❑ Organic Streaking in Sandy Soils ® Aquic Moisture Regime ❑ Listed on Local Hydric Soils List ® Reducing Conditions ❑ Listed on National Hydric Soils List ® Gleyed or Low-Chroma Colors ® Other (Explain in Remarks) Redox. Features (w/in 10" Criteria Met? Yes 1K No Ej Remarks: This soil pit consisted of an organic soil throughout the profile. Some sand was mixed in to the soil, and this may be due to the serious historic erosion problem on the uphill slope. 1: ViolaoIlitaIefil ® Recorded Data (Describe in Remarks): Wetland Hydrology Indicators: ❑ Stream, Lake, or Tide Gauge Primary Indicators: ® Aerial Photographs ❑ Inundated ❑ Other ® Saturated in Upper 12 Inches ❑ No Recorded Data Available ® Water Marks Comment: No standing water observed in aerialphoto.__ ® ® Drift Lines Sediment Deposits Field Observations: ® Drainage Patterns in Wetlands Secondary Indicators (2 or more required) Depth of Surface Water: 0 in. ❑ Oxidized Root Channels in Upper 12 Inches ® Water -Stained Leaves Depth to Free Water in Pit: 3 in. ❑ Local soil Survey Data ❑ FAC-Neutral Test Depth to Saturated Soil: 1 in. ❑ Other (Explain in Remarks) Criteria Met? Yes DQ No Remarks This data point was saturated to the surface and emitted a strong sulfuric smell when the profile was extracted. No standing water was observed in the aerial photo howevor there is a strong canopy on site and the seasonality of the photo may not be a fair indicator of hydrology. WETLAND DETERMINATION Hydrophytic Vegetation Present? Yes ® No Wetland Hydrology Present? Yes ® No Hydric Soils Present? Yes ® No 717 Is this Sampling Point Within a Wetland? Yes ® No ❑ Remarks This soil pit is being considered as Wetland sample #4 (WL-4). This sample point contains primary and secondary charackerisitcs of a wetland. BERGER/ABAM ENGINEERS, INC. 2of 2 Attachment B Wetland Buffer Averaging Analysis 17 February 2006 Table of Contents Section Page I. Introduction...................................................................................................................................I II. Background Information..............................................................................................................1 IV. Existing Site Conditions...............................................................................................................4 V. Proposed Buffer Averaging.........................................................................................................6 VI. Site Specific Determination of Buffer Width.............................................................................8 VII. Proposed Buffer Enhancement..................................................................................................21 VIII. Conclusions..................................................................................................................................21 IX. References.....................................................................................................................................22 Image No. 1: Existing Buffer Conditions...............................................................................................5 Image No. 2: Graving Animals in Buffer...............................................................................................6 Image No. 3: Existing Conditions of Proposed Buffer Reduction Area............................................7 Figure1— Site Map.....................................................................................................................................2 Figure 2 — Buffer Averaging Map............................................................................................................3 Figure3 — Slope Map...............................................................................................................................13 Figure4 — Buffer Vegetation...................................................................................................................14 Wetland Report BERGER/ABAM, A06112 17 February 2006 Page i of i I. Introduction Following the wetland delineation completed by BERGER/ABAM Engineers Inc. (Attachment A) on 17 February 2006, the client, Daniel Bretzke, has requested the completion of a site analysis for the suitability of buffer averaging in accordance with Renton Municipal Code (RMC) (4)(3)(050)(M)(60 and the associated guidance document The Science of Wetland Buffers and Its Implications for the Management of Wetlands by Andy McMillan (2000). Due to the presence of a large wetland on the southwest half of the subject site and the location of the proposed lot lines; the client is requesting the authorization of buffer averaging in accordance with the Renton Municipal Code. Because the characteristics and widths of buffers necessary to maintain aquatic resource health and functions are dependent on site -specific conditions (McMillan, 2000), the site has been analyzed for potential to reduce the standard width for one 340-square-foot triangular section of buffer. This document provides an assessment of site characteristics and analyzes existing conditions and proposed mitigation to ensure that the regulatory buffer width is sufficient to preserve wetland functions without being larger than necessary. This report has been prepared by BERGER/ABAM Engineers Inc. for exclusive use by Mr. Bretzke as supplemental documentation for land use actions with the City of Renton. No other persons may use the information contained in this report for commercial purposes without express written consent of both BERGER/ABAM Engineers Inc. and Daniel Bretzke. 11, Background Information The subject site is currently divided into three separate tax parcels. The delineated wetland and associated 50-foot regulatory buffer are situated across all three parcels and occupy more than one-half of the 2.25-acre subject site (See Figure 1- Site Map). The wetland area is primarily located on Parcel No. 1023059360 (hereby known as parcel "A"). Parcel A is 38,993 square feet in size. Of this, 25,293 square feet are occupied by wetland and 8,335 square feet are regulated as wetland buffer, limiting the development potential of this parcel to 5,365 square feet of area. Due to the location of the wetland, existing site conditions, the orientation of the existing lot lines, and the proposed development design, the applicant is requesting buffer averaging for a specific section of wetland buffer located on Parcel A. See Figure 2 for a site plan identifying the area of proposed buffer reduction and replacement. Wetland Report 17 February 2006 BERGER/ABAM, A06112 Page 1 of 1 40iw -Am 230M 2 r 1. �1023U5918$ NE�F1Dth 8t ee ' Figure No. 1 Site Map ' s—%.a wnwd ary.m,V 102305934T r�w.wneate. 1023059 Parcel uAn ^y a .y1. 9 _mod 159 1023059358 M. a j 1023059357 a� a•1 1 "` as 0 15 30 60 Feat 1 inch equals 50 feet i Do& sure.: aDy ce.rwty M. - - Qftch lww sla wr.w 5939 BERGERIAMM 1.1 rFA,e •. n Mn.l� MtNS4 4. iY.CY IrST 1r+i4Ax1� SCALE !-w i R ro 40 60 __ _ ----- Cf Y OF REWCXV SITE PW N ANI NEApW "l; •,T -'.�.....�.,.,�, .'/ _v t ' Ot o: d'�i it a 4r� y •�. TIC+. �} - ��r r .1-� �...i. - �` i i '.ers• r: �. ' LL .r.:•.tifn. I i . N Lre�NNA1Yrn•yi iliMf.f YIYiMwarlYii. ra l• : •'\ ..T•�'U' 4.rIwA4'� \ "g !� •�-",-.\ I,�,Ii:. wr,rl,JOgl 411LrwlarfaM _ 11„Iwt , F �t ++:'� .,,\ ,� v AO,,LA1q i fOt4ti11 FxN.r. � 1a1i:.p • ALI :01` 040 C Co VC09 :S A 14M iflhlry POLE JW CA TCI iu SI.Y ® SWUM Vwx* mfflo. k T 1WAeif1 VALV& 04Tra vL r_- 0 AN 44. i 1a ••A+1 m ,71wAGN1- • •fNFSMM F OM EJVAf71F1 x S1"O1 Ly,VA ri Oy cd WX 19K 'F!f P1/ PLA3 Rt FLAW PL4V YAmm As FW C'1 FSCA' y j AVWA." AN40 itAL 91AW0 fii $a.. &%L cm rYUC EfEE4 &W V MtiLYi1 Sw0. am or WrImmmV Iftorv, .� flMOTPO i:E — AW944W X1050 —M --- 11E111►l7 W •f:i i TW —�—•+^ CJ044 LARK F&UT { f P_I 7Ar riw w-'W[itkM,rlo-&1VA1:lw .4ti"* Uwe UNMI! �F 0a nif -OF-wr &O&f "Y1LGrw CCPUC* err; 10 fi.cjwwi Tp!f EA10T SWAw. ea :c4u-) r*r rc arA SWJ.n " .ecr-w I 'ON17`-Ft TACO ; WT jp C TO SC'-• 1�4A f�'J 1i'�:d, CAI ful:h6m. rws -mn vkioN rC .-rA. F- t r1V�if`1�`'►gr1MF- BEAJZWG 1M1.J1AU- 4 E78o;WU Cf A.rris TAt US., SYCfZLV. j1L .NrwrY Tiff 4R ill[. =A1,17 Ow !4 { 1.•T sO1; O;R K 9:C. tuff tG-p7 9p. �lrr S PIWA Zoe W LLVSWW Al f;C1lagEp A f10Pf il? l� II row AV 10, 1c A 1k... 1PFt 1 •� .y -4� ' .� -i• Vas T• _' S.�S A931I �• ,1 �L- �MSi\ PARCEL A t?C7t r E i( v K M Ilk ' S sal V 1� r ~ I �`r w ' •M'r VERTICAL DA4Ti1M. 1 - M. OFJWNTON AFNCH MAiQK NO QRM 101 NAVO 100! 'SEE inP F1}19 Vic— hf.•EVNE�I'v GN CCU!•'_'' :.-..-... Figure No. 2- Buffer Averaging Map Map Provided By Applicant Sze l Ill. Proposed Development The proposed development for this parcel will include the construction of one single family home. The site is zoned by the City of Renton as R-4, which allows up to four single-family residences per acre. No wetland alterations are being proposed. The proposed development plan will result in necessary buffer impacts; however, these impacts will be minimized and mitigated to the greatest extent possible to allow for reasonable use of the property and the placement of a building footprint while remaining in compliance with other dimensional restrictions imposed by the City of Renton. The proposed single-family residence will primarily be built adjacent to the wetland buffer, and long-term prevention of human intrusion will be maintained by the placement of a split rail fence with attached critical area easement signs prohibiting access to the buffer and wetland. Due to the dimensional limitations of the site the proposal includes the conversion of 340 square feet of wetland buffer to building footprint and the dedication of 340 square feet of lot area as wetland buffer. The proposed development also includes the enhancement of approximately 1,340 square feet of new and existing buffer. See Figure 2 for a diagram of this exchange and enhancement. This proposal will not cause a net Ioss of wetland buffer area and through enhancement, the proposal will help to better protect areas of the wetland and existing naturally vegetated buffer that provide the function of wildlife habitat. IV. Existing Site Conditions From across the wetland to the west and beginning at the wetland edge, the landscape develops into rolling hills and climbs away from the elevation of the wetland. Land within the buffer ranges from flat to 29 percent slope. The native vegetation on the upland portion of this site has been cleared many years ago for use as pasture and in conjunction with rural development. Currently, that portion of the wetland on Parcel A is naturally buffered by an upland vegetated strip of forested and scrub -shrub canopies that vary in width from 10 to approximately 40 feet beginning at the wetland edge and continuing uphill towards the existing single family residence. This vegetated strip lacks diversity and is primarily made up of Scots broom (Cytisus scoparius), Himalayan blackberry (Rebus discolor), black cottonwood (Populus baIsamifera ssp. trichocarpa) saplings, and red alder (Alnus rurra). Evidence of past clearing in this area was observed (stumps and charcoal) and the plant communities are not fully established and many of the trees that make up the buffer are still saplings. This existing vegetated buffer would benefit from enhancement, soil amendment, and the removal of invasive species. Beyond this strip of vegetation and further upland within the wetland buffer, the site is heavily impacted by grazing and rural development. Commonly characterized by bare soil and emergent vegetation, erosion and poor soil stability are apparent (See linage No.1: Existing Buffer Conditions). The long presence of ungulates has degraded portions of the wetland buffer by striping it of topsoil and inhibiting regeneration of vegetation in the area. This area would benefit from revegetation through restoration and the removal of grazing animals (See Image No. 2: Grazing Animals in Buffer). Section VII of this Wetland Report BERGER/ABAM, A06112 17 February 2006 Page 4 of 4 report describes the applicant's proposed restoration in more detail. Image No. L Existing Buffer Conditions Wetland Report BERGERIABAM, A06112 17 February 2006 Page 5 of 5 Image No. 2: Graving Animals In Buffer V. Proposed Buffer Averaging Renton Municipal Code (RMC) (4)(3)(050)(M)(60 states that "Standard wetland buffer zones may be modified by averaging buffer widths. Upon applicant request, wetland buffer width averaging may be allowed by the Department Administrator..." An applicant may request the use of buffer averaging to reduce the wetland buffer in a specific area to help facilitate the placement of a building footprint on a site that is dimensionally limited by wetlands and associated buffers. This provision is especially oriented to a site with varying levels of sensitivity, degraded conditions, and historic uses within the regulatory buffer. There are seven criteria that must be met for an application to be considered for buffer averaging. The criteria are identified below followed by a qualifying statement. That the wetland contains variations in ecological sensitivity or there are existing physical improvements in or near the wetland and buffer. The 50-foot regulatory buffer surrounding the Honey Creek wetland consists of areas of varying sensitivity. This is due to existing developments within the buffer and degradation of buffer conditions from historic grazing and rural development. The proposed buffer reduction through averaging includes a buffer creation and enhancement element as described in Section VII of this report. Image No. 3 below is a photo of the Wetland Report 17 February 2006 BERGER/ABAM, A06112 Page 6 of 6 conditions of the proposed area of buffer reduction. ii. That width averaging will not adversely impact the wetland function and values. The proposed buffer width averaging will result in no net loss of buffer. The proposed averaging will not adversely impact the wetland function and values because the proposed buffer averaging will reduce the buffer in an area that is already impacted and devoid of vegetation and that provides no function or value as buffer. The proposed buffer averaging will also widen the buffer in an area that is vegetated through buffer creation and will enhance the buffer through a buffer enhancement plan providing additional protection to the wetland function and values. See Section VII of this report for a description of the buffer enhancement plan. iii. That the total area contained within the wetland buffer after averaging is no less than that contained within the required standard buffer prior to averaging. The applicant is proposing buffer averaging including a reduction in buffer of up to 50 percentto a triangular width of 25 feet for 340 square feet of wetland buffer and the dedication of additional land as buffer for 340 square feet of nonbuffer area. The total area of wetland buffer after averaging will be the same as the standard required buffer prior to averaging, and there will be no net loss of wetland buffer. Buffer creation and enhancement is also being proposed to ensure a higher quality buffer as the result of this action. See Figure 2 for a site map depicting buffer averaging. Wetland Report BERGERIABAM, A06112 17 February 2006 Page 7 of 7 iv. A site specific evaluation and documentation of buffer adequacy based upon The Science of Wetland Buffers and Its Implications far the Management of Wetlands, McMillan, 2000, has been conducted. A site specific analysis of buffer adequacy has been completed. See Section VI below. V. In no instance shall the buffer width be reduced by more than fifty percent (50%) of the standard buffer or be less than twenty five feet (25') wide. The applicant is proposing buffer averaging including a reduction in buffer of 50 percent to a triangular width of 25 feet, converting 340 square feet of wetland buffer to building footprint. To compensate the applicant is proposing the dedication of additional land as buffer for 340 square feet of area on the same parcel. The applicant is not proposing the reduction of buffer by more than 50 percent or to a width of less than 25 feet. See Figure 2 for a map of the proposed buffer averaging. vi. Buffer enhancement in the areas where the buffer is reduced shall be required on a case -by - case basis where appropriate to site conditions, wetland sensitivity, and proposed land development characteristics. Buffer creation and enhancement in those areas where the buffer will be reduced and in those areas where the buffer will be expanded is being proposed. See section VII below for a complete description of the proposed buffer enhancement. The areas of proposed buffer enhancement is also shown on Figure 2. vii. Notification may be required pursuant to Subsection FS of this section. The applicant will comply with all noticing requirements of the City of Renton Municipal Code. VI. Site Specific Determination of Buffer Width Table 7 - Wetland Characteristics Record the following Information about the wetland under consideration. 1 Wetland area The area of wetland onsite is 34,135 sq. ft. (covering (in acres) the three parcels surveyed) and is part of a large wetland complex that extends south and west of the subject site. The total area has not been determined due to the scope of the completed delineation. 2 Wetland rating (class/category) This wetland has been referenced by the City of and name of rating system Renton as a Type II wetland in existing documents. 3 Hydrogeomorphic Class Riverine (rverine, depressional, slope, lacustrine fringe, estuarine fringe) 4 Cowardin classes present (forested, Forested and scrub -shrub Wetland Report 17 February 2006 BERGER/ABAM, A06112 Page 8 of 8 Table 7 - Wetland Characteristics Record the following information about the wetland under consideration. scrub/shrub, emergent, open water, aquatic bed) S Area of permanent open water None 6 Area of seasonal open water None T Area of vegetated standing'water Hard to quantify. Small pockets of vegetated standing water exist but are well dispersed. S Source(s) of water Input to the Honey Creek, intermittent streams, surface sheet wetland flow, groundwater. 8 Threatened/Endangered/Sensitive None known. or rare plant species present 10 Threatened/Endangered/Sensitive None observed. Among others, bald eagle (Haliaeetus or rare animal species present leucocephalus) and pileated woodpecker (Dryocopus pileatus) may occasionally use this site as habitat. 31 Known or expected bird species Expected bird species that may use this site as utilizing the wetland as habitat habitat include American robin (Turdus migratorius), wren (Troglodytes), and several other migratory species. However, a bird survey was not completed due to the scope of the project. A complete list of expected birds can be found in the King County Wildlife Habitat Profile, 1987. 12 Known or expected mammal Field observations support the presence of mammals species utilizing the wetland as due to the presence of scat and tracks. However, a habitat mammal survey was not completed due to the scope of this project. Expected species include deer mouse (Peromyscus maniculatus), raccoon (Procyon lotor), and coyote (Canis latrans). A complete list of expected mammals can be found in the King County Wildlife Habitat Profile, 1987. 13 Known or expected fish species None known. The nearest aquatic habitat that would utilizing the wetland as habitat support fish life is May Creek. 1.4 Known or expected herptlle species The presence of the northwestern salamander utilizing the wetland as habitat (Ambystoma gracile) and the long -toed salamander (Ambystoma macrodactylum) within the buffer area are possible due to the presence of the adjacent wetland. Additionally, garter snakes (Thamnophis spp.) and northern alligator lizard (Elgaria coerulea) may also be present; however, a herptile study was not completed due to the limited scope of this study. A complete list of expected herptiles can be found in the King County Wildlife Habitat Profile, 1987. Wetland Report 17 February 2006 BERGER/ABAM, A06112 Page 9of9 STEP 2: Describe the level of Impact from adjacent development and measures to be taken to minimize Impacts Description of Potential Development Describe the type of Construction of one single-family residence, including 15 development a split rail fence to restrict entry into the wetland buffer. Describe how surface water Currently, due to the degraded condition of the buffer, 16 runoff will be addressed improvements made through the proposed buffer Including plans for treatment enhancement plan will improve buffer conditions and release to wetlands or through increased sediment and nutrient capture and streams. uptake. Surface water collected from roof and storm drains associated with the development of this site will be addressed through the City of Renton stormwater review. The applicant has indicated that soil conditions on site are amenable to infiltration. No additional surface water is anticipated to be released to the buffer or wetland as a result of this development. Describe how surface runoff No additional surface water is anticipated to be 17 will affect the hydroperiod of released to the buffer or wetland as a result of this the wetland and what development. pollutants might be Introduced Into the wetland. Describe the potential for Some light and glare from the adjacent proposed 18 noise and Iight to affect the residential development may affect the wetland and wetland and steps taken to buffer. The City of Renton Code allows the Reviewing reduce noise and light Impacts Official to condition permits "directing lights from on the wetland. buildings or parking areas, or noise generating activities, away from wetlands". The applicant will comply with all conditions placed on the building permit. Additionally, the proposed site plan focuses all residential activities to the northeast side of the property on the opposite side of the structure from the wetland. Describe the potential for A split rail fence to restrict entry into the wetland and 19 human and pet intrusion Into buffer will be constructed in conjunction with the the wetland and steps taken to placement of critical areas signs along the fence and minimize intrusion. buffer boundary. This will assist in restricting access to the buffer and wetland, and will also raise awareness of the importance of protecting wetland resources. wetland Report 17 February 2006 BERGER/ABAM, A06112 Page 10 of 10 STEP 3: Describe the characteristics of the buffer luate the area within 300 feet of the wetland edge in the vicinity of the proposed development and answer the auestions below. Make a drawing to answer auestions 21-22 20a Described the mapped soil type including horizons, texture and drainage class. There are three soils located on or near this site as mapped by the Soil Survey of King County Area (Gale, Pringle, and Snyder; 1973). The mapping symbols and slope classes of the three Alderwood subgroups are: AgB: 0% to 6% Slopes AgC: 6% to 15% Slopes AgD: 15% to 30%: Slopes The King Conservation District describes Alderwood soils as: "Moderately well -drained soils underlain by consolidated glacial till (hardpan) at a depth of 24 to 40 inches. Alderwood soils formed in glacial deposits under conifers. They occupy upland areas at elevations between 100 and 800 feet. The annual precipitation is 35 to 60 inches, mostly rainfall between October and May. The frost -free season is 150 to 200 days." (King Conservation District) A typical alderwood soil profile from 0 to 27 inches is a dark brown gravelly sandy loam. From 27 to 60 inches, the soil takes a grayish brown weakly to strongly consolidated glacial till characteristic (hardpan). Soil permeability is rapid in surface layer and subsoil above hardpan material and very slow in the hardpan. The depth to the seasonal high water table is 2 to 3 feet and the water -holding capacity is seasonally low (summer) to seasonally high (winter). (King Conservation District). Observations made on Draw a typical soil horizon (0-20") for the buffer soils See data sheets from wetland delineation report. Wetland Report 17 February 2006 BERGER/ABAM, A06112 Page 11 of 11 Table 9 - Buffer Characteristics Evaluate the area within 300 feet of the wetland edge in the vicinity of the proposed development and answer the questions below. Make a drawing to answer questions 21-22 the landscape scale and during soil sampling were generally consistent with the descriptions provided in the Soil Survey of King County Area and by the King Conservation District. 20b Do field observations confirm Yes. the mapped soil type? 20c If not, describe soil type observed in the field Including horizons, texture and drainage class. SLOPE 21 On a drawing of the buffer area, <5% show areas where the slope Is: 5% -10% See Figure No. 3 attached. >10% VEGETATION 22 On a drawing of the buffer area, The site buffer is estimated to be 40% shrub, 30% Indicate approximate percent of forested, and 25% herbaceous mixed with bare. aerial cover of each vegetative strata as well as bare areas and Strata areas with buildings or Tree Impervious surfaces Shrub Herbaceous See Figure No. 4 attached. Bare Buildings/impervious 23 Describe measures that could The buffer could be enhanced through the removal of be taken to Improve the invasive species and the planting and maintenance of functioning of the buffer area. native vegetation. See section VI for a complete description of the proposed buffer restoration plan. Wetland Report 17 February 2006 BERGER/ABAM, A06112 Page 12 of 12 V V V V J. a � r F`., N E 10th Street V . 1, Legend Source: King County GIS, Puget Sound Lidar Consortium, -Surveyed Parcel Lines % Slope GeoDimensions Site Survey -Wetland Boundary <5% Figure No. 3- Slope Map ,ERGER/ABAM - 50 Foot Wetland Buffer 5- 10 % f N C I N E f A S I x C Y_ County Tax Parcel Lines am > 10% 1 inch equals 50 feet I* I N p o °gym €� g a, gs Z� L ai 8��s mCD � g fig$, pp $ o EE N m \W K a W � �0 F •� ► N ► �. r - - �• ! � .��J rT-�+J'.Js'•l •J •J •J ••� ••....••.r Jr, •, •. •.•�'rJ... . !. • . • • • r r J J r J • . . . , • • . . • . . . . n . J . ! . ! . . J . . r . STEP 4: Determine the buffer functions and width needed to protect the wetland Table 10 - Buffer Functions Based on the Information recorded in Tables 7, S and 9 above, determine which buffer functions are needed to protect the wetland. For each function determined to be needed, describe the width necessary to protect the wetland and provide a rationale for the width selected. include a description of enhancement activities proposed to improve the buffer or otherwise protect the wetland. Buffer Function Needed? Y/N Needed Width & Rationale Buffer or Site Enhancement Yes The function of sediment removal See section VII below. Sediment removal from surface water sheet flows is not being provided by the Additionally, the applicant will wetland buffer in its current provide for stormwater condition. The buffer is degraded infiltration, detention and and lacking emergent vegetation or grasses in many locations and treatment in compliance with erosion is apparent. The the City of Renton adopted regulatory buffer for this wetland Stormwater Manual and is currently set at 50 feet through prevent flow from lawns and standard application of code by surfaces that directly enters the City of Renton regardless of the buffer. buffer condition. This is a proposal for buffer The applicant will also use averaging, includinga reduction best management practices of buffer width to 25 feet for a to control dust during specific section of buffer that is construction. currently in a degraded condition and the addition of buffer in an area that is adjacent to an established forested community. This proposal also includes buffer enhancement for the area adjacent to the buffer reduction and for the area of buffer dedication. Following the completion and establishment of the enhanced buffer, and due to the improved vegetated condition of the buffer, a 25-foot enhanced buffer will be more effective at providing water quality function (sed€ment removal) than the existing standard 50 foot buffer with no enhancement. It is also important to note that this is a request for buffer Wetland Report 17 February 2006 BERGEWABAM, A06112 Page 15 of 15 Table Buffer Functions Based on the information recorded in Tables 7, 8 and 9 above, determine which buffer functions are needed to protect the wetland. For each function determined to be needed, describe the width necessary to protect the wetland and provide a rationale for the width selected. Include a description of enhancement activities proposed to improve the buffer or Otherwise protect the wetland. Buffer Function Needed? Y/N Needed Width & Rationale Buffer or Site Enhancement averaging through a reduction in buffer width for a specific section of the current regulatory buffer. The applicant is proposing additional buffer dedication to compensate for the site -specific reduction of buffer. The applicant is not proposing any impacts to the wetland. Yes The function of nutrient removal See Section VII below. Nutrlent removal from surface water sheet flows is not being provided by the wetland buffer in its current condition. The buffer is degraded and devoid of vegetation in many locations and there is no ability to provide this function. This is a proposal for buffer averaging including a reduction of buffer width to 25 feet for a specific section of buffer that is currently in a degraded condition and the addition of buffer in an area that is adjacent to an established forested community. This proposal also includes buffer enhancement for the area adjacent to the buffer reduction and for the area of buffer dedication. Following the completion and establishment of the enhanced buffer, and due to the improved vegetated condition of the buffer, a 25 -foot enhanced buffer will be more effective at providing water quality function (nutrient removal) than the existing standard 50-foot buffer with no enhancement. Wetland Report 17 February 2006 BERGER/ABAM, A06112 Page 16 of 16 Table 1 - Buffer Functions Based on the information recorded in Tables 7, 8 and 9 above, determine which buffer functions are needed to protect the wetland. For each function determined to be needed, describe the width necessary to protect the wetland and provide a rationale for the width selected. Include a description of enhancement activities proposed to improve the buffer or otherwise protect the wetland. Buffer Function Needed? Y/N Needed Width & Rationale Buffer or Site Enhancement It is also important to note that this is a request for buffer averaging through a reduction in buffer width for a specific section of the current regulatory buffer. The applicant is proposing additional buffer dedication to compensate for the site -specific reduction of buffer. The applicant Is not proposing any impacts to the wetland. Yes The function of toxics removal See Section VII below. Toxics removal from surface water sheet flows is (specify type of not being provided by the Additionally, the applicant will toxic substance) wetland buffer in its current comply with the adopted City of condition. The buffer is degraded Renton Stormwater Manual and and devoid of vegetation in many use provisions in this manual locations and the buffer does not that ensure the routing of all have the ability or capacity to new untreated runoff away from provide this function. Currently, the wetland and its buffer. The water flows freely across the applicant will also explore the compacted soil in the buffer potential to establish a covenant area. requiring the use of integrated pest management and limiting This is a proposal for buffer the use of pesticides and averaging including a reduction herbicides to outside of the of buffer width to up to 25 feet regulated buffer. for a specific triangular section of buffer that is currently in a degraded condition and the addition of buffer in an area that is adjacent to an established forested community. This proposal also includes buffer enhancement for the area adjacent to the buffer reduction and for the area of buffer dedication. Following the completion and establishment of the enhanced buffer, and due to the improved vegetated condition of the buffer, a 25 foot enhanced buffer will be Wetland Report 17 February 2006 BERGER/ABAM, A06112 Page 17 of 17 Table 1 - Buffer Functions Based on the information recorded in Tables 7, 8 and 9 above, determine which buffer functions are needed to protect the wetland. For each function determined to be needed, describe the width necessary to protect the wetland and provide a rationale for the width selected. Include a description of enhancement activities proposed to improve the buffer or otherwise protect the wetland. Buster Function Needed? Y/N Needed Width & Rationale Buffer or Site Enhancement more effective at providing water quality function (toxics removal) than the existing standard 50- foot buffer with no enhancement. It is also important to note that this is a request for buffer averaging through a reduction in buffer width for a specific section of the current regulatory buffer. The applicant is proposing additional buffer dedication to compensate for the site -specific reduction of buffer. The applicant is not proposing any impacts to the wetland. Yes The function of shading and See Section VI below. Shading & microclimate protection is not microcllmate being provided in full by the protection wetland buffer in its current condition. The buffer is degraded and devoid of vegetation in many locations and there is limited ability to provide this function. Some sections of the buffer are forested and do provide this function. This is a proposal for buffer averaging, including a reduction of buffer width to 25 feet for a specific section of buffer that is currently in a degraded condition and the addition of buffer in an area that is adjacent to an established forested community. The applicant is not proposing the removal of existing vegetation and is proposing a reduction of buffer in an area that is already impacted. This proposal also includes buffer enhancement for the area adjacent to the buffer reduction Wetland Report 17 February 2006 BERGER/ABAM, A06112 Page 18 of 18 Table 1 - Buffer Functions Based on the information recorded in Tables 7, 8 and 9 above, determine which buffer functions are needed to protect the wetland. For each function determined to be needed, describe the width necessary to protect the wetland and provide a rationale for the width selected. Include a description of enhancement activities proposed to improve the buffer or otherwise protect the wetland. Buffer Function Needed? Y/N Needed Width & Rationale Buffer or Site Enhancement and for the area of buffer dedication. Following the completion and establishment of the enhanced buffer, and due to the improved vegetated condition of the buffer, a 25 foot enhanced buffer will be more effective at providing shading & microclimate protection than the existing standard 50-foot buffer with no enhancement. It is also important to note that this is a request for buffer averaging through a reduction in buffer width for a specific section of the current regulatory buffer. The applicant is proposing additional buffer dedication to compensate for the site -specific reduction of buffer. The applicant is not proposing any impacts to the wetland. Yes Because of habitat provided by See Section VII below. Screening noise, the wetland and associated light, Intrusion buffer, this function will need to be preserved and enhanced. By Additionally, the applicant will orienting the home away from the design the single-family wetland and restricting access residence to locate activity that through preservation easement, generates noise away from the wetland intrusion and impact wetland and will direct all lights from noise will be limited. The associated with the structure will also help serve as a development away from the noise barrier from other wetland. Permanent fencing will developments located further also be installed, and through upland from this single-family enhancement, dense vegetation home. will be planted to help delineate the buffer edge and discourage This is a proposal for buffer disturbance. averaging, including a reduction of buffer width of up to 25 feet for a specific triangular section of Wedand Report 17 February 2006 BERGEWABAM, A06112 Page 19 of 19 Table1 - Buffer Functions Based on the information recorded in Tables 7, 8 and 9 above, determine which buffer functions are needed to protect the wetland. For each function determined to be needed, describe the width necessary to protect the wetland and provide a rationale for the width selected. Include a description of enhancement activities proposed to improve the buffer or otherwise protect the wetland. Buffer Function Needed? Y/N Needed Width & Rationale Buffer or Me Enhancement buffer. Due to the applicant's intended diligence in site design through low impact development and buffer enhancements, this minor reduction in buffer is not expected to impact the noise, light, and screening function of this wetland buffer. Yes In its current state, the wetland See Section VII below. General wildlife buffer provides differing levels of habitat protection based on its condition Additionally, the applicant will at different locations. This is a design the single-family proposal for buffer averaging, residence to locate activity including a reduction of buffer that generates noise away width of up to 25 feet for a from the wetland and will specific triangular section of buffer. Due to the applicants direct all lights associated intended diligence in site design with the development away through low impact development from the wetland. Permanent and buffer enhancements, this fencing will also be installed, minor reduction in buffer is not and through enhancement, expected to impact the habitat dense vegetation will be function of this wetland buffer. planted to help delineate the buffer edge and discourage disturbance. No N/A N/A Habitat for particular species Wetland Report 17 February 2006 BERGER/ABAM, A06112 Page 20 of 20 STEP 5: Determine the appropriate width of buffer and enhancement actions necessary to protect the wetland. Summary This is a proposal for buffer averaging, including a reduction of buffer width of up to (Describe the 25 feet for a specific triangular section of buffer. The applicant is proposing the overall width Conversion of 340 sq. ft. of buffer to building footprint. The applicant is also needed to protect proposing the addition of 340 sq. ft. of new buffer area as compensation, and the the wetland & a ' enhancement of up to 1,340 sq. ft. to help restore the ability of the buffer to summary of the perform key functions in protecting the wetland and maintaining water quality. It is enhancement important to note that the applicant is not requesting a complete reduction of buffer actions needed} and is only proposing development where the existing buffer is in a degraded condition and devoid of vegetation and topsoil. Section VII of this report details the applicant's proposal for buffer enhancement. VII. Proposed Buffer Enhancement' Included in the request for buffer averaging is a proposal for buffer enhancement. Due to the degraded conditions of the wetland buffer, the applicant is proposing buffer enhancement in the area adjacent to the proposed reduction and in the area of the proposed buffer expansion. The applicant proposes the enhancement of approximately 1,000 square feet of buffer and 340 square feet of newly dedicated buffer. Enhancement will include the manual and mechanical removal of invasive species, restoring soil conditions through decompaction and amendment, and the planting of native vegetation. Plantings will include western red cedar (Thuja plicata), Douglas fir (P. menziesu), bigleaf maple (Ater macrophylla), salmonberry (Rubus spectabilis), vine maple (Ater circunatum), osoberry (Gaultheria shallon), red elderberry (Sambucus racemosa), thimbleberry (Rubus spectabilis), and snowberry (S. albus). The enhancement plan will also include seeding with the appropriate and recommended certified grass seed mixtures. The purpose of grass seeding is to provide ground cover for soil stability to minimize erosion during the first years of growth of the proposed plantings. Seeding when combined with mulching helps to reduce erosion and helps serve as an herbaceous Iayer removing sediment from sheet flow and helping establish an emergent layer that the. site currently lacks. With the establishment and growth of tree and shrub species, many of the grasses will be shaded out as succession progresses. A complete enhancement plan detailing planting requirements, monitoring, contingencies, and costs will be submitted with the building permit application. Vill. Conclusions Based on the requirements outlined in the City of Renton Municipal Code, the factors identified in this report, and considering the City of Renton standard buffer width of 50 feet for Type II wetlands, this request for buffer averaging to convert 340 square feet of wetland buffer to building footprint and enhancement of up to 1,340 square feet of low quality degraded buffer will result in a net gain in wetland buffer function and enhanced wetland protection. The applicant is proposing to restore a regulatory buffer that Wetland Report 17 February 2006 BERGER/ABAM, A06112 Page 21 of 21 provides little functional value and protection in its current condition and is proposing the preservation of the buffer through protective measures for generations to come. IX. References Gale, Pringle, and Snyder.1973. Soil Survey of King County Area, Washington. United States Department of Agriculture, Soil Conservation Service. King Conservation District. 2000. King County Soil Descriptions. (http:llwww.kin cg d.org(pub soil.htm) King County. 1987. Wildlife habitat profile. King County Open Space Program. Parks, Planning, and Resource Department, Seattle, Washington. McMillan, A. 2000. The science of wetland buffers and its implications for the management of wetlands. Master's Thesis. The Evergreen State College. Washington State Department of Ecology. 1993. "Restoring Wetlands in Washington" Ecology Publications #93-17. Wetland Report 17 February 2006 BERGER/ABAM, A061I2 Page 22 of 22 Roger Short Plat r023a5P2�J 102305P203 ,r� 4°' 5 Y� ,`'f0i3u6D171 � .1,.. 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King County makes no rymsontadons or warren»", express or implied. as to accuracy, wrnpletaness, tlmaliness, or rights to the use of such Information. This document is not intended for use as a survey product. KGng County shall not be Ilabta for any general, special, Indira incidental, or consequential LQ damages including, but nol limited to, lost revenues or lost profda reeuldng from the use or misuse of the inform®tlon conlslned on this map. Any sale of King County this map or infotmallon on this map is prohibited except by written pormisslon of King County. Date: 971g12097 Source: icing County IMAP - Properly Information(http:fhuww.mat(olw.govlGl8AMAP) I GEOTECRNICAL ENGINEERING STUDY PROPOSED RESIDENTIAL SHORT PLAT 5521 NE 10" STREET RENTON, WASHINGTON G-2320 Prepared for Mr. Daniel Bretzkc 1313 - 33`d Avenue South Seattle, Washington 98144 August 31, 2006 GEO GROUP NORTHWEST, INC. 13240 NE 20'h Street, Suite 10 Bellevue, Washington 98005 Phone: (425) 649-8757 / Fax: (425) 649-8758 Geotechnical Engineers, Geologists Group Northwest, Inc. & Environmental Scientists August 31, 2006 Mr. Daniel Bretzke 1313 - 33'd Avenue South Seattle, Washington 98144 Subject: Geotechnical Engineering Study Proposed Residential Short Plat 5521 NE 10' Street, Renton, Washington Dear Mr. Bretzke: G-2320 GEO Group Northwest, Inc., has completed an investigation of subsurface soils at the above referenced site in Renton, Washington. This work was performed in accordance with our proposal dated July 18, 2006. GEO Group Northwest, Inc., explored subsurface soil conditions at the site by excavating five exploratory test pits TP-1 through TP-5, on August 8, 2006. Soils encountered at the test pit locations typically consisted of unconsolidated, loose to dense silty sand with minor gravel fill soils underlain with dense glacial till soils. Approximately 5.5 feet of fill was encountered in one test pit (TP-4) located in the western part of the site. No groundwater was observed in the test pits. Based upon the results of our subsurface investigation, it is our professional opinion that the site is geotechnically suitable for the proposed short plat development. We recommend that the proposed structures (roadways, buildings, etc.) be constructed on the dense native soils on or structural fill that is placed onto the dense native soils. We anticipate that in the proposed roadway area, excavation to a depth of approximately 4 feet below existing grades will be needed to reach suitable dense soils for support. 13240 NE 20th Street, Suite 10 - Bellevue, Washington 98005 Phone 4261649-8757 • FAX 4251649-8758 August 31, 2006 G-2320 Mr. Daniel Bretzke Page ii We evaluated the upper, unconsolidated soils for their suitability for stormwater infiltration or dispersion. Based on the high fines content of these soils, it is our opinion that these soils have relatively poor infiltration capability; however, water from roof downspouts and footing and wall drains can be discharged to dispersion trenches on the individual lots or possibly in the on -site wetland area. Additional findings and recommendations for geotechnically related aspects of the project are discussed in more detail in the text of the attached report. We appreciate this opportunity -to have been of service to you on this project. We look forward to working with you as this project progresses. Should you have any questions regarding this report or need additional consultation, please feel free to call us. Sincerely, GEO Group Northwest, Inc. NINNM C$ A x William Chang, P.E. ��� zotta Principal �f�NAi GEO Group Northwest, Inc. TABLE OF CONTENTS (.CONT'D) G-2320 ILLUSTRATIONS Plate 1 - Site Location Map Plate 2 - Site Plan Plate 3 - Existing Layout Plan Plate 4 - Proposed Plat Plan Plate 5 - Retaining Wail Backfill and Drainage Detail Plate 5 - Footing Drain Detail APPENDIX A Soil Classification Legend and Test Pit Logs APPENDIX B Grain -Size Distribution Test Results GEO Group Northwest, Inc. GEOTECHNICAL ENGINEERING STUDY PROPOSED RESIDENTIAL SHORT PLAT 5521 NE 10 n STREET RENTON, WASHINGTON G-2320 i N- RODUCTION 1.1 Project Description The project site is located near the eastern limits of a recently incorporated portion of Renton, Washington, along the south side of NE 10(' Street, approximately 200 feet west from Nile Avenue (also known as 148`'' Avenue SE). The general location of the project site is illustrated in Plate 1 - Site Location Map. Two existing residences, with addresses of 5521 and 5603 NE 10'h Street, are located on the north and northeast part of the site, respectively, as illustrated in Plate 2 - Site Plan. We understand that the site will be developed into a short plat that will consist of seven new residential lots, plus two lots that contain existing residences. The majority of the lots will be accessed via a new roadway that leads southward from NE 100' Street and enters the eastern part of the site. The proposed location of the new roadway is illustrated in Plate 3 - Existing Layout Plan. The new lots that are being planned for the platted site are illustrated in Plate 4 - Proposed Plat Plan. 1.2 Scope of Services i The tasks which we have completed for this study were conducted in general accordance with the scope of work presented in our proposal dated July 18, 2006. The scope of work included the following: 1. Observed the excavation of five exploratory test pits using a standard backhoe. The test pits were completed to depths ranging between 4 and 7.5 feet below the ground surface. The conditions encountered in the test pits were logged by an experienced geologist from our office, and representative soil samples were collected for moisture content and grain - size distribution testing. GEO Group Northwest, Inc. August 31, 2006 Mr. Daniel Bretzke G-2320 Page 2 2. Prepared test pit logs that present the soil classification and moisture test data. Also, bulk soil samples collected from three of the test pits (one per test pit) were tested for grain - size distribution. These samples represented the loose to medium dense soils that were encountered above the glacial till soils in the test pits. 3. Analyzed the findings from the site exploration and soil sample testing and developed conclusions regarding the use of infiltration or dispersion to manage stormwater on site, and evaluated the presence of erosion hazard areas on site (as described in City of Renton critical areas regulations), and 4. Performed engineering review and analysis for proposed earthwork, site drainage, and roadway support and pavement. 5. Prepared this report of our findings, conclusions, and geotechnical recommendations. 2 SITE CONDITIONS 2.1 Site Description The project site is located southwest of the intersection of Sunset Boulevard and 148`h Avenue SE in Renton, Washington, as shown in Plate 1 - Site Location Map. The site property and surroundings recently were incorporated into the City of Renton. The site is roughly rectangular in shape and has Comprises approximately 1.2 acres. The northernmost boundary of the site runs along NE 10' Street. The site is occupied by two single family residences (5521 and 5603 NE 10'b Street) and associated outbuildings (a detached garage, two barns, and two small storage sheds). The existing improvements and structures on the site are illustrated in Plate 2 - Site Plan. In general, the site is characterized by a moderate to steep, south and southwest facing slope which is interrupted by an essentially flat bench area that runs from the southeast toward the northwest part of the site, as illustrated in Plate 2 - Site Plan. At the base of the lower part of the slope is a wetland area that occupies the southwest and west part of the site. Based upon GEO Group Northwest,.Inc. August 31, 2006 G-2320 Mr. Daniel Bretzke -- - -- Page 3 information from a topographic survey of the site provided to us, the upper part of the slope on site has inclinations ranging from approximately 20 to 45 percent grade and is approximately 30 feet high. The steepest inclinations are located near the top of the slope on the eastern part of the site. The lower part of the slope on site has inclinations ranging from approximately 25 to 35 percent grade and is approximately 8 to 16 feet high (increasing from east to west). 2.2 Geologic Overview GEO Group Northwest, Inc. reviewed the "Geologic Map of the Renton Quadrangle, King County, Washington" published by the U.S. Geological Survey in 1965. According to the information on this map, the subsurface soils in the area of the subject site are mapped as Glacial Till (Qgt) which typically consists of compact, unsorted mixtures of silt, sand, gravel, and cobbles deposited and directly overridden by the Puget Lobe glacier. Soils in the southwestern portion of the site, occupied by wetlands, are mapped as being lake bottom, and bog type deposits (Qlp) that typically are composed of peat and organic silt and clay. 2.3 Field investigation GEO Group Northwest, Inc., explored subsurface soil conditions at the site by excavating and logging five exploratory test pits TP-1 through TP-5 on August 8, 2006. The test pits were excavated by a backhoe and were completed to depths ranging between 4 and 7.5 feet below ground surface. Soil samples were collected and returned to our office for moisture content and grain -size distribution testing. The test pits locations are shown on Plate 2 - Site Plan. 2.4 Subsurface Findings Soils encountered in the test pits typically consisted of layers of loose to relatively dense silty sand with minor gravel and occasional cobbles to depths of approximately 4 feet, underlain with very compact, dense silty sand and gravel soils interpreted to be glacial till. In test pit TP-4, approximately 5.5 feet of fill was encountered. In test pits TP-1 and TP-3 located on the upper slope area, the upper layers of unconsolidated silty sand were loose to medium dense, dry to damp, and approximately 4 feet thick. In test pit TP-2 on the flat area of the site, the upper layer of unconsolidated silty sand was approximately GEO Group Northwest, Inc. August 31, 2006 G-2320 Mr. Daniel Bretzke Page 4 1 foot thick and dry, and was underlain with medium dense to dense silty sand to approximately 4 feet below the ground surface. In test pit TP-5 in the northwest comer -of the site, the upper layer of unconsolidated silty sand was loose to medium dense and dry to damp to a depth of 4 feet. In test pit TP-4 located in the western part of the flat area, the upper approximately 5.5 feet of soils consisted of fill and were underlain with approximately 1.5 feet of mottled, medium dense sandy silt to silty sand that is suspected to be weathered native soil. For a more detailed description of the soils encountered in the test pits, please refer to the test pit logs provided in Appendix A. No groundwater seepage was encountered in the test pits. It should be noted, however, that groundwater conditions may fluctuate seasonally, depending on rainfall, surface runoff and other factors. Seasonal, perched groundwater may develop on top of the glacial till soils where poor drainage conditions are present. 3 EROSIQIN HAZARD EVALUA110N Moderate to steep slopes on the northern and eastern portions of the project site appear to have a surficial layer of dry, loose, fine sandy silty soil. In test pits TP-1 and TP-3 located in this area, these soils were approximately 3 to 4 feet thick. The underlying soils typically consisted of damp, medium dense to very dense silty sand with gravel and cobble and are interpreted to be glacial till soils. On unused parts of the site, these soils are vegetated with a mix of grasses, weeds, and brush. During our visit on August 8, 2006, we observed no evidence of soil erosion or slope movement on the site. Based on the conditions observed during our site investigation activities, we conclude that the moderate to steeply sloped areas on the northern and eastern portions of the site meet the criteria for classification as high erosion hazard areas per the City of Renton critical areas regulations. Significant potential does exist in these areas for sheeterosion or washouts of the surficial loose soils if they are denuded and exposed to flows of surface water. In order to mitigate the potential for soil erosion on the site during and following development, GEO Group Northwest, Inc., recommends that the following measures be implemented: GEO Group Northwest, Inc. August 31, 2006 G-2320 Mr. Daniel Bretzke Page 5 • Exposed cuts and soil stockpiles should be covered with plastic sheeting or mulched during unworked periods that are longer than 2 to 5 days (depending on the season). • Silt fencing and/or straw bales should be installed along the base of those slopes where grading will be performed, to prevent sediment -laden sheetwash from leaving the slope area. • Construction traffic entrances should be built and.stabilized at the start of the project and maintained as appropriate. • Water should not be permitted to flow over the tops of excavations or over areas of exposed slopes. Based upon our observations and interpretations of the site conditions, it is, our opinion that the site is currently stable. The proposed development of the short plat improvements will not increase the potential for soil erosion from the disturbed areas during or after construction, provided the recommendations contained in this Geotechnical Engineering Study are properly implemented. STORMWATE-R INFILTRATION EVALUATION Based upon the soils encountered at the test pit locations, it is our opinion that the site soils are relatively impermeable below depths of a few feet relative to existing surface grades, at which depth glacial till soils are typically encountered. The overlying few feet of weathered soils typically contain a significant proportion of fines and will have relatively low infiltration rates. The soils consist of relatively graded silty sand with lesser gravel, and have silt contents typically in the range of 20 to 30 percent. The results from sieve analyses of three samples of the weathered soils collected from test pits TP-1, TP-3, and TP4 had reported silt contents of 28, 23, and 22 percent and gravel contents of 32, 12, and 30 percent, respectively. Copies of the analysis' reports are provided in Appendix B. Based on the grain -size distribution characteristics of the soil samples that were tested, we conclude that the upper loose soils at the site consist of loamy sand, per the U.S. Department of CEO Group Northwest, Inc. August 31, 2006 G-2320 Mr. Daniel Bretzke Page 6 Agriculture Soil Textural Triangle classification scheme. Per the King County, Washington, Surface Water Design Manual (SWDM), 1998 Edition, soils of this type typically can be used for dispersion (but not for infiltration) of roof downspout water (SWDM, Section 5.1.1 and 5.1.2). A iypical dispersion trench has a length of 10 feet per 700 square feet of drained roof area. We recommend that footing drains and wall drains also be tightlined to the dispersion facilities. It may be permissible per applicable regulations to locate the dispersion trenches within the wetland buffer area on site. In cases where the dispersion trenches are located on the individual lots, the trenches should be located downslope. and no closer than 10 feet to the residence. CEO Group Northwest, Inc., recommends that.surface water from the proposed roadway be collected into one or more catch basins and be conveyed via a tightline system to the local storm drain utility, or dispersed into the wetland buffer. 5 CONCLUSIONS AND RECOMMENDATIONS 5.1 General Based upon the results of our subsurface investigation, it is our professional opinion that the site is geotechnically suitable for the proposed short plat development. In our opinion, new residences can be supported on conventional spread footings that bear on the dense site soils or on structural fill which is placed on the dense site soils. Similarly, the proposed roadway can be constructed on a subgrade of the dense site soils or on structural fill placed on the dense soils. Specific details these and other geotechnical aspects of the project are presented in the following sections. I 5.2 Site Preparation and General Earthwork 5_.z.1 Clearjag. and Subgmde Preparation The proposed construction areas should be stripped and cleared of surface vegetation, debris, uncontrolled fills, and other deleterious materials. Silt fences should be installed downhill of areas to be disturbed by construction activity to prevent sediment -laden surface runoff from being discharged off -site. During construction, exposed soils (including stockpiles) should be GEO Group Northwest, Inc. August 31, 2006 G-2320 Mr. Daniel Bretzke Page 7 covered with plastic sheeting when they are not worked for extended time periods. Alternatively, straw or mulch may be placed on exposed compacted soils in order to mitigate erosion. Water should not be allowed to stand in any area where foundations, slabs, or pavements are to be constructed. During construction, loose surfaces should be sealed at night by compacting the surface to reduce the potential for moisture infiltration into the soils. We recommend that the subgrade below slab -on -grade floors, sidewalks and driveways be compacted and then proof -rolled with a piece of heavy construction equipment such as a fully loaded dump truck or vibratory roller. Any soft spots or disturbed areas thus detected should be re -compacted or excavated and replaced with compacted structural fill. L 2 ;2 Tem oraExcavations and -Slopes Under no circumstances should temporary excavation slopes be greater than the limits specified in local, state and national government safety regulations. Temporary cuts greater than four feet in height should be sloped at an inclination no steeper than 1H:1V unless otherwise approved by the geotechnical engineer. Excavations into the very dense, glacial till soils may be sloped up to 1H:2V (Horizontal: Vertical) in inclination, provided that no water seepage or other adverse conditions are encountered. Permanent cut and fill slopes at the site should be inclined no steeper than 2H:1 V. Surface runoff should not be allowed to flow uncontrolled over the top of slopes into the excavated area. During wet weather exposed cut, slopes should be covered with plastic sheeting ; during construction to minimize erosion. If groundwater seepage is encountered during construction, excavation of cut slopes should be halted and the cut slopes should be re-evaluated by GEO Group Northwest, Inc. L21 Structural Fill All structural fill material used to achieve design site elevations below buildings and below non - structurally supported slabs, sidewalks and driveways should meet the requirements in this report GEO Group Northwest, Inc. August 31, 2006 G-2320 Mr. Daniel Bretzke Page 8 for structural fill. During wet weather conditions, material to be used as structural fill should have the following specifications: 1. Be free draining, granular material containing no more than five (5) percent fines (silt and clay -size particles passing the No. 200 mesh sieve); 2. Be free of organic material and other deleterious substances; 3. Have a maximum size of three (3) inches in diameter. All fill material should be placed at or near its optimum moisture content. The optimum moisture content is the water content in soil that enables the soil to be compacted to the highest dry density for a given compaction effort. During wet weather conditions we anticipate that the silty sand site soils (both the loose shallow soils and the underlying glacial till soils) will be difficult to compact to meet structural fill specifications because of their moisture sensitive character. Consequently, if earthwork occurs during the wet winter months of the year it is unlikely that the on -site soils will be suitable for use as structural fill. Alternatively, an imported granular fill material may be needed; such a material will provide more uniformity in character and be easier to compact to meet the recommended specification for structural fill. If the on -site soils are to be used as structural fill, it will be necessary to segregate the topsoil and any other organic- or debris -containing soil, because such soils would be unsuitable for use as structural fill. Excavated on -site material that is stockpiled for later use as structural fill should be protected from rainfall or contamination with unsuitable materials by covering it with plastic sheeting until it is used. If the material is particularly dry, it may need to be moisture conditioned before it can be used as structural fill. Structural fill should be placed in thin horizontal lifts not exceeding ten inches in loose thickness. Structural fill under buildings should be compacted to at least 95 percent maximum density, as determined by ASTM Test Designation D-1557-91 (Modified Proctor). Structural fill in pavement subgrade areas should be compacted to at least 90 percent of the maximum dry density, with the exception of the upper twelve (12) inches. The top twelve (12) inches should GEQ Group Northwest, Inc. August 31, 2006 Mr. Daniel Bretzke be compacted to at least 95 percent maximum dry density, as determined by ASTM Test Designation D-1557-91 (Modified Proctor). 19 )PIAT] We recommend that GEO Group Northwest, Inc., be retained to evaluate the suitability of structural fill material and to monitor the compaction work during construction for quality assurance of the earthwork. 5.2.4 Roadwgyand Pavement Page 9 We recommend that the proposed roadway be supported on a prepared subgrade of compacted, unyielding native soil, or structural fill as necessary to achieve design grades. The prepared subgrade should be proof -rolled with a piece of heavy construction equipment such as a fully loaded dump truck or vibratory roller under the observation of the geotechnical engineer. Any soft spots or disturbed areas detected should be re -compacted or excavated -and replaced with compacted structural fill. The pavement section for the roadway can consist of at least 6 inches of base course overlain with at least 3 inches of asphalt. 5.3 Foundations The proposed buildings may be supported on conventional strip and column footing foundations that bear on the dense site soils or on compacted structural fill placed on top of the dense site soils. Based upon the findings from the subsurface investigation, it appears that some over - excavation may be necessary at the lot 3 building pad location. GEO Group Northwest, Inc. should be retained to verify that the new spread footing foundations are bearing on the dense site soils or compacted structural fill placed on top of the competent site soils. Individual spread footings may be used for supporting columns and strip footings for bearing walls. Our recommended minimum design criteria for foundations bearing on the dense site soils or compacted structural fill placed on top of the competent site soils are as follows: - Allowable bearing pressure, including all dead and live loads Medium dense native soil = 2,000 psf GEO Group Northwest, Inc. August 31, 2006 G-2320 Mr. Daniel Bretzke Page 10 Dense native glacial till soil Compacted structural fill = 3,000 psf = 2,000 psf - Minimum depth to bottom of perimeter footing below final exterior grade = 18 inches - Minimum depth to bottom of interior footings below top of floor slab = 18 inches - Minimum width of wall footings = 16 inches - Minimum lateral dimension of column footings = 24 inches - Estimated post -construction settlement = % inch - Estimated post -construction differential settlement; across building width ='/z inch A one-third increase in the above allowable bearing pressures can be used when considering short-term transitory wind or seismic loads. Lateral loads can also be resisted by friction between the foundation and the supporting compacted fill subgrade or by passive earth pressure acting on the buried portions of the foundations. For the latter, the foundations must be poured "neat" against the existing undisturbed soil or be backfilled with a compacted fill meeting the requirements for structural fill. Our recommended parameters are as follows: - Passive Pressure (Lateral Resistance) , • 350 pcf equivalent fluid weight for compacted structural fill • 350 pcf equivalent fluid weight for native dense soil. - Coefficient of Friction (Friction Factor) • 0.35 for compacted structural fill • 0.35 for native dense soil GEO Group Northwest, Inc. August 31, 2006 Mr. Daniel Bretzke 5.4 Permanent Basement and Conventional Retaining Walls G-2320 Page l l Permanent basement walls restrained horizontally on top are considered unyielding and should be designed for a lateral soil pressure under the at -rest condition; while conventional reinforced concrete walls free to rotate on top should be designed for an active lateral soil pressure. Active Earth Pressure Conventional reinforced concrete walls that are designed to yield an amount equal to 0.002 times the wall height, should be designed to resist the lateral earth pressure imposed by an equivalent fluid with a unit weight of: • 35 pcf for level backfill behind yielding retaining walls; • 45 pcf for 25% sloped backfill; • 60 pcf for 50% sloped backfill; At -Rest Earth Pressure Walls supported horizontally by floor slabs are considered unyielding and should be designed for lateral soil pressure under the at -rest condition. The design lateral soil pressure should have an equivalent fluid pressure of: • 45 pcf for level ground behind permanent unyielding retaining walls; • 60 pcf for 25% sloped backfill; • 75 pcf for 50% sloped backfill; Passive Earth Pressure • 350 pcf equivalent fluid weight for structural fill • 350 pcf equivalent fluid weight for native dense soil Base Coefficient of Friction • 0.35 for structural fill • 0.35 for native dense soil We recommend that a vertical drain mat, Miradrain 6000 or equivalent, be used to facilitate drainage behind permanent concrete basement walls and retaining walls. The drain mat core is CEO Group Northwest, Inc. August 31, 2006 G-2320 Mr. Daniel Bretxke Page 12 placed against the wall with the filter fabric side facing the backfill. The drain mat extends from the finished surface grade, down to the footing drain pipe. A minimum 18 inches of clean, free - draining, washed rock, crushed rock, or pea gravel should be placed in the bottom of the footing trench. These recommendations are schematically illustrated in Plate 5 - Retaining Wall Backfdl and Drainage Detail. We recommend using an imported relatively free -draining pit -run sand or gravel as structural backfill behind the walls. This material should have less than 5 percent fines (that portion of the total weight passing a #200 sieve). Backfill material behind retaining walls should be compacted to 90 percent of the maximum dry density determined by ASTM D 1557-91 (Modified Proctor). 5.5 Slake -On -Grade Floors We understand that the proposed residences may have slab -on -grade concrete floors. We recommend that the subgrade for these floors consist of medium dense to dense native site soils or compacted structural fill placed on top of unyielding, competent.site soils. We recommend - that GEO Group Northwest, Inc. be retained to verify that the subgrade for the slab -on -grade floors meets the aforementioned criteria prior to the concrete placement. To avoid moisture build-up on the subgrade, slab -on -grade floors should be placed on a capillary break, which is in turn placed on the prepared subgrade. The capillary break should consist of a minimum of a six (6) inch thick layer of free -draining crushed rock or gravel containing no more than five (5) percent finer than No. 4 sieve. A vapor barrier, such as a 6-mil plastic membrane, is recommended to be placed over the capillary break beneath the slab to reduce water vapor transmission through the slab. Two to four inches of sand may be placed over the barrier membrane for protection during construction. 5.6 Drainage GEO Group Northwest, Inc., recommends that.surface water from the proposed roadway be collected into one or more catch basins and be conveyed via a tightline system to the local storm drain utility, or dispersed into the wetland buffer. CEO Group Northwest, Inc. August 31, 2006 G-2320 Mr. Daniel Bretzke Page 13 5,,6.2 Foundations and Roof Drains We recommend that drains be installed around the perimeter foundations of new residences or other buildings that are constructed on site. The drains should consist of a four (4) inch minimum diameter perforated rigid drain pipe laid at or near the bottom of the footing at a gradient sufficient to generate flow toward the tightline location. The drain line should be bedded on, surrounded by, and covered with a free -draining rock, pea gravel, or other free - draining granular material. The drain rock and drain line, should be completely surrounded by a geotextile filter fabric, such as Mirafi 140N or equivalent. After the drains are installed, the excavation should be backfilled and compacted to surface grade. These recommendations are schematically illustrated in Plate 6 - Footing Drain Detail. Roof downspouts and foundation footing drains should be tightlined separately to their respective appropriate discharge locations, such as dispersion trenches as discussed above in Section 4 - Stormwater Infiltration Evaluation in this report. We also recommend that sufficient cleanouts be installed at strategic locations in both drainage systems to allow for future periodic maintenance. ! 1 TKUATIONS This report has been prepared for the specific application to this site for the exclusive use of Mr. Daniel'Bretzke and his authorized representatives. We recommend that this report be included in its entirety in the project contract documents for use by the contractor. Our findings and recommendations stated herein are based on our field observations, experience and judgement. The recommendations are our professional opinion derived in a manner. consistent with the level of care and skill ordinarily exercised by other members of the profession currently practicing under similar conditions in this area and within the budget constraint. No warranty is expressed or implied. In the event the soil conditions are found to vary during site excavation, GEO Group Northwest, Inc. should be notified and the above recommendations should be re-evaluated. GEO Group Northwest, Inc. August 31, 2006 G-2320 Mr. Daniel Bretzke Page 14 7 ADDITIONAL SERVICES We recommend that GEO Group Northwest Inc. be retained to perform a general review of the final design and specifications for the proposed development to verify that the earthwork and foundation recommendations have been properly interpreted and implemented in the design and in the construction documents. We also recommend that GEO Group Northwest Inc. be retained to provide monitoring and testing services for geotechnically-related work during construction. This is to observe compliance with the design concepts, specifications or recommendations and to allow design changes in the event subsurface conditions differ from those anticipated prior to the start of construction. 8 CLOSfNG We appreciate this opportunity be of service to you on this project. We look forward to working with you as this project progresses. Should you have any questions regarding this report or need additional consultation, please feel free to call us. Sincerely, GEO Group Northwest, Inc. Keith Johnson Project Geologist William Chang, P.E. Principal Engineer GEO Group Northwest, Inc. ILLUSTRATIONS G-2320 GEO Group Northwest, Inc. GE4 E w i G _,* t TP-5a�' �' a aev. DPW rasMn i z 3F Cr'M L TP-4 nfM e a•af'rO'f rPO.M' I •". 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PROPOSED RESIDENTIAL SHORT PLAT Geatechnicai Engineers, Georagisu, & 5521 NE 10TH STREET @nvironmenW Scientists RENTON, WASHINGTON SCALE 1" = 50' DRAWN BY - KI CHECKED BY WC DATE 7/31/06 1 PROJECT NO. 6-2320 1 PLATE 2 i i A - - 03/O2/2dOs rn - --�� - �— - - - FOUNO 4" CQNC MoLmENT WITH 1/2" COPPER PIN. N.E. 1 ITN STREET -PUBLIC ROADWAY- - T - DOWN 1. 5' IN CASE LLi 0 POINT NO. 1945 CITY OF RENTON caNrRQL 588'16'10'E 661.76' CALC`❑ N.E_ SEC. CORNER OF o w ~^ SEC. io-23-5 o t� 0 SBB'16'1d"E 431.69'{ 4 l31.56' 1L" 100.04' 100.04' �ATCFI BASIN v 2 h13 121.651 70.00'7 100.04' RIFT ELEV.=469.24' x "A" 80.03' S8B'f6' 10"E - - - c�i� * rsab BSBL `, TP-5 AREA $ Q 70.03 r� t o - tn TP-3 tom' N AREA LU DK Y C� 1. 431. 83 OO FT . tV O� h� _. J o W �,o c W "gip INGRESS. BAM /to �� NEW LOT A\ cu I�� BUILDING EASEMENT J 3 099 SO. F NEW UNE o ft TO REMAIN m tail O r° I NETLAND � M d 61 m v AREA •~ c .2 p 72.3' cu HOUSE NO. 560 3 cn S88'I6'12'E'- 121.S9 z TO REMAIN AR ZOhEP R-4 is w4l 0 TPA Ai-uw x N00'02'42"E 8.2' 30.00'(}M 88'16'!0"EOL❑ LINEED Cu co 30.ofm N�.0. S88'16' 10-E 70.03' S88'16'10'E rn70.03' d O�70.00. EDGE OF c" Vg°L3w ► N WETLAND v p�' �BUFFER N �� �� 0.03 N L� LINE`i v Q �� p 03/02/20d6 11 LM a o ` p 5o O�� Q MOVE5 ZONED R -4 �� MONUMENT WITH COPPER PI CONC 10 DOWN 1.6' IN CASE Z Z 15ji'05/NEW �3'A o ti t�P O=�O �O�Q�� ELEV. ON TACK 512.02' Q� i E� pp. o • v '$u, O y OE. F SEC. CORNER5m <u QP SO �a,m N P w N� BARN to�ii' Loa6 NSF ``rC'ED w vvo�.ovxto�9�a LOT C� 0. :NE N $-' y "��0� if rn ,AaE�-63.130.91 SD. FT.v TP-2 `* �; � cm 0- R" P •'e N ,� N'`, f a 0 Q �/ o o TP-i N LEGEND NEW LOT C N �'6� ` Z iF 31. 1a1 so. F i. v a�� v � D7��UHE ,ZEXPLORATORY TEST PIT z"�'WET��,00grTP-1(APPROXIMATE LOCATION) Y v ifHLEE100.04'100-04' �70.03' 70.03' 2-E 361.78' Z S. 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P i Y Y i =. - i LC �� �` 4! b! ul N- W i+1 Y Y ` �% i-;. - c iY� ;v w a :WE cu- 04 Y i�iw�inr lmromm"-]Y 11 1 �` ` �`� o' �� a* t cm - o! w� oo o+~+ v� N ci ... = TP-2 . co '20 z o oa --------- �-• o z Y Y i Y Y i ��%` z TP-1% z Y v Y Y Y i Y i ..�Y. Y Y Y S88'2D 02- E =- W20 2'E LEGEND Z91.78 • �/ Y 70. 8.20' 02'E S870.03 S88 -� ' 02'E „ ' 70.03' — EXPLORATORY TEST PIT SW W -E se820'oz'E � _ -'A, - _ _� JL 588.20.02'E — (APPROXIMATE LOCATION) e81.s0• 170.07' TP-1 so goo SCALE: I INCH = 50 FEET Base reap from Lot Line Adjustment Map by GeoDimensions, dated June 21, 2006. mall Slope to drain+ awayfrmn teafi Vertical Drain Mai (Mira&%dn 6000 or equivalent) Relwtwely Inwnwable CbmpadedBad$17 Free-dn*r g +nateria4 such as trashed rock or dvshed roe* GeakrWe p4ino 140 Nl, or equtvalentj 4 or 6 inch diameter slotted or perforated PVC pipe NOT TO SCALE NOTES: l_) Do not replace rigid PVC pipe with flexible corrugated plastic pipe. 2.) Perforated or slotted PVC pipe should be tight jointed and laid with perforations or slats down, with positive gradient to discharge. 3.) Do not connect roof downspout drains into the footing drain lines. 4.) BacUill should be compacted to 90% of maximum dry density based on Modified Proctor. The top one foot should be compacted to 95% of maximum dry density if baeldill is to support sidewalks, driveway, etc. RETAINING WALL BACKF ILL =Group Northwest Inc, AND DRAINAGE DETAIL PROPOSED RESIDENTIAL SHORT PLAT Geotodinical Engineers, Geologists, a 5521 NE 10TH STREET Environmental Scientists RENTON, WASHINGTON SCALE: NONE I DATE: 8/30/06 1 MADE: KJ I C11KD. WC I JOa NO: G-23201 PLATE 5 slope to da- away from wall '•�? .t :,-S�'r• :Y'�r �. _^' S%',•`�JS!�i; :i •[�: 7;ii3 i ��f �%"� �' 1•}•a.}�� • ''�:�:•i7. Fti � y.,f.1ti, SLAB s:��.Nyli�.�:: �:�yi �:t'J ••!�l`cY::7L .ir2'is�.f ��i }��: :;t. . i(• �..� ,1 .1• ••iY w':1.1ei`n r�:5 j. i,� 1 «tom Nil x.'1. J :��.•" Rdattvdyurpermeable ar..� h•ti. 1�1 'srSL. ti.f yr« '.1:iV-�i: CAPILLARY BREAK campacted backfMHIM :! c r r; ,x� ., a • .... `;'''. , 'ei�rt=:..:y.�'r• ��fi;r-;s•:i_.fr�yii��:--^•. Geolantlle filler fabric (Mrrafi 144 NL, or egpivaki4 Free draining material - FOOTING (Washed crushed rock I II or drain rock) Minimum 4-inch diameter slotted or perforated PVCpim with positive gradient to discharge NOT TO SCALE NOTES: 1.) Do not replace rigid PVC pipe with flexible corrugated plastic pipe. 2.) Perforated or slotted PVC pipe should be tight jointed and laid with the perforations or slots down, and with positive gradient toward discharge. 3.) Do not connect roof downspout drains to the footing drain lines. 4.) Backfili should be compacted to 90% of maximum dry density based on Modified Proctor. The top 12 inches,ofbackfill should be compacted to 95% of the maximum dry density if backfill is to support sidewalks, driveway, etc. -... FOOTING DRAIN DETAIL L111JI Group Northwest, Inc. PROPOSED RESIDENTIAL SHORT PLAT err Geotochnicai Engineers, Gedogists, E T� 5521 NE 10TH STREET Environmental scientists RENTON, WASHINGTON SCALE: NONE I DATE: 8/30/06 1 MADE: KI C11KD: WC I JOB NO: G-2320 PLATE 6 APPENDIX A SOIL CLASSIFICATION LEGEND AND TEST PIT LOGS G-2320 CEO Group Northwest, Inc. LEGEND FOR SOIL CLASSIFICATION AND PENETRATION TEST DATA UNIFIED SOIL. CLASSIFICATION SYS71`M (Uses) GROUP MAJOR DNISION TYPICAL DESCRIPTION SYMBOL LABORATORY CLASSIFICATION CRITERIA CLEAN GVY lval GRAO%O Cf:AVEl.3.•GRAVF7.•.SNIO iIORURE. Ou - (050! DIG) greater than 4 GRAVELS LITTLE OR NO FINES CONTCONTENTCc a pm?I mo - DW) beereat 1 and 3 . CRAVENS faba orno OF FINES BELOW 5!LSAND Gp POORLY GRADED GRAVELS. AND GRAVEL CLEAN GRAVELS NOT ItEEiV4G ABOVE COARSE -GRAINED PAore Than Nag wml k"I'LIRES Lm" OR NO FINES REQUIREMENTS 301 S cum FrAcom Is ONriTY GY SILTY GRAVELS. GRAVEL-%V41-SLT MMTUFtCS (;aAk AT7ERBERG LOJfTS BELOW -e UNE. Lav" ThaA N0. 4 *�q1 y y CONTENT or PI LESS THAN 4 OF FINES E7ICsaS M� GC CLAYEY GRAVELS. CRAVELS-QAY MIXILRES GG ATTEABE G UMM AsavE A' LIFE. hAr som 1 6m) or P.L MORE THAN 7 SAHIB CLEAN SW WELL GRADED SANDS, GRAVELLY SANDS, LITTLE OR Cm - am 10101 greairs our, 0 SA MS NO F111*9 Cc = (030 f I (D10. 060) bd. I and 3 (hero Than Yhtl CONTENT OF FINES BELOW 5Y (tN6a or m PGOrII Y GRADED SANDS, GRAVELLY SANDS, lf1 ILE ap CLEAN SANDS NOT MEETING ABOVE M— Than Ha# by Smaft Than No. 4 Win) OR NO FINES RECANT 143CTS W" t L-W Than Swm1 DOTTY Sit SILTY SANDS. SANDSLT WXTlisFS ATTETMERG LAM BELOW 'X UNE No. 200 Slew sib py I FGC THAN { SAHM CONTENT OF FINES SC CLAYEY SANDS. SANDQAY MIXTURES ATTUMOW LWTS ABOVE ALINE (W m toots EXCEEDS 1 r11tl1 P1 Mom THAN r L SILTS <60% iaL 0� A{Jna m • PusLICOyChart. FPC-GRA04M NOORA s OrOanlrsl Laid SO" S CLAYS �b CL (Above ^AJm on PWsgY ata4 mmag le No.(**) 14,W LJd CH >50% Lass Thin Ha by WeWd Lwg-Thran ORGANIC SILTS i Liq` b OL Nm 200 SIC" CLAYS NAow, A4Jne on Char-) ' om U ON NIGFLY ORGANIC SOILS Pt SOIL PARTICLE SIZE UA STANDARD SIEVE FRACMN SIN Relmh d 85M slra Si.— Sire I�+ml 1-1 SILT I CLAY Mo 0.075 ;tom • FINE 840 0.425 0200 0.075 MEDIUM 010 2.00 040 0.421 COARSE N 4.76 M 2.00 FINE 0.75 19 04 4.75 COARSE 3' TO 0.75' 19 COBBLES 76 mm b 203 mm BOLIMERS > 203 mm ROCK iRAGMENTS > 76 mm ROCx >0.70 cubic meter in `otu m INORGANIC SILTS, ROU FLOUR. SANDY SLTS OF SLIGHT F ASTiCITY - gNORGANIC SILTS. MICACEOUS OR DIATOMACEOUS. 60.1 FINE SANDY OR SILTY SOIL X INORGANIC CLAYS OF LOW PLASTICITY. GRAVELLY, 640 SANDY. OR SILTY CLAYS, CLEAN CLAYS O }Z t 30 INORGANIC CLAYS OF HIGH PL ASTICLIY, FAT CLAYS U H 20 ORGANIC SL75 AND ORGANIC SILTY CLAYS OF LOW PLASTICITY d. 10 ORGANIC CLAYS OF HeGH PLASTICITY .a --I - Mom sommullm lmrmmmlmmmm� 0 FAA NPA00=0 0 10 2'0 310- 4o 5n 60 70 00 00 too PEAT AND OTHER 111GI CY ORGANIC SOILS LIQUID umff GENERAL. GUIDANCE FOR ENGRIEERNG PROPERTIES OF SOILS. BASED ON STANDARD PEIIIETRATION TEST ISPT) DATA SANDY SOILS SILTY i CLAYEY 50fLS Btorr C49tMs PARWI a friction An9N 8bW COrna . N DerW % R dw— N Sao Cj% tzf D owdobom 0-4 0 -15 Very Lose < 2 < oz Very tuft 4.10 15.35 26-30 Lam 2-4 025.0.50 Soft 10 - 30 35 - 65 25 - 35 Medlum Dense 4-8 GAII.1.10 MIadk m Sdff 30 - 60 55 - 03 35. 42 Dmge B -10 1.00 -2.00 sw >50 85-100 36-46 Very Delete 15-30 2-00-4.00 Varysm � 30 > 4.00 Hard LfjW@j Group Northwest, Inc. Geotechn"Engineers,Goo Ingests, & Erervironrnamal Scierdists M40 NE 21Nh Sbnel Swim 10 Bek a, WA 9=5 7 Phone (425104"757 Fax (425)64WSa PLATE At LOGGED BY: KJ TEST PIT NO. DATE EXCAVATED: TP -1 8/8/06 GROUND ELEV: 437' (+/-) DEPTH It. USCS SOIL DESCRIPTION SAMPLE No. Water '/. OTHER TESTS/ COMMENTS ML- Brown SILTY SAND to SANDY SILT, loose, dry, sand is SM predominantly fine grained, minor medium sand to gravel and cobble, some cohesion and blocky texture in upper 1 foot of soil. 1 83 1 2 ML SM As above, light brown, d , dry, cohrsionless some tanning of pit walls. 2 9.0 I i 3 ----- ----------------------------------------------------- i Grayish brown SILTY SAND, damp, loose to medium dense, sand is BULK SM somewhat more graded than above, 30-35% fines, more gravel and cobble, no running of pit walls. 4 ----- ------------------------------------------------------- 3 11.0 SM Brownish gray SILTY SAND, damp, dense, sand is mostly fine and medium grained with some gravei and cobble, 15-20%. fines (GI.AC[AL TILL.). A 11.2 5 6 Bottom of test pit at 4.5 feel below ground surface. No groundwater observed. 7 t1 9 10 I Group Northwest, Inc. Geotechnical Engineers, Geologists, S �r Environmental Scientists TEST PIT LOG PROPOSED RESIDENTIAL SHORT PLAT 5521 SE 10TH STREET RENTON, WASHINGTON JOB NO: . G-2320 I DATE: 8110/06 1 PLATE LOGGED BY: KJ TEST PIT NO. DATE EXCAVATED: TP-3 8/8/06 GROUND EiLEV: 455' (+/-) DEPTH USCS SOIL DESCRIPTION SAMPLE Water OTHER TESTS/ ft.No. % COMMENTS ML- Light brown SILTY SAND to SANDY SILT, loose, dry, sand is SM predominantly fine grained, minor medium sand to gravel, 30% fines, some cohesion and blocky texture in upper few inches of soil, but soil 1 6.7 1 underneath "nuts". Black flexible perir pipe and wash rock found at 1 foot 2 SM Tan to pale brown SILTY SAND, dry to damp, loose; fine grained, 15- 20°/u fines, some light grayish zones. 2 3.1 S---- ----------------------------------------------------- Light gray -brown SILTY SAND as above, damp, loose to medium BULK SM dense, sand is somewhat more graded than above, more gravel and cobble, no running of pit walls. 3 3.5 4 ............................................................ - SM- Gray -brown SILTY SAND, damp, dense to very dense, 15-20% fines, - sand is mostly fine and medium grained with'gravel and cobble (GLACIAL TILL). N 4 2.8 _/T B Bottom of test pit at 4.5 feet below ground surface. No groundwater observed. T 8 i 9 10 [! Group Northwest, Inc, Geotadrnical Engineers. Geologists, d Environmental Scientists TEST PIT LOG PROPOSED RESIDENTIAL SHORT PLAT 5521 SE IQTH STREET RENTON, WASHINGTON JOB NO: G-2320 I DATE: 8/10/06 1 PLATE LOGGED BY: Kl TEST PIT NO. DATE EXCAVATED: TP-4 8/8/06 GROUND ELEV: 434' (+/-) DEPTH I' USCS SOIL DESCRIPTION SAMPLE No. Water % OTHER TESTS/ COMMENTS ML- Dark brown SILTY SAND to SANDY SILT, medium dense, damp, SM sand is predominantly fine grained, trace gravel and cobble. 1 l 13.5 2 3 SM Dark brown SILTY SAND, medium dense to dense, damp, sand is 2 13.1 somewhat graded, 20-25% fines, trace debris (FILL). BULK 4 SM Brown, as above. 3 14.8 B --------------------------------------------------------------- Mottled brown, olive, and gray SANDY SILT to SILTY SAND, damp, 4 22.2 MLI medium dense, minor black organics and oxide stain (SUSPECTED SM SM WEATHERED NATIVE SOIL). 7 ---- --------------------------------------------------- SM - Gray SILTY SAND with gravel and cobble, damp, dense, 201/.fincs (GLACIAL TILL). S I I.l 8 Bottom of test pit at 7.5 feet below ground surface. Fill to approximately 5.5 fed. No groundwater observed. 9 10 Group North-west, Inc. Geotechnical Engineers. Geologists, a EnW onmental Scientists TEST PIT LOG PROPOSED RESIDENTIAL, SHORT PLAT 5521 SE IOTA STREET RENTON, WASHINGTON JO13 NO: G-2320 1 DATE: 8/10/06 1 PLATE LOGGED BY: KI TEST PIT NO. DATE EXCAVATED: TP-5 8/8/06 GROUND ELEV: 432' (+/-) DEPTH USCS SOIL DESCRIPTION SAMPLE Water OTHER TESTS! tL No. % COMMENTS Strong brown SILTY SAND, loose to medium dense, dry to damp, SM 40%+ fines, sand is mostly fine and medium grained, minor gavel. I 9.l 2 3 2 10.6 SM Brown SILTY SAND with gravel, damp, medium dense, sand is BULK somewhat graded, 25% fines. 4 ----- - ---------------------------------------------------- SM- Gray -brown SILTY SAND, damp, dense, 10-15% fines, sand is mostly - SP fine and medium grained with some gravel and cobble (GLACIAL TILL.). 3 4.2 5 6 Bottom of test pit at 4.5 feet below ground surface. No groundwater observed. 7 8 9 10 [! Group Northwest, Inc. 4 Gootechnical Engineers, Geologists, h Environmental Scientists TEST PIT LOG PROPOSED RESH)ENTIAL SHORT PLAT 5521 SE 10TH STREET RENTON, WASIHNGTON JOB NO: G-2320 I DATE: 8/10/06 1 PLATE APPENDIX B GRAIN -SIZE DISTRIBUTION TEST RESULTS G-2320 GEO Group Northwest, Inc. DEv c rr of R NTON PLANNING SEP z 7 2007 PRELIMINARY RECEIVED TECHNICAL INFORMATION REPORT BRETZKE & ROGERS SHORT PLATS 5521 NE LOTH ST(BRETZKE) 5603 NE 10TI` ST(ROGERS) Renton, WA BY SITE DEVELOPMENT SERVICES 310 208th ST. SE BOTHELL 98012 425--481-9587 May 10, 2007 tlfa? D0 ASy 15182 'ONAL " EXPIRES Q TABLE OF CONTENTS Section Section Title Number Project Overview I Preliminary Conditions Summary 11 Offsite Analysis III Detention Design & Water Quality Design IV Conveyance systems Analysis and Design V Special Reports and Studies VI(See Appendices) Other Permits VII(not used) Erosion/Sedimentation Control Design VIII Bond Quantities and Other Forms IX(to be completed) Maintenance & Operations Manual X(to be completed) Appendix A: Wetland Analysis Appendix B: Geotechnicai Report SECTION I PROJECT OVERVIEW PROJECT OVERVIEW This report is submitted for two short plats. The first is four lots for Daniel Bretzke at 5521 NE 10t" St., and the second is three lots for Larry Rogers at -5603-NE 10t" St. Both sites consist of single residential family-houses'With a number of outbuildings. The houses are to remain; however, all outbuildings except the garage on the Rogers site outbuildings will be removed. The entire development area and much of the proposed buffer has been cleared and landscaped or used for livestock in the past. The developments will share a private roadway access easement, although at least two of the lots will access directly to 10" St. Although two additional parcels to the west of the Bretzke short plat are included in the construction documents, they are not part of the subdivision. Frontage improvements in 100 St. are not required for those lots, but they will be done in order to create a continuity of the walks and pavement constructed for the Plat of Wedgewood Lane to the west. The staff has determined that the new impervious area in front of those parcels can be excluded from the threshold determination for flow control. Due to the presence of wetlands on the Bretzke site, a report and buffer averaging analysis were performed by Gerger/Abam Engineers. The resulting buffer limits are shown on the construction documents submitted with this report. The drainage calculations exclude the buffer and wetlands from the development area. In accordance with directions from the City staff, the requirement for detention was evaluated using the 1990 King County Surface Water Design Manual. It is shown in this report that detention is not required, as the increase in runoff is under 0.5cfs. This exemption is defined in the subject Manual on page 1..2.3-5. Runoff control BMP's will be applied to each lot through the use of dispersion trenches, as the geotechnical report completed for the project determined that the soils are not suitable for infiltration. Water quality was not required under the PGIS area increase exemption. The post -developed site will have 8,594 square feet of new PGIS from all roadway improvements. This excludes driveway area, as that will be dispersed or allowed to sheet flow to the wetlands. Of the new impervious area, 4,524 square feet will be on the Bretzke site and 4,070 square feet on the Rogers site. The existing PGIS on the pre -developed site consists of 3,790-square feet -on -the -Bretzke-site and 3,256 square feet on the Rogers site, for a total of 7,046 square feet. Therefore, the increase in PGIS is 1,548 square feet. m LU V) OPT w 12TH ST SE ST 112T� ST 6L 1 REP N VITH ST HAZZEN ------------- HS c CIA w a. 1 CITH Ept �F!to NTH ST N ST NE DTH SE 118T,6j 9TH PL NE qTH i'STHE 9TH ST � NE T LO NE 7TH p TH x e F- '0 00 _SE 12 IST ST -A IE 7TH 2 D ILI 1?2ND 2 ST is ST r-4 OD 10 tn VICINITY MAP. G. YA . La.. GOb SE 111T St !12'hi ST SE SE H2nJ Pi 5, uj at;4 113TIl ST SE 114TI1, a iE f�,l :5 tl W,�+ SE 117TH V 118TH ST t PROPERTY INFORMATION BRETZKE ROGERS SITE ADDRESS: 5521 NE -,10TH ST 5603 NE `?`BOTH ST TAX PARCEL Acount No.: 1023059358 1023059357 TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND PROJECT ENGINEER Project Owner Daniel Bretzke Address 1313 TT Ave South Phone 206 310 2190 Project Engineer David Dougherty Company: Site Development Services Address/Phone 310 208' St. SE, Bothell, WA, 98012 425-481-9687 Part 3 TYPE OF PERMIT APPLICATION ❑ Subdivison X Short Subdivision ❑ Grading ❑ Commercial Part 2 PROJECT LOCATION AND DESCRIPTION Project Name Bretzke Short Plat Location 5521 NE 10t' Street Township 23 Range 5E ...NE%, Section 10 I Part 4 OTHER REVIEWS AND PERMITS ! ❑ DFW HPA ❑ COE 404 0 DOE Dam Safety ❑ FEMA Floodplain ❑ COE Wetlands Part 5 SITE COMMUNITY AND DRAINAGE BASIN Community : Renton Drainage Basin : May Creek, _ Honey Creek Sub basin Part 6 SITE CHARACTERISTICS ❑ River ❑ Stream ❑ Critical Stream Reach ❑ Depressions/Swales ❑ Lake ❑ Steep Slopes Part 7 SOILS ❑ Shoreline X Rockery ❑ Structural Vaults ❑ Other ❑ Floodplain X Wetlands ❑ Seeps/Springs ❑ High Groundwater Table ❑ Groundwater Recharge ❑ Other Soil Type Slopes Erosion Potential Erosive Velocities Alderwood 5% to 35% Moderate Low Part 8 DEVELOPMENT LIMITATIONS REFERENCE Downstream Analysis ❑ 30' 36" culvert under NE10th ❑ Honey creels Stream channel ❑ 30' 36" culvert under Hoquiam Ave NE ❑ Honey Creek Channel Part-9 ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION XSedimentation Facilities X Stabilized Construction Entrance X Perimeter Runoff Control ❑ Clearing and Grading Restrictions XCover Practices XConstruction Sequence ❑ Other LIMITATION/SITE CONSTRAINT MINIMUM ESC REQUIREMENTS AFTER CONSTRUCTION ❑ Stabilize Exposed Surface ❑ Remove and Restore Temporary ESC Facilities ❑ Clean and Remove All Silt and Debris ❑ Ensure Operation of Permanent Facilities ❑ Flag Limits of SAO and open space preservation areas ❑ Other Part 10 SURFACE WATER SYSTEM Grass Lined ❑ Tank Channel ❑ Vault X Pipe System ❑ Energy Dissapator ❑ X Wetland Open Channel El Stream ❑ Dry Pond ❑ Wet Pond ❑ Infiltration Method of Analysis X Dispersion SBUH XFlow Dispersal Compensation/Mitigati ❑ Waiver on of Eliminated Site El Regional Storage Detention Brief Description of System Operation: On site dispersion of each house with individual on site dispersion systems. Access road to be dispersed into 50' trench next to wetland buffer. Facility Related Site Limitations Reference Facility Limitation On Site dispersion trenches I Part 11 STRUCTURAL ANALYSIS 1 ❑ Cast in Place Vault ❑ Retaining Wall XRockery > 4' High ❑ Structural on Steep Slope Other Part 12 EASEMENTS/TRACTS X Access Easement X Native Growth Protection Easement ❑ Tract ❑ other Part 13 SIGNATURE OF PROFESSIONAL ENGINEER I or a civil engineer under my supervision my supervision have visited the site. Actual site conditions as observed were incorporated into this worksheet and the attachments. To the best of my knowledge the information provided here is accurate. Signed/Date i'� • I I t �� 1 - fr 'r3 Y -C �µ r L. l !Y t - .� { `k � E _ 3. r. y _.' i� 7.7r�r���l�� �t'f •A�. �"".��``y i_, r r�, ICr � �t���(5_r� r Ad el cv mill of MG lk '•51 - 1 - .'� .�YI� { 114f 9i {�y`t U !• � s, s,� IImo�! Ar ! �, S � �' i i4 ^ y .+s � _ � '±3}� _ � f1 l ��' I �l . 1+ • e j � �y` � ,4 •T .+ J .w w .,.. � 3+- ht SOIL CONSERVATION SERVICE KING COUNT Solt. LEGEND The first capital letter is the initial one of the soii name. A second'capiial letter, A, B, C, D, E, or F, indicates the class of slope, Symbols without o slope letter are those of nearly level soils. SYMBOL NAME AgB Afderwaod gravelly sandy loom, 0 to 6 percent slopes t-q- AgC Alderwood gravelly sandy foam, 6 to t5 percent slopes �..�.1p. AgD Alderwood gravelly sandy loom, 15 to 30 percent slopes AkF Alderwood and Kitsap soils, very steep AmB Arenrs, Alderwood materiol,0 to 6 percent slops+ AmC Arenrs, Alderwood motsriof, 6 to IS percent slopes An Arenrs, Everett materials BeC Beousite gravelly sandy loam, 6 to 15 percent slopes B.D Beousite gravelly sandy loam, 15 ra 30 percent slap., BeF Beausire gravelly sandy loam, 40 to 75 percent slopes Bh Bellingham silt loam 13r Briscot silt loom B. Buckley silt foam Cb Coastal Beaches Ea Earlmont silt loam Ed Edgewick fine sandy loam EvB Everett gravelly sandy loam, 0 to 5 percent slopes EvC Everett gravelly sandy loam, 5 to 15 percent slopes EvD Everett gravelly sandy loom, 15 to 30 percent slopes EwC Everett-Alderwood gravelly sandy loamy, 6 to 15 percent slopes InA Indianola loamy fine sand, 0 to 4 percent slopes InC Indianola loamy fine land, 4 to 15 percent slopes InD Indianola loamy fine sand, 15 to 30 percent slopes KPB Kitsap silt loam, 2 to 9 percent slopes KpC Kirsop silt loam, B to 15 percent slopes KpD Kitsap silt loam, 15 to 30 percent slopes KsC Klaus gravelly loamy Bond, 6 to 15 percent slopes Nta Mixed alluvial land NeC Neilfon very gravelly loamy sand, 2 to 15 percent slopes Ng Newberg silt loam Nk Nooksack silt loam No Normo sandy loam Or Orcas peat Os Oridio silt loam OvC Ovall gravelly loam, 0 to 15 percent slopes QvD Ovoll gravelly loam, 15 to 25 percent slopes OvF Ovall gravelly loom, 40 to 75 percent slopes Pc Pilchuck loamy fine sand Pk Pilchuck fine sandy foam Pu Puget Billy cloy loam Py Puyallup fine sandy loam RaC Rognor fine sandy loam, 6 to 15 percent slopes RaD Ragoar fine sandy loom, 15 to 25 percent slopes RdC Ragner-Indianola association, sloping+ RdE Ragnar•Indionolo assoclaticn, moderately steep • Re Renton silt loam Rh Riverwash So Solal silt loom Sh Snomomish silt loam Sk Sea rtI& muck Sm Sholcar muck Sn Si silt loam So Snohomish sill loam Sr Snohomish sill loam, thick surface variant Su Sultan silt loam Tu Tukwila muck Ur Urban land Wo Woodinville sill loam • The composition of these units is more variable than that of the others in the area, but it has been controlled well enough to interpret for the expected use of she soils. SECTION If PRELIMINARY CONDITIONS SUMMARY PRELIMINARY CONDITIONS SUMMARY This section only includes Core and Special Requirements, as no conditions of approval have been issued for the subject projects. Summary of City of Renton Pre application notes 1. Sanitary sewer is required. It is not in an Aquifer Protection Zone, 2. Water is served by WD 90. Water main improvements need to be approved by City of Renton. 3. Project is in Honey Creek Drainage basin. Conceptual drainage plan and report are to be submitted with application for short plat. Drainage plan first to be designed to the 1990 King County Surface Water Design Manual to determine if detention is required. If detention is required then it shall be designed per the 2005 KCSWDM. 4. Street improvements to include curb gutter and 5 sidewalks. Curb to be located 16 feet from center line. Private streets to be located in a 26 feet wide tract, with 20 feet paving, and include a fire department turn around. 5. All new power, telecommunications to be placed under ground. CORE REQUIREMENTS Per the drafting standards revised May 2000 the Core requirements 1-5 in section 1.2 are to be addressed, and all special requirements in 1.3 that are applicable to this project are to be addressed. Core Requirement #1: Discharge at the !Natural Location. The current storm water sheet flows from exiting impervious surfaces and the existing pastures to an on site wetland. The proposed storm water management plan -proposes to use dispersion trenches on each individual property to disperse storm water in the same manner. Core Requirement #2: Off site analysis. All the surface water from this plat drains to the wetland on the property. The wetland Is drained by-Honey*Creek, which is a1ributary-to-May creek. This project is adjacent to the recent plat of Wedgewood, which has recently extended the culvert crossing under NE 10th street. A review of the downstream system indicates stream conveyance across private property. The -next -culvert crossing in public right of way is located over a '/ mile to the north under Hoquium Ave NE. There does not appear to be any down stream problems with in % mile of this project. Core Requirement #3: Run off Control In accordance with directions from the City staff, the requirement for detention was evaluated using the 1990 King County Surface Water Design Manual. It is shown in Section IV of this report that detention is not required, as the increase in runoff is under 0.5cfs. This exemption is defined in the subject Manual on page 1.2.3-5. Runoff control BMP's will be applied to each lot through the use of dispersion trenches, as the geotechnical report completed for the project determined that the soils are not suitable for infiltration. Core Requirement #4: Conveyance System. Downspout Dispersion systems. Appendix C, Section C2.4.4, of the 2005 KCSWDM provides that basic dispersion is allowed for single family lots with less than 22,000 square feet and full infiltration or dispersion is not possible. The conditions are that the flowpath be over at least 25 feet of vegetative coverage at a maximum slope of 15% before leaving the property and does not pose a significant flood or erosion problem." In order to accomplish this, some of the dispersion systems will have to be in easement areas that will provide for the preservation of the flowpath over adjacent lots in the plat. In addition, to avoid flowing over slopes exceeding 15%, some of the trenches had to be at the toe of the slopes in the wetland buffer, which also coincided with the edge of the wetland. Runoff from the plat roadway and Lot 1 of the Rogers Short Plat had to be conveyed to the base of the slope in the buffer as described above. This was designed as an outfall condition in accordance with Section 4.2.2 of the 2005 KCSWDM. The calculation of the runoff to allow the use of this system is found in Section V. Core Requirement #5, Temporary Erosion and Sedimentation Control (TESC): Soils in this project have a high silt content and are moderately sensitive to erosion. Also, work involves significant soils movement due to steep grades. However, the size of the development area is about 1.73 acres, so normal TESC BMP's will be applied for this project. This will include perimeter protection using silt fences, a quarry spall construction entrance, ground cover practices, and the use of a sediment pond. Core Requirement #6: Maintenance and Operation Maintenance of the plat access road is to be performed jointly by all lot owners in the two subdivisions_ An agreement has been recorded with lot line adjustment, which was recently completed. All off site improvements are to be completed under a right of way use permit from City of Renton. All storm drain maintenance will consist of catch basin and pipe cleaning as specified in Section X. SPECIAL REQUIREMENTS Other Adopted Area -Specific R uirements: No such areas are known to affect this site. Floodolain/Floodway Delineation: The site contains a wetland and is adjacent to a drainage ditch. The mitigation and restoration requirements for the wetland and buffer are being provided by Berger/Abam Engineers, Inc in a report attached as Appendix A. Flood Protection Facilities: The site is not adjacent to a Class 1 or 2 stream, nor does is propose to construct a new or modify and existing flood protection facility. Source Controls: No special controls should be required for the site, as it is a single family residential development. Oil Control: This is not a high use site, nor is it redeveloping an existing high use site. Therefore, special oil control measures are not required. SECTION III OFFSITE ANALYSIS OFF -SITE ANALYSIS UPSTREAM: The upstream area consists of the adjacent parcels to the east, which are single family residential lots. Runoff from those sites sheet flows across the southeasterly corner of the project site. No signs of concentrated runoff were found entering the site. ON -SITE: The project site is occupied by two single family residences and several outbuildings. Much of the southwest portion of the site is a forested wetlands. The area up to the wetlands and the slope leading down to it has been cleared and landscaped (Photo 1A). Some of it was used for the horses, so there is a corral and barn on the site. No sources of runoff, closed depressions or other drainage features were observed outside of the wetland area. Most of the runoff from the site sheet flows to the southwest into the wetland; however, some flows into a drainage flue to the south of the site. DOWNSTREAM: Both the wetlands and the drainage ditch mentioned above drain to the west into Honey Creek (Photo 1 B). The creek crosses 101h St. in a new 36 inch culvert that reduces to the existing 24 inch culvert before exiting on the north side of the road(Photos 2A & 2B). This system was installed by the new plat adjacent to the west called Wedgewood Lane. From there the runoff enters a vegetated channel. The channel area immediately downstream of the outfall is landscaped, but is forested beyond that (Photo 213). This channel and the surrounding forested condition continue to a point over '/a mile downstream, so the reconnaissance ended there. iti�� ' 1p—jj A S� 535 T' �ti � 1 O mil•`-i �' a vJ S t! M 43 (ixb~ a 3s 3rlY RUMci tmo t 4 a M m M7 W a 3N-OOOVM's n r � D ♦ b ti h f'r% kn Ri' y rn A^.F ' Irk ,�� I� � •� ;,�j J •. �,�'�'t i { i. 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J ti s +l )i t'' Y r i f t w s4D461 ,f ^ 1 : i- ri - '� u-�•saw'•�`..� ' r .;'� .., r '{ J� ',f,�.., �!� .,. �, iiF�k"5�" C.'� f 'oaf '. e�•` 4 ,; .\Y r q+ � r•,�� ', r� t Y�3 '1l-` '� t a fit_ yy •1; + �+ .{- C'� r ti y � �J � �d� t i� • ' `' - l.Y• . r .•"�,i"�yi,��� �"•r«� x °' i-J!� �"l._1 ti.j�-yJ + .:.1 q y' rt !!x'';. Yv, •� A`-U � t- S 7 tY 5 Jf kn ry S�. � � r ft ! 'f i ��,�`11!,' .F �y� �f�rv�,�:' �` "�, sr�;�(sc FTti 7.; ;••rr4 Er ?rr ,'� Tsl'�, I• r� f � r rr �` � �r ry� r ,IYl1�•• ' .r ' ! ail xl r� E ✓A 5 , ir A r . r A fit•. � h "1—u f'� 3 ice„ r h'ra:r 1; SECTION IV DETENTION & WATER QUALITY ANALYSIS DETENTION ANALYSIS The enclosed calculations show the increase in runoff from the pre -developed to the post -developed site conditions. In accordance with the requirements of the 1992 KCSWDM, the Santa Barbara Urban Hydrograph method was used. The increase in the 100 year event was found to be 0.24cfs. Because this is below 0.5cfs, detention is not required. ul W ui J uj u EO 0 cl ©o 04 � r [i NN NNCV ry� I Ul-i r�� fi I 1 S 'ff" �.. +6+� � i • s..'-�'. �� '� �^ a-�., � [."^'. 7; � i. S_/ � • ' �` S+�- � °f"L•. � (,.e..} •@, �T" �%. � C'"/ vp Ir tiGf rC%C) g '�.. lam {^•. �• 1."t 44" .0. Vt(� �'A VA-1- Reams~ 0.7 7 f Li ra rr 1C r ! I I �L:����-�:.�� ��: J I i I pvl�e 1� 12 It Cf , , �' t V c tag ►` vR ake- _, t Irk 10 1. -7J fge- - DI -;-71ge- � 1. 4o qG �Lti�tT�1 R`�?�� •, 4 As ra�(s I i 7Z � (9 . 76)� r 3 Z vpp .0 %ry 0 el! So 0 -e LIS4 rl " L,L.,. I or 1.00.9 sA 4pc( IP '4 Im 1 2*7 Z�4e�rv-c,3e, = Op Z 4 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TABLE 3.5.2B SCS1yESTERN WASHINGTON RUNOFF CURVE NUMBERS SCS WESTERN WASHINGTON RUNOFF CURVE NUMBERS (Published by SCS in 1982) Runoff curve numbers for selected agricultural, suburban and urban land use for Type 1A rainfall distribution, 24-hour storm duration. CURVE NUMBERS BY HYDROLOGIC SOIL GROUP LAND USE DESCRIPTION A B C D Cultivated land(1): winter condition 86 91 94 95 Mountain open areas: low growing brush and grasslands 74 82 89 92 Meadow or pasture: 65 78 85. 89 Wood or forest land: undisturbed or older second growth 42 64 76 81 Wood or forest land: young second growth or brush 55 72 81 86 Orchard: with cover crop 81 88. 92 94 Open spaces, lawns, parks, golf courses, cemeteries, landscaping. good condition: grass cover on 75% or more of the area 68 80 (86 i 90 fair condition: grass cover on 50% �� to 75% of the area 77 85 90 92 Gravel roads and parking lots 76 85 89 91 Dirt roads and parking lots 72 82 87 89 Impervious surfaces, pavement, roofs, etc. 98 98 9 98 Open water bodies: lakes, wetlands, ponds, etc. too 100 0o too Single Family Residential (2) Dwelling Unit/Gross Acre % Impervious (3) 1.0 DU/GA 15 Separate curve number 1.5 DU/GA 20 shall be selected 2.0 DU/GA 25 for pervious and 2.5 DU/GA 30 impervious portion 3.0 DU/GA 34 of the site or basin 3.5 DU/GA 38 4.0 DU/GA 42 4.5 DU/GA 46 5.0 DU/GA 48 5.5 DU/GA 50 6.0 DU/GA 52 6.5 DU/GA 54 7.0 DU/GA 56 Planned unit developments, % impervious condominiums, apartments, must be computed . commercial business and industrial areas. (1) For a more detailed description of agricultural land use curve numbers refer to Nationat Engineering Handbook, Section 4, Hydrology, Chapter 9, August 1972. (2) Assumes roof and driveway runoff is directed into street/storm system. (3) The remaining pervious areas (lawn) are considered to be in good condition for these curve numbers. j 3.5.2-3 11192 POSTDEVELOPED RUNOFF ROUTE: 101LF @ 23.37(GRASS) 35LF ® 10%(ASPHALT) 37LF ® 5.47o(GRASS) ' R �----�^,��r-ArF.-fv.N..�y -. i, :- Y-�..-_ - -- �_. .'4_. • .r _ - _ter.:_- � __. a.... _ _..-_ - l� �� -!". y�-�- S_IIE l�gli Si •�-• i. 5:_ .�t�� .�, ��.._...:F"`;, �'r I�� •a-�. " --- ..� f fM..4 h'3P. - '�•. WHIR FF.R �' � � + V t :: � ` � r � •� , ' k 3 '' . r -.,y.. r�rr.. t'_..- _ _ y •_.� v ' • ��te + ft, '7 -r � _ ..! yf . .•.. _Y - _ �E �� ' ,,• ,,.. - _M• l a,y -uw it +� a .l,f_ ..tl 1 ,.:� �� —- •.— •. �r ,'� �' ,� �- —.'•� PREl7EVLOPE ,,RUNOFF ROUTE: _ ., ------- ir240' „ ;aat ,, w., SLOPE=16.2� �` + • ' f' .. r ice...., - - - .. - . �rrr�e�4rrrirr�:r�rr�r ..M1-,�;�'} I -3�•c •r MAXIMUM RUNOFF ROUTES. BASIN DATA AND RUNOFF CALCULATION b-r pre Event Summary: BasinlD Peak Q Peak T ------ (cfs) (hrs) b-r pre 1.03 8.00 Drainage Area: b-r pre Hyd Method: SBUH Hyd Peak Factor: 484.00 Storm Dur: 24.00 hrs Area Pervious 1.4000 ac Impervious 0.3300 ac Total 1.7300 ac Supporting Data: Pervious CN Data: pervious area Impervious CN Data: Impervious areas Pervious TC Data: Flow type: Description: Sheet Runoff Impervious TC Data: Flow type: Description: Fixed Impervious b-r pos Event Summary: BasinID rea-k Q Peak T s) (hrs) b-r pos 7 8.00 Drainage Area: b-r pos Hyd Method: SBUH Hyd Peak Factor: 484.00 Storm Dur: 24.00 hrs Area Pervious 1.0500 ac Impervious 0.6800 ac Total I.7300 ac Supporting Data: Pervious CN Data: pervious area Impervious CN Data: Impervious areas Pervious TC Data: Flow type: Description: Sheet Upper segment Sheet Last segment Impervious TC Data: Flow type: Description: Sheet Impervious Pv-.p d g,4 r (T'd Peak Vol Area Method Raintype Event (ac ft) ac ILoss 0.4006 1.73 SBUH/SCS TYPEIA 100 yr Loss Method: SCS CN Number SCS Abs: 0.20 Intv: 10.00 min CN TC 86.00 0.26 hrs 98.00 0.01 hrs 86.00 1.4000 ac 98.00 0.3300 ac Length: Slope: Coeff: Travel Time 240.00 ft 16.20% 0.2400 15.37 min Length: Slope: rr 0.00ft r0.00% 1,90 54ct 'e q a r r o(J e d Peale Vol Area Method (ac-ft) ac /Loss 0.4361 1.73 SBUHISCS Coeff: Travel Time 0.3000 0.30 min Raintype Event TYPI 1 A 100 yr Loss Method: SCS CN Number SCS Abs: 0.20 Intv: 10.00 min CN TC 86.00 3.66 hrs 98.00 0.01 hrs 86.00 1.0500 ac 98.00 0.6800 ac Length: Slope: Coeff: Travel Time 101.00 ft 23.30% 0.2400 6.65 min - 37.00 ft 5.40% 0.2400 2.45 min Length: Slope: Coeff: Travel Time 35.00 ft 10.00% 0.0100 0.31 min SECTION V CONVEYANCE ANALYSIS CONVEYANCE SYSTEM ANALYSIS Due to the small size of the site a detailed conveyance analysis is not required. The 100 year runoff for the entire as calculated for the detention exemption was 1.27cfs. The capacity of a 12 inch storm drain pipe @ a slope of 0.5% (the pipe on this site are all steeper) is 2.6cfs. Thus, no pipe in the system will be at capacity, and no backwater analysis is required. Included in this section is the calculation for the flow from the roadway storm drain. The results show that the flow is over 0.2cfs, but under 0.5cfs, so a dispersion trench is appropriate. �l1 �11 ' 1l: IIMAIAMMIM King County Runoff Time Series Program Version 4.42d All files will be read/written in the Working Directory Working Directory:C.\KC_SVDK KCRTS Command CREATE a new Time Series Production of Runoff Time Series Project Location Landsburg Computing Series PLAT RDWY.tsf Regional Scale Factor 0.80 Data Type Reduced Creating IS -minute Time; Series File Loading Time Series File:C:\KC SWDX\KC_DATA\LAEIiSR.rnf Impervious 0.19 acres Scaling Yr: 8 Total Area 0.19 acres Peak Discharge:_ 0.228 CFS at 7:30 on Jan 9 in Year 8 Storing Time Series File:PLAT RDWY.tsf Time Series Computed 9 8 p,,*W SECTION 3.2 RUNOFFCOMFUFATION AND ANALYSIS MM'HODS ST 1.1 ST 1.1 FIGURE 3.2.2.A RAINFALL, REGIONS AND REGIONAL SCALE FACTORS ST 1.0 ST 1.0/ ST 1.0 LA 0.8 LA p.9 LA 1.0 LA 1.2 "ISH COUNTY LN OM OI(ING DOpM " It CO-.F . lea, r i ,LA111Y2 Y1� � • id7 T I ! 1 OKI r� �fY' - • _ f. Leo eft y qfs �p 1 i �b •t' r 0 _ Rainfall Regions and Regional Scale Factors irk:[ Incorporated Area —c=s River/Lake Major Road rtr7 I�x�y;r�a #� �•� s� ,,� roc �.'� Jj�'= 't��1� v s d'r,���Mg01 5rlr ' � . A "� �•�.3: `! slt3 �` �,'`r -'� , •t fir' z-+r a , ✓�� ? � i. LANDSBV R.G s �r A,. ` `Z. ..-�'t.rt ' i _ / fir' •�^GR �Sr ` t'a f 5 �� f � ,F ! � S �fs j�l � . 3 ��A�• A Q �� e f T� /11U we taulfr.T' r ST 1.01 i• i� ,,W-; LA 0.8 LA0.9�� LAi.2 LA 1.0 9/1/98 1998 Surface Water (Design Manual 3-22 -- -- ----- -- -- -- SECTION VIII EROSION/SEDIMENTATION CONTROL DESIGN EROSIONISEDIMENTATION CONTROL DESIGN Size the sediment trap: Compute design flow, which is the 2 year, post -developed storm with a 15 minute time step: KCRTS Command CREATE a nev Time Series Production of Runoff Time Series Project Location : Landsburg Computing Series b-rconstr.tsf Regional Scale Factor 0.80 Data Type Reduced Creating 15-minute Time Series File Loading Time Series File:C:\KC SODN\KC DATA\LATG15R.rnf 8 Till Grass 1.05 acres Scaling Yr: 8 Loading Time Series File:C:\KC-SWDM\KC-DATA\LAEI15R.rnf 8 Impervious 0.68 acres Adding Yr: 8 Total Area 1.73 acres Peak Discharge: 1.38 CFS at 7:30 on Jan 9 in Year 8 Storing Time Series File:b-rconstr_tsf 8 Time Series Computed Flov Frequency Analysis Time Series File:b-rconstr.tsf Project Location:Landsburg ---Annual Peak Flov Rates --- Flow Rate Rank Time of Peak (CFS) 0.390 7 2108101 19:00 0.349 8 5/06/02 7:15 0.723 4 9/10/03 13:45 0.927 2 8/25/04 23:30 0.513 6 9/10/05 16:45 0.859 3 10/22/05 16:15 0.610 5 11/21/06 9:00 1.38 1 1/09/08 7:30 :omputed Peaks Flow Frequency Analysis - - Peaks - - Rank Return Prob (CFS) Period 1.30 1 100.00 0.990 0.927 2 25.00 0.960 0.859 3 10.00 0.900 0.723 4 5.00 0.800 0.610 5 3.00 0.667 0.513 6 2.00 0.500 0.390 7 1.30 0.231 0.349 8 1.10 0.091 1.23 50.00 0.980 This shows that the two year storm has a flow of 0.51cfs. Using the surface area (SA) for the pond from page D.3.5.1 from the Manual: SA = 2080 (0.51) = 1061 square feet This area is measured at the invert of the weir. APPENDIX A WETLAND REPORT