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HomeMy WebLinkAboutGRD2007-00020 Stormwater Grading Plan - GRD Engineering / Geo-Tech Reports - 8/8/2008 MASON COUNTY PUBLIC WORKS DIRECTOR/COUNTY ROAD ENGINEER Shelton, Washington 98584 DATE: August 8, 2008 INTER-DEPARTMENTAL COMMUNICATIONS TO: Al Christensen Jim Scholz & Barb Robinson PARCEL # 12321-14-00041 Pages 3 FROM: John Sliva, Programs Engineer-PW PERMIT NUMBER: GRD2007-00020 SUBJECT: Stormwater/ Grading Plan NAME: Earl Iddings/Brad Shaurer Barb, Al, and Jim: The grading plan proposes the development of two plateaus that will create approximately nine acres of impervious surface area. The easterly plateau will slope at approximately 2% until it drops at a 2:1 slope for 17 feet to the next plateau to the west. The westerly plateau will drop off at a 2:1 slope to a water quality pond and an infiltration pond. The ponds will have 2:1 slopes. The water quality pond will have 3:1 slopes in the lower portion. Pond grading will start before site grading. Material placement densities are noted on the drawings. Structural Fill will be compacted at 95% maximum density. A liner will be installed in the lower portion of the water quality pond. The Temporary Erosion Sediment Control Plans are acceptable. On October 24, 2007 a meeting was held with Bill Tabor(PW), Bob Thuring (PW), John Sliva (PW), Earl Iddings and Kent Rasmussen of (Dewatto Bay Development), and Scott Muern PE (KPFF Engineering) in regards to this development. The main topic was the development must have no negative impacts downstream due to the closed basin. An IDC letter was send out on November 8, 2007 with regards to the meeting. The first condition from the letter is: 1. Must show that no negative impacts down stream will result from the proposal. The depression will be eliminated by the proposal. All of the current drainage areas feeding the depression will be analyzed. The Stormwater facility will be designed to provide the equivalent retention storage of the depression that existed prior to the construction of the new retention/detention pond as well as accommodate the proposed development. We reiterate that the stormwater facility must be redesigned and calculations submitted to show that there will be no negative impacts downstream from the newly designed Stormwater Facility. On December 21 , 2007 Public Works received an updated stormwater plan for the proposed site. The stormwater plan is complex. Two new ponds are to be located in a closed depression that handles runoff for a large portion of the Logyard Road Basin. Some of the runoff is directed to this area from as faraway as a pond on the east side of State Route 3 in Kitsap County. Public Works concern is that the stormwater facility be designed with calculations submitted to show that there be no negative impacts downstream from the new stormwater features. It is known that the area downstream does flood at times in the winter. This stormwater proposal was delivered to Department of Community Development to be sent to an outside consultant. The review is at the expense of the applicant. This was done on December 31 , 2007. The reviewer is Vector Engineering of Olympia. Russell LaForce, PE of Vector Engineering of Olympia, WA performed the review working closely with Scott Muern, PE of KPFF Engineering, the applicants engineering firm. Technical information was exchanged several times between January 11, 2008 through August 6, 2008. On August 6, 2008, Mr. LaForce responded with a letter titled the Storm Drainage Technical Information Report. Under Conclusions and Recommendations, Mr. LaForce notes, "the report was prepared by a qualified licensed professional engineer and does provide sufficient information to determine the proposed commercial/industrial development will not increase flooding. It is recommended that the storm drainage technical information report be accepted. No further review by Vector Engineering is necessary". The August 6, 2008 letter from Vector along with the correspondence, documents, and drawings that were exchanged between engineers appears to address the conditions of the letter of November 8, 2007. In my review of the final drawings I noted that the culvert from Katchemak Lane that dumps into the depression was not addressed. Both engineers, Mr. LaForce and Mr. Muern were contacted on August 7, 2008 on this issue. They both independently concurred that there is very little impact from this culvert and there is not an issue. The Stormwater Site Plan and Grading Plan will be considered acceptable by Public Works based on the information provided and recommendations of the outside reviewer, Vector Engineering, if the applicant will accept the following conditions: 1 . A Declaration of Covenants Associated with Privately Maintained Storm Drainage Facilities (Operations and Maintenance Agreement) is recorded. A copy of the Operations and Maintenance Agreement shall be provided to Planning and Public Works before grading starts. 2. Engineer of record shall document the stormwater facilities were built to the drainage plan and drawings and note any changes upon completion of the stormwater facilities. This documentation shall be provided to the County for final acceptance of the completed stormwater facilities. 3. Part of the pond is in parcel 12321-75-00010. An easement is needed for that portion of the parcel that will have the stormwater features prior to grading. 4. PE Stamped final drawings will be provided in lieu of PDF's prior to grading commencing. Comments and recommendations contained in the report should be incorporated into the site development plans and made conditions for permit issuance. Adequate erosion and sediment control features need to be implemented during land disturbing activities to protect neighboring properties and State waters from adverse stormwater runoff impacts. The migration or release of silty water or mud from the applicant's property will be considered a violation of County and State water quality protection regulations. Please feel free to contact me at 724 if there are any questions. Si rely, John Sliva Programs Engineer iZ3z � i � o � �t f Form Effective June 2008 TO BE KEPT IN THE Mason County Department of Comm up4 i�1q ftFnt Submittal Checklist For a Geological Assessment Instructions: This checklist must be submitted with a Geological Assessment and completed, signed, and stamped by the licensed professional(s) who prepared the Geological Assessment for review by Mason County pursuant to the Mason County Resource Ordinance. If an item found to be not applicable, the report should explain the basis for the conclusion. Applicant/Owner: EARL IDDINGS Parcel # 123211400041 Site Address NE LOG YARD RD&NE STATE Hwy 3 BELFAIR,WASHINGTON 985828 (1) A discussion of geologic conditions in the general vicinity of the proposed development, with geologic unit designation based on referenced maps. _ E Located on page RCEIVIE s) 6 r ( ,ALIC; 12 (2) (a) A discussion of the ground water conditions at the site, MCCG PLANNING Located on page(s) 7 - (b) A discussion of the estimated depth to water Located on page(s) 7 (c) A discussion of the quantity of surface seepage Located on page(s) NONE OBSERVED (d) A discussion of the upslope geomorphology Located on page(s) 5 (e) A discussion of location of upland water bodies and wetlands. Located on page(s) 7 Form Effective June 2008 (3) The approximate depth to hard or dense competent soil, e.g. glacial till or outwash sand. Located on page(s) 7 (4) A discussion of any geomorphic expression of past slope instability (presence of hummocky ground or ground cracks, terraced topography indicative of landslide block movement, bowed or arched trees indicating down slope movement, etc.) Located on page(s) 7 (5) A discussion of the history of landslide activity in the vicinity, as available in referenced maps and records. Located on page(s) 7 (6) An opinion on whether the proposed development is within the landslide hazard area or its associated buffer or setback and the potential for landslide activity at the site in light of the proposed development. Located on page(s) 7 (7) A recommendation by the preparer whether a Geotechnical Report should be required to further evaluate site conditions and the proposed development of the subject property. Located on page(s) 8 (GEOTECHNICAL REPORT NOT REQUIRED) (8) If the presence of a hazard is determined within 300 feet of the proposed development, then the following are delineated on a geologic map/site map: (a) the area of the proposed development, Located on Map(s) NA (b) the boundaries of the landslide hazard area (top, both sides, and toe), Located on Map(s) NA (c) the associated buffers (top, both sides, and toe), Located on Map(s) NA (d) building or other setbacks (top, both side, and toe), Located on Map(s) NA Form Effective June 2008 (9) A site map drawn to scale showing the property boundaries, scale, north arrow, and the location and nature of existing and proposed development on this site. Located on Maps(s) PROVIDED WITH THE RECENT ADDENDUM LETTER I, Curtis D Cushman hereby certify under penalty of perjury that I am a civil engineer licensed in the State of Washington with specialized knowledge of geotechnical/geological engineering or a geologist or engineering geologist licensed in the State of Washington with special knowledge of the local conditions. I also certify that the Geological Assessment, dated and entitled meets all the requirements of the Mason County Resource Ordinance, Landslide Hazard Section, is complete and true, that the assessment demonstrates conclusively that the risks posed by the landslide hazard can be mitigated through the included geotechnical design recommendations, and that all hazards are mitigated in such a manner as to prevent harm to property and public health and safety. (Signature and Stamp) Wash�� � A# 2439 c+�'8ed Geo�o Disclaimer: MaspUtRfflgt6eAWVMA the quality of the work done in this Geological Assessment.