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HomeMy WebLinkAboutStormwater Management Issues for BLD2003-01134 - PLN General - 9/11/2003 TO BE KEPT IN THE MASON COUNTY PARCEL FILE PUBLIC WORKS DIRECTOR/COUNTY ROAD ENGINEER Shehon,Wuhington 98584 DATE: September 11`h, 2003 INTER-DEPARTMENTAL COMMUNICATIONS TO: Diane M-Jones, DCD - Planner FROM: Alan A. Tahja,P/W- Co. Hydr. Engr. WO# PLG-03 SUBJ: Stormwater Management Issues NAME: Wilson 2 Stonebriar/Jensen Rd BLD2003-01134 Diane, Review of the materials you submitted to Public Works for review, and my conversations with Jerry Hauth,the County Engineer, shaped the following remarks. The immediate proposal to develop the property for residential use,will have, as any land disturbing activity will require, a need to control erosion and sediment during construction. Under Ecology's and the County's Stormwater Management regulations, grading for single family residences is exempt from permanent stormwater quality protection plans (engineered stormwater facilities), but is required to control and contain construction borne silt and erosion on the subject site. Typically, construction sites are required to limit their access to a single stabilized entrance during construction to act as a defense against silt and mud migration off the property. Mason County's stormwater management regulations require development, whether residential or commercial,to preserve natural drainage patterns and natural drainage routes. The report authored by The Coot Company indicates that fill material has been placed in a natural drainageway, and that some impact to the drainage has been accomplished in terms of natural drainage detention areas, and natural drainage/floodplain features. Removal of fill material from the drainage swale is recommended in the Coot Company report, and Public Works supports this recommendation. The material reviewed indicates that the Jensen Road has experienced flooding during past storm events. The road itself may be an accidental impediment to stormwater drainage through this area, but there does not appear to be a direct correlation between the development of the Wilson property and the construction or existing condition of the road. Flooding of the road suggests that drainage issues relating to the road have not been adequately addressed, and may need an engineer's investigation and analysis to determine whether it is an obstruction to the natural drainage in the area, and what remedy or revisions to the road and its culverts may be needed. File: H: \WP\Strmwtr\Reviews\Wilson-Stonebriar.doc The exempt status of single family residences and duplex, is interpreted by the County Engineer as only applying to single family residences and duplexes that do not create more than 5000 square feet of new imperviousness(rooftops, driveways,and other paved areas). To summarize my investigation, if the proposed residential development of the property creates less than 5000 of new imperviousness, an erosion and sediment control plan should be implemented during construction, and any erosion and sediment control features implemented during construction should be maintained until they are no longer needed. If the development of the property creates in excess of 5000 square feet of new impervious surfaces, an engineered stormwater plan may be requested to be developed. I hope this information assists you in disposing of this proposal's issues. Please feel free to contact me at County extension 461 if you have any questions regarding these comments,or if you feel any features need further discussion or attention. Since el , RL 7; -� Al n A. Tahja File: H: \WP\Strmwtr\Reviews\Wilson-Stonebriar.doc I �J 0.t�' Per our discussion last week regarding Bld. 2003- (Parcel number 32132-32-90114), Building staff conducted a site inspection on Friday August 29, 2003, in order to assess the soil compaction and fill of the proposed foundation of the subject property. Building staff determined that a foundation analysis and/or a geotechnical report would not be necessary for the proposed foundation. However, concerns regarding the stormwater drainage still remain. As mentioned in the Resource Lands and Critical Area Site Evaluation (RLC2001-00099), the stormwater swale on the subject parcel carries significant amounts of water during the rainy season. The evaluation continues, "evidence of inundation is present at the driveway entrance and eastern portions of the filled area." It is Planning staff s determination that prior to recommendation of approval of the proposed development, that the project be reviewed under the requirements of the Stormwater Management Ordinance (Mason County 141-97) and if necessary a stormwater site plan be required. Attached are the documents that support this determination and provide descriptive evidence of the stormwater drainage concerns on the subject property. Please advise planning staff, as to what may be required of the applicant per the Stormwater Management Ordinance regulations; in order to proceed with review of the building permit. Thank you for your assistance TO BE KEPT IN THE r= CEL FILE I ` Resource Lands & Critical Area Site Evaluation 10/3/01 Case No.: RLC2001-00099 Comments A field inspection of the subject property was conducted on 9/27/01 with the following results. The parcel is located in the Stonebriar subdivsion. It is characterized by extensive fill that was emplaced without a Mason County Grading Permit. The fill work was stopped by County enforcement action in March of 1998. In addition to the permitting issues, there was concern that the fill had encroached into a jurisdictional wetland. A subsequent analysis by The Coot Company determined that the area was a seasonal stormwater swale and did not meet the criteria for a wetland. County staff concurs with this assessment but notes that the area still experiences significant albeit brief periods of inundation. The fill was determined to be below the threshold required for a grading permit and the case was closed. There are still issues that affect further development of the parcel. The stormwater swale carries significant amounts of water during the winter rainy season. Evidence of inundation is present at the driveway entrance and eastern portions of the filled area. Residents of the area have noted that the culverts emplaced to carry this flow are, at times, inadequate and the roadway itself floods. Continued filling of the parcel may diminish the capacity of this swale and exacerbate flooding conditions. No additional fill may be placed on the parcel without a grading permit. In support of this permit, Mason County will require the applicant to provide engineering that demonstrates the fill will not increase flooding on the roadway and/or adjacent parcels. In addition, in concert with recommendations made in the wetland assessment, the County will require removal of some of the fill that currently displaces areas of the stormwater swale. Discussion included consideration of a more westerly driveway access and removal or modification of a large berm along the western property edge. Questions regarding driveway access should be directed to Terence Conley of the Mason County Public Works Department at (360) 427-9670 x456. Removal or modification of the berm will also require a grading permit if the material is to be redistributed onsite. The engineering requirements described above would also apply to this activity. If you have questions or require clarification regarding this determination, please contact me. 10/3/01 2 of 2 RLC2001-00099 MASON COUNTY RECEIVED DEPARTMENT OF COMMUNITY DEVELOPMENT r� Planning SE J 0 Mason County Bldg. 1 411 N.5th P.O.Box 279 Shelton,WA 98584 54N COUNTY PuBuc1NORKS (360) 427-9670 Belfair (360) 275-4467 Elma (360) 482-5 69 To: Allan Tahja, Public Works Department From: Diane M-Jones, DCD-Planner Re: Bld. 2003-01134 ?AA �c� — Date: Sept. 3, 2003 Please review the attached application and supporting documents with respect to the Mason County Stormwater Management Ordinance. Recommendations provided will be incorporated into the site's development. It was Building Department's determination that a geotechnical report for the foundation on the subject property was not necessary. Thanks for your assistance, Diane TO BE KEPT IN THE. PARCEL FILE