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Home My WebLink AboutCOM 0176.019 2006-2008 Murashige, Laura From: Nancy E. Burns [nebpellc@hawaii.rr.com] Sent: Monday, March 19, 2007 5:50 PM To: counciltestimony@co.hawaii.hi.us Subject: FW: Final Testimony Bill 51 Draft 2.pdf -Adobe Acrobat Professional Attachments: Final Testimony Bill 51 Draft 2 4 ~ , ~3 Final Testimony Bill ~ - ~ N 51 Draft - C Here is my testimony for tomorrow's meeting. I plan on testifying from Kona Nancy E. Burns, P.E., LLC ~ 73-1487 Hao Street ' ~a u Kailua Kona, Hawaii 96740 Tel. (808) 325-3182 Fax (808) 325-1065 nebyellc ,hawaii.rr.com comm. ~ . ~ ~ ~o' Rif. To: ~r°~ I~ltl l ~ 1 Ref. Uate MA_,_R 20 ~U~ Honorable Peter Hoffman, Chairperson Hawaii County Council 25 Waupun St. klilo, HawaiT'i 9b720 Testimonv on Bi1151 1Jl2AFT 2; Progoscd Arrsendrnent to Chapter 27 of the HCC Dear Chairperson Hoffman and Members of the Hawaii County Council: 1 previously submitted testimony regarding 1311151 Draft 2 on March 1, 2007 via email af4cr aU.ending the Public Works Committee meeting on February Z1, 2007. 1 have since obtained a copy of Draft 2 and have additional concerns regarding the amendments. The storms that usually cause major damage are the longer duration high intensity rainfalls such as the 100-year, 24 hour storm. This is the design storm used by FEMA in determining special flood hazard areas shown on the Flood Insurance Rate Maps (FIRM maps). These spacial flood hazard areas are usually stream channels that will cause significant damage to life or limb if drainage infrastructure is not constructed to accommodate the flows. Thus culverts and bridges drat cross such stream channels are sized so that the road can retrain in operation if the 100-year, 24-hour storm flow occurs. Special flood hazard areas are also regulated to prevent habitable structures from being constructed in the path of stream channels in order to protect life and property. Section 27-5 states that the chapter shall apply to all areas of "special flood hazards" but it seems to me That many of tixe proposed amendments apply to areas that do not contain special flood hazard areas. Tlxe majority of the island land area is id~ntifed as Zone X (not shaded) on the Flood Insurance Rate Maps (FIRMs)_ 'Lone X (not shaded) lands are "areas of minimal flood hazard carrrespandang to areas outside of'the flue-hurtdred-year.floodplain. " Many of the proposed amcndtnents would appear to be applicable to Zone X Ituxds drat are clearly outside of the realm of Chapter 27 which applies to "special flood hazard" areas. Furthermore, FF,MA does not require the 100-year, 24-hour storm to be mitigated, it only regulates what can be constructed within areas subjected to special flood hazard areas. So it seems like the C',ouncil's proposed amendments are mixing apples and oranges. The amendments appeaz to be directed torvard mitigation of the 100-year storm for all areas of the island, not die special flood hazard areas that the subject of Chapter 27. Specifically the definition proposed for "Flood-prone area" includes any area that has previously been subjected to topsoil erosion. This would include most if not all fanny lands where crops are harvested exposing land to erosion. 1n addition, all eonstnrcfion sites are subject to erosion dining consbuction so therefore these areas would by the, proposed definition be. considered "flood-prone areas". On page 11 under "Violation" there is a requirement to obtain an elevation eertifleation or other evidence of compliance far a stricture or other development to be considered to be in compliance with Chapter 27. 'T'he proposed amendment to Section 27-20 {d){2) {page 20) requires "Stebdivisions arrd adher~ developmertds any locatleart vr, flood zone any shall comply smith: . (2) For all proposed developments ancUoz• subdivisions greater than either rivo lots or one acre, the developer undJor subdivider shall include hase,flaod elevation data with their proposal. " Does this mean filet the depth of flow across a lot must be computed even when it is in 7ozre X (mrshaded) areas which are clearly outside the "special flood hazard" areas? Is the intention to calculate the depth of sheet flow? Is an elevation certification required for all lots of all subdivisions that are greater than 21ats or one acre? Costs for performing the base flood calculations and prepazing flood elevation certifications can be substantial and could be a tinancia] burden fnr an owner of a one acre lot that wants to construct one home. 1s it really necessary to provide this information when there is no stream channel and no history of flooding? I also question whether the requirement for developments in "any location or flood zone" belongs in Chapter 2? which is meant to cover areas of special flood hazards. The original language for Secfion 27-20 (d) referred to special flood hazards (A zones). It made sense in this context to provide base flood elevations as the A zanes are stream channels and calculation of base flood elevations is necessary to assure that sttvctures are elevated above tlxe base flood elevations of the streams. It makes no sense to calculate base flood elevations if there arm nn stream channels. "I"he proposed amendment to Section 27-18 Standards for Construction item (6) (page 17) states " Within areas where the grade of the natural elevation of the ground surface prior to construction exceeds ten percent, frilling, grading, and other developmen[ which may inerecrse the likelihood of:flooding or erosion hazards shall he prohibited unless u professional civil engineer licensed in the State of Hawaii certifies that the development will not divert runoff or disturb naturul protective buffers in a manner which increases the likelihood r~fflooding or erosion in other areas. Mun-made alteration of such sloping areas will be limited to no more than twenty percent of the total land urea of any lot or proposed new subdivision. Any measures to fie implemented in order to prevent or decrease the likelihood ofrun-qff or erosion shall fie clearly shown ar described on the gz•ading> or infrastructzrre construct[on plan. " 1 have a question as to the applicability of this requirement; does it apply only to Special i'laod Hazard Areas or to all areas evherc ilic natural grade exceeds 10%. In any event, there is no justification t`or the special treatment of lands over ten pc.z°z•cent grade or limiting, the alteration of such land to 20 percent of the land area. All projects on any slope can incroase the likelihood of hooding or erosion hazards during construction prior to drywells and infiltration basins being constructed. In order to obtain final subdivision approval developments ;mrst he designed to infiltrate increases in runoff from the TO year, 1 hazer storm no matter how steep tlie grade of the land. Economic ramifications of this amendment are very great. There are many developments where all of the land area is over ten percent. The Gvay the amendment is written, only 20 acres of a 100-acre property that is entirely greater than ten percent slope cou]d be developed. I am not sure how this helps to manage special flood hazard areas. It makes it much more difficult to develop any type of housing projects including affordable housing where in order for the projects to be economically feasible, high density and use of all of the land including land over ten percent slope is required. I am also not sure what is meant by not disturbing natural protective buffers. Is this amendment restricting the removal of vegetation and thereby reducing the usable land area o:f properties? What is the definition of a natural protective buffer? What are the aesdietia ramifications of leaving "n;ztcual protective buffers"? 2 The amendment to 27-18 (e) (page 20} does not belong in Chapter 27 but would be better placed in Chapter 23. The requirement to dispose of site generated runoff is applicable to all land areas and should not be in a chapter dealing with special flood aeeas. The use of the term. "base flood event" and "one hundred-year' flood" is a little confusing when discussing runoff disposal. Base flood events are usually considered to be the 100-year, 24 hour statistical storm and the base flood events are used to calculate 104-year base flood elevations in special flood hazard zones. I am not sure how a base flood event would be applied to stone drainage calculations for subdivision which use the 10-year, 1 hour storm with the Rational Method per County standards. The reference to the 100 year storm is inconsistent and confusing. If this amendment is trying to change the County Stone Drainage Standards from the 10-year, 1 hour storm to the 100-year, 24 hoar storm it should he made clear that that is the intent. There aze significant economic and aesthetic implications to designing storm drainage systems to carry the 100-year, 24-hour stones including wider paved roadside ditches, more and larger drainage structures, and the maintenance of all this larger infrastructure. Requirements to design for the 100-year storm could pui an added strain on getting our much needed roadways designed and amstructed due to the ecmtomic constraints of the larger infrastructure: Iwould want to know if federal funding would cover the costs of the larger drainage systems as federal standards are much less. Would we as taxpayers pick up the tab for all the extra storm drainage costs on f'ederaily funded projects'? Iwould want to know if the economic benefits of installing the larger drainage infrastnteture to accommodate a storm event that happens on the average once every 100 years outweigh the cost of construction and maintenance of the larger facilities. As a tax }>ayer, I would want a cost/benefit analysis done before deciding to implement a code which treats al] areas of the island as special flood hazard areas. This will increase costs to taxpayer but will do little to mitigate the aetual flood problem. Additional costs will substantially drive up the price of the roads which arc so desperately needed and only serve to make housing even less affordable. Regarding the County of l tawaii's current Chapter 27 regulations, it should be noted that they are already stricter than the FEMA requirements in that FEMA allows fill within certain floodplains provided there is minirrtai rise in base flood elevation. The County allows no rise in the base flood elevation. It should also be noted. that all property on the island is exposed to some degree of potential flooding during major storm events. Some property is subject to more intense flow than others due to the existence of stzearrt charnels and large tributary watersheds. At is the large scream channels and low lying areas with large tributary watersheds that are the subject of Chapter 27, not all properties. There is no way to stop the rain and no way to prevent it from crossing from one property to the next on its downhill journey to the ocean. It is the landowner's responsibility to construct his home so that water does not enter the buildings by elevating floor slabs so that water flows around. and eat through homes. Garages that are on the downhill side of driveways should have trench drains installed to carry the water away from the garage. Swales should be constructed to carry water away from the strucume. While developers are responsible to mitigate increases in runoff generated by constntetion of impervious surfaces, they are not responsible for stopping all flow from above on its way down 3 the mountain as this is an impossible requirement. Homeowners and business owners must understand that water from upstream properties can and will flow downhill across their properties just as runoff from their properties flows downhill across their downstream neighbors' lands. Storm water runoff is going to be generated whether or not there is any upstream development. All property owners must accommodate this nmoff in a way that does not impact their homes or businesses. Property owners should be responsible for hiring design and construction professionals that aze aware of drainage conditions. Individual home and business sites should be constructed accommodate storm water runoff: In my 22 years of experience as a civil engineer, I have seen lots of homes that were flooded by sheet flow entering the lots and then going into homes due to poor grading design by builders, not due to lank of dryvvells on subdivision roads. Before enacting a law that greatly increases costs to taxpayers for construction and maintenance of infrastructure, I would investigate whether this is really going to solve flooding problems of individual homes and business. Perhaps the properties that are currently experiencing flooding problems can be redesigned by adding a trench drain, catch basin or Swale to alleviate the problems. I urge the County Council to consider this matter carefully and consult with the professional engineers in the llcpaztment of Public Works and the private sector before advancing Bill 51 in its cunent: form. Sincerely, ~tN~ Nancy E. Burns, P.E. cc Bruce McClure, Director, Department of Public Works Galen Kuba, Division }lead, Department of Public Works, Engineering Division 4